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Fitting a Sam James Plenum to Vans Standard Cowl

R

rwtalbot

Well Known Member
G'Day Everyone,

I am considering fitting a Sam James Plenum to my RV7. As I am based in Australia and the shipping for an entire cowl, I was thinking of just purchasing the Plenum and adapting it to Van's Standard cowl.

Will James can provide a mould of the front 7" of the SJ cowl which can be cut and adapted to fit on the existing one I have. He says a number of people have elected to go this way.

I'm hoping someone here has been through the process and can give me some insights as to how it turned out. I'm particularly interested in seeing some pictures of the finished/painted cowl and hearing if there was an increase in cooling as well as speed.

Cheers
Richard
 
Like this:
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VAF member: Yakdriver has a James Plenum and a modified Vans cowl.
 
I retrofited my RV7 with the plenum and modified the Vans cowling using the round inserts they provide.

I posted pictures of the cowling work on the Sam James yahoo group which you should join up with.

Hope this helps.
 
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I had oil cooling problems with my modified cowl. I ended up going to a stock Van's cowl and baffling with a Rod Bower FI intake. Oil runs 20 degrees cooler and my airplane is 8 mph faster. Don
 
Check this out..........

I made this plenum for a friends RV8, IO360 Parallel Valve. It is made out of carbon fiber, very lite. Fits very well, currently retro fitting one of these to a 6a. Due to demand, I will be making some more. It fits standard Van's baffles and makes it very easy to fit. Brent got carried away with the nutplates, you could probably use fewer.

The ducts in the front are being reshaped to meet very close to the standard Van's cowl. NASA's report says with standard baffles in great shape, air loss is still 38%, the number one thing to do to drop this loss to 8% is use a "doghouse" like the one shown below. The remaining 8% loss is due to air entry into the bottom cowl around the prop.

The plenum made has not be tried at this point, but looks very promising, very tight.

http://img96.imageshack.us/i/img0130op.jpg/
http://img8.imageshack.us/i/img0127fv.jpg/
 
yakdriver said:
I had oil cooling problems with my modified cowl. I ended up going to a stock Van's cowl and baffling with a Rod Bower FI intake. Oil runs 20 degrees cooler and my airplane is 8 mph faster. Don
Click to expand...


G'day Don,

That's very interesting. Do you have a theory on the reason for the loss of speed/cooling or are you currently exceeding Van's numbers? What are you current figures for speed and oil temps? Perhaps the Rod Bower FI is giving you an advantage.

Also did you see any changes to CHT's? My experience seems to be that the ECI cylinders I have run hotter than the Superior/Lycoming units.

Cheers
Richard
 
Capflyer said:
I retrofitted my RV7 with the plenum and modified the Vans cowling using the round inserts they provide. Before you go through doing all the work this will entail it is important to note that in my case it did absolutely nothing to either the performance of the plane or cooling. That said, I did like the way it looked.
Click to expand...

In my case, I already have a plenum which I believe is less than ideal, particularly in climb. Like CNEJR's unit, in that it integrates with the stock cowl inlets. Having flown it for a while and done quite a bit of testing, I think that with the plenum it is absolutely critical to ensure the transition between inlet and the chamber is smooth and well sealed.

I don't know if the SJ mod will be any better than Van's standard system, but if it is as good I think I will see an improvement.

I saw your detailed photos on the SJ forum. What I didn't have was pictures of the painted airplane and an idea of the benefits. Like you I think the plenum looks good.

Out of interest, what is the configuration of your engine, i.e. HP, cylinder manufacturer, electronic ignition? Also, What sort of CHTs/oil temps are you seeing at 75% power?

From looking at the pictures it seems like you have a standard oil cooler mounted to the firewall with 3" SCAT. Is that correct?

Cheers
Richard
 
Almost the same

Hi Richard

I am doing almost the same as you propose in that I am modifying my cowl to have round inlets like the show planes/Sam James cowls, but I have also made my own plenum. Also I am sealing the front of the cowl to minimise losses there. If I can work out how to put images on I will d this in the next few days. If not send me a pm with your email address and I will forward them.

Whenever you modify there is a lot of extra work and buying parts off the shelf saves a lot of time.

Like you I would like to see some before and after figures to se if what I am doing will be of anything more than asthetic benefit.
 
CNEJR said:
The plenum made has not be tried at this point, but looks very promising, very tight.
Click to expand...

Chuck,

Unfortunately, I already have a unit very much like yours that doesn't work. Please do everyone a favour and go and flight test what you are building on a couple of aircraft properly before you start selling them. That is measure the performance of a well built, flying aircraft, remove the standard baffles and then install and measure yours.

If you can consistently improve on Van's standard performance you may have a marketable product. I've spent many hours fitting the unit I have above standard baffles and troubleshooting why it won?t cool. At this point I may just install standard Van's stuff and go flying.

Cheers
Richard
 
Hmmm..........

I wonder why your's won't work? Do you have it sealed well from the cowl to the inlets? It would be interesting to see pictures. Is it partitioned?

The reason I stated " The plenum made has not been tried" is because it has no data good or bad. It looks promising but we shall see.

I didn't say anything about selling them. I just have a number of friends that want to give it a try, from looking at it. Have to say though, generally the stuff I design & do works pretty well. All it is really doing is replacing the top of the cowl, but with a an air seal where the traditional baffles generally leak.

Just have to wait and see.

One thing you might think about. If you have your plenum sealed up well, then you might think about increasing the exit area on the cowl bottom. I did this on my 6 and it had a dramatic effect on temps The rule of thumb I always used is double your exit area to your inlet area. Need that pressure drop to pull the air. Good Luck.
 
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I have seen Plenums work great

The builder assist guy I used, Noel Simmons uses a plenum with a stock cowl on every RV I have seen exit his shop and they cool great. Recently I have seen them with milspec 1/4 turn fasteners which is a great idea.

Hans
 
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