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Author Topic: Dumb trim question, I should know the answer!  (Read 1005 times)

Offline Larry Renger

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Dumb trim question, I should know the answer!
« on: July 24, 2007, 10:06:49 AM »
I always manage to argue myself into mystification when trying to figure out which way to tweak flap vs elevator setting to even out insides and outsides.  I know it has been discussed a zillion times, but not recently enough for me to find, I guess.

My Smoothie turns insides better than outsides.  I THINK this means I need to lower the trailing edge of the elevator from neutral when the flaps are exactly level.  Or is it the other way around?   HB~>  b1
Think S.M.A.L.L. y'all and, it's all good, CL, FF and RC!

DesignMan
 BTW, Dracula Sucks!  A closed mouth gathers no feet!

Offline Jim Oliver

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Re: Dumb trim question, I should know the answer!
« Reply #1 on: July 24, 2007, 10:34:13 AM »
Larry,
Some genius will undoubtedly give the right answer---until then, you might think about adjusting your handle to give slightly more down control movment.

Cheers,
Jim
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Offline Crist Rigotti

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Re: Dumb trim question, I should know the answer!
« Reply #2 on: July 24, 2007, 10:48:56 AM »
Shroten the elevator pushrod.  More down elevator at neutral flaps.
Crist
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Electric - The Future of Old Time Stunt

Offline Larry Renger

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Re: Dumb trim question, I should know the answer!
« Reply #3 on: July 24, 2007, 10:53:44 AM »
That's what I thought ...... but wasn't quite sure!  Thanks   y1
Think S.M.A.L.L. y'all and, it's all good, CL, FF and RC!

DesignMan
 BTW, Dracula Sucks!  A closed mouth gathers no feet!

Offline rustler

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Re: Dumb trim question, I should know the answer!
« Reply #4 on: July 24, 2007, 01:36:35 PM »
The trick has got to be to keep the insides as good, while improving the outsides. Anyone got any further thoughts?
Ian Russell.
[I can remember the schedule o.k., the problem is remembering what was the last manoeuvre I just flew!].

Offline Larry Renger

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Re: Dumb trim question, I should know the answer!
« Reply #5 on: July 24, 2007, 03:58:53 PM »
Actually, the insides are a little TOO sharp, to where they slow the plane down and happen too high.  More even maneuvering is what I need.  Shorten the flap to elevator rod here I come! (and then find the neutral at the handle again, of course).  Thanks all!
Think S.M.A.L.L. y'all and, it's all good, CL, FF and RC!

DesignMan
 BTW, Dracula Sucks!  A closed mouth gathers no feet!

Offline Kim Mortimore

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Re: Dumb trim question, I should know the answer!
« Reply #6 on: July 24, 2007, 06:38:14 PM »

There seems to be a lot of this going around (uneven turn rates in one direction or the other), at least in the area where I fly.  I guess our planes are very sensitive to small errors in thrustline and stab incidence.  I don't see any other explanation (at least for conventional designs).  Some very experienced builders as well as less experienced ones run into the same problem. 

Kim Mortimore
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Santa Clara, CA

Online Dennis Adamisin

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Re: Dumb trim question, I should know the answer!
« Reply #7 on: July 24, 2007, 10:19:36 PM »
Larry:
By all means, try the down elevator

but

make sure your wings are level too.  If you are riding outboard tip high it will turn easier inside than out...
Denny Adamisin
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Offline Bill Little

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Re: Dumb trim question, I should know the answer!
« Reply #8 on: July 25, 2007, 12:31:57 AM »
There seems to be a lot of this going around (uneven turn rates in one direction or the other), at least in the area where I fly.  I guess our planes are very sensitive to small errors in thrustline and stab incidence.  I don't see any other explanation (at least for conventional designs).  Some very experienced builders as well as less experienced ones run into the same problem. 

Kim Mortimore

Hi Kim,

It seems to be the rare case that the turn rates are equal "off the board".  Most of the top echlon fliers Ihave talked to over the years usually have the problem of tighter insides than outsides.  Mr. Terry Fancher at the WC in '04 had about 5/16th" droop in the elevators at flap neutral.  I have heard it explained that the wing dampens the elevators somewhat in the conventioal stab C/L higer than wing C/L when "down" elev. is applied.

I found the opposite in almost all my planes.  I have a funny wrist anatomy (I guess), it is very easy for me to give a lot "down" control movement to the handle.  Another problem I ran into was that I am convinced that a "vertical" hand is best for CLPA.  I went too far in the other direction and actually had my hand tilted back!  The natural position for the hand (as you know) is for it to tilt "forward" slightly when the arm is extended.  But I do not fly with an extended arm, I have some bend in the elbow.
Big Bear <><

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Offline Larry Renger

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Re: Dumb trim question, I should know the answer!
« Reply #9 on: July 25, 2007, 03:25:09 PM »
Larry:
By all means, try the down elevator

but

make sure your wings are level too.  If you are riding outboard tip high it will turn easier inside than out...

Verrrrry interestink!  My flaps were tweaked in the outboard tip high direction.  I have fixed that, so I'll leave the elevator alone until I have had a chance to fly agin.

Thanks one and all for the input. 
Think S.M.A.L.L. y'all and, it's all good, CL, FF and RC!

DesignMan
 BTW, Dracula Sucks!  A closed mouth gathers no feet!

Offline Stan Tyler

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Re: Dumb trim question, I should know the answer!
« Reply #10 on: July 31, 2007, 11:01:14 AM »
Larry,

You may also want to check to see if the motor thrust line has any unintentional up or down thrust.

Regards,
Stan

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