Countersinking Trim Tab Hinge

[blueisthenewblack]

Yes, I am using the plate as the female die. The two hole sizes where to test the DIENQ die vs a standard 120 degree die. The DIENQ worked out just fine so I haven't been using the #30 countersunk hole.

Thank you, Scott. I'm just about ready to dimple the trim tab. I plan to try countersinking the hinge on some scrap using Dan's description and also try dimpling the spar on some scrap using your method to see which one I like better.

[Jinkers]

Thanks for the method! Sounds like you're using the steel plate as the female end while using the male die to form the dimple. You mentioned a #30 in one corner and a #40 in the other corner, why is this? Were you using DIENQ with one hole size and the 120 degree die with the other?

Yes, I am using the plate as the female die. The two hole sizes where to test the DIENQ die vs a standard 120 degree die. The DIENQ worked out just fine so I haven't been using the #30 countersunk hole.

[blueisthenewblack]

1/4"x4"x12" steel plate. Drilled a #30 hole in one corner and a #40 hole in the other and counter sunk to proper depth. Mounted it to the work bench overhanging 2". Cut out some 1/4" plywood to support the hinge while dimpling. Drilled a hole of proper size to hold a male of of a dimple die in the end of a brass rod. This is used to dimple the trim tab spar and the squeezer or C-frame is used for the hing and trim tab.

Thanks for the method! Sounds like you're using the steel plate as the female end while using the male die to form the dimple. You mentioned a #30 in one corner and a #40 in the other corner, why is this? Were you using DIENQ with one hole size and the 120 degree die with the other?

[Jinkers]

Here is an alternative method I used for dimpling the trim tab spar. Not original but it works.


1/4"x4"x12" steel plate. Drilled a #30 hole in one corner and a #40 hole in the other and counter sunk to proper depth. Mounted it to the work bench overhanging 2". Cut out some 1/4" plywood to support the hinge while dimpling. Drilled a hole of proper size to hold a male of of a dimple die in the end of a brass rod. This is used to dimple the trim tab spar and the squeezer or C-frame is used for the hing and trim tab.

I tried a normal 120 deg dimple die and the DIENQ die. Both worked but the DIENQ and then reaming with a #30 reamer makes the tightest fit.

Hinge_Dimpler01.jpg

Hinge_Dimpler02.jpg

Hinge_Dimpler03.jpg

[GlenNJ]

For those starting a Panther build, there is a fairly easy way to dimple the trim tab spar (top and bottom). I choose to dimple the top and bottom of the spar, because I didn't want to countersink the hinge. The bottom holes of the trim tab spar can be done with your standard nail dimple die. The top holes requires:
1) Grinding a slight angle on the backside of the female half of the nail dimple die.
2) Cutting a #6 finish nail less than the distance of the dies together (3/8" worked for me).
3) Put a small piece of electrical tape on the backside of the female die, to keep the nail from falling out.
4) Take a small, cheap pair of pliers, and grind the teeth so you can fit them around the dies, but still fit inside the trim tab spar.
It took me less than 1/2 and hour to modify, and make the tools I needed. To test my theory, I made a spar replica out of scrap aluminum, and drilled about 15, #31 test holes. I had no problem with any of the holes, so I dimpled all the holes on my trim tab spar.
The procedure goes like this:
1) Drill you #31 holes in the trim tab spar (the top of the spar, where the hinge will be).
2) Take your female dimple die (make sure you tape the backside so the nail doesn't fall through), and put it in the spar.
3) Hold the female die in place with you finger, line up the holes and drop you cut down #6 finish nail in place.
4) The nail will be sticking out slightly, so drop the male end of the die in place.
5) Take your modified pliers, and hold everything in place.
6) Looking from the side, move things around until you have an equal distance gap on both sides.
7) Squeeze the pliers until there is no longer any gap (it doesn't take much pressure), and you’re done.
It took me around a 1/2 hour to do the whole spar this way, and it worked perfectly. I have a couple of pictures that show the tools, and how it looks when you squeeze a dimple, but I don't know how to load it. I'll work on that.

Glen

[danweseman]

Guys
In general on hinges we would dimple but not always. On the half that is attached to the elevator ,you can dimple the skin, the hinge, and the closer. the closer can be a bit difficult to dimple but it can be done.But on the trim tab this doesn't work. You need to dimple skin, countersink hinge and leave the trim tab spar alone. It is virtually impossible(possible but difficult and you will need to get "creative") to dimple the trim tab spar. slightly "under countersink" the hinge, meaning don't go as deep as typical. it will be a compromise, but airplanes are a series of compromise flying in close formation. The dimple will carry the shear load. this is how the Prototype was built.
If you don't like this option you can fumble around and figure a way to dimple the trim tab spar, or you may simply choose to use protruding head rivets.

[psalter]

Glen,

As you have found out, the hinge is too thin to properly countersink, at least when using 1/8" rivets. It is best to dimple instead of countersink hinges, they will bend on you but can be straightened easily.

About the only place you can countersink on the Panther for skins is along the main spar of the wing, where the spar is 1/8" thick.

Paul

[PlaneDan]

If you have some material the same thickness as the skin, take a small piece and dimple it. Then countersink and test fit using that piece, until it fit's flush. You will be needing to do the same when countersinking the spars on the wings. Don't take this as a "standard" method, it is just the way I did it.

[GlenNJ]

I need to clarify something on my last post. I didn't show the supports that are under the trim tab, and the aft end of the elevator, to lessen the clutter in my drawling. I probably should have included them, because they would probably eliminate any chance of the rivet pulling through the assembly. I'm not sure if the bottom taper of the rivet would be long enough to reach these supports.

Glen

[GlenNJ]

Since this is the first time I'm used a countersinking tool, I want to make sure I'm doing this right. I am flush riveting my tail parts, and I am ready to countersink the elevator trim tab hinge. I make some test parts to check the fit, and I don't know which method is better.
Method #1
If I countersink to the bottom of the hinge, but not past it (120 degrees both parts), I maintain a #30 hole at the bottom of the hinge. The fit seems good, but there is a very slight gap between the top of the hinge and the bottom of the skin.
Method #2
If I counter sink the hinge deep enough to eliminate the gap between the hinge and the skin, the hole at the bottom of the hinge is much larger than a #30 hole. The fit seems loose, and I'm afraid there might be some movement when I rivet things together (mainly because the hole at the bottom of the hinge is much larger than a #30 hole). I'm also afraid the rivet could pull through, because of this large hole.
I'll try to attached a diagram that might help show what I mean.

Glen