Campgems

I've used the pinned flat hinges for all of my models and have decided to step up the the Robart hinges. I am haveing a problem getting then to set fully. The hinges are 1/8" diameter pins, but the width of the hinge lugs widens out to 0.155". In very light balsa, I can just push the pin in by hand, but the plane I'm re-hinging now has some harder wood on the hinge line. I've searched for help cutting the correct seat for the hinges, and only found one suggestion that you could use a tapered burr to open the drilled hole so you could the the hinge seated fully. That does work, but it also leaves a lot of air over the top and bottom of the hinge line. Where I can cut in the hinges some, IE on the elevator and rudder, I can get around this som buy cutting a rectangle taper with an Xacto knife. My problem is going to be the wings where I have a 7/8" flat TE on the wing that I want the hinge line to be almost on the surface of. To use the larger hole to accomidate the width of the hinge, I need to cut the oversize hole about 1/4" deep to get it where I want it. That doesn't leave much meat on the TE for gluing, event with the back up blocks behind the TE, ahead actually.

Any suggestions???

Don

MinnFlyer

My Feedback: (4)

First of all, the "Fat" area doesn't really need to be seated tightly - or even glued for that matter. It's the ribbed section that the glue really grip onto.

As for setting the hinges near the top of a hinge line, angle then downward like this:

tmproff

My Feedback: (5)

I always use triangle stock between the TE of my wing and the control surface. This gives a large range of movement without creating a big gap. Where I am about to put the hinge point, I cut out a 1/4 inch section of the triangle stock that was glued to the TE, and then I drill a hole. This way, the large area of the hinge (where the pin is) seats inside the triangle stock.

planebuilder66

My Feedback: (8)

The nice thing about robart hinge points is you can build with scale hinging, just round the leading edge, recess the pin section in the center of the radius, notch top and bottom for throw deflection and set it up to be almost 0 gap between trailing edge. The surface will piviot around the pins centerline, if you've done you homework well, it will move like magic and provide a smooth flying surface for airflow over it.You could even add sheeting lips to the top and bottom of the trailing edge and smooth out the airflow even more.

SPLIT S

On flat trailing edges I use this tapered stone from Dremel. The taper of the stone matches the taper of the hinge point perfectly. I can seat the hinge fully without an excess of wood removed from the trailing edge. Makes for a snug fit. For the flaps on my JetMach, I made a crude (but works well) jig to drill the 1/8" holes in the trailing edge of the wing and the leading edge of the flap. Puts the hole right where you want it at a consistant angle throughout.

Dan

Campgems

Wow, lots of good info. I'll boil down what you all have said and let me know if I'm wrong.

1. A loose fit on the flaired area around the hinge pin is not a problem.

2. Set the hinge point into the control surface, not the TE of the wing, or either of the stabs.

3. by all means use them.


My first attempt was on the ailerons of a GP Super Aeromaster bipe I built last year, I gave up in frustration and went to the Dubro pined hinges. Bad choice. I ended up with one aileron high by about 3/32 on one wing tip. I have yet tried to fly the plane because of this and Looking back, I should have addressed my frustration then. Anyway, I'm just finishing up a new wing and replacement of all the hinges and control horns on the Ruperts Dad I built a couple years back, my first build in close to 40 years. Hinge points were not around back then, Over/under cloths strips were the norm then. Couldn't get them right either

Iv'e got a few of those taper dremil grinding bits. I'll give them a try. So far, I really like the hing points better than the flat dubro pined hinges. It is a lot easier to hit the center line with a drill rather than the slot machine. I'm also discovering how easy it is to build drill jigs, not only for the hinges, but for the locating dowels in the LE of the wing. A couple scraps of wood and balsa any you have your jig.

Don't wan't to make this to easy, or I'll have to build an addition on the garage to hold all the planes. Actually, it getting hard walking around it now.

Don

MinnFlyer

My Feedback: (4)

Don, what Planebuilder was talking about was IF you wanted to do round LEs on the control surface similar to this illustration. This can be pretty tough to get the geometry right.

planebuilder66

My Feedback: (8)

I've used bolth applications, the one you talked about and the one I talked about on 1 plane, my topflite P-47, the flaps I used a jig to align the hinge points for the fowler style flaps(even though it's not true scale hinging), and on all the other surfaces, they were rounded and installed like your picture you drew. that bird is rock solid throughout the entine flight envelope, when I drop the flaps to 30 degrees and setup for final, it can actually land within 50 -70 feet it's going so slow, but I have total control, due to almost no gap and havong a lot of throw on tap if needed.

dbacque

My Feedback: (3)

I just use an X-acto knife and square out the entrance of the drilled hole. Test fit the hinge and trim more if required. It's quick and easy and I think it's kinda fun.

Grinding the round hole out bigger will work but I always go for as perfect a fit on everything I can because a tighter fit equals less glue and less glue equals a lighter airplane.

Dave

Campgems

I'm hinging a 3D wing, It has a 3/4" flat TE on the wing it's self, and the aileron had a 45 degree angle, tri stock glued to a flat LE. I'll be ablt to cut into the LE of a aileron a little bit, but ideally, the hinge pin will be along the sharp LE of the aileron. I'll taper, or actually step cut the taper with jewelers burs. I just did the rudder and it is going to workd out OK. However, on that surface, the plans called for a round edge on both the TE of the vertical stab and the LE of the rudder. That required quite a gap to get full movement and I'm trying to get around this gap with the re-hinge. I had to cut shape the LE of the rudder some for full movement. It is going to work OK. THe elevator will be that same story. Sure would have been nice to have been able to remove the old hinge tabs, but I just cut the lugs off and ground the tab down below the balsa surface. THis allowed some shapping of the LE, but will not let me get a sharp edge.

Assuming tihis goes OK, I'm going to re-hinge the ailerons on my Supper Areromater. Then I can get back to some real building again.

Thanks for all the help guys. Even if an answer didn't really address my situation, I would learn from it.

Don

sscherin

My Feedback: (1)

Everyone has a different method.. The best I've found is on the Airfield models site.
http://www.airfieldmodels.com/inform..._points/03.htm
http://www.airfieldmodels.com/inform..._points/05.htm

I like his method of drilling both the surface and TE together on a press for perfect alignment then cutting the bevel after the holes are done.
I use a router table for the bevel.. small Table saw or hand plane also works.

As for fitting the taper on the hinge.. I use a small square jewelers file to open up the hinge pocket. make for a nice fit with the square shank on the hinge.

This is the hinge line on my Stick using the Airfield methods