Thread hinge variations

[Phil Hawkins]

Hey Guys,
I have a few 1/2A kits in progress and I really want to try thread hinges. I searched the forum and found a few pictures, and every one was different. Only one was a close up.
I am going to try this on the 1/2A ships but might end up trying on some as big as, for example, a Ringmaster size.
Hopefully a few of you guys can post a pic or two?

[Tim Wescott]

I'll try to get something later today.  In the mean time -- if you understand how cloth hinges work, thread hinges are basically the same geometry.

Either way, the idea of a thread hing is that the thread rolls over the trailing edge of the stab and the leading edge of the elevator.  Unlike a "regular" hinge, this means that there's no barrels turning on a pin -- instead, the surfaces roll on one another.  This makes for a very friction-free hinge, as long as you don't paint it, or let it get goobered up with glue.

[bill bischoff]

The photo is a Flying Clown with an OS 18. The stab and elevator both have 1/4" wide spruce strips along the hinge line. The hinge holes are drilled into the spruce. This isn't necessary on a 1/2A size airplane. The hinges are dacron 1/2A flying line. One end of the dacron line is saturated with thin CA to stiffen it for easier threading through the holes. Start at the centermost hinge, and sew 3-5 figure eights. Tie a knot and use one end of the line to pull the knot into the hole when you're done. Secure the hinges with a drop of white glue off a toothpick in each hole. White glue allows easier hinge replacement if it's ever necessary, and less chance of gluing the hinges stiff than if you used CA glue.

[Mark Mc]

I tried four or five different variations on the thread hinge for my 1/2As, but finally settled on a sorta-baseball stitch hinge a few years ago.  If the elevator is not a split type, I just start at one end and stitch right across to the other end.  Plenty of freedom of motion and has never failed on me yet.  My go-to hinge material these days is 10# Spectra.  Way overkill.  If I had 5# Spectra I'd use that instead.

This is a terrible drawing I just threw together with MS Paint.



Mark

[Phil Hawkins]

Thanks! I have a better understanding.
I have a few materials to try it, Tuf Strand lines, dacron, even dental floss. Plus all kinds of scrap balsa.

[Tim Wescott]

... The stab and elevator both have 1/4" wide spruce strips ... This isn't necessary on a 1/2A size airplane. ...

If you've found some nice light, strong balsa, it may be necessary.  Or, I pull my thread too tight.  Whichever, I sometimes use a strip of hard balsa or spruce, or if it's a super-light little RC plane with built-up surfaces I'll use hard balsa for the stab TE and elevator LE.

I've always sealed my hinges with dots of CA, and haven't had a problem with it wicking into the working part of the hinge for years.  As for replacement -- aren't you supposed to crash the plane before anything has a chance to wear out?

[Tim Wescott]

Pictures.  I was going to post pictures of all four 1/2-A planes I have, built by three different people -- but the hinges are all the same.  So I'm posting one example of the 1/2-A planes, and the sewn hinge on my Firecat Rescue Plane.  The plain wood stab/elevator is the 1/2-A; the Firecat used to be pretty but, well, now I own it.

[Dave Hull]

Late to the party, but....

I did an article a few years ago for our club newsletter. A portion of that article was specific to sewn hinges---

"Of course, I am also a huge fan of sewn hinges for any racing plane and many sport planes. Just don’t do them the way they were done 'back in the day.' Most often, those looked like sutures you’d see on Frankenstein. Especially if you listened to the guys recommending carpet thread 'for good strength.' Done properly using Spectra line and using only a pair of drilled holes in each location you would have put a slot for a pinned hinge, these look perfectly fine and are incredibly strong and very free-moving. You do need to reinforce the woodwork with a spruce or basswood strip to prevent tearout."

"A properly installed 'sewn hinge' works very well in a number of applications. It is unfortunately named, as you don’t use a needle, you don’t use thread, and there should absolutely be no line of stitches. Sewn hinges are as strong as any other hinge you might compare them with. Note the spruce spars at the hinge line. These are one of the secrets to durability and strength--you can wrap it nice and tight, and once installed not worry about it. For best appearance, if a slight groove is created leading to the holes, the Spectra can be installed and filled over, virtually making the hinge disappear after painting. The hinge gap is uniform and exactly one thickness of the line. In this case .020”.

The included picture is of a 15-sized training ship. These hinges will work on any size airframe.

Dave

[M Spencer]

requires a degree of patiance . Mark & pre Drill holes . if the woods not soft . also score to recess if the woods rock hard !

Probably 3/8 in each side , one half spacing along . Staggered 50 % . UPHOLSTERERS THREAD is way best . Maybe Doubled .



You go along from a knot at the start , pull out the slack every six or so , but not tight .
Once completed , ' Tension Off ' , starting at one end . HOLDING THE ELEVATOR ALIGNED .

I pre Dope & Pre tissue , about 1/4 inch in both sides . Say a 5/8 wide strip , folded to align centre  then  doped on .

Last Ole' is  " IN LINE " half space'd , dual or triple  . And Foist .

Can be DUAL reversed for a fancy pattern 'V' s each side , top & bottom .

[Robert Zambelli]

I have been using thread hinges for over 25 years - NEVER had a failure.
The photo shows the hinges on my Viking, done in 1998.
I use only dental floss, waxed or unwaxed, doesn't seem to matter.
They are incredibly smooth, even if painted over.

Bob Z.

[Steve Helmick]

The photo is a Flying Clown with an OS 18. The stab and elevator both have 1/4" wide spruce strips along the hinge line. The hinge holes are drilled into the spruce. This isn't necessary on a 1/2A size airplane. The hinges are dacron 1/2A flying line. One end of the dacron line is saturated with thin CA to stiffen it for easier threading through the holes. Start at the centermost hinge, and sew 3-5 figure eights. Tie a knot and use one end of the line to pull the knot into the hole when you're done. Secure the hinges with a drop of white glue off a toothpick in each hole. White glue allows easier hinge replacement if it's ever necessary, and less chance of gluing the hinges stiff than if you used CA glue.

Bill's method is exactly the way I did mine on several sets of speed models and a couple of rat racers. The only difference was that I filled the holes with Ambroid and not white glue. Potential for replacement on the field was the main reason, but in actual service, I never had to replace a hinge either at field or shop. I drilled 3/32" holes about 5/16" from the stab TE and elevator LE. They worked so well that I used similar hinges on the rudders of many F1A gliders, except for smaller holes and nylon or dacron thread instead of Dacron 1/2A flying line. Highly recommended for Ringmaster and Flite Streak type models!  Steve

[John Carrodus]

Bill, a beautifully crafted model. I have several questions. What does the cable do on the modified elevator horn- Throttle, fuel shut off? Is the needle valve on the engine RC - and offset to protect the NV? I'd love to see more photos if you are prepared to reveal your secrets to the world!

[John Carrodus]

Bill...
another annoying Q
What is the story with your fuel tank sticking up at the rear?
Cheers
John ( curious Kiwi)

[M Spencer]

Yea , thought there must be something more modern than the upholsterers thread .

1/2 A youd do say 3/8 along and 1/4 in ea. side . If the zig zag pattern .

Biggest snot is ultra soft wood and puling at the holes - elongating - tautening it off .
Super Glue to firm it up might be an idea ? BEFORE the sewing .
With a square edge on the tailplane & radius on the elevator - the action is ' rolling ' ,
so it actually presents quicker & further than a centerline hinge .

For aerobatics , say .35 size up ?the zig zag Id think would work like the L E zigf zag turbulators ,
and assist ' flow attachment , with big thread !
Also say four two inch runs on a 24 inch flap , if the flaps hard wood , the flap acts as a brace fully deflected , to avoid bowing the rear off the wing , under duress . Gales & so forth .