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N23J

Member
I've been looking at different websites and there seem to be deferent views(as usual) on the Sam James cowl being worth the effort. Vans doesn't recommend doing anything but build the stock plan. I assume if I do the baffles correctly cylinders will stay cool. I have also been told by other builders that any time you make a small change in the plan or add something it always effects other stuff in the kit and takes tons more time than you think it will. I have to admit the cowl looks nice!
Alan
 
I would do it again

Your post seems to be a request for feedback. Yes, it may cause more work, but in the case of the cowl, not much IMHO. If you go with the cowl, go with the plenum, too. I believe it's a drag saver and that it improves cooling. I won't take the space to argue it here, but I firmly believe it's true, Van's NIH reaction notwithstanding. James is not the only one to use that style cowl (LoPresti is another).
 
I like it....but...

Since you asked specifically about an -8 (which is different than a -7), if I recall correctly, when I was building, the Sam James cowl for the -8 required you to have a prop extension. I never read enough convincing data that showed me that the prop extension on a Hartzell C/S prop was fully endorsed for aerobatics, and this was a show stopper for me.

Now that was over three years ago, and it is possible that the Sam James folks have reworked their design, in which case - yeah, I think the round inlets look very cool! But from the accounts I have read, you WILL spend more time building the cowl than if you went stock van's.

Paul
 
Aerobatics

Paul
A guy in chino has an extension on his 8 and he told me it has limited his aerobatics. This could be a deal killer:eek:
 
a few more considerations

I considered the James cowl for my 7A, but finally decided against it when I heard that the prop extension would limit the g-loads the plane should experience. I would like to fly aerobatics, so that was a negative factor. I also didn't want to deal with the fab that would be required to fit an injected IO360 with forward facing induction into the cowl WITHOUT using the snorkel. I just don't like the look of the snorkel.

I think the cowl and plenum are great ideas if you don't have either of my limitations.

The advantages are supposed to be better cooling, less drag/more speed and arguably a more modern look.
 
"Is it worth it?" is a question that can only be answered when one knows your particular priorities. I did it on my RV-8 and in retrospect, and with all things considered, would not do it again. When I built my second RV I went with the stock cowl.

Not sure if you've seen it or not as you've done your research, but here's a fairly thorough account of my experience...
http://www.romeolima.com/RV8/Cowl.htm

I got by without the prop extension. If I had had to use the extension then there would have been no way, that is a deal killer for me from the get go.
 
Retrofitting with Van Cowl

I just received my SJ plenum and will install it using my finished and flying RV7 with its stock cowling. It will take some major reworking of the front to fit the inlets in but I'm up for the challenge. A little extra speed and better cooling is what drove my decision to try this and it will allow me to gauge the performance increases from stock to using the plenum. I'll keep everyone posted on the numbers once the work is done which I am pushing to finish to fly it done to Oshkosh.
 
Works for me

I have a 2.25" prop extension and a Hartzell C/s prop.

Do I fly aerobatics...Er yeah actually I do..:)

http://youtube.com/user/frankhinde

Now having said that...The RV is not a rip snorting aerobatic airplane, I avoid gyroscopic manouvers (I.e adding high power to aggravate spins etc) but the RV is just not that sort of airplane if you see what I mean.

I have close to 300 hours on this set up.

I also started a Yahoogroup to gather all the builders in one spot and there is a lot of good info there now.

http://groups.yahoo.com/group/JamesAircraft/

Would I do it again?..Look at the beautiful airplane at the front of the yahoo group..You tell me?..:)

Frank
 
Another opinion

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.
 
Why I posted

Randy,
Your website and experience is one of the reasons 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
 
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
 
N23J said:
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
Click to expand...

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.
 
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.
 
tcone1 said:
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.
Click to expand...

Tim,
Do you have any pictures you could share?
 
Way to go Mike

mikegraycmg said:
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.
Click to expand...

I have to look into that I really don't think want to do the prop ext. Way to go on your 8:D
 
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!
 
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
 
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

N23J said:
I have to look into that I really don't think want to do the prop ext. Way to go on your 8:D
Click to expand...

mikegraycmg said:
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.
Click to expand...
 
SJ w/ no prop extension

vmirv8bldr said:
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".
Click to expand...

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

my.php
 
gyroscopic effects don't care about prop extensions

Just to be clear about one thing, the gyroscopic torque that the propellor exerts on the crankshaft due to precession is the same irrespective of how long the prop extension is (or isn't).

The 'g' load is the only torque/bending moment that is applied to the prop extension and this will increase the bearing loads and apply fatique loads to the prop extension and crank flange itself. If you go with a lighter propellor, you can increase the 'g'-load limit for the same extension design

A
 
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