G'day

The Sig LT 40 is well known and loved but it slightly smaller brother, the LT-25 is a really excellent trainer too. It is smaller than all the other Sig Kadets apart from the Kadet Mk II but at 62 inches wingspan, it is hardly small. It builds easily to a light trainer which only needs a 25 size engine.

I flew my old and battered LT-25 yesterday and it was great. It was built in 2007 and initially had a Magnum 30 four stroke which suited it perfectly. I sold it to a friend who was in the "learning to land" stage of his career and he managed to break it several times (mostly wingtips from cartwheels) and we just kept repairing it. Eventually, once he had mastered the basics of landing, I bought it back and retired it. It was a bit sad with its landing gear ripped out (again) and it sat for several years gathering dust.

And then about two weeks ago I decided to fly it again. I cut a new undercarriage mounting plate from 1/4 inch ply, partially re-sheeted the bottom of the fuse then covered the patch with a small Solatex patch. The fuse of the model is covered in Sig Coverall which is doped on and then coloured with Sig coloured dope. (I used this plane as a test for Coverall and it has worked well as it is easy to repair and then re-paint after prangs.)

I have a new ASP 30 four stroke and was going to use it but then I remembered we had put a series of different motors in it and the current engine mount is too large for the little 30. What to put in it? Eventually I landed on an ancient, but still excellent, OS FS 40. This particular engine is probably over 30 years old. It recently had new bearings and a new ring and is fighting fit and even better it fitted easily.

So yesterday, in quite windy conditions, it had its latest maiden flight with the little OS purring away. (It is extremely quiet. I have electrics that make more noise.) The little four stroke is perfect in it. Plenty of power to gain some height and then back to half to putter around or do rolls and loops. The small LT is a tail dragger (steerable) but its take off is easy. It is also an excellent kit for a beginner builder as the instructions and plans are excellent. It also builds quite quickly and as our experiences show, it is tough and easy to repair. Just the combination a beginner needs. With a smaller engine, it is also very light on fuel.

A 25 size engine is all it needs and my old OS 40FS is about as powerful as a sport 25 two stroke. At one stage we ran out of engines and I put a 46 Leo in it. We ran it on FAI (no nitro) fuel and even then, we did not go above half throttle but it files better with less power and a lighter motor.

So if you are looking for a really good trainer, the LT-25 is well worth your consideration. I am glad I got mine back into the air.

Mike from Oz

I agree. I had one and sold it - I wish I hadn't. Mine had an OS FP .25 and flew great. One thing that helped with the landing gear is to substitute nylon screws for the metal screws supplied (same gauge). It is a lot easier to dig out a broken nylon screw than to re-glue the wood under the landing gear back to the plane.

I'm an experienced RC builder and pilot that when wanted a trainer for the grandchildren chose the LT-25 and couldn't agree more with your claims that the LT-25 makes a good choice. Ours is equipped with a Saito .30.

Flies slow, thus gives more reaction time.

All balsa construction, thus is easy to repair.

Is a kit build, thus gives pride of building as well as knowledge of the air frame.

No cowl, canopy or wheel pants, thus is a simple air frame without the headaches that come with those things.

Wings mounted with rubber bands, thus forgiving of catching a wing tip.

I have been watching youtube videos on the LT-25 and am considering buying one. My local HS has one for $80-90 IIRC. I have a new in the box Magnum 25 and an almost new thunder tiger gp 40 and haven't figured out which one to use. I don't need a trainer. I am way past that but just enjoy slow, easy flying models. I like to sit on the tailgate of my truck and just watch the plane putt around the sky.

Twoof my favorite planes were the two Senoritas I used to own. Both had FP 25s in them. They would fly with just a couple of clicks of thottle past idle. Trimmed properly you could fly with just rudder at low speed. I hope the LT 25 will be the same. Someone made a post here onRCUabout their LT25 and they added an FP 40 and said it was their favorite plane to fly.

My suggestion would be the Magnum 25. It is what Sig recommends. I've flown mine with two different engines, a very old Enya .29 and a Saito .30. Not a lot of difference between the anemic old Enya and the Saito .30 except the Enya was noisy and the Saito is quiet and the Enya went through a lot more fuel leaving much more oil residue on the plane. Both pulled the plane without problem. A friend had one with a hot OS 32 and it was much faster than mine, so it depends on how fast you wish to fly. You can be assured that a .25 will adequately power it for all but someone with a need for speed.

The LT-25 is very light and has plenty of wing area so it flies on the wing and doesn't require going fast.

The LT-25 is probably one of the easiest to build kits ever on the market, even if you have never glued anything together. Best of all, it is an all balsa design, with that dreaded "lite-Ply" limited to the hatch over the fuel tank.

I decided to build one a few years ago to introduce people to RC flying, since I was not satisfied with the set-ups of most of the trainers that people have loaned me to fly in this role. Currently, it is all framed up waiting for covering, but I have always enjoyed framing up models more than the sanding and finishing.

My only suggestion in the building is to lightly sand the nubs off the laser cut parts before gluing into the structure. The nubs are where they leave the part connected to the sheet during the cutting. Do that minor sanding touch-up and everything fits perfectly.

I loved mine, (sold it later) looking for an airframe for a tired Saito 45 I aquired.
I couldn't bring myself to cutting off 3" of all the wing stock. I simply cut an extra rib for each wing panel, 36" per side. Cut the trailing stock to make flaps. What a hoot!
Eventually scratch building a new fuse, to try my hand at electric power. A real great conversion, again. Flying electric off ski's here in Alberta, my flying buddy had to have it! Now I will have to replace it. It will be great for my upcoming grandson's.

Hope this helps.

-Snuts-

Thanks for the quick replies guys. And also the tip on sanding the nubs. I have built to the best of my memory over 40 planes since I started RC in about 1979. That doesn't count count control line planes. I have scratch built several planes. I carried a couple of bashed Senioritas and a scratch built Pietenpol to the old Small Steps fly in and I am sure Randy Randolf put them in one of his articles but I never saw whitch one. He had me fill out a page of details on the mods I had made.So building it shouldn't be a problem.

And I prefer planes that fly one the wing and not the prop. I like to just watch a model cruise around the sky. I have also seen several vids of these flying off the snow. Thats cool. Here in TX we don't get enough snow to do that. It sure looks like fun though. If I pick up the kit I will let you all know.

Here is a pic of the Pietenpol. This is a picture of a picture so the image aint that hot.

One suggestion for you to consider is to reduce the stock dihedral by about half. The one fault of the LT-25 is that because it is light and has generous dihedral it is a handful to land in any crosswind. Given that you are an experienced pilot, you don't need as much dihedral for righting stability and would gain more ease of control during cross wind landings.

Thanks AA. I planned on doing that. I may also increase the stab incidence and give it a tiny bit more down thrust since several post have said it tends to zoom up when going to full throttle. Those folks also used bigger engines so with a .25 that may not be an issue. But Ithink that Magnun 25 pulls about as well as the TT GP 40. Thats the one downside to a flat bottomed wing. But I sure like the lift and slow landing speed.

I built an Air Cruiser 25 from Bridi Planes and made the wing longer as suggested for electric flight and I think you could walk along beside that plane as it lands. It also has a flat bottomed wing.Here is a link to the air cruiser and I will include a picture of my version.

http://www.bridiairplanes.com/hangar/aircruiser25.html