bchapman

What do you guys think of putting a OS 35AX on a PT-40. This plane was built by myself and my 8 year old son. I fly RC all the time, but this is his first model. I don't really want to add the extra weight of using the 46AX and this model in my opinion doesn't need a high performance 46 on the front as I think it would be way overpowered. What do you think?

Thanks

mike109

G'day

I think it will be fine. I built a PT-40 many years ago and it was powered by a Thunder Tiger GP 40 which would have been no more powerful than the AX 35 and it was fine. You are doing the right thing keeping it light.

The LT 40 is a floater like the Sig Kadet Senior (my favourite plane). I have powered various Kadets with a range of engines from an extremely asthmatic and old OS FS 40 four stroke to quite large four strokes and the less powerful ones always fly well.

More recently I powered a Sig LT-40 trainer with an Enya 40SS plain bearing engine. I was told here that it would not be powerful enough. It was perfect.

There is a contributor here called JohnBuckner. He has a Sig Kadet Senior ARF - a much larger plane than your PT-40 - which is flying on an AX 35 with great success.

We overpower most of our models these days because it is easy to do so. Yours will be just great.

Cheers

Mike in Oz

Gray Beard

My Feedback: (-1)

It's got more power then the old LA 40s people used, I see no problems at all.

flyhigh2

I fly a PT 40 with a OS 40 LA and it does just ffine. You may have to be a bit conservative on take but it really is enough engine.

bchapman

Thanks everyone!

I was thinking that it would be enough power as well (especially for an 8 year old) considering the size of the plane. He still over-controls when I buddy box him with my old trainer, so I thought the 35 would be perfect and would keep the weight down. He wanted to build it with the wing that had the most dihedral and had rubber bands because he read in the manual that is what they recommended (smart kid.) I'm going to set it up with just the rudder for now as he isn't really ready for the ailerons and rudder together anyway.

Brian

jetmech05

sorry i disagree....speed and altitude are life...the quicker you get speed and altitude the better..throttle is not an on off switch....better to have the power and not need it than to need it and not have it....good flying to you both

Scirocco14

I think the 35AX will be just fine on the PT-40. It'll teach your son to fly the plane on the wing and not the prop. As long as you're careful with your build weight, you'll be fine IMHO.

I'm not a proponent of overpowering planes. I've had a Goldberg Anniversary Cub w/ an OS 48 Surpass which flew very nicely and scale and had enough power to do scale-like aerobatics. Some of the other club members refused to believe it was just an 48 until I pulled the cowl off and showed them. Flew it for 3 years and that plane taught me more about flying than all the other planes I have combined, including the trainers I started with.

I also have 40 size sports planes flying on "puny" OS 40FP engines: Ultra Sport 40 and 4*Star 40. Again, the "overpower the plane" crowd said they'd be dogs. Guess what, they fly beautifully on those engines! Plenty fast and very nicely balanced.

Have fun with your son flying the PT-40!

Mark

JohnBuckner

My Feedback: (1)

Unless you were dealing with a high altitude location, say somewhere around 5000 foot density altitudes which I don,t beleve you are then the remarkable little .35AX will work very well indeed in your PT-40. Its a perfect match for that airplane.

I use the .35AX in my most active airplane a Senior Kaydet Which I use for training folks with. Although that is smaller than the normally suggested minimum .40 my airplane routinely outperforms many of the others useing much larger engines.

Here is some video of it flying in its original colors and the reason I had to recover the thing after I flew it for one of our events:

http://www.youtube.com/watch?v=rOEQl...PcXnWA&index=2

John

DavidAgar

My Feedback: (108)

I agree, the 35 will be just fine. Good Luck, Dave

bchapman

Thanks for the advice and I really liked the video of you Kadet Senior. I forgot how big those things were and how slow you could fly them. I remember them from the 80s at the field as a kid myself. I never build one, but I always loved the Sig kits and built quite a few over the years growing up in Iowa. I think I'll order one for myself now that you've reminded me. Thanks for the memories. Brian

JohnBuckner

My Feedback: (1)

Your welcome Brian.

The picture with the two Kadet wings shows my latest new wing that I am calling the Catalina Wing, it has almost ten inchs greater wingspan and it recently was tested on my PaintBall Wizard airframe lifting eight pounds in deadweight sandbags taped on.

It worked well without excessive takeoff run and flew with complete control. For this project I switched the .35AX out for a .65 AX.


John