carl.froehlich(at)verizon
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 Posted: Wed Mar 23, 2011 10:42 am Post subject: Optimal cowl intake and outlet areas for engine cooling air |
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Interesting note.
I'm just finishing the pretty work on a Sam James cowl and plenum. My findings to date:
- The cowl fitting was no harder than the cowl on my 8A.
- I noted the problem you had on the plenum not lining up with the cowl inlet rings. Perhaps this was fixed as my cowl and plenum lined up well.
- I also noted the cooling issues you reported and was worried. I did some measurement comparisons between the James Cowl and the stock Van's cowl and while the inlet areas are similiar, the James cowl exhaust area is much larger (same width but about an inch lower. Again perhaps this was a change from you cowl.
I'm six months away from flying so no real operating data like yours.
Carl
Sent from my mobile phone. Please read past the typos.
-----Original message-----
[quote]From: Robin Marks <robin(at)PaintTheWeb.com>
To: rv10-list(at)matronics.com
Sent: Wed, Mar 23, 2011 17:30:13 GMT+00:00
Subject: RE: RV10-List: Optimal cowl intake and outlet areas for engine cooling air
Ahhhh.. as one of the first -10 James cowl flying owners with lots of negative experiences associated with that cowl & plenum I strongly suggest that is about the worst starting place possible. As usual the factory design while not as sexy is functional and proven. I think it’s been established that the openings on the James cowl are just too small to properly cool the Lycoming 540 engine. There has been some success (I am not totally up to date) by increasing the inlet ring size from 4.5” to 6” but that is a lot of work. Imagine taking a new cowl and cutting the inlets back to then manually make transitions to new 6” inlets. Then modify the Plenum to match. Plan on significant R&D right when you want to be flying your plane. I don’t even want to go into the James Plenum that is misaligned from the factory as if they had NOOOO idea how wide their cowl inlets would be to mate to the plenum. The plenum doesn’t even comply with known design principals of smooth but ever increasing volume as the cooling air moves aft. Having owned 4 RV’s, 2 with stock cowls & baffles & 2 with plenums & James cowls I find the plenums to be a large pain in the ass. Extra weight & complexity. Reduced access with limited definable benefit.
Additionally forget about flying LOP out of the box with the James set up. While the stock cowl seems to not be an issue the James owners have a difficult time seeming to straddle a razors edge of LOP vs. poor engine performance even after exhaustive injector balancing and adding an expensive (and heavy) turbo rails & fuel injector shrouds.
Showplanes is making a valiant effort with a new cowl for the -10 that is great looking. Unfortunately it’s still a little early to that party as they do not have a production unit available for sale.
I personally will be removing my James cowl or making additional major modifications to the unit within the next 12 months. If you are building to fly head my warning.
Robin Marks
RV-4 Sold
RV-6A Sold
RV-10 220 Hours
RV-8A 4 Hours
From: owner-rv10-list-server(at)matronics.com (owner-rv10-list-server(at)matronics.com) [mailto:owner-rv10-list-server(at)matronics.com (owner-rv10-list-server(at)matronics.com)] On Behalf Of Ralph E. Capen
Sent: Wednesday, March 23, 2011 9:27 AM
To: rv10-list(at)matronics.com (rv10-list(at)matronics.com)
Subject: Re: RV10-List: Optimal cowl intake and outlet areas for engine cooling air
--> RV10-List message posted by: "Ralph E. Capen" <recapen(at)earthlink.net (recapen(at)earthlink.net)>
Considering the work that was done to develop the SamJames cowl and plenum...and how well they work - I think they're a great starting place.
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