gmata007

Hi im building a .60 P-51D Mustang, im installing the engine Cowl im mounting the engine sideways, i need to cut, a hole in the cowl, and body know any good techniques to cut a fiber glass cowl, and how do i mark exactly where to make the holes for the head and for the exaust?

thanKs

gmata007

Any techniques to cut fiberglass cowl? and how to know where to make the holes? for the engine and exaust.

pettit

My Feedback: (23)

I'm sure someone has nifty graphics showing this way, but here it is in words:

Mount engine and muffler in final resting place. Using file folder or similar cardboard, make a template that attaches to the fuselage behind the place where the back of the cowl is going to be located. Fasten this cardboard securely at the rear end with masking or other tape. It has to at least be larger than the engine cylinder head and muffler.

Trace around the cylinder head and muffler onto the cardboard with a pen or pencil. Cut out what you just drew with scissors. These are the holes you need to cut in the cowl.

Remove the engine and install the cowl with the template outside the cowl. Tape the front of the template into place and trace through the template holes onto the cowl. This is what you need to cut away. You'll need to do a lot of trimming and fitting, and a drum sander on your rotary tool does fine for this.

I use those "RotoZip" drill-like bits (used to cut holes in sheetrock) to cut fiberglass parts, but I run them in my high speed rotary tool.

Do this outside since fiberglass duct is really nasty stuff.

Flytoolow

My Feedback: (17)

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

mcarleno

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).