Hinge Question

[Dick Pacini]

What is the general opinion of Robart Pin Hinges vs Dubro type?

[Paul Smith]

I did a plane with Robart hinge points once.  OK in many ways.  But two downsides:

1. You need top drill a BIG hole.  So if the structure is thin, you can't use 'em.

2.  There is no really positive wy to assure that they won't rotate and lock up.

On the plus side, it's easier to drill a hole vs cut a slot.

[Mark Scarborough]

I did a plane with Robart hinge points once.  OK in many ways.  But two downsides:

1. You need top drill a BIG hole.  So if the structure is thin, you can't use 'em.

2.  There is no really positive wy to assure that they won't rotate and lock up.

On the plus side, it's easier to drill a hole vs cut a slot.

HUH?
1.big hole, as I recall the hole is like what, less than an 1/8 of an inch, thats not big and if your talking about the depth, then its the same idea as with a pinned hinge

2.lets see, when you epoxy them in place, I am thinking they probably wont rotate to darn much ,,
the only issue I have had with them is when you epoxy them in, getting them aligned initially. I made a little fixture out of scrap that would allow me to align them and they were ok but since I was shown a method of doing standard pinned hinges that is pretty foolproof, I would rather use them

[Paul Wood]

You can get these hinges in several different sizes.  The smaller ones (not the park flyer sizes!) are plenty strong and only require a small hole.  I only mount them in one surface at a time and allow the glue to cure.  I insert them, clean the excess glue with a Q-Tip and alcohol, then pull them down 90 degrees to the suface.  You can tell immediately if they need to be twisted a little to align them all exactly.  I just completed a Profile Oriental and used them with no problem.  I've used them for many years in R/C and never had one fail.

Paul

[Allan Perret]

I have used them on 1/2a's thru 60-size.  They work fine, just a different installation technique.

[Mike Keville]

I used the smallest ("mini") Robart hinges on the 3/16" tail surfaces of the profile A-26.  They worked just fine.

[Dick Pacini]

I was hoping someone would comment on how free they are when installed.

[Paul Wood]

Dick,

They are very free when installed correctly.  By that I mean the alignment of the hinge pin is important, but easy to "eyeball" when you install them.  But, the most important thing is to keep the hinge pin absolutely free of glue.  Many techniques, but the easiest for me is to put a small drop of light weight oil on the pin before I glue the hinge.  Some use a light smear of Vaseline and that also works well.  The secret for me is to NOT use epoxy.  I use water based glue such as Pacer canopy glue, Elmers carpenter glue, Titebond, etc.  If you build the hinge pocket so that the hole does not go all the way through into the bay, the glue is captured and will penetrate the wood for a very tight fit.  As the glue squeezes out, I clean it well with a wet Q-tip and set the wing/stab so that gravity will pull the glue into the hole, not out toward the hinge.  Same for the control surface.  I keep checking for glue leaking into the the hinge pin until I'm convinced the glue has begun to set, usually just a few minutes.  The control surface should fall from it's own weight if all is done carefully.

Paul

[Allan Perret]

I agree with Paul, properly installed they are as free as any other hinge out there.  
Pacer makes a special hinge glue (also water based) which etches the plastic giving it a better hold than regular aliphatics.  
I have confirmed this with glueing samples.  product # PT-55

You can also get the Robart hinges un-assembled (no pins) and use a continuous length of wire for a single hinge pin per panel.  
I did this with my recently finished RMD-3 (using barrel type hinges).  Some advantages, control surfaces are removable,
 better access if you have to clean any glue squeeze out, and the wire fills the hinge line gap.  
The RMD-3 flies great without having to seal the hinge line, and the controls are silky smooth...

I built a Stearman, used Robart hinges.  I built in sections of Everygreen plastic tubing to make sockets for the Robart hinges.  
So I ended up with plastic to plastic glue joint when I installed the hinges, worked good.  
This made it easier and neater to install hinges after the model was completely finished.    
The Evergreen tubing comes in telescoping sizes, which you can use to aid in aligning the mating sockets,  and also to keep surfaces aligned while painting.

[Randy Powell]

Dick,

I've used them several times and am using them on the plane I'm building right now. Check the freedom of movement first as some have some flashing that it's helpful to clean out before installation. If you drop them 90° when installing, it's pretty easy to get them aligned. I got the little tool that comes with a big pack of them. It's a drill guide and seems to work pretty well.