ORIGINAL: Flytoolow
Its a long process:
- mount engine.
- make a cardboard / paper template, STRAIGHT off of the fuselage, of where the head is, carb is, exhaust, thrust washer is <-thats important to get so you have enough clearance for your spinner.
- make sure you mark where you started all the measurements from on the plane and cardboard / paper.
- remove engine.
- mount cowl a little behind where the thrust washer would be located.
- using the marks you made on the template and fuselage, mark the cowl.
- remove cowl.
- using a small drill bit, drill into center of !QUOT!engine head area.!QUOT!
- don't cut to you lines yet, mount engine and test fit, trim as needed.
- a dremel works the best to open and clean the hole.
- just take your time and it will come out good.
good luck
Ron
This is the exact process. For the engine head, I usually cut the holes with my dremel but with a diameter starting at 1/4" less than I have marked (1/8th all of the way around the circumference). Maybe its just me, but I alway find a little variance from the template. Low and slow openning the hole for the head.
The most import of all of the steps is the last one -- just take your time and it will come out good.
The only thing I will add is with the tool. A rotory tool is your best choice. Fiberglass is sanded with a rotory tool with the right sanding head.
- Use the biggest round sanding head that you can for the hole. This will minimize and irregularities.
- Make sure you are sanding the fiberglass, not melting it.
-- Fiberglass sand best with a coarse on low speed.
- Leave about a 1/64--1/32 to do a final with a medium then a fine (or hand sand the cut-outs).