Question: Cutting a muffler hole in a cowl - RCCanada - Canada Radio Controlled Hobby Forum
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Old 12-26-2004, 07:15 PM   #1
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Question: Cutting a muffler hole in a cowl

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I need to cut a hole in the side of a cowl for a muffler to stick out. Well, actually not the muffler but the side of it. The "exhaust" hole--stinger-- is not a problem.

Is there an easy way to guesstimate where to cut? I can't slip the cowl on (properly) and mark inside where to cut. You almost have to put it on off-center and sort of guess where it is from the outside and when you cut (with dremel), guess where the edge of the muffler is going to be when the muffler is properly installed.

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Old 12-26-2004, 07:32 PM   #2
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I am: Bob D.
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Mark a line where the back end of your cowl fits on your fuse (muffler side) (take off the muffler/engine first if it's in the way). You can use a piece of masking tape to make this line. Make a 90 degree perpendicular line with another piece of tape over the first at roughly .5 - 1 " above the height of where the muffler would be. Mark the cowl with a matching perpendicular piece of tape (even with the second piece on the fuse, going back to front.)

Cut a straight 2-3 inch wide by 8 inches length piece of cardboard. Try to get the corners 90 degrees for best work.

Now take off the cowl and put the engine on w/muffler. Line the piece of cardboard up with the two tape lines on the fuse (even with the up/down piece and parallel to the back to front piece. Ideally let it run even across the top of the back/front piece. and use a marker to mark the cardboard where the muffler will go. Try not to bend the cardboard

Now all you have to do is cut out the hole in the cardboard where the muffler will go. If you make a mistake, just cut another piece of cardboard and keep adjusting until it fits perfectly around your muffler with sufficient clearance.

Once you are satisfied (use lots of cardboard if you need to as it's cheap), then line the piece of cardboard up to the back edge of the cowl and even with the 90 degree perpendicular tape on the cowl itself. Now all you have to do is trace the hole you cut in the cardboard onto the cowl and cut away.

Of course it's best to take your time but this method does actually work. There are probably other ways but I found this one to be quite easy. If I wasn't clear, please just let me know, it's actually easier to do than to describe.

Bob D.
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Member of MAAC since I joined

Lighten Up, Life is waaaaaayyyy too short
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Old 12-26-2004, 08:20 PM   #3
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Certainly seems clear Bob. Least ways, it will be when I read it with a clear head in the morning

I'll be able to follow those instructions no problem.

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Old 12-26-2004, 09:08 PM   #4
Wayne MIller
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Cutting Cowl


The following works well if the engine exhaust port parallel to the fuselage (not angled):
1. Remove the muffler
2. Cut a strip of paper about 1 inch high and about 6 inches long (or whatever length is needed).
3. With the cowl on, tack the end of the paper onto the fuselage about inch before the cowl with masking tape. Make sure the masking tape is not partially on the cowl.
4. Take the cowl off.
5. Stretch the paper to the exhaust port and lay the paper on the exhaust port. Outline the exhaust port on the paper with a pencil.
6. Hold the paper away from the engine and reinstall the cowl.
7. Now lay the paper on the cowl. The pencil marking on the paper will line up where the exhaust port was.
8. You can trace the outline onto the cowl with carbon copy paper, or even cut out the traced hole in the paper to mark the cowl.

Note: you may have to enlarge the hole if the muffler extension that goes through the cowl, is bigger than the exhaust port.

I hope this helps.


Wayne Miller
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