747drvr

My Feedback: (5)

Hi Guy's

I'm getting to the point where I have to start hinging my lightply overcast ( Super Reaper ).
What types of hinges are most commonly used by the jet guys ?If the flat pinned hinges are used, I understand that it's advisable to drill and pin them in place. This would have to be done before painting so I'm wondering how you guys keep the hinges from fouling ?
I'm thinking in favour of the Robart hinge points which can just be glued in post painting. Opinions ?

Terry Holston

My Feedback: (1)

Hinge points have worked well for me, I use 5 min epoxy and do all the hinges in one surface at a time.

Put a drop of 3 in one oil on the hinge pin before installing. Bend them at the hinge line 45 degrees or so and sight along the length of the surface at the hinge points.

Align them so they are all parallel and in the same plane. As the epoxy jells use a new exacto #11 and pull off the excess epoxy that has squeezed out. (it'll come off in a chunk and not string out at the right jell point)

Operate them a few times as the epoxy finishes curing, then install in the flying surface.

It is a lot of extra work, but I like the Robart Hinge Pockets, too.
makes painting and repairs a snap!

Woketman

My Feedback: (6)

I agree with Terry, the jumbo Robart hinge points are the way to go. I drill the hole just barely big enough to get the hinge in. If you put it in, you can hardly get it out due to the barbs. If you were a bit goofy, you might not need to even glue them, that's how good the friction holds them. Then I take a hypodermic that I have drilled out and inject a bunch of the slowest drying epoxy I have. Oil the hinge joint and put 'em in. Then stand the surface or the aircraft up so that the hinge line is below the glue. This allows a pool of epoxy to form where the hinge is sticking through on the inside of the structure. When this cures, it forms a sort of washer that can not allow the hinge to break out. You'll need to destroy the structure to ever get that apart.

Terry Holston

My Feedback: (1)

Woketmans system works really well also, but I never have time to wait on that slow epoxy. Thats why I use the five min stuff.

I have never had a hinge come loose, unless there was a crash, and even then it took out part of the wing structure with it.

Others have said "Aeropoxy" works well , too

Woketman

My Feedback: (6)

Yeah, I see Terry's point, but I just put the hinges in as the last thing I do on a building session so they are cured in the AM. I just had a thought that I have not tried but should be even better. Get some of the Aero-Poxy like stuff, ya know, with the mixing nozzles, and squirt that in the hole. The nozzle tip will fit just fine and you don't have to mess with the hypo-needle. But be sure to use a non-thixotropic epoxy as you want it to sag so that it surrounds the hinge point. This is what I will do next time.

747drvr

My Feedback: (5)

Hi Guy's

Thanks for the great info ! If I did choose to use the flat style hinges, are there any particularly good ones and how do you do the pinning routine and keep them free of paint when finshing ?

Woketman

My Feedback: (6)

Marc, I can't answer the flat pinned hinge questions, but I don't think you have to be worried a bit about the paint. As long as its paint or epoxy that gets hard, you just flex the surface and break off the little bits that are in the way and it always works fine for me. By the way, I tried the mixing nozzle approach with the Robart jumbo hinge points this weekend and it worked great!

DavidR

My Feedback: (1)

I have used aeropoxy for several years installing the hinges on my jets, flat hinges, robart hinge points, and BVM's new carbon fiber hinges (my latest Phantom and the F-100) and I have never had a hinge pull out. I squirt some in the hole, and smear a little on the hinge. The aeropoxy gives me some time to get the hinges positioned perfectly, and I can also use some alcohol to clean the excess glue up before it sets. Use a Q-tip to clean with.

David Reid

747drvr

My Feedback: (5)

Yah, I guess since they are plastic you can probably clean them up with an exacto

747drvr

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David,


Do you pin the flat hinges ?

PR38

Hey have any of you guys used the Beckman concealed actuators from Hobby Lobby? If so, what did you think? Are they reliable? IS there much slop? Will they take a lot of load?

DavidR

My Feedback: (1)

I have pinned them before but if you rough them up with a little 80 grit sandpaper there is really no need to pin them.

I would not use anything other than a good hinge, and solid pushrod/control horn setup for any flying surface on a jet, or high performance airplane.

David Reid

Brian B

My Feedback: (5)

I like the 1/4 scale Klett flat hinges. It is really easy to make a slot in the TE and aileron/elevator/rudder. Then I rough up the surface of the hinge with 40 grit, and glue them in with 30 min epoxy. I don't pin them. They are in there so tight, you would need a D9 Cat to pull one out.

F9F Texan

I've been using Robart Pin hinges for the last few projects, but I've used Klett & Dubro 1/4 scale(they're virtually the same to me)

I preferred Dubro because they had removable pins which I would usually replace with the appropriate size piano wire making the surface removable. I always thought it strange that smaller Dubro hinges didn't have removable pins, but smaller Klett hinges did. With the 1/4 scale size it was reversed.

JA

rpz-RCU

Hey there - I've also been looking at these concealed actuators - that might have been lost a few posts ago, but I'd like to know if anyone has had any experience with them... They look good on paper - how 'bout real life?

Randy

winship

To keep paint and even CA out of a hinge joint dip hinge barrel in heated Vaseline. I put the Vaseline in a jar lid just deep enough for the hinge barrel to submerge itself when bottoming out. Fold hinge back upon itself and squeeze/flex hinge so the heated Vaseline will wick better in the pin joint. Set aside to dry and wipe off excess Vaseline off of hinge joint.

Vice Grips are used to hold lid while heating with propane torch or heat gun. Place Vice Grips in bench vise. I usually get the Vaseline smoking a little bit before dipping hinge. Better wicking action.

The Vaseline is used since it will not migrate like other oils will and contaminate the hinge tab.

By using this method you will be able to use thin CA to install hinges. Although on a jet or larger models I would use epoxy or the other methods listed above.

Try a test sample with thin CA for medium sized models and you will be surprised how you can make a flat tabbed pinned hinge become a CA hinge.

CobraJet

My Feedback: (4)

Randy,
From what I've seen and read there is torsion in these type of concealed actuators. This is not good in a jet and would likely induce flutter in the control surface and/or strip the torque shaft.
I have not used these hinges only seen and handled them.

Woketman

My Feedback: (6)

Tom is correct. The "control rod" in these pocket type hinges is actually a torsion rod. The control force is transmitted from the servo as a torque or twist in the rod. We can hit some hefty control surface forces in our jets and need a very stiff control set up. The pocket type systems that I have personally seen did not, in my opinion, have a beefy enough torsion member for our use. That is not to say it can not be done (it can), just that the ones I've seen were inadequate due primarily to too much torsional flexsure.

(rocket structural analyst for 22.5 years)

747drvr

My Feedback: (5)

Hi Guys,

Tha actuator that PR38 was refering to is a different unit than the RADS with the torque tube. I've attached a photo of the "Beckman actuator". I'm not sure how strong it is but it's a neat concept. Perhaps a bomber machined version could be made for high load use.

As for the RADS, I presently have a few prop jobs that are incorporating this method. I haven't completed either yet but it does make a lot of sense to me. I may incorporate it in a jet but the adapter will be machine from aluminum with only a very short piece of wire at the end to go in the pocket.

Thanks for all the comments regarding hinging. I guess pinning the flat hinges isn't as important if you scuff the hinges first ?

DavidR

My Feedback: (1)

Marc,

One other thing I just thought of. I used some hayes flat hinges on the rudders of my Bobcat (came with the kit) they are very good and you can't tear them normally. I got a little too agressive with the sandpaper, actually the coarse side of a permagrit tool and the hing broke at that point. So a little scuffing goes a long way.

DR

CobraJet

My Feedback: (4)

I believe it also requires you to mount the servo close to the trailing edge to minimize the torsion and if I remember correctly the servo is mounted at an angle. With the thin trailing edges found in most of the jet airframes this type of mounting could be a challenge.