Plywood/hull attachment

[gareth harris]

I am cutting a lot of 0.5" (mostly) plywood which is going to be glassed to the hull.
Is there any concern with creating pressure points where the wood contacts the hull? Should anything be placed between the two to spread the load?
There does not seem to be much there originally, except that often the wood hardly touches the hull, so I wonder if the bonding glass is meant to act as a shock absorber.

Gareth
Freyja E35 #241 1972

 

[Geoff Johnson]

I think you are on the right track:

http://www.yachtsurvey.com/HullFailP2.htm

 

[gareth harris]

That is exactly what I was asking. However, that article said that the plywood should be lined with a 'soft material'.

Can anyone recommend a soft material for the purpose?

Gareth
Freyja E35 #241 1972

 

[Geoff Johnson]

I remember reading somewhere (maybe one of Casey's book) that you can use styrofoam or some equivalent that is more flexible. I don't think it is meant to have any structural purpose, just hold the hard edge of the plywood away from the hull. The one time I did it (and I was just making things up as I went along) I recall that I used 1/2 inch closed cell foam from a backpacking mattress. However, that boat was an O'Day and anything was an improvement over the original construction. I assume you are using epoxy. If you are using polyester, you obviously have to find something that will not dissolve.

 

[John Bouchard]

Elsewhere on this site, regarding bulkhead replacement, I seem to recall some instructions about inserting some type of foam or cushion between the bulkhead edge and the hull. Do a search for chainplate problems or wet rot in the bulkheads.

But, when I replaced the bulkheads in my E32, the friend who helped/guided me (he has worked with builders of America's Cup boats, evidently, etc. here in New England) did it this way: after installing the tabbing/fiberglass on one side of the bulkhead (fore or aft), he mixed colloidal filler with resin, and filled in the space betwen the bulkhead edge and the hull, smoothing it with a curved piece of wood. When it had nearly set, he applied the fiberglass tabbing over the filler and onto the bulkhead and hull.

I've sailed her all last season (not a lot of experience yet!), and everything seemed quite solid with no creaks or groans.

On the other hand, he always said that there's nothing like the smell of curing resin in the morning... he does seem to like those fumes....

For what it's worth! Good luck with it!

John B.