This is what a bad scarf looks like. That lip is about 1/8" tall and the gap extends 1 1/4" into the scarf. My first scarfs had a small gap, but this was unacceptable. I am unwilling to put myself into a dry boat that has only 2/3 of a 1/4" plywood bottom scarf. Too much potential for wetness. Actually, I considered just packing the gap with epoxy and forgetting about it. The outside gets another coat of epoxy and fiberglass and the inside gets at least one more coat of epoxy. But the still, small voice inside said that I should do it the Right Way. So I measured the length of plywood that I would need and lucky for me I could still make one more scarfing attempt! I cut out the bad scarf and am in the process of re-sanding the angle so I can try again. I am not sure what I screwed up last time. It seams like there are two possibilities, the alignment and the squeeze. The alignment means getting the two angles matched up correctly. If they were too on top of each other it would cause the lifting of the tips. But the rest of the face would match up and there wouldn't be a void, provided there was sufficient pressure. The squeeze refers to the pressure applied to the joint during glue time. I think you can compensate for some mis-alignment with enough pressure to smash it all together. The problem lies in too much squeeze, which would push all the glue out, making all my hard work for naught. Since the lifted tip runs the whole length (almost) of the scarf, I assume that pressure was approximately even but maybe just not enough. It's worth mentioning that my sanded angles were not perfect, but not that bad either. Like I mentioned in my last post, I didn't use two mixes of epoxy. I have learned that epoxy covers all mistakes, and in this case the extra might have filled in the gap I left. Since my angles are much closer to perfect this time, I will have to load up the epoxy, crank down the clamps and triple check the alignment. A dry fit might be in order too.
Thursday, October 29, 2009
Bad scarf
This is what a bad scarf looks like. That lip is about 1/8" tall and the gap extends 1 1/4" into the scarf. My first scarfs had a small gap, but this was unacceptable. I am unwilling to put myself into a dry boat that has only 2/3 of a 1/4" plywood bottom scarf. Too much potential for wetness. Actually, I considered just packing the gap with epoxy and forgetting about it. The outside gets another coat of epoxy and fiberglass and the inside gets at least one more coat of epoxy. But the still, small voice inside said that I should do it the Right Way. So I measured the length of plywood that I would need and lucky for me I could still make one more scarfing attempt! I cut out the bad scarf and am in the process of re-sanding the angle so I can try again. I am not sure what I screwed up last time. It seams like there are two possibilities, the alignment and the squeeze. The alignment means getting the two angles matched up correctly. If they were too on top of each other it would cause the lifting of the tips. But the rest of the face would match up and there wouldn't be a void, provided there was sufficient pressure. The squeeze refers to the pressure applied to the joint during glue time. I think you can compensate for some mis-alignment with enough pressure to smash it all together. The problem lies in too much squeeze, which would push all the glue out, making all my hard work for naught. Since the lifted tip runs the whole length (almost) of the scarf, I assume that pressure was approximately even but maybe just not enough. It's worth mentioning that my sanded angles were not perfect, but not that bad either. Like I mentioned in my last post, I didn't use two mixes of epoxy. I have learned that epoxy covers all mistakes, and in this case the extra might have filled in the gap I left. Since my angles are much closer to perfect this time, I will have to load up the epoxy, crank down the clamps and triple check the alignment. A dry fit might be in order too.
Subscribe to:
Post Comments (Atom)
No comments:
Post a Comment