stunthanger.com
Building Tips and technical articles. => Building techniques => Topic started by: Alan Resinger 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.
-
Alan,
Thanks for the nice photos, you're giving up secrets! ;D
Charles
-
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?
-
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
-
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^^
-
I suppose I should have said "forward". Pretty self-evident. Slick setup.
-
Thanks for posting this info.
-
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.
-
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.
F.C.
-
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
-
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
-
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
-
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.
???
-
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.
-
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?
-
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.
Alan Resinger
-
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.
-
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.
-
Quote from Howared Rush above: "These conversations remind me that I'm in a different league."
The Creator has only a limited number of Golden Arms to dispense. Like so many other things, I did not know enough to ask for one.
Keith
-
Ingenius! thanks for posting..
-
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?
-
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"?
Ken
-
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.
-
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
Ken
-
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.
-
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.
-
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
-
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.
-
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.
-
Just an RCH.
I haven't been in a position to measure an RCH since 1973. Do you know the diameter? LL~
Thanks - Ken
-
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.
-
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.
Chuck
-
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.
-
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?
-
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.
-
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,
Wolfgang
-
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.
-
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.
-
Poked holes in the control horn, two on one side, one on the other:
-
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.
-
I'm shocked to read that the JCT has any vices. LL~ y1 Steve
-
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
-
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.
-
Are those bushings or bearings?
Igus J bushings in aluminum pillow blocks.
-
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
-
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.
-
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.
-
OR...just make the outside 4-5” of both flaps tweakable....
Dave
-
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!
Dave
-
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.
Dave
-
I have high C/G problem in my Max Bee. Wing is kind of low, battery is all the way up.
Igor confirmed that he puts his battery this way( I also saw it for myself), so I just kept tweaking the flaps till it flew flat.
Which it does now and has no line tension problems anywhere, but I still wonder if this is the best way.
If I had a repeatable adjuster I would be more likely to try putting the battery in lower, and un-tweaking the flaps.
Next one might :)
Pat MacKenzie
-
I have no idea how much can be tolerated, but as a rule it's never good to fix one fault with another.
I guess the fundamental problem is that aerodynamic claptraps react exponentially to speed changes, when static CG effect changes in a linear way. That way you can acchieve a harmonic balance only in a very narrow speed range. Yes, allmost everything can be trimmed to work well but still all these little things make the model more logical and predictable to trim and fly. Or at least they give you a peace of mind😂. L
Lauri, I would tend to argue that CG change effects are second order, as are aerodynamic effects. Also, since no flying airplane that didn't leave the atmosphere was ever in a truly static condition, that mass and aero effects due to control surface deflections will be forever coupled.
Peace,
Chuck
-
Yes, Chuck. My wording was bad.
But still, it’s never a good idea to compensate one fsult with another. L
Clearly, you've never had to deal with the aero guys on a Formula 1 car!
Seriously, no problem friend. I like your posts.
Peace,
Chuck
-
Here are pins soldered into the control horn arms. I looked for several days for my Stay Brite flux, but couldn't find it, so I used ordinary solder.
-
And those bearing blocks look like the mother of all overkills🙃. Did you make them or buy ready?
Tony Huber made the aluminum blocks. I pressed Igus bushings into them.
I like the idea of one mounting plate where all are fixed before final assembly.
Me, too. That's Paul Walker's idea.
Any idea of the flap root dimensions yet?
Here are some pictures. Sorry about the dimensions. I don't know how to change them to mm in TurboCad.
Control horn slides into a carbon pocket at the end of the flap. Typically I make the pocket just fit the control horn, but here I've allowed for +/- 3 degrees of control horn rotation. The adjuster pin fits in a slot at the bottom of the pocket. The adjustment mechanism would be outboard of the pocket in a chunk of balsa or harder material as required. The pocket is attached to the flap leading edge torque tube and short aluminum doubler tube (blue in the pictures).
-
Here is a cutaway drawing.
I see we can post dxf files, but I can't get the dxf file less than a MB.
-
Here are the dimensions. I can email you the .dxf if you like.
The mechanism can protrude above the flap surface.
Thanks.
-
Yes. 3.175 mm according to Alexa.
-
Here is my entry in the sweepstakes. It's a poor man's version of Paul's design. It is drawn to show the inboard flap adjustable but it would be made to have the outboard adjustable.
You could also flip the adjustable horn and put a slot on the elevator linkage and use the ball link bolt to adjust both flap and elevator. However keeping one setting in line while adjusting the other might result in your accidently dropping your stooge on the inboard wing from 6'. LL~
Tinkering can be fun - Ken
-
Your flaps are very skinny, Howard. Remaining perfectly aesthetic, the adjustment could be +/-2ish° each flap. Is that enough? After that, it gets bumpy.
Bumpy is acceptable. I'm trying for +/- 3° and only putting the device on the right flap.
I now have ideas about how to make the adjuster. I am slowly drawing them. I want both the adjuster and the control horn pocket to be capable of reacting the flap hinge moment. This complicates the design a little.
-
Howard, that looks very nice but much more complicated than Paul’s original system in this thread. What are he advantages of your system over Paul’s original? My first guess is that Paul’s dual flap horn system is not easily incorporated into the Logarithmic control system. Correct? Any other advantages?
Thanks,
Bruce
-
...dual flap horn system is not easily incorporated into the Logarithmic control system....
Actually it could be but it is a lot of work with the dual tracks. I am in the process of machining this one for my Trifecta profile. It will not be flight tested till about March but I see no reason that it will not work.
Ken
-
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
Windy Urtnowski had a simple fix for tweeking 1/8" horns. Removable flaps. He removed the hinge pins and ran a piece of music wire out past the last hinge on the wing tips and bent an 'L' in the end of it, which was then sunk into an L shape trough and covered with a piece of tape? Or it could have been a brass eyelet in the TE.
-
Windy Urtnowski had a simple fix for tweeking 1/8" horns. Removable flaps. He removed the hinge pins and ran a piece of music wire out past the last hinge on the wing tips and bent an 'L' in the end of it, which was then sunk into an L shape trough and covered with a piece of tape? Or it could have been a brass eyelet in the TE.
I do that with my .031" hinge pins, but it doesn't get the control horn tweaked.
-
Howard,
If you drill new holes 1" from hingeline, +/-3° will fit nicely. And, you could still try to find your Staybrite. L
Alas, the control horn assembly is part of the fuselage now.
-
Howard, that looks very nice but much more complicated than Paul’s original system in this thread.
Probably so. It makes more sense, but not enough, if you look at the sequence.
2014 airplane:
1. I think I have a better idea than Paul's-- similar to Ken's, but more complicated. I get parts made.
2. I fiddle with the device for a week, but can't get the bind out.
3. I realize that the bind is designed in. It's too late to do something else, so I revert to a standard control horn.
2020 airplane:
1. I think I have a better idea than Paul's. Inspired by Chuck and Lauri, I decide to build the adjuster into the flap. Looks simple.
2. Find out it's not simple. By then I have a standard control horn built into the airplane with 1/16" thorns sticking out.
3. I'm working on it.
-
Actually it could be but it is a lot of work with the dual tracks. I am in the process of machining this one for my Trifecta profile. It will not be flight tested till about March but I see no reason that it will not work.
Initially, I thought it was too adjustable. If you have a good 3D control geometry program, you could dispense with the slots in the tops of both bellcranks. Then I decided it was really clever. You could find out how much flap travel you need, then set slot 5 to give full bellcrank travel for that much flap. I figured I had a better idea, of course. I would find out how much flap travel I need from the flight data recording, then drill the hole in the new airplane's bellcrank in the right place. The trouble with that is that it's too late to put a control surface deflection measurer in the old airplane. I have provisions for it in the new airplane, but I'd first have to drill the hole in the bellcrank to fly the airplane to get the data.
Also, it would probably be good to be able to adjust the bellcrank-to-flap ratio for flying in different density air,.
-
I do that with my .031" hinge pins, but it doesn't get the control horn tweaked.
Unless I'm missing something, removing the flaps leaves the 1/8" horns exposed. A pair of pliers on each horn allows them to be tweaked...
-
Unless I'm missing something, removing the flaps leaves the 1/8" horns exposed. A pair of pliers on each horn allows them to be tweaked...
My experience has been that tweaking results in over tweaking or breaking a flap. That is why I use tabs which look like crap. Removing flaps at the field is not where I want to go either. So I am for adjustable wherever and whenever you can build it in. My goal is to have everything flap related adjustable from a well placed side hatch. Besides, it is winter which is tinker time!
ken
-
It'll be not necessary to remove wing(s) at field (even though it's not a big deal, just unscrewing 3 bolts. I do it all the time).
I know this kind of mechanics pretty well, and you can tighten the setscrew snugly, you can still turn it but it'll stay in place during flight. When you're done, remove wing(s) and do the final tightening with 1 M2 screw. L
Most of us here do not use removable wings. I have had 2 over the years and I agree, it is no big deal and it does give you access to the flap linkages but I am not going to Worlds any time soon so I will keep them in one piece.
Ken
-
Unless I'm missing something, removing the flaps leaves the 1/8" horns exposed.
And I have a pair of 1/4” aluminum bars with 1/8” holes in the ends with which to tweak them. This is handy for the first flight or two of the airplane, but after that I’d have to untape the flaps to remove them, which is a bother.
-
Lauri,
should the M2 locking screw be rotated 90°, so you can acces that screw after adjusting?
Regards,
Wolfgang
-
If you rotate the whole assembly 90 degrees, then the screw could be accessed through a small hole in the back of the flap.
It would also move the slot for the pin away from the clamp part, which might be better structurally.
The mounting bolts might be problem though in this arrangement....
-
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.
Howard, this is my first adventure into milling since 1974. I learned/remembered a bunch and actually did not have to trash my first part! No end to the uses that cheap mill will have now!
I tried covertly to find the thickness of a RCH but failed. A BCH would be either too thick or too thin. This is for my profile so I am not wasting the 1/4" bearings you suggested. This uses a 4-9-2.5. The "slop" is slightly less than .005. Is that too much?
Will lightening it with the cutouts and holes in the second and third drawings hurt? I used 1/16" steel so it is pretty strong. Shame you can't laser print steel.
Ken
-
Hello Ken,
you can laser print steel, Selective Laser Melting (SLM). But it is expensive!
Regards,
Wolfgang
-
Hello Ken,
you can laser print steel, Selective Laser Melting (SLM). But it is expensive!
Regards,
Wolfgang
Cheaper to have a die made and stamp them. Cheaper yet to DYI with a cheap mill and a good file!
Ken
-
Howard,
This is how I'd do it. Sorry for the drawing. It's designed to fit inside your flap without a bump. It should give the +/-3° adjustability you required. But still, please consider having it in both flaps..
There is a minor f**kup in the plan, for some reason I remembered that the pin ø in horn is 2mm. But actually that's great, it'll be slightly stronger and more compact with 1/16" pins. Also, the distance between pin CL and hinge line should be 1".
I drew it all rectangular, the idea is to file it conical as per flap cross section when it's in place before sheeting the flap. But if I did it (wink wink), I could as well mill it conical.
I would clamp the thing between 2 gf or cf ribs, with epoxy & countersink M2 bolts. Then fill all empty space between ribs with balsa. See the bad assembly drawing.
It looks much more complex than it is. I'd estimate 1 hour work with lathe & mill per unit.
Thanks, Lauri. That looks better than what I was thinking. I'm not averse to having an Allen key slot in the flap to tighten the wee screw. I was considering putting access holes through the fuselage until I remembered that there is a flap in the way on the opposite side.
-
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.
For one-off parts, there are very few things you can't make accurately with a file and other hand tools. It takes much longer and much more skill but most apprentice machinists learned first to make things with files and saws, then, move on to milling machines and lathes.
More or less everything I have ever done was done that way, not that I particularly look forward to it, but I have made some pretty precise parts (like an emergency replacement for Sergei Belko's broken ball link, including *metric* threads with all hand tools I had in my regular toolbox, and under and hour, from a phone description).
Brett
-
Have enjoyed reading all the responses to Alan's initial post.
I think some have missed the point. The method I use is simple, and reasonably light, AND is precise and repeatable. Tweaking a flap horn is less that precise, and very difficult to get a 0.2 degree change in flap angular relationship. My system solves all the issues I have had over the years with tweaking or tabs.
-
And as with other things, thinking I could come up with a better solution has proven troublesome.
-
And as with other things, thinking I could come up with a better solution has proven troublesome.
That's what you get for thinking.
Brett
-
And as with other things, thinking I could come up with a better solution has proven troublesome.
I plan to do it the old fashioned way. Re-invent somebody else wheel. H^^ LL~
Seriously though I don't see any way to pull it off and still have the flaps removable without splitting the flap horn unless you have 3/8" or thicker flaps. Paul's method is probably the best available and I can assume that the small amount of differential that it adds is actually good but it would require a lot of work and accuracy to use it on logarithmic horns. Keith's method on the other hand will work just fine but does not offer the same ease to make very small adjustments. That brings me to what you are working on. I eagerly await a finished product so that I can invent one just like it! LL~
Ken
-
Have enjoyed reading all the responses to Alan's initial post.
I think some have missed the point. The method I use is simple, and reasonably light, AND is precise and repeatable. Tweaking a flap horn is less that precise, and very difficult to get a 0.2 degree change in flap angular relationship. My system solves all the issues I have had over the years with tweaking or tabs.
Hello Paul,
is your method diagrammed somewhere? I have your 2016 column, from Flying Lines, but only one picture comes up of the completed mechanism. You refer, in your article, to other, "Figures" and "Photos" that are not on the page I can view.
Regards
Craig Beswick
-
Hello Paul,
is your method diagrammed somewhere? I have your 2016 column, from Flying Lines, but only one picture comes up of the completed mechanism. You refer, in your article, to other, "Figures" and "Photos" that are not on the page I can view.
Regards
Craig Beswick
Hi Craig,
I put together a document entitled, “Turning to the Dark Side – The Building of Circulas 46 IIe”. This is an electric profile that uses the Walker Flap Adjuster Device (WFAD). The PDF document can be downloaded at: http://flyinglines.org/nunes.circulas46lle.html (http://flyinglines.org/nunes.circulas46lle.html)
“Chapter 4 – Controls System” starting on page 37, shows the control system including how I made my WFAD. Hope this helps.
Dennis
-
Thank you Dennis,
just what I was looking for.
Fantastic build feature!!!
Craig
-
Here is a photo from the first P-47.
Note that this is NOT the final adjustment position for the mechanism. It is in the assemble stage at this point. The inboard horn goes forward, the outboard aft them the bolt threads into the clevis and then drawn into the flaps level position. I have blocks that fit under the horns to check that both horns are in the same plane. Hope this helps.
-
Thanks Paul,
I couldn't work out what was going on inside the black box/captive area. Nothing, as it turns out just a bolt inside a sleeve.
Thanks once again
Craig
-
Step 1 for the adjustable logarithmic. Step 2 is to have my head examined. I was surprised how firm it is with just the single tightening screw. Hope it is worth the extra weight. Wish I had the machining tools some of you have. FYI the bulges where a well trained brazer would have made this look spiffy are from adding a pin into the drive arm so that I could use solder to make it.
1/4" flap adjustment at the TE each way. If it needs that much then the wing is crap.
Ken
-
That's how the first one came out. It should fit inside Howards flap and have the required adjustability range.
Tightening works like a treat.
The distance between hinge line and 1/16" pin should be 1". L
I love it. #^ That is one piece that will not go into the trash if the plane gets totaled! y1
I only wish I had the tools.
Ken
-
That's how the first one came out. It should fit inside Howards flap and have the required adjustability range.
Tightening works like a treat.
The distance between hinge line and 1/16" pin should be 1". L
Very nice, Lauri.
-
Finished product. With good drilling and milling equipment (which I don't have) this is a simple project. Without them it is a day with your favorite files. I have made it adjustable. I can see a need to have the flap drive arm different lengths till I decide on the ratio I want. Then I will probably make it fixed. Probably could use smaller bearings as well.
Ken
-
Ken,
I think the flap horn looks too weak, too little material around the bearing groove. I wouldn't save grams there.
A point well taken. However it is high grade steel. I have put a lot of pressure on it and it doesn't bend. Future ones will be thicker because I will be using a smaller bearing. I used too large a mill to cut the slot and I had to widen it for a larger bearing. Next one will have an undersized slot that I file to fit the bearing and will be 1/8 over the slot.. Right now it is actually thicker that one of Morris's adjustable horns and larger that the drawings Igor published.
Once I get my shop up and running again I will be brazing instead of having to use cheater pins so that I can solder the horn. The main reason I built this one is to mount it on a test stand. It may never see a live flight.
Ken
-
I am really curious as to how much this unit weighs?
-
I am really curious as to how much this unit weighs?
Unfortunately I lost my scale in last year's fire but I have one on order. As soon as I have one I will weigh it. My SWAG is about double a heavy duty standard horn. It can be made lighter, especially if I could have brazed the joints instead of reinforced solder. However, I am not concerned with the weight due to the way I build. For whatever reason I almost always come out nose heavy and have to add tail weight. It is such a regular thing that I even build in a tail weight box just like a tip weight one. The whole gizmo is well aft of the CG. Right now I am making a test stand to evaluate the movement.
Ken
-
Ooh. Ooh. Splendid. Thank you. Can I send you something in return? Some cheese with no holes?
-
...
-
Here's Lauri's tweaker in my flap.
-
...
-
One thing I’m trying to figure out with the WFA, is to also be able to adjust the elevator pushrod. My current plane has the adjustable pushrod and I’m a huge fan of it to get my neutral just right, adjust inside/outside turn, inside/outside corner presentation etc. i realized recently while building an airplane for someone else when I installed the WFA, I can’t adjust the pushrod length because it’s bolted to the other flap horn.
So right now im at a crossroads for my next airplane…either have an adjustable pushrod and don’t include the WFA and use a trim tab again, or the WFA without an adjustable pushrod in the back. Hmmmmm…
-
...
-
One thing I’m trying to figure out with the WFA, is to also be able to adjust the elevator pushrod. My current plane has the adjustable pushrod and I’m a huge fan of it to get my neutral just right, adjust inside/outside turn, inside/outside corner presentation etc. i realized recently while building an airplane for someone else when I installed the WFA, I can’t adjust the pushrod length because it’s bolted to the other flap horn.
So right now im at a crossroads for my next airplane…either have an adjustable pushrod and don’t include the WFA and use a trim tab again, or the WFA without an adjustable pushrod in the back. Hmmmmm…
Matt:
This is the arrangement I have in my plane. It is not a new idea, it is an offshoot of one I saw a while back and modified it to suit my needs. A small access hole for the hex driver. The one on my profile that you have seen is a bit different, but the same idea. Only problem is that you need a guide, I use a piece of paper cut to fit the wing, to keep from losing your reference point. I see your point since any serious flap tweaking will also need an elevator change.