Subject: recurring rot in '69 wooden Lightning
Date: Fri, 10 Sep 1999
I recently found considerable rot in the floor plank (below
water line) in an area that I treated 5 yrs ago with git-rot. I
removed all loose rot with a knife and now have a hole 2.5 feet long
and 1 inch wide, pretty much where two planks join. I plan to cut the
hole uniformly and patch with a similar wood (tight fit) and screw the
patch into the ribs. One rib has about 1/2-inch of rot, all others are
in great shape. Should i coat the edges of the hole and the patch with
penetrating epoxy? I am concerned about differences in shrink-swell
between surrounding untreated wood and the epoxy treated wood. Will
this create future avenues for moisture retention?
Greg,
Yeah, that's the problem with GitRot -- it doesn't penetrate.
Treat everything with Penetrating Epoxy (CPES)-- the hole, the
ribs, and all new wood going in. Pay particular attention to edges and
end-grain areas...this is where the rot usually gets started. For the
rib that has the rotted area, treat the area first with the CPES, give
it a couple of days to dry, and then go back and apply a coating of
our Layup & Laminating Resin to the same area. This will follow
the CPES into the wood and give it the substance you need.
Don't forget butt-blocks, i.e., backer pieces of wood on the inside
of the hull where the ends of the new wood meet the end of the old
wood. And yes, treat everything with the CPES. It doesn't take much
and it will pay off big time down the road.
CPES is a very thin coating and there will be very little
expansion/contraction differences between the new CPES-treated wood
and the old wood. Moisture retention should not be an issue if that
worries you, especially if the edges and ends have been CPES-treated.
Come on back if you have additional questions.
Doc
Click
here for more info on C.P.E.S.
Subject: (Lightning re-build)
Date: Fri, 30 Apr 1999
Robert,
Wow! A complete surface restore. Good for you. I've sailed
Lightnings many times and they're fine boats and a pleasure to sail.
That's why they built so many of them and they lasted so long. I'll
give you my point-by-point comments item by item. Be prepared, though,
for a few mildly unpleasant surprises during the dismantling process.
There are always a few problems buried that the eye can't see. You
will need to replace all fastenings as you reassemble, as you suggest
below, and be prepared to doctor the wood a bit to get things fitting
tight. Okay, here goes....
Dear Dr. Rot:
I hope to use your products to restore an old (1950s?) Lightning
sailboat. It is 19 feet long; the beam is 6' 6". It seems to be
almost all mahogany. There is a little rot in one of the floor boards,
but it is not too bad (about 1/3 through). And there is a little rot
where the deck (1/4" plywood) meet the sides of the boat in a few
places.
Here is a preliminary plan and some questions. What do you
think?
1. Remove all wood trim, interior seats, and hardware including
centerboard.
Okay,
2. Strip the inside, and deck with a chemical stripper (What
type?) and sand to bare wood.
Okay. For stripper I've yet to find anything that worked any better
than the hardware store Jasco brand. It is not the most
*environmentally correct* stripper you can buy, but it works the best
and if you carefully gather the residue and dispose of it correctly
then it presents no problem for me.
3. Turn the boat over.
Okay.
4. Remove skeg which is bolted to the hull.
Okay. Watch the hull/skeg joint and treat thoroughly with CPES.
When replacing, use a polyurethane sealant such as 3-M 4200. The
polyurethane sealants adhere especially well to CPES treated wood.
5. Strip the outside of the hull and skeg with a chemical
stripper (Again, what type?) and sand to bare wood.
Jasco.
6. One coat of CPES including inside of CB trunk and skeg.
Okay.
7. Replace skeg and apply another coat of CPES to the hull, skeg,
and inside of CB trunk.
Perfect.
8. Apply your Resin and Filler to all cracks including where
deck meets the sides of the hull (some rot here).
Okay. If the rot runs deep and you have any questions about your
ability to get the filler into all openings, apply some of the L&L
Resin before the final go with the filler. The L&L Resin is VERY
slow-setting and will seep into places you might not be able to reach with
the filler.
9. Paint hull and skeg with epoxy paint (what kind? How many
coats?) Then UV polyurethane paint (How many coats?)
I wonder if you need the epoxy paint. I think I would use a
one-part polyurethane paint, such as Interlux Brightside One-Part
Polyurethane Enamel. If you want a glassy smooth finish, I would apply
the hi-build primer coat directly over the CPES-treated wood and then
sand down until it is as smooth as you want. After that 2 coats of the
poly enamel she should sparkle. Choose your paint (there are other
brands besides Interlux) and then religiously follow the instructions
on the can.
10. Turn boat over.
Right.
11. Two coats of CPES to deck. (Then what? It was covered with
canvas and painted. I'm not so interested in having the boat just like
original. I just want it to be strong and dry.)
The canvas gave traction for the feet and provided a buffer zone
between the paint and the wood. It's kind of a pain to put down, but
you might want to consider it. Your options are glass (even messier
than the canvas and expensive because of the resin required) or just
paint and some non-skid material. Lightnings don't get a whole lot of
deck traffic so you could get by with just the paint.
There are books out there (see WoodenBoat
Magazine) that go into
some detail on canvassing the decks. You might want to take a look.
12. One coat of CPES to the interior. Resin & Filler to the
small rot spot (Then varnish?).
Right on the resin and filler. You can varnish or not, as you
choose. CPES alone tones the wood about like a coat of clear varnish
and you might find that sufficient. Thick epoxies are subject to UV
degradation and MUST be varnish-covered. CPES soaks so far into the
wood that it's not so much of a problem, although you will have to re-CPES
every couple of years. Not a big deal since CPES splashes around
nicely.
13. Strip spars, interior seats (removed), and treat with
chemical stripper, sand to bare wood, one coat of CPES, then multiple
coats of varnish (How many? Interlux Spar Varnish?)
Interlux Spar Varnish is fine. Strip with the Jasco, sand, CPES,
and then put AT LEAST 5 coats of varnish over the CPES. Seven coats
would be even better, with a light sanding in between each coat. Don't
cheat on the varnish while you've got the mast down. It takes a bit
longer but the extra varnish gives much greater longevity.
14. Replace original bronze hardware (should I put epoxy in the
holes before I replace the screws? use new stainless steel screws?)
Before the epoxy in the holes, soak each hole with CPES (this
applies everywhere, by the way), let it cure (about 3-4 days) and test
a screw for solid grip. If the grip isn't what you think it should be
then a bit of epoxy is indicated. I would put the epoxy resin in
first, give it 24 hours to cure a bit, and then come back with the
screw. You can embed the screw in soft epoxy but you may never get it
out again, and you can't be sure that you are getting maximum draw on
the screw.
15. What should I do about the rudder (no rot)? I'd like it to
match the hull. I'll varnish the tiller after a coat of CPES just like
the spars.
Do the same thing to the rudder you're doing to the hull: strip it,
CPES-coat it, undercoat build it, and then paint with a couple coats
of poly paint.
Of course I'm not loaded with cash, but I really want to do this
right.
I understand. Fortunately you're not going to be using a whole lot
of anything. I can advise you an how much of what you might need once
you get started on the project.
Thanks for your help.
Rob F.
Hey, we're done! New boat! Sail the Mississippi like a champ!
Get back to me if you have more questions. Your project is a good
one and being undertaken on a good boat.
Doc
