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  #11  
Old 02-03-2013, 06:43 PM
Wesael's Avatar
Wesael Wesael is offline
 
Join Date: Feb 2009
Location: Brooksville
Posts: 282
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Quote:
Originally Posted by RV10inOz View Post
Its interesting stuff drag, because you can't see or measure it, well not easily in flight apart from speed.

I have a stubby Transponder, 2 x VHFs, GPS, Stormscope (huge) and the VOR/ILS rabbit ears in the tail. They will be all huge drag items for sure.

Spinner drag is an interesting one, and a very good point. I might have a look at that a bit closer and investigate sealing it.

We noticed about 4 knots in removing the tie down rings alone.
There are a few things that we did different very early in the build trying to get the most speed possible in a practical manner. I was not out to make an all out race plane but something that I can use and service in a practical manner.

The cooling system was modified using a plenum with fiberglass transitions molded to capture all of the air and force it into the plenum without leaking into the lower cowl.




Under the engine we tried to provide a transition to smooth the airflow flowing out the exit side of the cowl. (not shown in the pics. all of the gaps were sealed with RTV)




This along with a modification to the lower cowl to slightly increase the outlet area provides enough cooling to keep the engine cool without using the factory "louvers" under the cowl. I think they are draggy but the effects are unknown to me.

We closed all of the ends on the control surfaces.



Closed the hinge gaps like this



Also we sealed every hole that we could find in the wing root area. control rods, spar web gap etc. This is to keep air from in-filtering from the tail and exiting the low pressure area in the wing root and door area..

The wheel fairings are extra tight around the tires.

I only have 1 comm antenna on the belly and 1 transponder blade. the rest of the antennas are internal.

I ordered new ECI cyl's that were flow matched. worth it? i dont know..

The area that Pierre talked about on the spinner is cut very close to the blades.

The spinner is very close to the cowl (really its to close but its not rubbing so i left it like it worked out).

It is not really 1 thing that makes airplanes go faster. It is a lot of small things that finally add up.

Also note that I accept a slightly higher CHT that some do. My limit is 400 F in cruise so I MIGHT be accepting accelerated engine wear due to heat???? In my case I accept the risk--not for everyone.
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  #12  
Old 02-04-2013, 01:32 PM
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J Twilbeck J Twilbeck is offline
 
Join Date: Oct 2012
Location: Huntsville AL
Posts: 145
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Wow that's fast. Good work! I will definitely keep these in mind later on in my build!

Thanks!
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Last edited by J Twilbeck : 02-04-2013 at 01:36 PM.
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  #13  
Old 04-12-2018, 11:42 AM
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Bill Boyd Bill Boyd is offline
 
Join Date: Sep 2006
Location: Landing field "12VA"
Posts: 1,108
Default Great time for me to ask about this!

Quote:
Originally Posted by Wesael View Post

We closed all of the ends on the control surfaces.


This would not be hard to do right now since I'm glassing in the control surface FG tips. I've considered it on the -6A for 20 years but never gotten around to it. Seems like a no-brainer on the -10 project, but I thought I'd ask if the weight/cost/time is worth it. Is there an extra knot to be gained doing "this one weird trick" by itself, maybe?
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  #14  
Old 04-13-2018, 06:00 AM
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Weasel Weasel is offline
 
Join Date: Dec 2012
Location: Brooksville, MS
Posts: 717
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Quote:
Originally Posted by Bill Boyd View Post
This would not be hard to do right now since I'm glassing in the control surface FG tips. I've considered it on the -6A for 20 years but never gotten around to it. Seems like a no-brainer on the -10 project, but I thought I'd ask if the weight/cost/time is worth it. Is there an extra knot to be gained doing "this one weird trick" by itself, maybe?
Few things.....make sure whatever you use to fill from the last rib to edge is not something heavy and will not turn to powder (some types of foam). One posible idea is use balsa wood secured with a large area fender washer bolted to a plate nut in last rib then covered in fiberglass. Understand the risk! If something comes loose you could have a jammed control and go down.

Also consider mosture intrusion. If you get any moisture inside an enclosed cavity it will freeze and swell at altitude!
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RV-4 715hr Sold
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Fisher Classic Cassler Power VW sold
RV-10 N7631T 820hr Sold
RV-8 700+hrs
Carbon Cub 200 hr Sold
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Last edited by Weasel : 04-13-2018 at 03:17 PM.
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  #15  
Old 04-13-2018, 07:54 AM
Tom Martin Tom Martin is offline
 
Join Date: Jan 2005
Location: Ontario, Canada
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The best speed test is to fly beside another aircraft at known power settings, then matching speeeds. Now make your change, one at a time, then fly with the other plane , same power settings and compare. Speed gains, or losses, can be seen. Any other method requires multiple runs and temperature corrections.
For me this was the quickest, most reliable method of checking speed mods.
I flew countless four leg trials before I realized that horsepower at different temperatures had a big effect on speed. Data without horsepower corrections due to temperature change are unreliable, useless was my experience.
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2010 SARL Rocket 100 race, average speed of 238.6 knots/274.6mph
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  #16  
Old 04-15-2018, 12:18 PM
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aturner aturner is offline
 
Join Date: Jan 2005
Location: Clarion, Pennsylvania
Posts: 496
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There is always some error when measuring airspeed, so it can be difficult to determine the effect of an individual modification. Just because we canít measure it doesn't mean it doesnít have an effect, it just tells us that the effect is smaller than our measurement error. But the cumulative effect of many small individual tweaks and attention to details can be significant. Bottom line for me is to use our understanding of physics to make small tweaks that should improve airspeed, and not worry too much about measuring their individual effects.

Weasel, now that this old thread is revived, I got to say that I really admire what you have accomplished with your -10. It really shows what a stock setup can do when you focus on the right details.
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