What is the preferred method of building a fuselage for electric power? Side thickness, doubler thickness balsa or ply, and what kind of motor mount?  SV 11/Legacy size model.

I use 1/8" sides with a 1/32" plywood doubler with a 1/4" plywood "through the bulkhead" rear mount.  Lots of cross bracing.  You don't have to deal with vibration and you don't need those logs in the front anymore.  I leave the entire front open and use the battery hatch and battery tray to provide rigidity.   As a side note, I put 4 5/16" brass screws through the doublers
into the motor mount.

Design around your electronics.  You have a timer, an ESC, a motor, a battery and a cutoff switch all of which have wires that want to go the other way.  I use a structural hatch that opens up almost the entire bottom front of the plane.

Motor is a Cobra 3520/12 battery is a 5s 3300.

Ken

It was a brain fart - I use 1/32 not 1/16.

1/16 ply doublers seem like a bit of overkill for an electric specific fuselage.  1/32 ply is also probably just excess weight.

I would think 1/64 on 1/8" balsa would be plenty. 
SV style 1/8" balsa-carbon veil-1/8" balsa construction would work well also.

I fixed my post.  I do use 1/32 doublers.  I don't think they are too much weight.  Too weak and the nose is going to twist.

Ken

I talked to a guy yesterday who has a 700 square inch electric stunter with 4-lb. 3/32” balsa fuselage sides and no doublers at all except right at the bellcrank, where he grabs it for pull test.

Is that the guy who is married to your wife?

I talked to a guy yesterday who has a 700 square inch electric stunter with 4-lb. 3/32” balsa fuselage sides and no doublers at all except right at the bellcrank, where he grabs it for pull test.

Does he understand that his 10-12oz battery might weigh 6 lbs or more in a corner?   That is a lot of stress on the wing joint not to have some reinforcement.  Try and not stand close to the circle down wind when he is flying.

Ken

As long as you use a "classical" structure shape, it's going to be quite inefficient use of material. I mean a nose cross section that looks something like this: П.
Immediately when you close the structure to look like O, and add some double curvature to get form stability it will be much more stiff in bending and especially in torsion, with much much less material needed.
That kind of structure comes naturally by molding. L

   I have a feeling that the guy he was talking about knows a lot about stress calculations.

    Brett

I certainly hope so.  I have seen a nose separate in a corner and it isn't pretty.

Ken

No CLPA plane makes maneuvers as violent as a large RC 3D bird, nor will it ever be subjected to such motor torques. And look inside the 3D airframe and be amazed at how little structure there is. Yes we pull from the side - but for the most part our wings are one piece and glued to the fuse so we have even more strength.

Stunt ships were traditionally built with ultra-strong noses to get a consistent  engine run because we needed to tame the vibration of an out-of-balance single cylinder engine in order to keep the fuel from foaming and jumping around and second, to be easy to build with an Xacto knife and sandpaper.

In todays CAD to LASER design world, we can easily built stronger, lighter structures, and electric has tamed the vibration problem.

The stone age didn't end because we ran out of stones, something better came along.

Be bold and try something new.

I'm building two electrics this winter. One has balsa/CF/balsa nose with a pretty traditional cowl. The other is a scale(ish) Laser with the entire front half of the top of the fuse (back of the canopy to firewall)  removable for battery and access to the controls. It's proof-of-concept and if viable ver.2 will have a removable wing. FEA told me that 3/32" balsa with 1/8" Lite Ply was the way to go. Given the omission of the maple motor mounts and and crutch and floor of a Big Jim nose the weight is less than a "traditional" structure and it's more than strong enough for flying or the impulses of a hard landing. 1/16" Lite Ply would be adequate, but really, my planes tend to be tail heavy and I end up adding weight to the nose anyway so I figured I'd just use wood instead.

Chuck

Ken,
I recommend you to take a look at Yuriy Yatsenkos work, to see how little is enough.
Basically a 1,5mm balsa skin with a very thin gf on both sides.
As I said earlier, it’s more about form stability than actual material thickness. L