My 1975 SeaCraft 25' Seafari rebuild thread

[Blue_Heron]

Originally Posted by Bushwacker

A bracket will evenly distribute motor loads across the entire transom, so you'll actually have lower concentrated loads and stresses on your rig than you'd have on a conventional outboard or outdrive transom mount!

... (When you bend an I-beam, the compressive and tensile stresses are directly proportional to the distance from the neutral axis, which is at the center of a symmetrical part, so there is NO bending stress at the neutral axis. A cored panel is similar to an I-beam, so the max bending stresses are at the outer surface. This is why cored panels can be so stiff and strong with relatively weak and lightweight core materials like foam. As long as you use epoxy or vinylester resin for good bond strength, that transom will be stiff as a brick!

Originally Posted by hermco

Is why you want as close to an equal laminate on both sides of the core as possible to achieve the "I" beam.

Originally Posted by FishStretcher

Decks with sandwich core construction tend to have unequal skin thicknesses. This isn't contradictory, rather that the minimum thickness required for stiffness isn't enough for when you drop the anchor on the deck. So you add more laminate there. But it isn't needed for the bending stiffness.

This is all good discussion about the fundamentals of boat structure. It got me thinking that maybe we should start a thread on the basic structural concepts of cored laminates and other aspects of boat construction. If it proves useful, it could be made a sticky. I've bookmarked some good links, maybe I'll start something when I have a chance to pull it together.

Dave