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RV10 Plenum.

Richard Connell

Well Known Member
Some people PMd and asked me to show some more pictures of my plenum.
I have a Barrett IO-540 with CAI, 9:1, showplanes cowl and a Hartzell 3 blade.

When I built my RV7 I never really enjoyed the fibreglass aspects of the build.
It wasn’t difficult, I just never warmed to it.
As the RV10 canopy loomed in my future I was quietly dreading it.

Anyway, after many many months (maybe even years) it was finally done, and I had learned some new skills in the process. Thats what its all about right?
So I decided to build some internal centre console tunnel parts as well which turned out better than I had expected.
So I thought Id try my hand at building a plenum for my engine.

Brief summary: I layed up the basic shape using the top of the cowl as a mold.
I then made some balsa/glass edges. Glued them all together and formed a solid plug that mimicked the final shape sitting on the engine.
In order to seal around the dipstick I formed a well in the top of the plenum.
I finished it up nicely with some 2k primer and topcoat then took a mold off it.
Finally I used a vacuum resin infusion process to pull a part from the mold.
It came out pretty good first go. A few minor flaws which were relatively easy to fix.

I had some larger intake rings machined - with rounded ridges to wear better long term. Floxed them into the cowl halves waxed.
Then made up some ducts from the rings to the plenum and attatched them to the plenum.
I 3d printed up a sleeve to attatch to the dipstick top which screws into the oil door well bottom.

Still need to join the rings to the duct with some sleeving. Its on the long list of minor jobs which seem to take a lot longer to get done once flying.

Id hate to think how much time I put into it, but if seems worth it now that its done, and I learnt a lot along the way.

The plane comfortably meets book values or a few Kts quicker.
I probably set my expectations too low for this plane TBH. My benchmark was equivalent performance to the 7 - I expected the 3 blade to hurt cruise performace.
Its much better than I expected.

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Richard,

Very nice work.

Did you use the standard Van’s baffles for the side aluminum pieces? For the plenum I made for my first RV-10 I had to fabricate those parts out of aluminum sheet - I’d rather not do that again.

Carl
 
Well Done Sir . . .

Nicely done!! Bravo! - the vacuum resin infusion is not so easy to get perfected, I made 4-5 before getting it right. Love the carbon look! This took me 6 months.

Do you have any more photos on the inlet-to-plenum diffusers?

Bill
 
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Nicely done!! Bravo! - the vacuum resin infusion is not so easy to get perfected, I made 4-5 before getting it right. Love the carbon look! This took me 6 months.

Do you have any more photos on the inlet-to-plenum diffusers?

Bill

Bill,

If you are ready to make a plenum for the 10 similar to the ones you made for the 7 - I’ll send you a check today!
 
Nicely done!! Bravo! - the vacuum resin infusion is not so easy to get perfected, I made 4-5 before getting it right. Love the carbon look! This took me 6 months.

Do you have any more photos on the inlet-to-plenum diffusers?

Bill

Thanks Bill.
I have to confess that your RV7 plenum which I saw on my good friend Cams engine was the motivation for me to attempt this. It looks fantastic.
I think I got lucky getting a result on my first infusion. I had made some engine mount bolt covers just before so I had some idea of what I was doing. 6m sounds about right. COVID project....we were locked down on and off for a while.

I hacked up the inlet ramps supplied with the upper cowl and appended them with spray foam and bog etc until I was happy with the transitions then cast a part of them. I then glassed them to the plenum top. Then I reinstalled my Governor cable bracket and made further modifications. :eek:
The sides of the ducts I used hinges to attach to the ramps which worked out well.

Carl - Yes just the standard vans baffles trimmed to give me a 1/2 -3/4 clearance all round. Maybe a bit more in the corners.

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Pretty work!

Richard, what are the inlet diameters?

Kind words Dan. I have taken much inspiration from your work. I am thankful for your sharing.

The rings are 6.5" or 165mm OD.

I bought some 6" James rings initially, but I was nervous that it wouldn't be big enough esp with the extra HP of 9:1 and the lower 25% being taken up by the intakes.
I actually wasted a week or more copying (poor imitation - no photos!) your ram air FAB. That would have allowed the smaller intakes. Eventually I decided that it would look horrible on the bottom of the cowl as the throttle body is too far fwd.
So I had a local machine shop make up the new rings for me.

I had the ridges rounded off as I figured this would make install and removal a little easier.

PS i have 2x 6" rings for sale if anyone wants them.

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Kind words Dan. I have taken much inspiration from your work. I am thankful for your sharing.

Thank you, and you're entirely welcome.

The rings are 6.5" or 165mm OD.

OD or ID?

Do I understand correctly, you're currently flying without a sealed joint between the aluminum ring and the plenum entry duct?
 
Looks like nice work Richard. Especially the effort you have in the tooling. Hope you can crank out some duplicates to sell and maybe return some of that investment.

Are you flying now, and if so, can you offer up performance numbers on the induction scheme? After taking pressure measurements in flight (Rocket) it appears that I will see essentially the same MP if I draw from my cooling inlets as I do with the dedicated FAB/chin scoop. And, I fully expect to see a slight loss in cooling which is desired. I overcool now, and this saves me from making smaller rings.
 
Welcome to the world of composites manufacturing -- which is pretty different from fitting and gluing existing composite parts together, filling pin holes, etc.

We have learned over and over that time spent making good plugs and molds pays dividends. Higher quality parts with less 'body work' time spent later, and as soon as you need to make a second one, all that time just paid for itself.

You are brave and adventurous to try the resin infusion. Not many folks get a good part on the first pull, and wasted materials for trial and error adds up. We have stuck to wet hand lay-ups with vacuum bag.
 
Thank you, and you're entirely welcome.



OD or ID?

Do I understand correctly, you're currently flying without a sealed joint between the aluminum ring and the plenum entry duct?

That is correct, OD. Which isn't much help! I just had an old ring at my desk to measure. Its a 6" ID ring.

The seal....
I haven't got a seal on as yet. Its a long story. I have some neoprene, and attaching to the ring is straight forward.
However, the plenum/intake combination is difficult to attach the seal to without gluing it. Which has its own maintenance issues. So I've put this off for now while I try and come up with a solution. Suggestions welcome!

I accept that this is necessary for optimum performance so I will address it at some stage. LOP I'm seeing CHTs in the 330 to 350 range so I'm not too stressed about it as yet. I suspect that once sealed up properly I will indeed have excess cooling. So I may then address the exit.

If the cowling was 2" longer then the intake scoops would be longer and have a much better geometry and a flange could be incorporated onto that to clamp the seal to. I have it as far forward as practical. Only 1/8 spinner clearance and a split lower cowl.

Ive heard someone has extended their SP cowl 2" and put an extended hub Hartzell on in order to make more room for the aircon compressor. This setup would be ideal for a few reasons. The intake system is a tight fit. I have some minor rubbing to adress. Another benefit is that the extended hub makes for a nice place to rest a prop shaft seal as well. I haven't been able to conceive a method for that with my combination of compact hub and SP cowl.

Performance wise, Michael, Ill investigate measuring some pressures in the future.
I still have a long list of little jobs to get to first.
Like I said at the start, my aim was to meet Vans performance numbers even with a 3 bladed Hartzell. All the anecdotal data pointed to there being a meaningful penalty. It seems I have achieved that, but who knows where I've made it up. I still feel there is a little more low hanging fruit to pick too.
 
The seal....
I haven't got a seal on as yet. Its a long story. I have some neoprene, and attaching to the ring is straight forward.
However, the plenum/intake combination is difficult to attach the seal to without gluing it. Which has its own maintenance issues. So I've put this off for now while I try and come up with a solution. Suggestions welcome!

This is interesting. Don't recall ever seeing a Showplanes setup with the cowl off. What does Bryan specify for sealing those inlets?

I accept that this is necessary for optimum performance so I will address it at some stage.

Oh yeah.

I asked about ring diameter because with the relatively sharp change of section immediately aft of the inlet rings, they really need to be operating as low Vi/Vo inlets. That means external diffusion, i.e. the conversion of dynamic pressure to high static pressure takes place mostly out in front of the inlet. No seal means the gap is bleeding high pressure.

Which brings a suggestion to mind. A low Vi/Vo inlet doesn't actually need a duct faired to it aft of the inlet ring. Sure, a nicely shaped one, with moderate diverging angles, might pick up a bit more pressure, but most applications don't bother with it. Take a look at a Mooney Acclaim (below), or a Cessna Corvalis (formerly the Lancair-built Columbia series), or even an ordinary Cessna 172 (again, photo below). They all use a front wall sealed to the cowl, not the inlets...which you might consider.

BTW, in such an arrangement, your dual filter elements would be within that volume in the nose of the lower cowl, so the upper duct section would be eliminated. See the intake location on the Acclaim below.

Good illustration of low and high Vi/Vo inlets: http://www.n91cz.net/Interesting_Technical_Reports/106-111_BuildingBasics.pdf
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....Performance wise, Michael, Ill investigate measuring some pressures in the future...

Thanks for that. Not looking for laboratory grade data here (unless you have it handy), rather, Im just wondering how your airplane compares with other RV-10's when looking at MP at cruise. Do you pull more MAP at full throttle or less than your buddies in the same air?
 
Pretty work!

Agree on this. Very nice work. Great timing as well. I have 145 hours on my 10 with a Thunderbolt IO540, horizontal sump, showplanes cowling. I originally (and currently) sealed my cowl with baffle seal. While I am using the showplanes cowling I am actually not using their snorkle. With the lycoming sump and a Airflow FM-300R I just could not get the angles right. So I punched out a hole in the lower cowl and built an airbox. In doing this, this gives me the full 6.25" inlets for cooling air. I custom built some carbon fiber ramps for the transition, but it is by no means "sealed" the way I wanted it...

My cooling is actually not bad, but I have never been fully happy with what I have. At the time I just wanted to fly and it was good enough. Just last week I started drawing up a plenum that would seal to the inlets. I had an email in my draft box about the SJ 6.25 inlet rings, but with Dan's email about the Columbia baffling now I have to go think about that. However, I think my problem is probably easier than yours now because I am not stealing 1/3 of the inlet for the intake.

I will post photos here as I work my way through it.
 
Good illustration of low and high Vi/Vo inlets

DanH, you wouldn't happen to have any more photos on the Columbia? I realize that is feeding a turbo setup, but now that has me thinking a bit more about my setup. I punched a hole in my showplanes cowl for my fuel servo (and airfilter), but in this setup I could possibly keep all my things inside of the cowl and seal that hole back up.
 
Agree on this. Very nice work. Great timing as well. I have 145 hours on my 10 with a Thunderbolt IO540, horizontal sump, showplanes cowling. I originally (and currently) sealed my cowl with baffle seal. While I am using the showplanes cowling I am actually not using their snorkle. With the lycoming sump and a Airflow FM-300R I just could not get the angles right. So I punched out a hole in the lower cowl and built an airbox. In doing this, this gives me the full 6.25" inlets for cooling air. I custom built some carbon fiber ramps for the transition, but it is by no means "sealed" the way I wanted it...

My cooling is actually not bad, but I have never been fully happy with what I have. At the time I just wanted to fly and it was good enough. Just last week I started drawing up a plenum that would seal to the inlets. I had an email in my draft box about the SJ 6.25 inlet rings, but with Dan's email about the Columbia baffling now I have to go think about that. However, I think my problem is probably easier than yours now because I am not stealing 1/3 of the inlet for the intake.

I will post photos here as I work my way through it.

Jeff,

Interested in your use of the FM-300R instead of the FM-200. Don at AFP recommended the FM-200 for my cold air sump IO-540 order.

Also I’m working a filter box for the RV-10 James Cowl so very interested in your airbox photos and dimensions.

Carl
 
DanH, you wouldn't happen to have any more photos on the Columbia? I realize that is feeding a turbo setup, but now that has me thinking a bit more about my setup. I punched a hole in my showplanes cowl for my fuel servo (and airfilter), but in this setup I could possibly keep all my things inside of the cowl and seal that hole back up.

Sorry, no good Columbia/Corvalis baffle pictures on my hard drive, just the green exterior below. Conceptually it will be similar to the Acclaim (below), or for that matter, a Glasair Sportsman.

Some call it a Continental style baffle. Mark Frederick is running the setup on his Rocket. Ask him how well it works.
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I know this is getting way off topic, but the cowl to inlet transition seal has always bugged me. That led me to try the Rutan "Boomerang style" inlets that are fixed to the engine and move independantly of the cowl. I have to say, I am very happy with their performance. If I was to do a 10, it would have these inlets.
 
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Jeff,

Interested in your use of the FM-300R instead of the FM-200. Don at AFP recommended the FM-200 for my cold air sump IO-540 order.

Also I’m working a filter box for the RV-10 James Cowl so very interested in your airbox photos and dimensions.

Carl

Thunderbolt picked it up when they built the engine. I had a little back and forth with Don when I received the engine and at that time he would have let me exchange it but recommended that I actually run it. In retrospect I think I recall the 300 being a little longer and setup for a silicone pipe so that change is probably what actually drove me to a bunch of work due to going to a different intake setup.
 
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