A Photo & Discussion Forum for Wharram Design Enthusiasts
my t-26 has rot on the outwale. It looks like the fiberglass from the deck cracked at the corner and allowed water to infiltrate. My plan is to remove the rotten sections and reglass.
Looking at the build book it appears that the glass from the deck drapes over the gunwale and the glass from the hull meets the bottom of the gunwale (see photo below). Do I cut the glass back to the deck replace the gunwale and then use a 6 or 8” strip of glass overlapping the deck and hull glass? Do I grind a taper and use multiple strips of differing widths over the gunwale To affect a structural repair? Is the gunwale important in terms of how the deck fastens to the hull? There does not appear to be any hull rot...
Here also is a scaffolding I built from 2x6 and ply for lifting the hulls off the trailer. It goes together with carriage bolts and I use a chain fall attached to a heavy duty strap around the hull and above, to the scaffolding to lift the hulls. I then bought a garden cart rated for 1300 pounds, with plywood supports bolted on to take a hull. I can wheel each hull individually around the yard or what have you.
I have had to deal with rot in a fir stringer in a cockpit of my 31' where there are many water traps. ( it was small enough to repair with epoxy). With rot in painted wood there is always more of it than it looks. The paint/epoxy/glass forms a more or less (not 100%) impermeable covering but if the water gets underneath it the water stays in and the rot forms hidden to the eye. You only need a small crack for it to get in, so I always have some Milliput epoxy filler around to work into an expansion crack anywhere when I see it. With the greater extremes in temperature we are getting in the UK, with wetter winters also, it's more of a problem (expansion/shrinking: this happens whatever the integrity of the epoxy/glass coating and paint finish, wood can burst it).
It looks as though your outwhale fibreglass covering has worn down a bit as well as the cracking. Maybe moisture got into the wood because of the wear, expanded, then cracked the thin covering. When I built my boat I made an epoxy high strength fillet all around each hull below the outwhale/gunwhale stringer where the fibreglass cloth ends to join the fibreglass covering on the upper hullside below. I don't know if Wharrams are including this on their plans now, if not they should. There can not easily be any rot coming from below the stringer with this set-up.
So I would carefully pare back the wood with hand tools only and explore the area, taking away timber only when you have worked out your method for replacing it. Sometimes I will work a taper in while I am cutting (thin Japanese saws are ideal for work like this), sometimes undercutting so the taper traps the repair piece against the timber behind. If the rot is extensive then you can repair on the inside to any sound timber before removing a lot of what is defective from the outside. This also preserves the integrity of that part of the hull if you have to take much rotten timber away on the outside. Epoxy makes this relatively easy on the inside, but you will have to put it on a sound substrate.
Don't use your best chisels though, as the ply is nailed to the stringers with annular ring nails and you are bound to hit one somewhere.