R

rvbldr3170

Active Member
HI All,
I am building an RV-4, and have placed an order for Sam James cowl/plenum combination, so I have a couple of questions to "those that have gone before"

1. any tips/tricks to installation of the cowl? How was the initial fit of yours?

2. What is the "real world" speed increase expectation over Van's cowl? I have heard several opinions on this but I'd like someone who has definite EXPERIENCE not an opinion.

Regards,
Merle

Wings almost finished - fuselage start by August
 
Merle - cant help you with your queries, just want to alert you to the fact that on the -4, the Sam James cowl and a c/s prop are I think mutually exclusive. At least true of MT. I expect you are going fp.

I wanted to go Sam James but MT was more important to me.

Have fun.
 
Not so fast...

Steve/Merle,

Eight years ago I helped a friend install a complete Sam James setup on a stock, 160HP RV4 including cowling, rings, plenum, pants, leg fairings and wing root fairings. I know Sam personally and he is a great guy with a good product.
The Conversion: Before we tore it apart we did comparison flying alongside The Bandit which has stock pants, leg fairings and cowl with a 150HP 0-320 (Redneck Blueprinted in my garage) with a Warnke ACS wood prop. Our 2 RV4's were very closely matched rpm for rpm except at full throttle The Bandit could turn 2850 and walk away from "Ole Yeller" at about 5 knots. Then came the conversion. After 3 weeks of messy glass work, filling, sanding, dust and resin smells permeating the air and $2000 poorer, we rolled Ole' Yeller out for the big test flight. I chased him in The Bandit and noticed immediately I could "hang" with him no problem on his wing. At lower power settings the difference in speed slightly noticeable, but at full throttle I still walked away from him just slightly! Needless to say, my friend wasn't impressed...
Epilogue: OK, there were plusses for the conversion of which fuel economy was one. He could go slightly further on the same tank of gas at the same speed than I could. The other was cooling, everything ran cooler with the plenum. The conversion does improve efficiency slightly. Overall though, I flew about 25 hours while he was filling, sanding and spending 2 grand that I saved for gas and flying.

Your Call...


Rob Ray
15,000 gallons burned in my RV4...
Alot more in the F16...
 
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Hard to say

For some reason, even though performance was really important to me on paper by the time I got it flying it didn't seem to matter that much.

I measured 205mph at 8k in my 7a with the James cowl but that was at 2600rpm, not 2700.

The only other comparison was flying chase on a 7a first flight, his with a Van's cowl but no main wheelpants...Had the leg farings though. (cost say 5mph)

I aught up to him and had to thottle back by a couple of inches mp to stay with him.

Doesn't tell you much I'm afraid.

I used the Hartzell C/S prop and 2.25" extension to go with the James cowl/plenum.

There is a Yahoo group that I set up that is dedicated to the cowl install and there are a few folk with actual speed measurements on there I believe.

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

Cheers

Frank 7a...Still right side up
 
Will Jame's New Cowl

Merle/Smoky

I purchased the holy cowl from Will James in July of last year. Sometime in September/October, Will called me out of the blue and asked if I had fitted it yet. No was my reply. He said his original cowl was made from a pattern taken off of Sam Jame's RV-4 and did not match the drawings from Vans.

He told me not to start fitting and would send me a NEW replacement cowl. He did so at his sole expense. (Told me to make a bird house out of the old one! :D ) My good friend and I have installed it, the new one, now; and I would say it was NOT any more difficult than a standard cowl from Vans. Smoky Ray might not have had such a task with the new "corrected" cowl???

Have an 0-320 160 hp with a 4" extension swinging an Aymar Demuth wood proop. Have a 3 blade Catto on order.

I don't have any performance figures for you as we're doing some extensive mods and I haven't flown it yet. Hope to fire up engine this weekend and fly it again next week.

I wanted to replace the engine mount and use the longer gear legs. So it was a good time to replace the cowl. I like the looks of the cowl; so even if I don't get any performance gains....I just like the looks.

Will report results to you guys after flying.

Cheers,

Deal Fair
RV4 (N34CB)
George West, TX
 
Merle:

I really like the fit of the cowl. Will take photos and post them soon.

Deal Fair
RV4 (N34CB)
George West, TX
 
SJ Cowl

Merle:

I'm afraid that I'm another SJ fan with no real world comparison as to before and after speed claims. That said; I have an RV-8 that I fitted an earlier James cowl. That particular cowl had some bad "press" from earlier posts on some of the RV sites.

I bought Sam's cowl because I really like the looks. I bought the plenum to get even CHT's. I bought the wheel pants because they're smaller with less flat plate and wetted area for less drag.

This year at Sun-n-Fun, I ran into Sam and Will and told them of the problems I had with fitting the cowl. They informed me that Will James had built a new mold and would lay up a new cowl to replace the old one for FREE! Can't beat that for customer service. If youl have any problems don't hesitate to call them for clarification.

Real world speeds for me:
RV-8, IO-360-A3B6D 200hp Angle Valve engine from a Mooney 201, McCauley constant speed prop from a Piper Arrow.
Sam James cowl, plenum and wheel pants.
7500ft altitude, engine turning 2300rpm, manifold pressure 23in. Hg. <10gph,
178-182 knots TAS depending on density altitude. These speeds verified by GPS average on 4 way runs on autopilot.

Not sure what percentage power that is. (Guessing about 70????). I believe this meets or exceeds Van's published speeds.

A long winded way to say that I think you'll like the James cowl. I sure do!
 
Thanks for all the input guys, It really helps.
I have ordered the Van's finish kit minus the cowling, so the added cost for the SJ cowl is only about $300, I guess the speed increase I was expecting is maybe not as much as I first thought, and without doing a comparison with the same airframe using Van's and then SJ's, it's really a crapshoot as to whether there is any performance gains to be had.
But it does look cool!!
 
Yeah it does

At least with a nice paint job to accentuate the sleeker lines it looks great.

Frank
 
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