Trimming the Twister #1
Written By Chad Northeast
Guys,
A while back I posted this, and have recently got around to the suggestions.
Bryan said that the TL was far too much negative as the Twister has -2.5 deg molded into the fuse. So away I went, here is a copy of the email (just below) I sent to them after my flights to resolve it.
Before last week you could have never convinced me that you could get a plane neutral in knife edge without giving up something....well I officially stand corrected :-)he knows his stuff,! He was right on the money and the Twister goes pretty much anywhere you point it now without mixing (except a bit on down-line but I think I can get rid of that).
I gotta say thanks to Bryan for his help, he was bang on, and I would suggest to anyone that you give their suggestions and honest try, I bet you are more than happy with the results!
Flying today, was a bit breezy (about 20mph) but steady.
First flight was just to baseline, so you guys could see mods, then results. Nedim was recording so nothing was missed .
Starting point:
· wing is 1.5mm at LE higher than stock, which should be around 0.3-0.4,
· stab 0,
· motor 0
· CG slightly behind front of tube (maybe1/4").
I will have to measure the exact throw for down-line mix, %'s are only good if we all have the same ATV's and total throws.
#1 flight
Base line flight
· left top rudder KE - push to belly
· right top rudder KE - push to belly slightly
· down-line required 1.5% to mix
· up-line good
· 45 down-line
· upright ok, very slight curve
#2 flight
CG moved 1/4" ahead, all else left alone
Results:
· left top rudder KE - slight push to belly
· right top rudder KE – neutral
· down-line required 3% to mix
· up-line good
· 45 down-line
· upright - worse than previous
#3 flight
Added 1/2 turn + to wing - not sure of exact angular change as I did not calculate angle/turn all else left alone
Results:
· left top rudder KE – neutral
· right top rudder KE – neutral
· down-line required 3% to mix
· up-line good
· 45 down-line
· upright - improved over #2 slightly
#4 flight
Added another 1/2 turn + to wing all else left alone
Results:
· left top rudder KE – neutral
· right top rudder KE – neutral
· down-line required 3% to mix
· up-line good - might be starting to go canopy....need a calm day
· 45 down-line
· upright - improved again, its almost straight, would need a calm day to really check
Where I am now is pretty good, I would need a really calm day to check closer. The incidence change is a really minor change at this point. In fact it requires almost no elevator trim after the 1/2 to correct. Up-line snaps are good, they stay online.
I am carrying a little down-trim, from my experience with the Twister. When I adjust the stabs a hair to correct the trim the small deviations in up-lines got perfect with the stab adjustment.
Its damn close now, I need to be at sea level though I don't know how this will work down low All I know is moving from our 3500' to Muncie usually results in mix changes. The diving 45's are probably partially a result of our nice thin zero oxygen atmosphere we have here. lol!
I will fly tomorrow or the next day, hopefully it will be calm and I can verify and tweak further. I could not go more incidence on the wing today because I am binding a bit on one side and need to do some grinding. :)
Now if there was only an easy way of fixing roll coupling in knife!
Coming Soon...
We will soon be adding pictures to the Chronicles to help demonstrate the concepts discussed in each article.
Please Note
This trimming method is an original concept developed by Bryan Hebert, from twenty years of designing F3A airplanes and empirical testing.
This is the sole property of Hebert Competition Designs, please do not copy or reproduce this information without the sole permission of Bryan Hebert.