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Sam James RV-7 Builders- need feedback

BillL

Well Known Member
I built a replacement plenum cover for my SJ cowl (long). It uses epoxy with a Tg over 300F. The cooling inlet areas are increased by over 40% at the head, and the area flow diffusers are much smoother. It has a perimeter flange for attachment, can be removed without cutting a lot of RTV, the oil cooler can sit up high, and it weighs less than the rubber baffle material in the standard kit. A core material was added to the center section to substantially stiffen the structure.

It took way to much time and money just to make one. The question: would you be interested in buying one to help me offset the cost of the materials of development? If you are interested, send me a PM-Email and I will send a draft report with more details, and answer any questions. The plenum cover is very smooth on the top side as it is a female mold and vacuum infused with resin. The inlets are on bucks, and hand layups. The exterior would need bodywork to look as nice as the cover. I think your installation time of fitting to perfection would be very short. Parallel valve only, though. I have materials for 4-5 sets, and wish to do this while skills are still fresh.

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Hmmmmm

That is very nice!

I would order one but I have a short cowl on my -9.

Well, you have the 360, so probably already used the 7 engine mount, but the baffles?

I thought this might come up and don't have a ready answer as I am not aware of the geometry changes, the question . . is it closer to the engine or further? Also, do you already have the SJ plenum cover? If so and you have already cut down the baffles, would you be making some new pieces?

If you are serious, I could make some patterns of the side baffle profiles and send to you to check. If that works out, then I would send an early development piece (if you promise not to take a picture of it.) to see if it will fit. If the cover fits, then the next steps are the inlet transitions. My cowl is already 7/8" shorter. It might be that you could make a set of DanH style inlets from rubber and eliminate another 1.5 inches from the transition. Maybe the shorty could work just fine.

Gee - already sounding alike a bit of work, but could make a nice change.
 
I built a replacement plenum cover for my SJ cowl (long). It uses epoxy with a Tg over 300F. The cooling inlet areas are increased by over 40% at the head, and the area flow diffusers are much smoother.

And that, boys and girls, is what the inlet diffusers should look like.
 
Sure looks righteous. Are the angles on the starter ring temporary cowl supports?

Right you are! - - they allowed me to use the bolts as touch points for the upper cowl. That way it could be installed w/o the lower with some assurance of position for marking baffles, checking clearances etc.
 
Nice job!

Bill,
Very nice work and as someone who had to rework a Sam James plenum, I can understand why you took on this task. The only thing I see that you may want to reconsider is the gap between the rear of the inlet ring and the front of the inlets on the platinum. When the engine shuts down it twist quite a bit and I think that your gap is not enough to allow for this movement.
 
Well, you have the 360, so probably already used the 7 engine mount, but the baffles?
...

Nope, I have the -9 engine mount. The -9 has longer gear legs than the -7 and they come out at a different angle. That is required to get the wing stalled in the three point position.

I could buy new baffles but the transition is so short it probably wouldn't make any difference as there isn't enough room for the air to slow down before it hits the cylinders.

I cut off the front of my plenum and fiberglassed it right to the nose of my engine so it is a perfect fit. That said, I like your solution.
 
Bill,

I'm intersted, but VAF says you've exceeded your private message limit. Contact me offline.

David
[email protected]

Email on the way, David.

Bill,
Very nice work and as someone who had to rework a Sam James plenum, I can understand why you took on this task. The only thing I see that you may want to reconsider is the gap between the rear of the inlet ring and the front of the inlets on the platinum. When the engine shuts down it twist quite a bit and I think that your gap is not enough to allow for this movement.

Nice work on the cover, Jake, I like your site and work. The clearance was close on the inlets to the rings for fitting. I will be doing some experimentation on what the gap should be. The prop has 5/8" clearance, so maybe 1/2" will work on the inlets. I was thinking shear would be the greatest displacement, from reaction torque, but yaw can/will occur too. 3/16" is definitely too small. I am kinda resisting just making the last 4" of the inlets out of rubber and bonding them to the inlet rings in order to keep the airflow clean. For now I will stick with the neoprene wrap.
 
Plenum

Bill Im in and Seriously Interested. just sent you a PM. Call me I would love to talk.

Im a 7 SJ Long cowl Angle Valve AIA. I have just started started fitting the SJ plenum and stopped... I had planned to build my own but the material cost to build just one and my access to an oven to post cure became a problem.

The Cowl I am very happy with,the fit and install went smooth. However I am back to building my own plenum.

And now I see your post

Yes Please call me I PM'd my #

Thanks
 
Post cure oven DIY

Bill Im in and Seriously Interested. just sent you a PM. Call me I would love to talk.

Im a 7 SJ Long cowl Angle Valve AIA. I have just started started fitting the SJ plenum and stopped... I had planned to build my own but the material cost to build just one and my access to an oven to post cure became a problem.

The Cowl I am very happy with,the fit and install went smooth. However I am back to building my own plenum.

And now I see your post

Yes Please call me I PM'd my #

Thanks

I am discussing this with Jason off line, but for others, if the hurtle is an oven, here is the solution. 1" thick duct board. I heated it to 300f with no problem. Specs are higher on the aluminized side. Cost was about $35, not including thermocouple reader.

The plenum cover was post cure in this oven per resin supplier specifications. The floor (rack) was covered except for a 2-3" perimeter gap. The part was set on a 4" thick piece of wall insulation blanket to prevent hard points touching and reduce possibility of drooping. If the oven is preheated, then the element seldom comes on and temperature excursions are minimal. After curing several parts, I will run the oven through a clean cycle and let you know if any adverse effects are found. Smell and deposits thus far are minimal, so your home oven might work, but not endorsed at this time.
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I just received my plenum from BillL today, compared to all the other fiberglass pieces I've used this piece is great. I'm a novice so my opinion isn't worth much. Top surface looks like a light scuff and it would be ready for primer, final pinhole check and paint. Even with the plenum sitting on top of the old baffle seals the plenum shape seems to fit the shape of the stock Van's baffling very well, I'll have to remake the center baffle behind the spinner as noted by Bill. This saved me a ton of work, is better quality than I would've produced and the price was right.
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Will this set up work for an O-320 are the egine dimensions close to the same?

I don't know yet. I am working with a builder and we will have to wait and see. I don't have access to a 320, or plane to compare fits. It is certainly more narrow, which affects both plenum cover and inlets.

It might be months until we know for sure. Sorry, but that is the story.
 
plenum

Hi Bill, Your plenum looks great. I would be interested in a price for one of your plenums. Frank
 
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