I'm Scratch bulding a Learjet and plan on using 2 d/f the plane is going to be about 6' in legenth the fusalage will have a radius of 110mm and i have yet to scal down the wing span but my question is will 2 .46 fans be power enough or should i go all out and get 2 .91 the plane is going to have a fiberglass fuse and a wood and foam wing and elevator. plan on also having alot of scale detail like flaps and spoilers so that would add weight but again (2) .46 or (2) .91 and if you know of any d/f manufactures could you please let me know by sending a url

Thanks
Adam

Adam,
There is a big difference in output between a 46 and a 91 DF, and they are very close in price. For a plane that size I'd recommend 91's. After all that work it would be very disappointing if it wouldn't get off the ground. Better safe than sorry, and you can always throttle back.

Check out the Mark Frankel Lear at http://www.modelspecialties.com/Learjet.htm
It's a little bigger than what you have in mind and I believe that his original one flew on two OS77's.

Joe

thanks for the advice i plan on mine to be a bit bigger right now it's on papper and it doesn't seam that big but once i start making the mold i think my mind will change
Thanks
Adam

depending on the size of your learjet and weight, you could put twin Kress fans in. The rk-740

[link=http://www.kress-jets.com]www.kress-jets.com[/link]

Just a thought!

Hallo Valier:
Another consideration about .46 or .91 fan/engines is the weight of the power plants. .91 class engines are almost twice the weight of .45 class engines. That extra weight means more structure weight and large fuel tanks, more structure weight, etc.
Remember to keep it light, and carbon fibre strands in stress areas. Use proper wood types to keep it light. When in doubt use areodynamics, not ballistics.