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Electric Stunt => Gettin all AMP'ed up! => Topic started by: Jeff Traxler on July 08, 2017, 09:57:22 AM
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Here is another one of my prop experiments.12.75x4.5 CFEP with droop tips.Trying to cut down on vortex drag at the tip to save a few MAH.On the bench it is using about 3% less MAH in static tests than the same prop without the droop tips.The weather has been too crappy to fly it yet but Monday looks like the day
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I'm using 1K 3 oz. CF cloth on the front and back of the blades for stiffness.
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Front view
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one more......
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Looks GREAT
I am flying the prototype Brodak SV-11 ARF Electric with an APC 13x4.5EP. Great combo but that prop is much more flexible than yours. I'm thinking your new 12.75x4.5CFEP is going to be a solid upgrade. Bring one to Muncie for me!
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Dennis,Already have one with your name on it.Do you need an 8MM hole?I am making those and 1/4".Trax
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Dennis,Already have one with your name on it.Do you need an 8MM hole?I am making those and 1/4".Trax
Yes, the "normal" 5mm collet style adapter...
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Shouldn't the tip sweep up instead of drooping? I am thinking winglets here but i might be wrong.
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I borrowed the idea from the prop on one of the full size aircraft I built.The original Witcomb(????) winglet went above and below the airfoil.Don't know weather it's better or worse below but it is a good starting point.
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Shouldn't the tip sweep up instead of drooping? I am thinking winglets here but i might be wrong.
Google Hartzell Q-Tip propellers.
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This is Beringer's prop from 2006:
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One simple test is to run the prop stock then cut of and reshape tip without the tip geometry and compare to see if there is any difference in between the two.
If my goal was to reduce vortex I would go in this direction.
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These tips have more of an objective than just reducing tip vortex.On full size aircraft they help with climb performance.They also help with spillage of thrust from centrifical force and lower prop noise(Not that that matters for E power).The wind and rain took a small break yesterday and I finally got to fly it.Very pleased with the few flights I got in and it performed better than I had hoped.Not used to having my airplane come out of the squares with such authority #^ #^ #^
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Just looking at your prop instinctively i think it will help with traction (climb performance).
An interesting experiment would be to compare 3 props identical in most ways. One prop same diameter as yours minus the curved tip, one prop more diameter, and the existing one.
What i am wondering is if perhaps more diameter would get the job done as the curved tip.
Since we run electric and can monitor battery usage we can ID for the same power consumption per flight what is more beneficial more diameter of less diameter with curved tips.
Also what is the difference between same diameter curved tips versus same diameter no tips.
Please in no way I am trying to talk you out of it or talk bad about it I am more interested towards data gathering and perhaps push this idea even farther.
How did you develop the tip shape?
Traian
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Traian,Did you see the photo in my earlier post of the prop tip from my homebuilt?I used to work for a guy that makes a lot of props for homebuilt experimental aircraft as well as a couple NASA wind tunnel fans and got the idea from that experience.This prop is the first I have tried with these tips and wasn't really sure if I could get them out of the mold or how stiff the tips would be.So far so good on those two.The tips are VERY rigid and didn't look to be changing shape during static tests.I plan on flying a lot in Muncie next week and have a few for others to try and see how they like them.Hope to put one on the new ARF SV-11 Dennis Adamisin has and get his 2 cents worth as well.I'll post more info after I return home.