On my 80" BUSA Citabria Pro, the plans call for 1 Dgeree of Engine downthrust. But, many who have built it say it flies much better with 2-3 deg of downthrust.

I have installed an Enya 155R 4c, and had 0 degrees to start with. It of course flew as if it needs downthrust, so I have added the following....

Under the top mount bolts, I installed two 1/16" thick washers between the mount and firewall, and it definitely has downthrust now.

>Make sure the washers are not going to compress into the firewall. I prefer
>to use them under the mounting lugs of the engine.

But, I am wondering exactly how much? I appears to be a good 2-3 degrees, but I have now way of really measuring exactly, so I was wondering what you all thought from your experiences of adding washers to attain an angle.

>The GP Laser Incedence meter will also measure down/side thrust.

How much does it generally end up with when doing this?

>I am more concerned with how the plane flies, than with how
>many degrees of down/side thrust I have. I use the amounts indicated
>on the plans as a STARTING POINT and go from there. I have had no
>problems using washers for shims.