OK. Since I was a young lad building balsa stick, rubber powered planes, I've yet to build a straight fuselage.

Just completed a 1/2A kit with a crooked fuselage...I pinned it all down, made sure it was straight, then glued. The next morning when I unpinned it, it looked good. A couple hours later it was bowed!

I'm thinking of building a 40 sized Kaos (tower kit), but i'm worried about all that work just to have a crooked plane.

I hear some kits inter-lock and can't be built crooked...but for the ones that aren't designed that way, what can I do to build it straight?

I am not used to builing the smaller size models, mainly 80" to 140" spans. Sounds like you have an open airframe or thinly sheeted model. What type of glue are you using? I use CA for the most part and never have a problem with a twisted or bowed airframe. The smaller models can do this more easily than the larger ones. You can get some of this out when covering them. If your building a 1/2a you should have no problem straightening it when you cover it.

tell you what I do----first, I glue the triangular stock longerons onto the fuse sides as called for in the plans. Then I glue the first 2-3 formers at the front of the fuse---glue the first few formers at the front ONLY to this point. Use a square to make sure they are 90 degrees to the fuse sides. Then I take this partial assembly and place it over the plans---usually with the TOP side of fuse facing UP---you want the bottom of the fuse absolutely flat against the building board and perpendicular to it---place the fuse assembly right on top of plans. Drive small drywall screws (3/4" or 1", 2-3 per side) thru the beveled edge of the longeron, right thru and into the building board. Do the same for both sides---just use screws in the front half of the fuse to this point---the back half of the fuse will have no screws or formers installed yet. The front half of the fuse should be absolutely solidly screwed into the board---flat to the board and firm---no "wiggle" movement at all. Then I curve the back half of each fuse half (separately) to match the plan---and while holding each side in place over the plan, I screw each (thru the longeron) down to the building board. I usually end up with 5-6 screws per fuse side---screws spaced roughly equally from the nose to the tail of the fuse (# of screws depends on the size of the fuse). The fuse halves will NOT move and each side will be right on top of the plan----completely straight---no bows or "banana". I then glue in the rest of the formers. When all the formers are glued in place, I then remove the drywall screws and take the fuse off the board and finish the fuse (sheeting bottom, turtledecks on top, etc,...). I use drywall screws because the threads are very sharp and "bite" into the building board easily. They are also very small guage (diameter). They also back out easily. Just make sure you don't put them where you can't later get 'em out---too near formers, etc,.. . The small screw holes made in the longerons are not important. Sometimes, the design of the kit is such that you have to screw the fuse to the board with the TOP facing up, sometimes with the BOTTOM facing up. It really doesn't matter. The important point is that the "flat", or STRAIGHT edge of the fuse (top or bottom) needs to be screwed flat to the board. I've used this technique on .40 planes, .60 planes, and Giant Scale planes. Seems to work every time---at least it does for me. Now, this obviously won't work for round cross-section fuses. Different techinque there,....