desmobob

I've found tons of information and opinions on the best methods for sheeting foam wings, but I have some basic questions:

When (before or after sheeting) and how do you cut the channels for the servo leads, cut-outs for the servos, landing gear wheel wells, retract lines, wing tube, etc.?

I have a Wing Mfg. A-26 Invader kit that has been sitting in my shop for several years and my lack of any experience with foam core wings has kept me from starting it.

Any hints, tips, or links to relavent sites appreciated!

Good flying,
desmobob

DMcQuinn

My Feedback: (13)

Good questions. You must cut a hole for the wing tube and install the phenolic receiver tube first. This is because this tube needs some reinforcement at its end and perhaps along the way also. This is often a piece of lite ply with a hole in it that is the thickness of the wing. The plywood connects the tube receiver to the wing skins. Everytihng else can be done after the skins are on. I use a copper pipe to cut the channels for the servo wires. The servo holes are easily cut after sheeting. I don't have retracts. Because of the high impact load on the retracts, you will need to have some reinforcement here. You may want to build in some hard points under the wing skins before you sheet. maybe someone else can chime in on this point.

JohnW

My Feedback: (6)

I've tried various methods from sanding sticks to hot tools to knives. What I like best for nearly every cut is a Dremel mounted in their large router attachment (the one with handles and the large flat base, not the little ring one… they make two kinds.) As for cutting bits in the Dremel, I'll use either a fluted cutting bit or sanding drum. This makes quite a mess, but allows for very precise cutting and is quick.

For a aileron channel, a 1/2" sanding drum gives a perfect size for the servo leads. This channel can be at the surface, or it can be below. For example, for a below the surface channel, set the router depth to say 1", then drive the sanding drum into the root section of the wing and run it toward the servo bay. This will give you a nice 1/2" by 1/2" channel that is 1/2" below the surface. The 1/8" shank on the sanding drum will tear thru the surface, but this is not significant with respect to structure or strength.

For aileron bays, retracts, etc., I prefer to cut my way down using a cylindrical cutting bit that also has cutting flutes on the flat bottom of the bit. I use one that is 1/4" in diameter and about 3/8" tall. I mark off the area and cut out the first 3/8" depth, or what ever I need. I'll then keep readjusting the router depth until I finally obtain the depth I want.

Wing tube is more difficult and not as much fun as blowing little bits of foam all over. Often you can sharpen the end of the socket tube and use it as a "drill bit." But you may need to build a jig to guide the tube to ensure the hole is aligned properly.

Cheers

Countryboy

My Feedback: (25)

desmobob,

Here are a few links that show some of the techniques used to cut slots in foam for running servo leads & installing retracts.

http://www.quietflyer.com/pdf/08-08howtohotwiring.pdf
http://www.rcfaq.com/answers/modelbu...oamcutting.htm

I think it is best to cut the pockets prior to sheeting. This just saves the aggravation of having to go back and fill the channels of your nicely sheeted wing, however it can be done after the wing is sheeted as shown in the thread below.

http://www.rcuniverse.com/forum/m_95.../tm.htm#952918

desmobob

John,

So I guess you prefer to do all the cutting before sheeting... thanks for the tip on the Dremel router attachement. I will definitely pick one up for this foam wing project and other uses.

Countryboy,

Thanks very much for the links! I put that RCFAQ.com on my favorites list so I can peruse it later.

I feel I can dive right into this project now (as soon as I find the time!)


Good flying and thanks again,
desmobob

JohnW

My Feedback: (6)

Yes, I wasn't real clear, but I will perform any internal foam work, such as servo wire tunnels, before sheeting. As for work that involves holes that are exposed, such as retract bays, servo bays, etc., it is a wash as to when to do that IMO. I've done it both before and after sheeting, pros and cons to both ways; but in general I prefer to do that work after sheeting. Two reasons, I find it easier to sheet if the foam hasn't been routered out, I believe I get better cosmetic results, and I believe I get more accurate positioning by routering afterwards. But that's me. Indeed you can, and I have, cut and even bonded inserts before sheeting, such as servo rails, LG blocks, etc. Cheers.

FLYBOY

My Feedback: (11)

I use a soldering iron to cut my servo wire troughs most of the time. Make sure your foam doesn't produce gasses that are harmfull if you do that. As far as sheeting, there are 2 methods I like the best. If the airfoil it thick and has wood leading and trailing edges, I like a method with wood glue thinned with water, and thin glider wings I use scotch transfer tape.

The wood glue method: Thin the glue with water, paint it on both surfaces and let it dry. Then iron the balsa on just like monokote. It works well and I have never had one come apart.

Transfer tape: I use 3M #924 transfer tape. I use the 3/4 inch. It has a backing on it. Make sure your wing is in its cradle from which it was cut and is straight. Put the transfer tape on the foam side by side covering the entire foam blank. Once it is all taped, peel the backing carefully and lay the sheeting on. It should all be glued together already. Make sure you get it right, it won't move. Trim it and you are done. I use both methods for both power and glider. Both work very well.