Right thrust on twins

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Glenn Rackstraw
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Right thrust on twins

Postby Glenn Rackstraw » December 4th, 2012, 6:28 pm

I need advice from a twin expert. My friend is building a Bristol Freighter with two 26cc petrols, the original had electric power with contra rotating props and offset in one motor so not very helpful. With two petrol engines is there a need for right thrust and or downthrust?? Any advice gratefully received.

Alan Cantwell 1131
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Re: Right thrust on twins

Postby Alan Cantwell 1131 » December 4th, 2012, 8:28 pm

Here is the rply from a twin expert, there can be none better than Nick Ziroli senoir

For a tail-dragger aircraft, I set the left engine with zero offset, and I set the right engine with 3 degrees of right thrust. I came to this setup when I was fine-tuning my Beech D-18. The Paul Matt 3-views I used to design the model, showed each engine with 2 degrees of outboard thrust. As it turned out, this produced a tremendous amount of left torque. Even with full right rudder, the D-18 always turned to the left on takeoff. My zero and 3 degrees setup solved the problem nicely. The effect of left torque turning is much less of an issue with aircraft that are equipped with tricycle landing gear. I feel that this offset thrust setup also helps during an engine-out.

How much engine down thrust you need is more a matter of how the airplane flies and the model’s wing and tail-surface incidences. You can adjust this after several test flights.

FLYING TWINS

Alan Cantwell 1131
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Re: Right thrust on twins

Postby Alan Cantwell 1131 » December 4th, 2012, 8:30 pm

heres the full article, bet bossman Dave will have a bit to say on this

http://www.modelairplanenews.com/blog/2 ... -aircraft/

DAVE JOHNSON
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Re: Right thrust on twins

Postby DAVE JOHNSON » December 4th, 2012, 8:46 pm

Glenn--as Alan has posted on here,if you follow the suggestion of the article,it would be a good starting point---obviously different aircraft have differing tendencies,but most of my multis have set up as above---DAVE

Glenn Rackstraw
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Re: Right thrust on twins

Postby Glenn Rackstraw » December 5th, 2012, 7:24 pm

Many thanks to you both, your help is much appreciated.


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