JUST WONDERING WHAT THE OPINIONS ARE REGARDING WHAT THICKNESS OF BALSA USED FOR SHEETING FOAM WINGS. i'VE ALWAYS USED 3/32 AND THEY ALWAYS SEEM TO COME OUT HEAVIER THAN EXPECTED. WOULD SWITCHING TO 1/16 BALSA SAVE SOME WEIGHT? ALSO WHAT WOULD THE STRENGTH FACTOR BE VS THE 3/32...JUST AS STRONG NOT QUITE AS STRONG??
I USE 3M SPRAY 78 (NOT 77) AND THE BOND SEEMS TO WORK GREAT, MUCH BETTER THAN THE 77.
THANKS IN ADVANCE
TOM

Given an equal density, 1/16th balsa weighs 2/3rds of what 3/32" balsa weighs. Here are some formulas to help you do precise weight calculations for balsa and other materials. http://www.nextcraft.com/weightprediction.html

Your question about "what is better" depends on information you haven't given yet. Yes, 1/6th balsa is lighter, and yes, it's usually fine for sheeting wings, (although I prefer epoxy over contact cement) but it really depends on how the wing is built, how you're going to fly it, etc..

Tom:

Have you thought of trying 1/32" Obechi vaneer sheets? Very lite
and super strong.

Randy

Use either all though I prefer 1/16. The weight differance is minimal and will have no effect on flight performance.

Given the choice, I prefer 3/32"...gives me more room for sanding to get a nice finish on the covering and the weight difference is almost negligible unless you are scraping for every ounce. Let's say you are building a 72" plane, around 1000 sq in of wing area. An extra 1/32" of skin thickness, using 10lb density balsa adds less than 3 ounces total to your plane...

Helped do a post-crash examination of a beautiful 1.20 size pattern ship a few weeks ago after it shed a wing in flight. 1/16th balsa had been used for wing sheeting and had been sanded to get a smooth surface for the finish. The sheeting was less that 1/32nd inch thick in several places. One of those places was a critical area near the wing root and spar tube. Foam won't carry much load once the balsa fails. Yes, it had carbon fiber reinforcement too but not enough to make up for sheeting failure.

I'll stay with 3/32nd for anything over .40 - .50 size aircraft.

10LBS DENSITY..... Wow!!! you building a brick? You can build a wing of 1000 sq in with 1/16" 6lb density balsa and still get a strong wing. Use 1" wide c.f 5mil or even fiberglass strips as spars, 2 on top and 2 on the bottom at least 20 inches out. Put a square of c.f. over the aeileron cutouts top and bottom. Use Probond urethane glue as it penetrates well when activated with moisture. First seal your skins with 50/50 thinned nitrate dope and this will control the absorbtion of glue into the skins. Use an 8lb grade balsa for tips and L.E. and T.E. (this wing uses a wing tube and a ply rib at the end of the tube)

I just finished up a set of wings for a pattern plane with retract setups and the precovered weight is 12 oz per panel. On my current plane the wings came out to 15 oz covered with no retracts (fixed gear) and servo a heavy ine to boot(FMA 5601M).

The built up wing on my Hangar 9 CAP came out at just over 3lbs (its just an ARF) and I am thinking of building a foam wing using this technic to try and make it lighter.

It can be done with carefull planning and the right stuff.

No, I was just trying a make a point...even with heavy balsa the thicker skins add less than 3 ounces total. Most contest balsa I've bought has been in the 5.5lb range and "regular" balsa typically around 8lb, but I used 10lbs just to demonstrate a worst case scenario.

I too use Probond and 7mil undirection carbon laminate on my foam wings but I do a lot of sanding to get a good finish, so I'll take the extra wood and sacrifice a couple of extra ounces worth of contest balsa to be safe.

When I use 1/16th, I get paranoid about how much sanding I'm doing and end up with an imperfect finish. Next time I do 1/16th (probably on a Boxer I'm planning to build soon), I'll try putting a coat of sanding sealer on before I start sanding so I won't have to remove as much wood to get the desired finish...