fred685

My Feedback: (67)

I'm looking into building an Ultrasport 60 and making it a twin using two 40's. I was looking at the Duelist plans and see that has a good bit of down thrust. Is this something all twins need or is it just the Duelist?

Thanks

Bad_Daddy

The torque required to spin the prop causes a counter-torque rotation of the fuselage. Airplanes will typically mount the motors 2° down and 2° right to compensate for this.

jrf

My Feedback: (551)

Oops, sorry, have to differ with that. Down thrust is only required where the airfoils and incidence of the wing and stab are not set up for neutral lift. A trainer needs down thrust, an aerobat does not.

To answer your question, you need to set the engines of your twin at the same up or down thrust as the single engine version. In the case of the Ultrasport, that is 0 degrees.

The Ultrasport has 2 degrees right thrust in the single engine. On your twin version, you should set the left engine straight ahead. The right engine can be either 2 degrees right like the single or straight ahead to match the left. Right thrust in the right engine will make it track marginally better in the uplines and in left engine-out situations. Do not put right thrust in the left engine.

The orignal Duelist was not set up for neutral lift. It needs the downthrust to offset the positive incidence in its wing. FYI, I understand that the Duelist MK II is set up O-O and does not have the down thrust.

Jim

TCBLightning

My Feedback: (5)

Jim is correct the Mk II plans are 0-0.

I built a Pica Duellist which I think has 2+ on the wing and stab but made the engines 0 to the wing cord and it flew just fine.

Here's a pic of my current Duelly that was built from the Mk II plans.

boingram

This sounds like a great idea...keep us posted...

Bo

jaka

Hi!
No!
I have had 0,0,0 on all my twins.
Regards!
Jan K