Acceptable aileron hinge gap for a Trainer?
 

What is an acceptable hinge gap for a 40 sized trainer using CA hinges?

Now that my torque rods are installed, it looks like I'm going to have an 1/8" gap between the aileron and the wing. Will this be okay, or should I build up the back of the wing a bit to lessen the gap? I was worried that if I do this, the glue under the 1/16" 'laminate' will not allow the CA to properly wick into the hinge.

Thoughts?

RE: Acceptable aileron hinge gap for a Trainer?
 

Cut into the aileron where it interferes with the torque rods. Knife and small round file makes it easy.

RE: Acceptable aileron hinge gap for a Trainer?
 

less gap is always desirable, and 1/8th inch is a little much, but it is a trainer and i am sure it will fly. if you dont care too much, dont worry about it. if you want to do it right, build it up. however, my bigger concern would be that the hinge point for the torque rod is now 1/8th away from the hinge point for the surfaces.

RE: Acceptable aileron hinge gap for a Trainer?
 

A 1/8" gap is way too much; [:'(] in a slow moving trainer it may not hurt you. [:o]

However; in a faster moving AC it will foul up the flight characteristics and possibly cause flutter which could cost you the AC. [:'(]

The best way to install any control surfaces is to bevel (round) both of the contact points to allow maximum travel without binding. Keep the gaps to an absolute minimum by recessing the hinges.

By keeping these basic rules in mind you will ensure smooth control surface operation and excellent handling responses of the AC.

RE: Acceptable aileron hinge gap for a Trainer?
 

It's not the aileron that's the problem--the torque rod is sitting high. The only way I can reduce the gap is to build up the back of the wing a bit, around the torque rod.

This is my first balsa bird with ailerons, and I've learned an important lesson. Next time I will recess the Torque rod a bit. Didn't have the experience.

But what about the concern with the CA properly coating the hinges if I add a 1/16: strip where the aileron will fit onto the wing? Will the CA wick in properly, even if I drill a hole down the center of the hinge slot?

RE: Acceptable aileron hinge gap for a Trainer?
 

Time Pilot,

If you haven't glued the ailerons on yet, applying a 1/16 strip to the wing hinge like is the perfect solution. Produces the same result as if you had recessed the torque rods that much. The CA will wick in fine. Adding the lamination doesn't change the characteristics of the slot.

Multiflyer

RE: Acceptable aileron hinge gap for a Trainer?
 

in all honesty, i dont think you would ever notice it. it's a trainer. just dont do it again:)
-Clam

RE: Acceptable aileron hinge gap for a Trainer?
 

the big thing too be sure of is that when you have the aieleronon that you are not able to make the aieleron move up or down while keeping the aileron in a consistent attitude (move up and down like an elevator in a building). if it does not move up and down vertically you can seal the gap with some covering or clear tape. This is a hack way of fixing the problem that works but the other methods listed above are better especially if you are flying more performance aircraft in which this method would be very costly to try.

RE: Acceptable aileron hinge gap for a Trainer?
 

The least amount of gap is always best. I'm not following your problem with the aileron torque rod. However, the beauty of CA hinges is it is really not much more trouble then the original install, to cut through them and start over with new hinges, moved an inch or so away from where the original hinges were installed. Your torque rod pivot axis should be on the same centerline as the hinge's pivot point. If this isn't the case, they should have been let in to the framework to allow this to be.

My opinion on the shape of the trailing edges and leading edge of the control surfaces where they meet is as follows. I make the T.E. flat, no bevel or rounding. The flatness should be perpendicular to the centerline of the airfoil, or what is called the cord of the airfoil. I bevel the L.E. of the control surfaces. A bevel is V-shaped, not round. The shape of the bevel should allow for the maximum the control surface will be deflected, at maximum throw. The control surfaces should be as tight as you can make them, without friction occurring between the two.

It is possible to seal the hinge gap on the model as you have it right now and you will not need to do any surgery at all. Take a length of covering material, the same length as the gap between the two surfaces and 3/4ths to 1 inch wide. Crease this piece down the middle, making this piece the length of the control surface gap and folded over, it will be one half of the 3/4th or 1 inch width you made this piece. Lay the crease in the gap and iron this piece to one of the surfaces, then the other. You might be able to do the same thing with Scotch tape. Just make sure the crease is all the way down to the centerline of the hinge axis.

RE: Acceptable aileron hinge gap for a Trainer?
 

Did you cut a channel in the aileron for the torque rod?

RE: Acceptable aileron hinge gap for a Trainer?
 

The picture is what I think you're saying you have now. The wing and the aileron are obvious. And the dark blue right angle to the left represents the torque rod. And there are a couple of nylon hinges and a CA hinge. And obviously there is a large aileron gap (with a dotted line down it's center.

When you attach the torque rod to an aileron (or elevators or rudder) you inset it into the aileron. (I think you've already learned that JUST NOW. ;) right) The amount you inset it would be half the thickness of the torque rod. You want the axis of the rod to line up with the "hinge line axis". With the nylon hinges that look like door hinges, you have to cut slots for them and ALSO inset them slightly into the aileron so that their very centerline winds up where the center of the wing:aileron gap winds up after you connect glue the ailerons into the wing and the aileron. That means with those nylon hinges you have to also slightly inset them into the wing as well. With CA hinges, you don't inset them, you just cut slots for them and try to get the aileron as close to the wing as possible, to have the least gap possible, and glue them.

I said all that and drew the picture to illustrate the problem. The problem is to wind up with the torque rod and whatever hinges you install, both to have the same axis or rotation and that axis winding up being the almost invisible line where the aileron LE touches the wing TE.

In the picture, if you look closely, I drew the torque rod having an axis that's centered down the huge aileron gap. I also drew a nylon hinge that was on that same axis. And I drew one that is placed like you would place it to be on a zero-gap hinge line IF the torque rod had been inset. And there is also a CA hinge represented.

If your torque rod is placed like in the picture, you have a problem or two. You need to inlet it into the back of the wing for one thing. How much?

Ideally, the axis of all the hinges are all on a straight line and the torque rod would be on that line too. If you do as you say you plan (and it's a good idea but one that needs some more planning) and glue in a filler, the filler ideally would only fill the gap from the aileron LE to a line that'd run through the torque rod's axis. See where I'm going? or would you like more????????

Anytime you have a number of different type hinges, you have to place all of them so their axis line up or they will bind the free movement of the surface. The stronger the hinge, the worse the binding. CA hinges don't care where they bend so will be forced by a strong "hinge" like a torque rod to try to bend inside the wing. Not good.

RE: Acceptable aileron hinge gap for a Trainer?
 

I thought I'd post a picture so you could better see the problem. A bit out of focus, but you can see by the ruler (divisions are in 1/8ths) that the rod sits about 1/8" off the wing. 1/16" balsa sheeting slides nicely under the torque rod.

Any new thoughts?

I did cut out a groove in the aileron so that the center of the torque rod is in line with the 'leading edge' of the aileron.

RE: Acceptable aileron hinge gap for a Trainer?
 

Rlipsett,

I clamped a CA hinge between some balsa leaving a 1/8" gap and it looks as if it will go up and down as you say.

Minnflyer,
The channel is in, but the aileron isn't glued in yet. One less problem to deal with. :)

Darock,
Thanks for the diagram and explanation. That was the conclusion I came too. I didn't think much about it when I glued the torque rods in thinking that the kit designers wouldn't have allowed that much error in the design. I know better now.

Luckily, a 1/16th sheet will slip under the torque rod. I have some 3/32" sheeting so if I use that and groove out the area where the torque rod will fit, I should pretty well be bang on to a perfect hinging job, yes?

One question though: When I put the covering on, do I go over the torque rod or under?

RE: Acceptable aileron hinge gap for a Trainer?
 

Time pilot,
There is an easier fix for this. Right now you have the groove in the aileron cut so that the torque rod is flush with the top of the forward edge of the aileron. Cut the groove a little bit deeper in the aileron so that the edge of the aileron is against the trailing edge of the wing, and so the torque rod now sits a little deeper than the edge of the aileron.

Ken

RE: Acceptable aileron hinge gap for a Trainer?
 

TimePilot,For the perfect hinging job, you want to glue two strips of wood. Take an imaginary line that extends the CL of the torque rod toward the wingtips and that should be your new hinge line. Fill from that line to the TE of the wing, that will become the new TE of the wing, and glue that solid to become a perminent, non-moving part of the wind. It's actually a very easy step. Just use a balsa wood strip that is slightly wider than the wing and sand to fit after the glue cures. Now glue a piece of wood to the LE of the aileron that brings the LE of that aileron to the imaginary line. This is also an easy job.

If you use slightly thicker wood and sand to fit after the glue dries, the glue seams will be zip. Won't be a clue anything was different about this part of the build.

You don't want to try to cover anything that is going to move under the cover. Since the torque rod is going to turn with the aileron, cover it from the aileron side. When you cover the aileron you'll cover it with the aileron.

RCKen,
That fix will close the hinge gap, but unfortunately, there will be a really bad result. If your filler moves some of the aileron hinge line forward of the aileron hinge line that already exists where the torque rod is you'll bind the aileron movement.

The torque rod has established an axis right down the center of it. It's the imaginary line that will become the hinge line when everything is assembled, ready to go. And that torque rod is going to try and force the aileron to hinge around that axis. When you glue wood to the aileron beyond where that axis runs, and then hinge where your new gap is between the wing and aileron, all the hinges are going to try to hinge where the new gap is while the torque rod is trying to get them to hinge back in the fill wood. The new LE of the aileron is going to want to go Up and Down a lot near where the torque rod is. And if there are CA hinges there, they're going to try to keep the LE of the aileron from moving Up and Down, and there will be binding.

It really isn't harder to glue in two strips of wood that follow the already established hinge line. It just takes a little more time. And if you don't take that time to give the aileron one hinge axis instead of two you'll have problems. We really want to have all the hinges on the same axis of rotation.

RE: Acceptable aileron hinge gap for a Trainer?
 

Really, either fix will work, but Darock's is a more proper way to do it as it will put the torque rod on the hinge line.

Time Pilot, Use the 3/32" sheet you have and do it like you said (Cut a groove, slide it under the torque rod, and glue it to the Trailing edge)

Covering should go UNDER the torque rod, not over it.

RE: Acceptable aileron hinge gap for a Trainer?
 

BTW, Ken,
Actually, filling with just one strip of wood would be what you wanted to do if you were using nylon hinges and planned to move their hinging out to line up with the hinging axis already established by the torque rod. If you round the resulting LE of the aileron, and use hinge locations that are online with the torque axis, you wind up with a very elegant result.

I've added a couple of hinges that would work and one that won't:

RE: Acceptable aileron hinge gap for a Trainer?
 

MinnFlyer,
Actually, there is more to it than "a more proper" way. That sounds like the quick and dirty ways won't bind the servo. chuckle.....

Anytime you don't have all the hinges on the same axis, you're screwing up the freedom of movement for the surface.

Back when most people flew Control Line because RC wasn't even around, most of the beginner kits had bent steel torque rods and the surfaces were hinged with alternating strips of cloth and a TON of beginners would wind up with exactly what's being suggested as a quick and dirty "fix". Until the steel torque rods caused the other hinges to fail, those beginners had lousy flying models. The controls would not want to stay at neutral. The flaps would want to either be full up or full down. The torque rod would be trying to rotate the front of the flaps right where the hinges there were trying to keep that part from moving. And the surface would wind up wanting to stick up or down but really, really did not want to be at neutral. And you can bet the farm that surface had no freedom of movement. Alternating hinging was about the most resistance free hinging you can imagine, but when you fought it with a steel torque rod that was off the centerline by 1/8" there wasn't any freedom anywhere.

Today, we don't feel any of the forces the servos are going to have to fight. And the model won't be kept from flying. But there is a reason that most every building manual worth reading says to make sure you keep all the hinges on the same line.

But whatever.... all the suggestions will "work". For how long, and how well is up to the builder.

RE: Acceptable aileron hinge gap for a Trainer?
 

again, guys,
you are all forgetting several things.
1. these are CA hinges, and will bend wherever they are exposed. so if you put 1/8th inch gap in you aileron, they will bend wherever it's the easiest (ie centerline) and there will be no binding

2. while the surfaces may not center perfectly, it is a trainer, which fights being turned, and will resist small mis-alignments. being trainers, they are also built to allow the modeller (presumably a first timer) to make mistakes during the build, and not have them show up in the flight characteristics or interfere with the training ability of the aircraft. trainers are extremely tolorant of elevator mis-alignments, (very common) improper thrust line (again common) and even a crooked wing, caused by a novice getting used to the sensitivity or rc planes and pulling too many g's in the process.

3. the ailerons are too small to really worry about flutter, especially if you seal the gap.

basically, if you want to do it right, shim up the TE of the wing and put the hinge line center with the torque rod. however, it is a trainer and you could get by without it. i would personaly do it the right way, but either will work just fine.

RE: Acceptable aileron hinge gap for a Trainer?
 

Sorry for jumping in on this....but I was wondering the same for the control surfaces on my plane also. I take this is way to much gap? Its on a Kadet Senior which is my first plane/build.

flynte

http://www.telusplanet.net/public/flynte/113_1368.JPG

RE: Acceptable aileron hinge gap for a Trainer?
 

Wow. This is more help that I'd ever have expected. Would it be too much if I just shipped one of you all the parts and you returned it covered and ready to fly? ;)

I didn't want to sink the torque rod deeper into the aileron to close the gap because then the front of the aileron would sweep the hinge line and that doesn't seem good building practice.

But what I will do, is do it right, and build up the TE of the wing to close up the gap. This way I will be less inclined to do the same thing next time. :eek: Luckily, I don't need to build up the front of the aileron as the piece was slightly oversized anyway.

Many, many thanks!

Now off to cut wood!

RE: Acceptable aileron hinge gap for a Trainer?
 

I don't see any real difference between filling the gap with strips of wood and sinking the torque rod deeper into the aileron. In either case, you don't want the aileron rubbing against the back of the wing. Try as you might to make a hinging job perfect, there are always little flaws that keep this from happening! The aileron may have a small warp, one way or the other, the hinges may not be perfectly aligned, the hinges may not be dead center on the hinge line or may be slightly slanted from the centerline, etc. etc, this list goes on and on. Darock describes what might be the absolute best correction. However, since your gap is 1/8th inch, using 1/16th thick strip is the perfect way to fill this gap, putting 1/16th on the wing and 1/16th on the aileron. No sanding required and a perfect line for the hinge line, if the surface being glued to are perfect.

RE: Acceptable aileron hinge gap for a Trainer?
 

Actually, they will bend wherever the forces cause them to bend. Yes, and it'll LOOK like everything is kewl. But "the easiest" in that case isn't easy for the system and there will be binding. The reason to have all the hinges bend along the the axis of the hingeline is based in solid physics and from years of experience of all the modelers who came before us. One of the reasons CA hinges fail for some people and last years and years for others is how easily they operate. Put 'em in so they have all want to bend on the same line without built-in extra stress and they'll last. And the servo's won't be pulling excess battery.

whatever.......

RE: Acceptable aileron hinge gap for a Trainer?
 

removed as unnecessary

RE: Acceptable aileron hinge gap for a Trainer?
 

TimePilot,
With the aileron not yet placed, truth is, all you have to do is put in one filler, and that one on the back of the wing. Fill out to the centerline of the torque rod. Then taper the front of your ailerons to come to a point along the centerline of the torque rod and you're ready to hinge. And the hinges and torque rod will all share the same center of rotation.

I've drawn a picture to illustrate the problem with having two centers of rotation. And one to show the setup you'll have by filling half the gap and alingning the aileron to fit that.

The top picture shows what you have now. The little yellow dot is the center of rotation of the torque rod. The gap is where it would be if you had the aileron all the way forward.

The middle picture shows that same little yellow dot. That's where the torque rod is going to rotate. At the point of the green lines is where the aileron LE would go if it lined up to the front of the torque rod. The point on that "arrow" is going to be forced Up and Down by the steel torque rod. If that's where the CA hinges go through, that point on the CA hinges is going to try and rip them apart there. Since the CA hinges are flexible, they're going to shift that tearing force back toward the line where the yellow dot is. If there is balsa wood in the way, it'll just have to crush and bend.

The lower picture shows the result if you just move the wing TE back to line up with the torque rod's center of rotation. That'd take one fill strip of balsa that'd be glued solidly to the original wing TE. You'd then attach the ailerons and be good to go. You could simply profile their LE and you'd wind up with them being 1/16" wider than the plans call for. If that bothered you or looked funny anywhere, you could simply trim them 1/16".

Hope this helps everyone understand.