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Permalink Reply by Joe Spencer on February 1, 2015 at 11:08am

here's a tip i've been working on. haven't finished evaluating it yet. the goal is to reduce the stall speed on my plane from 30-31 average weights to 27-28(mph). got 29.25 yesterday which is the best i've ever recorded. will test it over the long term and average all the results together before any conclusions. i had great results with this tip on a legal eagle...+15.8% ROC and -8% stall speed. I've also got tip plates on my HS and elevator.

it's ticky business when trying to see a reliable 3 mph diff. but the percentage is big!

all very interesting and challenging

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Permalink Reply by Chumphol Sirinavin on February 1, 2015 at 6:20pm

Joe,

Your tip is quite unique! Very interesting indeed. It also increases your wing area.

Champ

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Permalink Reply by Joe Spencer on February 1, 2015 at 7:01pm

Hi Champ

thats right. 7-8" per side. not much but about 5% that oughta be worth something. it seems to hang on longer before letting go...the real numbers will be a while coming. it handles diff in turb...those plates with flange seem to bite and don't wanta yaw. not sure yet if thats gonna be good or not. seems to want more rudder. and do believe the stall speed is some slower as it needs more right rudder and aileron when nearing the stall to counter the torque/p factor thing(3000 rpm power setting for stall tests). that seems to indicate the speed is lower/controls less effective. the pitch is also higher. well, its too early yet for conclusions but enjoying the process. if they dont work out can drill em off and put the originals back on

Joe

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Permalink Reply by Chumphol Sirinavin on February 1, 2015 at 11:51pm

Hi Joe,

I 'feel' that while the flange at the low end of your tip plate helps lessen wing tip vortex, it might give some undesirable effect with yaw control and stall/stall recovery. One thing good from your test is that it takes lower speed and more nose high attitude to approach a stall.

With the exsisting 701 wing tip plate removed, we can gain the wing area a little by adding a tip sweep of about 20 degrees to the rear. This can be done with aluminum sheet as shown by my paper model of the wing tip. The curve line on top represents the existing upper wing tip shape. We can gain more area by adding more skin to the leading edge, within a prudential limit. For fiberglass, I have seen the traling edge curved down into a claw making me wonder of the gain.

Looking forward to more follow-ups of your test.

Champ

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Permalink Reply by Chumphol Sirinavin on February 4, 2015 at 9:42am

Larry,

You are right if I remember ground school material correctly. Don't wait for my flight test result. In 2010, it looked like my CH701 would fly in 2011-12.

Champ

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