On certificated engines; propellers bolt directly to the engine regardless if reduction gearing is used or not. Aircraft engines are designed for optimum power where the propeller will also turn at an efficient rpm. Auto engines on the other hand are designed for a completely different set of parameters.
The auto engine turns at an rpm too high for most propeller applications. What homebuilders have done to solve this dilemma is create a reduction unit to make the auto engine usable on aircraft. So you understand how this works here is an example. If you have a 2 to 1 (2-1) reduction unit it will change 6,000 rpm at the engine to 3,000 rpm at the propeller. These numbers are a bit high for practicality but you get the idea.
Fortunately you can normally get the reduction unit from those who sell aircraft auto conversion engines. Vesta can even make a custom reduction unit if you need a custom application.
It's time to recap where we are in out virtual build.
The airframe and a good portion of the major components are in position. The instrument panel is either still being worked on or ready to install if not already. The lighting has been completed. We have either ordered all our powerplant components or just installed them according to the instructions and when it's time for break in we will follow those instructions as well. This has been an educating, at times stressful and frustrating and joyful project.
As you wrap up your checks, electrical goodies and powerplant installation and start the break in process; you will hopefully have a bit more available time. I know you have been saving all those reference materials, papers and pictures for certification so let's make sure we have some things in order with our Aircraft Forms and Records to get us prepared for our inspection and first flight.