I just finished doing all the inventory on a new GP Extra kit. I separated all the parts into large ziplock bags to have it all organized and labeled each of the zillion sticks that come with the kit. Some parts are slightly warped which do not concern me, but the front top part of the fuse is more more less considerably warped. How can I determine if the warp will affect my final product once the piece is fitted and glued with the rest? If so, what is the best method to un-warp a ply or balsa piece?

Determining if a warped piece is usable or not is a matter of judgment on how badly warped it is, how much pressure it takes to straighten it out, and where it's going to be located. If you are concerned about, replace it. Better off with a new piece than a fuselage that warps after it's finished.

The thicker the material the more likely it is to go back to the warped shape due to internal stresses. Thin sheet it OK to use since it doesn't take much pressure to overcome the warp, but thicker blocks may need to be planed/jointed or recut to true them up. Also if it’s a piece that will be carved, the it may be OK to use it since you’ll thin it out and could remove some the warp inducing internal stress.

Hogflyer

I`m building an Ultimate .40 and just about finished. Replaced 3/4 or more of the wood and this was after I bought new replacements. You can try to contact GP, but I would`nt hold my breath. Their customer service is the worst I`ve run into.

Maybe some images might help.

And some more...

try and remove the warp... you can try to wet the inside of the warp and lay some weight on it till dry

I did. I actually soaked the whole piece and pressed it with 3 10lb bricks and let it dry overnight. Nothing changed.

BTW, what do you think about the corked building surface? Is it a good idea?

plugin,

Actually, for plywood, that's not bad. You usually must bend the piece a little in the opposite direction after wetting it. Using a little vineger instead of water, that will help, too.

That fuselage is built up of plywood pieces. That piece is warped along the length. If the rest of the pieces are fairly straight, I wouldn't worry about it. They will pull the top into alignment.

I've used cork for over 20 years. It's a great building medium. I have a large solid oak library table with a solid core door screwed dead flat to it. On top of the door is ceiling tile, then a layer of 3/32" cork. When the cork becomes worn, it's easily replaced. I replace the ceiling tiles about every 4th plane.

Dr.1

So this amount of warp is not that bad, great. I recon from what I can see in the plans, that it might actually not be bad at all since it lines up with the main fuse sides perpendicularly so it will be forced to sit straight.

For the table I have a hollow door as a base. Then, I have a sheet of ply over the whole door surface and then I have a ply backed cork. The table I built myself and its practically flat. Its off about 1 degree in one axis and perfectly flat on the other axis.

I wouldn't hesitate to use those pieces. It's the nature of wood to warp when the moisture content changes. As long as you glue it straight and hold it that way until it dries, you should be fine.

I wouldn't worry too much about it , if that's the actually piece in the photo that's in question.

You build with that piecce flat and pin or tac your building surface anyways.
have the fire wall hang beyound the table slightly

The sides and the formers will keep it nice and boxie. just glue it striagth and use a triangle to check it.

My dinning room table is made of glass. it's flat, flat. however my gf don't like me build where we eat.lol

GP are pretty good about sending replacment parts if you're really consern about it.

Yeah, I had me one of them for a while (see signature below). Now I got one that suits me much better.

I'll go ahead then and use this part. I'm being really picky as this is my first build and I want it to be as perfect as possible.

Yea, as others have said, the rest of the plane will straighten that out. That is very typical for a plywood piece. Don't sweat it

Hello plugin,

i would glue the piece as it is, i wouldnt go religious about it.

There is a method I used to make parts curved like on profiles.

You hold the part over stream of steam, like from cattle of boiling water.

If you hold a piece of wood over the steam it curves into a bowl.

Be careful! Safety first! eye protection!

I would try it first on non important parts!

It helps BUT then the wood tends to return to be curved so I did it twice.
Then expand about 5% - 10% in length, after a day or two it returns back near it original length.

May be to hold it third time on low steam to release stress.

It’s a method of artists, wood workers, carpenters used 70-80 years ago, they curved 2 cm thick hard wood into 15 cm radius….

Good luck.

I think I'll be safe using the piece as it is. What is now really starting to concern me is (and this may be off topic) being able to assemble the cowling correctly so it ends up at least as a decent job. I already trimmed all the abs and now I've only got to glue it. I plan on using auto body putty to cover all the seams and to sand it so it's ready for paint.

don't sweat it. leave the colwing til after you get it framed up.
scruff the abs on the inside so the fiber glass will adhere better and just apply epoxy.
I use masking tape on the outside to hold it together until the epoxy cures.

don't drill any mounting holes or trim the rear of the cowling until after the engine is mounted.
you have to makesure it dosn't rub the back of the spiner, muffler and stuff like that.

you know...measure twice and cut once.

if i can recall i think it was a built in rigth thrust, so the cowling is not going to sit exactly straight, straight.

when cutting out for the engine..trim a little bit at a time with a dremel. makesure you allow
enough clearence for vibrations of the engine and carb intake.

you can practice with the wheel pants thou.

I just use clothing dye to tint the canopy or go the black out FX and paint the inside.

"Toy airplanes are for people with more money than sense."

So are wives!

Dr.1

Agreed! At least THAT wife was. The current one actually insists that I go fly more often.

If you're concerned about ensuring the fuselage remains straight, use a slow curing glue (titebond or elmers carpenters glue), use lots of pins and clamps to hold things in position while the glue cures, and consider adding some triangle stock along the joints to add support, particularly where plywood joins plywood at a 90 degree angle (fuselage sides, formers). The weight added will be minimal, but the strength gains will be substantial, and it will be more resistant to future warping.

Brad

soak your pieces, then pin them to your plans, when possible, make sure your building board is true. Let them dry, and that should take out all your warp. Good Luck! Al