Luders 16 rebuild

[Etienne]

I have a wood L-16 that has been glassed over. Looking for a few other thoughts on the plan of attack. Leave the glass or strip it?

Thanks
ET

[seo]

I will make this one comment once, and then duck the likely deluge of contempt.
FRP is a pretty good sheathing for a cold molded hull. Some of the very most snazz-ola cold-molded wood/plastic glue boats are sheathed with plastic resin and fiber matrix.
Is kevlar or some other miracle aramid better than glass? Probably. Worth the cost? Dunno
Is epoxy better than polyester? Probably. Worth the cost? Depends on how much you have to spend.
A hot-molded L-16 does not come and go like a carvel planked hull, and does not have a lot of troublesome hull penetrations. It's a pretty good candidate for being sheathed with FRP, in my opinion.
I would suggest that you do (or have done) a careful inspection of the hull. The ideal time would be when the boat is dry from winter storage, and has been sanded down. A electronic radio frequency miracle moisture tester is a big help. So is a good eye, a good ear for different qualities of sound, and a sensitive thumb that can detect "give" in the sheathing that indicates the wood underneath is soft. The ear is to hear the "clicking" sound that FRP sheathing makes when it's tapped, and it deflects in and taps the underlying wood.
A very useful preliminary is to measure where the various stringers, bulkheads, stiffeners, etc, are, and then draw them in chalk on the outside of the hull. This is a great help in visualizing the interior structure, and analyzing why the hull sounds very dead HERE (You're tapping on top of a solid bulkhead), or very vibrant THERE (Sound dry hull, clear of interior structure) or very DEAD there (No interior structure. hmmmm. What can it be?)
That's about all I can tell you. After doing this for 22 years, I think it's true that the second hundred boats you inspect will go better than the first hundred.
If there aren't soft spots in the wood, or spots where the FRP has pulled loose from the wood substrate, my suggestion would be to leave it alone. Unless you're in an unusual area, an L16 is neither terribly rare nor highly sought after. I myself, speaking only for myself, would be inclined to spend my time enjoying the boat for what she's really good at, which is sailing...
SEO

[Etienne]

Thanks SEO, was thinking the same.

[hm0316]

Etienne, it would be helpful if you would give us some more detail about what problems you are trying to address and what you are trying to accomplish. Does the boat currently leak? Are there any obvious problems, such as delamination? Hot molded Luders 16s begin to leak around the keel batten and delaminate in that area as well as around the joint between the deck and topsides. Most fiberglass jobs are attempts to fix these strutural problems. It will not work unless you first address the structural problems. There is nothing wrong with a layer of fiberglass on the hot molded hull. It will provide some protection and help limit delamination around the end grain of the molded laminations. Fiberglass will not, however, solve structural problems.

Just my opinion, but I believe properly restored wooden Luders 16s are rare and good wooden restoration candidates are sought after. If you have not already seen it, you might enjoy reading the cover story on the Luders 16 in the April 2004 WoodenBoat volume 177.

Let us know what your situation is and what you are trying to accomplish.

hm0316

[seo]

HM0316:
I agree with your general point about structural integrity. Problems with FRP sheathing are common at the hull/deck joint. There's often a problem with how to sheath a hull with an external lead ballast keel. 1) Just sort of end the sheathing at the wood/lead joint? 2)Drop the ballast, sheath the keel, rebolt the ballast? 3) Sheath around the ballast?
#1 has problems. because if the structure that the ballast is fastened to isn't stable, the ballast keel bolts can start to leak, or the garboard joint.
#2 is a lot of work, and often people who sheath wooden hulls are looking for quick and dirty solutions.
#3 might work with lead. I think it will surely not work with iron, where rust expansion will crack the sheathing.
A boatbuilder/surveyor named Alan Vaitses wrote a book about sheathing wooden boats a long time ago. He supports your point that the structure has to be stable before sheathing will work. He stresses the importance of mechanical fastenings through the sheathing into the hull.
I do wonder whether it might not be possible to use FRP sheathing to stabilize the keel/ballast joint. If the sheathing is built up to structural thickness from the turn of the bilge and down under the ballast, and is well fastened with screws to the planking. The screws are covered with the last layer of FRP...
This may sound like apostasy, but take a look at how some of Herreshof's big racing yachts were built, with bronze strapping on the OUTSIDE of the hull, running down over the keel and fastened to the ballast. It seems to me that he was on to something-any reinforcement there has the best angle on the strains generated by a heeled-over hull with a big ballast keel. If the same reinforcement can be provided with a low-tech material, wouldn't that be good? It might also be a lot quicker and cheaper than doing a lot of structural work inside the hull.
The girths of the hull might grow enough so that she's no longer considered an L-16 for one design racing, depending on how picky the measurer is.
One place where we may disagree is on the demand for L-16's. You write that they're "sought after" for restoration, which may well be true in some places. But are the seekers willing to pay a fair price for the hull, which I define as being the cost of a boat to replace the L-16 with?
As an example, I know of a case of someone inheriting a Herreshof 12 1/2 in not very good shape. He was considering sheathing it, when a potential buyer showed up and offered him $500 for the boat, pointing out that he'd end up spending many thousands restoring it to its former glory. The owner wasn't interested in glory-just in a boat to go sailing it. He pointed out that $500 wasn't going to buy him a boat, and if he could repair the 12 1/2 to functional condition for $1,200 wouldn't he be better off doing that? In other words, the offered $500 plus the 1,200 for repair wouldn't buy a used fiberglass "doughdish." or a Cape Dory Typhoon.
The potential buyer felt that he was preserving an historical artifact, and felt that the owner should sell cheap to help with the preservation. The owner felt that the buyer was just fixing up an old boat into a fancy toy and status object.

Other than some highly desirable types, maybe an Adirondack guideboat or an E.M. White canoe, maybe a historical Whitehall, maybe some very famous individual boat (Maybe "Stormy Weather", maybe one of N.G. Herreshof's personal boats...) I don't think that restoring wooden boats is often a paying proposition for the guy writing the checks. I'm sure there are exceptions to that observation.
A friend of mine still owns the first car he ever bought, a 1967 Ford Mustang fastback, 289 engine, four speed transmission. He has upgraded it with radial tires, keeps it in a garage, doesn't drive it on snowy roads. It's a toy, not a daily driver. People are always trying to buy it for 5-10,000, pointing out that they'll end up spending four times that "restoring" it to show-winner standards. He has come up with a standard response, which is that he'll trade it even-up for a new Mustang. Last I heard there were no takers...

But it certainly does seem logical to try to sell a boat that might have some collector value if it needs significant repair. Right now there are lots of pretty nice boats on the market cheap. If the Luders could be essentially "traded" for a boat of equal utility, with simpler and cheaper upkeep, that might be a rational approach.

[DLW]

seo - I disagree with you completely. It does not matter whether or not the boat was hot, cold molded or traditional build. Sheathing fiberglass around the outside of a boat is bad news unless it is done properly. When you put fiberglass on the outside of any boat you are basically creating a giant bucket and all the water just sits in the wood slowly rotting it from the inside out.

Etienne - look at my rebuild of my L-24 it is well documented on this board, and will give you an idea of what kind of damage can and probably does exist with your boat. If you have questions feel free to PM me.

[hm0316]

Etienne, I agree with DLW. His L24 project has been well document in this forum and has been done by a highly reputable and experienced professional. You would do well to look at it.

To make a long story short, you can't "fix" a problem with fiberglass. In some applications, done properly, it can protect molded construction and limit water saturation at the end grain of laminations; that is about it. If you are trying to make the boat stop leaking or make the hull "stronger" because it is falling apart, it will not work.

If you are serious about a restoration, you would do well to get a set of drawings of the L16, which are available from Delta Marine Small Craft Design in Brownfield, Me. There are some design problems that need to be corrected in a rebuild, principally relating to the keel batten and floors being too light. The drawings will help to understand these.

Good luck, hm0316

[bamamick]

This is a very interesting subject to me, as I am the owner of a wooden Dragon with the class-legal layer of 'glass covering it.

When I brought my boat home I had two options: the first was to do a complete restoration, which means take it apart piece by piece and replace everything more or less (build a new boat on the old ballast keel). That was never going to happen with my financial situation, but what we could do we did. We replaced a bunch of frames, some planking, and then glassed it.

Where I live we do not have hard freezes, and I had been led to believe that this was really my only practical choice. As my boat builder said, I could have my boat and sail for what will likely be the rest of my life, or I could not. How long will she last after I am gone? Don't have a clue. Not forever, of course. But neither would the rebuilt boat. A boat is only as good as it's next owner, and there are no guarantees.

I know that a lot of folks here are purists and I really, really respect that, but we have a twelve month season down here and though I sometimes wish that I had been able to afford to have done a traditional rebuild, I can't really get too mad at myself. My boat is sailing and racing at the age of 46 years old.

If I had my 'druthers I would go for the traditional rebuild. No doubt about it. On the other hand, a Dragon that was doomed to die an ignomious death probably gained another 25-30 years of life (we have wooden Fish class boats that we glassed that long ago that are still going strong). I can't say that either way is the wrong way, as long as both are done correctly.

jmo Mickey Lake

[Don Z.]

I agree with DLW. I'm currently undergoing a similar refit on the 8mR. The glass keeps water against the wood and can't get out. The wood fibers will transport the water farther than you might think. I'd strip it.

[hm0316]

bamamick, everyone has to decide what they can do and I have nothing but respect for someone who wants to extend the useful life of a wooden boat. Anything that will keep the boat together is better than letting it fall apart on the hard. That said, here are a few observations.

The L16 is not a traditional plank of frame boat but rather is a "hot molded" lamination. Perhaps because wooden L16s are laminated, there has been a fair amount of experience with attempted fiberglass repair of hot molded L16's. It is often tried when there is a leak and it may stop the leaking for a while. It will, however, allow the delamination and structural failure causing the leak to continue. The "next time" the boat starts to leak additional fiberglass lamination is unlikely to work and the situation will be harder to repair.

To know if or how well sheathing will help with respect to Etienne's particular hull, even for a few seasons, we would have to know more about Etienne's boat than we do now. I gather from his first post that the hull has already been fiberglassed and that he is, for some reason, considering a "rebuild". Etienne hasn't said anything since his orginal post so it may be he has decided the advice he is getting is worth what he is paying for it. If he is still interested, however, it would be helpful to know if the hull has been laminated with glass for a long time and if it is currently leaking. It would also be very helpful to know how easily one can push an ice pick into the wood (once it goes through the fiberglass) around the area where the hull is in contact with the deadwood.

A very good article on the subject of sheathing is Richard Jagel's
"Sheathing vs. Encapsulation" in WoodenBoat, vol. 123. It is a detailed analysis of the consequences of sheathing a particular boat. There Jagels, who is a well known expert on wood who regularly publishes in WoodenBoat, discusses what would happen if a new cedar strip outboard were sheathed. His discussion, among other things, demonstates the importance of evaluating the specifics of the hull and its envoronment before sheathing, even with a construction methodology that often uses a fiberglass lamination.

hm0316

[Etienne]

She is a 1948 hull at was finished out in Newport Beach. In 1998 the boat was epoxied in and out, deck was replaced, and the hull was glassed to give it a smooth finish. Glass does go around the lead. It has been out of the water for some time, shows
no delamination, and have yet to find a dead spot. I would like to pull some glass to check the deadwood as mentioned. I just lifted the boat and put it on a cradle as the trailer was not mine, and have been stripping the hardware off the mast getting ready to give it a once over. Looking to deal with the hull in May and apperciate all the info. Will get some photos posted. ET

[DLW]

My question would be was the wood replaced in 1988, or was the epoxy put over rotten wood. The fact that the glass wraps around the ballast is in itself bad news, generally. You are going to need to do some exploring,

[hm0316]

Etienne, that is very helpful information.

Based on the fact that the work is fairly recent and that they replaced the deck (which is another major problem area) there is some chance that the issues around the keel batten (which are very common in L16's of that age) were also addressed. I take it that the fiberglass actually is wrapped around the ballast keel. That may mean that the dead wood and ballast were not dropped at the time the work was done. I would have suggested dropping the dead wood and ballast keel and "wrapping" just from the keel batten up primarily because the deadwood is not laminated but some might debate that. Also, it would be best if they had replaced the floors with larger ones. The originals were 1 3/8 inch oak which are too light for the forces created by the keel when heeled. You can measure the floors to see what the situation is. Also look carefully at the "keel batten" which you can see from the inside of the boat. It is the long plank that connects the two sides of the the bottom of the molded hull. It is laminated mahogany and it is glued to the hull and takes the lateral pressure of the keel when the boat heels. It is too light as designed and is a contributing reason for leakage and delamination in the hull. Look for any stress fractures or cracking or separation from the hull.

If you find any softness or delamination around the keel batten, then you may have some hard decisions to make. A proper rebuild of a molded hull is expensive and/or time consuming. Depending on how many layers of fiberglass were used around the keel area, you might not see any obvious problems for quite a while. You might want to put it in the water and sail it for a year and see what happens. If there are problems around the keel batten, they will get worse, but the boat could be fine to sail for many years. I am sure it is obvious, but any holes you poke in the fiberglass should be filled with epoxy since the objective with a molded hull is to keep the water out.

Good luck with your project. The L16 is a fine looking boat, particularly in its wood version.

hm0316

[hm0316]

I just reread your post and wanted to mention that the problems, if any, will probably not be in the deadwood but in the area of the hull just above the dead wood. This is where the lateral pressures of the keel when heeled are likely to have caused cracking or delamination in the hot molded hull. hm0316

[Tom Robb]

Re seo's point #3:
Alan Vaitses' sheathing method IIRC concerns carvel planked hulls - a very different animal than your molded hull. All that mechanical fastening may not only be beside the point but may be detrimental.
If feasible it would be good if anything you do to fix her would be undo-able by the next guy who wants to do a perfection restoration. I do get it that not everyone sees these boats as valuable historic artifacts.
Good luck with your project. Really neat boats BTW.

[seo]

The logical reason for using mechanical fastenings through an FRP sheathing is to improve the shear strength of the hull/sheathing joint. This would be critical if you decided to try the method of building up the sheathing to STRUCTURAL thickness from the turn of the bilge down around the ballast. Structure added here, at the outside of the angles of stress, might go far to stabilize a hull that as people have pointed out above, is deficient in strength at the keel/hull joint.
This might be just as strong as the more orthodox approach of dropping the ballast, rebuilding the batten keel, renewing the floor timbers.
Does anyone have a bill of materials and time budget for that job?

One theory, and it's only a theory, for why FRP sheathing works better than people often expect is that the water that finds its way into the (this is a great word, one of my favorites) intersticial spaces between the wood and FRP is quickly depleted of oxygen by biological activity in the wood. Once the O has been used up, respiration (and rot) stops. Sort of like the Gokstad viking ship lasting all those hundreds of years underwater, sunk in glurk. No oxygen, rot stops. No water flow, no new O finds its way in.
One obvious area of concern is freeze/thaw of intersticial (God, I love that word!) water. This is the force that Nature picked out of its toolbox when it decided to crumble the lofty mountains, and it is incredibly powerful.
One obvious workaround is to move the boat to a sunny place, preferably with palm trees, swaying maidens, frosty glasses. Another is to heat the storage space.
Maybe the best approach is to store the boat in a shed without windows, northern exposure, where the hull will hopefully freeze once in the fall, thaw once in the spring, and be frozen hard in between.
Just like the normal progress of rot will progress along its Malthusian curve when the weather is warm, so to it will grind to a halt at freezing temperatures, when the rotganisms go into hibernation. I base this opinion on having inspected a number of wooden hulls in places like Duluth and Sturgeon Bay, places where you'd expect to find punk-rotten bonfire candidates, destroyed by all that freshwater. "Freshwater, water, everywhere, and all of it we could drink..." My guess is that what kept these boats so remarkable sound was how cold the water is, and how cold the temperatures that the boat's were stored in. Duluth is not a spot often visited by January thaw...

[DLW]

I can't imagine a worse idea than putting mechanical fasteners through a fiberglass sheathing. This old school thought and process has long since failed at being a good idea. Having water sit and being captured against wood does not result in anything good.

I know this because I am living it with my restoration.

[hm0316]

DLW is correct. hm0316

[John Meachen]

To get to the point the original poster raised,a hot moulded hull and epoxy sheathing should be about the most durable thing afloat.Hot moulded hulls from forty or more years ago seem to be almost indestructible and what could be a better covering than epoxy and glass.The experiences and attitudes of the naysayers may be of relevance when referring to plank on frame construction which has been sheathed after an amount of use and with oil based paints having been initially used.The sheathing of the keel need not be catastrophic in temperate regions as the thermal movement of the metal will not be as great.It would be best if there were sufficient glass to cope with the ballast.There are quite a few production boats which have a large ballast keel dropped in to the moulded hull and then retained by a laminate over the top of the keel.No keelbolts and no leakage are useful attributes.Glassed over rot was never a good idea and I would be curious to know if an ultrasonic scanner could differentiate between sound wood and compost.

[hm0316]

John, I am not sure anyone has been a naysayer with respect to the feasibility of using glass and epoxy to cover a hot or cold molded hull or encapsulating a ballast keel if the boat were designed for that treatment or prepared for it through proper repair and/or modification. (I would say no unequivocally to using screws to try to attach fiberglass mechanically to a molded hull). The problem here relates to a Luders 16. The original design of the wooden version of that boat produces delamination and structual failure around the keel batten and around the deck. Also, the boat has comparativley large solid deadwood. Sheathing the area of delamination will not solve the delamination and structural deterioration and wrapping the deadwood may cause another problem. Etienne has bought a boat that may (or may not) have been properly repaired 9 years ago. My objective has not been to criticize the use of a material but rather was trying to assist someone who has a very handsome boat that is worth preserving and is trying to figure out the best thing to do. It is entirely possible that the best thing will be to do nothing.

hm0316

[Peter Malcolm Jardine]

Some of the questions I ask about any repair on almost anything.

Was the original method/design of build a good one?

What led to the nature of the fault that now requires repair?

Is my method of repair an increase, a decrease, in the quality of the original method of build?

Is my method of repair a best temporary fix, a permanent upgraded rebuild, or a restoration of the original build method?

If all the answers are honest, and those answers are accepted by the owner/builder/restorer.... then off you go.

The contrary is, of course, that the fix is not an improvement on the orginal build, and will not correct the original fault, but merely mask or temporarily deal with a structural issue. Personally, I won't spend a lot of time or money doing something in that ilk. It's a waste of my resources, and in the end disappoints me with the results anyway

[seo]

I think that at least some of the cold-molded boats built by Brooklin Boat yard are sheathed with FRP. I wonder if they are destined to failure? I guess the same could be wondered of the Herreshoff and Nevins-built hulls that were double-planked with a layer of canvas and white lead paste in between. That is not a permeable material, and some of those boats are around 100 years old.

I think the value of mechanical fastenings as part of an FRP sheathing is in sheathing a hull that isn't new, using polyester instead of epoxy. The mechanical fastenings provide shear strength and help prevent peel failure. The most common fastener I've seen used is monel staples, short enough that they don't come through the wood. If you're using, say, three layers of FRP you put the staples in when two layers are on, still green enough so that the staples penetrate easily. The last layer goes on to cover the staples.
I have been involved in repairs of hulls that were sheathed like that, and needed to be fixed after grounding damage. The sheathing was remarkably tenacious, and the wood underneath was by all appearances about the same as when it was sheathed.

Obviously, a complete overhaul using original materials and methods might be the best thing, if there's money enough to do it. I'd be very curious to hear from someone who has done this "new floors and batten keel repair" job how many hours went into it, and how much money for materials.

If someone has the money or time for that repair, then good on them, and Bob's y'r uncle. But if that's not the case, then it's logical to try to figure out a repair that works. Otherwise, the boat is on its way to the compost heap or into some rich guy's collection of concours status objects. Which is also fine with me, personally.

Small yachts of the 1940's are not pyramids, or even cathedrals. Their life span may well be less than a hundred years. If someone were to ask me for a "permanent solution," I'd first ask him if he was a nazi, and second ask if he was planning to live forever.

[Don Z.]

As a naysayer, I'll reiterate what I said earlier. I'm spending a lot of time and effort fixing an 8mR that was sheathed with glass. The boat was cold molded in 1983 by Bent Jesperssen. If water gets in (usually osmotic, but not always) between the glass and the wood, it has difficulty getting out, and this can lead to problems. Yes, plank on frame will cause problems. Cold molding, however, is not impervious to the problems.

[rbgarr]

Assuming careful construction, application and maintenance, do people find the same problems with fabrics epoxied onto plywood decks also, or is it mainly when used below the waterline that water intrusion and rot problems occur?

[seo]

Don Z.
How can you tell whether water go in between the sheathing and wood hull by "osmosis"?
For that matter, how do you define osmosis? I have a pretty good idea of how it's used in biology and botany, and how it's used in describing how something like a "reverse osmosis desalinator" works, which isn't really osmosis, if you go by the following definition, from Wikipedia:
"Osmosis is the diffusion of water through a semi-permeable membrane, from a solution of low solute concentration (high water potential) to a solution with high solute concentration (low water potential), up a solute concentration gradient. The simplest definition is that it is diffusion of water across a semipermeable membrane.[1] It is a physical process in which a solvent moves, without input of energy, across a semi-permeable membrane (permeable to the solvent, but not the solute) separating two solutions of different concentrations."
I don't think that FRP can be said to have "cell membranes," and even though living trees certainly use osmosis all the time in cell respiration, I think that that's only in the sap wood, leaves, and in the roots. I don't think that the wood that is lignified has cell membranes, but maybe they do.
So anyway, how do you tell between water that's leaked through a crack or pinhole in the sheathing, and water that's leaked out through the hull.
As I understand it, both wood and FRP are permeable to water, particularly water vapor. The rate depends on how thick the hull, and what type of material.
There are materials, like "Typar" sheeting that they use on houses, and "Gore-tex" that they use in clothing, that is a sheet that has holes in it big enough for water vapor to pass through, but too small for liquid water, which suggests that permeability isn't exactly simple.
My understanding is that the rate of permeation in a typical hull is so low that it evaporates off the inside of the hull without being noticed. Above the waterline I guess it's possible for permeation to be going the other direction, with water vapor moving from the humid inside to the dry outside of the hull.
But anyway, if water is building up in the layer between sheathing and planking, it would be very interesting to know where it came from. Is it permeating in through the sheathing, or out through the planking? Or is it just leaking through a crack?
One aspect of this whole topic that hasn't been mentioned is that of shipworms. For some reason shipworms seem to be extending their range northwards. Belfast Maine now has worms, where it never did before?

Why? Evolution? Warmer water? Wrath of God? dunno.

So far, I haven't heard that worms can make a hole in FRP sheathing. Although that may be the next step...

SEO

[hm0316]

Jardine, I agree with your list of questions. With respect to the Luders 16, it does have original design flaws that lead to delamaination and failure. They can be corrected and a solid, long lived boat will result. As I previously suggested, it is helpful to have a set of plans before undertaking a restoration and plans for the L16 are available. A review of them in conjunction with an inspection of the boat will make the problems I have been discussing fairly obvious.

SEO, Brooklin Boat Yard makes outstanding cold molded hulls and does use other laminates in addition to wood. They are designed from the outset to be built using that method and do not present the issues associated with using laminates with hulls not designed for composite construction. BBY boats are expensive and worth every penny. I would observe, however, that the cost of properly restoring a classic to pristine and solid condition is not materially different from new construction from a quality yard. Indeed, Brooklin Boat Yard and many other reputable yards do both quite well. I hope that answers your question.

rbgarr, the presence of delamination is not dependent on whether the material is above or below the waterline. Rather, it is primarily dependent upon whether there is water penetration along the end grain of the laminates. Because wooden L16 were built 60 years ago in substantial numbers, the L16 is an important boat for understanding the long term problems and benefits of wood lamination. When the L16 was built, the demands of monocoque/laminate construction were even less well understood than today so they provide a useful laboratory for examining failure in wood laminate construction. What one sees repeatedly in wooden L16s are failures both above the waterline, in the deck and top sides around the joinder of the two, and in the lower part of the hull around the keel batten. This is primarily due to water penetration along the end grain. The hulls between these two areas of delamination (either above or below the waterline) are absolutely solid even after 60 years.

hm0316

[Don Z.]

Well, I did use the term osmosis, but I also said "not always". I was thinking in terms of "Osmotic Blistering", which may be mis-named, but is a fairly well described concept. I was, after all, trying to explain that my naysaying was not "referring to plank on frame", but rather based on a cold molded hull, designed by a fairly well known designer (Bruce Kirby) built by a fairly well known builder (Bent Jesperssen) and modified by someone who had a "better idea" than the designer and the builder.

Of course, I may completely mis-understand the why, but:

I understand the wikipedia definition... but as explained to me in the eighth grade, osmosis can be understood as: water moving from an area of high concentration through a membrane to an area of low concentration.

That understood... While I'll accept for the sake of the conversation that the FRP does not have cell membranes, it is a woven fiber. The gaps in fiberglass matting are far larger than the gaps in Gore Tex. In the use described, the gaps in the matrix are filled by epoxy, which we know will allow the passage of water.

So you have high concentration of water on the outside of the boat, with water "potential", as you described it (i.e. dry) inside the boat, or, more specifically, inside the glass layer, but outside the interior of the hull. The glass/epoxy matrix absorbs the water (I think) due to water pressure. Maybe that's not "really osmosis", but it does describe why a "wet" boat weighs more than a "dry" boat.

That water ends up between the glass and the wood. How is that different than wood just sitting in the water? Gosh, I miss the Chemist. This is where I fall back on empirical data. My empirical data tells me that on at least one boat, which had fiberglass over cold molding, water got in between the glass and the wood (osmosis? Crack in the layer? Poor workmanship by the glass/epoxy previous owner?) and the rot began.

I'll accept your argument that it wasn't osmosis (I did, after all, say "not always"). The 1980s arguments over "osmotic blistering" can still light up a yacht club bar. But I can tell you that whatever layer is put there will some day have dings/abrasions/microscopic cracks/misalignment of Jupiter with Mars as Venus is on the cusp of Pluto/a butterfly farted in Zimbabwe causing a chaos theory reaction which lead to the epoxy being mixed at a .9999999999999 to 1 ratio instead of a 1 to 1 ratio/whatever, and water will get in. I believe (but do not know) that this is more common below the waterline than on decks, mostly because I think decks dry out more, or because they don't have the pressure from sitting in the water, or whatever the highly scientific terms are which describe the differences between being below the true water line and above.

I know two things. The first is that the length plus two times the girth differential minus the freeboard plus the square root of the sail area all divided by 2.37 equals Eight Metres, and the second is that my bank account is much, much lighter due to a keel replacement job. Everything else is theory.

[rbgarr]

Steve Smith (of CPES) on the causes and treatment of blisters.

http://www.smithandcompany.org/GRP/GRP.html

[hm0316]

The failure of fiberglass sheathing is dependent upon several factors, including, most importantly, the original design and constuction of the hull and the glue used to attach the material. T When the L16 was originally built, it was, of course, not sheathed with fiberglass. The glue used was resorcinol and the laminations above and below the waterline have not failed after 60 years, except where there has been saturation through the end grain, which is very common due to original design and construction limitations. People have been trying to repair wooden boats with sheathing for a fairly long time. Many of these attempts have involved the L16, because it was laminated to start with and we can see what has worked and what has not. Attempting to "fix a leak" or make a hull "stronger" by applying mutiple layers of fiberglass around the hull will make a boat heavier and may slow a leak but it will allow the structure to continue to deteriorate and may accelerate that deterioration. A final layer of fiberglass properly applied with epoxy to a monocoque laminated wood hull should not hurt and may help by protecting against abrasion and helping to seal the end grain of the wood laminations. Beyond that, it is generally not a good idea.

hm0316

[Tom Robb]

IIRC, Googe Bros hold that one of the purposes of a layer of glass on a molded hull is to ensure a consistent thickness of epoxy on the outer surface of the hull. Too much is wasteful; too little increases vapor permeability as I understood it.

[seo]

Don.Z,
The eighth grade description of osmosis works all right as long as you're inside a plant or animal cell system. Move it to the wide world, and it describes all kinds of things, like evaporation, rain, waterfalls, etc, that are not osmosis.
I'm pretty sure "permeation" is what we're talking about, and I don't think that word has an alternate meaning that can confuse the issue.
As you very correctly point out, fiberglass is a fabric, very permeable. Plastic resin, either polyester or epoxy, when laid up with fiberglass, dynel, etc, makes a pretty impermeable "Shell Plating" material, as everything from welded steel to yak-hide is referred to in the ABS manual of construction.
Even when given a thick coating of gelcoat, I don't think FRP ever becomes "impermeable" the way that steel plate is, or that's my conclusion after looking at the results of some early and ill-advised experiments with building integral fuel tanks into FRP hulls as it's done in steel hulls.
Whether the FRP "plating" or the wood "plating" is more permeable isn't known, and isn't significant. As you point out, the FRP can get holes in it, and it's also logical that the reason that the hull was sheathed was that it was leaking, and leaks work both ways.
Well, anyway.
Yesterday I looked at the pictures on this site of the rebuild of a Luders 24 on Long Island. It was a remarkable repair, and a lovely outcome, but I do wonder what it cost. If that's what an owner wants, and they can afford it, good deal. But I don't think it's the only rational, ethical, moral, choice. This is a small pleasure boat, after all. Accepting the premise that there's no such thing as permanent, there's a lot of rational approaches.
Someone might decide to use the old hull as a plug, splash a mold off it, and build a new hull of FRP.
Or they might take off the hardware and interior joinerwork, and build a new cold-molded hull to put the old stuff in. That's what was done with the Herreshoff original "Bounty." The hull now going around under the name "Bounty" was built in the 60's in Nova Scotia, using the original rig, interior, deck fittings, etc. The original hull built in the 30's by the Quincy Adams yard was rebuilt by O. Lie-Nielsen and re-named "Poquita." I think she's out in California now, named "L. Francis Herreshoff."
Other's might choose to make a less expensive and less long-lived repair with FRP. I know of a 40's era hot-molded Rhodes 19 that was coming apart in much the same way that it appears L-16s do. The owner sheathed it with several layers of glass/polyester, and got another six years out of it. At that point the keel, floors, etc, had gotten REALLY rotten, to the point the centerboard trunk wasn't stable. So they peeled the wood out from the inside below the waterline, leaving the FRP sheathing, put in several more layers of FRP inside, so the centerboard trunk was now mounted directly on the FRP hull. The joint to the wood hull above the waterline was done with a combination of epoxy/glass gussets, or doublers, and a built-up FRP belt at the joint, which was pretty unobtrusive.
It worked all right, the boat didn't leak. I lost track of the boat some years later, and it was all right.
Was this an elegant work of art, suitable for the cover of Woodenboat Magazine. No, probably not. Was it a practical and economical way to extend the useful life a a nice little boat? I think so. The Rhodes had no particularly stunning pedigree or admiring throngs of afficionadoes waiting with wallets open to take it under their wing. The choice was to do an affordable repair that made her adequately strong to be safe, or to let the boat turn to mulch.

[seo]

Don.Z,
The eighth grade description of osmosis works all right as long as you're inside a plant or animal cell system. Move it to the wide world, and it describes all kinds of things, like evaporation, rain, waterfalls, etc, that are not osmosis.
I'm pretty sure "permeation" is what we're talking about, and I don't think that word has an alternate meaning that can confuse the issue.
As you very correctly point out, fiberglass is a fabric, very permeable. Plastic resin, either polyester or epoxy, when laid up with fiberglass, dynel, etc, makes a pretty impermeable "Shell Plating" material, as everything from welded steel to yak-hide is referred to in the ABS manual of construction.
Even when given a thick coating of gelcoat, I don't think FRP ever becomes "impermeable" the way that steel plate is, or that's my conclusion after looking at the results of some early and ill-advised experiments with building integral fuel tanks into FRP hulls as it's done in steel hulls.
Whether the FRP "plating" or the wood "plating" is more permeable isn't known, and isn't significant. As you point out, the FRP can get holes in it, and it's also logical that the reason that the hull was sheathed was that it was leaking, and leaks work both ways.
Well, anyway.
Yesterday I looked at the pictures on this site of the rebuild of a Luders 24 on Long Island. It was a remarkable repair, and a lovely outcome, but I do wonder what it cost. If that's what an owner wants, and they can afford it, good deal. But I don't think it's the only rational, ethical, moral, choice. This is a small pleasure boat, after all. Accepting the premise that there's no such thing as permanent, there's a lot of rational approaches.
Someone might decide to use the old hull as a plug, splash a mold off it, and build a new hull of FRP.
Or they might take off the hardware and interior joinerwork, and build a new cold-molded hull to put the old stuff in. That's what was done with the Herreshoff original "Bounty." The hull now going around under the name "Bounty" was built in the 60's in Nova Scotia, using the original rig, interior, deck fittings, etc. The original hull built in the 30's by the Quincy Adams yard was rebuilt by O. Lie-Nielsen and re-named "Poquita." I think she's out in California now, named "L. Francis Herreshoff."
Other's might choose to make a less expensive and less long-lived repair with FRP. I know of a 40's era hot-molded Rhodes 19 that was coming apart in much the same way that it appears L-16s do. The owner sheathed it with several layers of glass/polyester, and got another six years out of it. At that point the keel, floors, etc, had gotten REALLY rotten, to the point the centerboard trunk wasn't stable. So they peeled the wood out from the inside below the waterline, leaving the FRP sheathing, put in several more layers of FRP inside, so the centerboard trunk was now mounted directly on the FRP hull. The joint to the wood hull above the waterline was done with a combination of epoxy/glass gussets, or doublers, and a built-up FRP belt at the joint, which was pretty unobtrusive.
It worked all right, the boat didn't leak. I lost track of the boat some years later, and it was all right.
Was this an elegant work of art, suitable for the cover of Woodenboat Magazine. No, probably not. Was it a practical and economical way to extend the useful life a a nice little boat? I think so. The Rhodes had no particularly stunning pedigree or admiring throngs of afficionadoes waiting with wallets open to take it under their wing. The choice was to do an affordable repair that made her adequately strong to be safe, or to let the boat turn to mulch.