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Phil Barnes
100 Posts |
 Posted - 12/03/2003 : 10:07:19 AM
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It is important on the the Aegea Mantis wing to reinforce the flap servo holes to prevent buckling of the top skin. When this issue first came up, a number of people E mailed me with some very good methods that they had used for doing this. I no longer have those E mails saved due to recent computer and E mail provider "issues" so I am asking for you guys to post your suggestions here.
Phil |
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Anker
83 Posts |
Posted - 12/03/2003 : 11:10:48 AM
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I just scraped all the foam out of the wells and reinforced the top skin with a single layer of 5oz glass. The sevos are epoxied to the top skin and are a tight fit to the servo wells. I cannot see any buckling and I also launch hard.
Anker |
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F3jeb
103 Posts |
Posted - 12/03/2003 : 1:07:27 PM
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This is the original message sent by Phil
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Remove any remaining foam in the servo bay all the way to the top skin.
I am thinking that there is about 1/16" or so of foam thickness left though
I don't have a wing here to look at anymore. Install a 1/16" thick plywood
plate in the hole that completely fills the hole. Use something like five
minute epoxy or thickened epoxy and be sure that there are no gaps
between the ply plate and the top skin. Line all four sides of the hole also.
This could be done with small pieces of plywood . Or it could be done with
pieces of fiberglass that tie the ply plate to the servo bay sides. Either way,
the idea is to lock the ply plate in place so that it can't be pushed into the
hole or be pulled out. If you use small ply pieces to line the sides of the
servo bay then be sure they are bonded to the ply top plate at least with
glue fillets or better still, with small strips of glass.
Phil |
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Tony D.
1 Posts |
Posted - 12/03/2003 : 3:22:06 PM
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When I lay up the wings I add a small circle of Kevlar on the top surface over the area where the servo will be installed.
I line the servo bays with carbon plate made from a couple of layers of 4.7oz. carbon cloth.
I have not seen any buckling on my wings, I am using the Drela carbon capped spar and not a carbon tube.
Tony D. |
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snhrccsec
1 Posts |
Posted - 12/03/2003 : 9:54:11 PM
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OK, I know this doesn't apply directly to the Aegea question, but I have seen some buckling of the upper skin on my MH-32 wings. I had attributed it to the heating of the epoxy used for installing a .032 plywood plate to adhere the servo to. Is this possibly buckling from stress? It almost looks like a couple of thumb print depressions.
Thanks,
John Hayes
I-SOAR |
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Phil Barnes
100 Posts |
Posted - 12/04/2003 : 01:18:11 AM
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John
The buckling of the skin over a servo hole that we have seen has always been a long crease running chordwise and centered somewhere over the servo bay. It is possible that the MH32 wing could be sosceptable to the same problem. A couple of these wings in the CRRC club did develop creases over the single flap servo hole. These were the only MH32 or 7037 wings that I have heard of so far with the problem. The solution would be the same as the Aegea wing. It sounds like the addition of a plywood plate inside your servo bay would have helped as long as you did not leave gaps between the ply plate and the top skin. Any space between the ply plate and the top skin should be filled with epoxy or filler. If you press on top of the servo bay with your thumb it should feel firm and solid.
Phil |
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Phil Barnes
100 Posts |
Posted - 12/18/2003 : 11:53:32 AM
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HANS WIEDERKEHR'S post, I have simply re-filed this post under this topic heading (Phil Barnes, moderator):
OK boys here goes:
The way I installed my servos in the wings of the Drela Mantis a method I learned from Mark Levoe way,way... back with a few simple adjustments:
First you get the "blue" masking Tape 2" or wider from Home Depot. This "blue" tape has less adhesion and will not give you as many pin holes when you pull it up.Place it over the hole so the hole is covered up with a 1/2 overlap around the hole.Next get an old servo (or case) of the exact same servo you will be using.Wax it throughly with butchers wax or some type of paste wax. Next purchase some carbon mat and cut out a piece 1" widen than on all four sides. Mix some slow set epoxy and coat the inside of the hole. (I also coat the mat with a fine coat to insure good adhesion).I then place the mat over the hole with the coated side down and force the servo down into the hole bringing the mat with it. Epoxy will then ooze out the sides onto the tape you put down. It is smart to wipe away as much epoxy as needed.Next let the epoxy cure and remove the servo.You can also use the servo that will remain in the wing to insure an even stronger bay area. Carefully file the excess mat away that should now be sticking up along the sides of the hole. BUT YOU MUST STILL COAT IT WITH WAX,CUS IF YOU EVER WANT TO REMOVE IT ,IT WILL BE IMPOSSIBLE WITH-OUT DAMAGING THE WING..........BELIEVE ME .I HAVE DONE IT!!!!!! Also, you can install two spruce mini spars for/aft of the servo around 2 to 3 inches along with this method. I have never had a wing kink/crease using this method.........the only draw back is it is time consuming and messy.
Hans |
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Phil Barnes
100 Posts |
Posted - 12/18/2003 : 12:04:11 PM
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I like Hans' method but I would still take the additional precaution of digging out the foam all the way to the top skin and installing a 1/16" ply plate with epoxy. Then go ahead and finish with Hans' method. The Aegea wing is a special case. The flap servo hole is under a very highly stressed area of the top skin and every precaution must be taken to be sure that the top skin cannot buckle. If foam is left between the servo case and the skin, there is still a possibility of the skin buckling into the hole by crushing the foam. The ply plate is additional insurance, reinforcing the hole well enough so that it will be strong enough even with a loose fitting servo in the hole (think about the case where you change some servo gears at the field and then reinstall the servo, now the servo is not locked in as tightly as it was and might not support the top skin as well)
Phil |
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Reinforcing methods for flap servo holes
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