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jeffwill55(at)sbcglobal.n
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 Posted: Wed Sep 29, 2021 11:26 am Post subject: Flap binding issue - how to shorten the flap actuating cross |
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I am am close to that elusive first flight, but I have a problem I must address, and I could use some help.
I need to shorten the flap actuating cross tube on the port side. Without sufficient clearance, the flap gets pushed outboard as it retracts, and as it is, the port side binds up.
I have only a 1/16” of wiggle room on the starboard side, and I am hoping that will be enough. But on the port side, the flap is really binding in the retracted position, and after checking and double checking, it is clear that the flap actuating tube simply sticks out too far.
As a bit of background, I had two things that had obscured this issue with the flaps. As I indicated before on this forum, I had been having trouble getting the pip pins installed in the wings, both at the wing roots and behind the seats. And until recently, I hadn’t powered up the aircraft. As a result, I hadn’t actuated the flaps, and didn’t know I had a problem with them…until recently.
As for getting the pins in, after lots of measurements. I realized that I had installed phenolic spacers that were a bit too thick on both bellcranks in the sides of the fuselage. I took off the bellcranks, removed the spacers, and tried again. After putting the wings on, with clay on the bellcranks, which indicated slightly smaller spacers, I installed new spacers and that resolved the issue. The wings still don’t just “slap on”, like Bud Yerly’s, but they do go on.
Next I turned on the power and brought the flaps up. At that point I could see that the inboard edges of both flaps (the flap root extensions) needed to be trimmed just a bit, which I did cautiously little by little…three times. On the third attempt, the inboard edges of both flaps cleared the fuselage, with the 1/4 inch clearance gap as well, but then the flaps bound up as they moved to the fully retracted position.
Again, after lots of measurements, it became clear that I have a problem on the port side.
In the last paragraph on step 2 in Chapter 28, it says,
"Cut the cross tube as necessary. When you’re happy with the length of the cross-tube, bond in the bearing housings FL17 using Loctite 638."
Well, it is clear that I didn’t cut the tube quite short enough on the port side way back then (May 28, 2007).
It would be very difficult to move the entire flap actuating tube toward the starboard side, AND it would be a very bad idea, as there is only a 1/16 of an inch of extra space over there, and I would need to move the tube over by more than that to get enough room on the port side. That would just transfer the binding situation to the starboard side.
As I see it, I can cut out a small section of the tube on the port side and either weld it back together or bond it in place with a smaller diameter tube as a doubler inside, or I can simply try to cut off the end of the tube, like it said in the manual.
The latter option seems better, but is more challenging as cutting off the end of the flap cross-tube (FL15) would be hard to do without damaging the GE12E bearing or its bearing housing, FL17, or both, unless I can get them out.
The bearing and the housing are bonded in place with Loctite 638. Can I just heat those up to get them loose enough to pull out? If not, how can I pull them out otherwise?
I would appreciate any input, especially from those who are in the know on this subject.
Regards,
Jeff Williams
Builder A157
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rparigoris
Joined: 24 Nov 2009
Posts: 792
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| Posted: Wed Sep 29, 2021 12:20 pm Post subject: Re: Flap binding issue - how to shorten the flap actuating c |
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Hi Jeff
I would try and remove the bearing. First make a sample and stick together with 638. Then heat using a heat gun and beat it apart. This way you know heat required. Perhaps you can get it off without hurting the bearing? My first attempt would be to use a collar like this:
https://www.mcmaster.com/collars/set-screw-two-piece-shaft-collars/
Idea is leave a few thousands clearance to flap cross tube so it slides. if you can't get exact size, go slightly under-size and bore on a lathe. Install the collar, slide towards fuse, heat cross tube, slide collar against the bearing and using a 3 or 4 jaw slide hammer, grab the OD of the collar and try and hammer it out. You may need to use a blowtorch which will kill your paint and probably damage bearing. If that doesn't work, you could turn a shaft with a step, so perhaps .020" step larger than the bearing bore. Then drill and tap for slide hammer threads. Now for the magic, make it out of Brass and slit an X using a hack saw (2 cuts) the flange about 3/8" deep. Now you can squeeze the OD of the flange down so it fits inside the bearing, when you screw in the slide hammer, the threads will expand the flange and allow you to grab the bearing! Again heat and beat. You need to mess with an undercut that allows for contraction. Good luck Ron P. BTW as far as Europa, lift pins and flap drive pins, good idea to sand them starting with 1,000 grit wet dry and get up to 3,000 grit, then polish them. Before assembly clean pins and bores and put the thinnest of thin amount of grease on them. Using a make up applicator works great, can get at Drug Stores: https://www.digikey.com/en/products/detail/techspray/2313-30/7914580?utm_adgroup=Clean%20Room%20Swabs%20and%20Brushes&utm_source=google&utm_medium=cpc&utm_campaign=Shopping_Product_Static%20Control%2C%20ESD%2C%20Clean%20Room%20Products_NEW&utm_term=&utm_content=Clean%20Room%20Swabs%20and%20Brushes&gclid=EAIaIQobChMI-MTJ24Cl8wIVAlNyCh3H7QY6EAQYAyABEgLiT_D_BwE
Do same for spar pins.
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JohnFrance
Joined: 17 Sep 2014
Posts: 78
Location: Grenoble France
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| Posted: Fri Oct 01, 2021 4:56 am Post subject: Re: Flap binding issue - how to shorten the flap actuating c |
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Hi Jeff,
The idea of putting a lot of heat in that area could cause problems. If you need to remove the bearing I would try and find a way of putting localised heat on the bearing to soften the loctite then pulling off the bearing.
An electric soldering iron either attached to or kept in contact with the flap tube will provide ample heat without risking heat damage elsewhere.
A good blob of solder on the tip will provide a good thermal contact.
If you can attach the iron even better, you will have a free hand.
Good luck
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Europa mono Nr 192 |
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budyerly@msn.com
Joined: 05 Oct 2019
Posts: 286
Location: Florida USA
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| Posted: Sat Oct 02, 2021 7:34 am Post subject: Re: Flap binding issue - how to shorten the flap actuating c |
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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
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