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Inside cowl muffler

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Inside cowl muffler

Old 01-14-2007, 04:23 PM
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HDB
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Default Inside cowl muffler

In am in the process of building the F6F HELLCAT ARF by Hanger 9. I have used 4 stroke engines in other planes which I have built with the mufflers enclosed, however this time I want to use a Webra two stroke - The large muffler will not fit without drilling a hole in the firewall and diverting the exhaust out the bottom. What other options do I have as this is my first attempt or do I go to a four stroke?
Old 01-14-2007, 04:41 PM
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KidVermin
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Default RE: Inside cowl muffler

http://www2.towerhobbies.com/cgi-bin...P?&C=GMA&V=BIS

You didn't mention the size of Webra, but you might be able to alter a Bisson Pitts muffler made for GMS,OS or ST.
Old 01-14-2007, 04:51 PM
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Default RE: Inside cowl muffler

The Webra is a Speed 61 and with the size of the cowl there is plenty of room to drill a hole in the firewall, add an extension and run it out thru the bottom of the plane. I have a bison and will look at it, but will still need an extension to run it out thru the bottom of the cowl.
Old 01-14-2007, 05:05 PM
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Default RE: Inside cowl muffler

In reference to running it out thru the bottom of my plane - would this possibly cause a heat problem since the exhaust would be exiting right below the fuel tank? Probably better to keep it in the cowl and exit at the bottome of it?
Old 01-15-2007, 01:17 AM
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Default RE: Inside cowl muffler

G'day Mate,
You will have to cut some sort of hole in the cowl to let hot air out, or you will cook your engine.
Might as well use the hole to let exhaust out as well.
Old 01-15-2007, 11:41 AM
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Default RE: Inside cowl muffler

Thanks for responding Allan, I still have the problem with the muffler. With the 2 cycle, the muffler is too long to fit within the cowl. It will fit only if I drill a hole in the firewall and run the exhaust extension(if available) out thru the bottom of the plane. I looked for an after market muffler to fit the Webra, but havn't located one yet. Any more thoughts on this?

Harvey, Florida
Old 01-16-2007, 01:02 AM
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Default RE: Inside cowl muffler

G'day Mate,
Try Emailing Bisson Mufflers, they may have a pitts style muffler, available for your motor.
This is the web page, http://www.bissonmufflers.com/en/index.html
Old 01-16-2007, 08:17 PM
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Default RE: Inside cowl muffler

Allan, thanks, I located a Pitts at the Bison site and have requested info and availablilty. Costly, but would be worth it. Looking forward to getting it in the air. Good days to you from Florida.

Harvey
Old 01-18-2007, 10:20 PM
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Default RE: Inside cowl muffler

You may also want to check out JTec http://www.jtecrc.com/ >, they also have a variety of mufflers that may work. FWIW - they will drill a muffler to fit your engine. If I remember correctly, the additional charge is minimal.
Old 01-19-2007, 10:09 AM
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Default RE: Inside cowl muffler

I've got the same deal with my H9 Thunderbolt. I plan to use an OS91FX and it's muffler is basically a 61FX muffler that's got a 1.5" extension in the middle of it. It's looonggg.

I'm going to have to put a hole in the firewall AND the next bulkhead AND make room in the belly pan that's glued to the wing.

I plan to protect the inside of the fuselage with a tube that runs from the firewall hole to the bulkhead hole. I figure to use cardboard tube, like from inside a roll of toiletpaper. It's light and a coat of finishing resin will make it fuelproof. The diameter isn't quite enough, but that's easily taken care of.

The muffler will have to be sealed from the inside of the fuselage for sure. They always leak.

I'm not worried about the heat. Given at least 1/4" clearance all around the muffler and the air flowing through ought to be enough. And I'll probably have a layer of glass cloth around the toiletpaper tube.
Old 01-19-2007, 10:14 AM
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Default RE: Inside cowl muffler

BTW, pink foam insulation from a home improvement warehouse is also a great material for this application. Blue foam insulation is the same stuff. whatever........

It's absolutely easy to use. I've considered "boxing" instead of "tubing" my muffler tunnel. The foam would box it off perfectly. And might be easier to create than a tube.

I've used the stuff inside cowls as baffles since discovering how easy it is to use. And how much space it can fill. And that it coats with surfacing resin to be completely fuelproof. And that strengthens it if that's needed.

And darned if it doesn't insulate too. amazing........
Old 01-28-2007, 03:13 PM
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Default RE: Inside cowl muffler

Thanks da Rock, I have ordered a Bison Pitts that I hope will do the job, will have to see how long it takes to arrive. Understand that sometimes they are not too expedient.

Thanks everyone for the words of assistance. I have a new problem on the forum under Enya Parts. Help !!

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