Tuesday, June 11, 2013

Spring has Sprung

Well the worst of the cold weather passed with the end of March. April was a busy month, and a good bit of May was spent recovering from April. I did get to do some cleaning up. It's surprising what just a couple months of "I'll just put this here for now," will do. I have things looking much more organized now, but I couldn't get everything cleaned up before the urge to Do Something overcame me.

Experimenting with fiberglass cloth over the plank lands.

I'd been thinking a lot about how to finish the hull, and had decided to put a fiberglass skin over the plywood, but I wasn't quite sure how I wanted to do it. Other builders have put fiberglass and epoxy on each plank separately. This protects the faces of the plywood, but less protection to the more delicate edges. It allows the builder to keep the traditional "clinker" look where the planks overlap, but does not add any additional strength to that joint.

My main reason for using fiberglass is to protect the edges, so I've been thinking about using a continuous layer of fiberglass cloth to cover the planking. I'm also interested in the additional strength this will add. The epoxy glued overlaps are, in principle, plenty strong. In all my destructive tests, the plywood failed before the epoxy bond. But I know I have a few places where there is a gap between the planks that the epoxy didn't fill completely, though. The angle of my plank land must have been off a little bit. I've gone back to fill these in, but, as I'm planning to use the fiberglass anyway, a little extra piece of mind can't hurt.

I don't want to round over the edges of the planking more than I need to, so I made up a test piece from some scrap.

My System Three squeegee makes an appropriately sized fillet.

I rounded the corner with either a 1/8 inch radius or 3/16, and made a fillet with either my System Three squeegee or a tongue depressor. I'm using the lightest weight cloth I could find, 4oz., so it would conform more easily to the curves. The 3/16 radius with the squeegee worked all right.  It took a little massaging to get the cloth to adhere firmly, but in the end it did.

The cloth clings nicely to both the inside and outside curves.
The fillet left by the tongue depressor was just too tight. I couldn't get the cloth to adhere. In some places it stuck, but in others it pulled away. You can see the light colored patch in front of the stick. There is a bubble of air underneath the fiberglass cloth.
The radius left by the tongue depressor is too tight!

The cloth did actually adhere to the tighter 1/8 inch roundover, but not without a lot of careful work. The thought of trying to get a 20' long piece of cloth to cling for the full length is not appealing. Indeed, even with the more gentle 3/16 radius, it may be a chore to get everything right. This is compounded by the fact that I plan to use one continuous piece of cloth to cover each side of the boat - all six seams. (Well, except for a lens shaped section near the keel that I'll have to go back and cover after the sides are cured.) This will be two long days of epoxy work.