Rot Doctor discovers polyurethane hull coating is good

[sdowney717]

http://www.rotdoctor.com/L/BoatL/bQA170.html

I am doing the same thing with sanitred permaflex. Just make sure your hull is sound not rotten and deteriorated. I was wondering when someone of some authority would also recognize the value and performance of a polyurethane coated hull.

[Gary E]

2) Take the hull down to wood, and, as you suggest, rout the seams to bare wood and epoxy-spline (we'd use our Tropical Hardwood Epoxy adhesive) with a soft wood, such as pine or western red cedar. Saturate the exterior with CPES, and then epoxy-sheathe with glass cloth and epoxy resin. Paint. This type of work has been done, and it will work if the hull is dry. The main downside is that epoxy/glass is not very flexible, and so some strain is produced as the wood attempts to expand and contract under different atmospheric conditions. It will produce a watertight hull if done correctly.

3) Follow the same procedure as above, except instead of using epoxy/glass as the final coating, use two coats of our ELASTUFF 120 Polyurethane coating followed by two coats of our UNIFLEX 255 Aliphatic Polyurethane. This produces an absolutely watertight coating, and the UNIFLEX 255 being totally UV resistant also produces the matte-gloss final finish. The big advantage of the poly coatings is that they always retain some flexibility, which reduces stresses on the hull as the wood expands/contracts.

After a few years of testing the polyurethane's, we have elected to use alternative #3 for our tug. She is now sitting inside a steel barn drying out, and we will begin removing all miscellaneous wood and paint down to the bare hull probably within the next 6 months. We are confident that this will produce a totally watertight final seal that will be good for 20++ years. It is a process that is also easily repaired, which epoxy resin in glass is not.

There is not such thing as "economical" in these kinds of matters. To do it right it costs what it costs.

Are you making splines for the Egg ?
All dried out?
Then coating with Sanitred?

Wow, that is a project...

[Jagermeister]

If I understand the pros and cons of splining (aka "wedge seaming"), there are three possible drawbacks relative to traditional caulking (aka "corking"):

1) If the planks take up water post splining, the splines will not compress, and the stress on the frames can break frames and/or fastenings.

2) If the planks dry out post splining, the splines, being glued to both planks, will not stretch, will "pull" on the plank edges, and can split the planks and/or splines.

3) If the boat flexes in a seaway, collision, etc., the planks will be unable to move relative to one another (temporary distortion while absorbing stress), and the resulting strains, concentrated at the glued spline line, can split planks, break frames, and/or fastenings. The boat is not rigid enough to resist flexing, but is too rigid to "give" during flexing.

Efforts to prevent (1) and (2) lead to encapsulation, which, if I understand correctly, must be near total to be effective. Of course, partial or improper encapsulation leads to "rot trap", of which more is explained elsewhere.

The suggestion for "flexible polyurethane" resolves an issue not even listed - that rigid encapsulation will crack under the stress of normal loading, causing the encapsulation to fail, and leading to any or all of the above failures.

So, even assuming "flexible polyurethane" encapsulation performs as suggested, it would (a) have to be total to prevent drawbacks (1) and/or (2) listed above, and would do nothing to address drawback (3).

As much as I like the idea, it still seems to me that an encapsulated hull is STILL not a cold molded hull. It has no diagonal or perpendicular grain to resist torsional movement, distribute the loads away from the plank interfaces, or otherwise make the hull more rigid.

Please don't misunderstand me. I would LOVE for this method to work. It would make my life so much easier. But, it still seems that the problems associated with wedge seaming a hull not designed for it remain. (And exactly how does one design for wedge seaming - I'm still unclear on that one?)

Lastly, the claim that "...this produces an absolutely watertight coating" is something of which I yet to hear any long term data. Googling for "sanitred permaflex" produces an almost evangelical flood of claims - but not much in the way of verifiable results (i.e., specific owners with specific hulls, dates, etc.).

If I've missed something, please correct me. But, if I've analyzed this correctly, the "miracle cure" remains elusively out of reach.

[Thad Van Gilder]

yeah... ok... you pays your money and you take your chances.

That stuff is still not going on one of my or my customer's boats!!!!
-Thad

[sdowney717]

No, I am not wedge seaming.

Basically what I did was remove all the bottom planks.
Renewed and or repaired the frames. The frames from stern to midship were basically gone in the deep bilge area. Plus the strut logs were gone.
Coated all the floors and frames with permaflex etc... inner side of the planks etc...
Then I reattached planks to frames. I pushed them all tight together. Used square drive #14 1.5 inch Bronze Boat Screws. Each side uses 2000 screws.
I then used polyurethane construction adhesive from Home Depot to fill the screw holes and forced it into the plank seams. I found if you take a vice grip you can flatten the end of the tube so it will fit easier into the seams. I only did this to form a flat smooth surface between the planks. I found it sands down easily with a random orbit and 40 grit paper. If you buy the very large tubes for $5 it is a decent cheap filler. Takes 7 or 8 large tubes to fill all the holes and seams. It expands as it cures.
If you use a putty knife you can press it back down and get rid of some of the large air bubbles that form as it cures.
Then I coated the hull with permaflex. I have one coat on and plan to put on a couple more.
I really thought wedge seaming the planks was uneccessary. What I have been wondering is using a stretchy Dynel cloth on the hull as extra insurance, but I really dont want to do that either.

[sdowney717]

Hi Jagermeister,
One really big benefit you may have missed is worms and gribbles will no longer be able to eat the wood. I have read some stories where people lost the boat from under them due to worm damage. Perhaps they did not know how to maintain their boat. But it made me think about it.
Some of my reasons are
I want a dry bilge.
I also dont want the pump runnning the battery down.
I dont want worms, critters eating the wood.
I dont want salt weepage eating my fasteners and salt angel hair shredding the wood fibers and degrading the hull. But I have probably read too many survey stories about wooden boats on yachtsurvey.com .
I have also thought the boat might shed some weight since it wont be dragging around 2000 pounds of water in the bilge and water saturated wet wood.
At least this is what I am hoping to achieve.

As far as excessive pressure on the planks from wedge seaming, these guys are using a soft wood like cedar. Also have you thought when a boat is new, planks are tight fitted, boat goes in the water, the planks swell and edges come together and form a crush zone sealing the gap. And then the planks move a little this way and that and evetually the edges can wear out after a long period of time.

I really think some wedge seaming failures are due to wasted or weakened fasteners and frames.

[sdowney717]

Hi GAry,

I pulled the boat out last september. The keel finally completely dried out in July.
It really is a very big job and taking a lot longer than I thought. I had rot damged frames and I had a fair amount of salt water weepage rot 'angel hair rot' on the shaft logs and some floors. This is where salt water weeps thru cracks etc,, dries out on the wood, salt crystals form on the wood surface and cut and shred the fibers. It looks just like a fuzzy rot that covers the wood surface. It was a problem that I had to get rid of and take a strike right to the source. The only way I thought to permanently stop this was to stop the salt water from getting into the hull. It just about destroyed one shaft log. And I was worried about all my bronze bolts. But they have held up well, the few that had corrosion damage lost maybe only 5 to 10% of their width. I had worms eating the stem and keel in places. Most of the planks were very good. A few had some damage. Most of the frame screw holes would not hold new screws due to rot. I must have drilled and a pluged a thousand screw holes in the frames. I just replaced every frame in the rear half of the boat. And I did have cracked frames mostly by the fuel tanks at the chine.

[Bob Cleek]

My, my... well, do keep us posted on how this repair technique holds up. As for keeping bilges dry, aside from a stuffing box, which SHOULD drip a bit underway, I've never had problems with leaks below the waterline. It seems that all the water leaks from the top down.

[Matt Cohen]

Just a note: CPES is pretty intense on your lungs. Make sure you use a Vap or Respirator (http://www.jamestowndistributors.com/find;a;1;ID;,Safety,3M.Respirators,Half.Mask.Respi rators,3M.Half.Mask.Kits) when applying it.

[Chris Coose]

Originally posted by Bob Cleek:
My, my... well, do keep us posted on how this repair technique holds up. As for keeping bilges dry, aside from a stuffing box, which SHOULD drip a bit underway, I've never had problems with leaks below the waterline. It seems that all the water leaks from the top down.Bob since Victoria had an extended period out of the water many years ago, she takes on a maintenance amount of water, 10-12 quarts a day. There is some around the CB trunk which is obviously the business around the spline seam which I think will take a rebuild.
But this haul season I'd like to take care of the plank seams.
As you may know, she is Cheoy Lee built and it appears the principle reliance is in the fit seams for tighnness. There is some dry hard caulk in the seams but no cotton I've ever seen.
What would be your approach and material for tightening her up?

[ 09-12-2005, 10:43 AM: Message edited by: Chris Coose ]

[Bob Cleek]

When was she built by Cheoy Lee and to what design? The teak planked Cheoy Lees I've seen, including my own, were apparently not caulked, but rather tight seamed. They should not leak that much. Have you checked your framing and floor timbers? Problems at the garboard are more often than not the result of floor timbers or fastenings going south. (See good discussion of this in McIntosh's "How to Build a Wooden Boat.") It's not likely the plank fastenings are bad, since they are probably copper rivets. You may have some shot floor timber bolts. The "hard stuff" you find in the seams is just a fairing compound, not caulking.

It IS possible to caulk tight seamed boats by running a circular saw blade which has been ground to a V shape down the seam, but that is a ticklish and tedious process and shouldn't be done until you are sure all the structural fastenings are holding everything where it should be.

If you provide more info, I'll keep and eye on this thread and pass on whatever occurs to me.

[Matt Cohen]

Inter lux Seam Compound (http://www.jamestowndistributors.com/find;a;1;ID;,Paints,Interlux.Compounds...Fillers,I nterlux.Seam.Compounds) is one common solution.

Also check out Sealants (http://www.jamestowndistributors.com/to;ID;,Caulking) and various Caulking cottons and compounds (http://www.jamestowndistributors.com/to;ID;,Caulking,Tools.Materials)

[Katherine]

Sdowny, I have been contemplating doing this to the Owens, minus the splines. I have the advantage that her hull is already extremely dry. Keep us posted on how it works out.

[Chris Coose]

Since I composed a new topic on this, let's go there.

[sdowney717]

Sure thing Katherine.
Also discovered recently the permaflex ever so slightly swells the wood which sort of makes sense as it does soak a little into the wood.

I have coated 2 coats. The buildup is between 1/32 and 1/16 of an inch for each coat depending on how hard you roll it out and or if it is thinned out with xylene. I bought 10 gallons and on this 37 foot boat, coated many inside planks, all floors and frames from midships aft, keel and keelson, strut and shaft logs, 2 coats on the starboard outside and still have 2.5 gallons left. Mostly since everything was apart, I had easy access to do this and could thorougly clean and examine everything.
I took 2 gallons to put 2 coats on one side of the boat.
Looks like I will get one more 5 gallon pail.
The thicker you put this stuff on, the stronger it gets. So I will put on one more coat on the outside for a total of 3 coats. I may lightly sand before the final coat to knock of some fuzzy lumps from the roller.
The bottom has a nice shiny gloss look now. And is really solid.
I have gotten a lot of interest from people at the yard.
I rolled this on using a small smooth foam roller. Tried a small fuzzy paint roller but since the stuff is so sticky it would sometimes pull fuzzy bits off the roller. It will also run and drip just like paint.