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Tail Jig, am I doing the right?

Posted: Sun Jun 02, 2019 12:55 pm
by pilotstretch
Here’s some background on how I built my jig.

1) drew out full size plan on a 2X4 sheet of MDF
2) cut 1x1x2 pine blocks and drilled holes and countersinks
3) put a drop of glue down where I was going to put the block and then lined up the block with my plan lines as best I could by eye then screwed the blocks down, a few slid on the glue a little but most stayed where I wanted them to.

I built half of an elevator on it and it turned out pretty good for my first time. But starting to build a full elevator out of pine for practice I found that there is some gap between my pieces and the blocks. I have four questions.

A) Is this the correct way of building a jig?
B) can I use shims to close up the gap between the blocks and my pieces of wood?
C) should I just remove the out of line pieces and replace them?
D) should I flip the MDF over and start over?

Below are a few pictures of my jig.

Re: Tail Jig, am I doing the right?

Posted: Sun Jun 02, 2019 4:27 pm
by EAB4
You are off to a good start, but honestly, I'd flip the MDF over and start over.
You are going to be hard pressed to get 2 identical pieces out of the existing jig. And that's really the point of the jig, to make sure the parts are the same.

You don't need to glue the blocks, screws are enough (I used nails), but they do need to be snug against the parts.
If your pine pieces are cut accurately, you should be able to clamp or weight the parts down on the drawn lines and then screw the blocks down against the parts.
I started with the main beam, made sure it was lined up, then added the jig blocks. Then worked on the outboard edge, then trailing edge, then inboard edge. That way you can make sure the 2 90* corners are lined up before you line up the inboard edge, then fit the spar.

While most of the strength in the joints will be from the gussets, you do want your pieces to fit pretty close.

Attached are some pictures of my horizontal stab jig if it helps.

Re: Tail Jig, am I doing the right?

Posted: Sun Jun 02, 2019 5:14 pm
by pilotstretch

Thanks for the input, now thinking about it I agree that I wouldn’t get a consistent product. Well that gives me a direction now, I haven’t been working on it much lately so this will be go to get back into it.

Thanks again,


Re: Tail Jig, am I doing the right?

Posted: Tue Jun 04, 2019 10:33 am
by ArthurD
I actually did my tail skeletons a couple weeks ago and I had a pretty similar setup and they all turned out great. I layed out all the lines on an mdf workbench. Some things I did differently were:

I ran some 2x4s through the jointer to get a perfectly straight edge and screwed the mdf to them to keep it flat.

My blocks have a slot in them to allow some adjustment, I also used some lag bolts with a flanged head because drywall screws caused the blocks to split.

I did not glue the blocks because I wanted to reuse the workbench for the other tail parts. Also the screws are plenty strong for this.

I sanded the mdf after each glue up so the blobs of glue that get squeezed out didn't cause any problems.

I positioned the blocks right up against the layout lines put the piece in and then put the blocks on the other side just tight enough to eliminate any movement.

I also recommend not putting the blocks so close to the end because you should get a decent amount of glue squeeze out and might end up gluing your part to the blocks.

For glue I used T-88, I coated the end grain and let it sit open for 30 minutes before adding more glue and fitting the parts up.

Since the main beam is 1" tall, the center beam is 3/4" and the trailing edge is 5/8" you do have the shim the center beam and trailing edge up 1/8" and 3/16" respectively.

Re: Tail Jig, am I doing the right?

Posted: Fri Jun 07, 2019 10:25 pm
by pilotstretch

Thanks, you answered some questions that I was just about to ask. Thank you for sharing.

Joshua Gregg