RE: [bolger] Options for ply thickness for similar sharpie construction on similar moderate LOA?

At least a couple of Micros have been built with all 3/8s. In general, small boats are stressed by point impact (hitting something or crew weight while standing), sustained or rhythmic force (waves leading to oil canning or vibration from trailing), and twisting from the force if ails and boards. Plywood is fairly heavy and increasing the thickness by 50 to 100% will increase the weight of the hull by the same amount while increasing the strength and stiffness. So everything is a compromise. If you are inclined to beef up scantlings, conventional wisdom is to increase the thickness of the bottom which will increase strength and stiffness while adding “ballast” to the bottom of the boat. PCB often did this.

JohnT

From:bolger@yahoogroups.com [mailto: bolger@yahoogroups.com ]On Behalf Ofc.ruzer@...
Sent:Monday, December 23, 2013 4:36 AM
To:bolger@yahoogroups.com
Subject:[bolger] Options for ply thickness for similar sharpie construction on similar moderate LOA?

Otter ll pic here:

http://groups.yahoo.com/neo/groups/bolger/photos/albums/925048110

Otter: 19'6", sides 1/4", bottom 3/8", and ballasted;

Otter ll: 19'6", sides 1/4", bottom 3/8" doubled, and unballasted (but for bottom?);

Birdwatcher: 23'6", sides 1/4", bottom 1/2" doubled, and bottom is ballast;

Micro: 15'4", all 1/4", and ballasted;

Long Micro: 19'6", all of either 3/8" or 1/2", and ballasted;

AS19: 19'6", spec'd all at 1/2" and suggested a better sailer when of 1/4", and ballasted;

Anhinga: 23'6", all spec'd at 1/4" and no more than 3/8", bottom doubled, and ballasted;

Wish ll: 20', all 1/2", bottom doubled, and ballasted.

All quite similar construction. Similar bulkhead, timber stiffener spacings...

So what's the take-out here? Is it use within reason what you want/got? How about 1/4" sides, 3/8" bottom for Wish ll then?

NB. Teal was certainly 3/8" only because at the time that was what was best available for whomever, wherever...