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Carbon Plenum Install

RudiGreyling

Well Known Member
Ok so I am 90% complete with the baffles and ready to post pictures of the long process. Here is the plenum as received.
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A person just trim your baffles as per the plans as if you were going to fit rubber seals. This plenum just goes in place of the rubber seals. This also means existing airplanes with rubber seals can retro fit, or vica versa, if it does not work properly to your liking then you can remove plenum and put your rubber seals back. So I was willing to take the risk...The plenum is actually a perfect match to the countour of your top cowl. Jan used a top cowl as a plug for it. So if you trim for rubbers every where the same clearance, and the plenum follows the contours of the top cowl, you have perfect clearance inside the top cowl. Simple and very clever!

I masking tapped the sides so that the plenum dont scratch since the baffles are still rough cut at this stage. Then marked and made small adjustments so the baffles follow the plenum pofile perfectly and then decided where my nutplate screw holes will go and drilled and clecko'ed the plenum in place. I added 2 screws per loose baffle plate over each cylinder along the sides, and evenly spaced them the same on the front and rear.
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A tip for installing the LH rear screw, drill a access hole in the rear cover so you can get your screw driver in.
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The Front
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Install the nutplates.
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more nutplates
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I put some friction free tape on the sides of the plenum and trim to fit to contour.
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Mark and trim the front overhangs and oil door position.
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After Trimming,.
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.....
 
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....

McMaster Carr Edge Rubber to seal the oil access door against the top cowl.
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With a nice carbon plenum cover the grey tappet covers had to be repainted to match.
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Gloss Black Rattle Can high heat Engine Enamel.
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Paint the Baffles a nice silver colour too and refit them
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Fit the plenum in place
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Close up Right Front. The front lip is the standard Vans edge lip rubber supplied to seal under the HStab for instance, and this rubber lip pusses against the top cowl inlet ramps to seal the top.
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Top View
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Left Front (jip some screws missing cause it is just a temporary fit for photo purposes.)
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Oil hatch cutout detail
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I just need to do the inlet rubbers and the bottom fastners to pull the front and rear bottom baffles together, and seal the baffle gaps against the engine, then I am 100% done.

Regards,
Rudi
 
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Looks good Rudi.

Interesting way to handle the oil access ----- instead of a separate inner door.
 
What is the weight of the carbon fibre plenum Rudi?

Anthony, I am not sure but it is light enough, more than rubbers but then this seals better. Maybe Jan will chip in later about the weight, if not I'll weigh it next time I take it off in a week or two...Rudi
 
Very Cool!

Rudi,

Great work on your plenum. My wife and I just received the tail kit for our 10 and are anxious to get started. I am close but still have a little more shop setup to do. (I think I have shop OCD, like you do..) Thanks for the post and beautiful pics. The time you take to share your experiences on this forum is very helpful to us newbies, and much appreciated.

Mike
 
I want one! I like Carbon so much better than fiberglass, too bad noone makes a one for the IO-360's, hint hint :)

-david
 
Weights

Thanks Rudi,
I have weighed them now.
The Carbon fiber model weighs 900 Grams - 32 Ounces only. :)
The Glass model weighs 1200 Grams - 42 Ounces only.

Just out of interest - I have also weighed a roll of baffle rubber with some of it used and it weighed about a 1000 Grams - 35 Ounces.

Another way of tackling the oil door seal is to glue soft foam rubber strips on the inside of the top cowl.

flyguy - we have already made one for the IO-360 RV8 and have also made a dummy for the IO-360 RV7. So keep a close watch on http://www.rvbits.com
 
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How does it seal

Dan, You can use two short strip of rubber like the ones you use underneath the HS to make a seal. Even if you do not seal it and there is a gap, I found that you cannot even see the difference on the temps. That gap is much less in volume than all the leaks you normally have with rubbers.
 
Jan, so how does it seal to the cowl inlets?

Hi Dan,

The front seals against inlet ramps using the HS rubbers see below.
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To get to this stage the front lips of the plenum as supplied is a little bit longer than required cause of differences in the inlet ramps where people glue them in on the top cowl. You would trial fit the plenum and then fit your top cowl, and then cut those lips back until it clears your inlet ramps by 1/8" - 1/4". The HS rubbers then seal up against the inlet ramp. Below is my lip cut lines defined with white tape. You then glue the HS rubbers to the lip...I used High Temp Black RTV to glue the rubbers to the lip
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The sides seal with normal rubbers inside the bottom Cowl inlets on top of your baffles.

I hope it makes sense!

Rudi
 
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Results ?

A very old thread.......

To all the builders that installed the RVBits plenum,would you mind sharing your results.

Did it provide the cooling you expected ?
Was the front transition where it touch?s the upper cowl a maintenance problem?
Was oil temps on par with your baffled friends?

The reason I ask is that I have my RV-10 with very good cooling even in the Hot Australian summer and I know I have leakage out my baffles and rubbers.
My choice this annual is to do a much better job of my baffle rubbers than when I built 4 years ago or install a Plenum that I already own but never fitted.

My thoughts are that there is some cooling drag to be recovered either way.

All thoughts and results welcome......
 
Hi Ashley, as the maker of these a few comments and a question.
My original idea with this was just to have proper and neat looking seal with no rubbers folding down the line.
So if your rubbers are really sealing well there is no gain. Personally I found that the front transition can even be a small gap with no rubber, but rather use a rubber to be safe.
Something else. Do you have a bigger oil cooler installed. With our ISA+ conditions here in South Africa it is a must to install the bigger 17 fin cooler.
 
Jan, you make beautiful parts. Why not go back to the drawing board and design a plenum lid incorporating truly sealed inlets and dipstick access? This one can't be any better than flap seals.

Actually, it incorporates standard flap seals around both inlets, the area of most difficulty for builders. In particular, note the prop governor region. This lid only replaces the long side and rear flap seals which are easy to build.
 
Hi Jan,

Yes,
I have the larger Airflow Systems 2007X oil cooler and it handles the Far North Australian temps well.It required only a small mod to the existing oil cooler mount and Bill at Airflow has done a lot of flow testing on these units.
Also fitted the recommended flow divider for the oil cooler.

I fitted my baffle rubbers as per plans and have been rewarded with a good cooling RV-10.
However after 4 years and 500 hrs, the stains on the under side of my top cowl show a very clear picture of where my baffle rubbers do not seal.
This is all wasted cooling air and drag.

Dan,
The cowl inlets on the RV-10 have reverse airflow at the blade root. I have observed this on my own aircraft where my first baffle rubbers would actually lift backwards into the A/C serpentine belt.
So any transition for the plenum would need to address this problem.
The simplest is adding round inlets as far outboard on the cowl and slightly higher than centre as recommended by Sonja Englert (Cessna TTX engineer )
I am not afraid of tackling the cowl and transitions and realise that this is only part of the equation to reducing cooling drag.

So my question would be,what size inlet rings ?
We know the first Sam James rings were to small,and I do plan to throttle the exit later in the project,so do I just start with 6? rings and work from there?
 
SNIP

So my question would be,what size inlet rings ?
We know the first Sam James rings were to small,and I do plan to throttle the exit later in the project,so do I just start with 6? rings and work from there?

I built my RV-10 using the James Cowl as well as plenum. The rings that came with it work just fine.

Too bad Will James no longer offers this cowl. I would not build another RV-10 without it.

Carl
 
Carl were they the later large rings or the earlier small rings?

Would you mind sharing what size yours are.

Cheers,
 
@ Dan - sitting halfway around the world is not easy. Shipping is way too expensive to get from SA to you guys in USA.
 
Dan,The cowl inlets on the RV-10 have reverse airflow at the blade root. I have observed this on my own aircraft where my first baffle rubbers would actually lift backwards into the A/C serpentine belt.
So any transition for the plenum would need to address this problem.
The simplest is adding round inlets as far outboard on the cowl and slightly higher than centre as recommended by Sonja Englert (Cessna TTX engineer )
I am not afraid of tackling the cowl and transitions and realize that this is only part of the equation to reducing cooling drag.

Sounds familiar.

Inlet%20Prelim2.jpg


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So my question would be,what size inlet rings ?
We know the first Sam James rings were to small,and I do plan to throttle the exit later in the project,so do I just start with 6” rings and work from there?

There is no "perfect" size; any size covers an operating range. All the data says low Vi/Vo is superior, so when in doubt, go larger. Experimentally, six inches diameter seems to work well with the 390 and 540. The external diffusion (pressure rise in front of the inlet) is frictionless. The practical limit seems to be set by external drag, i.e. flow separation as the excess air flows from in front of the inlet, to outward and around the inlet....something like this:

Inlet%20Radius.JPG


The aero guys call it spillage, although I think that creates a mental picture of air entering the inlet, reversing, and somehow flowing back out again. Whatever it's called, the cowl needs to be well rounded in the region surrounding the inlet, and as the inlet moves further outboard, further upward, or grows in diameter, there is less and less real estate within the frontal area envelope for shapely external curvature.

For external shape I look at the best radial engine cowls. In a previous thread, Steve Smith suggested looking at good fanjet inlets. I have no idea if this is optimal:

P7050006.JPG
 
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Hi Carl,

Well done for getting the James set up to work correctly with the small inlets.
All the reports I had read mentioned that with the small inlets they had had to except higher CHT's than they would of liked.
In the end,it was only after fitting the 6" rings that there problems were solved.
They also mentioned having to run Turbo Rail Injectors for stable LOP operation because of the higher Vi of the smaller inlets.

It does look good with the 14" spinner
 
Challenge accepted !

Hi Dan,

Looks like me and the " Dremmel " are going to be getting back together again!

So before I contact James Aircraft for a set of 6" rings,does anyone have a set lying around they would part with?
I am in Calgary for another two weeks.

Dan, you mentioned a while back about a 2 channel digital Manometer. I have found several expensive ones,but I remember yours was well priced ?
Can you supply the link ?

Also, how close to the prop can the intakes go ? I have read that 1/2" clearance is the go ?

Thank you to all that contribute to this amazing hobby !
 
Hi Carl,

Well done for getting the James set up to work correctly with the small inlets.
All the reports I had read mentioned that with the small inlets they had had to except higher CHT's than they would of liked.
In the end,it was only after fitting the 6" rings that there problems were solved.
They also mentioned having to run Turbo Rail Injectors for stable LOP operation because of the higher Vi of the smaller inlets.

It does look good with the 14" spinner

Have no clue on such reports. I run LOP 95% of the time. Cruise is 170+kts at 9.5-11.5 GPH depending on altitude. CHTs in cruise are below 380. I run a standard Van?s IO-540 but replaced 4 injector nozzles to get the GAMI spread down to 0.1GPH. At $26 a nozzle this is the cheapest thing you can do to make your engine a better performer.

Perhaps your reports are about an RV-10 with some fire breathing engine - or other issues.

There is no free lunch. A plenum enables you to get the most cooling for every pound mass of air coming in the engine. As such, you can reduce drag by reducing engine cooling air coming in. While the inlet rings have a roll in this, remember the cowl outlet is a big player. I did install louvers on the bottom of the cowl (not the Van?s stufff) to add some additional cooling.

Every element of my RV-10 was optimized for cruise efficiency. If you want an RV-10 to be a climb monster, installing a plenum no longer makes sense.

Carl
 
Ashley, you have air conditioning and a front governor? If I were you, I would take a real hard look at the Acclaim and TTx. Then I would think about how I might add glass structure inside the cowl for optimized flap sealing surfaces. I might even make some molded seals for perfect fit.
 
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Ashley,
Cheap mamometer is single channel, from eBay, about $35. Send an email and I'll send a white paper.

I don't remember how close the prop gets on mine.
 
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Every element of my RV-10 was optimized for cruise efficiency. If you want an RV-10 to be a climb monster, installing a plenum no longer makes sense.

A plenum lid is just a sealing device. The flight regime matters not at all; better sealing is always beneficial, regardless of how it is accomplished.

That said, better conversation of available dynamic pressure (largely an inlet function) and better sealing are most valuable in the low speed climb regime, where there isn't much dynamic pressure available, and power setting is high.
 
My concern would be the sealing of the oil access door to the top plenum. As the engine shakes around and the engine mounts sag, I would assume the sealing rubber would allow a small space to develop, and cooling air would be lost.
I also feel compelled to mention that on high compression IO-360's at least, cylinder temps in the 340's range and oil temps in the high 180's is easily obtained with stock Van's cowling and baffles.
 
My concern would be the sealing of the oil access door to the top plenum. As the engine shakes around and the engine mounts sag, I would assume the sealing rubber would allow a small space to develop, and cooling air would be lost.
I also feel compelled to mention that on high compression IO-360's at least, cylinder temps in the 340's range and oil temps in the high 180's is easily obtained with stock Van's cowling and baffles.

Here is how I did mine. The well seals around the engine dip stick tube and stays on the engine when you pull the plenum.
Carl
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Top motor mounts outside the plenum and baffles!

Carl, In the photos of your oil filler access, your plenum and aft face baffle stays in frot of the motor mounts. Any chance of a photo or two that shows a bit more detail on the aft vertical baffle and a side shot to show the hight of the plenum top / vertical baffles by the back 2 cylinders?

Anything you have is of interest.
Thanks!
 
Carl, In the photos of your oil filler access, your plenum and aft face baffle stays in frot of the motor mounts. Any chance of a photo or two that shows a bit more detail on the aft vertical baffle and a side shot to show the hight of the plenum top / vertical baffles by the back 2 cylinders?

Anything you have is of interest.
Thanks!
Some photos during fit up. Perhaps they show what you are interested in seeing. Note - I made the aluminum part of the plenum. Not too hard - just follow the handwritten instruction from James.

I ended up putting a 3/4" restrictor in each cabin heat SCAT hose as separate hoses was overkill, and just had the effect of bypassing engine cooling air to the bottom of the cowl. Even so, on the coldest days I just crack open the rear heat and leave the front heat off. If I was to do it over again I'd just have the one hose with a restrictor going to a Y, and then to the two heat muffs.
Carl
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WOW! This post is phenomenal. Love this data and details. AWESOME! Huge Thank you!

+1

Thanks Carl, that is exactly what I wanted to see.

There is a lot of really great tech info and help that gets buried in time, and needs to be presented new for the benefit of new builders.
 
These rings measure about 4 3/4” ID, but James list them at 4 5/8” ID. Here is the link: http://www.jamesaircraft.com/?page_id=11

Note the 14” spinner. While I understand Van’s desire to standardize across kits, the stock 13” spinner is, in my opinion, out of proportion on an RV-10.

Carl
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wow - somebody knows their way around a sanding block. That's some awesome prep and paint work there. The sanding dust was obviously rinsed off with sweat! Look at the light reflections and how straight they are. Hope mine turns out even close to that. Respect.
 
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wow - somebody knows their way around a sanding block. That's some awesome prep and paint work there. The sanding dust was obviously rinsed off with sweat! Look at the light reflections and how straight they are. Hope mine turns out even close to that. Respect.

I have to give credit to the quality of the James cowl. But - any RV-10 builder will tell you they cough up sanding dust long after first flight.

Painting the plane was much harder than I expected. While I tell builders to consider doing this themselves, I caveat with ?BUT HAVE HELP?.

Carl
 
Have no clue on such reports. I run LOP 95% of the time. Cruise is 170+kts at 9.5-11.5 GPH depending on altitude. CHTs in cruise are below 380....... I did install louvers on the bottom of the cowl (not the Van?s stufff) to add some additional cooling.

Carl, what is the typical mission climb...speed, mixture, power setting, and resulting temperatures?

What temperatures in an extended hot day WOT climb at 2700?

Can it fly at at 90 knots indefinitely? If so, how hot?
 
Can someone buy Dan H a 3d printer so he can start making inserts to test and continue his research?

Can we crowdfund that?
 
Carl, what is the typical mission climb...speed, mixture, power setting, and resulting temperatures?

What temperatures in an extended hot day WOT climb at 2700?

Can it fly at at 90 knots indefinitely? If so, how hot?

Normal is full RPM, Full Rich and WOT on take off, then 2500 after 2000'. On a 90+ day CHTs will top out at 410 on a hard climb, lower if I keep the nose down. Once above 3000' will drop below 400 and continue to drop with altitude. At 4000 I'm also leaning. I like to keep the climb between 120 and 130 knots.

While I do climb straight to 10K+ feet on a hot day, I don't do it at 2700 RPM.

I would never fly my plane continuously at 90 knots. I can report it does just fine in the pattern.

So what? I am pleased with the results of the mods I did to the plane. I'm sure other RV-10s will out climb it, but that was not the design goal.

Some screen shots:

First screen shot is after a hard climb out of Phoenix (100+ degrees) heading to Santa Fe.

Second is a typical cruise set up.

Third screen shot is the obligatory 25" and 2500 RPM ROP shot - just to see what it would do.

Build the plane you want,
Carl

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I would never fly my plane continuously at 90 knots.

The question is can you do it for a half hour, or an hour? See, there is a popular procedure called the Ripon approach, complete with lake holding...

Build the plane you want

Sure. What does this one do better than a stock cowl? What do you give up?

Can someone buy Dan H a 3d printer so he can start making inserts to test and continue his research?

Inserts for the inlets? Don't waste your money. Plenty of data out there.

Fig 5 from AIAA 80-1242R tells a lot about big holes in the front of a cowling. (The paper is available at the NASA documents server: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19980214918.pdf).

The researchers set up an entire engine nacelle and wing section in a NASA Ames wind tunnel. They tried three different inlet sizes (41, 61, and 107 sq in total) while measuring upper cowl pressure recovery (Cpu), and the variation in drag (Cd). None of the inlets had any sort of internal diffuser. The climb condition was about 100 knots (and 8 degrees AOA), while the cruise condition was roughly 160, close to typical RV speeds. Wc was an arbitrary 3 lbs per second mass flow, a reasonable ballpark for our Lycomings, set by throttling the flow downstream of the inlet as necessary. The scale across the bottom is inlet ratio, 0.2 being (for example) an inlet area 5x the area of a 3 lbs per second stream tube...a very low Vi/Vo inlet.

There are a number of interesting observations to be made, but here I'll stick to just two key points. First, without good internal diffusers, pressure recovery (Cpu) takes a dive as the inlet ratio is increased. In the 0.6~0.8 range it's is truly awful; the addition of internal diffusers is mandatory at those ratios, and here you see why. However, look how good Cpu is at low inlet ratios, with a very steep rise for the climb condition between 0.4 and 0.2. That performance comes without internal diffusers to complicate design and fabrication, just big holes.

Take a survey on any flightline, and you find the usual objection to big holes is drag. However, take a look at the lower plot; the Cd lines are almost flat across a wide range of inlet ratios. For the same cowl and mass flow, inlet size actually has very little relation to drag.
 
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