I am putting a .40 OS on a Seagull Arising Star trainer, I have heard you should mount the engine off centered, a little bit to the right, to counter the rotation of the prop. Is this true?(it is when building a Vans RV-4) And if so do you mount it to the right when standing behind(its right) or in front(its left) of the model?
Thanks

In general right thrust is good, it helps counter engine tork… you view right thrust from behind the engine, crankshaft will point to the right. Normally just 2 or 3 degrees is enough, some planes may need more some none at all. I’m not familiar with your plane but some trainers have the right thrust built into the fire wall. Mount the engine straight have someone fly/trim it out for you…any good pilot can tell you if you need right thrust down thrust and so on... it's easy to add it later...not having it will not keep the plane from flying.


John

thanks John thats a great answer and fast 2

Jeff_Bubba,
Just so you fully understand, it's not the off center mounting of the engine that creates the right thrust. The firewall must be slightly angled or you'll need to add shims under the left side of the engine mount to achieve right thrust. The reason for mounting the engine to the left of center, (pilot's left) is to get the spinner backplate on the thrust line (center) of the airplane. As stated, most planes require right thrust but some do not.

Jeff, I am still flying my 2nd Arising Star (Irvine .46MkIII). Just stick your engine on the installed mount, you will not have any problems with it

I'll second what Merlin said. Mount the engine acording to the instructions. If the designers wanted right thrust on the engine, they would have designed it into the plans.

I have never had to worry about right thrust until I started using 60 size or larger engines. Its not usually an issue on 40 size trainers. [8D]