The one thing I have never like about DTF planes are the hinges. Paper, hot glue, tape. None of them ever really lived up to my expectations. The paper delams. The tape comes off. Glue isn't much better. And DTF tends to bend, especially if your horn is offset to one side.
Out of frustration with some on a build I decide to experiment with the old way of hinging, sowing them. And ya know what? These work awesome. It fixes a couple inherit problems, is actually easy to do, and is very inexpensive to do.
The one advantage I found was the better control it gives. Since the hinge is running the whole edge of the control, torque is transferred better. Off set the horn way to one side and the other end will still move with it, no DTF bending. The non horn side moves as much as the horned side.
This work on all control surfaces. Ailerons, elevators, rudder, whatever.
(in addition to your plane and standard FT weapons of destruction)
For a longer hinge
1/8” 36” long doweling $0.30/ piece in the craft section of Walmart.
Some polyester thread. Any color you want. It don't matter.
A sewing needle.
A small tube of super glue.
Needle nose pliers or a hemostat are recommended. I use a hemostat.
You will want to use polyester thread. Cotton thread, from what I have been told, is a bad choice. It wears faster. Polyester is naturally smoother. That isn't really an issue. These hinges will outlast your plane easily. Also, I have been told cotton doesn't like CA. The CA weakens it.
My thread of choice is 30 lb test Spiderwire EZ Braid Fishing Line. Strong and smooth. Your hinges will be the strongest part of your plane. And they work very smoothly.
For ease in this write up I just used a scrap piece and faked a hinge. I'm in between projects. But the process is the same no matter what control surface it is, aileron, elevator, rudder, flaps.
Prep the Skewers
Take the bamboo skewers and cut the pointy end off and cut them to length. Make them as long as the hinged surface.
Cutting Your Control Surfaces
As you're building your wing you will want to completely cut the control surface out. Cut all the way through. NO BEVEL! Straight cut.
Adding the skewer or doweling will add about 1/4” to the overall width of the surface. On wing ailerons it usually isn’t a problem. But on rudders and elevators it may cause some clearance issues.
If it does simply cut a 1/8” strip the same length as the skewer from the edges of the control surfaces and recess the skewer into the surface. You may need to adjust the recess, not all skewers are the same diameter.
Glue the Skewers
Take your hot melt glue gun and glue a skewer to the edges of the control surfaces. If it's a long hinge I like to use the 1/8 inch doweling. It's cheap (27 cents a piece for 36”) and looks nicer than splicing skewers.
But if you want you can still use the skewers. Offset the joints of the skewers so the gap doesn't line up. A joint on the left side of the wing, a joint on the right of the aileron. You’ll want to make sure there is enough room for a stitch near the end of every skewer. Give yourself at lest a couple inches of overlap. It will still work great. You'll just have a few extra stitches to do.
Make sure they are centered on the edge of the DTF. If they move off center it throws the hinge off a little.
Mark Your Hinges
Lay your parts out and determine where your hinges are going to be.
I usually have one about ½ to an inch in from each end.
For really short hinges that may be enough.
For medium ones, a third in the middle.
For long ones, two more evenly spaced.
Even on a really long hinge, like the Explorer with full length ailes, four seems to be enough. I haven’t needed five unless I spliced the skewers.
If you had to splice the skewers for length you'll want one about ½ inch on either side of the joints. The short side should have two. The long side four.
Non spliced layout
Line up the hinged surface with the non hinged surface where it will wind up being. For this step, taping it in place helps, but not necessary.
Make a small mark on each surface where your hinges will be. The marks need to be straight across of each other. If their off, it will pull you hinge to one side.
Take the needle, not threaded yet, and poke through where you made the marks. Go in between the foam and the skewer where the glue is. If the hole is in the foam it will eventually pull through to the skewer and loosen up.
Wiggle the needle around in the hole and enlarge it just a little. It makes sowing easier.
Repeat for the rest of the holes, both hinged and unhinged surface.
I start with the hinged surface. Easier to start.
Cut a piece of thread about a foot and a half long.
Thread it through the needle.
Start on one end, not in the middle.
From the top, thread the needle down through the little hole.
Pull it through and leave two or three inches of thread on the top
Wrap the needle end around the skewer back to the top.
Tie the two ends together with a small knot and pull it tight.
Be careful tying the two ends together. If you slip pulling on the thread you'll give your self a nasty cut. That’s where the needle nose pliers, or better yet a hemostat, come in. Use them to pull the knot tight. The long end isn't too bad. You can get a wrap and get a good grip. It's the short end you have to watch.
Take and pull the knot so it is directly above the hole. Lay both ends of the thread so they run flat and straight out the control surface.
Put a very small drop of CA on the knot and give it time to dry completely.
Joing Them Together
Align the two surfaces in place. A couple temporary pieces of tape will help hold them while your working.
Leave the loose end hanging straight off the end. I usually leave the hemostat on it to keep it tight and out of the way.
Now we are just going to do a few figure 8 loops around the skewers.
Run the needle down through the hole in the hinged surface.
Poke the needle up between the skewers, the center of the hinge.
Then go down through the unhinged, surface back up through the center, and down through the first hole.
Now to help stop the string from rubbing on itself, what ever side the first stitch was on, go back up on that side of the stitch, come back on the other. Let's say keep all the stitches running away from the hinged surface on the right, towards it on the left.
Just remember, down between a skewer and foam, and up between the skewers. Away from the control surface to one side, towards it on the other.
Pull the thread tight after each loop. Really as tight you can with out over stressing the thread or slipping and cutting your hand. In the pic I didn't pull it tight so it would photograph a little better.
Repeat until there are about four to six wraps around the skewers on both sides.
You want to finish with the needle end of thread on the side with the loose end of thread. It should be on bottom after going through the hole.
The hinge works by rolling around the skewers. If it's loose and slipping around them the thread will eventually cut the skewer in two. So make it tights all pulled tight.
Run the needle Up through the skewers.
Then down through the hole and up through between the skewers. Leave a small amount of slack on top in this loop.
Run the needle through the loop you just made. Keep the loop and knot to one side so you aren’t tying around the hinge.
Pull it tight. Try to pull the knot around so it is above the hole.
Repeat tying the loop knot once more.
Put a small dab of CA on the knot and let it dry.
Now repeat all that on the other end.
Then for the middle.
Take the hinged surface and hold it flat so it's pointing straight out from the unhinged side. It should be even. If it's a little high or low you can gently move it so it's even.
Last drop of glue
Take and place another drop of CA on either side of every hole. Keep it small. The CA will try to wick out into the part that needs to hinge if you use to much.
Trim Off the Extra Thread
Take your Exacto or scissors and trim the loose threads off. They can be close. The knot is glued.
Lastly. The CA always wicks through the thread just a little. Just work the hinge back and forth a few times to loosen it up.
And we're done!
Like everything else sowing hinges takes a little practice and the first one might take a bit.
But they are such vast improvement over standard paper hinges I wouldn't even think of doing anything else any more. Stronger, longer lasting, and improved performance. This is a mod definitely worth trying at least once.
No presure. Just where it flopped to after working it just a little flipping it around in my hand.
Explorer with the Sport Wing
Close up of tail
Close up of aileron
I used the 1/8" dowling cut to size.
A non FT plane tail