Re: Protecting your botto

Posted by LeeG on Oct 29, 2004

epoxied 6oz is mighty tough,,the sounds of scraping will be worse than the actual damage. That said you will have 100X more wear at the stern and bow in a narrow 3/8"x12" strip. Put down 1/2 oval 3/8" brass strips like Terry mentions. It doesn't do much good to put stuff everywhere if the wear is down to the wood in one place. After that epoxied laminates will always be tougher than various thin coatings. Sure you can use two part paints,,that's tougher than varnish or one part paints. But there's no way 1/10mm of paint will be as tough as 1mm of epoxied glass or .5mm of two more fill coats of epoxy. Graphite looks cool and is ablative,,but if you are talking about resistance to scraping IMPACTS then there's no free lunch,,you need a thicker exterior laminate that's tough. You could put down a relatively soft ablative epoxy/graphite coat that will allow the kayak to slide over stuff or a hard ablative coat using epoxy/cabosil that will be harder. But what if you used the weight of all that thicker fill coats/paint and layed down another layer of 4oz glass? Speaking from experience if you REALLY want resistance of the hull to scraping impacts that can wear through the glass and into the wood make a thicker bottom using the toughest materials. Think of it this way,,6oz glass with three fill coats and the last one a thick layer of graphite/epoxy. Get a hammer and drag the claw side along the bottom starting with an impact. Then go to another hull that has 6oz glass+4ozglass and three fill coats and do the same.

The claw will dig right through the graphite epoxy before sliding,,it's the damage caused when the 6oz glass is breached that you'll be repairing,,not the scrape.

If you wanted to spend as much effort masking/applying and sanding black dust but have a much more durable bottom get three yards of 4oz s-glass for about $45, cut it diagonally and apply it. You'll still be able to have a varnishable surface. My take on it is to make the laminate strong enough for the purpose and lay down thick fill coats. The only serious objection I'd have to graphite coatings is for kayaks stored/transported in hot weather where it can be a solar collector. I don't have the data but I think Epoxy starts softening around 170degrees. Aside from that everyone knows what it's like to put your hand on a black car sitting in 100degree sun. The epoxies we're using aren't the kinds used in aerospace devices so I'm not sure what the consequences of repeated heating could be.

In Response to: Protecting your bottom by Michael Delchambre on Oct 28, 2004