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Old May 19, 2014, 05:05 PM
Little Red Plane
United States, TN, Knoxville
Joined Dec 2012
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Top Drive Bottom Drive Top hinge Bottom hinge?

Since I've returned to building I've looked at several different way to control flaps and ailerons.

I did what I thought was a top drive system on my last wing using a 'live' Kevlar bottom hinge/top drive and a tape top hinge/top drive for the ailerons. I used the Kevlar and tape styles of hinging to see which I like better. Both work well, but for the little extra work I think that on my next wing I will use the Kevlar live hinges.

Is this to correct way to do this?

To me the only difference between the top drive/bottom hinge and the top drive/top hinge is the increase of the lever arm of the control arm with the top drive/bottom hinge. Am I not getting this concept correctly?

It seems to work well for me, but after some comments from other builders need to ask the crowd what is the accepted way to top drive the wing control surfaces.

What type of drive are you using?
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Old May 19, 2014, 05:37 PM
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Joined Jan 2007
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Gary,

I believe the whole point is to keep as much of the linkage and horn internal as possible to reduce drag. The control surface horn and the servo arm should be on opposite sides ("cross-over") to keep the maximum amount of linkage buried, and the cut-out through the wing as small and as far back as possible. By also keeping the point where the control rod exits the wing as far back as possible, you can possibly keep the entire linkage inside the turbulent boundary layer that gets thicker along the airfoil.

A top hinged surface should have the horn on the bottom, but be driven by the servo arm near the top surface. That keeps most of the horn and linkage inside the wing.

Whether you top or bottom hinge the ailerons depends on whether you want to do Crow (ailerons up), or full-span flaps (ailerons down), for landing. I believe Joe Wurts does both (ailerons down for crawling, ailerons up for max drag), so then it would depend on which direction you need the most throw on your ailerons with flaps/crow.

The Linear Drive Systems being used on some new gliders is the idea taken to it's maximum. where everything is inside the wing profile:

http://www.tud-modelltechnik.de/start_english.htm

Kevin
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Old May 19, 2014, 06:29 PM
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United States, MT
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Garry, like I said in the "other thread" look at any production glider on the market today. Top drive bottom hinge. Look in the DLG forums, look in the F3B/X forums look in this forum.... Look at Soaring USA http://www.soaringusa.com/ Every modern production glider on the market today (worth it's salt) uses top drive/bottom hinge unless it's LDS or RDS. Why? because that's what works best. Enough said...
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Old May 19, 2014, 06:47 PM
Little Red Plane
United States, TN, Knoxville
Joined Dec 2012
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Ihava,
I'm OK with being wrong on any topic.

I just want to learn and fully understand the concepts and systems that other flyers are using.

That is why RCG is a good thing!
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Old May 19, 2014, 06:57 PM
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Garry, It's not my goal to prove you wrong man. I just want your next sailplane build to be "all it can be." We're all able to learn and I'm not saying I know it all cuz I'm the first to admit when I don't in hopes that those with much more knowledge than me ( and there are so many) will teach me or inform me of a better way. In that we are in agreement. These forums are amazingly full of some brilliant minds that offer so generously their talents and knowledge. We are all here to learn from each other and better this cool hobby we all share. I wish you all the best my friend. I'm not trying to be a snob.... I may be a purist but not a snob.

* edit, please look at the bottom of this page at the other "similar threads" listed for additional reading...
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Old May 19, 2014, 07:42 PM
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....because keeping the bottom of the airfoil clean is more important than keeping the top clean. Bottom hinged, top drive generally accomplishes that much better.

At least that's what I remember reading from Dr. Drela somewhere.
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Old May 19, 2014, 08:07 PM
Little Red Plane
United States, TN, Knoxville
Joined Dec 2012
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Well I admit that I did not fully understand the top drive concept.

The good news is that I did get half of my wing correct!
Even after hours of studying the Supra plans I still cut the ailerons wrong, so there for they are top drive bottom hinged. Too late to change it now, but lesson learned.

Thanks to all!

After I posted this I went out to my shop and took another look at my wings, I DID have it correct after all! Both my flaps and the ailerons are bottom hinged and top driven.
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Old May 19, 2014, 10:02 PM
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I use RDS pretty much exclusively but so far all my aileron hinges have been on the top. Flaps , of course, should be hinged on the bottom, since the aren't very effective for landing until the reach 70 degrees or so. I've been considerring bottom hinged ailerons for my next build. Those wipers can get pretty small near the tip.
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Old May 20, 2014, 05:02 PM
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Quote:
Originally Posted by GarryOgilvie View Post
Well I admit that I did not fully understand the top drive concept.

The good news is that I did get half of my wing correct!
Even after hours of studying the Supra plans I still cut the ailerons wrong, so there for they are top drive bottom hinged. Too late to change it now, but lesson learned.
Don't worry about your Ailerons as they will be fine top drive and top hinge. You just have to make your aileron horn a bit longer to get the geometry right between the hinge line and horn hole to get the correct throw.
Mine are like that as well on the two Supras I've built and I have no problems with throw.
I will admit that after studying and building DLG's and their requirements for flaperons that top drive bottom hinge may make more sense for the ailerons as it extends the distance between the hinge line and horn hole allowing you to use a really short aileron horn. The DLG's are looking for a 2-1 ratio or there abouts on their arm and horn. So if their arm is 5mm to the hole, they want 10mm between the hingeline and horn hole.
Next Supra I build, I will do my linkage something like what Vlad does on the Supra. I'll mount a 1/2 cylinder that's been sliced so that it goes to nothing on one side out of hard wood. I'll then drill and tap it for those screw in fittings like the MPI you use. That will give me a range of adjustment in and out which will be especially helpful on setting up the flaps to get max travel.

Terry
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Old May 20, 2014, 06:19 PM
Little Red Plane
United States, TN, Knoxville
Joined Dec 2012
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Terry,
Actually I Did hinge them correctly!

Both the Ailerons and the flaps are top drive/Bottom hinged.

I don't know why I told Keith that they were top drive/top hinge, I'm going to rack it up as a senior moment! Since I'm old I can use that excuse...
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Old May 20, 2014, 08:51 PM
MrE
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Quote:
Originally Posted by Chuchuf View Post
Don't worry about your Ailerons as they will be fine top drive and top hinge. You just have to make your aileron horn a bit longer to get the geometry right between the hinge line and horn hole to get the correct throw.
Mine are like that as well on the two Supras I've built and I have no problems with throw.
I will admit that after studying and building DLG's and their requirements for flaperons that top drive bottom hinge may make more sense for the ailerons as it extends the distance between the hinge line and horn hole allowing you to use a really short aileron horn. The DLG's are looking for a 2-1 ratio or there abouts on their arm and horn. So if their arm is 5mm to the hole, they want 10mm between the hingeline and horn hole.
Next Supra I build, I will do my linkage something like what Vlad does on the Supra. I'll mount a 1/2 cylinder that's been sliced so that it goes to nothing on one side out of hard wood. I'll then drill and tap it for those screw in fittings like the MPI you use. That will give me a range of adjustment in and out which will be especially helpful on setting up the flaps to get max travel.

Terry
Terry - do you have a link or pics to show what you're talking about? Im not quite following you on the description.
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Old May 20, 2014, 09:04 PM
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nnn

* edit, after re-reading my post.... it was confusing to me...
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Old May 21, 2014, 12:50 AM
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Quote:
Originally Posted by dion9146 View Post
....because keeping the bottom of the airfoil clean is more important than keeping the top clean. Bottom hinged, top drive generally accomplishes that much better.

At least that's what I remember reading from Dr. Drela somewhere.
Please, remember and quote here, because is contrary to what I know from other general airfoil aerodynamics sources: the airfoil top is more important than bottom.
Turbulators are placed on top, after all...
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Old May 21, 2014, 06:34 AM
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Quote:
Originally Posted by MrE View Post
Terry - do you have a link or pics to show what you're talking about? Im not quite following you on the description.
Mr E, not sure what you need?
If you look at pictures of Vladimers Supra or a thread about hookup and the mechanism they use on ailerons and flaps you'll see what I mean. Look at the pictures of the ailerons on post #32 here http://www.rcgroups.com/forums/showt...ght=supra+flap
I'm going to do that on my next build as it allows me to screw the horn in and out getting the perfect distance using these brass horns (just the horns) http://www.espritmodel.com/control-h...ace-m3-10.aspx

The other thing I talked about is the height of the servo are hole distance and it's relationship to the height of the flap or aileron control horn hole above the hingeline. Look at post #34 here http://www.rcgroups.com/forums/showt...1512749&page=3

Terry
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