Key Largo Build in Charleston

A forum for contacting other builders of Ken Hankinson designs. These designs are now a part of the Glen-L family.

Moderators: Bill Edmundson, billy c

TomB
Posts: 544
Joined: Wed Jan 18, 2017 4:07 pm
Location: Holland, MI

Re: Key Largo Build in Charleston

Post by TomB » Sat Jun 08, 2019 7:34 am

Sometime during the summer I get to say "its not the heat, its the humidity". If we go back in time before plywood when boats were made with planks -

The bottoms where planked close, the cracks sealed with oakum and the builder's secret formula "red lead". They leaked. To solve the problem the boats were lowered into the water and allowed to soak and the planks swelled across their width to form a tight seal between planks, solving the leak problem.

Topsides leaked too. Put the planks together and the wood shrinks when the humidity is low causing leaking gaps. Put the dry planks tight and humidity pushes them apart causing "duck puckers" and eventual fastener failures. The solution was wider joints and caulk.

If you use plywood, the wood grain in each layer is turned to reduce the effects of expansion and contraction. So we wind up with a stable layer, top and bottom of the boat, no more soaking, no topside caulk. Now add a veneer layer, full adhered to the stable substrate (really no different than making a thicker layer of plywood). While a 1/4" veneer might want to move, it can't move at the plywood interface because the plywood won't let it. So how much can the top face of a 2" wide 1/4" thick board expand/contract? Not much. Butt the top planks together, caulk, epoxy caulk, paint stripes on plywood, all good.

There is a gap in my argument at the coverboard topside interface. Since the coverboard is rabbeted and overlaps the plywood layer all the expansion happens away from the topside seam, so that joint can be tight too. Here's a little eye candy to illustrate my point-
Madeleine.jpg
my two cents,

Tom

mickfly
Posts: 69
Joined: Mon Jan 29, 2018 9:19 am

Re: Key Largo Build in Charleston

Post by mickfly » Sat Jun 08, 2019 12:52 pm

Thanks all. The caulking with UV resistance sounds like a winner. Charleston is extremely humid...so maybe an issue with epoxy "caulk". I will have a 1/4 plywood base...and ~5/16-3/8 planks.

Post Reply

Return to “Hankinson designs”