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Cowl
Well, I have a pressure plenum, so all the high pressure is in there. When it exits into the cowl, you really want a pressure drop so the air gets sucked out. In my case, the high pressure from the plenum goes into the cowl volume, and since the cowl flap is reducing the exit, the pressure builds up, and yes, it increases exit velocity, however obviously, the inlets will supply as much pressure as they can, and what I need to do, is to seal the oil door and make sure the latch works properly.
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Yes, I agree, you are correct.
My door was made quite stout with Carbon stiffeners. I checked it today and it is pretty stiff.... I might have to add some more stiffeners though. Still a little disappointed that it didn't do anything for the performance at the lower altitudes, but higher up it will :) |
Hakan would you please share some pictures and details of your cowl flap. Is it electrically or cable actuated?
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What is the rationale for 'negative reflexed flaps and ailerons'. Wouldn't that tend to raise the nose? Why would that lower drag or increase speed?
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flaps
Negative reflex is a strange term....as that implies that the flaps and ailerons would move trailing edge down....
Anyway, the reflex moves the nose up a tad and actually reduces wing shape drag. The big issue however is that there is always a point when shape drag of the fuselage will be higher then the shape drag of the wing. It is seems though, though my flight tests that even with a slight nose up of the fuselage ( and aircraft) the reduced drag of the wing wins. It could be that our RV's are flying a tad nose down to begin with... Regarding the cowl flap, I will check to see if I have any pics. It is controlled by a vernier cable and closes beyond nominal and have cutouts for the exhaust pipes. |
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This at: WOT (76% PWR), 9.8 GPH, 1605 lbs, 84.1" CG (some aft of center CG) Airplane: 7A, ECI parallel valve 360, Vertical Induction, AFP injection, WW200RV prop, dual PMAGS, louevers on bottom of cowl, no antenna fairings. With the lightweight prop, I tend towards aft CG, so not interested in reflexed ailerons/flaps, but would like to consider and learn more about: tire seals, antenna fairings, internal air ramp, and closing my louevers. |
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Bevan |
Reflexing doesn't shorten the chord, it changes your zero lift angle of attack, drag and pitching moment. You will also produce the same amount of lift, regardless of CG, however your pitching moment changes.
It is true that the faster you go, the less angle of attack the wing needs to maintain level flight. For aft CG, you elevator now moves trailing edge down a tad to compensate for pitching moment change, and this adds to the trim drag. I used to have the ground adjustable Whirlwind and it worked great, and with my 160hp I had a top cruise at 8500ft DA, 75%, 2700rpm of 164ktas. Since then I changed to the CS Hartzell and my CG became more manageable, plus I did many other drag reducing changes as well, to get the cruise to be 170ktas. |
Did you make or buy your comm antenna fairings?
I doubt I have the artistic talent to make good ones. Glenn |
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