Hatz Biplane Association

I am starting to build my jigs for the wing ribs (promised my wife I would not start till I finished up my IFR... I am close). Well I really like the way Doug Mowry built his jig:

http://www.damowry.com/hatz/displayimag ... play_media

The question I have is that I have read that you don't want too much clamp pressure on the gussets.... something about squeezing out too much of the epoxy from between the wood pieces.

So am I over thinking this, or is this really a concern?

You can buy ratcheting clamps (like below), but they sure do cost a lot more:

http://www.gatzies.com/p-67413-master-m ... 4AodcE8AIA

So is it worth the extra money to buy these clamps, and does anyone have a good idea of how big a clamp you need to buy (the smaller the cheaper, and I really need somewhere between 20 and 50 of them).

Tlandrum,
I started out with the ratchet clamps but switched to spring clamps from Harbor Freights.
http://www.harborfreight.com/2-12-nylon ... 69290.html
I bought about 20 of them but could always use more. The ratchet clamps are handy but they are hard to squeeze without moving the gusset. I also think the clamping pressure is too much. It is either one click or the next.
I also bought a bunch of these but they are junk, they don't stay tight.
http://www.harborfreight.com/12-ratchet ... 68975.html
This turned out to be my favorite clamp for using on the wing, it is metal and doesn't slip.
http://www.harborfreight.com/12-inch-ba ... 96214.html
It is available in different lengths and you can't have to many in various lengths.
Yes you can squeeze out to much of the glue with the ratchet clamp but I don't think it is a concern with the spring clamp and a 1/2 or 3/4 piece of plywood.
The spring clamp lists a clamping force of 26 lbs, I like it better than the style Doug used because they have swivel pads on the jaws.
I didn't use ratchet clamps on the ribs but I did use them elsewhere so you still might think about picking up a few.

There are no hard specs for T-88 clamping pressure. I went with what seemed to work well and not be too heavy. I agree with Ed that clamps with movable jaws could be better. The ones I used would sometimes "creep" when you let go of them and move the gusset a bit. Once I figured out what was going on I got pretty good at getting the clamps on right and it wasn't that big of a problem. All my test glue joints were fine and all failed at the wood and not at the glue joint.

If you decide to go with spring clamps buy enough to do two ribs. I would build a rib in the jig and then take the previous rib and flip it over to glue "side 2". The whole process would take around 1.5 hours so once I got going I would complete one rib per night.

This link will take you to a list of Hatz builder sites. Interesting to see the various ways builders accomplish the same task. Good luck.

http://www.hatzbiplane.com/builders.html

I actually preferred the ratchet type clamps I used from Menards/Amazon. Just felt I had more control over the pressure applied vs spring clamps. Never felt I was applying too much pressure. They too have the swivel pads to them. I didn't notice any trouble with the gussets moving when pressure was applied. That may be a function of how much epoxy is used.

Bottom line, either type works, but you are very correct to be concerned to not express too much epoxy fron the joint. On the other side of the coin, too much epoxy really doesn't gain you anything except more weight. You'll get a feel for the appropriate amount of pressure to apply.

Just don't get epoxy on your glasses or in your hair. Not that I did that or anything.......

I used an office type stapler to hold the gussets in place while the T-88 set up. I placed strips of thick paper (or thin cardboard) under each staple to make it easier to work a small screw driver under the staple when it was time to remove them. It also keeps from leaving dents in the ply. Works quick and easy and you can do one side, pop it out of the jig and do the other side. You can build rib after rib until you run out of staples, glue or interest.

I have another method that worked for me:
A plywood board with the plans glued onto it, and long screws protruding from the bottom. Narrow pieces of plywood with holes to fit the screws. then I used wing nuts to adjust the clamping pressure. here's that 1000 word picture: