Hello folks!

New member here, & new to RC Planes. Recently, I decided to build a Great Planes PT-40 given to me as a gift from my wife & daughter about 15 years ago. While the box was opened and a few supplies purchased, it has basically remained untouched, but I've recently developed a real interest in getting it built.

Unfortunately, I have only just begun & I have a building question I hope I can get some help on. Following the build instructions, the second step is to glue the fin & forward fin together but my pieces don't match up well. Laying the pieces on the plan, it appears the forward fin might be cut a little short in height.

If I align the bottom of each piece on a straight edge, the top of the forward fin mates to the fin as in this pic:




If I align the leading edges on a straight edge (you can see the bottom of of my dial calipers acting as the straight edge in the pic), the bottom edges look like this:



Can anyone offer advice on the best way to deal with this? My thought is to align the bottom edges, glue together then plane & sand the leading edge of the upper fin (NOT reducing the overall height) to match the forward fin, but I'm not sure. There are trim pieces that attach to the bottom edge of the fin assembly covering where the mating surface attaches to the stabilizer, effectively hiding any gap that might be present if I align the top but I don't know if that would be wise.

Advice is appreciated!

You're approach to fixing that should work just fine. You will never notice any difference in the way the plane flies.

Another alternative would be to glue a piece of balsa (1/8" wide or so) to the back edge of the forward fin which would in essence allow you to make it taller (but also wider). However, from your picture, it looks like the assembly is already wider than the plans show, so just sanding down the front edge to get a nice smooth line from base to tip is probably certainly easiest. If you want to get fancy, you could add the piece to the back of the forward fin and then sand the forward fin to match the plans and then add it to the fin. If so, try to use balsa that is the same hardness as the existing fin/forward fin.

Guys, is it possible that the rear piece is done that way INTENTIONALLY as a way to help secure it to the aircraft's fuse and horizontal stabilizer?

Hydro Junkie - thank you for the input, but I don't think so. If you look at the pic below of the plans, you can see where both the bottom & top tip of the forward fin align with the fin edges.

Align the pieces on the bottom, that tiny spot on the leading edge will disappear when you sand the radius into the the leading edge. If not a dab of filler and it all goes away.

Speaking of filler, I use Elmers, it has an orange top on the can. it sands like balsa, dries hard, fills really well.

Buzz.

Call Great Planes - that's just not right. The forward piece of the fin is not the right size. I built one many years ago and don't remember a problem at all.

Curious if you tried turning the fin around so the back is the bottom and the bottom is the back.

Yes, I did that - it will only fit the way I have it oriented in the pics above. I think the forward fin is just cut inaccurately.

Don't over think this. If there is no slot in the horizontal stab for the long piece to fit into then it was meant to be glued flat on top of the stab with the two gussets on each side keeping the rudder in line with the wings and stab and giving it some strength. You don't want to compromise the size of the cut out for the elevator deflection so glue the two pieces so they are flat on the bottom. Then sand the leading edge of both pieces until they blend into one straight line. Shape the rest of the vertical fin as per the drawings and be done with it. 1/4 inch difference than the plan will not make one bit of difference in how it fly's.

Dennis

It appears to be cut out of a flat balsa sheet. Go to your local hobby shop (you don't list a location) and buy a sheet of 1/4 inch (looks like) balsa and using the plan as a pattern, cut out a piece that will fit. A couple dollars for the balsa and five minutes cutting it out should cover it.

Talk about over thinking !!!!! Just trim it flat and glue it . It's just a trainer and won't make a wiff of a difference . ENJOY !!! RED

Make the bottom edges match, glue it that way. Take your long sanding block and just make that step disappear. No biggie. Unless there is a slot in the horizontal stabilizer. But that really is nothing to sweat about. Glue it together, sand it, make it pretty. That's what sanding blocks are for.

X-2 on sanding block. Simple fix.

Sand it.... Looks right ... Fly right

Sand it and use the TLAR method.
TLAR method is -
That Looks About Right.

I agree . Aline the bottom , glue it. The front usually gets sanded anyway so sand till you are happy and move on to the next step .