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Doctor Rot

Subject: Recurring Rot in '69 Wood Lightning
Date: Friday, 10 September 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?


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.


Subject: Lightning Rebuild
Date: Friday, 30 April 1999


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.


  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.


  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.


  6. One coat of CPES including inside of CB trunk and skeg.


  7. Replace skeg and apply another coat of CPES to the hull, skeg, and inside of CB trunk.


  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.


  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 Wooden Boat 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.


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