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  #11  
Old 12-12-2016, 06:19 AM
frghtdg frghtdg is offline
 
Join Date: Feb 2016
Location: Boynton Beach, Florida
Posts: 62
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Quote:
Originally Posted by brad walton View Post
Sail plane pilots have debated waxed vs. unwaxed vs. very light crosshatch pattern on wing surfaces. My recollection is a light crosshatch sanding with 400 wet/dry sandpaper produced a measurable increase in the amount of laminar flow.
Recall also a smooth golf ball won't carry as far as a dimpled ball.
A little orange peel in the paint surface may actually be beneficial.
All true above, but don't start sanding yet. High performance gliders (fiberglass) are covered with gelcoat that is contoured and sanded by hand for hundreds of hours to an extreme tolerance of less than .003" deviation (wing).
Gelcoat and water/humidity don't mix and because it cost over 25K$ to refinish we wax it. Less than 3 do not because they believe the slight improvement in performance gives them an edge racing. So they sand with 4' aluminum sanding blocks and check the wings profile with a wave gauge to achieve <.003. A lot.
Everyone else waxes the **** out of it to ward off the devil.
Because smooth is sticky, we apply turbulator strips spanwise on the underside 'near' the trailing edge to help with airflow separation . Location is determined by wind tunnel testing. Why new glider = 160K$ +++

What improves our glider performance more, and I plan to apply this to my 14, is we do everything we can to reduce/eliminate/control where cockpit air escapes or leaks. Canopy and wing roots (via fuselage spar openings) escape are very high drag producers.
So, we seal the best we can by glueing material over openings, attaching flexible boots to pushrods , thin foam to canopy frames.
Most important is we give the air inside a place it wants to go, the tail. An exit as far back as possible in the belly so the escaping air does not impact a tail surface. A NACA vent perhaps. This means louvers in the aft cabin bulkhead.
Or go slow....less drag.

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  #12  
Old 12-12-2016, 06:34 AM
6 Gun 6 Gun is offline
 
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With out a doubt the way to go faster is Horse Power more faster less slower!
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  #13  
Old 12-12-2016, 06:39 AM
frghtdg frghtdg is offline
 
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Location: Boynton Beach, Florida
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Going fast while sipping gas.
H
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  #14  
Old 12-12-2016, 07:52 AM
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DonFromTX DonFromTX is offline
 
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Location: La Feria Texas
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A few years back I purchased a Cherokee with the worst paint ever, sort of a badly oxidized almost satin finish, absolutely no shine whatever.
I had it painted (with Imron) and will never forget the difference it made in the plane, not only speed increase but gave it a "slippery" feel in the air as well.
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  #15  
Old 12-12-2016, 09:47 AM
tal454 tal454 is offline
 
Join Date: Feb 2015
Location: Sacramento, CA
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Orange peel may not necessarily be a bad thing. I think myth busters applied a golfball like texture to a car to see if the gas mileage would increase due to the physics of a golf ball. The results were the car saved gas with golf ball like dimples. Even with the added weight.

Now how that translates to a smaller scale with orange peel like texture I don't know.
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  #16  
Old 12-12-2016, 10:25 AM
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grubbat grubbat is offline
 
Join Date: May 2012
Location: Ga
Posts: 662
Default Lot of time

I spent a lot of time and effort getting the right size orange peel in my paint job along with some nats and other flying critters. At between 1000ft and 20 ft, she looks great. However at 1 ft, I get a craving for bacon and eggs to go with my orange skin. 😜
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  #17  
Old 12-12-2016, 11:43 AM
David Paule David Paule is offline
 
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Location: Boulder, CO
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I suspect that the deformation of the skin in between the ribs causes higher drag than poor paint jobs can achieve.

Dave
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  #18  
Old 12-12-2016, 01:41 PM
deek deek is offline
 
Join Date: Mar 2013
Location: Flathead Lake Montana - 8S1
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Klaus Savier (LSE electronic ignition) has years of documented, instrumented testing of surface finish on his highly modified Varieze and LongEZ. NO ONE goes faster on less horsepower than Klaus; good luck in getting him to talk about what he's learned.

Anyone, however, can carefully inspect the finish of his planes, especially the canard, wings and winglets. Very interesting
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  #19  
Old 12-12-2016, 05:57 PM
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Alan Carroll Alan Carroll is offline
 
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Location: Madison, Wisconsin
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The CAFE Foundation actually tested the effects of waxing on speed of a Mooney some years ago (see Wax Job). They found a gain of 3 mph.
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  #20  
Old 12-12-2016, 08:07 PM
Turbo69bird Turbo69bird is offline
 
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Location: CT
Posts: 284
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There's been some interesting info on intake manifold design. I remember they did a test with a rough rasp on the bottom of the intake port(side to side ) and showed how it helped keep, fuel in suspension especially in carberated engines, in testing it was much better with the turbulence than the smoothed polished ports which was what was Done previously.

I realize this is very different than the flow over a wing I just thought it was interesting information.
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