Posted by dannparks on Monday, October 29, 2012 @ 11:48 PM:
The mufflers are the most "experimental" item on this rebuild and they've been going through some changes as the engine has been running and testing. The original muffler had a 12" long canister, and although it was quiet, It was really long and needed a support that would dampen vibration and mount onto the fuselage. I never really figured out a mount system, and I didn't really want to drill big holes in the fuselage. So, I'm trying a new design that is shorter and lighter, and doesn't need a mount.
The new design uses a 4.5" carbonfiber canister and an end cap called a SuperTrapp (used in high-performance motorcycle mufflers) with disks that send the exhaust out radially. They weigh about half what the others did (a pound each), and are almost as quiet. Definitely a different look for a Fournier. We'll see how they work when flight testing starts in the Spring. The adventure continues...
[Edit by dannparks on Tuesday, October 30, 2012 @ 01:45 AM]
[Edit by dannparks on Tuesday, October 30, 2012 @ 01:46 AM]
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Dann Parks • RF4D #4051 N2188 • now flying!
Pictures at: https://picasaweb.google.com/111628310900713778468/RF4D_N2188?noredirect=1
Posted by Donald on Tuesday, October 30, 2012 @ 02:59 AM:
Wow. Nice looking mufflers, Dan.
Posted by Jorgen on Wednesday, October 31, 2012 @ 03:02 PM:
I agree,
they look neat! I also agree it could be a problem with a long muffler since exhaust fatigue cracks are a Fournier problem and increasing the lever of the vibrating segment might exacerbate that problem. It's very inspiring to follow your development Dann, I still think mufflers on RF 4s is a really good idea!
May the 4's be with you/ Jörgen
Posted by Bob Grimstead on Friday, November 2, 2012 @ 08:30 AM:
Dann,
Nice looking mufflers, but do be careful.
The side exits from the cowlings are each approximately one third of the total engine cooling air exits (the other third is at the bottom).
If you block the two side ones like this, you might soon cook your lovely new engine.
Yours, Bob
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Flying and displaying Fournier RF4Ds VH-HDO and G-AWGN, building replica RF6B G-RFGB and custodian of RF6B prototype F-BPXV
Posted by dannparks on Friday, November 2, 2012 @ 02:14 PM:
Good observation, Bob. I cut the openings to allow some airflow, but they may need to be larger. The Eugenio cowl has an enlarged outlet on the bottom, so that should help, and I was very careful to get heads with large air passages (another thread) for best heat transfer. I have CHT on both sides and will watch carefully during first flights.
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Dann Parks • RF4D #4051 N2188 • now flying!
Pictures at: https://picasaweb.google.com/111628310900713778468/RF4D_N2188?noredirect=1
