Jan 31, 2014, 01:17 AM Registered User Joined Jan 2014 2 Posts Question 200% equals 200% Thicker Foam? Hi, I am about to build http://www.badtothefoam.com/Shuttle.html, a space shuttle for a friend. He wants it 200% sized, for this particular model, do I use 6 or 9 mm depron foam? I would much rather use 6 mm since itīs difficult to find 9 mm. Will it look thin and weak with just 6 mm foam? A 200% increase of this model would make it, 1.2 m long and 1.1m wide.
 Jan 31, 2014, 03:13 AM Registered User United States, NY, Fulton Joined Sep 2013 65 Posts My \$0.02 is that you should stick with 6mm foam, but double it up where you think the high stress areas might be and use more reinforcement (spars, CF braces, etc.) That way you get a much lighter model for its size. There is also something called the inverse square which explains why elephants are more efficient than mice, but the details are foggy to me. The designer probably chose 6mm as that is what he had around
Jan 31, 2014, 08:28 AM
Registered User
United States, PA, Easton
Joined Dec 2010
321 Posts
Quote:
 Originally Posted by Simdor Hi, I am about to build http://www.badtothefoam.com/Shuttle.html, a space shuttle for a friend. He wants it 200% sized, for this particular model, do I use 6 or 9 mm depron foam? I would much rather use 6 mm since itīs difficult to find 9 mm. Will it look thin and weak with just 6 mm foam? A 200% increase of this model would make it, 1.2 m long and 1.1m wide.
I know a guy who uses the 1/2 inch foam insulation from home Depot or Lowes to build his larger products. It requires a lot less stiffening than 6mm depron. My rule of thumb is any wingspan over 40 inches starts getting tricky with 6mm depron. The reinforcements needed to keep it stiff over a series of flights, and to keep it from cracking on landing means that you are adding a lot of extra weight, so I don't bother. I can't see where you are located, but Grayson hobby in the USA has 9mm, Btw.
http://www.graysonhobby.com/catalog/...ts-p-1011.html
Jan 31, 2014, 10:15 AM
An itch?. Scratch build.
South Wales U.K.
Joined Mar 2003
12,270 Posts
Quote:
 Originally Posted by f1wanabe I know a guy who uses the 1/2 inch foam insulation from home Depot or Lowes to build his larger products. It requires a lot less stiffening than 6mm depron. My rule of thumb is any wingspan over 40 inches starts getting tricky with 6mm depron. The reinforcements needed to keep it stiff over a series of flights, and to keep it from cracking on landing means that you are adding a lot of extra weight, so I don't bother. I can't see where you are located, but Grayson hobby in the USA has 9mm, Btw. http://www.graysonhobby.com/catalog/...ts-p-1011.html
You only need a balsa spar and leading edge to give Depron plenty of strength.

Examples, my
72" Spitfire, 6mm lower skin, 3mm upper skin,
90" Sunderland, 67" Dauntless, 50.5" A-10 Thunderbolt, are all 3mm upper and lower skins.

P.S. Forgot, there's also my 64" Mig, twin ducted prop, also 3mm upper and lower skins,
Last edited by eflightray; Jan 31, 2014 at 10:19 AM. Reason: Addition