How flexible is epoxy

[newey]

As the heading says "How flexible is epoxy?"

The reason I ask is help decide whether I apply epoxy to the flat panels (and sand) before I stitch the boat up. I have read that it can make panels more difficult to bend, but the fact they still do bend implies the epoxy bends also. Is there a point where it doesn't bend anymore - then what?

I can see definite advantages to being able to 'prepare' the panels first. Its seems some people do and some don't.

And another thing, I read the term wet on wet with regards to applying epoxy/glass. Does it make much difference strength wise if you apply epoxy or glass to a dry epoxied surface? I imagine wet on wet would create a greater bond between epoxy layers?

I will be building Ross Lillistone's Flint, so perhaps Ross, if you read this, you can comment as to whether flexing/twisting the bottom panels will still be possible once they are epoxied?

Cheers,

Ken

[PAR]

Ken, good epoxy procedures will produce reliable results, that are stronger then the wood fibers it's attached to, regardless of the type of bond (mechanical or chemical). So, though it's desirable to have wet on wet (chemical) bonds, often it's not practical and mechanical bonds must be employed. Again, if you use good techniques and follow procedures, you'll have fine bonds and well stuck goo.

Epoxy has a fairly high physical elongation property, though this does differ from brand to brand. For the most part, pre-coating plywood serves only one real purpose, which is a good one and that is to coat areas that other wise may be difficult or imposable to do well once the boat is assembled.

As far as making a panel stiffer as it's bent into position, well this may have some measurable merit, but, not enough to cause concern. In other words, a 3 mm panel (for example) being bent with no pre-coat, may require slightly less force, but the coated panel will probably bend further before surface damage occurs (raised grain, checking, etc.) because the epoxy is holding things in place while the plywood is being tortured into position.

Unless you're building a weird design with "quick" curves, you will not be bending plywood that severely, so don't be as concerned. Some of my designs will test the limits of plywood bending, but if you're building a Mik Storer design, you'll have no issues.

[Boatmik]

Howdy Ken,

Contact Ross directly. He drops in here sometimes ... but give him a call or a direct email. It is probably OK, but nobody knows the boat like the designer does!

MIK

[MiLKey]

I JUST finished stitching up my eureka today and glass taped the inside seams. I precoated the inside of the panels, and when i was lifting them and moving them around they still had alot of flex, and during the stitching i didnt have any problems. :2tsup:
Mike