Sunday, January 22, 2017

The Slow Saga of Zip Frame #4 — part four

Sometimes, the damnedest things go wrong.

I had decided to attach one of the side ribs to the floor beam, using thickened epoxy and screws. Seems simple enough, right?

Epoxy and screw the rib to the gusset: Done. 

Epoxy and screw the rib and gusset to the floor beam: Done. 

Drive one two-inch screw all the way through the lap joint. Well now, that's where we developed a problem. The screw actually pushed the rib away from the gusset some, rather than pull the whole thing together.

In hindsight, the simple thing to do would have been to remove the screw, and re-drive it. However, that's not what I did. I put nine clamps on the joint, and drove the screw as tightly as possible... until it broke.

No problem, I thought. I had more than enough clamps on there to do the trick. Or, so I thought.

You'd think this would be enough clamps. It wasn't.

Once the epoxy cured, and I removed all the clamps, however... I realized that reality was a bit different from my expectations. 


that's a big enough gap, you can see daylight through it.

The reality was that there was a substantial gap between the frame rib and the gusset. This is, of course, unacceptable. It must be fixed.

Fortunately, it looks like the gap can be pushed together, if I apply enough clamp pressure in the right place. So, my plan as of now is to fill the gap with more epoxy, and clamp it together forcefully.

Fortunately, enough pressure from the right kind of clamp will close the gap.

All this helped me to realize the weakness in my approach to the lap joint: Using only one screw through all the parts. I won't repeat that mistake on the other side. In addition to the one 2" #10 screw that's already in place, I will add one or two additional 1-3/4" screws that I bought recently. 

Here's part of the problem: only one 2" screw through the lap joint. I'll add one or two screws to this side, to avoid the same mistake. The best thing may have actually been to use carriage bolts. I used what I had, however.

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