rot in mahogany

[Divine Wind]

How far from an area of rot in a carvel plank would you take out to be reasonably certain to stop it. Also in beams of oak under ply decks.
regards, divine.

[Elco's]

Replace the entire plank. Replace the entire beam. If its into the polywood, replace the entire piece.

"to be reasonably certain to stop it"

[ 08-01-2004, 10:24 PM: Message edited by: Elco's ]

[Gary E]

"Replace the entire plank. Replace the entire beam. If its into the polywood, replace the entire piece"

Whut a crock a crap.

do you have the tooth pulled if it's just a cavity?
or the ashtrays in the car dirty so ya replace it?
or the tire go flat and ya dont fix it?

You fix what needs fixin, unless your the yard manager selling repairs on commission to unknowing boat owners.

G

[Dave Hadfield]

The sides of the cabin on my ketch are 18" x 1 1/4" mahogany boards. (Nice stock!) Last year I had to deal with rot induced from water seeping down from a poorly repaired companionway (not done by me).

I cut away until I was quite sure I was back to solid wood. Then I cut away some more. Then I soaked it with S1 epoxy sealer. Then I glued and fastened in the new piece. (sounds easy -- took a week.)

In 10 years I guess I'll know if I did it right.

Good luck.

[Oyvind Snibsoer]

The norm for house restoration in these parts is to cut a rotten plank 1 m/3' from where you can see the rot stops. OTOH, this would be in softwood, and the spores may not migrate so easily along the grain of mahogany.

[Scott Rosen]

I would cut until you get to sound wood. Then I would soak the end grain and nearby areas with a borate solution to prevent any further rot.

When that was good and dry, I'd seal the end grain with CPES or some other epoxy. Scarf in the replacement and you're ready to go.

[Paul Stohlman]

How much of the plank is rotten? The solution may be as easy as a dutchman for a small spot, or plank replacement if it is worse.

You can replace a section of a plank, but you have to consider where the butt joints will lie in relation to others. Too many, too close will make the whole structure weaker.

Deck beams are harder to get to, and may require a different approach, such as temporary fix now, permanent fix when enough of the deck needs attention.

Beware of epoxy as a cure. It is great as a glue, but it will not fix, stop, or prevent rot any better than other time tested methods.

[Elco's]

Wow Gary...time to take a laxitive?

Unless you know to what extent the microscopic spores that are the rot fungis, have permeated the plank,beam,plywood, then anything other than replacement is a bigger gamble in spent time and effort, then leaving the rot alone.

The decaying of the wood is the final stages of rot. Which means all of the other stages are in the lumber and undetected as to what extent.

Especially in plywood. As the rot enters each veneer, it travels with the grain, 180 degrees in opposite directions for each veneer. So replacement of the entire piece of plywood is recommended.

The only effective rot killing treatment (not final stage) is a borate solution. NOT CPES or anyother of the latest "wonder treatments". Coating any rot in either a plank, beam or plywood with an epoxy will create an incubation type situation where the rot will be excellorated.

Replace the plank, replace the beam, replace the entire piece of plywood.

Until you offer more specifics and/or pictures that better explain the situation...a general question deserves a general answer.

[ 08-01-2004, 09:37 PM: Message edited by: Elco's ]

[Gary E]

You still sound like a yard manager selling on commission.

[Elco's]

And you choose to post that? Got a problem Gary?
Do you treat everyone on here in that manner? or do I have the distinct pleasure of being singled out?

[ 08-01-2004, 10:59 PM: Message edited by: Elco's ]

[Bruce Hooke]

Elco,

For whatever it's worth, replacing only the rotten area seems to be pretty much standard practice, as evidenced by the numerous preceeding posts that talk about that method.

According to the Gougeon Brother's book, encapsulated a piece of wood in epoxy greatly cuts down on the oxygen that gets to the rot spores, thus greatly slowing or even essentially stopping their activity.

It's been my understanding that rot spores are pretty much always present, even in new wood, so trying to remove all the wood that might have rot spores in it is pretty much futile. The idea as I understand it is to create conditions that are not condusive to the rot spores growth and development.

[Elco's]

Yes and no, Bruce.
First off.....is Divine wind's question retorical or of an actual boat?
What size, useage, age and wood is used in its construction?
Given what little information one has to go on.....do you begin with a treatise of vessel repair? What about those beams...are they laminated or cut or grown? The planking...mahogany,full length planks in a 16 foot boat or 3 seperate coarses in a 40 foot boat? And that plywood deck on those beams. Is there an adequate beam shelf? Is the plywood epoxied down? Is it marine grade plywood? and what is the deck treatment?

If you don't get all of the rot in the plank when you go "surgically" slicing it up...then you've wasted your time...plus, every time you lop off the end of that plank you are adding a BUTT block and removing the intial strength from the boat that a solid plank gives. DITTO for the beam. Who would splice a beam end?

Sure, you could patch in any and everywhere you want...and only fix the most of the degraded plank,beam, ply....and in 6 months you can do it all over again, only cutting back another 6" of rot. Why, you could continue to cut out and repair a single plank over and over and over.

If it is rotten, replace it.

Encaspilation of wood containing rot will create an encubator that favors the degradation. Coating a rotten area with epoxy will speed up the growth of fungi.

It has to do with optimal conditions, the right tempreture, the right moisture content and STAGNET air. Gouegeon's advice can only pertain to non rotted wood. If you epoxy coat rotted wood, you are sealing the rot off from fresh air and making it warmer.

Rot spores are in the air. Not necessarily in the wood. In fact, when kiln dried lumber reaches certain tempretures (don't quote me but around 170 degrees F) rot dies. In fact, if your were so inclined, you could litterally "bake" the live rot from a wood boat by covering it and raising the tempreture.

So, the rot spores in the air, get into the wood (only because the conditions are optimal) the wood rots, you see the deterioration (perhaps due to paint flaking off the plank). You remove the plank and replace it. You also repair the condition that made it optimal for the fungi spores to propagate. Such as a window leak above ect.

Perhaps where you are the practice of "patch upon patch" prevails....not on my boat. And, I would never suggest that some one repair thier boat in any way or manner that I would not do on my own.

Until Divine Wind gives us something more to go on...you cannot get anymore general than his posed question,how can you give anymore of a specific answer?

[ 08-02-2004, 12:46 AM: Message edited by: Elco's ]

[Bruce Hooke]

Now I think we are getting to the truth of the matter, which is that we do not have enough information to give a definite answer. Clearly, to take a pair extreme examples, if we are talking about a 1/4" diameter area of soft wood around a single screw in an otherwise sound 40' long plank then replacing the entire plank would be a bit over the top, but if there are substantial pockets of rot in many places along the plank then it would be foolish to think that the plank could be saved. So, I would hope that we could agree that there are times when a simple graving piece is the appropriate solution and there are times when removing and replacing the entire piece is the only smart solution. I'd say that an important part of the equation is understanding why the rot happened in the first place. If the cause is very isolated then a graving piece is more likely to make sense versus if the cause is that the whole piece of wood is getting tired and one area just happened to show the most obvious signs of rot first.

If I may be so bold, what you, and we, probably should have done before answering the original question with simple "solutions" is ask some of the questions you just asked.

While I agree that coating clearly rotten wood with epoxy is a waste of time, your statement that rots spores are in the air pretty much comes back to what I said, which is that there are always going to be rot spores around, at least on the surface of wood that is exposed to the air. So, we have to assume that rot spores are always going to be present and ready to grow given suitable temperature, moisture and oxygen levels. Now, while epoxy coating (sound) wood may produce a warmer environment, if Gougeon Brother's are right (and I'm inclined to believe them since they have a heck of a lot of experience with epoxy boatbuilding) it also reportedly produces a de-oxygenated environment wherein a relatively small number of rot spores will have a hard time growing into a significant problem. Of course, if there are already massive numbers of rot spores present in the piece of wood in question then that is another matter.

[Elco's]

Yes Bruce, I do agree.
In new boat construction, where the wood is known to be sound, encapsulation as part of the building process...is totally different from encapsulating wood on an existing vessel.
Dutchmen have thier place in specific situations as does encapsulation...BUT we don't have enough information to know if those situations do in fact exist.

Encapsulation does not make wood "rot-proof". Removing 1 of the 3 conditions required for rot to propagate, makes rot more unlikely to occur. These are 1)tempreture, 2)moisture content, 3)oxygen. Encapsulation can increase the tempreture, stablize the moisture content and lessen the flow of fresh oxygen. These 3 things can generate the opposite effect by
stablizing the wood in the optimal conditions for rot. When rot spores already exist in the wood, encapsulation is the last thing you would want to do.

[ 08-02-2004, 09:18 AM: Message edited by: Elco's ]

[Dan McCosh]

Having done lots of rot repairs involving partial plank replacement, I've seen some fail and most succeed. That is, after 10 years, no recurring problems in the same areas. Some paritial plank replacements are 20 years old. I generally cut back to about a foot away from any detectible signs of rot. That probably about 18 ins. from noticably soft wood. Also, I generally glue in the replacement by scarfing, rather than using conventional butt blocks. It hasn't been entirely foolproof. I have had two spots where the rot continued, which showed up about four years after the initial repair. I'd estimate this represents a failure rate of about 2%. I've also done partial ribs, as well as whole planks and ribs. I feel the issue is always a trade-off. A longish plank. (in my case, this can be up to 15 feet.) involves lots of collateral damage removing it. I've had many problems that mainly involve a rotten butt block and a couple of inches nearby. Ripping out substantial planking where a few inches of rot is the problem is overkill. Likewise, some planks actually have a series of similar spots, hence need complete replacement.

[Divine Wind]

lads, what can I say, so much advice to mull over!
The boat is real, 34-6" of mahogany on laminated oroco, with teak on top. Main areas of rot seem to be above the waterline at the stern and under the transom or counter, in small patches in several different planks of six feet long. Sparkman and stephens designed, with all lead keel and bronze lifting keel with bronze fittings.
There is no rot on deck or above but can't see all the deckbeams but all sound ok.

[Scott Rosen]

There are two separate problems that need to be addressed. We don't really need more information.

First, the rotten wood needs to be replaced/reparied.

Second, the conditions that allowed the rot to develop need to be identified and changed, if possible.

Both of these problems have been addressed in the posts above. However, I would strongly urge the use of borates in any such repair. Once the wood is treated with the borate solution, allowed to dry and then painted, the borates won't leach out through the paint and will continue to penetrate the moist areas of the wood. Borates won't affect the strength of epoxy glue joints and won't affect the adhesion of paint.

P.S. In some instances it could be much easier and quicker to replace an entire plank, as you can remove the plank without any cutting, and you can use the old plank as a pattern for the new.

[ 08-08-2004, 11:44 AM: Message edited by: Scott Rosen ]

[RichardBlake]

You're probably way ahead of me on this, but on the subject of what causes the rot, counters do tend to rot from the inside out: Lack of ventilation, insufficient or blocked limber holes in the counter frames creating puddles, total inaccessibility meaning that the coatings on the wood up in there haven't been renewed in 20 years. Sorry to be a pessimist, but in a slender counter the amount of plank you remove may have more to do with being able to get in there to tackle these causes than just to replace what seems rotten on the surface. I'm doing one myself at the moment, so am admittedly somewhat obsessed.
In terms of the discussions above, I'm replacing a few key planks in long lengths, symmetrically each side, and with others I'm removing 2 to 3 feet measured from the transom and scarphing, 11 or 12 to one. Recommend lip scarphs rather than feather ends, to keep the main epoxy glue interface well below the surface. Tack a couple of battens on to the boat above and below the strake, with blocks under one end to get the scarph angle and make the battens well parallel, and rout! (Erm.. should add, if you're at my level of experience, greatly enlarge the base of your router by screwing a sheet of plywood to it, about 10 cm by 20 cm, and add extra deeper battens outside and parallel to the first, for the ply edge to touch and stop you shooting off onto the adjoining strake! The careful measuring time is worth it!)

Good luck.

(All suggestions thoroughly based on experience, the latter, however, limited.)