1990s vintage LT40 build thread
 

Am going to build my first kit, an old LT40. Been sitting in the box in a barn since the '90s.

The piano wire is a bit rusty, but that's the only flaw I see so far.

I have gotten as far as spreading out the plans.

Planning on 5S on a 700 KV GEForce motor, with a 12 to 15 inch prop.
Maybe 14 is the largest that will fit, we'll see.

A 13x10 would probably give it unlimited vertical, so I don't need to go crazy on prop size.

I will be looking for the best way to convert it to a bolt-on wing.
2 pins and 2 bolts or 4 bolts, either way is fine with me.

I'm sure it's easy, but for this plane is there a real advantage in putting a servo on each wing?
I won't be using the ailerons for flaps or such.

I'd have to go out and buy 2 servos (I'd like 'em to match if I did it that way), and funding is tight.

I would got 2 pins in front and two nylon bolts in the rear. On the LT-40 I built back in 2004 the ailerons ran the length of each wing and were connected controlled by the same servo with two short pushrods. I know yours is an earlier kit but unless the ailerons are different I see no advantage to using 2 servos. I will be watching your build good luck!

Ailerons are exactly the same way as the newer models.

Someone somewhere posted spoilers were useful in the wind to get the plane to come down, that spurred the thought that while I wouldn't use flaperons, maybe using spoilerons (is this 'crow?'), that is, pitching both ailerons up might be a way to dump some lift.

If I could make this enough of a short-field plane I could fly off my lawn...

If this kit was old enough I'd see if sig would want it for their archives, I'd trade 'em for an ARF.
Damn I'm lazy.

What kind of radio do you have? Most of the computer radios now days (including the Futaba 6EXA I bought in 2004) have a setting to set the ailerons to flaparons (this may require using 2 servos for the ailerons). Maybe your radio has this ability? From my experience with my LT-40, flaps are not necessary and you probably would never use them. I would stick to building it as designed except whatever modifications are needed to use an electric motor and LiPo. Don't over complicate the project wait until you get into to scale aircraft and then go nuts! (Says the guy in his second year of building a Cessna 182.) ;)

Flaps, no, but spoilers maybe. Cant both ailerons up a bit and it reduces effective camber.

Come to think of it that would take two channels for the ailerons on the RX as well as two servos.

I just want to think of all the things I might want to do (some just for grins) before I start gluing stuff together.

Hey, I build every plane 6 or 7 times in my head before I ever glue the first piece! Advance planning never hurts!

My biggest concern at the moment is actually, how do you secure what the wing bolts to?
Can't just glue some built-up ply angle brackets to the former just behind the wing, I assume.

Along for the ride. Always eager to learn. Thanks for posting

Dont waste time with two servos, this pane flies great with the single servo set, and I have never had an issue landing it. I would do a dihedral mod by reducing it down to about an inch, it will be less like a trainer and sportier too. Mine is bolt on, what I did was take the rear brace that goes at the back of the fuse where the wing mounts and copy that to a 1/4" plywood, then glue the ply to that piece after it was installed. The wing I dont remember if I needed to add balsa blocks to where the bolts go or not, so consider that area when assembling.

On the front of the wing I made a notch behind the leading edge where the two halves join, and glued in a 1/4" plywood piece, that hangs down about an inch or so, and put two dowels in that, I also put 1/4" ply in front of F3(windshield area) so the pins have something to hold onto. I also made it a tail dragger. Somewhere there are pics of it, but dont know where at the moment.

One wing mostly built, need to add rib W1, cut the dihedral, and cut off the excess spar on the tip end ... mulling lessening the dihedral, and bolt-on method.

Going to get the other wing to the same state then worry about the dihedral, I'll worry the bolt-on method after I have a fuse to hold it up against.

Funny, I'm looking at doing just exactly that with mine, when I get to that point. My intention was/is to add ply inside the wing and in the fuse (front & back) for bolts. It has worked for other planes I've done, should with this one too.

My biggest problem so far is trying to decide on whether I want to go with the original tricycle gear or make her a tail-dragger. I've already got a pretty good OS .40-LA for power, planning to do the single-servo bit for ailerons. Also looking at flattening the dihedral to make her a bit "sprightlier" - thinking seriously about just 1" total.

Dave

What is your flying skill? If beginner, leave the dihedral stock, if intermediate, lessen it to 3* instead of the stock 6*. That gives a 1 1/2" dihedral. It retains some of the self correcting, but makes it easier to do more advanced maneuvers like flying upside down with little aileron input, and not fighting the controls for level flight.

Hey acdii!!! If this was for me, I've been into RC since the early 70's, CL since 1955. I'm doing the LT40 to replace my seriously-aging 3-channel Kadet Mk-1. I was actually talking about lessening it to 1" total - pretty flat. I did that with my Sr. Falcon when I built her in 1974. That wing is very nearly flat on top, only 3/4" lift when the wing's flat on a table. The Kadet Mk-1 was built with the full 6* (my first RC plane), the LT40 will be much more of a "sport" plane than a trainer.

Our posts crossed at the same time, this was in reply to CNY_Dave

I have been through a flightstar-40 trainer (DX5 power switch killed it), and am currently flying a Fokker D-VII and a kyosho 50 spitfire.

This plane is for relaxing, beating on, general un-dumb-thumbing, and such. When I start doing something stupid I figure I can get more practice in on the kadet than either of the others.

The other trainer had 6° dihedral and I didn't have a problem keeping it upside down, or my champ (but 3ch rudder action is reversed tough to go back and forth), my only reason to think about less dihedral is for rudder practice that will be more like the spitfire, although the fokker is pretty good for that as it has minimal dihedral (and it slows as fast as the spit when the spit flaps are down!).

Building the wing isn't as lengthy as I thought, how hard is getting just the kit parts for the wing (or an ARF wing?). Might be nice to have a sport wing and a trainer wing.

I'm going to keep the dowels for rubber-banding a wing on so I can easily put on other wings.