Jigging the Fuselage

by Frank Justice

Note for RV-6 builders: At this time I do not have anything for installing the tailspring. Until I do, look for it in the construction manual to find the right time and procedure.

Building the Fuselage Jig
  1. If you cannot borrow a fuselage jig, build one as shown in drawing #23.
  2. The kind of wood you use depends on where you will be doing your building. You cannot use green wood; it will warp too much. Try to get kiln-dried or well-aged wood. If your shop is subject to wide temperature and humidity swings, you should use wood that is already very straight and has only small or no knots in it. Something like expensive clear fir, aluminum, or steel is overkill for all but the worst shop conditions, although metal may be the best choice if you can do welding and have a cheap source of scrap material. Make sure all of the 2x4's used for the upright crosspieces are exactly the same width (the 3 1/2" dimension). If you cannot find decent lumber make your own 2x4's and 2x6's by laminating strips of plywood; this makes a very stable jig.
  3. You will be spending some time on the underside of the jig; this is easier done using a mechanic's creeper. In order to have room enough for this you will need to make the jig higher than the plans say by about 6 inches. To make the jig easier to level, install tee-nuts and carriage bolts into the bottoms of the legs, or at least use lag bolts (wood-threaded hex-head bolts). The 2x6 uprights at one end need to extend about 27" above the main horizontal members. Add another 2x4 crossmember 3/4" away from these uprights; nothing sits on it, it just makes a better reference point for measurements. The small upright at the rear end must be 3 1/2" wide or less if you are doing a -6; a piece of 1x3 will work just fine.
  4. Level the jig and glue the leveling bolt heads to the floor with caulking compound; it holds well enough and is easy to get up later. Brace the firewall-end uprights vertical with diagonals between them below the level of the main part of the jig. The jig can be slightly warped laterally along its length, but the centerline along its length must be an exact perpendicular from the center point between the two uprights. To get this, locate a point on the rear upright that is equidistant from the outer corners of the firewall-end uprights. Then mark the centerpoint between these same corners on the added crossmember next to them. The centerline goes between these two marks. Mark a vertical canterline on the rear upright and drill a 3/16" hole on it at the same level as the tops of the upright crosspieces. Run a string through this hole all the way to and over the center of the added crossmember at the other end. Use this to mark the centerline of the fuselage on every upright crosspiece.
  5. Drawing #23 depicts the main longeron (3/4 x 3/4 x 1/8") laying on the upright crosspieces and curving up to the firewall engine mount support brackets. Locate the positions of the firewall engine mount bolt holes on the jig uprights and drill them 9/32"; remember that the upper and lower pairs of holes are not the same distance apart (see drawing #25) and that you are mounting the firewall upside down. Drawing #23 shows how far above the level of the upright crosspieces that the 1/8" thick longeron must be at the firewall, so measure on your firewall how much higher you must go to place the bolt holes.

Bottom-Top Convention
Since you have the fuselage in the jig upside down and the drawings show it right-side up, I will use the following convention to avoid confusion: the first direction given (top, bottom, up, down, etc) will indicate the orientation of the airplane and the plans; the direction following this in parentheses is the orientation as you have it in front of you in the jig.

Alternate Sequence (Early Fitting)
Some builders advocate assembling some items far earlier than Van's construction manual does. One suggestion is to assemble the seat ribs and baggage floor ribs to the bulkheads before installing the bulkheads on the jig. I didn't have any difficulty assembling these ribs to the bulkheads after they were put in the jig, and it also allowed me to see that some of the ribs needed slight length and placement adjustments. I suspect that you would have to spend some time setting up something to hold all these pieces rigid to rivet them. Another suggestion involved assembling the control sticks early. This can only be partially completed and what can be done is easy enough to do later. The only time saver is to drill the mounts to the F-604, which you have already done. These instructions also have you make the baggage area side panels during skeleton assembly. All other internal fitting is done after turning the fuselage right-side up, where the worst you have to do is lean over the main longeron to work or in a few cases go under and up through the floorboard area since you will be leaving the forward bottom skin off until later. You have already done some items early by following the bulkhead instructions.

Riveting/Construction Sequence
The general procedure in this section is to make and drill all the components of the fuselage skeleton working from the front. Then all these parts are countersunk, cleaned, primed, and riveted together. Then the skins are shaped, drilled, dimpled, cleaned, and primed, then riveted to the skeleton. In the area between the firewall and the F-604 bulkhead there are a number of #4 rivets that hold the skins and the skeleton together. Since the skeleton would not be rigid without these rivets but clecos would interfere with skinning, you will drill the large holes during skeleton construction, drill a few smaller countersunk holes in the same areas, drive only the smaller rivets during skeleton riveting, backdrill the skins through the existing holes, and when you drive the large rivets they will hold skins and skeleton components together.

Mounting the Firewall and Rear Bulkheads
Mount the firewall on the jig with 1/4" bolts (or 3/16" if you drilled smaller holes in the firewall) run through 3/4" thick spacer blocks. Mount the rearmost bulkhead F-612 on the jig side of the small upright at the other end, using drawing #23 to get its top (bottom) side the right height above the level of the longerons. If you are doing a -6A, the flange side of F-612 goes toward the jig. Mounting should be done with a couple of machine screws through the bulkhead and upright to insure that it does not shift.

Bending and Fitting the Main Longerons
  1. Read the section in the construction manual relating to the bending of the main longerons. Make the female template as described for the curved part and the 2x4 with the slot in it for twisting. Bending the longerons is an iterative process; with each bend you make another smaller bend or twist may occur, and as you take out this out it affects the desired bend. Try to figure out what else the angle is doing as you bend it so you can compensate to some extent during the initial process. You may find that the extra bend or twist does not occur in the same way for the two longerons. You may find it easier to bend one at a time rather than both together as the construction manual describes.
  2. After you make the first bend, make sure the longeron is still straight in the other plane. This is difficult to see unless you take it out of the vise and lay it on the floor or a large flat surface. After you make the long curve, lay it on the floor again to check for twist or minor bending. The side of the angle against the floor must lay flat on the floor all the way up to the upward bend, and there should be no sideways bend at the upward bend point.
  3. Lay the longerons in position on the jig with the front ends against the engine mount support brackets and the rear ends against the rear bulkhead. If the bending was done right the longeron side should lay flat on top of all of the upright crosspieces, and at the F-604 position (the first upright crosspiece from the front) the outside edges should be about 42 1/4" apart. The construction manual shows the longerons at an angle to the crosspieces but that does not apply to the RV-6.
  4. Clamp the longerons securely to the jig at the crosspiece for the F-604 bulkhead (the next one back from the one we added) and twist and bend them until they lay flat against the engine mount support bracket arms with little or no pressure applied. Clamp the longerons to one of the engine mount support bracket arms.
  5. Mark points on the crossmembers for the F-604 and F-605 bulkheads for the approximate location of the outer edge of the longerons; it is 21 1/8" (21.125) for the F-604 and 21 1/4" for the F-605. Set the longerons on these marks and clamp the rear ends to the rear bulkhead, modifying its flange angle as necessary. Mark the longerons for cutting even with the web of the rear bulkhead (webs for the RV-6; you can let the side part of the angle go to the rear edge of the flange of the bulkhead but the other side must be trimmed back to the web so the vertical stabilizer can be installed).
  6. Mark the locations of all the bulkheads on the longerons using drawing #22 for the numbers and measure from the forward edge of the crosspiece we added. Note that for the F-604 bulkhead the number to use is above the fuselage on the drawing, not below it; this bulkhead is not exactly perpendicular to the longeron line.
  7. Clamp the longeron at the F-604 station so that the outer edges are 21 1/8" (21.125, obtained from drawing #23 if you look long enough) from the center of the jig at the marks just made on the longeron. The clamp does not need to be quite like that shown in SK-49 of the construction manual since the longeron lays flat at every jig crossmember in the RV-6, but you get the idea. The clamp at this station needs to be no more than about 1" wide so it will not interfere with the channel that gets attached to the longeron later. Hold the F-604 bulkhead up to the jig to see where the clamp has to sit to avoid interference.
  8. Clamp the longerons very securely to the engine mount support brackets right at the firewall as shown in drawing #31, checking to make sure that there are no gaps. Due to variations in the manufacture of the engine mount support brackets, their fit to the longerons may not be very good. If there is a problem with not enough edge clearance for rivets, maintain the proper edge clearance in the longeron rather than in the engine mount support bracket; the steel bracket will tolerate a smaller edge distance than the aluminum longeron. Bend and trim the engine mount support bracket arms as necessary to make them lie flat along the longeron. Be careful not to bow the longeron by forcing it to fit misaligned bracket arms.
  9. Drill #30 the engine mount support brackets to the longerons from the bracket side if your drilling technique is not good (drilling through aluminum into steel can cause the holes in the aluminum to get elongated if you aren't careful), working rearward from the clamps. Clamp the F-695 gusset in place (drawing #31) and drill it through the engine mount supports and the longeron; don't bother drilling it to the firewall angles at this time. Mark the side holes in the longerons for countersinking. Remove the F-695 gusset and drill two smaller holes #40 in each area where you have #30 holes; mark all of them for countersinking. These holes are for rivets that will hold the skeleton together until the bigger rivets can be driven together with the skins and gussets.

Mounting F-604 Bulkhead
  1. Refer to detail A of drawing #31 and section A-A' of drawing #32 for the F-604 to longeron attachment. Remember that you are upside down. Modify the bend angles of the flanges of the F-604F short channels as required (necessary because the longeron is not perpendicular to the bulkhead at that point). Round off the corners so they won't dig into the inside corner of the longerons. Drill #40 to the longeron. Leave only one cleco in each F 604F.
  2. Stand the F-604 bulkhead assembly on the longerons and F-604F's; the F 604 side piece outside surface is even with the outside edge of the longeron. Measure from the center of the crossmember of the jig up to the center of the F-604 as shown in drawing #22 and #23; if is is greater than 25.16", trim the F-604 side pieces as required. Drill #30 the bulkhead to the F-604F's. Enlarge the longeron to F-604F holes to #30. Mark all these for countersinking.
  3. Clamp some strips of wood or aluminum from the firewall to the F-604 to hold the bottom (top) of it at the proper position (29 1/2" from firewall stainless steel to forward surface of main part of F-604, from drawing #22 or #23).

Firewall to F-604 Longerons
  1. Measure and cut the 1 x 1 1/4 x 0.125 (1/8)" longeron sections that go between the the firewall engine mount supports and the F-604 bulkhead; note that this longeron ends at the forward edge of the F-604 side piece and attaches to a gusset only.
  2. Clamp the F-655 gussets (in bag F-676) in place to the bottom (top) of the F-604 bulkhead as shown in drawing #31 section A-A' so as to support the longeron bottom (top) surfaces even with the bottom (top) edges of the F 604 bulkhead side pieces. If you have a more recent RV-6A kit you will not have these gussets; use a piece of scrap instead. Note that section A-A' is an inside view. Lay the longeron on the gusset and engine mount support bracket; modify the support bracket as necessary to match the lay of the longeron.
  3. Clamp the longerons securely to the engine mount support brackets next to the firewall. Twist the longerons until they will lay properly against the gussets on F-604 without being forced. Clamp the longerons to the gussets and drill the longeron sides #30 as shown in drawing #31 to the engine mount support brackets. These holes should be as close to the corner of the bracket and longeron as possible to insure that the forward bottom skin will overlap them enough when it is drilled. Mark these holes for countersinking. Drill the bolt holes on the bottom (top) 3/16" or #12 as shown in detail E
  4. RV-6 (tailwheel) only: trim and round the edges of the F-655 gussets as required for good fit and drill them #30 to the longeron and F-604 as shown in drawing #31 section A-A'. Mark the holes on the longeron but not the F-604 for countersinking. Drill two holes #40 in the each of the same areas (will be used for rivets to hold the skeleton together during skinning) and mark all for countersinking.
  5. RV-6A (nosegear) only: Mark the position of the web of the F-602 bulkhead on the longerons. Remove the F-655 gussets (or temporary gussets you made from scrap) and clamp the F-6101 gussets in place to the bottom (top) of the F-604 bulkhead as shown in drawing #59. Note that this is an inside view. Adjust the position of the F-6101 gussets so that their forward curved edges are vertical to mate with the F-602 bulkheads when they are put in later; trim the (top) edge to match the slope of the bottom (top) longeron. Then trim the gusset edge at the F-604 bulkhead if necessary so that it lines up and the forward edge is where the F-602 bulkhead web will be. Drill the gussets #30 to the longerons and the F-604 sides, but do not drill for rivets in the two areas where the gear leg supports will be put in later. Hold these supports up to the fuselage to find out exactly where it bolts on. Also, mark the longeron lower (upper) edge for trimming to clear the gear leg mounting tube. Mark all of the longeron holes but none of the F-604 holes for countersinking. Drill several holes #40 for rivets to hold the gusset to the longeron and F-604 during skeleton riveting; mark all these holes for countersinking.

Alternate Method for Drilling RV-6A Gear Leg Mounts
The main landing gear mounts on the RV-6A are bolted to the main spar rather than the engine mount as in the RV-6. The construction manual calls for doing this after the whole fuselage skeleton is done since the wings must be put in place temporarily. I will describe a procedure later which uses short, wooden imitation wings instead for those people who have limited space. While this procedure worked well for me some other builders were concerned about their ability to drill the landing gear mounting bolt holes accurately through the wooden spar. As a result one of the builders came up with an alternate procedure to perform at this point which while it requires the use of the real wings you don't have to fight installing them in the fuselage. I have reviewed this procedure and feel that there are no hidden traps, and the author has actually performed it. This procedure is found in a separate file called GEARLEG.DOC.

F-602 Bulkhead Mounting
  1. Mount the F-602 bulkhead pieces to the longerons. Bend the tab over at the top (bottom) longerons and drill #30; one hole is adequate and space is limited. For the RV-6 only, see drawing #31 detail F and use a piece of angle at the bottom (top) longeron. On an RV-6A the angle is not used as the F-602 attaches only to the F-6101 gusset. There will be a gap between the F-602 outer flange and the F-6101 gusset face; fill this gap with a spacer strip made out of scrap or the F-655 gusset, then drill #30 the F 602 to the F-6101 and spacer as shown in drawing #59. Drill two more holes #40 in the same area for rivets to hold the skeleton together during skinning. Mark the spacer for countersinking and the F-602 for dimples. Remove the F-602's.
  2. Notch and bend the F-684 gussets (from plastic bag 654P) to fit on the outside of the firewall stiffener and inside the lower (upper) engine mount support bracket as shown in detail E of drawing 31, which is looking from the inside. The gusset should overlap the engine mount support bracket arm by at least 1/2" for proper rivet edge distance. This gusset does not overlap the heavy bottom longeron, only the smaller one that goes back at an angle. Drill the gussets #30 to the firewall side stiffener only.
  3. For the RV-6 only, clamp the F-654 gussets (in bag F-676) in place on the F-604 bulkhead.
  4. Cut the diagonal longerons that go between the F-604 bulkhead at the F 654 gusset (RV-6) or the top (bottom) edge of the F-6101 gusset (RV-6A) and the engine mount support bracket/F-684 gusset combination and trim to fit. Trim the gussets as necessary to allow these longerons to fit properly. Drill #30 the longerons to the gussets and engine mount support brackets and the F-654 gussets (RV-6 only) to the bulkhead. Mark the longeron holes (but not the F-604 bulkhead holes) for countersinking. Drill holes #40 as appropriate for skeleton-only support and mark for countersinking.
  5. Put the F-602 bulkheads back in place and notch them to clear the longerons that you just put on. Remove the longerons and bow them slightly so that their outer edges will line up naturally with the outer flanges of the F-602's. Remove the F-602's.
  6. Cut, trim, and mount the longerons that go 9" below (above) the main longerons. Section C-C' shows how you use a little piece of angle to hold it out at the firewall end so that its edge will be even with the skin line. Section H-H' shows how you cut a slot and double-bend the other end so that the tip goes behind the bulkhead but the rest of the angle lies even with the skin line. These are also shown in photos in the construction manual on page P(8-8). Mark the holes in the F-604 for countersinking.
  7. Put the F-602's back in place and notch them for these longerons. Bow the longerons as necessary to make them line up with the bulkhead flanges.
  8. Make the four floor stiffeners and drill them to the firewall, but don't leave them in. On the two outer stiffeners which require a spacer to bring the stiffener up to the floor skin level, drill one hole vertical (through the spacer) and two horizontal; this makes it easier later to hold them in place for drilling to the floor.

Rudder/Brake Pedal Mounting
  1. The following only applies to newer kits having the overhead-mounted rudder pedals; earlier kit owners will have to fend for themselves. Refer to drawing 43a.
  2. Drill the F-6116 and F-6115 blocks 13/64" (this will result in a hole 3/16" in the plastic; the hole shrinks) for their mounting bolts; use great care to insure that the holes are perpendicular to the block surface. Saw the F-6115 block in half as shown.
  3. Smooth the WD-655 tube ends so they won't chew up the blocks in flight and slide the F-6116 plastic blocks onto their ends. To assemble them properly, hold up the two WD-655's so the WD-655B brake cylinder mounts (the small tabs near the main tube) are toward you. Then hold one in front of the other (pedals down) so that the one with the left pedals is closer to you. This is the way the pilot will see them in the airplane. Then slip the blocks on so their ends closer to you are farther apart (so they will follow the angle of the longeron they mount on.
  4. Clamp this assembly in place (upside down, of course) onto the top (bottom) side of the longerons.
  5. Trim the flange of the F-6118 bracket as required to clear the flange of the firewall stiffener (and the firewall cutout box if you are going to have one. Clamp it in place on the firewall stiffener so that it is the right distance from the tubes for the F-6115 block clamped to the bracket to just touch them. Drill the bracket to the firewall.
  6. Since the seats in the RV's are not fully adjustable some pilots have found it better to change the position of the rudder pedal mounts. Use the location shown in the drawing (4" from the firewall) for pilots in the range of 5'4" to 6'1" tall. If at all possible you should sit in a finished RV which has been constructed this way and decide for yourself whether you want a different location. You can move the mounts rearward by as much as 2" if all the prospective pilots are somewhat short (5' 4" or less). You can move them forward as much as one inch for taller pilots. Some builders also find it more comfortable to raise the blocks as much as one inch or to put pieces of heater hose on the rudder pedal. This affects the angle of your foot at rest (not applying the brakes). All of these changes can be made later if necessary, so don't make a big deal of it now.
  7. Drill the F-6116 and F-6115 blocks to the longerons and F-6118 bracket. If you are using the standard position and there is a chance you may want to move the pedal mounts rearward later, do not trim the rear of the F 6118 bracket at this time. It may be necessary to trim an end of one or both of the tubes so the F-6116 blocks do not overhang the outer edge of the longeron. Remove the rudder/brake pedal assembly and the F-6118 bracket.

Mounting F-605 Bulkhead
  1. The outer edges of the longeron at F-605 must be 21 1/4" from the jig centerline at the marks made on the longeron for it (from the dimensions of the F-605). Drive small nails into the crosspiece corresponding to the outer edges of the longerons to keep them from shifting.
  2. Place the F-605 bulkhead on the longerons and mark and cut the tops to fit the angle of the longerons. Put the F-657 gussets in place between the longerons and the F-605 and mark and cut them to fit the longeron angle. See drawing #32 for tip-up canopy or SC-3 for for sliding canopy.
  3. Adjust the positions of the small nails if necessary so that the outer edges of the longerons line up with the flanges of the side pieces of the bulkhead. Attach a couple of small wooden uprights to the crosspiece for clamping the F-605 to the jig; you will need to shim them a little bit forward if you have followed the jig plans dimensions to this point.
  4. Drill #30 the F-605 to the gusset and longeron in the pattern shown for the appropriate gusset. If you are doing a tip-up canopy, see the photo of the installed cabin frame on page 8-9 of the construction manual to see where you cannot put rivets. If you are doing the sliding canopy, it does not have the cabin frame, but the right side of drawings SC-1 and SC-2 shows where C-677 will bolt to the longeron later and no rivet holes should be drilled there. At this point you really only need to drill enough holes to allow the longeron to be held to the bulkhead; the rest can be drilled easily enough later. Mark the longeron holes for countersinking.

Seat Rib Attach
  1. Prepare the seat ribs F-615 through F-619: straighten by fluting the curved edge, then make all of the flanges perpendicular to the rib web. Enlarge the lightening hole opening in the F-618 and F-619 ribs as shown in drawing #29 if the ones in your kit are not already made that way. If your ribs already have the cutout, you may need to cut it out even more at the top; use the drawing as a template. Notch the rear end of the left F 619 rib so it will not close up the elevator trim cable hole in the F-605.
  2. Modify both of the F-619 ribs as shown in detail F-F' of drawing #33; the purpose of this is to make the upper part of the ribs removable so that you can remove and install the WD-610 control rod assembly later (see drawing #40). You could possibly get by with doing only one of the ribs as drawing #33 indicates, but it is better to do both. The kit at present does not include any material specifically for the splice plate; use what you can find, and it does not have to be .063 thick. The placement of the cut and the splice plate is not critical at all. Make and attach the splice plate first, then remove it and cut the rib so the rib shape will not be inadvertantly altered. The two big notches in the forward rib flanges are to clear the wing attach bolts.
  3. The F-617 ribs must be modified by cutting off the forward 4" of the top flanges. Some builders also rivet on new flanges on the other side of it. This is done because the control stick has to move almost all the way to the rib web for full aileron deflection. There is a photo of the control stick installation in the construction manual which shows this.
  4. Use drawing #33 to position the forward edge of these ribs and center the rearward flanges on the rivet holes in F-605. Trim and shape the forward ends of the outer ribs F-615 so that they will fit properly inside of the side of the bulkhead. Clamp them in place such that the distance between the two bulkheads matches the distance between the main spar and the rear spar on your wings. Drill them to the rear bulkhead, then drill two or three places #40 to the sides of the forward bulkhead (if holes are already there use those) and mark them for countersinking.
  5. Attach the rest of the ribs, adjusting the length by modifying the end flanges if necessary to keep the F-605 straight. Clamp the rearward end first and then the forward end; do not force the F-604 to twist by making it conform exactly to the forward edge of the ribs. At the rear end drill through the existing hole and make two more #30; some of these holes will later be drilled through the baggage rib flanges also, so verify that edge distance will be maintained in the flanges of both. At the forward end note where the wing spar bolt holes are and if necessary mark the ribs for notching so that you will be able to get a wrench on the nuts for the wing attach; you can also move the rib locations (except the inner two) up to 1/4". Drill #40 the end flanges for all except the center two ribs (which are screwed, not riveted on) to the bulkhead as shown in drawing #31. Also drill one hole #40 through each bulkhead flange into the all the ribs. Mark these holes for countersinking except the two at the center ribs on the top (bottom) side. Drill the holes #19 or 11/64" for the three screws that attach each of the center ribs F-619 to the bulkhead. Mark the six holes on the forward side of the F-604 bulkhead at the center rib attachment for nutplates.
  6. If you put a conduit in your wings behind the main spar, mark its location on the F-615 rib to cut out later.

Armrest F-620
Make the curved edge flanges of the F-620 armrests perpendicular to the web, then flute that edge to make the armrest straight. Attach the armrest F-620 between the bulkheads as shown in drawing #32. The forward end is attached with a single rivet through the skin edge flange only as shown in drawing #31 section H-H'. The rear end attaches using a piece of angle underneath it. The forward end should be about 1/16" short of touching the inward-pointing flanges of the bulkhead so there will be room to slip the F-604E channel onto the bulkhead later on as shown in drawing #31.

Mounting F-606 Bulkhead and BaggageCompartment Ribs
  1. Clamp the F-606 bulkhead to the jig at the proper distance from the firewall. Insure that the longeron outer edges are even with the outside edges of the bulkhead flanges and the correct distance from the centerline (18.02 inches per drawing #24). Insure that the bulkhead top and bottom are the correct distance from the plane of the top (bottom) of the longeron as shown in drawing #22. You will find it helpful but not essential to clamp some wood strips to the bulkhead to keep it from being so floppy.
  2. Kit Problem Note-Read this whole paragraph and try to understand all of it before deciding how you want to proceed:
  3. There are some problems with the baggage floor ribs F-625 thru F627 which have not been fixed as of this date. The F-626 and F-627 ribs are about 1/8" to 1/4" too long. The flanges at the ends may need to be tweaked slightly to keep them from trying to twist the bulkheads. The F 625 ribs are too wide to fit properly if placed as the plans show. Until this is fixed, Van's recommends the following fixes. Carefully rebend the flanges on the ends of the F-626 and F-627 ribs as required to get the bottom (top) of the F-606 bulkhead the proper distance from the firewall (the bulkhead should be vertical) and also to get proper angle at the ends. Move the F-625 ribs more toward the centerline to the point where their width matches the distance between the F-605 flanges and between the F 606 bottom flange and the baggage floor support angle. Then fix its length if necessary. The important thing is that the bottom skin not have a jog at the bulkheads and the baggage floor is reasonably flat (you will probably put a rug on it anyway). If you choose, you can save some time by not altering the end flanges of the ribs. The result will be that the F-606 bulkhead bottom will have a little twist and a little curve; also, the bulkhead itself will be appear to be a little too high when it comes time to align all of the rear bulkheads. None of this is particularly serious, and not really noticeable unless you are looking for it. You can still get the skins to line up by slightly tilting the F-607 and F-608 bulkheads.
  4. Drill the baggage floor ribs #30 to the F-605 and F-606 bulkheads, starting in the center. Remember that the bottom (top) flange actually extends past the F-606 flange by one skin thickness (0.025"). Notch the F 627L flange to clear the large hole in F-606 and F-605 and if necessary the flange of F-627R to clear the rivets that will later hold the F-628 rib to the bulkhead.
  5. Attach the F-623 ribs to the F-605 and F-606 using a lap attach at the forward end as shown in section H-H' in drawing #32 and a butt attach at the rear as shown in I-I'. You could use a butt attach at the forward end to avoid the slight jog in the skin there but it is not worth the trouble for the average builder. The rib is usually too short to do a lap attach at both ends. Note that a J-stringer will be attached later at the rear end using the same rivet. Mark the rivet holes for countersinking or dimpling as appropriate.

Seat Belt Anchors
  1. Drill one hole #12 or 3/16" about in the middle of the foot on each of the eight F-634 seat belt anchors as shown in drawing #33. I have had one report that this will make the bolt holes in the bulkhead too close to the upper edge of the bar for the two inboard anchor pairs, so compare what you have with Section K-K' of the drawing before drilling. Otherwise, try to drill each anchor in the same location so they will be interchangeable later.
  2. Hold the seat belt anchors in position on the F-605 bar using drawing #33. Leave 1/8" between the seatbelt anchor pieces. Make sure that none of the anchors will hit any seat rib webs or run up on the bend of the short bars and you will be able to get wrenches on the bolt heads and nuts (the lateral placement of the anchors is not critical). Mark and drill the F605 #12 or 3/16" for the bolt holes for the seat belt anchors.

F-622 and F-624 Side Ribs
  1. Prepare the ends of the F-624 ribs as shown in drawing 32; use the R6 pictoral. Note that these ribs are attached to the longeron and the F-623 ribs only by a bent-over end tab. The outside edge flanges are cut off at the ends so the rest of the flange will be even with the outside edge of the longeron and F-623. The outside edge flange points rearward. Loacate the ribs as shown in the drawing, except move them forward if the rear edge of the outside flange goes past the notch in F-623. Drill #40 the rib attach holes and mark the ones in the F-623 ribs for countersinking. Mark the exact location of the rib webs on the longerons and F-623's. Mark the location of the 5/8" hole in line with the similar holes in the F-605 and F 606 bulkheads. Remove the ribs. Mark the rivet holes for countersinking or dimpling as appropriate.
  2. Drill #40 the F-622 ribs to the bulkheads as shown in drawing #32. Note that the outside edge flange points upward (downward) and that the rear end must be positioned so that a J-channel will overlap it later. Cut a slot halfway through the F-622's from the outside where the web of the F 624's will intersect them. Cut away the outside flange of the F-622's to leave a place for the F-624 flanges to be flush with the skin lines. Mark the exact location of the rib webs on the bulkheads. Remove the F-622 ribs.
  3. Reattach the F-624 ribs. Cut a slot halfway through them from the inside edge where the F-622 rib webs will intersect them. Do not cut away any extra flange except tp clear the inside radius of F-622. Join the ribs and attach all to the fuselage. Drill #40 the inside flanges together at the intersection. Mark the holes for dimpling on the inside. Make sure the ribs do not touch each other at the crossing other than where they will be riveted or vibration may cause them to wear or break.
  4. Drill #40 the longeron to the bulkhead flanges.

Step (Option)
  1. If you are expecting short-legged people to fly with you it is a good idea to get the optional step from Van's. You can get either side or both. This is the best time to install the steps, although you can do it just as easily any time up until you put on the bottom skins in that area. You can even do it after that but it is somewhat more awkward to work where you need to.
  2. F-649 and F-650 Baggage Compartment Sides
  3. Drawing #37 shows the attachment of the baggage compartment sides, but is a little difficult to figure out because it does not show the dashed lines that indicate the edges of the F-622 side rib.
  4. Put the F-649 side panel in with the large flange resting on the top (bottom) of the F-622 side rib and the forward edge against the outside of the inside flange of the F-605 bulkhead. Trim the forward edge if necessary to make it conform better to the bulkhead. Trim the flange to allow the rear edge to lay against the F-624 vertical side rib. Bend the rear edge so it will lay flat against the flange of the F-624.
  5. Insure that the holes in F-622 and F-624 at their crossover line up, then drill holes for the attachment screws #30. Do not drill baggage floor attach holes. Mark the forward edge and the bottom (top) holes of the F 649 and the F-622 and F-624 ribs for platenuts.
  6. Mark the lower (upper) end of the F-649 even with the tops (bottoms) of the baggage ribs, then bend the edge down to hold the edge of the baggage floor. Cleco back in place.
  7. Modify the F-650 side panel in similar fashion. The small flange goes against the F-606 bulkhead and its angle may need to be modified so that the panel fits properly against both the bulkhead and the F-622 side rib. Drill the holes #30 that attach the top (bottom) of the panel to the F-622 rib and the forward edge to the F-624 rib. Do not drill the holes for attaching the rear flange to the F-606 bulkhead.
  8. Mark the baggage floor line on the side, remove it, bend down the baggage floor support flange, then cleco it back in place.

F-607, F-608, F-610, F-611
  1. Clamp some wood strips 1/4" thick or so to these bulkheads and also F 606 to make them less floppy. Proper alignment and later skin riveting will not be practical without this.
  2. Clamp bulkheads F-607 and F-608 to the jig at the proper distance from the firewall as shown in drawing #22 and Attach F-610 using small upright blocks attached to the jig. Verify that the longerons are equidistant from the jig centerline and that the marks you made previously on the bulkheads are even with the top (bottom) of the longerons. If you lay a long straightedge along the longeron from F-606 to F-612 you should find that it is straight or bows out no more than about 1/8" in the middle. If one or more bulkheads is pushing the longerons out of line (only likely if you were not able to use the tooling holes to align the bulkhead halves), move them backward or forward. Because the position of F-610 relative to F-612 is important for mounting the stabilizers, try to keep it as shown on the drawing.
  3. Clamp the side J-channels to F-606. Note that the ones that overlap the F 622 side ribs extend past the bulkhead by about two inches. Drill these channels #40 to the F-606 only. Cut off the ends even with the rear edge of F-612 and trim to fit against the flange of it. Modify the indentations and slots in the other bulkheads if necessary to allow the outside edge of the J-channels to fit into the indentations in the bulkhead flanges with enough overlap for proper rivet edge distance.
  4. Tie strings between the F-606 and the F-612 bulkheads at about six points as a guide, then adjust the positions of the bulkhead tops backward or forward as necessary to form a straight line across the bottoms (tops) of the bulkheads. Slight bends forward or backward in the bulkheads are not a problem, but make sure you look at the lineup on all six strings before deciding which way to move something. Otherwise you will have a lot of trouble getting it right an you may have some really wierd twists. Clamp the channels to the bulkheads.
  5. Trim and drill the bottom (top) J-channels to F-606 and cut the other ends off just past the rear edge of F-610, leaving a little extra in case you have to readjust the bulkhead position. Adjust the bulkhead positions again as required and clamp these.
  6. Kit Problem: If you place the bottom (top) J-channels based on where the slots are in the bulkheads you may not be able to attach the F-673 side skins properly. This situation was improved somewhat in kits shipped in 1994 or later as the side skin was made one inch taller at the rear. If the skin in your kit matches the dimensions on drawing #36 and the drawing has revision 9 incorporated, you should have no trouble. To make sure that you will not have a problem, find the F-678 rear bottom skin and place it on the fuselage (it goes between the F-606 and F-610 bulkheads). Position the bottom J-channels so that they come out to the edge of this skin. This may require that you enlarge the bulkhead slots a little bit. This guarantees that you will not have an edge distance problem in the side skin with the rivets that hold the F-678 and F-673 skins to the J-channel.
  7. Drill the J-channels and longerons to the bulkheads #41. You may have noticed by now that you only have one J-channel left and you know that two are required later for the top of the fuselage. Don't rush to Van's; the one you have left is long enough to make the two needed.
  8. Determine the position of the F-611 bulkhead following the drawing numbers as close as possible; notch the main longerons there to clear the bars on F-611 and the J-channels to clear the flanges. Clamp the bulkhead in place to the longerons and J-channels; drill it #40 to both.
  9. Mark all the J-channel - bulkhead holes for dimpling and the longeron holes for countersinking.
  10. Put in the F-629 rib between F-606 and F-607; modify its rear flange if necessary to make it the proper length. Drill holes to attach it to the F 607.
  11. Cut a piece of 3/4 x 3/4 x 0.125 (1/8)" angle to join the F-611 bulkhead to the main longerons as shown in drawing #34. Clamp firmly to the bulkhead, remove the bulkhead, and drill the angle through the holes in the bars on the bulkhead.
  12. Cut a piece of 1 x 1 x 0.125 (1/8)" angle to join the F-610 bulkhead to the main longerons as shown in drawing #34. Drill the angle for the rivet holes as shown in section D-D', then mount it on the bulkhead and drill that.
  13. On the RV-6 mount the Wd-609 tailspring bracket to the rear bulkheads as shown in drawing #34.

Skeleton Assembly and Riveting
  1. Disassemble everything a piece at a time starting from the rear and do the following required items (if you take it apart all at once it may be difficult to determine things like where nutplates go, what holes to drill out, etc) . You can leave the bulkheads clamped to the jig although you may want to remove F-604 to attach nutplates to it.
  2. Dimple or countersink all the marked holes.
  3. Drill the 5/8" holes in the F-624 side ribs.
  4. There are some places in the fuselage where the plans call for attaching K1000 nutplates to material that is thinner than 0.032" (too thin to countersink). In these situations just dimple the thin material and also dimple the mounting ears on the nutplates. They take a dimple quite easily.
  5. Drill and countersink or dimple the rivet holes for all the nutplates and drill out the screw holes to 3/16". The F-649 baggage side holes all get drilled for screws; on the F-650 drill out only the forward edge holes (along the edge that is not bent into a flange).
  6. Prime everything.
  7. Install all nutplates.
  8. Rivet the center rudder pedal brace to the firewall. If you have a box for the firewall rivet it on using Pro-Seal or epoxy to seal the seams.
  9. Start assembling and riveting as you go, starting at the firewall. Think about the order in which to do this so you don't put something in the way of a later riveting task. In the area between the firewall and the F-604 bulkhead most of the holes you have drilled are intended to be riveted with the skins so you will just drive rivets in smaller holes you made in the same area. Do not rivet on the F-695 gusset at the top (bottom) of the firewall now; it is much easier to do after the fuselage is out of the jig. Drive all of the rivets holding the F-684 gussets to the firewall sidebrace (but not the engine mount support brackets) since skin rivets will not go through these holes. See drawing #36. You can also permanently install the bolts that hold the bottom (top) longerons to the engine mount support brackets; this is adequate to hold this area so no rivets are required. You may want to put rivets in the #30 holes right next to the firewall as these may be hard to get to after the skins are put on. If you feel the need to put any rivets in the area where the main gear support goes on the RV-6A you can do this by countersinking both sides of the hole and driving the rivets flush with both sides. You should check to be sure you can drive the rivets that hold the next-to-outboard seat ribs to the F-604 bulkhead before you rivet the front side piece to the rest of that bulkhead; if not do these before riveting the front section pieces. Rivet on the two short angles that attach the two outer floorboard stiffeners to the firewall, but do not rivet on the stiffeners themselves.
  10. Remember that some of the baggage ribs and seat ribs get riveted at the same time. Install the bolts that hold the outer baggage ribs to the F-605 bulkhead. Bolt on the seat belt anchors. Cleco in the baggage compartment side panels. Rivet the F-629 rib to the F-606 bulkhead only at those holes below (above) the baggage floor support angle. Do not rivet the baggage floor support angle to the F-606 bulkhead. Put rivets in all the countersunk holes in the F-604 flanges to attach the seat ribs, but do not put rivets in the two holes on the bottom (top) side at the center ribs (these rib sections are removable).
  11. Rivet the angles to the F-610 and F-611 bulkheads.
  12. When you get the front half riveted, clamp the longerons securely to the jig at all points, attach the rear bulkheads and J-channels, recheck the skin lines for straightness, and then rivet the J-channels and main longerons to the bulkheads.
  13. Bend bulkhead and rib flanges as necessary to make them conform to the skin lines.
  14. Remove the baggage floor support angle from the F-606 bulkhead.

Drilling the Skins
  1. The most efficient way I have found to drill the skins to the fuselage skeleton (thanks to Gil Alexander and some others on the Internet) is to drill pilot holes in the skeleton using a #50 or 1/16" bit, put the skin in place, drill the skin through the pilot holes from the inside using a 6" or 12" long drill bit of about the same size, and then drill all of the holes from the outside full-sized. The pilot holes are drilled all along the curve of the bulkheads and also at intersections of the straight parts. The latter holes are used as reference points to locate and drill the rest of the holes that fall in straight lines. The small drill is used because some of the pilot holes cannot be drilled straight from inside the fuselage and the skin or bulkheads will shift slightly as you do the final drilling. Don't drill all of the pilot holes at once; wait until you see where a particular skin goes first, drill the pilot holes for it, then mount it for drilling. It is not necessary to drill pilot holes in the main longerons since you can see the location of the bulkheads.
  2. Using this method you will find it easy to locate all holes properly. You will find that the bulkhead flanges and J-channels wander much more readily during drilling than you are used to, however. This requires that you tape the flanges and J-channels securely to the skin before drilling the long runs between pilot holes and at the corners of the bulkheads.

F-679 Rear Bottom Skin
  1. Reshape the bends of the F679 rear bottom skin as necessary to make it fit properly to the ribs when it overhangs the rear bulkhead web by about 1". It will be trimmed here later. The skin needs to be tweaked well enough that it requires no more than light finger pressure to make it conform to the skeleton.The forward edge does not have to be trimmed. Bend the flanges of the bulkheads so that they lay flat against the skin, especially in the bulkhead corners.
  2. Drill pilot holes. Tape the skin down to the skeleton and backdrill through the holes with the small drill. Drill holes #41 (or #40; this skin can be countersunk safely, especially if you are doing a -6A which has less stress in this area) only in the two rear bulkheads. Those along the longerons and on the forward bulkhead are not drilled yet because other skins will go on top. Remove the skin, clean out the chips, deburr the holes on the mating surfaces, and put the skin back on.

F-678 Aft Bottom Skin
Drill pilot holes. Put the F-678 aft bottom skin in place and tape it down to the skeleton. Backdrill the pilot holes. Mark the remaining holes between the reference holes except the ones along the longerons and the forward bulkhead (skins will go on top later). Drill all the holes #41. Remove the skin, clean out the chips, deburr the holes on the mating surfaces only, and put the skin back on.

F-673 Rear Side Skins
  1. Remove the F-679 rear bottom skin. Clamp a rear side skin F-673 to the main longeron with one edge sitting on the jig cross-pieces and the rear overhanging the rear bulkhead web by about 1". The forward edge should just cover the F-606 bulkhead flange. Mark the inside of the skin for trimming such that it will overlap the rear bottom skin enough for a proper lap joint, using the rear side of the F-610 bulkhead and bottom (top) side of the J-channel as a marking guide. An approximation of this cutout is shown in drawing #36. Revision 9 of this drawing indicates the change to make the skin taller here to eliminate the problem mentioned previously.
  2. Take the skin off and trim it using your marks as a guide. Make sure you won't wind up with an edge too close to one of the holes you have already drilled in the rear bulkheads. Most builders leave just enough material so that the edge will be fairly close to the line of rivets that go into the longeron and the bulkhead, but they make the inside corner a fairly large radius rather than a sharp corner. Another way might be to trim off very little which makes the skin edge be near the bottom rather than on the side, but this will require an extra line of rivets to hold the skin to the rear bottom skin.
  3. Try forcing the side skin down against the bottom skin using the strap clamps from the wing kit or similar. It is best to do this with both side skins in place. If you cannot get it down well enough and you are afraid clecos will not hold it later or the skeleton will be distorted, modify the curve of the side skin so it more closely matches that of the fuselage. This should be done accurately enough so that tape will easily hold the skin fully against the bulkhead corners. This may be fairly difficult depending on when your kit parts were made; it takes a lot of force toward the rear of the skin, and if you are not very careful you will crease it. The best way short of setting up some elaborate fixture seems to be to place the skin flat on a floor or table with the curved-up edge toward you and the other edge against a wall; tape a broomstick or 1 x 2 near the top of the curved part and push on it. The direction you push (down or toward the wall) will determine whether the skin bend increases more in the middle of the curve or next to the flat part.
  4. Drill the pilot holes, but don't put any in the main longeron. Cleco the F 679 rear bottom skin back onto the skeleton, tape the edge down where you will be adding the side skin, then remove the clecos on that side that will interfere with the side skin. Clamp the side skin to the main longeron. Verify that there will not be an edge distance problem where the skin meets the aft bottom skin. Verify that they are straight and tape the J channels and bulkhead flanges to the inside of the skin.
  5. Starting in the center of the skin and working outward drill #40 with 3" spacing along the main longeron between the forward end and back as far as where F-610 will go later; do the rest to the rear at normal spacing. Drill #41 upward and outward from the center with normal spacing along the bulkheads and J-channels, backdrilling each pilot hole with the small drill only as you need it to locate the next line of rivets as you progress. Do not drill any holes holes along the forward edge at the F-606 bulkhead, not even the pilot holes.
  6. Remove the skin. The other skin can be drilled without the first one in place if you have carefully shaped the skins to fit without forcing them.
  7. Make the elevator pushrod access hole and cover for it as shown in drawing #46. You can do this in just one side but it is preferable to have an opening at least large enough on the opposite side to get a socket into. The opening needs to be as large as you can make it for easier access. Note that round-head screws hold the cover on because they take less room (no dimples required). The opening size you can get by using a reinforcing ring to hold the cover on as shown in the drawing is adequate, but it is possible to make it a little larger if you joggle the skin around the opening to form flanges for holding the cover. This method is also slightly faster but you need to have the tools to do it with. You can probably make a round hole and cover quicker than a rectangular one, and it will still be large enough. With the left (right) side skin in place mark the outlines of the main and center longerons and the two rearmost bulkheads on the inside of it. Remove the skin and use these marks as a guide to make the skin opening; be sure to leave enough to joggle or attach a reinforcing ring to (at least 3/8"). Cut the opening, then make the cover to fit the opening. To make a reinforcing ring, mark the outlines of the longerons and bulkheads on some 0.032 or thicker material, cut it out, put it on the skin lined up with the corresponding marks, drill the cover and ring for the screw holes and the ring and skin for the skin to ring rivets. Cut the opening in the reinforcing ring. Mount the platenuts, rivet on the reinforcing ring. The hole on the opposite side only needs to be about 3/4" in diameter, and it is best to wait until you have mounted the elevators so you know exactly where to put it.
  8. Deburr the skins and skeleton. Retrim if necessary to avoid having rivets too close to an edge. Round the edges that will go on the outside of the bottom skins and bow them inward slightly so they will not leave a gap when riveted.
  9. The photograph section of the construction manual indicates that you can rivet on the rear skins now. There is no particular advantage in doing it as clecoes will hold the rear skins quite well for now. If you do, you will have to drill the holes at the forward end of the side and bottom skins now, then dimple them with the rest, but don't rivet them. You will later have to backdrill the forward side skins and center section bottom skins through these holes and this will be a little awkward.

F-676 and F-677 Center Bottom Skins
  1. Place the F-677 skin (the wider one) with its rear edge past the F-606 flange by 1" and its inside edge overlapping the proper baggage and seat ribs. See drawing #36. It goes two inches past the fuselage centerline. Secure it only at F-605. Locate the centerline of the F-605 flange visually or with pilot holes. Mark the locations of the webs of the baggage ribs along that line, then mark the rivet holes to avoid these.
  2. Drill a few holes in the center of this line and then start drilling along the ribs in a diamond-shaped pattern out toward the edges. Drill the double row at the rear edge (see section A-A' of drawing #36) and the outboard seat rib, but not the forward edge, the inside edge, or the outside funny baggage compartment rib (F-623). Use the small pilot drill to find the rib flanges; the skin may shift as much as 1/16" at the front and rear edges as you drill and cleco. You must also tape the rib flanges to the skin and make sure the seat ribs are straight. While you are at it , drill the pilot holes in the curved part of the F-606 bulkhead on through the aft side skins.
  3. Tape down the inside edge of the skin, then place the other skin to overlap it by 3/4". Drill this skin the same way, and drill the skins together where they meet in the middle as the last step.
  4. Mark the skins for trimming along the sides in the area of the baggage compartment, and leave all of it in the area between the wing spars as shown in drawing #36. This part will later attach to the wing skin. Remove the skins and trim them slightly inboard of the marks or as necessary so they will not dig into the side skins as they are pulled around to the bottom later.

F-672 Forward Bottom Skin
  1. Put in the main spar substitute spacers at F-604 and run several bolts through them and the front and rear halves of the bulkhead to force the front half into the proper position.
  2. Cleco the floorboard stiffener angles to the firewall. Because you have cut them to the final length already per these directions you cannot make a temporary attachment as shown in SK-52; this will be handled differently. On the inside of the bottom skin mark the postions of the stiffeners near the rear edge using drawing #31.
  3. Place the forward bottom skin with its forward edge extends past the firewall web by at least 5/8" and is even with or past the edge of the flange everywhere. This skin may not fit very well and modifying it will be difficult. It may appear that the F-604 bulkhead is crooked but it is more likely that the bottom skin is formed incorrectly. Compare diagonal measurements on the skin and between the firewall and the F-604 to determine what adjustments need to be made. Rather than trying to modify the bends in the skin consider using shims between it and the skeleton as well as rotating the skin so that the sides line up with the skeleton even though the front does not. Attempting to pull the sides of the skin in to attach to the longerons instead will result in a bulge in the side skins at the bottom of the fuselage.
  4. Verify that the rear edge of the forward bottom skin overhangs the flange of the F-604 bulkhead by at least 5/16" so that there will be enough room for the row of rivets that go only through the skins and not the flange also. Clamp and tape the skin in place and drill it at the rear edge, starting with the row of rivets that goes through the F-604 bulkhead flange (see section B-B' for rivet location). Then make pilot holes for marking the forward end to the firewall stiffeners; at the same time drill a #40 pilot hole at the rear end of each floorboard stiffener and put in a cleco to hold it to the skin. Mark and drill the skin to the firewall stiffeners; it is suggested that this row of rivets be 1/8" where possible rather than 3/32" as called for in the plans for extra strength. The first two holes in the floorboard stiffeners should also be 1/8". Then drill the skin to the floorboard stiffeners.
  5. See drawing #31 for the application of the cowling attach hinge sections to the firewall. Cut the two sections of 13 1/2" heavy hinge for the firewall bottom out of the long piece supplied. Do not cut the hinge pin. Also cut two sections of spacer out of the proper width material supplied. Tape the spacer in place with riveting tape to make it easier to place the spacer and hinge for drilling. You will probably not be able to locate the hinge eye at the exact dimension shown on the drawing; just locate it so that the center of the eye is beyond the skin edge by 1/16". The piece of hinge with the eyes at the ends should be used on the firewall. Drill the hinge and spacer to the bottom skin and firewall flange, and drill the remainder of the skin to firewall flange holes between the hinges.

F-670 Side Skins
  1. Set a side skin on the fuselage with the forward end lined up with the firewall side flange and resting on the jig. Mark the edge of the bottom skin extension on it and trim out the material about 1/8" more than the mark indicates. Put the skin back and mark the rear spar connector on it; trim this out about 1/8" oversize. Put the skin back and check to see that it is not being blocked by the jig uprights from completely covering the forward firewall flages; trim if necessary.
  2. Put the skin back in place butted against the jig uprights and secure it to the skeleton with clamps and tape. Mark on the side skin those areas where rivet size and spacing are unusual to prevent mistakes, such as the main longeron, the F-604 bulkhead, and the area near and covered by the wing. The note on the drawing concerning use of AN470 AD4 rivets in the area covered by the wing root is a suggested time-saver; since the overhang of the bottom skin may be in the way when you rivet these, the universal-head rivets may be easier for you to drive than flush head rivets.
  3. Drill the side skin starting in the middle and working outward. Use pilot holes liberally to avoid drilling too close to skeleton members and to get in the middle of flanges and angles. Be sure you don't drill from the outside in those areas near the firewall where holes already exist in the skeleton. Note that there will be top skins put on later in certain areas. Drawing #36 shows these clearly for the tip-up canopy; the top skin runs from the firewall to just aft of the little F-602 bulkheads and from the forward edge of the F-605 bulkhead toward the rear. For the sliding canopy see drawings SC-2 and SC-4 which show the forward top skin going from the firewall back to a point about 3" aft of the F-604 bulkhead and the aft top skin starting a little forward of the F-624 side stiffener and going on back. Treat the main longeron in these areas just like you did in the rear part with 3/32" rivets on 3" centers.
Note: In the area between F-605 and F-606 where the side and bottom skins meet at the F-623 rib the side skin is curved over and slid under the bottom skin in the rear half but in the forward half which is a sharp corner most people just cut both skins at the corner which leaves a thin line through which you can see the rib. This part is covered by the flap when the flap is up. If this gap annoys you, you can trim the side skin about 1" past the corner, bend it down into a flange that will fit under the bottom skin, trim this flange to where it is about 5/8" wide, and then notch it in about four places so the skin will follow the slight curve in the F-623 rib. This actually shims up the bottom skin in this area closer to the level of the F-605 bulkhead, thus avoiding a jog in the skin surface. At the trailing edge the drawings show that the skin is trimmed some in the curved area and then riveted together with the aft side skin to the bulkhead. This is a little difficult as the forward side skin comes in at an angle to the aft side skin; you must bend a flange outward on the rear side skin and pull the bulkhead flanges outward also for proper riveting.
  1. Pull the side skin against the forward half of the F-623 rib and mark it for trimming either level with the bottom skin or past it by 1" as described above. Trim the skin only in this area, not in the area aft of it where the curved part will be. Work the aft end down by hand into a curve that will approximately fit the curve of the aft side skin. Mark a reference line on the curved part of the aft side skin where the web of the F-606 bulkhead lies, then carefully trim out the trailing edge of the side skin until it matches this line when you pull it down. Note that the rest of the forward side skin is left so that it overlaps the rear side skin enough to allow a second row of rivets. Trim off the excess side skin, leaving about 3/4" to go under the bottom skin.
  2. Notch the rear side skin at the same places where the F-606 bulkhead flange is notched and bend both flanges out to match the angle of the forward side skin. Drill the rest of the side skin to the skeleton.
  3. Mark the openings for the main spar, the seat rib lightening/aileron control rod hole, the fuel tank pickup fitting, and the wiring conduit if used. Mark along the edges of the longerons between the firewall and the F-604 bulkhead.
  4. Remove the side skin and put it in place on the opposite side of the fuselage, noting where it does not fit. Lay this skin on the other one and mark and trim the second one using the first as a guide. Drill and shape the second skin
  5. Cut out the marked openings about 1/8" oversize and trim along the longeron lines. For the RV-6A cut an opening in the large gusset in the landing grear area corresponding to the tank fitting access hole in the skin.

Riveting the Fuselage Skins
  1. Remove all of the skins, deburr, dimple, clean, and prime them. The heavy rear bottom skin can be countersunk, although if you are doing a taildragger dimpling will make this area stronger. The forward bottom skin can be countersunk for the floor stiffeners and cowling support hinge, but should be dimpled for the row of rivets that go into the firewall stiffener angles and the row that goes into the flange of F-604 for extra strength. Countersink or dimple all of the holes you have put into the skeleton except the ones where you are countersinking the skins; remember that some rivets near the main spar are universal (round) head and don't get a dimple.
  2. All of the skins except the forward bottom skin can now be put in place one at a time and riveted; backrivet the stiffeners to it on the bench and set it aside. For the RV-6A the two bottom skins in the seat and baggage area are also not riveted for now to make it easier to mount the landing gear leg supports. Rivet in the same order that you drilled holes to avoid problems with holes not lining up well at the edges of curved skins. You may find it handy to not rivet on the aft bottom skin until you have riveted most of the rear bottom and aft side skins if you are working alone; you can then slide the aft bottom skin under the side skins and get help with riveting this. You may have considerable difficulty driving rivets in the curved areas at the bulkheads; if so, try using flush-head pop rivets left over from your wing kit. Do not put rivets in any of the holes that are used by the forward bottom skin. Do not rivet the forward side skins to the firewall.

RV-6A Main Landing Gear Legs
  1. If you are doing a -6A which has the landing gear mounts bolted to the wing spars drill the landing gear as described below and in the manual and drawing #59.
  2. The normal method of lining up the -6A landing gear mounts for drilling is to attach both wings to the fuselage and drill the mounts through them. This requires either a lot of room in your workshop or moving the whole thing out in the driveway for a day or two. It also requires that you have the help of four to six people during part of that time to get the wings on and off. It is important that the holes in the landing gear get drilled accurately so you don't have to enlarge any later to get the wing bolts in. There will be a lot of stress in this area and you don't want the gear mounts working and chewing up the bolts. This is why you should make every possible effort to use the wings as the drill guides. It is not necessary that you have the fuselage in the jig for this; you can just put it on some sawhorses as long as you get it perfectly level from side to side. Having to later enlarge a few holes to get the bolts in is not cause for panic however; note that while there are a number of bolts holding the gear mount to the fuselage, there is only one bolt holding the leg to the mount. Also, there are two larger bolts in the mount at the point of greatest shear stress for which the holes will be drilled undersized and not enlarged until the wing is finally mounted on the fuselage.
  3. If you do not have room to put the wings in place for this or you don't have a bunch of people to help, make imitation wings out of wood the same thickness as the spars (just under 1 1/4" thick), 7 3/4" wide, and about 41" long. Laminating together a piece of 3/4" and a piece of 1/2" or two pieces of 5/8" CDX plywood work well for this since they are actually slightly under nominal thickness; at most you will just have to shim a little bit with some skin scraps. Clamp them in place in with the lower (top) edge carefully aligned with the lower (top) edge of the F-604 bulkhead. Verify that the fuselage is still level across the bottom (top) of the F-604 bulkhead, then verify that the dihedral angle of both imitation spars is the same. A smart level (digital readout) is very handy for this but a mechanical angle indicator will work as well (a square device with a hanging pointer and degrees marked on it in a circle around the pointer). Mark as many of the 3/16" holes as you can by drilling just a little bit through the holes in the F-604 bulkhead. Mark the rest with a transfer punch. Drill them all in a drill press; these holes must be very accurately located and precisely perpendicular or the gear leg holes will not line up later when you install the wing.
  4. With either the wings or the imitation wings in place, clamp the landing gear mounts in place, put the gear legs in them, and line them up as shown in the manual and drawing #59. In more recent kits the hole for the bolt that goes through the gear mount and the leg is already drilled. This reduces greatly the complexity of alignment necessary; all you need to do here is to put the bolt in the hole for each leg, clamp a stiff something across the ends of the legs, and move the gear mounts until the stiff something is level and the dimensions shown on the lower left corner of drawing #59 are met.
  5. The only really reliable way to drill the gear leg mounts accurately is by drilling a pilot hole first using a piece of metal tubing as a bushing and hole protector, then drilling the hole full-sized as shown in the construction manual. The mount is too oddly-shaped to drill in a drill press, so even drilling the pilot hole and then removing the mount for final drilling is accurate enough only if you are extremely careful to hold the drill exactly perpendicular to the mount surface. Using a transfer punch, removing the mount, and drilling a pilot hole with a 1/8" bullet-nose drill is the only other reasonable alternative. If you need a transfer punch and can't find one, buy a drive pin punch with a round or six-sided handle, chuck it in a drill press, and file the tip to a shallow point. It is difficult to drill the mount freehand without the bit wandering even with a pilot hole, so a reamer or drilling with a sequence of slightly larger drill bits should be used. You will find it difficult if not impossible to drill all of the holes in the gear leg mounts as shown in the manual with a regular drill bit; the seat ribs are in the way. Obtain 12" long 1/8" and 3/16" drill bits for this. The long drill bits should be available in any reasonably good hardware store and are worth the money to get you really good results. Then remove the mounts and ream the holes out with a #12 bit.
  6. Note that two of the bolt holes of the four in the outboard lower area are larger. At this time drill and leave them as 3/16". They will be drilled out to the proper size later after the wings a actually installed to insure a tight fit.
  7. Drill the side mounting holes; note that they are larger than the spar mounting holes. Do not bother with countersinking the forward side holes at this time. You will probably note that the forward side pad on the mount does not come right to the inside of the big gusset like it should; make some shims to match the pad to the gusset and glue them in place before drilling those holes.
  8. Make cardboard templates to locate the holes in the bottom skin for the gear leg mounts; cleco it to a few rivet holes along the F-604 bulkhead flange, cut the right size hole, then cleco it to the skin to mark the hole. The hole does not have to fit the mount tightly; it will be covered by the leg fairing. Cut the holes in the skins.
  9. Remove the gear legs. Rivet on the seat and baggage area bottom skins. Leave the forward bottom skin off.

fusejig.doc 2/11/96 Frank Justice

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