Need some Shearwater help

Hi all, this is long... bear with me.

I'm currently building my girlfriend a Shearwater 14 hybrid from plans, and am running into many, many headaches thus far.  This is my second build, the first being a C16 from a kit back in '08/'09. 

Before I explain what's going on, let me just say that I've been playing around with the construction a bit to try to lighten the boat: 3mm Okoume vs. 4mm, no sheer-clamps, and a full layer of 4oz glass on the interior instead of the 9oz tape. During initial wire-up, I had a pretty distinct outward flare/S-curve in the port side panel (the right panel looking aft from the bow).  I also had the bow panels spread a few inches upon removing the temporary bow form (Made spreader sticks in place of bulkheads and forms at this point).  I tried to remedy the curve by clamping some temporary 1/4x1/4 sheerclamps/rubstrakes along the oustide of the hull at the sheer.  This seemed to work pretty well, everything looked fair, so I went ahead and filleted the seems.  Everything looked good... I went ahead and glassed the interior.  15 hours later I did my first fill coat of epoxy.  Yesterday, I moved the shell outside of my workspace to start work on shaping the chines.  It was then that I noticed the panel bulge/flare was back with a vengence.  I tried to play around with the shape a bit when I heard "crack" and realized that I had just fractured the glass (and mos likely the fillet) for about 3 feet along that chine. <sigh>

I simply don't know what went wrong with my hull shape.  Is it that this design MUST have sheerclamps in order to keep the shape with the complex curves (the plywood hull version doesn't utilize them...)??  I don't think the 3mm vs. 4mm would make a difference, but maybe I had a warp in the ply that was then compounded when all glued together?   Gotta be honest... I'm thinking the best way to go right now would be to take a saw to it, buy the wood parts kit at this point and call it a day.  I'm a solid woodworker with a good skill set, but this issue just has me scratching my head.

Thoughts?  Advice?

Thanks in advance,

~Chris


8 replies:

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RE: Need some Shearwater help

áááYes, I think the sheer clamp is going to be very important to defining the shape. I have only made the sassafras and skerry but the gunwale rails really help define the sheer strake curve.

RE: Need some Shearwater help

How were you going to attach the deck without shear clamps? 

Did you remove the temporary shear clamps too early?   

Doesn't 1/4" x 1/4" shear clamp/ shear strake seem a little light?

Did I read that the hull had no bulkheads or forms for that purpose?  So what resists warp and the hull taking on a "trapezoidial section", wracking?

RE: Need some Shearwater help

   I looked at the constitution gallery for a WD12 hybrid because the Shearwater didn't have one and it showed many many forms used to define the shape and provide a platform for building the hybrid deck. Don't know if you're at that point yet but you may want to hold off on the Viking funeral (taking a saw to it).

I built the standard WD12 and joining the deck to the hull made a big difference in stiffness. Where you went with 3mm. for the hull panels its probably more so.

RE: Need some Shearwater help

Not so fast with the saw. Glass makes a mushy crunching sound when it fails, the fillet & wood make cracks, so your glass should be fine.

On my WD12, which does not use sheer clamps, the hull was all over the place until it was attached to the deck, at which point it took on a nice fair shape. So if your deck is not on yet, don't worry.

If it was my boat, I'd put back all the temporary crutches to fix its shape, find where the crack came from and fix it by patching it with epoxy/woodflour putty and let it cure for at least 48 hours before touching it. If the glass over the area looks as if it's delaminated, I'd remove it locally and laminate a patch over it at the same time I was touching up the fillet.

Then I'd leave all the temporary stuff on until the deck was wired to the hull. Once the deck is there to support the hull shape the crutches can come off.

Good luck,

Laszlo

 

RE: Need some Shearwater help

   I stand corrected. I checked the Shearwater 14 Hybrid page and it showed the plethora (don't get to use that much) of temporary forms used in the hybrid construction. 

RE: Need some Shearwater help

   Thanks all!  

Laszlo, I was hoping you'd chime in here...  I'd say your thoughts on putting the forms back in are sound.  Regarding the glass/fillet crack: it definitely made an audible crack/crunch sound, and there is a thin white line along the seam (where the glass broke).  Are you thinking grinding out the fillet and then refilleting and reglassing with 9oz tape is the way to go?  I just want to make sure I can repair the fillet so that it is structurally as sound as before.  

 

Based on the shift that took place, I'm thinking about installing the deck forms prior to flipping the boat to shape and glass the exterior.  This will keep the shape off the hull from shifting around even further.  That said, I'm trying to think about how best to attach said forms so that wire or screws won't penetrate the exterior hull (and therefore disrupt the continuity of the glass cloth).  Epoxy tab them in and then just cut them out when the time comes??  Hot glue??  

 

Grumpy, most kayaks do not require sheerclamps to attach the deck: you simply tape both the interior and exterior of the hull/deck joint.  The hull was formed with bulkheads and forms in place, but then removed so that I could glass the interior (I did this with one continuous piece of 4oz rather than only in the cockpit).  This is a common method among other designs (including some that CLC sells...  

RE: Need some Shearwater help

  "......you simply tape both the interior and exterior of the hull/deck joint. .........."

.

Y'all got longer arms than me.

.

The C-17 uses shear clamps and boat nails to secure the deck during cure.  No tape on the inside.  

RE: Need some Shearwater help

Sail114,

The white line indicates delamination, you definitely want to grind/peel that up and patch it. You can use the 9 oz tape if you want, or you can just make a patch out of leftovers from glassing the interior. Clean off down to bare wood for about 2 inches around the crack and lay up a patch that overlaps the glassed part for about 2 inches on all sides ( 4 inch wide patch). If you feather it in carefully, it'll be pretty much invisible, even varnished.

I wouldn't put the exterior glass on until the deck is attached. The glass will not stabilize the hull, but it will make it harder to flex when adjusting the shape to match the hull.

Grumpy,

Our arms are probably close to the same size, I just have my chimps to do it for me.

Seriously, tools on a stick take care of it just fine. It doesn't even have to be a smooth stick.

Laszlo

 

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