I'm new to jets so please bare with me.
I've picked up a F-15 Sport Eagle made by Sunset
Models which I understand is no longer around.
It is a balsa / ply kit.
Wingspan 42.5
weight 7 lb
Engine 45 -77 DF
Fan Turbax 1 - 111
My question is what would be a better motor for this jet? I live in Colorado which has high elevation. Would a Rossi 53 or Jett 50 be enough
power for this jet? Any help will be welcome.

Hello latinowl. It sounds to me like a K&B .48 with a Turbax III fan unit would be perfect. I'm not, however, to familiar with the smaller DF models so make sure you get a second opinion. You can contact Jet Hanger Hobbies (Hawaiian Gardens, Ca. I believe) for more info.

Hope this helps at least a little.

Spencer Maze
CRCJA

Thank You Spencer! It's a start.

You could get a used Rossi65,81,OS77,91 or K&B 82 with A Dynamax fan and just run the engine rich and it will last longer and they are just as cheap in the long run and you can get the parts all over the place.The little engines are fine don't get me wrong but the biger ones with the Dynamax will help you get off the ground faster and they are the same size as the Turbax fan.You will only gain A pound in weight and the thrust will go from 6 or 7 lb's to ten lb's.It's goin to be your decision on what you would like.A turbax 111 fan is the same as the 45 fan with a biger motor mount,to me it does not make very much sense.I know of people that has A Turbax111 fan that put a turned down Dynamax rotor in it with a old OS 65 and they last A lot longer becouse of the rpm's.Somthing to think about.Take care-Mac

You might want to try either the K&B 48 (if you can find one) or the OS 46 VXDF with the turbax 1 fan unit. More power doesn't always translate into better flight characteristics. With the .45 class of engine in such a light plane you will get nice long flight times and the lighter the plane is the better it will fly in the thin air. Also, check out the Weston UK mini tuned pipe if you get teh OS engine. This pipe is good for another 200-300 rpm.

I built one of these a few years back. I modified it to take a Dynamax fan and an OS.77. It had spring air retracts. Dry weight was 9.5#. It performed very well. But I always wonderered what the performance would have been like with a Turbax and OS.46 or K&B.45. It would have been a pound or so lighter, which would have improved the wing loading. Ivan Muninghoff scratch built a similar sized F-15 and he used the Turbax sized fan with great success and he is from Colorado also.

Thank you Macgyver and also MMallory
All three post are helpful
Nelson

Thanks grbaker
I'll check with him also.