drbutton

I had a thought- I didn't see this on the first few pages of my search of "hinges," but if it's a repeat, oh well.

Based on this method: http://www.rcuniverse.com/magazine/a...TOKEN=11509295

Installation of CA hinges: I like the idea of drilling a hole in the center of the hinge slot, as has been discussed. However, I also thought that drilling a small hole through the center of the area that the hinge will occupy in the TE and LE (perpendicular to the aforementioned hole, but passing through the tunnel that would be created) prior to hinge installation would help. The result would be a "T", turned sideways. To fasten the hinge, insert it into the TE and LE (using the "pin in the center method"), overflex the control surface, and then apply the thin CA through the holes perpendicular to the hinge. This way, the thin CA could wick into the hinge and wood, and maybe preclude direct gluing at the hinge line. Any thoughts? I havent tried this yet, so lemme know what you think. Thanks!

zetor

My Feedback: (2)

I put ca hinges into an ultra stick wing last night. The provided hinges had a large oval hole in the center. The instructions called for punching a pin on one of the sides of the hinges in the center (font and rear) creating another hole. That seemed like it would just weaken it further. I didn't do it. I just dug the slots out enough that when the hinge bottomed out it was in the center. I didn't wollow the hole out either. I know I must have gotten a little on the hinge line because the gap was very small. Movement of the flaps and ailerons are free. They flop back and forth when the wing is turned over. The ones on my avistar are a little stiff. They were a different style hinge - much "fuzzier". Who makes the best ca hinges?

J_R

I agree with the article on RCU with one addition. Before you start, get a crayon or grease pencil and mark the hinge line on both sides of the hinge. The CA will not stick to it and CA on the hinge line can not become a problem.

JR

Kaos Rulz

I like the hinges from Radio South. Been using them ever since Radio South started selling them. No problems to date.

I never trust the supplied hinges that come with any kits. Toss them and use most anything else. I think the worst after-market CA hinges are better than those suppied in kits. The type that's best is a personal preference. I'm sure others will chime in.

The most important thing to remember is to correctly install them. The best hinges in the world will fail if improperly installed.

drbutton

So, what do ya'll think about my hole idea?

J_R

If I understand correctly, your going to drill the hole from top to bottom.

I quit pinning CA hinges some time ago, but, if I was going to pin them your idea might be something I would try before inserting the pins, IF the surface was uncovered. Most of the time I have already covered the control surfaces and I am not inclined to drill a hole in the covering after that. I think there is a real likelyhood that the CA would go on thorugh the hole and get all over the surface.

If you use the RCU method, there is probably no advantage to drilling the extra hole.

drbutton

Yeah, I forgot to mention that I planned on doing this without covering (at least not around the hinge areas). But, the reason for the top to bottom hole is not to make room for a toothpick. Rather, the hole is drilled BEFORE placement of the hinges. I plan to follow the RCU method up to the point where the hinges are glued. Where that method suggests application of glue at the hinge line, I plan to put it in through the holes. This way, the potential problem of CA related hinge brittleness and failure is avoided. If the right amount of CA is used, none would wick all the way to the hinge line. Again, just an idea I had, so feel free to comment.

Kaos Rulz

I think that you have a very good idea here. Have you tried a test piece on scrap balsa? Let us know how you like it. [8D]

J_R

Run the test Ed suggested, and at the same time, try the Crayon. It works.

MinnFlyer

My Feedback: (4)

Drbutton, your idea will work beautifully. The only drawbacks are that if it is done after covering, the holes will have to be patched, and if it's done before covering, then you have to cover with the control surfaces already hinged, which is a real pain.

J_R

If you cover it after installing the hinges, the easiest way is to have covered the the edges of the surfaces with about 1/4 inch of covering on the flat of the surface. That gives you something to seal to, and at the same time covers the actual hinge joint without having to seal in the gap. It should still leave enough area to sand without messing up the covering.

stuk_at_work

My Feedback: (111)

I think I may try a variant of your suggestion on an Midwest AeroStar I am in the process of rebuilding this week.
[ul][*] I'll drill the perpendicular hole all the way through as you suggested, prior to covering on both the fixed and movable surface, and enlarge one side of the hole to accommodate a toothpick "pin".[*] cover all surfaces (Monokote) prior to hinging.[*] Re-open one side of the hole on both sides of the hinge. For ailerons and elevator, I'll use the lower sides. For rudder, I'll just chose one side.[*] Draw a crayon line across the hinge at what will be the hinge line and insert all hinges for the control surface.[*] Slightly flex the control surfaces and CA through the holes. BTW, this probably has the added benefit that since the surfaces can be kept pretty much horizontal to the floor (==gravity!) as opposed to perpendicular as in typical CA hinging, there is less likelihood that the CA will accidently "drip" onto other parts of the model.[*] After all hinges are in, drill through the hinge from the exposed hole, being careful not to drill all the way through! CA toothpicks or suitable sized dowels. As an alternative, just fill the hole with medium CA after drilling the hole through.
[/ul]

I realize that this is extreme overkill for this particular plane, but if the cosmetics are not too bad, it might be a worthwhile technique for other planes down the road (or is that down the drunway ). I'll let you know after the weekend how it turns out.

greenboot

My Feedback: (1)

The idea seems worth a try. However, for this to be a "solution", I need to have a "problem" first. I've never had trouble installing CA hinges, nor have I had one break. I would make sure you have given the normal installation a fair chance of suceeding before trying new methods.

The only problem I can see is spilling Ca on the wing surface. That stuff is very hard and I would not want to get it on the top of the wing surface.

Tom

drbutton

I'll be honest with you, Greenboot, I've never used CA hinges in the first place. However, I've noticed that thin CA glue will wick into almost anything, and I am concerned that, no matter how careful I am, some of the CA will wick into the flexing area of the hinge if the glue is added at the hinge line. J_R, you obviously believe in the crayon method: how does the crayon stop the CA from wicking through the hinge UNDER the crayon line? I am assuming that the diffusion of CA through the hinge is minimal. An additional thought: perhaps using the thicker "medium" CA through the holes would work better by minimizing diffusion and better filling the hinge/wood gaps.

J_R

Since this is your first attempt, trying these ideas on scrap is appropriate. The CA hits the crayon and immediately wicks into the wood. You only need 3 or 4 drops per hinge per side. Flex the pieces and see what you think. When you get done with each, let it fully cure, then destroy the sample by pulling till it breaks. if you make a couple of samples of each, your going to have a good idea of what works. It takes longer to write about it that to do the testing.

The problem with CA on the joint is not so much wicking into the hinge as build up of CA on the hinge and effectively gluing the surfaces together.

ABSOLUTELY DO NOT use thicker CA. It won't wick and you will find out what happens when the hinge lets go in flight.. guaranteed.

greenboot

My Feedback: (1)

Knowing you've never tried the normal installation, I again would recommend it first. 3-4 drops is about right. If you are getting a build up on the hinge, you are using too much. Sometimes, as you say, the Ca does bond the aileron to the wing. But if everything is monocote covered, it isn't a problem. It will break free after it dries.

Never use thick Ca, it absolutely will not wick in deep enough.

Tom

drbutton

Thanks for the replies, guys. I'll try the scrap idea, both my way and the RCU way, and post my results.

MinnFlyer

My Feedback: (4)

When I wrote the CA Hinge Article, I mentioned the crayon method. And this was exactly what came to my mind. The way I see it, the CA WILL seep under the crayon. By the same token, CA in the hinge area (w/o crayon) will seep INTO the wood.

The end result is that using either method, some CA will remain on the hinge in the flex area. The good news is: It just doesn't matter!

We are talking about such a minute amount that it really won't make a difference. As soon as the CA has cured, and the hinge is flexed, the CA will crack and won't hinder the hinge's ability to move, nor will it damage the hinge.

This is one reason I said NOT to use accelerator. For a short time, the CA may pool in the gap (Crayon or not), and if accelerator is used, you will get a BIG Chunk of hardened CA in there which COULD cause damage to the hinge.

Bottom line... The method used in my article works, and it works very well. If you choose to add crayon, I won't say don't. If you want to pin them as well, I think it's overkill on most planes, but if it blows your skirt up, have at it.

J_R

Nice recap Mike

Oh.. and watch that skirt

drbutton

OK, guys, here are my results:
I ran two tests, each time making the perpendicular holes in the LE and TE with a T-pin (I did NOT make a hole in the center of the gap, parallel to the LE and TE, as per the RCU method). I used a 1/16" drill bit to enlarge the holes, and get out any balsa dust. I then inserted the CA hinges and created a minor gap between the LE and TE (I didn't flex the joint to an extreme angle, because it kept messing up the alignment of the gap). Finally, I used Zap thin CA with the micro applicator tip attached for gluing. The first time, I dripped it into the holes, but after the second drop, it began to pool in the hole, leading me to believe that it wasn't wicking very well. When I destroyed the test piece, my suspicions were confirmed: not as much of the hinge had bonded to the wood as I would have liked. My second test, though, was a big improvement. This time, I pushed the micro applicator into the hole until it touched the hinge, and then added glue until it began to pool. When I destroyed that test piece, I had a MUCH better bond: nearly the entire hinge had adhered to the balsa. So, I think I have a winner here. However, I'm still open to comments.

Covetski

Here's the deal: The pins don't hold too well, try using toothpicks and ca'ing them in, so just put ca on the hinge, stick it in, and then make holes big enough just for the tip of the toothpick, put ca in the hole, ca on the tip of the toothpick and stick in in the hole, cut, and sand. Makes the place look like you just stuck the hinge in there after you cover it, but is as strong, stronger, or very little weaker then with pins.

Covetski

ps, do either 2 diagonal holes, or four: one in each corner.

Covetski

I meant diagonally across from each other
____
|* |
|_*|

Wabbit

Hey guys, I've built and crashed my share of airplanes and I still have no idea of what you all are talking about with the "toothpick" idea? Are you poking the toothpick through the monokote and the hinge, or drilling a hole in the hinge or what? I've just never heard of that before! Thanks

J_R

When you use nylon hinges and epoxy, you can never be certain that the hinges are glued in properly. As a fail safe, a hole was drilled through the surface and the hinge and a tootpick inserted and glued in.

If CA hihges are used and installed in the manner that MinnFlyer suggests, it is pretty well accepted that the toothpicks are not necessary.

JR