I'm planning on building the Sig LT40 this winter. I flew the Sig Kadet Senior for 2 years about 10 years ago and now I'm starting up again. I was using an OS .40 in the Senior and found it a bit lacking after a short while. I was thinking about a 4 stroke or a bigger 2 stroke in the LT 40. I want to use the biggest engine it can handle. Any advice? I also need a new radio system and am thinking of a 6 channel futaba so I can use it on more advanced craft in the future. Just to throw more questions into the mix I have an old Great Planes Trainer Forty kit, but I think with the symmetrical wing and little to no dihedral I should step back to a more basic trainer like the LT40 to get my skills back. Again any advice would be much appreciated.

OS Max .46 AX. Good, solid, and just a touch more oomph than the FX. Worth the $$$

I'm just completing the build of my LT-40 kit and went with the O.S. 46AX. From what i read here on the boards it seems the extra weight of the .46 gives the plane better "balance" then a smaller .40 plus the extra power of the .46 will keep you interested in the plane for longer. I only went with O.S. because it was recommended over the equivalent Thunder Tiger pro engine at my LHS.

If you can afford a four stroke, buy one. There's a guy at the field flying an LT40 with an OS 70 Surpass four stroke, and it'll fly with 1/4 throttle, BUT the engine will serve you well for a long time.

I'd also recommend spending the extra money for the Futaba 7C series transmitter. The Futaba 6 EXA is a decent first computer transmitter, but is lacking in some departments.

Good luck, and welcome to RCU!
Dennis-

OS46AX with a 11x5 up to a 11x7 prop. Increase the throws and seal all the control surfaces. I also eventually converted mine to a taildragger but made it so that it could be used as either setup depending on the need. Plane still flies fantastic even though I no longer own it. (I am training the person who bought it from me).

Replace the stock main and nose gear. I used Dubro super strength main gear

http://www.shopatron.com/product/pro...d=DUB789/101.0

and Fult's twin strut nose gear.

http://www2.towerhobbies.com/cgi-bin...&I=LXH124&P=ML

and ended up with tons on ground clearence. With the Fults nose gear I listed you can use the stock firewall mounts or their own if you haven't gotten that far in the kit yet.

At one point I put on an APC 12.25x3.75 prop and the plane went nuts. Lots of vertical (not unlimited) and all other maneuvers got more responsive, but throttle management was a must since this prop creates tons of pull and full throttle takeoffs were rather spirited.

This picture only shows the main gear.

3 great engine brands that I can see for the LT. Get the 46 size, better value for the dollar and bigger won't help you. Either Thunder Tiger, OS, or Evolution. All are user friendly, have good power and are easy to adjust. Get a Master Airscrew 11-5 to go with it and you have great all around performance.

I know they have had some bad press, but when I put a Tower Hobbies 46 in my LT40, life changed. Of course, I crashed a few flights later, but no fault of the engine. The TH46, when properly broken in, is one powerful 46, and mine runs great. The price was good, too.
Glen

I learned to fly with a LT40 powered with an OS 46FX. It flew beautifully with that combo. I later put an OS 52 four stroke on another LT40; and liked that even better. It gave the LT40 plenty of pull without adding too much weight. A few times I was able to trim mine out to where I could control altitude with throttle alone. Just a plain joy to fly.

I really Like K&B 48. Break-in is easy and lots of power. Made in the USA.

I use a Thunder Tiger .46 Pro and recently changed to a 12.25 X 3.75 prop and can prophang with the best of them ! With that prop, I am spinning 12,500 RPM, with the 11 x 5, it was 14,500.

Put the biggest you can afford in a .40-.52 size. The Magnum .52 from Hobby People is around a $100. Lots of people have this engine.

If you're building it then it's easy to convert to taildragger!

Mine has an OS .46AX and a 12.25x3.75 prop, since I fiberglassed the wing joint I get to have fun with it. Last night I ripped out my main gear in a very close call, I'm just lucky that it hit the ground flat. Good old disorientation/control reversal.

Honestly, it's really a .60-sized airframe, so you could go nuts with it.

I agree with the 46. I trained on my LT with a K&B 40 to start with. It flew it OK. About 8 months later I mounted a OS 46 FX on it and, oh baby! It made it an entirley different airplane! I still fly it from time to time, and have set of floats for it.

Thanks so much for all the input. Now I just have to hit the War Department up for it. What do you guys think.... a new necklace or maybe a piece of compressed coal. The tail dragger sounds fun with a 4 stroke OS 52. I'll let you know how things are going. I'm sure to have more questions soon.

Thanks again.

Stan

4 stroke? You might want to ask a little more.. Everyone was suggesting the size for a 2 stroke.. You might get different suggestions for a 4 stroke..

Was this a mistake? Would a bigger 4 stroke fit and be better? I like the sound and power of a 4 stroke but are they a lot more difficult to deal with and maintain? I had a OS 40 before and never had a moment of trouble. I'd hate to trade a cool sound for a pain in the fanny. Thanks for the thoughts.

Stan

There's really nothing more difficult about a four stroke, once I bought my first I've never even considered buying another two stroke. After a number of run hours you will need to adjust the valves, but that's a 10 minute job at most, and once the needle is set on one you usually don't have to touch it again unless there's a drastic change in weather.

I really prefer the power curve of a four stroke too. Greater thrust at lower RPM, and through the mid range to full power, whereas a two stroke develops almost all it's thrust at high RPM.

The 52 will be plenty of power for the LT, I only suggested the 70 because you'll get more use from it later on once you've moved beyond the trainer. You WILL have to use the throttle more with the 70, because it's actually way too much power for the plane.

There is one "negative" to using a four stroke, you really need to use a tachometer to acurately set "peak" on the needle valve because you can't tell by sound the way you can with a two stroke. I've set mine without a tach often enough, but just make sure that I'm well below peak.
Dennis-

I would normally disagree with DB here. I reccomend a 2 stroker for a complete newbie. It is simpler and less maintainance. But I see you have experience already. So in your case I heartilly reccomend DB's advice. A 4 stroke is a great way to go. I reccomend a Saito 72. As DB suggests you will need to use throttle management. But you should not have any problems. You can also use it in your next model or so.

As to the trainer 40, go for it. With some help from an instructor there is no reason you cannot use it. You already have experience. I am building the 60 sized one from RCM plans. I intend to use it as my way back in next spring. Money problems kept me grounded this year. I am gonna use an Irvine 61 in it. With a little buddy box time you should do just fine.

I also agree on the 7C issue. For a few dollars more you get a better radio. I think once again DB is right on the money here. The 7C will get you farther in the long run. Good luck and welcome back.

Mark Shuman

any of the motors listed here will give good service. the Tower 46.& Thunder Tiger 46 probably most bang for buck.

I have a SIG LT 40. I dropped an Evolution .46NT 2 Stroke on the plane and it flies great. It has plenty of torque and power and the engine is very responsive so far. I did notice a couple of bumps in the engine this last weekend, but I think it was a tiny bit lean. I plan to adjust it when I have a helpt to hold the tachometer. Other than that, more expierence pilots have flown it and I have too and it works great so far. I am using a 10X7 prop on it now. Pretty soon, I'll abandon that for a prop that will give me more bang. I used that prop at suggestion to slow it down until I got my air legs back again. I just started back up after a long hiatus away from RC flying. I combined that with a Futaba 6 Channel Radio.

Hope this helps.

Happy Landings,

Phil

http://www.sandhillsrcflyers.org

lairdpg, I recently tried an APC 10-7 prop on a 46 FX engine and it ran great. Then I tried an APC 11-5 and it runs fantastic!! I have more power and more speed.

I am certain you ar right. Until I get a few more flights under my skin, I intend to slow the pane down. Once I get back up to speed, I'll change the prop out. I'll try a APC11-5 on mine and let you know how it cranks. Thanks for your advice. [8D]

Happy Landings,

Phillip

Sounds good![8D]

Thank you everyone for your input. I'm still partial to the four stroke, but that will all depend on how fat my wallet feels when I buy the engine. Thanks for the prop input also. Happy flying while the weather holds.

Stan

I love the sound of the Four Stroke over the Two Stroke. They do require more maintenance than the Two Stroke, though and they are usually more expensive.

I hear thunder clouds looming overhead. Gonna get this PC shut down.

Happy landings!

Phillip
http://www.sandhillsrcflyers.org