Ok so im at the point in the instructions to balance my plane. It says that on the PT-40 the balance point is 4 7/64" from the leading edge. I have the GP balancer. And have set it so the points are as close to the fuselage as i can get them. I have the battery moved back as far as possible as with the servo tray, and I am coming up very nose heavy. Has anyone balanced one of these and know if that is the correct point. I thought i read somewhere on a thread that that wasnt accurate for the cg. The 4 7/64" puts it right behind the main spar. If it makes a difference the engine im using is the OS 46 LA. Any insight on this would be great. Thanks.




john

Hm.. nose heavy with an LA. Ok. I was going to ask you about why move the battery pack rearward, but I can understand. One solution is to move the battery pack even further back, even behind the servo tray, wrap it in foam, and tape it in place somehow. The alternate solution of course, is to add weight in the rear somewhere. You could do a combination of things.. move the engine back as far as it will go, move the battery pack rearward. then add weight in the rear.

CGr.

I balanced mine on mine on the main spar, of course I used my fingertips to replace the CG machine.

Just wondering how nose heavy are you? I have an OS .46 FX in mine and I had to move the bat up front just behind the tank.

You could try to replace the nose wheel with a foam wheel, that would save some weight. What did you do in the construction to have the nose so heavy? You are far better to be a bit nose heavy, but not so much that it is a problem in flight. Remember a nose heavy plane flies poorly, a tail heavy plane flies once.

Add a bit of lead weight to the tail and it should resolve your problem as well.

Good luck, it is a good little plane to start with, I have bashed mine around a ton and it still flies as well as day one.

Im not sure about the exact weight that it is heavy but when i put it on the balancer the prop is touching the table. Maybe ill try it on the main spar and see what that does




john

LOL it must be time for new glasses[:@] i had it at 5 7/64" It is now just slightly nose heavy, it is almost sitting level on the balancer




john

Beware, if you balance this model as per plans, it will be tail heavy and turn into a beast, balance it on the main spare and its great. there have been several threads on this[:@]

That sounds like like the cg point is too far back. I would balance it at the main spar, that is the general rule on planes like trainers. Mine is only about 3.5 inches back just barely in front of the main spar.

PS: Do you have a ruler that you can actually measure out 7/64 of an inch with?

Yeah, so that would cause the problem. Mine is a touch tail heavy halanced on the main spar, it flies very well, although I think that my 8 year old son will take over the plane this season as I am now on to my first low wing (4* 60, and have a Twinstar, Corsair and Cub ready to go, not to mention a 1/4 Chipmunk that just needs the electronics put in be ready) The PT-40 is a great little trainer, I hope you built the B wing, the A has way too much dihedral in it.

Good luck and please post a picture, would love to see how yours turned out.

Yeah I built the b wing. I have flown before but it was a long time ago, and I decided a couple months ago to get back into the hobby. My first kit is almost complete just a few more things to hook up then break the engine in. I have already started on a second PT-40 that im making into a tail dragger.


john

If you have a combination sqaure laying around, this is ideal for marking the Cg on your wing. If you don't, a cheap one is only $5 at Wal-mart. Just set the square at your desired point and lay the ruler part on the wing bottom while pressing the short part against the leading edge, requires you to tilt the ruler on edge a little, and then you just mark the wing along the end of the ruler. BTW a slightly repeat slightly tail heavy plane will take off quicker and land a little slower and easier than a nose heavy plane. This is how I set up my trainers, just my preference though.

I built two of them as well, the first was with the A wing and I did not like the wing, so I bought another kit ($15 more than just the wing kit) and built my second one. I later did a bunch of conversions on the original plane - it earned the name the Basher because of all the mods. I made it a tail dragger, took all the dihedral out of the wing, put an OS .61 in the front of it (it was a .40 size) and extended the rudder and elevator.

I had a few flights on it, and then had it up for what was it's final flight, doing a very basic circuit something came off of the plane and it went into a shallow kniffing kind of dive. I have not been able to find the wreckage.

If you have not yet built your second PT-40, do yourself a favor and pick up a Sig 4 Star, as easy to fly as a trainer, but much more airplane, and a lot of fun to fly.

Good luck!

I have already started the my second PT-40 have the fuselage almost done already. And I have a Rapture which will be my next build.

Brett65 no my ruler wont actually measure 7/64 I just put it slightly in front of the 1/8 mark but I am going to balance it on the main spar anyway


john

Balance is not that critical. If you're very close, you'll be OK.