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Chuckellis90b

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Oct 24, 2011
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17
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Moses Lake, WA
Bit of thread drift; does anyone have guidance regarding exhaust pipe clearance? I am build a 6 to 1 system for a Skybolt with bungee gear. I need some clearance to avoid heat damage of the bungee cords but I would obviously prefer not too much.
 

TFF

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Apr 28, 2010
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Location
Memphis, TN
I would keep a pretty good berth on the bungees. Too close you will end up on your face. You also want as much life because they are a pain to change, I just did some. I would go over to the Biplane forum to where there are lots of owners.
 
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mcrae0104

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Oct 27, 2009
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BJC
The engine is pretty well dressed out now...
Great looking installation. Would you mind telling us what length of prop extension you're using, and perhaps a bit about how your cowling inlets will seal to your cooling and intake plenums?
 

Toobuilder

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Jan 19, 2010
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Mojave, Ca
Thanks. No prop extension per se... This airplane (typical of Rockets) uses the extended hub Hartzell which pushes the blades forward a couple inches. With the blades in full course pitch, the prop TE is breathtakingly close to the inlets. The inlets float in front of the cowl like the Rutan Boomerang, but unlike his plan, I have a foam seal between the cowl and the back of the inlets. Zero air leakage there, and I also have a felt seal around the prop hub, so minimal leakage there.
 

Victor Bravo

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Jul 30, 2014
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KWHP, Los Angeles CA, USA
The inlets float in front of the cowl like the Rutan Boomerang, but unlike his plan, I have a foam seal between the cowl and the back of the inlets. Zero air leakage there, and I also have a felt seal around the prop hub, so minimal leakage there.
If the upper plenum is sealed to the inlet, and if the top of the plenum has a full cover over it (I see the piano hinge sections, which I presume are to hold the plenum cover), then what difference could it make to seal the inlets where they float in front of the cowling?
 

Toobuilder

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If the upper plenum is sealed to the inlet, and if the top of the plenum has a full cover over it (I see the piano hinge sections, which I presume are to hold the plenum cover), then what difference could it make to seal the inlets where they float in front of the cowling?
Because the inboard areas of the prop create a localized area of low pressure that will draw air OUT of the cowl seams. This is especially true at the spinner gap behind the blade root where this outflow, perpendicular to the airstream, creates a bunch of parasitic drag. There have been some dramatic improvements in cooling just by taping up the cowl seams near the inlets so that this outflow does not disturb the cooling inlet flow.

Additionally, my cowl outlet is augmented with exhaust flow for segments of low speed/low Q flight - I don't want to waste any of that "sucking power" with leaks going around the plenum. The inlets on this airplane are smaller in area than than my RV-8, despite having over 50% more heat load. I need all the delta P between the upper deck and lower cowl I can get, and every air molecule needs to pass through the fins.

So if the cowl leaks "out" at high Q (cruise), I get drag; if it leaks "in" at low Q/high extraction (climb), cooling suffers. Bottom line: Cowl leaks are bad for me.
 
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Toobuilder

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Happen to have any pictures of that? I've been looking at a brush or foam seal between the cowl and spinner backplate since I have the lightweight SDS flywheel too, but I'm also open to other options.
Cowl Seal.jpg

I was planning to do the "Dan Horton" style seal on the flywheel, but obviously that wont work with the ventilated SDS piece. Then I saw pictures of what Dave Anders did on his RV-4 and copied the concept (felt on prop hub). This one is not as flexible as the "horton style", but does offer significantly lower surface speed at the seal face. Dave's RV has the standard "short" Hartzell hub you probably have, so check around for pictures of his setup.
 

BJC

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Oct 7, 2013
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97FL, Florida, USA
On Saturday, I flew for some time with my son-in-law. After the flight, he checked the ADS-B integrity via the FAA site for doing so. I know, I installed it last fall, but I just recently have begun flying again. Also verified that the anonymous mode switch functioned as expected.

All was OK.


BJC
 

Doran Jaffas

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Jun 25, 2019
Messages
161
I'm looking at Aircraft Spruce and Specialty adsb out in the rear nav light.
Couple thousand dollars. For the most part I don't fly into class B anymore. And definitely not with this particular airplane. Was up to 9000 feet earlier this year and I felt like a real tiny bug!
 

bifft

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Apr 17, 2011
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275
Location
Utah
Painted the wheel pants and gear fairings. Still lots of pinholes. But at least no BB sized anymore. Good enough for a 10-yard paint job. Used up the last of my paint so I'm calling it good. From day one on this project I've said "if an error is cosmetic rather than structural it flies". So just more of the same. Just hang a "Don't Judge Me" sign on it if I ever go to a fly-in.
 

Toobuilder

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Engine run today. Started on the second blade and ran perfectly, no drama whatsoever. As expected of an engine thats had 5 hours of flogging on the Ly-Con dyno and the well scienced out SDS engine management system. Next time the engine will be run is to taxi out and fly.

 
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bifft

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Apr 17, 2011
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275
Location
Utah
Got the wheel pants and fairings mounted. Once on the plane the crappy paint with dust on it from the very dusty hangar fits right in with the crappy dust covered paint job on the rest of the plane.
Faired.jpg

In the two steps forward one step back department, when putting in the third to last screw hit the transponder antenna with my knee and it broke off. At least it's a cheap part by airplane standards. Will have to take the floor out to install the new one.
 

cblink.007

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Jul 7, 2014
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207
Location
Texas, USA
Halfway done with finishing on the testing model. Lower surface complete and ready for epoxy wiping. Today, applied dry micro all over the top surface:

20200607_140610.jpg

Now my fiance thinks I will be able to help her decorate holiday cakes...
 

gtae07

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Dec 13, 2012
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1,960
Location
Savannah, Georgia
Pulled the engine off the mount and put it back on the engine stand. Next up is starting to mount stuff to the firewall (which is why the engine had to come back off).
 
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