Today's Message Index:
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1. 08:34 AM - Re: Flap binding issue - how to shorten the flap actuating cross (budyerly@msn.com)
2. 09:18 AM - Re: Re: Flap binding issue - how to shorten the flap actuating cross (Ron Jones)
3. 03:38 PM - Re: Flap binding issue - how to shorten the flap actuating cros (budyerly@msn.com)
Message 1
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| Subject: | Re: Flap binding issue - how to shorten the flap actuating |
cross
Jeff,
Measurement of your binding is easy.
Simply retract the flap in stages until the tube forces the flap outboard.
Continue until the flap is forced out to contact. If it is in the last few degrees
of flap travel and it is in hard contact, you will need to pull the flap
bearing out of the flap tube.
Heat will debond the Loctite 638. To protect yourself and finish:
Pull the wings.
Flaps down.
Protect the fuselage with some aluminum foil.
Put a wet rag around the flap tube about 4 inches back.
Pull out your soldering iron or a small propane torch and heat the bearing and
tube end a couple hundred degrees. Not red hot, just enough to sizzle water spray
is enough...
You can't hurt the metal parts.
Expect the paint to be damaged. (That is what touch-up paint is for.)
Use a long tapered drift or similar to insert in the bearing and begin a circular
binding motion to torque the bearing out slightly. I am fairly aggressive
about moving the drift fore, aft, and up and down. The bearing is tough, it can
take it. I use an old chisel or screw driver once the bearing starts to move
to pry it a bit as customers get squeamish about applying force on their airplane,
but it has to be done...
Once the bearing begins moving it will come out.
Use a small square to check your tube end squareness. With the bearing out you
have more room between the flap closeout and tube.
Install the wings and retract the flaps. Check for slop. This is fairly tough
for most to see, but simply make a tool out of either thin scrap metal or .041
safety wire if you don't have a small hook. Place the hook in the slot and
check in and out clearance with the flaps up. Be creative, you will be surprised
how a piece of stiff safety wire will achieve your measurement goal.
If the flaps go up and down without binding without the bearing, then measure how
much the flap moves in to hit the tube end. Compare to the bearing surface
that protrudes and pull the wings and mark the tube.
Decide how much to trim by any method above. If it is an 1/8 of an inch, start
with a 1/16 trim.
If the flap is binding at the outer wing close out simply measure by how much if
you can.
If the tube end is square, use a compass and sharp pen to mark the tube the desired
cut.
I use a 40 grit sanding disk on my 90 degree die grinder to make fast work of the
shortening. Check your grind is square with your 90 degree square.
Clean out the swarf and old Loctite from the tube.
Reassemble and test and trim. Please ensure your flaps will not disengage when
full down and you pull with great force outboard IAW the Safety bulletin.
Reinstall and Loctite, paint and go fly.
Best Regards,
Bud Yerly
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=503376#503376
Message 2
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| Subject: | Re: Flap binding issue - how to shorten the flap actuating |
cross
Hi Bud / Jeff,
It seems you are talking about a small amount of tube- shortening ( 1 or 2 mil
perhaps?) Is it worth considering shortening the flap? The glass flange at the
tip of the flap could stand being reduced that amount without undue weakening
(I think!) and there is enough "spring" in the hinges to allow that - or spacers
added to the hinge bolts?
(I should add that its 25 years since I was at that stage on my Mono so it's all
a bit hazy now!)
Regards to you both,
Ron Jones,
Message 3
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| Subject: | Re: Flap binding issue - how to shorten the flap actuating |
cros
Jeff and Ron and folks:
Sorry to add fuel to this
I agree, the easy way would be to just whack things.
I'm a bit more concerned that I don't know how much the flap tube is pushing the
flap outboard.
Perhaps the flap outboard closeout is not perfectly square after finishing.
Is the flap tube linear actuator drive biasing the flap outboard because it is
installed at an angle instead of dead parallel to the center line?
Is there too much paint and filler added to the flap tip?
Was the wing flap closeout filled and painted too much?
Were the flap arms installed differently during the final assembly?
Is it something simple like some glue or filler preventing the flap pin from fully
seating in the flap tube bearing when retracted which is causing rig and retraction
binding?
So if Jeff is measuring carefully, as I'm sure he is, and he has de-rigged the
wing, checked the flap extension and retraction motion, assured the outboard clearance
is not binding and there is anywhere between 1/8 and 3/16 inch of clearance
in the up position. Then when the wing is rigged the and flap binds with
the pin fully seated something in the drive isn't right. Fixing the drive seems
to be the correct course of action.
If the wing is installed, and the flap is pushed outboard to say 1/16 inch from
the outboard wing closeout when down, during retraction it will definitely bind.
If the bind is reduced by only sanding the outboard flap closeout until clear
in the up position, how much force is on the hinges to keep it there.
What we all want on retraction is a just a nice contact with the wings retracted
pushing the whole flap very slightly outboard. When we extend the flaps we
want the pin straight portion slightly exposed and when we pull the wing flap
outboard until the flap hits the wing closeout near the aileron and the flap movement
will still not disengage the flap pin, it is safe. In fact we want about
10mm / 3/8 inch max exposed of the pin. SB 16 is fairly clear. Bottom line,
the flap pins should not disengage when full down when pulled hard outboard
and common sense says when up do not put excessive force on the flap outboard
and of course not bind.
If this is what we have in flap extension and retraction the flaps will last and
operate flawlessly.
I prefer to fix the rig so nothing is forced over a lifetime. There will be less
pressure on the glass and bearings. Wing fairings fit right and don't drag
and life is good. Not good enough, but good... for a lifetime.
Quick fixes tend to cause lasting consequences. If you do it right, you can sleep
at night and the plane lasts a lifetime.
Of course as my friend Ira says: "Better is the enemy of good, and good is the
enemy of good enough". I'm a centrist, good is good.
Bud Yerly
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=503380#503380
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