I'm building a 1/3 scale Balsa USA Sopwith Pup and was wondering how to tell if my fuselage is straight (side to side). I noticed that some of the crossmembers are not perfectly straight. I measured right at the end of the tail section center to both side of the firewall and the measurements look the same! Are my checking it right?


Regards,

Bill..

Bill,
I've never built anything as big as 1/3. That sounds big enough to me to stretch a string or thread right down the center line of the fuselage and measure from there to matching points on the sides and top/ bottom of the fuselage for comparison and straightness. This sounds like a really neat model!
Member Bill

Do you have all the formers marked at center? If so, you can stand it on the firewall, making sure that the surface it stands on is dead flat and level. Hang a plumb bob from the tailpost. The string should line up perfectly with the center lines. This also assumes no right thrust is built into the firewall. If there's right thrust, you'll have to shim it up til the firewall is level with the surface.