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Pros/Cons Std Cowl versus James

motodave

Well Known Member
I just ordered the finishing kit for my 7 (Aug delivery) and looking for some advice / comments / experience on the std Vans cowl versus the James cowl. I've seen the James cowl on a local RV (thanks Brian). The cowl looks great and builder did a excellent job and he gave good reviews. The James is a more expensive but now is the time to make change so I can get a credit from Van's.

I like the idea of more direct air flow with James versus the snorkel Van's uses, circular openings and plenum option versus baffles. I'm planing on using hinge pins on the side as I like the seamless look and quick fasteners on the top for easy access. Any other experience or comments to consider? I have a couple of weeks to make changes to order.

Thanks for your help & thoughts.
 
I was told and read here that the James cowl is a little more aerodynamic and may gain as much as 5 knots. When ordering my Catto prop, they tailored the prop for a James cowl, so they know something.
 
I would not buy a james cowl or plenum again! Might be slightly faster, but they are way too crude out of the mold, nothing fits, caused an extra month on the build!! Also, the engine runs hotter than my previous RV-7. I had to do a lot of work to get it to fit around the exhaust pipes, widh I just stayed with the stock Vans cowl!!

Regards,


Gary
 
+1 for bad fit 😏

Mine is -4, but the two halves did not align well. Residual stress is a concern and lots of cosmetic work required . This cowl predates the sale of the business so YMMV.
 
Slightly different experience

I hate to disagree with Gary, since he has years more experience than I do with RV's. However, my RV-7A extended James Cowl (built by Will James) fit really well and the quality of the exterior surface was outstanding. I did have to send my exhaust back to Clint at Vetterman twice to get one of the pipes modified for clearance. We did not have to modify the cowling at all for exhaust fit.

To be fair, the Build Tech for the cowl fit (at Synergy in Eugene) had decades of composite experience and my A&P son was also there working with me. The builder next to me (with an RV-8) had a lot of issues getting his Van's cowl and snorkel to fit. He had to modify both substantially to fit around the starter and fuel servo. He had essentially the same engine and cold air sump as I did.

As to the plenum, I used a Bill Lane plenum. One of the Build Techs at Synergy had previously installed a Sam James plenum and indicated it took almost two weeks to get it to fit properly. Eric and I did the BL plenum in less than two days.

I do agree with Gary that this cowl does not cool as well, especially on the ground. It's probably less tolerant of less than perfect baffling and leaks than the stock Van's cowl.

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Looks cool...but not so cool...

I did not build my RV7a. It has a Sam James Cowl and 3 blade Catto prop. I like the way it looks. It has 1/4 turn camlock fasteners and is easy to get on and off. It has a plenum and there are many screws to remove to get to the top of the motor. I wish my plane ran cooler...especially #4. This plane is all I really know but I read of people having lower CHT with standard cowl.
 
I did not build my RV7a. It has a Sam James Cowl and 3 blade Catto prop. I like the way it looks. It has 1/4 turn camlock fasteners and is easy to get on and off. It has a plenum and there are many screws to remove to get to the top of the motor. I wish my plane ran cooler...especially #4. This plane is all I really know but I read of people having lower CHT with standard cowl.

I have the exact same set up on my 9 and have experienced the same issue with the #4 CHT. I?ve been able to balance the CHT?s in cruise but my #4 is still hotter than all other cylinders in climb.
I put a small piece of aluminum tape on the #1 cylinder and that has helped quite a bit to lower the #4 CHT in climb. #4 no longer exceeds 400 degrees in the climb and definitely helped to balance all the CHT?s in cruise. In cruise all my CHTs are now within 10 degrees of each other.
I?m not the builder of my 9. My plan at my next inspection is to fabricate a more permanent solution using a piece of aluminum angle iron.
 
I have the exact same set up on my 9 and have experienced the same issue with the #4 CHT. I?ve been able to balance the CHT?s in cruise but my #4 is still hotter than all other cylinders in climb.
I put a small piece of aluminum tape on the #1 cylinder and that has helped quite a bit to lower the #4 CHT in climb. #4 no longer exceeds 400 degrees in the climb and definitely helped to balance all the CHT?s in cruise. In cruise all my CHTs are now within 10 degrees of each other.
I?m not the builder of my 9. My plan at my next inspection is to fabricate a more permanent solution using a piece of aluminum angle iron.

Plenum or no plenum? We're going with the James cowl on out build and I'm curious what to expect.
 
I have installed 2 James extended cowls and plenums on 20 year old, carb'd 360's on RV-6's. The cowling was very good quality! The plenum sucked and I had to virtually cut it up and make a custom plenum. I have fiberglass skills so not a problem. The Vetterman exhausts worked fine. The cooling is normal RV.
I used 1/4 turn fasteners all around and love it. I also used James intakes.
Big job, but very happy with overall package.
 
Here is what I posted on page 9 of this thread regarding the Sam James cowl.

One thing to keep in mind, the Sam James cowls and plenum business was recently sold and the new owners are working on improving the quality of the products.

After 16.5 hours of work, the top and bottom cowls are on and attached at the firewall. There is still a lot of work left to do, such as rivet a piece of aluminum along the horizontal part line to hold the Skybolt fasteners, layup some fiberglass in the nose area, next to the spinner for platenuts to hold the nose together, cut and fit the oil door, and a few other things.

A number of people have compared the James Aircraft cowl to the Van's and said the James is of better quality. I'm not so sure that is true.

* There are a LOT of pin holes in the James cowl, call it equal to the Van's cowl. The trimming effort is the same, so call that equal.
* The opening for the crankshaft had to be sized on the Van's cowl but the James cowl was the correct size out of the box. Advantage James
* On the Van's cowl you have to glass in the air ramps but on the James cowl you have to fit a plenum, advantage Van's.
* There is no recess for the oil door in the James cowl but it is easy to see where to cut the door, advantage Van's.
* With the James cowl, you have to either layup fiberglass on the top of cowl prior to cutting the oil door opening so you can use that newly formed piece for the door or use caution when cutting the hole. Van's gives you a door, advantage Van's.
* With the James cowl, you have to fit and glass in three rings; two for the cooling air inlets and one for the intake air. Advantage Van's.
* With the James cowl, you have to do a lot of work on the cooling plenum. On the Van's cowl, you have to do a lot of work with the airseal fabric. Advantage Van's.

As for cost, the plenum and James cowl are only $100 more than the Van's cowl, advantage Van's, just barely.

In the looks department, ADVANTAGE James cowl. That thing looks fast just sitting there. IMveryHO!
 
Another data point. My SJ long cowl fit great and I didn't have to mess with a snorkel that many have said requires a much rework. I also have the plenum, built by Will and it fit quite well.

Exhaust is a Vetterman trombone and required a small bump on the left side of the lower cowl for pipe clamp clearance. I could have sent it back but it was an hour of glass work vs a couple weeks turn around for to send the pipe back.

Temps are well under control (< 380 in climb / 350-360 in cruise). If CHTs are all high, your timing is likely advanced too much (assuming baffles are well sealed). Engines running high compression (>8.5/1) likely need to retard timing a degree or three.
 
Plenum or no plenum? We're going with the James cowl on out build and I'm curious what to expect.

I just finished an RV-8 with a stock Van?s cowl and baffles - AND I REGRET that decision.

I built the RV-10 with a James Cowl and plenum and was very pleased with the quality and fit, and the performance. I did not do that for the RV-8 (a variety or reasons) but if I had to do it over again I would go with the plenum.

Carl
 
I'm not at the point of ordering the exhaust yet (or engine for that matter) but does the James work with std Van's exhaust? I hear a lot about the Vetterman but don't know enough about it yet.

This will be a tough choice on the cowl with all the pro's / con's...
 
I'm not at the point of ordering the exhaust yet (or engine for that matter) but does the James work with std Van's exhaust? I hear a lot about the Vetterman but don't know enough about it yet.

This will be a tough choice on the cowl with all the pro's / con's...

Dave, the cowl will fit with the Vans or Vetterman exhaust.

For the hinge pins, I prefer and have done a few builds using a hidden hinge so there is nothing showing on the front of the cowl where Vans has you put in the pins. Run them from inside the cockpit. Use the aluminum tubing between the firewall and cockpit to guide the pins into the first eyelet on the bottom cowl hinge. I used solid drawer pulls that make it easy to push and pull the pins in the cockpit.
 
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Here is what I posted on page 9 of this thread regarding the Sam James cowl.

One thing to keep in mind, the Sam James cowls and plenum business was recently sold and the new owners are working on improving the quality of the products.

Sounds like Will was a naughty boy and forgot to put the oil door in the box. The cowls I purchased from him prior to buying the business all had the door with them and we continue to provide the door with every cowl.
 
Picture?

I have the exact same set up on my 9 and have experienced the same issue with the #4 CHT. I?ve been able to balance the CHT?s in cruise but my #4 is still hotter than all other cylinders in climb.
I put a small piece of aluminum tape on the #1 cylinder and that has helped quite a bit to lower the #4 CHT in climb. #4 no longer exceeds 400 degrees in the climb and definitely helped to balance all the CHT?s in cruise. In cruise all my CHTs are now within 10 degrees of each other.
I?m not the builder of my 9. My plan at my next inspection is to fabricate a more permanent solution using a piece of aluminum angle iron.

Could you share a picture of what you did?
 
On my 9A, I used both the James cowl and James plenum.

The cowl was excellent, my experience there was quite nice and it fit up beautifully. The plenum was a disaster and I ended up cutting 3 of the 4 corners and the entire front face off and reglassing those - it would have been faster to start from scratch.

As Bill pointed out, the company has recently sold and has a new owner so current experiences may vary.
 
I went with the James cowl simply because I liked the look of it. This is my first build so I have no experience with the vans cowl. What I can attest to is that my cowl was made and shipped by the previous James owners and was missing a couple parts and had misshipped another part. In total 3 things were wrong. The new owners made things right even though they weren't responsible for the errors. There was considerable work getting the rings in properly but they look great and I'm very happy with how they came out. As far as engine cooling that is yet to be seen. I'm doing a few mods to the baffles to help with that.
 
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