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Spindrift 12 setback: plywood fracture.


Ambler

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Tom - can you give a description of how you use an outside batten? I haven't clued in to the concept.

Attached is a close-up of my okume showing the ply thicknesses. Increasingly I think the thin face plies must have been part of my problem.

Michel, I looked at Noah's (Toronto) website and thought the photos of their plywood didn't look all that much better from the standpoint of ply uniformity - but the pictures are a bit small to be sure.

Alexander.

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Alexander, The plywood does not look too bad to me. The outer ply is almost 1 mil and we often deal with stuff thinner than that.

The batten I would use is about 1/2 " thick by 1 1/4" width (all approximate) and maybe 1/3 the length of the boat so that the bending is supported over a large area. I place the batten on the outside about 1" below the chine to give ample room to install the wire stitches. run screws from the inside through small pieces of scrap plywood to minimize scaring the panel. If there is a lot of panel edge curvature, you may need to decrease the width of the batten.

I also like the thin epoxy coat on the outside like I mentioned above.

Good luck.

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I don't know about the okoume but with domestic fir ply the variation in thickness is due to finish sanding. I saw one sheet of 1/4" fir that had been sanded all the way through in one place. I guess the guy running the sander dozed off or something :-)

I am lucky to live within driving distance of a supplier so I can inspect each sheet before I buy it.

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In Ambler's photo of the edge of his plywood, there is an obvious difference in thickness in the middle layers.

I inspected the 6mm Okoume BS-1088 plywood that I received from Harbor Sales. The BS-1088 code is printed on the plywood faces. The three middle layers are all the same thickness. Also, the outer layers are almost the same thickness as the middle layers with only a small reduction due to sanding.

I have been very pleased with the working characteristics of my plywood. I did take Graham's suggestion and temporarily reinforced the butterfly joint before I folded the sides into place.

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  • 3 weeks later...

Garry, thanks for your comment about ply thicknesses. Like you I think my face & center plies are significantly thinner than they should be.

You say your wood had BS 1088 stamped on it. Did it also have the BS official "Kitemark?" (I'll try to attach a picture of that in case it's not familiar.) I don't know whether (m)any manufacturers outside UK are really BSI certified or accredited or whatever the terminology is.

Browsing the net I've come to the conclusion that some plywood makers call their product BS 1088 whether it's literally produced to the same standards or not. I found at least one who stated his 1088 stuff was made according to the BS standard "interpreted." Hmmm.

I suspect there's material out there of highly variable quality, whose makers, distributors or retailers are calling it, and maybe stamping it, BS 1088 if it comes more-or-less close (or maybe not even that.) On my own wood there was only a handwritten sticky label. Obviously I should have examined the stuff more closely, but I'd had such a hard time finding it locally, I was too pleased to stop & think. Caveat emptor indeed!

Alexander.

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From what I've gleaned on the www, yes - Shelman's plywood is top grade. I think I read they even have a brand that is Lloyd's certified. But it seems some folks who call - and probably stamp - their product "1088" are selling stuff that's not literally up to that standard. One dealer's write-up described his 1088 plywood as being made to an "interpretation" of BS 1088.

Sort of like "Based on a true story!"

Alexander.

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I'm fairly certain that the Brits dropped support for the BS1088 & others several years ago. Therefore, no plywood now being produced is ever actually verified by the keepers of the standard. Of course, the standard is still there and some plywood makers still claim to adhere to it. Hopefully they are honest about the claim, but it is a matter of trust or experience with a given manufacturer. :(

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