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Repair Advice? SN-10 Nesting Bulkhead


mjshp

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Finished Wisp, a SN10 this spring.  Sailed in races, took it to the mother ship...all was wonderous at 59N until I noticed the cracks at the nesting bulkhead and the gunwale. It's happening on all 4, so something is amiss--see the photo below.

 

The crack's size is exaggerated in the photo--to show the area if concern I am pressing inward in on the mating surface of the bulkhead, without the applied pressure, the crack is just a hairline.

 

Thoughts on how best to repair this?

 

Thanks.

The Crack

post-2157-0-43924300-1393201102_thumb.jpg

 

Launch Day

post-2157-0-80435000-1393201095_thumb.jpg

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Looks to me like your gunwales are in the process of delaminating. Mine did something similar, but that was while I was still in the process of building the boat, so it was easier to repair. I determined the culprit to be excessive clamping pressure, which combined with dry wood soaking up the juice, leaving a thin, glue starved joint. Stress from use was probably the trigger that got you where you are.

 

If that is the case, not sure what repair is possible, other than prying it off, cleaning up the surfaces and putting it back on. Short term, you might try prying the edge open a bit, forcing some epoxy in, and allowing the spring back to be your clamp or use a small stainless deck screw from the inside and leave it in. But that only affects the ends. If the middle is doing the same thing, you would only be buying time until you get to to the whole job.

 

BTW, this was the issue that got me thinking about putting something into my thickened epoxy mix to prevent squeeze out from excessive clamping pressure. That led me to using the finely ground walnut shell, which acts both as a spacer and grit to prevent the two pieces being clamped from sliding around.

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Use a wooden wedge to pry open the gap and a syringe to inject some goo. No clamping pressure, just let the crack close back up after you inject and pull the wedge. Farm and feed stores will have veterinary syringes for cheap. I use these for spot repairs frequently and since they're plastic, you can clean them out easily, for reuse.

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Use a wooden wedge to pry open the gap and a syringe to inject some goo. No clamping pressure, just let the crack close back up after you inject and pull the wedge. Farm and feed stores will have veterinary syringes for cheap. I use these for spot repairs frequently and since they're plastic, you can clean them out easily, for reuse.

Yeah, maybe clamp the gunwale a foot away from the bulkhead to make sure you don't open the split any more than it already is.  If you can't find syringes locally you can get them through Jamestown Distributors. 

http://www.jamestowndistributors.com/userportal/show_product.do?pid=2096&familyName=Epoxy+Syringes

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It is hard to tell from here what the real cause of the cracks is. It could be the glue, mix ratio, glue technique or stress. The fact that they are in the break in the gunwales, stress is certainly a contributor.  I find that the easiest way to repair a a crack like yours is to run a saw cut through the crack. This will clear out the old glue, and get rid of any crud that will effect the new bond. Cut a thin sliver of wood to fill the saw kerf with just enough room for epoxy. This should get you back to original strength.

 

The gunwales contribute a lot of strength to an open boat and cutting them in half does allow the boat to rack more which stresses the gunwale ends. I assume that you glassed in the bulkheads to the schedule specified. I would add some mechanical fasteners such as a small through bolt through the gunwale and the heavier glass layup opposite.

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UPDATE:

 

Graham, yes I followed the inner corner tape schedule as specified in the plans. Upon taking a closer look, it's not the gunwale separating from the hull, rather the nesting bulkhead--on the nesting side--separating from the hull.  The gunwale and the inner corner tape schedule are holding things together.

 

Given this new information does the repair approach you outlined stay the the same?

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