I am currently building a PT60 and I'm having some trouble with the engine compartment doublers not fitting correctly. When I put them in there is a gap about 1/8" from the firewall in some places. My question is should I glue some wood on the back side and try to shape it to fit or can I fill the gaps with a wood filler?

I'd glue in some wood with plenty of epoxy, much stronger than filler.

I have built many PT-40's and the PT-60> I have found that the PT_60 does have problems with cutting and fitting properly. as to your question, yes fill the gap with wood (ply) and use Epoxy as moosimo1 said. JUST MAKE SURE that you get the firewall properly lined up. I also find it to be a very heavy plane. it seems to be also very tail heavy. I am in the process of cutting lightning holes in the aft section of the fuse to remedy this problem. I am using a OS 70 four stroke also. If you havent built the wing yet build it with the sport wing version (you have to cut the spar joiner) you will get more fun out of it. I use this plane to help other new pilots learn to fly. its very durable and easy to repair. have fun!

If this doubler is ahead of the firewall, it's purely cosmetic. Norm's advice is correct. Simply fill in the gap with wood and CA.

However, you might want to look at the plans again and find out if this is a GP cutting error or something you did in building. Check the firewall location.

Dr.1

Thanks for the responses guys. I have doubled check the plans many times (very obsessive compulsive) and every thing else lines up as it should. It seems as if the angle of the doublers is off just enough to cause a gap of about an 1/8". I think I will epoxy some wood to them and trace the pattern on them then cut to fit. Thanks again.

When I did mine I glued the doublers so they were against the firewall and sanded the fuselage sides to match them. The previous posts are right about the plane building tail heavy. With a TT61Pro up front and the battery under the fuel tank, against the firewall, it still needed around 3 ounces on the bottom of the engine mount to balance.

Mine went together with no problems -parts fit well. Must have been a lucky one.
My PT60 was tail heavy as well, had a OS 60FP with a 5 once heavy hub on the engine and 3 onces lead on the firewall. Flys great, and the engine ran smooth with that flywheel-like weight, and can still accelerate quickly as well. It may be tail heavy, but it sure is durable (knock on wood). If I built it again I would try to lighten the tail, and build the wing with less dihedral (really wish I did it that way). Been thinking of putting mine on floats.

Something strange on mine; the cheek doublers were laser cut. The entire kit, with the exception of these 4 pieces of wood, was die cut. I'm thinking they tossed the wrong parts in the box but it only took a minute to sand the fuselage sides to match.

The PT-60 is built like a tank. It is really tough. I built the 'sport wing' and ended up with 3.5 inches total dihedral (plan called for 4 inches) because everything fit and I stopped sanding when all the spars, sticks, and joiners fit with no gaps.

It is a great flying plane and a good first build.