Ricardo Aurelio

Hi

I'm just about to make my first foam wing, for my .45 pattern (F3A kind) but I still have so many doubts...
Can you gays help me solve my questions?

1 - What should be the "typical" wood (balsa and ply) wing structure?
2 - Should be better to overlap the balsa trailing and leading edge with the balsa sheeting?
3 - Do I need to make any carbon reinforcement along the wing span? How ?
4 - The wing tip edge will be angled (35*). Any suggestion how to make it?
5 - What should be the balsa sheeting thickness?
6 - Can I make the dihedral by just installing the root wing template lower then the tip template in the foam block? What should be the best way to make it?

Thank you

Kenny R

Generally people use 1/16 balsa for sheeting.

To cut the angle for dihedral and the 45* ends sheet the wing first then set the wing cores back in their "beds". Simply cut the ends in a band saw, scroll saw, or table saw.

A wing this size shouldnt need and carbon fiber reinforcement.

In your question number 6, I guess it could be done that way, but is not the easiest way to do it or the comman way.

There are as many opinions on how to do this as there are people doing it, this is just my 2 cents worth.

might want to check this link it has a few details on wing building. http://www.rcuniverse.com/forum/m_13...tm.htm#1379174
Good Luck ! have fun

Ed Smith

In addition to the above

Question# 2,
I do not do this you will end up with a thick trailing edge and a very rough leading edge. I cap them both and sand and carve to shape

Question# 4
I cut my cores on a board,. I have adjustable angles on the end and cut angled wing tips with the wire.

Question# 5
I prefer 3/32 sheet. the extra thickness allows me to sand out all of the seam mismatch and differing sheet thickness.

Question$ 6
To cut dihedral this way will require a very thick foam block, depending on the dihedral. My wings are fairly thin, the root is 7/8 thick and the tip is 1/4, the panel is 26". With just a 3/4 tip dihedral I can just squeeze the core out of a 2" thick block. Remember the wire is cutting on an angle so the core is slightly undersize. The big advantage of this is that when joining the two halves the bottom foam blocks can be used to set up the panels for gluing.

Ed S

Ricardo Aurelio

Thank you for your help.

The 4th question may not have be very clear. I've attached an image of my pattern design. Please note the 35* angle in the wing tip. Do you think I can precisely cut it with a band saw or any similar to that?

Ed, I couldn't understand how you use to cut the dihedral angle[]

Ed Smith

Hi Ricardo,

I cannot attach a diagram so I will attempt to describe it. The foam block is cut to size and shape. I attach the root template to the block. Let's say the root template has 1/2 foam block underneath it. If 1 1/2" tip dihedral is needed the tip template is positioned at the tip end of the block 1 1/2" higher than the root template.

Your fourth question was very clear to me, maybe my answer was not. I have a foam cutting board with lines marked on it. Each end of the board is screwed a flat 1/4 ply plate. I can adjust the angle these plates stick up. I align the core to the plates and run the wire down the angle to cut the wing tip.

Ed S

CafeenMan

I'm not clear on question #1. Are you asking how to design an all-wood wing and also asking about foam or are you asking where to put wood in a foam wing?

Ricardo Aurelio

Ed
I understood how you cut the dihedral. I guess it is just the way I've mentioned in question number 6.
I'll have to make a kind of variable template to work as plates you've described. I'll think about it.
Thank you very much for your help.

CafeenMan
My question was were to put the wood reinforcements in a foam wing, considering a patter plane (F3A type) for .45 engine with 55" ws.

CafeenMan

You don't need any reinforcements on a plane that size. Sheet with contest balsa, add a balsa leading and trailing edge and glass the two halves together. Has been done for years and is well proven.

Johng

My Feedback: (4)

You should take a look at the Extra300 project article on the AMA web site:

Look here: http://modelaircraft.org/mag/hurley/hurleyindex.asp

Scroll down for section 2 - sheeting foam.

I learned alot from that article, even after 20 years of flying. THe tip that I liked most was the method of routing out the foam and putting small plywood reinforcements under the balsa. Done right, the plywood is attached to the inside of the balsa skin when finished. Makes really clean, light, reinforcements. You can also drop in spars and stringer material with the same method.

Anyway, the article is a guide for the whole process.

Johng

My Feedback: (4)

--And to more directly answer your questions:

Build the wings first, then block up the tip and sand the dihedral into the root. You can do this a bit quicker by cutting the dihedral angle into the foam before you sheet, then just sand the overhanging sheet down to the foam.

On the trailing edge, I cut the foam down to a feather edge, then apply the balsa so that it is a bit bigger than the planform area. The trailing edge ends up as 2x thick balsa wood laminated together. THis can then be sanded to match planform shape and thickness taper - although with 1/16" skins, a 1/8" trailing edge is good for most applications and mice and tough.

The leading edge I just clip off 1/2" back or so and attach balsa stick to the front. THen sand to shape.

You'll note that the Giant Scale Extra 300 in the article I mentioned uses 1/16" balsa for the wings and tail surfaces. Anything smaller should be fine with that as well, with one note. If you mount the wing to the fuselage with a wing saddle, you'll want to glass the center section out past the fuselage sides, so the sides cannot make a dent in the foam wing and cause it to buckle. You could also put in a small ply spar for the same effect.

kdheath

Some links to good data:

http://winshipmodels.tripod.com/myfav3.htm

http://www.aerobatix.com/articles/probond/

Ricardo Aurelio

Thank you GENTLEMAN for your kind help.

The information you all gave me aloud me to accomplish my small dream of flying my own design.
Thank you again.

Have a great 2004 !!!