teamselpats

Im new to airplanes and I was looking at some plans and i was noticing that most of the parts are made of different materials. Most are balsa, but i was wondering about why the different thickness. I thought that it would be much easier to mostly use the same size pieces. Please explain.

danny03

It would be more simple, but would not be very structurally sound to withstand the stresses that are placed on the airframe. Simple explanation and maybe someone else can elaborate further.

teamselpats

i could see it not being structually sound unless you used thick balsa on all the parts. I realize that that could add weight, but it wont add much, and also it will make your plane very strong. explain if i am wrong

dicknadine

another way to look at it. a 1/16 sheet costs $1.50, a 1/8 costs $2.00, a 1/4 costs $2.50. and on and on. multiply all of the sticks the same way. printing on the sheets costs the same. add it up, $$$$ diference . am not ignoring the structural/weight differences. dick

Crewguy25

Designers specify different thicknesses over single thickness for the same reason that some designers specify stick-building fuselages over box sheet fuselages. Less material = lighter plane = better performance or less power required. Why use thick material when you only need thin?

You could build a plane completely out of thick material, and it would be strong. This would be suitable for a trainer that you plan to beat up on, but it would be heavy, and it wouldn't be as responsive as it could be.

I design airplane parts for a living. Real ones. Believe it or not, even when designing parts for a plane that weighs well over half a million pounds, we niggle over 1/32" thickness in the material of a 6-ounce hose bracket.

BMatthews

It won't add much? Actually it does add a lot overall. And a heavy airplane is quite often not a strong one. It's like when you build it heavy you build in the hammer heads that destroy it from the inside out in a crash.

Plywood (the birch stuff not the liteply) is needed for areas of very high local stress or vibration like engine mounts or landing gear mounts. The plywood part passes that stress out to larger areas of balsa via the glue joints. The thin balsa in those areas often has balsa doublers to the stress is further carried out in the heavier thickness to a wider area of thin wood. Thin wood can withstand a lot of even stress much like an eggshell can but it's not good for high pinpoint local stress.

It is possible to build a model out of only a couple of sizes of sheet with some miscellanious other materials tossed in but it takes some care and attention. The model below used only 3 sizes of wood, 1/16, 1/8 and 1/4 with a couple of small bits of 1/2 for the nose blocks. The wing in particular uses 1/16 for all the construction other than the full depth spar of 1/8 and the leading edge of 1/4 sq.