Europa-List Digest Archive

Mon 01/24/11


Total Messages Posted: 6



Today's Message Index:
----------------------
 
     1. 03:54 AM - Re: Re: Main wing bushings (Peter Zutrauen)
     2. 04:38 AM - Re: Re: Main wing bushings (G-IANI)
     3. 11:17 AM - Re: Re: Main wing bushings (Fred Klein)
     4. 02:02 PM - Re: Re: Main wing bushings (Duncan & Ami)
     5. 03:12 PM - Re: Re: Main wing bushings (Bud Yerly)
     6. 03:23 PM - Re: Re: Main wing bushings (GRAHAM SINGLETON)
 
 
 


Message 1


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    Time: 03:54:27 AM PST US
    From: Peter Zutrauen <peterz@zutrasoft.com>
    Subject: Re: Main wing bushings
    Hi Bud, All valid points - and thanks for the detailed calcs and drwgs. After more head scratching, I can only come to the conclusion that the Fuse (especially the wrt the front pins) flexes relative to the main spar pins, allowing for the main spar pins to begin carrying the loads. So, if one was to actually *strengthen* and thus stiffen the area around the front pins, the loads on these pins could actually be *increased* and result in failure s (?) - since as you have pointed out, the margins of those front pins do not appear to be excessive. Quite the mind-bender - at least for me. Further thought also makes me envision the fuse itself flexing under g-loading in the front-back direction (with that heavy chunk of metal up front and that long tail out back), which also transfer the loads to the main spar pins from the lift pins. So I heartily agree with your view that *all* the pins are required, and al l share the dynamic loads in a complex relative fashion, due to all that fiberglass flexing going on (both the wings and the fuse). Cheers, Pete On Mon, Jan 24, 2011 at 12:11 AM, Bud Yerly <budyerly@msn.com> wrote: > =EF=BB > Photo E-mail Play slideshow<http://photos.msn.com/Viewing/Album.aspx ?PST=8nK2AN1B%211LEiKSdooxx9v4CFFiF2tnPWP2mfc7Vl*sFUj2%21vUzirO5TouaOzaO* BEOC0mA51%21eASMb0hNQHNQ%24%24>| Download > images > <http://photos.msn.com/viewing/Photos.aspx?pi_Type=SlideshowTask&Task =Download&stppData=&pi_ImagesOnly=1&Folder=nBuRgwTGIGjZPMtNhxCyPhYL UBR*bYP2KBLX6a88C1s%24&User=23IQaj7Z2BRqNO1wUECSpX*P0Ju9hSGI&pi_NoLogin =1> > Pete, > I really enjoyed our discussions, as you and Graham have excellent insigh t > and the Lord knows I need a break from wiring. > > Just as you and others found it interesting that the side pins on the > fuselage were designed to take all the load in lift and moments, I ran so me > basic calcs one Sun n Fun and it hit me why. > If you consider the wing sockets only it is a determinant structure and > easy to calculate. > > When the Europa was only 1300 lbs, like my Classic, I figured quick and > dirty the following: > The GW is 1300 less wing weight is 1200, times ultimate of 6 Gs gives 720 0 > lbs load and 3600 pounds load born by the pins on each side. > > Figure one below shows the balance beam idea. Of course we have to add > pitching moment and the drag component doesn't go exactly through the pin s > and the dimensions were rough as shown in figure two. Considering 304 > stainless pins are good for about 15Ksi in shear and at 1/2 inch diameter > they can take a load of roughly 3000 lbs. The front pin holds about 2700 > pounds and the rear pin about 900. So it was a slam dunk why it was > calculated that way. > > My instructors in college had a saying which was "the spar takes the lift > and the root takes the moments" and that is something we, and I am sure the > PFA, all remember. So the Europa design calculations indicate the main s par > only translates the wing bending and the wing spar pins carry no lift loa d > in the calculations. But who would buy an aircraft where the wing pins a re > not attached to anything but the spar themselves. After all if the wing > sockets at the root carried all the load, we would only have an inspectio n > plate in the fuselage back and we would rig the wings to the spar cup and > side sockets only, then stick the other wing in, pin it and go fly. What do > we need all that extra ply, aluminum and bushings for in the cockpit > bulkhead? That is a lot of beef for just the spar bending loads and late ral > shifting to be checked. That is unless it is redundant structure? > > Further, if we increase the loading of the plane to 1450 lbs and then tak e > the gust loading into consideration as well as temperature, the actual > loading jumps up by a huge factor. We only had a reserve on that front p in > of a few hundred pounds, now that pin/socket is going to be compromised. > > If we consider the wing is supported at the main pins as a fulcrum say, w e > have the sum of forces and the sum of moments but three unknowns and we h ave > an in-determinant structure as in figure three. If you assume the wing p in > takes all the load as a see saw, then the spar bushes only have the momen t > load which is much less. Add in the point you made about the spar bendin g > actually unloads the load its all gravy. So it seems without extensive > strain gauge testing you can't get the design approved on the statement > "well the pin is really not overstressed". We can't calculate the forces > actually born by the pins unless we assume (ass out of u and me) some > loadings. > > It is my feeling that the main wing pin does in fact take some of the lif t > load, greatly relieving that front pin. Any assigned loading on the > bulkhead wing spar pins would significantly relieve the front socket. I > believe this is born out by the fact that so many aircraft are flying wel l > over gross weight and have flown uneventfully with no signs of stress on the > forward pin and socket. Looking at the forward and rear socket, we also > note that if a careless builder did not get the clearances as per the > manual, bending on the pin would compromise the rib attachment as the gla ss > could not stand the peel forces from the pin threads and disaster would > ensue. A loss of any one pin would be catastrophic. If the front pin wa s > removed, the rear pin may be able to take the load, but the root rib shea r > web may not be quite strong enough and the main spar cannot take any > twisting so structural integrity will be lost. So to recap, the root rib , > socket attaches, and pins are all critical. > > > Anyway, that is all I was commenting on. I'll leave the gross weight > increase to Dave Goddard as he is a whole lot smarter than me. Other > drawings and comments are provided below the three figures. > > Regards to all, > Good night, > > Bud > > <http://photos.msn.com/Viewing/Album.aspx?PST=8nK2AN1B%211LEiKSdooxx9 v4CFFiF2tnPWP2mfc7Vl*sFUj2%21vUzirO5TouaOzaO*BEOC0mA51%21eASMb0hNQHNQ%24%24 > > <http://photos.msn.com/Viewing/Album.aspx?PST=8nK2AN1B%211LEiKSdoox x9v4CFFiF2tnPWP2mfc7Vl*sFUj2%21vUzirO5TouaOzaO*BEOC0mA51%21d384Ff4KCjNQ%24% 24> > > > ----- Original Message ----- > *From:* Pete <peterz@zutrasoft.com> > *To:* Bud Yerly <budyerly@msn.com> > *Cc:* GRAHAM SINGLETON <grahamsingleton@btinternet.com> > *Sent:* Saturday, January 22, 2011 7:08 PM > *Subject:* Re: Europa-List: Re: Main wing bushings > > hi Bud, > > thx very much for taking the time for your clarifications and drawings et c. > i agree with strenthening the front lift pin fwiw. > > the point i was making was that although the main spar pins ideally > *should* take a considerable portion of > the g-loads, in the current implementation i believe they are not when th e > wings and spars are flexing > under g-loading. for paper illustration purposes only, imagine the main > spar pins being free floating wrt > the cockpit module. also assume for illustration purposes only, that the > wing spars ar glued together, > and the shear/twisting is negligible. now draw a straight line between th e > two lift pins. measure the vertical > distance between this line and the spar pins. now add g's to the wings, a nd > the bend thoughout the spar > increases- thus this distance measurement increases, in a downward > direction relative to the lift pins. > so the result is that when the spar pins are captured securely in the > cockpit module, they are exerting > a downward pressure on the cockpit module bushes (!). > > surely not what we want from the design, but what i believe we have in > reality. so when the wings and spars > are flexing under load, all the g loading is carried by the lift pins, a nd > the spar pin bushings are > actually *adding* downward load to the load carrying lift pins :-( > > all that said, i would never mess or compromise the design, and only > strengthen areas after very careful > anaylsis, to avoid simply moving failure points to other areas of the > structure...which why i'm happy to hear > that there may be a forward lift pin strengthening mod. > > cheers& thanks again, > pete > a239 > > > On Jan 22, 2011, at 5:44 PM, "Bud Yerly" <budyerly@msn.com> wrote: > > =EF=BB <photosHeaderCamera.jpg><photosHeaderLogo.jpg> Photo E-mail Play > slideshow<http://photos.msn.com/Viewing/Album.aspx?PST=8nK2AN1B%211LEiK Sdooxx9v4CFFiF2tnPWP2mfc7Vl*sS5AKZ1XFu9bdFiq9nGbamu2smUkPeKxoqgpH5Zhql1A%24 %24>| Download > images > <http://photos.msn.com/viewing/Photos.aspx?pi_Type=SlideshowTask&Task =Download&stppData=&pi_ImagesOnly=1&Folder=nBuRgwTGIGjZPMtNhxCyPhYL UBR*bYP2xqPRoK3DBCQ%24&User=23IQaj7Z2BRqNO1wUECSpX*P0Ju9hSGI&pi_NoLogin =1> > AH semantics, or I just don't understand the question. Fatigue is > setting in... > > I failed to note your discussion was also including the root pins, which > are absolutely carrying a share of the load and cannot be discounted. > The system needs all the pins, and it is rather scary to note that > elimination, compromise or failure of any one pin leads to catastrophic > failure of the wing... > This is why the LAA is so concerned about the glider wing and the wing ro ot > pins. I'm afraid that the shear forces have always been of concern on th e > aft pin, but in fact is also a problem on the forward pin as well. The > fuselage pins do contribute to the lift forces, but also are the alignmen t > devices to hold the wing in place so the root pins stay engaged. It has to > otherwise we would not have a plywood reinforced and metal and glass > interface structure holding the bulkhead mounted bushings, we would have put > an access hole in the fuselage for the pins only and just a bolt to hold the > root secure to the fuselage... It is an integral system. > > Granted, my traditional schooling always implied *the spar takes the lif t > and the root takes the moments and drag forces*. *One would only have to > consider the spars glued together and the fuselage attached to the spar a t > only the two spar pins to see the point.* Each spar pin would be carryin g > half the fuselage weight or more accurately, the spar pins must take the > full load of the fuselage weight component with loadings. The spar (glue d > together) will just be a rigid structure and the fuselage would hang from > the pins, and I say it can normally, however, the Europa seems to count o n > both side pins as well to translate the root forces and assure structural > integrity. > > The two side pins at the wing root do allow the root forces to lift a > component of the weight of the fuselage or as much as the root rib will > translate, it is true, but the sum of the forces and moments on the root > pins is significantly augmented by the wing fuselage pins. A significant > amount of the load, in my opinion has to be carried by the pins in the > cockpit, as you know there is considerable moments working on the fuselag e > bulkhead. Of course the moments imparted by the wing cannot be born by j ust > this internal fuselage structure and pin arrangement the shear web on the > side of the fuselage contributes to the strength of the aircraft. The pi n > sockets on the side of fuselage or root pins take all the torque of the l ift > moment and the moment between the lift vector and the main spar as well a s > the root rib imparted lift and drag forces. If only the side pins were > supporting the entire load, the spar bending loads on the root rib (which > unfortunately allows flexing of the glass, as well as the attach points), > would in practice fail in bending of the socket or pin so the load cannot be > 100% on the root pins. This is quite prevalent in the motor glider. The > root rib cannot lift all of it alone nor is it strong enough if the forwa rd > pin or socket is compromised. We are now facing the LAA wanting a much > stronger attach point on the fuselage for the forward root pins. The sid es > of the fuselage are not strong enough really for my taste and I believe t hey > are probably correct in wanting a much larger fitting on the forward pin and > socket to take some of the load from the rear pin. > The sum of the forces then about the starboard cockpit pin indicates huge > shearing forces on the internal pins, as I alluded to, which keeps the pi ns > in check. (See my quick and dirty drawing.) > If the pin bush is imparting an upward force on the fuselage, in steady > flight, the downward force implies that the fuselage has a weight (plus > manuever loading) to the fuselage wing pins also. Hence my term, hanging > from the pins. Of course, the side pin forces must be included and are > considerable as the vector drawings show. > > If the side attach pin points were so strong, why don't we have a trolley > for the mono with pins to lift the plane for servicing. Or, why not buil d a > wooden beam through the fuselage to hold the plane alone through the pins , > probably. Would it hold in either case, you bet, but any slop and you ar e > going to bend something badly. In reality betting the whole design limit > loading on the plane on just either is not possible as glass and fittings > bend under load. It is an integral structure. > > Anyway, that is how I understand it... > Bud > <74.jpg><http://photos.msn.com/Viewing/Album.aspx?PST=8nK2AN1B%211LEi KSdooxx9v4CFFiF2tnPWP2mfc7Vl*sS5AKZ1XFu9bdFiq9nGbamu2smUkPeKxoqgpH5Zhql1A%2 4%24> > > > ----- Original Message ----- > *From:* GRAHAM SINGLETON <grahamsingleton@btinternet.com> > *To:* Peter Zutrauen <peterz@zutrasoft.com> > *Cc:* Bud Yerly <budyerly@msn.com> > *Sent:* Friday, January 21, 2011 7:39 AM > *Subject:* Re: Europa-List: Re: Main wing bushings > > Pete > that's how I understand it > Graham > > ------------------------------ > *From:* Peter Zutrauen < <peterz@zutrasoft.com>peterz@zutrasoft.com> > *To:* <grahamsingleton@btinternet.com>grahamsingleton@btinternet.com; > <budyerly@msn.com>budyerly@msn.com > *Sent:* Friday, 21 January, 2011 11:41:12 > *Subject:* Re: Europa-List: Re: Main wing bushings > > Hi Bud, > > (this email sent to just you and Graham to avoid further confusing the > issue.) > > My original mental analysis was just has you have described - but Graham' s > description contradicted the assumption that under positive high-G loads, > the main spar pins are indeed providing an upward force vector to the > cockpit module as originally (and intuitively) thought. > > The reason being that both the forward and rear (your rear pin under > tension analysis is accurate tho) lift pins are indeed taking *all* of th e > downward G-loading from the cockpit module, and the two spar pins are > actually pushing *downward* on the cockpit module (disregarding the twist ing > vector on the main spar pins imparted by the scissor action of the spars) . > Why? because the spars are actually bending in curve (think a smile) just at > the entire wing is, and the root ends of the spars are actually (relative to > the fuse) higher as a result than the spar pin positions. The spar is try ing > to impart it's smile shape onto the vertical cockpit module surface - whi ch > is not going to comply. > > I believe this analysis (Graham's) is correct. So the fuse is not > hanging on the spar pins during high-G loading as one would intuitively > assume. > > Cheers, > Pete > > On Thu, Jan 20, 2011 at 10:26 PM, Bud Yerly < <budyerly@msn.com> > budyerly@msn.com> wrote: > >> Sorry guys if I don't understand the actual question about the bushes >> and bearing loads! I had to go back and try to picture the question, in the >> mean time, Grahams analysis is spot on as usual. >> >> To visualize the loads read on to my miscellaneous drivel. >> >> The two spars are basically a set of scissors.. The pins lock the spars >> together like a pair of scissors trying to cut a steel bar. The pins of >> course must go through the fuselage and each spar to hold the fuselage >> gravity forces and translate the lift forces of the wings to the fuselag e. >> The bushes distribute the load and the hardened pins take the lifting >> loads as shear load. >> >> Essentially the fuselage (about 1100 lbs. loaded with down tail forces >> added under G and acceleration as well as the radial Gs) hangs from the >> pins. >> >> The spars bend under the vertical load. Like a pair of scissors, that i s >> trying to cut through that solid steel bar stock, so picture the force o f >> your hands causing the thin blades to bend, as you would expect a thin long >> pair of scissors to twist, bending vertical and laterally. >> Mod 52s rear socket and tube takes the forward element of the lift vecto r >> (the lift of the wing near maximum is forward and up, really pulling on the >> aft socket) and translates the load through root rib, to the rear attach to >> the steel tube in fuselage which is under tension but does not >> significantly contribute to the vertical lift load. >> >> Because the aircraft is fiberglass and it does move a bit under load, th e >> spars twist some under load. The Mod 52s, 1/2 inch spar pip pin, keeps the >> tip of the starboard spar in check and from slipping into the control >> linkage under bending and twisting. The spar strap deters twist and spa r >> separation under load from their at rest positions. The pins hardened >> strength allows it to not be sheared by the huge shearing action of the two >> spars against the fuselage and each other. >> >> So why doesn't the spar pin bend at the bush? Picture the fuselage >> weight is pulling down at the left cockpit bush, the left spar (forward) is >> pulling up, but the right spar (aft) is pushing down, and the sum of the >> actions basically keeps the pin horizontal. All that force though is on >> only one 1/2 inch in diameter pin, and that is one heck of a lot of >> shearing force. Because it is over a short distance (and our spars are t ight >> together), we don't have to have microns of tolerance in the pin to bush ing >> fit.....The action of the spars against one another brilliantly keeps th e >> pin horizontal and not from bending upward at the fuselage bush and slip ping >> off the pins as one would expect at first glance thinking of only one sp ar. >> >> It is a clean neat simple design. Could it be better, you bet, but can it >> be built by us simple beings easily and cost effective? Probably not, s o do >> I want to change it? No way, it isn't worth it. Like you all say, it a in't >> broke, so don't fix it. >> >> For you new builders, keep your bushes and spars at a reasonable tightne ss >> and you will be fine. If you must ream the bush a bit because the port pin >> is too tight, you only need to ream a couple of thousandths normally. A >> heated pin through the bushes works best, as Graham said before, to take a >> slightly out of align bush and right it. Don't panic at the fuselage bu sh >> slop as the spars keep the pin horizontal. Always use the spar strap an d >> the pip pin adjusted as per the manual with the washer to distribute the >> load on the poor spar cup. Don't substitute bolts for the wing pins >> provided unless properly hardened. If you own a classic, do a Mod 52/74 as >> it is great insurance. >> >> Regards to all and I hope to see you at Sun "n Fun. >> >> Bud Yerly >> Custom Flight Creations, Inc. >> <http://www.customflightcreations.com/>www.customflightcreations.com >> (813) 653-4989 >> >> >> >> >> >> >> >> >> ----- Original Message ----- >> *From:* Bob Harrison <ptag.dev@tiscali.co.uk> >> *To:* <europa-list@matronics.com>europa-list@matronics.com >> *Sent:* Thursday, January 20, 2011 6:38 AM >> *Subject:* RE: Europa-List: Re: Main wing bushings >> >> Hi! I understand that the late Barry Mellors did all the fuselage calcs . >> IMHO he was a brilliant engineer in all things aircraft and worked in hi s >> own self employed right doing lots of work for the Brazillian aircraft >> manufacturers Combine him with Don Dykins wing designer and you had the >> benefit of a wonderful combine. Unfortunately we obviously can=99t speak to >> Barry anymore to discuss the items you are interested in. However it may >> help you to understand that when the wing fails it fails forward. Like h as >> been suggested =9Cif it ain=99t broke don=99t try to f ix it !=9D Barry, bless him, >> helped immensely with the engine mount design and PFA approval for the >> Jabiru 3300 engine mount and I=99m quite sure the aircraft would n ever have >> flown without his design skill and approach to the intransigence of the PFA >> engineer of the time! >> >> Regards >> >> To all >> >> Bob Harrison G-PTAG >> >> >> >> *From:* <owner-europa-list-server@matronics.com> >> owner-europa-list-server@matronics.com [mailto:<owner-europa-list-server @matronics.com> >> owner-europa-list-server@matronics.com] *On Behalf Of *Kingsley Hurst >> *Sent:* 20 January 2011 03:33 >> *To:* <europa-list@matronics.com>europa-list@matronics.com >> *Subject:* Re: Europa-List: Re: Main wing bushings >> >> >> >> Hello Will, >> >> >> >> I am not suggesting there is any alternative for us as builders. The >> design "as is" obviously fits the bill so the old adage, "if it ain't br oke, >> don't fix it" is appropriate. >> >> >> >> From a designer's point of view however, if you inspect the various >> methods employed by sailplane manufacturers, there are possibly better w ays >> of doing it. I have never seen a sailplane with the same set-up as the >> Europa but that doesn't mean there isn't any. Ivan Shaw did get some id eas >> from sailplanes so maybe he found one . . . . I dunno! >> >> >> >> Cheers >> >> Kingsley >> >> >> >> do not archive >> >> >> >> ----- Original Message ----- >> >> *From:* William Daniell <wdaniell@etb.net.co> >> >> *To:* <europa-list@matronics.com>europa-list@matronics.com >> >> *Sent:* Wednesday, January 19, 2011 9:57 PM >> >> *Subject:* Re: Europa-List: Re: Main wing bushings >> >> >> >> Kingsley >> I don't understand due to my limited knowledge of the engineering. >> What alternative might there be? >> Will >> >> * * >> >> * * >> >> ** >> >> ** >> >> ** >> >> ** >> >> ** >> >> * <http://www.matronics.com/Navigator?Europa-List>http://www.matronics.c om/Navigator?Europa-List* >> >> ** >> >> ** >> >> * <http://forums.matronics.com/>http://forums.matronics.com* >> >> ** >> >> ** >> >> ** >> >> ** >> >> * <http://www.matronics.com/contribution>http://www.matronics.com/contri bution* >> >> ** >> >> * * >> >> * >> >> href=" <http://www.matronics.com/Navigator?Europa-List>http://www.matr onics.com/Navigator?Europa-List"> <http://www.matronhref/>http://www.matron href=" <http://forums.matronics.com/>http://forums.matronics.com"> <http: //forums.matronics.com/>http://forums.matronics.com >> href=" <http://www.matronics.com/contribution>http://www.matronics.com /contribution"> <http://www.matronics.com/c>http://www.matronics.com/c* >> >> * >> =========== matronics.com/Navigator?Europa-List =========== =========== .com/contribution =========== >> * >> >> > This MSN Photo E-mail slideshow will be available for 30 days. > To share high quality pictures with your friends and family using MSN Pho to > E-mail, join MSN <http://g.msn.com/0PHenus1/29>. > > This MSN Photo E-mail slideshow will be available for 30 days. > To share high quality pictures with your friends and family using MSN Pho to > E-mail, join MSN <http://g.msn.com/0PHenus1/29>. >


    Message 2


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    Time: 04:38:17 AM PST US
    From: "G-IANI" <g-iani@ntlworld.com>
    Subject: Re: Main wing bushings
    In support of Bud and Pete=99s notes I can confirm that flexing of the fuselage is important. The LAA had considerable concerns that the tail dragger conversion would stiffen the structure in such a way that it could lead to overloading of the forward lift pin. Ian Rickard G-IANI XS Trigear, 300hours Europa Club Mods Specialist e-mail g-iani@ntlworld.com


    Message 3


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    Time: 11:17:22 AM PST US
    From: Fred Klein <fklein@orcasonline.com>
    Subject: Re: Main wing bushings
    On Jan 24, 2011, at 4:34 AM, G-IANI wrote: > In support of Bud and Pete=92s notes I can confirm that flexing of the > fuselage is important. The LAA had considerable concerns that the > tail dragger conversion would stiffen the structure in such a way > that it could lead to overloading of the forward lift pin. BINGO !! This is one of those times when I truly value this forum...I've been following this thread w/ only mild interest...to this non-engineer's mind, the assumed function of the lift pins was primarily to set and maintain the wings' AOA. But Ian's comment got my attention, and I have a newfound appreciation of all the posts leading up to it. =46rom the get go, I've been embedding components within my mono which would facilitate potential conversion to Bob Berube's tail dragger. I'd planned to add the recommended layups intended to transfer LG loads to the fuselage sides which have the effect of stiffening the sides of the fuselage. While I do not have the expertise to comment on the implications such layups may have on the loads ending up on the forward lift pins, I now will hold off on these layups...they can, after all, be easily added in the event the mono-ground handling proves troublesome...I may even get airborne a week earlier! Fred


    Message 4


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    Time: 02:02:35 PM PST US
    From: "Duncan & Ami" <ami-mcfadyean@talktalk.net>
    Subject: Re: Main wing bushings
    <<.. would stiffen the structure in such a way that it could lead to overloading of the forward lift pin >> Ian, How does that work, if the lift pins are designed to carry the lift loads in the first place, there being no greater load available?! Actually, it was stiffening in bending that might restrain rotation of the lift pin that was the issue, resulting in an additional bending load (not lift load) being applied to the forward lift pin. The LAA were offered a spherical socket that would articulate and remove the bending load on the pin, but declined to accept that. However, you are on right path, The earlier discussion in this thread presumes that the spar flexes, as it indeed doe. But actually the spar (loaded in this direction) is the least flexible part of the whole system. What about the forward and aft portions of the root rib? Let's say these ribs have equal section and 'I' as the spar, but being laid-up at +/- 45 degrees have x1.41 the elasticity of the unidirectional spar (in the direction of principal stress), added to which the length of these flexing root ribs (between lift pin and spar) is longer than the offset between lift pins and spar pins. So, as the root ribs will flex more than the spar and it follows that the "leverage" effect between the longitudinal offset of lift pin and spar pin centres is removed, or reversed to the extent that the spar pins share some lift load. As you say, the flexing of the fus side also contributes, albeit this had to be stiffened-up to prevent pin disengagement. Previously I have put a small finger down one of the (1/2") spar pin holes with the wings rigged, while someone else rather violently loaded the wing, albeit not even near to 1g. But there was no hint of the "leverage" effect or the spar hole flexing downwards relative to the pin hole in the seat back. Rgds., Duncan McF. -----Original Message----- From: owner-europa-list-server@matronics.com [mailto:owner-europa-list-server@matronics.com] On Behalf Of G-IANI Sent: 24 January 2011 12:34 Subject: RE: Europa-List: Re: Main wing bushings In support of Bud and Pete's notes I can confirm that flexing of the fuselage is important. The LAA had considerable concerns that the tail dragger conversion would stiffen the structure in such a way that it could lead to overloading of the forward lift pin. Ian Rickard G-IANI XS Trigear, 300hours Europa Club Mods Specialist e-mail g-iani@ntlworld.com


    Message 5


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    Time: 03:12:00 PM PST US
    From: "Bud Yerly" <budyerly@msn.com>
    Subject: Re: Main wing bushings
    This topic is a moving target, a lot like fiberglass... Most of the flex of the spars is in the thinner section reaching maximum nearing the spar socket area. The spar at the root does not move, and the forward root rib is really quite stiff, the aft root rib portion is not as high so it tends to flex a bit as stated. The fuselage side on the other hand is a bit flexi. After repairing a couple aircraft, the aircraft flexing spots tend to be the area just behind the rudder pedal step, just forward of the windscreen on hard landings (when the floor flexes), and between the front socket and the spar. Interesting thing is the Redux did not let go in any of the mishaps. Tough stuff. Those looking at conventional gear, we must do considerable work to try to get the landing gear loads closer to the fuselage sides to carry the torsional load of the cantilever gear. The cockpit module seat is not quite up to the task. To get a proper stance on the gear (read as taller in height), the moment between the wheel and the fuselage on rough surfaces is quite high, and a thin beam gear verses a wider gear beam and the actual attach mechanism has to be analyzed and tested properly. All in due time. Bud ----- Original Message ----- From: Duncan & Ami<mailto:ami-mcfadyean@talktalk.net> To: europa-list@matronics.com<mailto:europa-list@matronics.com> Sent: Monday, January 24, 2011 4:58 PM Subject: RE: Europa-List: Re: Main wing bushings <<.. would stiffen the structure in such a way that it could lead to overloading of the forward lift pin >> Ian, How does that work, if the lift pins are designed to carry the lift loads in the first place, there being no greater load available?! Actually, it was stiffening in bending that might restrain rotation of the lift pin that was the issue, resulting in an additional bending load (not lift load) being applied to the forward lift pin. The LAA were offered a spherical socket that would articulate and remove the bending load on the pin, but declined to accept that. However, you are on right path, The earlier discussion in this thread presumes that the spar flexes, as it indeed doe. But actually the spar (loaded in this direction) is the least flexible part of the whole system. What about the forward and aft portions of the root rib? Let's say these ribs have equal section and 'I' as the spar, but being laid-up at +/- 45 degrees have x1.41 the elasticity of the unidirectional spar (in the direction of principal stress), added to which the length of these flexing root ribs (between lift pin and spar) is longer than the offset between lift pins and spar pins. So, as the root ribs will flex more than the spar and it follows that the "leverage" effect between the longitudinal offset of lift pin and spar pin centres is removed, or reversed to the extent that the spar pins share some lift load. As you say, the flexing of the fus side also contributes, albeit this had to be stiffened-up to prevent pin disengagement. Previously I have put a small finger down one of the (1/2") spar pin holes with the wings rigged, while someone else rather violently loaded the wing, albeit not even near to 1g. But there was no hint of the "leverage" effect or the spar hole flexing downwards relative to the pin hole in the seat back. Rgds., Duncan McF. -----Original Message----- From: owner-europa-list-server@matronics.com [mailto:owner-europa-list-server@matronics.com] On Behalf Of G-IANI Sent: 24 January 2011 12:34 To: europa-list@matronics.com Subject: RE: Europa-List: Re: Main wing bushings In support of Bud and Pete's notes I can confirm that flexing of the fuselage is important. The LAA had considerable concerns that the tail dragger conversion would stiffen the structure in such a way that it could lead to overloading of the forward lift pin. Ian Rickard G-IANI XS Trigear, 300hours Europa Club Mods Specialist e-mail g-iani@ntlworld.com http://www.matronics.com/Navigator?Europa-Listhttp://forums.matronics.com http://www.matronics.com/contribution http://www.matronics.com/Navigator?Europa-List<http://www.matronics.com/N avigator?Europa-List> http://www.matronics.com/contribution<http://www.matronics.com/contributi on>


    Message 6


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    Time: 03:23:25 PM PST US
    From: GRAHAM SINGLETON <grahamsingleton@btinternet.com>
    Subject: Re: Main wing bushings
    Not convinced Duncan. The spar resists bending and the leverage is enormous , =0Afrom the centre of lift of the wing 30% span? The load on the root rib s is shear =0Aand some bending of the pins. Don't forget the lift load is a spread load =0Awhereas the spar bending of the tangs is a point load appli ed by the spar pins.=0AYou are right about the stiffening of the fuselage side. We really should have =0Aflexible sockets at the LE as well as the T E.=0AI still believe the lift pins (in the root rib) should carry all the l ift loads =0Aand the spar pins all the bending loads. That's why the tangs needed to be =0Astrengthened on the glider.=0A=0A=0AGraham=0A=0A=0A=0A=0A__ ______________________________=0AFrom: Duncan & Ami <ami-mcfadyean@talktalk .net>=0ATo: europa-list@matronics.com=0ASent: Monday, 24 January, 2011 21:5 8:21=0ASubject: RE: Europa-List: Re: Main wing bushings=0A=0A =0A<<..would stiffen the structure in such a way that it could lead to overloading =0Aof the forward lift pin>>=0A =0AIan,=0AHow does that work, if the lift pins a re designed to carry the lift loads in the =0Afirst place, there being no g reater load available?!=0AActually, it was stiffening in bending that might restrain rotation of the lift =0Apin that was the issue, resulting in an a dditional bending load (not lift load) =0Abeing applied to the forward lift pin. The LAA were offered a spherical socket =0Athat would articulate and remove the bending load on the pin, but declined to =0Aaccept that.=0A =0AH owever, you are on right path, The earlier discussion in this thread presum es =0Athat the spar flexes, as it indeed doe. But actually the spar (loaded in this =0Adirection) is the least flexible part of the whole system. What about the =0Aforward and aft portions of the root rib? Let=99s say t hese ribs have equal =0Asection and =98I=99 as the spar, but be ing laid-up at +/- 45 degrees have x1.41 the =0Aelasticity of the unidirect ional spar (in the direction of principal stress), =0Aadded to which the le ngth of these flexing root ribs (between lift pin and spar) =0Ais longer th an the offset between lift pins and spar pins. So, as the root ribs =0Awill flex more than the spar and it follows that the =9Cleverage=9D effect between =0Athe longitudinal offset of lift pin and spar pin centres is removed, or reversed =0Ato the extent that the spar pins share some lif t load. =0A=0A =0AAs you say, the flexing of the fus side also contributes, albeit this had to be =0Astiffened-up to prevent pin disengagement.=0A =0A Previously I have put a small finger down one of the (1/2=9D) spar pi n holes with =0Athe wings rigged, while someone else rather violently loade d the wing, albeit =0Anot even near to 1g. But there was no hint of the =9Cleverage=9D effect or the spar =0Ahole flexing downwards relati ve to the pin hole in the seat back.=0A =0ARgds.,=0ADuncan McF.=0A =0A =0A- ----Original Message-----=0AFrom: owner-europa-list-server@matronics.com =0A[mailto:owner-europa-list-server@matronics.com] On Behalf Of G-IANI=0ASe nt: 24 January 201112:34=0ATo: europa-list@matronics.com=0ASubject: RE: Eu ropa-List: Re: Main wing bushings=0A =0AIn support of Bud and Pete=99 s notes I can confirm that flexing of the fuselage is =0Aimportant. The LA A had considerable concerns that the tail dragger conversion =0Awould stiff en the structure in such a way that it could lead to overloading of =0Athe forward lift pin.=0A =0A =0AIan Rickard G-IANI XS Trigear, 300hours=0AEurop a Club Mods Specialist=0Ae-mail g-iani@ntlworld.com=0A =0A =0A =0A =0A =0Ah ttp://www.matronics.com/Navigator?Europa-List=0Ahttp://forums.matronics.com === =0A




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