cuttin a hole in a foam wing
 

hey, i am building a plane with foam wings, and need to know the best way to cut a hole running span wise for a wing tube. I was thinkin of cutting a pilot hole with a brass tube, then using my hot wire to cut the actual hole out with. also, i was wondering where i could find a tube to glue into each wing half.
thanks,
andrew</p>

RE: cuttin a hole in a foam wing
 

Are the cores cut?
I cut my holes for the tubes in the core before cutting the airfoil, two templates equal distant above workbench, both holes cut at once. then I cut the airfoil. Here's a stablizer I did some time ago, same with wings, just bigger hole.</p>

RE: cuttin a hole in a foam wing
 

I clamp a wing tube at the desired location, then I place the cores in line with it where I want to cut the hole. I use a socket that is sharpened at one end and feed it into the core while turning. You will get about an inch to an inchand a half deep before a cylindrical plug will break off, and needs to be cleared. The core should be ''regestered'' to the jig so you can remove it to clear the foam plug from the socket, then replace it in the exact same spot. I clamp rails at the trailing edge and tip for this.

RE: cuttin a hole in a foam wing
 

I have already cut the foam.  I was just wanting to make a guide hole so i can cut the final hole with the hot wire.  If the brass tube idea will work, i will try it.  I just dont really want to bugger them up, cause 3" foam is about $20 per sheet.  Also, is it possible to just fiberglass over the foam, or is balsa sheeting a must?</p>

thanks,</p>

andrew</p>

RE: cuttin a hole in a foam wing
 

Andrew,

If it was me, I would simply send your stock to someone that cuts fom wings repeatedly.

An interesting note, the tube doesn't have to be in another tube hole. It can also be slid into a snug box.

Charles

RE: cuttin a hole in a foam wing
 

Not sure you understood what I meant. A picture is worth a thousand words.</p>

RE: cuttin a hole in a foam wing
 

I will definately do that next time  I cant really do the locator block thing, cause the wing is already cut.  maybe i can improvise

RE: cuttin a hole in a foam wing
 

do you still have the core beds? you could sandwitch the cores back in the beds then you have the solid edge to block in just an idea

RE: cuttin a hole in a foam wing
 

Hi ! I use an aluminiumtube that i have filed sawtoths at the end. I make a guide of plywood and just drill the hole by hand.The guide needs to align the tube in both angles. a boxlike thing with two holes in opposite walls. I simply, use woodscrews to hold i to the core.Not sure if this is understandable, i have drawings i made earlier. will try to find them.Jonas

RE: cuttin a hole in a foam wing
 

OK, found it!

RE: cuttin a hole in a foam wing
 

thanks, that helps alot.  I asked a few questions at the field, and i was told that 6" is all i need.  the club "guru" has experimented with lots of different lengths, and he said for a 40cc plane 6" is all that is needed.  he tried 5" and had one fail.  This plane is a 78" span with a 25cc engine, so it should be lots.  I dont expect the final weight to be much over 12 lbs, so it should be alright.  Now, i just have to find an aluminum tube, and also find a cardboard tube to glue into the wing.
thanks again for the advice

RE: cuttin a hole in a foam wing
 

One source for aluminum tube is here.

http://www.aircraftspruce.com/catalo...ube_6061t6.php

This is a source for Carbon Fiber tube = Lighter, but more expensive.

http://www.wildharerc.com/html/prices.html

Rather than find a cardboard tube, make your own sleve from 2oz fiberglass. Doing it this way will give you an incredably good fit.

Wrap your wing tube with two wraps of 1 mil painters drop cloth. use scotch tape to secure it to the tube at the ends.

Cut a square of 2oz FG 15''x long enough to wrap twice (2x(pi)xtube diameter)

Wet the FG w/finising epoxy like Z-Poxy, and wrap it around the tube. Wear vinyl disposable gloves when you do this. Squeege off excess epoxy and set the tube on stands so that the layedup sleeve doesnt touch anything.

When the epoxy is dry to the touch, but not fully cured (about an hour for Z-Poxy) pull the sleeve off the tube, and remove the drop cloth from inside the tube. This is easy since the epoxy doesn't stick to the painters drop cloth.

Now slip the sleeve back onto the tube and allow it to cure for 24 hrs. This is important. if you allow it to cure with out removing the drop cloth, it will shrink and become very hard to pull off. The 2mill wrap of drop cloth not only acts as a release film, it also alows for shrinkage.

RE: cuttin a hole in a foam wing
 

thanks for the tip.  I tried looking around for a tube, and didnt have any luck.   as far as the aluminum tube, there are a few welding shops around and most are more than happy to help.  As per fiberglass, will the type from canadian tire work? or is it too heavy?  $11 gets me a pretty big sheet of it, and there is no shipping.  Also, how do you cut the fiberglass without it unravelling and making a huge mess?

RE: cuttin a hole in a foam wing
 

The stuff they sell at auto parts stores for body work is probably 6-8 oz and it will work, but will come out a little heavier. As for cutting it, you just have to learn to handle it carefully. An Olfa cutter works well, and can be purchased at a fabric store. This looks like a pizza cutter, but the wheel is razor sharp, and give the cleanest cuts for FG. You will need to get a cutting mat too.

RE: cuttin a hole in a foam wing
 

i saw one of those at michaels, and thought about buying one.  I guess ill have to make a trip there after work.