Hey,

Just wondering how much washout is in a 60" wingspan trainer, maybe a rough range??? How do you go about putting washout into a wing? Im scratch building a trainer and am wondering how much washout i rly need, and where do you want to place the piece of wood under the wing, etc....??? Any help with this would be great! Also any articles, websites, etc...that might have more information on this could help as well. Im guessing that a 1/8" piece of balsa would work, or a 1/4", thats about as much as i know on this. Please help Thanks in advance

David

If it's a constant-chord wing, you don't really need any washout, since aerodynamically the wing is effectively washed out by the way it affects the upwash along the span. If you don't like this opinion, I sure you will see others, but this is just MY philosophy. If I was building a trainer, I wouldn't use any, even a basic trainer that I was going to teach with.

What mesae said is good advice. You really don't need washout on most trainer wings.

However, I always make sure that every one I work with doesn't have washin. You'd be surprised how many "flatbottom" wings show up with drooping TEs out at the tips. It usually comes out just running an iron over the covering along the top while holding just enough twist to see wrinkling. And while I'm doing it, I usually put in just a hint of washout. Just to hedge the bet against it coming back.

BTW, what is the airplane?

I think the best answer is to build it according to the plans. A good trainer will have dihedral, washout, incidence, etc. all worked out and the instructions should walk you through everything to do to build a good, solid flying airplane.

If the instructions don't tell you to add washout, that usually means the plane doesn't need it.

Dave

no real airplane, just scratch building a 60" wingspan trainer

its hard to know, im following a couple of other trainers for cg, wing chord, etc...but wanted to check with everyone here to see about the washout since i couldnt find to much on that. im drafting the plans atm so im kinda doing it as a i go here, then getting it cutout, then building it, and see how it flies

mesae's got it... if you have a constant chord wing, you don't need any washout. If you decide to taper the wing, then the amount of washout will depend on the amount of taper and the airfoil sections chosen at the root and tip.

Cheers!

Jim

thanks everyone for all the help

Well, call me a belt and suspenders sort of guy but I'd still like to see a bit of washout on a trainer. Especially if it's going to have ailerons. A bit of washout can make the difference in a turn when low and slow if the ailerons are used with a bit more gusto then they should have. It won't save the model from a gross mistake but it may let the pilot get away with a smaller one.

I'm guessing that the wing chord will be in the 10 inch wide range for a nice trainer like aspect ratio of 6:1. If so then about 3/8 inch of washout would be my suggestion.

It's normal to just warp it into the wing using the covering and the heat gun or iron to warp it in and hold it. If the wing uses a D box leading edge then shimming plus clamping or wdighting the building board to as much as it'll twist up to the max is also a good idea.