Cowl Exit Streamlining

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PMD

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You'll only really know how successful you are with any approach by flight testing and instrumenting the cooling exits for velocity before and after mods. If you increase exit velocity in cruise and it still cools ok in the climb, you've made it better.

Toobuilder was able to shrink the inlets and exits, almost certainly reducing drag as compared to before

Most other guesses here are just guesses...
I think MOST engine installations at least start with nothing more than a bunch of guesswork. The secret is to extract as much fact from the fancy to make those guesses WORTH testing and development.
 

TFF

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Everything has a starting point, and everything gets to the point of good enough. That is a sliding scale. There is no end point of perfection.
 

lakeracer69

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Dec 10, 2008
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New Hampshire
You people try to make mountains out of molehills, The shop that I work at has two RV-10's that we have done multiple yearly condition inspections on both. Neither one has had any cylinder or high heat problems. There is a Service Bulletin about the lower rudder hinge that we keep our eyes on though. If you need to set up a Manometer to make yourself feel better ( Irrespective of CHT and EGT gauge readings) go for it. That's why they call it experimental.

YMMV
 

rv6ejguy

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You people try to make mountains out of molehills, The shop that I work at has two RV-10's that we have done multiple yearly condition inspections on both. Neither one has had any cylinder or high heat problems. There is a Service Bulletin about the lower rudder hinge that we keep our eyes on though. If you need to set up a Manometer to make yourself feel better ( Irrespective of CHT and EGT gauge readings) go for it. That's why they call it experimental.

YMMV
Kyle is trying to find a couple more knots and retain the present cooling margin. Nobody said they didn't cool.

The manometer would show pressure differential but we're more interested in exit velocity relating to momentum loss and cooling drag here.
 

lakeracer69

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I wish I had learned this saying years ago. "Perfection is the enemy of good" It would have saved me a lot of past wasted time.
I do get the "strive for better", but sometimes it is a futile pursuit.
 

TFF

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I don’t think it’s fruitless, if you are in the mood to experiment. Toobuilder is always trying something. If you got the time and willing. If the mission is to get it over with, then hoping quick fixes are all you need probably are a waste because it’s all about going deep. Nothing on your Lil Bitts looks like time to get it over with. Just different stages of the game.
 

Toobuilder

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Dave Anders and his RV-4 is probably one of the best examples of an ongoing journey of learning. He will research, theorize, modify, test, collect data, and weigh results on his little airplane. He's been doing this for 25 years and its a big part of his enjoyment with flying. I totally get it. Sometimes the search for "better" does not get the results you expected (and sometimes you go backwards), but the process sure is fun for some of us. Dave has an incredibly fast RV, but it did not come out of the shop that way. But now that he has this vast knowledge base, I'll bet his next RV rolls out of the shop pretty well close to optimized first time out.

WRT augmentor tubes, If my neighbors RV-10 wasn't so far along in the build process I'd be working with him to duplicate my setup on his. As far as I'm concerned, that idea is a "keeper".
 

rv6ejguy

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I wish I had learned this saying years ago. "Perfection is the enemy of good" It would have saved me a lot of past wasted time.
I do get the "strive for better", but sometimes it is a futile pursuit.
I found about 4 knots plus better cooling margin on my RV by re-designing the cooling system. Learned a lot and worth the effort in my view.
 

Victor Bravo

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KWHP, Los Angeles CA, USA
The mental and intellectual exercise of improving the airplane, taking on a complex or technical challenge, is part of the hobby for many people. Whether it gives you two or three knots may not be the real reward, it may be that you fought your way through a problem, solutions, obstacles, and tested ideas you came up with.

People who do crossword puzzles aren't doing them because they need 50 more words in their vocabulary, and people don't lift weights because they really need to move the weight to another location :)

I can only guess that engineers and technical people get the same joy out of working toward a performance improvement on an airplane, whether or not they get the three knots.
 
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