Cowl Inlet Design. How does this one work? LOOKS COOL!!

[rv969wf]

After looking at many cowl inlets shapes, round, rectangle, annular, etc. etc. I'd like to know how the design on Sean D. Tuckers highly modified airplane works. His system appears to be a downdraft design with a large lower cowl outlet and two side cowl outlets. I was wondering how they came up with this design? I'm assuming it works or they would not of designed it the way it is. This design reminds me of the annular cowl design like on the Reno Racer 'Rare Bear', but that airplane has a radial engine. I'd like to hear some comments about anyone's thoughts on this design and why are there so few cowl inlets designed like this. I actually like the looks of it, maybe because it's different and not normal looking like everything else, very clean and I like the shape. Anyone interested in experimenting and changing the looks of your RV into one looking like S.D. Tuckers would have a one of a kind. VAN and others might frown,,, but hey it's a free world. It also reminds me of how turboprop airplanes are designed with the same shape inlet for the turbine engine. After looking at the design, I could see how the stock RV cowl could be more profiled and not so blunt on the sides. No I'm not going to whack my cowl up and try it as my very small round cowling inlets are working great! I'll let someone else experiment on this one.

Bob Axsom, does this give you any ideas??? I also added the next post with the Reno racer to give you some ideas with your search for cooling drag reduction. Hope some of these ideas help.
I don't think the annular design is for racing purposes as S.D. Tuckers plane is for Aerobatics and not speed/racing.

[rv969wf]

Here's another cool cowl system, except this one is designed for speed since it's a Reno Racer I'm assuming. Notice the updraft cooling system and the cowl outlets are on the top of the cowl. Both pictures you can see the upper cowl outlets with louvers, very interesting.

Just a thought, but the updraft cooling with the cowl outlets on top might help keep the windshield defrosted in the winter time, LOL....

Off the subject of cowl designs, but notice the second picture of the Reno Racer, the right wing tips are different than the left ones.

[gmcjetpilot]

Originally Posted by rv969wf

After looking at many cowl inlets shapes, round, rectangle, annular, etc. etc. I'd like to know how the design on Shawn Tuckers highly modified airplane works. His system appears to be a downdraft design with a large lower cowl outlet and two side cowl outlets. I was wondering how they came up with this design? I'm assuming it works or they would not of designed it the way it is. This design reminds me of the annular cowl design like on the Reno Racer 'Rare Bear', but that airplane has a radial engine. I'd like to hear some comments about any one's thoughts on this design and why are there so few cowl inlets designed like this. I actually like the looks of it, maybe because it's different and not normal looking like everything else, very clean and I like the shape. Anyone interested in experimenting and changing the looks of your RV into one looking like S.D. Tuckers would have a one of a kind. VAN and others might frown,,, but hey it's a free world. It also reminds me of how turboprop airplanes are designed with the same shape inlet for the turbine engine. After looking at the design, I could see how the stock RV cowl could be more profiled and not so blunt on the sides. No I'm not going to whack my cowl up and try it as my very small round cowling inlets are working great! I'll let someone else experiment on this one.

Bob Axsom, does this give you any ideas??? I also added the next post with the Reno racer to give you some ideas with your search for cooling drag reduction. Hope some of these ideas help.

Sorry I am not Bob but I slept at a Holiday Inn Express last night.

Its call an annular inlet, and a piece of trivia, Van has already done this. The original prototype RV-6 (the all ford blue one 1987 time frame) had a similar single lower annular inlet. The bad news is Van's experiment found cooling was marginal (read terrible). He went back to the RV-4 design.

The area NEAR the spinner is terrible with a stock GA prop and spinner. The reason is obvious if you look at the root of the blades, where they come out of the spinner and for the first 5 inches; they are blunt clubs that beat the air to death. (Note: picture below shows yarn going backwards near spinner, second picture shows low drag axisymmetric inlets, aligned with the cylinder where you need cooling and away from dirty spinner air. Who da thunk? )
(click)

Remember an acro plane is all about slower speed often and pulling G's at high angle of attack, so this lower smiley face may be fine or even beneficial at high angles of attack. He's not going for top speed. That is also A LOT OF AREA. This is not a low drag design. Also he's in show business and going for looks, its a show plane, so cool looks are cool (no pun intended).

Check out Cafe Foundation Org for their research if you have not already. They tried this with a Mooney. They also super sized the spinner and it look really odd. You have to look up the report (Local Air Flow Control II) to see what their conclusion was. Actually, there was no real conclusion. The problem is, in my opinion, you have to go to up-draft cooling (as you mentioned); than where do exit the air, at the windshield where there's a huge pressure gradient? No. If you try to stay with down draft, ducting from the scoop to the upper cylinder plenum becomes problematic. My friends Navion has updraft. It has its charm, but who want oil all over the windshield and top of the plane and more drag. Tony Bingles has a chapter on the differences.

(Note: the gigantic spinner to cover up the blunt blade roots.)
(click)

[rv6ejguy]

Peter Garrison's Melmoth uses updraft cooling but I think he said he couldn't note much difference.

In the case of the biplane racer pictured, well pretty hard to argue with the winning result. That's Paul's prop if I'm not mistaken BTW.

Ducting of an annular intake to feed an air cooled engine would be harder. You'd also have more trouble sealing baffles or a plenum around intake and exhaust pipes- no fun and more leaks and you'd be adding exhaust heat from the pipes to the cooling air stream.

Picking up air just around the spinner circumference is maybe not great according to the CFD plots on an RV. This is an area of relatively low pressure compared to where the existing inlets although reprofiling the cowling would change this to some degree. Updraft cooling with top cowling exits could work as there is low pressure over the whole cowling top, pressure does not rise above median until just behind the firewall.

Overall probably not worth it on an RV and Lycoming engine. I think the original theory was that hot air rises and that updraft cooling would take advantage of this natural convection. In practice, on RV it would probably work worse.

[Yukon]

Updraft cooling bathes the cylinders in the 1400 degree heat of the exhaust pipes rather than venting it down and out the lower cowling where it belongs.
Piper Saratoga had it and it ran hotter than the Cherokee 6. What's the point?

[rv969wf]

[IMG]

Originally Posted by Yukon

Updraft cooling bathes the cylinders in the 1400 degree heat of the exhaust pipes rather than venting it down and out the lower cowling where it belongs.
Piper Saratoga had it and it ran hotter than the Cherokee 6. What's the point?

[/IMG]

I totally agree with everyones comments and if somethings works why change it.

So can someone tell me, what is the Reno BiPlane Racer gaining with the updraft cooling?

[rv6ejguy]

Winning Reno racers rarely have anything on them that wasn't an improvement in the speed department compared to what they had before.

[pierre smith]

Originally Posted by rv969wf

[IMG][/IMG]

I totally agree with everyones comments and if somethings works why change it.

So can someone tell me, what is the Reno BiPlane Racer gaining with the updraft cooling?

Hi Alan,
Since heat rises, these guys try and take advantage of that fact and duct it upwards since that's what the air wants to do anyway. Hot air being thinner than cool air, they send it over the canopy and the wing strut since hot air creates less drag than cool air around these protruberances....or so I was told by an old F-1 racer.

Rivets (F-1 owned by the late Bill Falck) was the best example that I've ever seen of a well done updraft system. The only intake for cooling air and the carb was under the cowl, about where an RV's intake is, then carefully routed up through the cylinders and over the top of the engine and ducted back down to exhaust a lot like your RV is. The air was directed from inlet to outlet with custom made ducting and sealed tight. There were no openings for cooling like we have, just radiused closed cowls. He blew the competition away for years until some radical stuff showed up but he had died already.

Pierre

[rv969wf]

Hi Pierre,
Do you or anyone else have any pictures of the (F-1) that you mentioned above? I'd like to see it if possible, the cooling system mostly.

Another question: Does anyone know where the exhaust exits on the RENO bi-plane in the pictures I posted earlier?

[DanH]

Ross, are those RV CFD plots posted somewhere?