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Author Topic: Tweaking Flaps  (Read 16307 times)

Offline Alan Resinger

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Tweaking Flaps
« on: December 24, 2011, 02:14:12 PM »
Since the early eighties just about every plane I've built for competition has required some slight tweaking of the flaps to get the trim just right.  This didn't seem to be a problem when we all used 3/32" wire horns.  With the advent of heavy duty controls the process started to become a bit more difficult and I had a few incidents of cracking the flap due to the force needed to make the wire take a set.  Even plywood clips built onto the end of the flap didn't completely cure the problem.  A few years back I was at an early contest in the PNW and was looking at Paul Walker's new ship.  Might have been his first electric. I noticed an oval shaped opening slightly behind the flap hingeline.  I immediately know that it had to do with adjusting the flaps but was unsure of the method he was using.  The opening was adorned with a cryptic decal that stated something like "Don't ask".  All his new ships since have sported the same type opening.  Last Spring I stopped at Paul's house to look over his new ship that was being clearcoated.  I finally ask about the mechanism used for his flap tweaker as I was going to use the same thing on my newest ship. 
The set-up requires dual flap horns with one horn being tied to the flap pushrod from the bellcrank and to the pushrod to the elevator.  The elevator pushrod has a standoff which contains a free turning grade 8 4-40 bolt which then connect to the other horn via a ball link.  I opted to use a T shaped pushrod for my installation.
At the last contest of this year in Salem, Oregon, Paul and I talked about the system some more and he stated that in the process of doing retrimming to a more forward CG this past year he's found the ability to tweak the flaps easily to be a real plus. 
I've included a couple of pictures of my set-up and a picture of the flap horns on Paul's new ship which is under construction for the 2012 season. 

Offline Avaiojet

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Re: Tweaking Flaps
« Reply #1 on: December 24, 2011, 03:23:50 PM »
Alan,

Thanks for the nice photos, you're giving up secrets!  ;D

Charles
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Offline Randy Powell

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Re: Tweaking Flaps
« Reply #2 on: December 25, 2011, 01:39:39 PM »
Pat Johnston and I have both done similar setups from time to time. I preferred a clamp system, but I like the screw adjustment. I assume the nut on the inside is a drag nut to keep the screw from self adjusting?
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Offline Alan Resinger

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Re: Tweaking Flaps
« Reply #3 on: December 25, 2011, 05:16:52 PM »
Randy,
Inside to you, outside to me.  That bolt is free to rotate in it's tube and the nut in front of the standoff is JB welded to the bolt.
Half a turn with a ball driver is the same as rotating the ball link 180 degrees.  The result is quick and accurate tweaking. 
Alan

Offline john e. holliday

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Re: Tweaking Flaps
« Reply #4 on: December 25, 2011, 05:38:05 PM »
I was told one time that if the flaps are lined up with each other, do not tweek them.   Put a trim tab on the plane.   Tweeking the flaps out of alignment with each other causes weird things during flight.  At least that is what I try to do.   I do like the set up tho. H^^
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Offline Randy Powell

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Re: Tweaking Flaps
« Reply #5 on: December 25, 2011, 08:30:20 PM »
I suppose I should have said "forward". Pretty self-evident. Slick setup.
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Online Crist Rigotti

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Re: Tweaking Flaps
« Reply #6 on: December 25, 2011, 08:31:36 PM »
Thanks for posting this info.
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Online Howard Rush

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Re: Tweaking Flaps
« Reply #7 on: January 15, 2012, 06:31:52 PM »
I was told one time that if the flaps are lined up with each other, do not tweek them.   Put a trim tab on the plane.   Tweeking the flaps out of alignment with each other causes weird things during flight.  At least that is what I try to do.   I do like the set up tho. H^^

The only thing worse than tweaking the flaps is adding a trim tab.
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Offline FLOYD CARTER

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Re: Tweaking Flaps
« Reply #8 on: January 18, 2012, 03:36:28 PM »
I agree that "flap tweaking" might cure the symptoms, but not the real problem.  If your flaps measure the same angle, then the real problem is a twisted wing.  The wing twist should be removed instead of trying to compensate.

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Offline Dennis Toth

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Re: Tweaking Flaps
« Reply #9 on: January 19, 2012, 09:14:13 AM »
Sometimes you are just fighting a vertical CG problem (i.e. like the piped ships having the pipe below the fuse creating an inward roll moment that adds to the inward torque of a counter clockwise, tractor, motor rotation), best is to get that VCG in line with the leadout tip exit then use the flaps as minor trim. Cool system, I have used twin flap horns with ball links through a top hatch. The side slot looks cleaner, will give it a try.

Best,           DennisT

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Re: Tweaking Flaps
« Reply #10 on: January 19, 2012, 11:48:55 AM »
I agree that "flap tweaking" might cure the symptoms, but not the real problem.  If your flaps measure the same angle, then the real problem is a twisted wing.  The wing twist should be removed instead of trying to compensate.

   Probably, but given how rigid you need to make the wing, if there is a warp, you aren't going to get it out, or at least not so it stays out.  Alternately, if you can tweak out warps after the airplane is finished, it's not rigid enough.
 
     Given the alternatives of either tweaking the flaps or junking the airplane, I will tweak the flaps.

    Brett

Offline Alan Resinger

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Re: Tweaking Flaps
« Reply #11 on: January 19, 2012, 01:53:08 PM »
I concur.  If people use the time honored trimming chart that Paul came up with about 20 years ago the first thing on the chart is getting the wings level by tweaking the flaps.  As I said, I was suprised last year when Paul was pretty happy to have the feature available when doing major CG shifting.  I dont' think I've ever made drastic CG shifts except when burning off fuel and didn't think much about wing levelling after intitial trimming until this past year when I spent considerable time and practice for the first time in about 20 years.  I've always been impressed with the trim of Paul, Brett, David and Ted's planes.  It is easy see when planes are close to perfect trim.
Alan

Offline PJ Rowland

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Re: Tweaking Flaps
« Reply #12 on: January 20, 2012, 12:32:40 AM »
ok.. I can admit to not understanding things from time to time - generally Im fairly good with most technical things.

Looking at Pauls adjustments, Im confused..

Just what is the adjustment mech? This is for "flap tweaking" how is this achieved through the small side hole, what are we rotating to adjust.

All I see are : Dual horns, each with ( what appears to be ) a Rocket style ball link.

 ???
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Offline rob biddle

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Re: Tweaking Flaps
« Reply #13 on: January 20, 2012, 02:49:16 AM »
 Pj,

 From what I can gather the left side is a 4-40 bolt screwed straight into the ball link. Turning it will move it in relation to the other flap. I'm pinching the idea, hate trying to tweak 1/8"horns.

 Cheers, Rob.
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Offline Dick Pacini

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Re: Tweaking Flaps
« Reply #14 on: January 20, 2012, 06:00:57 AM »
It looks to me that the outboard flap is tied to the bellcrank and elevators, so adjustment is actually made to the inboard flap.  Is that correct?
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Offline Alan Resinger

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Re: Tweaking Flaps
« Reply #15 on: January 20, 2012, 08:17:52 AM »
Dick,
In the pictures I posted, the first just shows where a 4-40 ball driver is inserted into the side to make connection to the 4-40 bolt head on the turning 4-40 socket head bolt that goes to the left side ball link and left side flap horn.  The opposite side has a threaded pushrod insert connected to a ball link on the right side flap horn.  This is a fixed connection.  Only the left side adjusts.  The bottom picture shows Paul's new ship with just the flap horns installed with no pushrods yet installed.  Paul's ship has plug in wings using Tom Morris take apart hardware.  The left side on my plane is the outboard panel as I fly clockwise but it would make no difference which flap you chose to adjust.  Chris Cox and I are in the process of building new ships and after seeing mine he's installing the same set-up into his.  We are going to use a machined fitting to form the T at the flap pushrod end that allows the flap tweaking feature but will also allow for the adjustment of the pushrod length to the elevator by utilizing a left and a right hand threaded pushrod end on the rod.  The high strength machined unit that forms the T end weighs only 4 grams.
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Offline Dick Pacini

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Re: Tweaking Flaps
« Reply #16 on: January 20, 2012, 11:10:32 AM »
OK, that explains it.  You fly ass-end-to, so the left flap is your outboard flap. y1  I see, said the blind man.

It is an impressive device and looks to be just the ticket.  Much cleaner than a tab and much safer than reefing the flaps against each other.
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Re: Tweaking Flaps
« Reply #17 on: January 20, 2012, 12:47:00 PM »
I had a discussion with Paul Walker about the adjustable flaps.  I contended that they were unnecessary.  Sure, it takes a few iterations to level the wing by bending the wire, but after a dozen flights or so, the adjustment stays put for the life of the airplane.  He said that when he goes to a world championships, the travel and reassembly can alter the airplane enough to require a flap tweak.  Practice time is precious, and he can't afford to spend several flights leveling the wing.   I've had similar discussions with Dave Fitz.  These conversations remind me that I'm in a different league. 
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Offline Trostle

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Re: Tweaking Flaps
« Reply #18 on: January 20, 2012, 02:34:48 PM »
Quote from Howared Rush above:  "These conversations remind me that I'm in a different league."
 
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Offline Dennis Adamisin

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Re: Tweaking Flaps
« Reply #19 on: January 21, 2012, 08:08:21 PM »
Ingenius! thanks for posting..
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Offline Bruce Shipp

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Re: Tweaking Flaps
« Reply #20 on: December 16, 2020, 09:28:53 AM »
Necrothread alert! 

Referencing this photo from earlier in the thread, would it be practical to build this set up with an adjustable screw on both flaps?  This would allow you to not only tweak the flaps for roll trim, but allow you to adjust the flap/elevator neutral by turning both flaps the same direction.  It seems this would be a simpler way to adjust the flap/elevator neutral than detaching and rotating a ball link on the end of the push rod at the elevator or flap horn.  It would also allow smaller adjustments than a full 180 degree rotation.

Thoughts?

Offline Ken Culbertson

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Re: Tweaking Flaps
« Reply #21 on: December 16, 2020, 02:43:23 PM »
One thing that has bothered me about this setup is the change in angle of the pushrod which would add more deflection on one flap.  Is it an issue or do you make it so that the outboard flap gets the extra and call it "trim"?

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Offline Chuck_Smith

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Re: Tweaking Flaps
« Reply #22 on: December 17, 2020, 04:20:56 AM »
I never claim to be the smartest guy in the room, but if ever there was an application for 3-D printing in controline, adjustable lucky boxes would be high on the list.
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Offline Ken Culbertson

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Re: Tweaking Flaps
« Reply #23 on: December 17, 2020, 12:02:43 PM »
I never claim to be the smartest guy in the room, but if ever there was an application for 3-D printing in controline, adjustable lucky boxes would be high on the list.
Get your own office and you will always be the smartest guy in the room. LL~

This is a good idea and I would be the first in line to buy one or two.  The engineering feat I am trying to solve is a simple way to add this to a logarithmic horn.  Since I already have a CAM rudder in the chain I am afraid adding both of these will only prove my theory that:  The likelihood of failure = 2 x the square of the number of things attached to your bellcrank.  Maybe tweaking isn't so bad if it gets in the way of the other doo-dads.

Here is what I have come up with.  If it is doomed to failure please say so.   Please forgive me for getting my "Stunt fix" doing trivial brain trips like this.  However, thinking up these things, designing the next kick-ass PA ship and arguing with our poor misguided liberal friends is all I can do for now but it is no substitute for balsa dust!  Good news is that they started laying brick today! 

Ken

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Online Howard Rush

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Re: Tweaking Flaps
« Reply #24 on: December 17, 2020, 12:06:13 PM »
I never claim to be the smartest guy in the room, but if ever there was an application for 3-D printing in controline, adjustable lucky boxes would be high on the list.

Great idea.  How would you do it?  There is also the complication of the control horn having to pull out of the flap when the wing is removed from the fuselage with the flap attached to the wing.
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Online Howard Rush

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Re: Tweaking Flaps
« Reply #25 on: December 17, 2020, 12:21:06 PM »
Here is what I have come up with. 


I’m not one to give advice.  I spent a week trying to get a bind out of such a system before I realized that it was designed in. 

PW built all the claptrap into a tray, then added the tray to the fuselage.  I copied that idea on my last two dogs.
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Offline Ken Culbertson

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Re: Tweaking Flaps
« Reply #26 on: December 17, 2020, 02:08:46 PM »

I’m not one to give advice.  I spent a week trying to get a bind out of such a system before I realized that it was designed in. 

PW built all the claptrap into a tray, then added the tray to the fuselage.  I copied that idea on my last two dogs.
I like the tray idea.  Was already considering it.  More of a Box due to size.  I will have the entire control system from the bellcrank to the CAM rudder working on a test stand before any of it touched the plane.
 Did you find your bind?  I have reservations about the adjustment block.  I think a yoke with adjustments at the horn (horizontal slot and ball link) might be better.  With all the adjustment points it is going to require a hatch but I planned that anyway with just the single log horn.  Plenty of time to ponder, they just started bricking our house today so I still have several months of balsa dust free days.  I have already sketched two more versions.

I think I read that you are using a logarithmic horn.  My question is should there be a very small amount of slop in the bearing race.

Sorry to bother - Ken
« Last Edit: December 17, 2020, 02:27:37 PM by Ken Culbertson »
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Offline Chuck_Smith

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Re: Tweaking Flaps
« Reply #27 on: December 17, 2020, 02:31:26 PM »
Great idea.  How would you do it?  There is also the complication of the control horn having to pull out of the flap when the wing is removed from the fuselage with the flap attached to the wing.

Let's work it out. It's an engineering problem and we have some smart people here.

I'd like to be able to adjust both flaps separately so we can also have an easy way to keep the flaps and elevators lined up too.  Ideally it will work on both sides so right and left aren't required.

Let's kick around ideas and I'll bet we can come up with great solution.
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Online Howard Rush

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Re: Tweaking Flaps
« Reply #28 on: December 17, 2020, 08:03:00 PM »
Did you find your bind? 

Yes.  I then threw that stuff away and used a nonadjustable control horn.

I have reservations about the adjustment block.  I think a yoke with adjustments at the horn (horizontal slot and ball link) might be better. 

That's what I thought.  The way I did it wasn't better.

I think I read that you are using a logarithmic horn.  My question is should there be a very small amount of slop in the bearing race.

Just an RCH.  I specified a 1/4" slot, which was made very accurately for the 1/4" bearing.  That was too tight.  Mike Haverly told me that it's easy to make it just right using a file.  It actually was. 
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Offline Ken Culbertson

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Re: Tweaking Flaps
« Reply #29 on: December 17, 2020, 08:14:08 PM »
Just an RCH.
I haven't been in a position to measure an RCH since 1973.  Do you know the diameter? LL~

Thanks - Ken
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Online Howard Rush

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Re: Tweaking Flaps
« Reply #30 on: December 18, 2020, 05:09:00 PM »
That should do it, Lauri. The groove in the screw could be open on the side to allow wing removal.  A lump in the flap is OK.  IKEA may have the hardware.
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Offline Chuck_Smith

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Re: Tweaking Flaps
« Reply #31 on: December 19, 2020, 05:39:24 AM »
I was looking at an eccentric cam method.

Problem is, I think I just figured out it's a lot easier to make the flaps removable and then make tools for tweaking the wire horns.

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Online Howard Rush

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Re: Tweaking Flaps
« Reply #32 on: December 19, 2020, 06:09:12 PM »
End of horn wire that goes straight into screw slot is maybe not the prettiest mechanically.

There would need to be a force pushing the control horn against the screw, lest there be a deadzone in the flap travel, maybe not the prettiest aerodynamically.


Most elegant would be, if you manage to drill a radial hole in the very end of horn wire  and braze a short piece of say ø2mm wire in it. That wire would then be in screw slot tangentially.

Easy for you to say. You have access to all that surplus Swiss watch tooling.  Good idea, though. Haverly or Helmick will know how to drill the hole.
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Offline wwwarbird

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Re: Tweaking Flaps
« Reply #33 on: December 19, 2020, 06:20:02 PM »
Maybe, if flap is thick enough, you could integrate adjusting screws into flaps, one/each?
You could use a short lenght of threaded rod and in the middle there is a groove where end of flap horn wire fits nicely. Then, there is a threaded hole through flap where the screw fits snugly.
That way you would have precise adjustment about +/-1mm, more rough adjustment could still be made by tweaking the horn wire.
In the picture is a fixed wing wigler that we use in free flight, it kind of gives an idea of what I try to say. L

 Genius, but how do you lock the thread position?
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Offline pmackenzie

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Re: Tweaking Flaps
« Reply #34 on: December 19, 2020, 06:49:47 PM »
Genius, but how do you lock the thread position?

I would assume there is a small screw that closes the slot down so the adjustment screw is clamped.
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Offline Wolfgang Nieuwkamp

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Re: Tweaking Flaps
« Reply #35 on: December 20, 2020, 08:45:04 AM »
Lauri,

Take a flap of 8 mm thickness, tapering to 3mm at the trailing edge. Flap width, say 60 mm. Can you kindly design such an adjusting system?
I would like to build it!
Regards,
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Offline Peter Germann

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Re: Tweaking Flaps
« Reply #36 on: December 20, 2020, 09:03:54 AM »
Like with many things, it's easy to find a complicated solution, but you need a genius to come up with a simple and elegant one. L
Agree... Following a suggestion from Igor, I use 3 mm diameter (1/8) copper-plated welding wire for my flaps and elevators horns . The material withstands operation loads and yet can be easily and sustainably twisted without respringing.
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Re: Tweaking Flaps
« Reply #37 on: December 20, 2020, 12:32:45 PM »
Howard, if you worry about a possible play of the pin in groove, you can use a piece of HSS drill bit as pin. They can be bought in 0,01mm increments.
But I have no idea if all this could work. It would help if you gave some flap dimensions. Then I could draw something up. L

Play in the groove should not be a problem with the sideways 2mm pin.  The screw could even have parallel threads. 

Mike Haverly told me how to drill the hole.  Amazon will deliver the centering drill tomorrow.

Thanks for the offer.  I must draw the flap to get the dimensions.   
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Online Howard Rush

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Re: Tweaking Flaps
« Reply #38 on: December 25, 2020, 02:48:27 AM »
Poked holes in the control horn, two on one side, one on the other:
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Online Howard Rush

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Re: Tweaking Flaps
« Reply #39 on: December 26, 2020, 02:19:22 AM »
Howard, I have a vise exactly like that (but, I'm trying to give it up).

I had to remove that vise from my workbench and bolt it to the drill press to drill the holes.  I couldn't fit the control horn into the official drill press vise. 
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Offline Steve Helmick

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Re: Tweaking Flaps
« Reply #40 on: December 27, 2020, 11:47:53 PM »
I'm shocked to read that the JCT has any vices.   LL~ y1 Steve
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Offline Ken Culbertson

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Re: Tweaking Flaps
« Reply #41 on: December 28, 2020, 02:30:43 PM »
Poked holes in the control horn, two on one side, one on the other:
Are those bushings or bearings?  I am considering flap and elevator bearings. 

Ken
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Online Howard Rush

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Re: Tweaking Flaps
« Reply #42 on: December 28, 2020, 03:09:07 PM »
Looks nice. What's the hole size? Got the flap root cross section dimensions allready? And what's the distance of hole from hinge line?
Ideally, the horn wire should be as close to end of flap (or fuselage wall) as possible.
What do you think about attaching the pins? Is something like StayBrite enough?
Those pins will be really annoying in the transport box🙄. L

Hole size is 1/16 inch (1.59 mm).  I have been distracted elsewhere, so I haven't measured or drawn anything yet. 

Solder should suffice, but I wonder if Loctite makes something that could keep them in place without heating.
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Online Howard Rush

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Re: Tweaking Flaps
« Reply #43 on: December 28, 2020, 03:10:15 PM »
Are those bushings or bearings?

Igus J bushings in aluminum pillow blocks.
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Offline Ken Culbertson

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Re: Tweaking Flaps
« Reply #44 on: December 29, 2020, 11:35:16 AM »
Poked holes in the control horn, two on one side, one on the other:
This will teach you to post pictures - The bearing size that fits that slider appears to be a 10mm.  I just got an order and they really look small.  How big are your bearings?

Ken
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USAF 1968-1974 TAC

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Re: Tweaking Flaps
« Reply #45 on: December 29, 2020, 12:19:04 PM »
The bearing size that fits that slider appears to be a 10mm.  I just got an order and they really look small.  How big are your bearings?

1/4".  Stainless Steel Ball Bearing, Flanged, Shielded with Extended Inner Ring, Number R144-2Z from McMaster-Carr.   I think Igor uses 10 mm.
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Offline Ken Culbertson

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Re: Tweaking Flaps
« Reply #46 on: December 29, 2020, 01:31:42 PM »
1/4".  Stainless Steel Ball Bearing, Flanged, Shielded with Extended Inner Ring, Number R144-2Z from McMaster-Carr.   I think Igor uses 10 mm.
Thanks - Ordered some. 
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Offline Dave_Trible

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Re: Tweaking Flaps
« Reply #47 on: January 01, 2021, 07:58:45 AM »
OR...just make the outside 4-5” of both flaps tweakable....

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Re: Tweaking Flaps
« Reply #48 on: January 01, 2021, 08:17:32 AM »
Lauri these work well for me (and gizmos give me hives).  My airplanes are normally straight but they are handy to trim out engine torque issues and perhaps tweak vertical CG.  Not much to fail and next to no added weight.  Of course I was born just a few miles north of the Ozarks.  You may have to be from the US to understand that!  Happy New Year Lauri!

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Re: Tweaking Flaps
« Reply #49 on: January 01, 2021, 08:45:16 AM »
Well the airplanes I have don't have huge VCG issues anyway as long as I use very light wheels etc.  I'm all IC so can't move batteries.  Wing 3/4" below the thrust line seems about right.  Torque and prop choices show me more to think about it seems.

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