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Author Topic: flap hinges  (Read 2031 times)

Offline Jim Morris

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flap hinges
« on: August 01, 2022, 09:03:45 AM »
Quick question. How many hinges does one use on each wing panel for the flaps? Thanks. (full sized ship)

Online Ken Culbertson

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Re: flap hinges
« Reply #1 on: August 01, 2022, 09:23:37 AM »
Quick question. How many hinges does one use on each wing panel for the flaps? Thanks. (full sized ship)
With DuBro I use 5.  Two at the end of the flap 1" apart.  One 1" from the flap horn and the other 2 evenly spaced in-between.  With Robarts I use 4.  Skip the extra one at the tip.  Probably will use 2 there in the future.  Both are removable.

Ken
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Offline Jim Morris

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Re: flap hinges
« Reply #2 on: August 01, 2022, 09:41:45 AM »
With DuBro I use 5.  Two at the end of the flap 1" apart.  One 1" from the flap horn and the other 2 evenly spaced in-between.  With Robarts I use 4.  Skip the extra one at the tip.  Probably will use 2 there in the future.  Both are removable.

Ken
Thanks Ken. I am using the Robart hinges for the first time. You answered what I needed. I will use two out at the tip, which I have always done. Its been a minute for me to build and didnt want to over do the hinges. Thanks again.

Online Ken Culbertson

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Re: flap hinges
« Reply #3 on: August 01, 2022, 10:46:20 AM »
If you are using Robarts for the first time here are some things I have learned over the years.  Use pockets but prepare them.  Cut off the ends and shorten the hinge post by 3/8".  Anything past the set screw is just extra weight.  Put the set screws into the pockets and carefully thread them so that they seat properly.  Back them out just enough to allow the hinge to slip in and out and leave them in permanently.  Find the aluminum tube that will fit over the set screw post and put a piece of it over the post after gluing the pocket in.  I am attaching a picture.  Wish it were less fuzzy.

Ken

One more, well maybe two more things.  Buy extra pockets.  The set screws are tiny and impossible to find, and you will lose two of them to the shop floor before it is over.  A large magnet bar helps but they bounce.  Don't glue the hinge in until you are 150-200% sure that they are alligned.  You think a DuBro is hard to dig out, wait till you try a Roberts!  Is it worth it - yes.

If you worry about the set screw pits looking bad, cover them with a square of Monokote if monokoted or draw a panel line around them.  That is what I am going to do with the one in the pictures. I have these pots all over my planes for hatches.  Real planes are covered with decals pointing to hatch access fasteners.  Why not ours!
« Last Edit: August 01, 2022, 11:19:52 AM by Ken Culbertson »
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Offline Jim Morris

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Re: flap hinges
« Reply #4 on: August 01, 2022, 02:27:58 PM »
If you are using Robarts for the first time here are some things I have learned over the years.  Use pockets but prepare them.  Cut off the ends and shorten the hinge post by 3/8".  Anything past the set screw is just extra weight.  Put the set screws into the pockets and carefully thread them so that they seat properly.  Back them out just enough to allow the hinge to slip in and out and leave them in permanently.  Find the aluminum tube that will fit over the set screw post and put a piece of it over the post after gluing the pocket in.  I am attaching a picture.  Wish it were less fuzzy.

Ken

One more, well maybe two more things.  Buy extra pockets.  The set screws are tiny and impossible to find, and you will lose two of them to the shop floor before it is over.  A large magnet bar helps but they bounce.  Don't glue the hinge in until you are 150-200% sure that they are alligned.  You think a DuBro is hard to dig out, wait till you try a Roberts!  Is it worth it - yes.

If you worry about the set screw pits looking bad, cover them with a square of Monokote if monokoted or draw a panel line around them.  That is what I am going to do with the one in the pictures. I have these pots all over my planes for hatches.  Real planes are covered with decals pointing to hatch access fasteners.  Why not ours!
I got to reading and was asking myself, what set screw and what are these pots?. so I googled these hinges and found out. I must say I will just be gluing the hinges strait in. They will not be removeable which is fine. Maybe the next one I will incorporate the pods ect. I didnt even know the pots were part of it.

Online Ken Culbertson

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Re: flap hinges
« Reply #5 on: August 01, 2022, 02:56:47 PM »
I got to reading and was asking myself, what set screw and what are these pots?. so I googled these hinges and found out. I must say I will just be gluing the hinges strait in. They will not be removeable which is fine. Maybe the next one I will incorporate the pods ect. I didnt even know the pots were part of it.
No problem but you will want to investigate the pockets for later.  If you are going to just glue them in be super careful not to get any glue on the hinge itself.  You can free up a DuBro if you get a little careless but not a Robarts.  They hold quite well with that long shaft so it doesn't take much glue.  I drill small holes into the wing touching the hinge and use one of those super fine CA applicators to push in and squirt in some thin CA.  It will grab the hinge with no chance of getting any on the moving parts.
I also oil the cylinder just in case.  If you must use Epoxy or slow cure CA put it deep into the hole because when you push in the hinge shaft it is going to try and ooze out.  Go slow.  I keep the hinges straight by bending them 90 degrees down so that you can eyeball them.  They are super easy to get rotated without the pocket to center them.

Good Luck!  - Ken
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Offline Jim Morris

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Re: flap hinges
« Reply #6 on: August 01, 2022, 03:09:25 PM »
No problem but you will want to investigate the pockets for later.  If you are going to just glue them in be super careful not to get any glue on the hinge itself.  You can free up a DuBro if you get a little careless but not a Robarts.  They hold quite well with that long shaft so it doesn't take much glue.  I drill small holes into the wing touching the hinge and use one of those super fine CA applicators to push in and squirt in some thin CA.  It will grab the hinge with no chance of getting any on the moving parts.
I also oil the cylinder just in case.  If you must use Epoxy or slow cure CA put it deep into the hole because when you push in the hinge shaft it is going to try and ooze out.  Go slow.  I keep the hinges straight by bending them 90 degrees down so that you can eyeball them.  They are super easy to get rotated without the pocket to center them.

Good Luck!  - Ken
Thank you sir!

Offline Trostle

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Re: flap hinges
« Reply #7 on: August 02, 2022, 10:41:59 AM »
No matter how you install those Robart hinges - with or without the pockets, you need to be very careful when you glue the hinges into position.  I always use epoxy.  To assure that no epoxy gets into the hinge itself, suggest that you apply a small amount of Vaseline on the hinge barrel itself so that even if epoxy might get to the hinge barrel, it cannot get into the hinge itself. (cotton Q-tips help with this.)  After the epoxy cures, the excess Vaseline can be removed with the benefit that some residual might remain in the hinge itself for the initial lubrication you would want anyway.

This has probably been explained many times by many before this.

Keith
« Last Edit: August 04, 2022, 11:56:56 AM by Trostle »

Offline Colin McRae

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Re: flap hinges
« Reply #8 on: August 31, 2022, 06:33:03 PM »
FYI

I saw a video on Robart pin hinge install. A cool trick I saw was that the guy used Vaseline petroleum jelly (versus oil) to coat the hinge point so epoxy does not get into the hinge. However, he heated up the Vaseline w/ a micro torch to the consistency of water (did not boil it, just enough heat to turn it to liquid form), then folded over and dipped the hinge point in the liquid and put them aside. Within a few minutes the jelly re-gelled. Then installed the hinge.

I tried the method myself and it worked great. No oil all over the hinge and no epoxy in the hinge point.

Here is the video.


Offline Onelife

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Re: flap hinges
« Reply #9 on: October 16, 2022, 07:57:30 AM »
I don’t want to hijack this thread but I figured why start a new one. My question is I am building a old s1 ringmaster and the elevator is only 3/16. I have used those cloth / paper hinges you just slice the balsa and slid the hinges in but after you use CA and do you painting they get stiff is that a big problem? I never flew a u- control with a free moving hinge is there a big difference?
I could remake stabilizer and rudder using 1/4 inch and go with plastic hinges and a metal control horn from brodak but it’s a 12 gram difference in weight.

Online Ken Culbertson

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Re: flap hinges
« Reply #10 on: October 16, 2022, 10:01:05 AM »
.... they get stiff is that a big problem?
It is always undesirable but it depends totally on the application and just how stiff it is to know if it is a "problem".  If you are flying an Electric PA ship then even stiffness without any binding *can* become an issue but with a flapless Ringmaster probably not.  Binding, that is bad anywhere but some stiffness (without slop) is not that big of a deal on an elevator only plane. 

Over/Under cloth hinges work great on stabs like the Ringmaster and they generally loosen up and also "seal" the gap.  Large Du-Bro nylon hinges will easily slot into 3/16,  and if alligned properly are "floppy free" - AND easily make your elevator removable.  You would need to seal the gap which is explained about 100 times on other threads.  Do a search on "sealing hinge" lines.  If the wood on your stab is good then you really won't gain much by going to 1/4"

Ken

After reading Brett's post I realized you were talking about a totally different kind of hinge than the one I was picturing.  Brett is right, those hinges are totally inappropriate for control line.  No hinge that allows the elevator to "spring back" should be used.

« Last Edit: October 16, 2022, 08:27:45 PM by Ken Culbertson »
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Online Brett Buck

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Re: flap hinges
« Reply #11 on: October 16, 2022, 08:03:09 PM »
I don’t want to hijack this thread but I figured why start a new one. My question is I am building a old s1 ringmaster and the elevator is only 3/16. I have used those cloth / paper hinges you just slice the balsa and slid the hinges in but after you use CA and do you painting they get stiff is that a big problem? I never flew a u- control with a free moving hinge is there a big difference?


   That can be a *huge* problem. They are OK on RC models because the servo always has a lot of torque to move the controls, and will (since it is a feedback control system) get to the desired position no matter how stiff unless the torque capability is exceeded.

   On a CL model, the only thing you have to move the controls with is line tension and the mechanical advantage of the control system (bellcrank and horn) and with any sort of spring system, like CA hinges, will always reduce the throw from a free system. Worse, the elevator or flap deflection will vary as the line tension varies even with no other control motion on your part.

     There are plenty of alternate hinge systems for thin surfaces but a mere 1/2 ounce is *nothing* compared to having free controls.

    Brett


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