Is there a rule (scantling) for replacing plywood with strip-plank?
That is, if plywood of X millimeters is specified for a hull, then
what should the thickness of the strip planks be?

I do have a vague idea of doubling; in other words, using 12mm strips
instead of 6mm plywood, say. But I can't think of where I got this from,
and, indeed, it seems to add a lot of weight.


Thank you,
Sakari Aaltonen

Sakari says:

I do have a vague idea of doubling; in other words, using 12mm strips
instead of 6mm plywood, say.

You need to carefully assess how much of the plywood is providing strength in
the 90degree direction, and apply a similarly-strong layer of strips in that
direction, as well as the obvious similarly-thick strips in the zero-degree
direction to replace the outer lamina of the plywood.

Steve
Stephen C. Baker - Yacht Designer
http://members.aol.com/SailDesign/pr...cbweb/home.htm

you should be able to do your own stress testing on sample pieces if you
want. I've read that in one direction plywood is only 60% as strong as
wood (hardwood?, softwood? same wood?, I don't remember), in the other
direction its stronger.

to test place a length of material between two blocks and pile weights
on the middle until it cracks or breaks. do it three times to make sure
its consistent and average the weights. moisture content will have some
effect.

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On Sat, 10 Jan 2004 10:49:47 +0200 (EET), (Sakari
Aaltonen) vaguely proposed a theory
.......and in reply I say!:

Is there a rule (scantling) for replacing plywood with strip-plank?
That is, if plywood of X millimeters is specified for a hull, then
what should the thickness of the strip planks be?

I do have a vague idea of doubling; in other words, using 12mm strips
instead of 6mm plywood, say. But I can't think of where I got this from,
and, indeed, it seems to add a lot of weight.

Unfair question. Sheathed or not? Both sides or only outside? If not
sheathed, how are you going to join the planks?

Ply is very strong on its own, and if I was strip planking without
sheathing, doubling the thickness would be a minimum.

But if you sheath both sides with epoxy/glass, the whole situation
changes. The ply/strip just about only becomes a way to hold two
tensile-strong layers apart. Ply would still be stronger if damage was
done to the skin(s).

If ply of Xmm is specified, talk to the designer about how many Xmms
they would ask for to replace it.
************************************************** ** sorry
remove ns from my header address to reply via email

I was frightened by the idea of a conspiracy that was
causing it all.
But then I was terrified that maybe there was no plan,
really. Is this unpleasant mess all a mistake?

In article ,
Old Nick wrote:

I do have a vague idea of doubling; in other words, using 12mm strips
instead of 6mm plywood, say. But I can't think of where I got this from,
and, indeed, it seems to add a lot of weight.

Unfair question. Sheathed or not? Both sides or only outside? If not
sheathed, how are you going to join the planks?

The current idea is to use polyurethane glue to join the strips.
No sheathing, probably.


Ply is very strong on its own, and if I was strip planking without
sheathing, doubling the thickness would be a minimum.

But if you sheath both sides with epoxy/glass, the whole situation
changes. The ply/strip just about only becomes a way to hold two
tensile-strong layers apart. Ply would still be stronger if damage was
done to the skin(s).

I often wonder about the strength vs. thickness vs. weight. Birch
plywood, say, is about 50% heavier than okume - is it also 50% stronger?
If a plan specifies 6mm plywood, what species is meant?


If ply of Xmm is specified, talk to the designer about how many Xmms
they would ask for to replace it.

Not all designers are alive...


Sakari Aaltonen