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05-11-2008, 09:16 AM
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Join Date: May 2008
Location: Logandale NV
Posts: 45
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Why I posted
Randy,
Your website and experience is one of the reasons why I posted this thread. So the plenum can be retro fitted to the stock cowl. Are is there any pics put there? Speed is always attractive but I'm wondering more about cooling. I live in the desert. That is why I'm asking the question
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05-11-2008, 09:25 AM
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moderator
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Join Date: Dec 2004
Location: Mill Creek, WA
Posts: 617
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Quote:
Originally Posted by N23J
Randy,
Your website and experience is one of the reasons why I posted this thread. So the plenum can be retro fitted to the stock cowl. Are is there any pics put there? Speed is always attractive but I'm wondering more about cooling. I live in the desert. That is why I'm asking the question
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My RV-8 cooled adequately, but just adequately. I live the northwest where it is relatively cool so it was only a problem during the peak of the summer or when travelling in hot climates.
The whole thing behind the James cowl and plenum is to flow less air through the cooling system but try to make more efficient use of it. Cooling drag is a significant portion of overall drag, 25-20%. Somewhere this is a calculation of the inlet area of the James cowl versus Van's and I can't remember the difference, but the James cowl is a fair amount less.
When I got into a high/hot situation I had to manage climbs by turning my LASAR off and/or doing step climbs to keep CHT and oil temps down. Once level I never had a problem.
My RV-3 has no such problems and it's nice not to have to deal with it under almost any condition. IMHO if the James cowl/plenum does provide any speed increase it is very small at best. Is it worth the extra hassle? That's for each builder to decide.
__________________
Randy Lervold
RV-12iS, empennage/tailcone complete, wings currently, fuse in box
RV-3B, first flight 2007 - sold
RV-8, first flight 2001 - sold
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05-11-2008, 09:45 AM
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Join Date: Feb 2006
Location: Grand Prairie, Texas
Posts: 232
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No extension
I am building an RV8, and am getting the Sam James cowl. I already have the plenum. I was told that the new model SJ cowl does not require a prop extension.
__________________
Mike Gray, A&P IA, AET, KGPM, Grand Prairie, Texas
1956 Bonanza for sale.
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05-11-2008, 09:50 AM
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Join Date: Sep 2006
Location: Bozeman, Montana
Posts: 858
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You Can Build Your Own Plenum
You can build your plenum, just trim the baffling down, and lay up some fiberglass over it...
Something like the one showed here:
http://www.blueskyaviation.net/plenum.html
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05-11-2008, 04:39 PM
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Join Date: Jun 2006
Location: Ohio
Posts: 1,686
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Quote:
Originally Posted by tcone1
I opted to go half way. I've got the Sam James plenum but only added the SJ rings to the stock cowl, so no prop extention required. I love the looks of the resulting cowl. I also love the performance. I am regularly running down 200 horse 6's and 7's. My XP-360 is only supposed to be 180 horses, but the combination I've got seems faster than stock.
Would I do it again...yes just like last time, only it wouldn't take as long because I no longer fear ripping into perfectly good fiberglass pieces.
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Tim,
Do you have any pictures you could share?
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05-11-2008, 06:53 PM
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Join Date: May 2008
Location: Logandale NV
Posts: 45
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Way to go Mike
Quote:
Originally Posted by mikegraycmg
I am building an RV8, and am getting the Sam James cowl. I already have the plenum. I was told that the new model SJ cowl does not require a prop extension.
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I have to look into that I really don't think want to do the prop ext. Way to go on your 8 
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05-12-2008, 08:28 AM
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Join Date: Mar 2005
Posts: 337
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Love the Sam James! Love the look!
N23J,
I have a Sam James on both my flying -6 and on my -4 Fastback I'm building. I have 1,000 hours on my -6 with both plenum and cowl and no problems noted, flying out of 'hot' TX, NM and AZ with no unmanageable heat issues. Fly all recreational aerobatics and think, besides any promised speed gains, the look is very, very nice, in my opinion.
My -4 will not have the plenum.... My father in law finished his Super -8 without the plenum and is also not having cooling issues so wanted to avoid the hassle this time of the plenum. We'll see. Sam James thinks I will lose some speed without it...
I agree with the previous poster concerning aerobatics in the RV series. If someone is concerned about the 'limits' a prop extension puts on their RV, they may be interested in looking at a more aerobatic capable steed. I personally own a YAK 50 for body punishing feats and relegate my RVs to gentleman acro, rarely exceeding 3-4 Gs in all maneuvers. Do I feel i can't do 6 g's if needed? No, but can really not see a need, in MY situation.
BTW, love the N#. I tried to get that one as well as some others but finally settled on N234JJ, got the 23 and J in there at least!
__________________
Jj
Eagles Nest, TX
Built and FLYING RV-4 Fastback!
SOLD RV-6/RV-8/Rocket
Retired USAF, Current Boeing Driver
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05-12-2008, 11:42 AM
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Join Date: Mar 2005
Location: Olathe, KS
Posts: 374
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My Two Cents
I have the SJ cowl on my 7A. It IS more work to install and the plans leave quite a bit to be desired, but I would definitely do it again.
It looks 10X better, and the speed increase is reported to be significant. It always surprises me that people will pay $10K more for a 200 hp engine (vs a 180), but they shy away from the SJ cowl do to the work.
I do have a prop ext. on mine, and I am OK with it. Take a quick look at a Velocity ot Long-EZ to see what a real prop extension looks like, and the mild 2.25 or 4 inch extensions that the SJ require are pretty minimal. Additionally, the real engine experts I talked to (Mahlon, Bart, etc.) didn't seem to think a 4" extension was really a problem.
Just my two cents...
Scott
7A
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05-12-2008, 01:20 PM
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Join Date: Jun 2005
Location: Eastvale, CA
Posts: 378
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Still need the ext
In lieu of this discussion, and my desire to use the SJ cowl, I did due diligence and followed up with a call to James Aircraft and spoke with Will James. According to him, the SJ cowl for the RV-8 DOES require a prop extension, unless you are using an M hub. C hubs require 2.5", fixed pitch require 4".
I have also called my closest lycoming distributor, BPE, Whirlwind, and American Propeller regarding the aerobatic limitation. Will James had the most information and stated that the 3.5G limitation is due to a statement issued by Lycoming and Hartzell and applies to that combination. No data exists for wooden or composite props. All parties said they have no data regarding a specific issue, but that while wooden and composite propellers weight significantly less, the concern is mitigated to some extent. However the 3.5G limitation would supply enough safety factor. Again, nothing in writing one way or the other regarding wooden and / or composite props.
They also said that if building a true hard aerobatic airplane, a prop extension should not be used, and neither should an RV. Gentleman aerobatics can all be performed at or below 3.5G unless you really screw up.
hope this helps,
Bart
Quote:
Originally Posted by N23J
I have to look into that I really don't think want to do the prop ext. Way to go on your 8 
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Quote:
Originally Posted by mikegraycmg
I am building an RV8, and am getting the Sam James cowl. I already have the plenum. I was told that the new model SJ cowl does not require a prop extension.
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__________________
Bart Filipiak
Eastvale, CA
RV-8 N74VB
Barrett IO-390
WW200RV
FLYING!!!!!!!
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05-13-2008, 11:13 AM
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Join Date: Mar 2006
Posts: 86
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SJ w/ no prop extension
Quote:
Originally Posted by vmirv8bldr
In lieu of this discussion, and my desire to use the SJ cowl, I did due diligence and followed up with a call to James Aircraft and spoke with Will James. According to him, the SJ cowl for the RV-8 DOES require a prop extension, unless you are using an M hub. C hubs require 2.5", fixed pitch require 4".
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2 years ago at OSH, I spoke with Michael Quatacker out of Porterville CA, he used the SJ cowl on his -8 and did not use a prop extension. He said the just trimmed off the back of the cowl to mate properly with the firewall area. He said it was a really tight fit, and had to do some mods to his alternator mounting, but it can be done without a prop extension. Here is a pic of his plane. -Brad
http://img236.imageshack.us/my.php?image=img1694un5.jpg
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