Plank dutchmans?

[tsunami]

I am restoring my 36 ft Atkin ketch ( Sunny ).I have some areas of surface rot(up to 3/4 in on 1 and 1/2 in planks above the waterline around chainplates two different spots and what I figure 4 small dutchman with a seam between The planks.I thought bedding them with 5200 and screws through the bottom plank.(typical carvel plank)Pine on oak any suggestions?

[TomRobb]

Perhaps a semantic difference but I thought dutchmen were mostly small cosmetic patches having little structural significance. Maybe a bigger chunk scarfed in place might be better.
Perhaps it depends on the extent of the rot - the evil tendrels of which I hear can reach way beyond the obvious punky spots.

[WFK]

I think before you address the duchman question, you better find out where the water is coming from. To me I see a big red light when you mention "above the water line, around the chain plates". No point in doing a fix without addressing the problem.

Bill

[tsunami]

Its an odd situation The previous owner epoxy coated the upper hull(12mm!!) Its a bitch to get off and 97% stable whereever a crack developes and moisture is trapped, the rot developes. I have been restoring this boat for 7 yrs.I am going cruising this year and opt for the structural repair and recoat with epoxy.It is the quicker fix .I will moniter it.I am pulling the chain plates and removing the rot.Replace the wood(half of plank thicknes)and 5200 or epoxy glue.As un orthadox as the shell on the upper hull is its lasted 20 yrs.The guy spent alot of time on it.

[Ian McColgin]

Glad to see you're removing the chainplates. I see no reason why a dutchman replacing all the rotten wood will not do the trick. Just make the ends at least 8:1 bevel, top and bottom edges normal to the surface, and use epoxy, not 5200.

Interesting that you're reporting rot at the surface. That's the last place I get problems. Maybe use CPES as a sealer before adding other epoxy and paint??

I imagine the chainplates are through bolted, but whether yest or no, better fill those holes with epoxy - use something really thin like CPES for first injection so you soak into the endgrain - and then rebore.

G'luck

[tsunami]

The rot is all because of the MnM coating of epoxy.Its pretty stong but if a crack developes(very few all things considered) thats where the problem begins.The stuff is a #%&#*!!!! to remove and I dont want to do it.I like your input Ian.

[dickw]

tsunami,

I believe that the rule is to remove wood 4" past the dry rot because the spores are already there. It is surprising that the dry rot is on the outside as it is more common to start on the inside and work out unless it is under a chain plate or some fitting.

The 8 to 1 scarf solution of removing the the offending plank and scarfing in a new piece of plank with a long scarf is for sure a proper solution, but does require recaulking. The way to do it is to first cut out the dry rot with a plundging router using a rectangular jig, then build a jig that will plundge the router to the 8-1 scarf. You flip the jig over for the second side and use the same jig to cut the plank to the same angle. A friend of mine did it on my boat below the waterline a few years back and after caulking with cotton I left the Secoflex proud so that I can check it each year. It appears to be working well.
The complete project took about 2 days work from start to finish.

[dickw]

tsunami,

I believe that the rule is to remove wood 4" past the dry rot because the spores are already there. It is surprising that the dry rot is on the outside as it is more common to start on the inside and work out unless it is under a chain plate or some fitting.

The 8 to 1 scarf solution of removing the the offending plank and scarfing in a new piece of plank with a long scarf is for sure a proper solution, but does require recaulking. The way to do it is to first cut out the dry rot with a plundging router using a rectangular jig, then build a jig that will plundge the router to the 8-1 scarf. You flip the jig over for the second side and use the same jig to cut the plank to the same angle. A friend of mine did it on my boat below the waterline a few years back and after caulking with cotton I left the Secoflex proud so that I can check it each year. It appears to be working well.
The complete project took about 2 days work from start to finish.