Page 1 of 2 12 LastLast
Results 1 to 35 of 42

Thread: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

  1. #1
    Join Date
    Aug 2015
    Location
    Canberra, Australia
    Posts
    140

    Default Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    So,

    A few months ago, my partner and I became the new owners of a 36' Sparkman Stephens One Tonner named Kishmul. Built in 1971 in NZ, cold-molded from triple-diagonal heart kauri. Thread here:

    http://forum.woodenboat.com/showthre...at-Have-I-Done

    Not unusually for cold-molded boats of that era (I'm told), she has never been sheathed in glass - only painted with 2-pack. As far as a full percussion tap-test survey can reveal, the hull is entirely sound, with one possible trouble spot that will be the subject of a future thread. I think she's copper fastened but I'm not sure what she was glued with - given a launch date of 1971, I imagine probably resorcinol.

    Kishmul has now been pulled out of the water and will stored on the hard for a year or two for various reasons. From the day we had her surveyed, I thought she would benefit from sheathing. The surveyor, an expert in this type of construction, agreed that this would extend her life and simplify maintenance considerably. There are also cosmetic considerations: there is some fastener print-through and some movement along the seams of the top layer of veneers, and I'm not above admitting that I'd like to restore her to a yacht finish (she's no workboat). In any case, I am increasingly of the view that it would be a shame to waste the 1-2 years' drying out, and that I should try to sheathe her before she goes back in, while the hull is at an exceptionally low moisture content and while I have access to her for longer periods without paying marina hardstand rates.

    I'm aware that sheathing is a controversial topic on the Forum, but keep in mind that she is not carvel. No caulking, and with a monocoque structure that is intended to be fully watertight. Perhaps as an offshore racer, sheathing was originally omitted as a weight-saving measure or due to the relative newness of resins, but it could just as easily have been added. I think I recall that JohnB's beautiful Riada, also an NZ boat from a similar era, is constructed like this - cold-molded with a light external cloth.

    The ethics of sheathing aside, my question is this: what additional benefits does cloth (as opposed to the epoxy it is set in) offer in this application? The issue is not one of strength or stiffness - I'm simply hoping to seal the hull. Does the cloth add any waterproofing? Intuitively, I would not think so since no cloth is, by itself, waterproof, but I'm keen to hear if I'm missing something. Perhaps the huge amounts of resin sucked up by the cloth helps to make a thicker and more impermeable layer? Clearly, plenty of small ply boats are treated only with resin, including my own GIS, but I can't say I've heard of coating a larger boat with epoxy but not cloth.

    Why entertain skipping the cloth, then? Well, basically because adding cloth will be immensely more time-consuming and expensive (and heavier). Given my own amateur skills and pace, sheathing this complex and very curvy IOR-type hull with cloth could (at a guess) require 200-400 hours of labour, mostly due to the fact that it will require a soul-destroying quantity of fairing, which I have some experience with. It might also require some professional assistance, which is expensive. Conversely, doing some light fairing of the veneers and rolling on 4-8 coats of epoxy (or even more) would, at a guess, be more like 100 hours.

    Keen to hear some opinions from those more knowledgeable than myself. I'm young and stupid - please educate me.
    Sailing - the fine art of getting wet and becoming ill while slowly going nowhere at great expense.

    - Henry Beard

  2. #2
    Join Date
    Apr 1999
    Location
    West Boothbay Harbor, Maine
    Posts
    23,294

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    Our boat (much smaller) is epoxy and cloth sheathed triple diagonal also. The layers and interior are epoxied as well, so I wonder if there are other issues to consider as well as the cloth. How about contacting a widely, professionally, experienced source like Gougeon about what you envision? https://www.westsystem.com/contact/need-help/
    "It's a pirate's life for me. Savvy??"

  3. #3
    Join Date
    Dec 2003
    Location
    Portland, Oregon
    Posts
    47,330

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    Quote Originally Posted by Brightwater View Post
    So,

    A few months ago, my partner and I became the new owners of a 36' Sparkman Stephens One Tonner named Kishmul. Built in 1971 in NZ, cold-molded from triple-diagonal heart kauri. Thread here:

    http://forum.woodenboat.com/showthre...at-Have-I-Done

    Not unusually for cold-molded boats of that era (I'm told), she has never been sheathed in glass - only painted with 2-pack. As far as a full percussion tap-test survey can reveal, the hull is entirely sound, with one possible trouble spot that will be the subject of a future thread. I think she's copper fastened but I'm not sure what she was glued with - given a launch date of 1971, I imagine probably resorcinol.

    Kishmul has now been pulled out of the water and will stored on the hard for a year or two for various reasons. From the day we had her surveyed, I thought she would benefit from sheathing. The surveyor, an expert in this type of construction, agreed that this would extend her life and simplify maintenance considerably. There are also cosmetic considerations: there is some fastener print-through and some movement along the seams of the top layer of veneers, and I'm not above admitting that I'd like to restore her to a yacht finish (she's no workboat). In any case, I am increasingly of the view that it would be a shame to waste the 1-2 years' drying out, and that I should try to sheathe her before she goes back in, while the hull is at an exceptionally low moisture content and while I have access to her for longer periods without paying marina hardstand rates.

    I'm aware that sheathing is a controversial topic on the Forum, but keep in mind that she is not carvel. No caulking, and with a monocoque structure that is intended to be fully watertight. Perhaps as an offshore racer, sheathing was originally omitted as a weight-saving measure or due to the relative newness of resins, but it could just as easily have been added. I think I recall that JohnB's beautiful Riada, also an NZ boat from a similar era, is constructed like this - cold-molded with a light external cloth.

    The ethics of sheathing aside, my question is this: what additional benefits does cloth (as opposed to the epoxy it is set in) offer in this application? The issue is not one of strength or stiffness - I'm simply hoping to seal the hull. Does the cloth add any waterproofing? Intuitively, I would not think so since no cloth is, by itself, waterproof, but I'm keen to hear if I'm missing something. Perhaps the huge amounts of resin sucked up by the cloth helps to make a thicker and more impermeable layer? Clearly, plenty of small ply boats are treated only with resin, including my own GIS, but I can't say I've heard of coating a larger boat with epoxy but not cloth.

    Why entertain skipping the cloth, then? Well, basically because adding cloth will be immensely more time-consuming and expensive (and heavier). Given my own amateur skills and pace, sheathing this complex and very curvy IOR-type hull with cloth could (at a guess) require 200-400 hours of labour, mostly due to the fact that it will require a soul-destroying quantity of fairing, which I have some experience with. It might also require some professional assistance, which is expensive. Conversely, doing some light fairing of the veneers and rolling on 4-8 coats of epoxy (or even more) would, at a guess, be more like 100 hours.

    Keen to hear some opinions from those more knowledgeable than myself. I'm young and stupid - please educate me.
    There you have the crux of it (though a single layer of glass won't capture 'huge' amounts of resin - but huge enough when it comes time to write the check, eh?). The research West System has done shows that epoxy... or epoxy+glass matrix... is not totally waterproof, but that the thicker the film... the more closely it resembles waterproof. Add in the fairing effect, and the stabilizing effect, and a bit of added hull strength... and I see no reason (beyond the pocketbook effect) not to sheath the exterior.

    I do hope you'll document the process - for posterity.
    David G
    Harbor Woodworks
    http://www.harborwoodworking.com/boat.html

    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

  4. #4
    Join Date
    Jun 2017
    Location
    Nazaré, Portugal
    Posts
    476

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    I certainly can't call me an expert, but ...

    Fibreglass on top of the ply gives a lot extra abrasion-resistance and protection from damage. One example: mates of mine had just launched their cold molded plywood sailing-boat a few weeks earlier after spending years building her, when a young boy playing with his fishing-rod on the shore got something wrong with his throwing-technique and the lead attached to his line hit the hull and caused damage to the ply. They were really shocked to see what kind of damage a little bit of lead was capable of doing to their plywood. They postponed their cruise around the world, the boat came out again, and they applied 2 layers of fibreglass with epoxy.

    Your boat is from 1971 and obviously was doing fine. Going on a long cruise where Marinas can become sparse and fishing-ports more of an option is something completely different than keeping your boat in a well protected space and nicely cushioned.

    I think this is a question you've got to ask yourself what you would like to do with your boat.
    fair winds, Dody

    "They did not know it was impossible so they did it" - Mark Twain

    http://forum.woodenboat.com/showthre...h-Tonga/page12

  5. #5
    Join Date
    Oct 2008
    Location
    Walney, near Cumbria UK
    Posts
    39,721

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    Glass sheathing does add abrasion resistance, helps stop the epoxy cracking along the wood grain and stops the planking glue lines printing through the paint.
    It really is quite difficult to build an ugly wooden boat.

    The power of the web: Anyone can post anything on the web
    The weakness of the web: Anyone can post anything on the web.

  6. #6
    Join Date
    Jan 2016
    Location
    Bolton, Massachusetts, USA
    Posts
    91

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    At the risk of further complicating your decision process, have you considered Xynole (polyester) fabric in lieu of fiberglass. (http://www.raka.com/xynole.html) I'm building a small cold-molded sailboat and have been considering that fabric for the sheathing. It is reported to be more impact and abrasion resistant (than glass) though I have seen no actual data to support this claim. I used this cloth set in epoxy to line the interior portions of the centerboard trunk. It handles nicely, though it does absorb a lot of resin.

    My personal preference would be to sheath your beautiful boat in something (cloth + epoxy resin). Good luck.

  7. #7
    Join Date
    Jun 2000
    Location
    Madison Wisconsin
    Posts
    8,953

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    The problem with Dynel or Xynole is always that they tend to soak up a lot more resin, which can fairly substantially increase both weight and resin cost. They are more abrasion resistant than fiberglass, though their impact resistance increase needs to be explained carefully. No thin sheathing layer of any fabric is going to make a big difference in impact resistance. It is mostly a function of the hull's structure under the sheathing and its strength, or lack of it. Where the non-fiberglass fabrics (Kevlar, Xynole, Dynel, polypropylene, nylon, etc.) increase impact resistance is a matter of holding the hull together after it has been holed, for example. When the fiberglass has ruptured, since it is more brittle and rigid, these other fabrics with higher tear strength or higher elasticity may hold the pieces together better. This may or may not mean that the boat is still watertight.

    If you intend to epoxy coat the boat and yield a smooth surface once finish sanded and made ready for paint, you will probably need to roll on somewhere in the neighborhood of four to six thin, even coats of resin (yielding the desired 10 mils or so of coating thickness as a good moisture barrier) then you probably have enough resin thickness to float a light layer of fiberglass cloth in there anyway with no increase in the amount of resin needed.

  8. #8
    Join Date
    Dec 2003
    Location
    Sound Beach, NY
    Posts
    3,449

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    FG boats use "Barrier Coat" after treating for blisters. I haven't used it. My Dad did, but both he and his boat have sailed on.

  9. #9
    Join Date
    Apr 2010
    Location
    South Australia and Tasmania
    Posts
    14,574

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    If you are worried about the weight, which I don't think you should be, you could just glass below the waterline, where the additional weight will matter not a jot. But what's the total weight going to be anyway? Less than say 50 kg max? It's nothing.

  10. #10
    Join Date
    Jun 2017
    Location
    Nazaré, Portugal
    Posts
    476

    Default

    Quote Originally Posted by johngsandusky View Post
    FG boats use "Barrier Coat" after treating for blisters. I haven't used it. My Dad did, but both he and his boat have sailed on.
    But this is with Polyester, as Polyester has no, or hardly any, water-tightening qualities. In the production-process of fibreglass-boats, after treating the form so the boat is capable to pop out, gelcoat is first applied in the form and then the fibreglass with Polyester. If the gelcoat is of minor quality water can get through and soak into the fibreglass (again, we're talking Polyester) and cause osmosis - which are the blisters you are talking of.

    Once you take the gelcoat off to sort out the blisters, of course you need to apply a barrier-coat to prevent the same thing from happening again!

    Sent from my SM-G900FD using Tapatalk
    fair winds, Dody

    "They did not know it was impossible so they did it" - Mark Twain

    http://forum.woodenboat.com/showthre...h-Tonga/page12

  11. #11
    Join Date
    Jun 2000
    Location
    Madison Wisconsin
    Posts
    8,953

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    Barrier coating is a multi-layer mixture of epoxy resin and tiny aluminum flakes, and it will usually take about six or seven thin rolled-on coats if you intend to later sand it smooth and leave enough on the boat to do the job. The principle sounds awfully simple, but actually works. Any moisture penetrating the coating literally has to zig-zag around the aluminum flakes to penetrate - and that actually does make it more moisture resistant than plain resin, gelcoat, paint, etc. You start with a neat coat of epoxy/hardener, followed by several coats with the powder mixed into the resin. It is not thick like fairing compounds and basically behaves just about the same as plain epoxy during the application. New coats are applied as soon as the previous one is hard enough that you won't disturb it. Once fully cured (about a week) you can sand it smooth. It ends up being a dull grey color.

    If you intend to paint it with topside paint (rather than some kind of bottom paint) your resin application should also finish with a coat or two of plain resin/hardener after all the aluminum coats. The reason for this is that like any filler, when you sand the surface smooth after the resin cures, you expose tiny bits of cut-off filler particles. Aluminum particles will start to oxidize immediately. When you try to paint over them, the paint may not stick and you are very likely to have a surface with thousands of tiny pinholes in your paint job. They probably won't hurt anything, but they do show and aren't very attractive. I even had one boat which was two-tone Brightside over sanded barrier coating and one color pinholed, but the other didn't. Now I would always top-coat the aluminum with plain resin to avoid that scenario.

  12. #12
    Join Date
    Aug 2015
    Location
    Canberra, Australia
    Posts
    140

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    Thanks for the replies, everyone.

    My take on the issue of impact resistance was the same as Todd's - it's unlikely to make much difference unless the sheathing is very heavy, which I'm not keen on. The boat was designed as an ocean racer (and completed quite a few ocean races) so I have few doubts about the hull's strength. As well as the veneers, which I would guess to be something over an inch in thickness (never taken a core sample), the interior is also covered in numerous closely spaced 'ribs' (for ignorance of the correct term). However, the point is taken that some of the non-glass fabrics might hold the boat together and give you a little more time to limp to port if you hit something really hard.

    I definitely have considered fabrics other than fibreglass, and I wouldn't rule those out if I were to use a cloth. My issue is not so much weight - it's that using a fabric is going to make the job immensely more difficult, due to the following:

    1. I'd need to strip a lot of hardware, and perhaps even drop the keel and wrap underneath it to do a proper job (the keel is about 2.5 tons so I really want to avoid that if I can);
    2. I'd need to fair the fabric into the hull-deck corner, and around the transom;
    3. I'd have to work overhead and at a height (the draft is 6'), probably applying the fabric to a wet layer of epoxy so it sticks;
    4. It will (I believe) massively increase the amount of fairing needed, because (especially for a non-professional) few glassing jobs that don't use a mold come out perfect. Possibly, some of the finer-weave and more 'drape-able' fabrics like Xynole would be easier to do a good job with, especially if I used peel ply?

    Strength issues aside, it sounds like the consensus is that cloth may offer some benefits in terms of waterproofing, ie. by preventing cracking and print-through and increasing the overall thickness of the sheath. However, this 'barrier coat' that Johng and Todd mention sounds like an interesting possibility. Todd, is there any chance you could point me to further info on that coating technique or a link to the right aluminium product to be added to epoxy? Have you heard of it being applied to a wooden boat before? Would you expect to see veneer print-through, if no cloth is used?

    I also wonder if G-flex might be a good epoxy option to avoid cracking. Has anyone ever heard of G-flex being used for sheathing or coating?
    Sailing - the fine art of getting wet and becoming ill while slowly going nowhere at great expense.

    - Henry Beard

  13. #13
    Join Date
    Aug 2000
    Location
    Auckland ,N.Z.
    Posts
    24,661

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    I was looking at photos of Kishmul in her new yard the other day as it happens. I didn't realise she had that trim tab.
    As to sheathing , I dunno. Some do some don't. Riada does from new but many Townsons of similar age , such as Des Townsons own boat Talent ,do not.
    How do you even do it I wonder, you'd wood her for adhesion and then you'd lose that few decades of fairing. By wooding her you expose her to excessive drying out which could be quite bad for a resorcinol hull. ( thinking out loud. )
    Printing is no big deal, there will often be some of that on the sun exposed side ( in a berth say).
    No I'm not sure .

  14. #14
    Join Date
    Aug 2015
    Location
    Canberra, Australia
    Posts
    140

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    Hi John,

    Someone’s found her in her new location, huh? I’m impressed, given how out of the way it is. The trim tab is a charming anachronism - not sure the old owner ever used it but might be fun to see whether it yields any benefit.

    Re drying, I would only wood her shortly before applying sheathing, so she wouldn’t be exposed for long. Do you think removing paint with a heat gun and scraper is likely to make her ‘unfair’?

    Part of the reason I’m considering sheathing is that there is a trouble spot at a floor timber around a cluster of copper plank fasteners where there is a small pocket of soft wood. I’m not sure whether this is due to the fasteners creating some kind of conditions that are friendly to rot, or whether it’s due to electrolysis. Will make a thread on this question separately. Either way, I’d be happier if the boat’s planking were ‘dry’ (clearly this has to be combined with removing all soft wood and addressing any electrolytic problems).
    Sailing - the fine art of getting wet and becoming ill while slowly going nowhere at great expense.

    - Henry Beard

  15. #15
    Join Date
    Jun 2000
    Location
    Madison Wisconsin
    Posts
    8,953

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    Gougeon Brothers has a small booklet on barrier coating, mostly for fiberglass blister repair. I can't remember off the top of my head if there is anything in their book about it. I have not seen it done to a wooden hull that I can remember. If it made a dramatic improvement over typical epoxy coating or fabric sheathing I think we would have heard a lot about it, which hasn't happened. I can't imagine trying to sheathe a hull with something like G-Flex.

  16. #16
    Join Date
    Feb 2006
    Location
    NZ
    Posts
    2,167

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    The short answer is dont bother unless you like spending money. 1971 and in good nick? I think thats your answer.

    Kauri especially heart is the worlds finest boat building timber, its not unusual to find boats that are still going after 100 years. You have a treasure that will not likely be repeated, take care of it and think very carefully before some Johnny come lately aussie surveyor gives advice on how to look after it. The 3 skin boats from this era are the highpoint of timber construction in NZ, you wont find better.
    whatever rocks your boat

  17. #17
    Join Date
    Aug 2015
    Location
    Canberra, Australia
    Posts
    140

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    Quote Originally Posted by Paul G. View Post
    The short answer is dont bother unless you like spending money. 1971 and in good nick? I think thats your answer.

    Kauri especially heart is the worlds finest boat building timber, its not unusual to find boats that are still going after 100 years. You have a treasure that will not likely be repeated, take care of it and think very carefully before some Johnny come lately aussie surveyor gives advice on how to look after it. The 3 skin boats from this era are the highpoint of timber construction in NZ, you wont find better.
    Paul,

    I appreciate your kind words on the boat - she is indeed unique and I intend to treat her with respect. I should, however, defend my surveyor’s honour by pointing out that he’s a Kiwi, and has built a few cold molded hulls himself! I would certainly never dream of sheathing a carvel boat, but it would be rare to find a cold molded boat built today that isn’t sheathed.

    That said, I see your point in terms of not fixing what ain’t broken. I won’t make a final decision until I figure out what’s causing the soft wood - I’m enlisting the help of some NZ shipwrights for that and will put these questions to them.
    Sailing - the fine art of getting wet and becoming ill while slowly going nowhere at great expense.

    - Henry Beard

  18. #18
    Join Date
    Apr 2009
    Location
    Mountain lakes of Vermont
    Posts
    10,556

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    I can't add anything to what's already been said about the sheathing.
    I'm wondering about the comment that she is "copper fastened".
    Does the boat have frames that the wood hull is fastened to? I thought cold molded boats usually don't a have a single screw in them.
    I was born on a wooden boat that I built myself.

  19. #19
    Join Date
    Aug 2000
    Location
    Auckland ,N.Z.
    Posts
    24,661

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    Its extremely probable that she has bronze screws but there would be copper staples used as part of the cold moulding process.

  20. #20
    Join Date
    Apr 1999
    Location
    West Boothbay Harbor, Maine
    Posts
    23,294

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    Our triple-skinned, epoxy/clothed boat has bronze screws into the sawn frames that have started to show print-through, just a tiny bit. Only on the starboard topsides though, interestingly.
    "It's a pirate's life for me. Savvy??"

  21. #21
    Join Date
    Oct 2008
    Location
    Walney, near Cumbria UK
    Posts
    39,721

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    Quote Originally Posted by rbgarr View Post
    Our triple-skinned, epoxy/clothed boat has bronze screws into the sawn frames that have started to show print-through, just a tiny bit. Only on the starboard topsides though, interestingly.
    How is she moored. Always with the same one side in the sun?
    It really is quite difficult to build an ugly wooden boat.

    The power of the web: Anyone can post anything on the web
    The weakness of the web: Anyone can post anything on the web.

  22. #22
    Join Date
    Apr 1999
    Location
    West Boothbay Harbor, Maine
    Posts
    23,294

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    Quote Originally Posted by Peerie Maa View Post
    How is she moored. Always with the same one side in the sun?
    Pretty much port side toward the sun.
    "It's a pirate's life for me. Savvy??"

  23. #23
    Join Date
    Feb 2000
    Location
    San Francisco Bay
    Posts
    11,546

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    Quote Originally Posted by Paul G. View Post
    The short answer is dont bother unless you like spending money. 1971 and in good nick? I think thats your answer.

    Kauri especially heart is the worlds finest boat building timber, its not unusual to find boats that are still going after 100 years. You have a treasure that will not likely be repeated, take care of it and think very carefully before some Johnny come lately aussie surveyor gives advice on how to look after it. The 3 skin boats from this era are the highpoint of timber construction in NZ, you wont find better.
    What Paul said! With all due respect to your surveyor, the boat may well be older than he is. In any event, it's quite possible he doesn't have "hands on" building experience with this building method.

    A "cold molded" hull is one in which, as some have described, veneers are stapled one on top of the other with adhesive, often epoxy resin, between the veneers. This molding is done over a "plug" or armature which is not part of the finished boat which, in most cases, being of monocoque construction, will have no frames and only bulkheads. The veneers in this construction method (often called WEST System epoxy cold-molding) are quite thin and, where the veneers are of softwood species, susceptible to surface damage, particularly where the hull might be finished bright. A lot of the early "cold molded" boats were planked with red cedar, which is easily dented with a fingernail and for this reason were sheathed in fiberglass. As I recall, having watched them built, the first of these sort of epoxy "cold molded" hulls were built in Alameda, CA in the early 1970's, to Gary Mull's designs under the IOR.

    For many, many years before, "multiple planked" hulls were built "on frame" in the same fashion as traditionally framed and planked hulls, running planks at alternate angles, with two, three, or even more layers of plank stacked one upon the other. In this construction method, the planks were fastened with traditional fasteners, generally screws, often driven from both the outside and the inside of the hull. The exterior-most planking was run parallel to the baseline, as in regular carvel construction, with the planking in between run at alternately opposing angles. In the earlier builds, muslin soaked in heavy-cut shellac or white lead paint was used between the planking layers to ensure water-tightness. This construction method was favored for lightness and the ability to resist the usual "opening up" when boats were dry stored. (This construction method was often employed in lifeboat construction.) L. Francis Herreshoff specified this construction method in a number of his designs.

    For whatever reasons, this later layered-planking construction was always particularly popular with NZ builders who raised it to a high art. Many of their boats built in this fashion of kauri wood have lasted for remarkable lengths of time. I was familiar with one LFH Araminta sloop (one of LFH's very last authorized builds... he designed the sloop rig as an alterative to the original ketch rig.) built of kauri in NZ in the early 1970's. She was a beautiful boat to be sure.

    In this layered planking method, the planking was generally thicker than the plywood-thin veneers used in the "cold molded" boats. The planking in the multi-layered construction had its grain running the same as any traditional carvel planking and the planks were generally of uniform thickness. Because the planking was thicker, and was generally of standard planking stock species which resisted impacts well, they were not sheathed in fiberlass or epoxy resin, as far as I know. Kauri is, as I expect you know, damn near bullet-proof in terms of its hardness.

    If your hull is built on traditional framing and is serving its purpose well at the moment, I would offer for your consideration the maxim, "If it ain't broke, don't fix it!"

    Sheathing a hull is a huge undertaking. (Yes, to be done correctly, the ballast must be dropped and you pretty much have to turn the hull upside down to accomplish the task with any measure of fairness.)

    If you are laboring under the misapprehension that sheathing a hull in cloth and resin is going to make it "water-proof," disabuse yourself of that foolishness. You can read many discussions about the myth of "encapsulation" in this forum. (Fortunately, most experienced boat workers have figured it out by now. It was a big fad for quite some time.) If your boat is truly a "yacht," then treat her like one: Preserve and maintain her in just the way her architect designed her. The odds are overwhelming that he knew better and more than your surveyor and certainly more than you. Fibreglass sheathing was well known and widely practiced at the time your boat was built, most frequently on cheap plywood production boats. If the designer thought it needed sheathing, he'd have specified it.

  24. #24
    Join Date
    Aug 2000
    Location
    Auckland ,N.Z.
    Posts
    24,661

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    Just a bit to add, The reason that cold moulding was picked up and developed / used extensively here in NZ was that earlier boats like our old Waione, boats from say late 1800's or so, were built multi skin but mechanically fastened. Typically 2 and 3 skins. They were influenced by lifeboat construction techniques.
    So if you went to a good yard for a yacht in say 1900, they would build it that way by preference. Then of course you had say 50 or 70 years of boatbuilders brought through from apprenticeship to business owners and yards in their own right. When reliable glues burst on the scene it was a natural progression for those people to use the same method of building a monocoque hull but adapt it from copper rivets and roves to glue.

    something from our sponsor...



    and one I like . Prize , a 1923 43 footer by Charles Bailey in build. many of those longitudinals are stringers ( Clamp etc), some are temporary for the skinning, as are the frames. Note also the keelbolts ready for the pour in situ. One of the jobs we've all had to do at some stage is rake out all the dross off the top of the keel and re bed with high density filler.





    and just one small point , kauri isn't very hard . Its quite like teak , very easy to cut generally and you can bruise it / dent it by being careless. There's just some sort of natural rot killer in it.
    And its a pleasure to work with , looks like refracted gold with a polish or varnish, smells like honey, doesn't break out, lasts a few lifetimes and is now expensive to buy. Which is why hoarders like me see a 2 x 4 or old weatherboard pulled out of an an old house and snaffle it for personal stock despite nail holes or other flaws.
    Last edited by John B; 07-12-2018 at 10:49 PM.

  25. #25
    Join Date
    Jul 2011
    Location
    Lindstrom, MN
    Posts
    2,059

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    I would lean toward the ain't broke don' fix it side. Thin glass sheathing can be cut fairly easily. Once the sheathing is cut, the water can get behind it and cause a lot of trouble. A 37' boat gets into the irresistible force and immovable object territory, and putting 0.005" of fiberglass in between isn't going to fare well. If I were to sheath it, I would use several layers of heavy cloth.

    There are some threads with a lot of information on sheathing materials and abrasion resistance that might help with the decisions.
    http://forum.woodenboat.com/showthre...ion-Resistance
    http://forum.woodenboat.com/showthre...olyester-cloth

    Abrasion resistant cloths like Dynel, Vectra and Xynole are bulkier than glass cloth so they use a lot of resin for the weight of the cloth.
    Management is the art of counting beans. Leadership is the art of making every being count. --Joe Finch

  26. #26
    Join Date
    Mar 2011
    Location
    Auckland, NZ
    Posts
    92

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    A kiwi boat builder I know and respect has a 40+ year old 3 skin resorcinol glued kauri 45 foot motor sailor. The planking was in perfect condition, however he has recently sheathed ( 6 oz glass cloth /epoxy) the topsides only His reasoning was to reduce the frequency of the need to paint the topsides. The unsheathed topsides previously needed painting in single pot every say 5 years whereas two pot would be good for 20+ years. The sheathing was a huge amount of work and the payback will be very long.

  27. #27
    Join Date
    Nov 2006
    Location
    Alameda, CA
    Posts
    10,560

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    Quote Originally Posted by Bob Cleek View Post
    What Paul said! With all due respect to your surveyor, the boat may well be older than he is. In any event, it's quite possible he doesn't have "hands on" building experience with this building method.

    A "cold molded" hull is one in which, as some have described, veneers are stapled one on top of the other with adhesive, often epoxy resin, between the veneers. This molding is done over a "plug" or armature which is not part of the finished boat which, in most cases, being of monocoque construction, will have no frames and only bulkheads. The veneers in this construction method (often called WEST System epoxy cold-molding) are quite thin and, where the veneers are of softwood species, susceptible to surface damage, particularly where the hull might be finished bright. A lot of the early "cold molded" boats were planked with red cedar, which is easily dented with a fingernail and for this reason were sheathed in fiberglass. As I recall, having watched them built, the first of these sort of epoxy "cold molded" hulls were built in Alameda, CA in the early 1970's, to Gary Mull's designs under the IOR.

    For many, many years before, "multiple planked" hulls were built "on frame" in the same fashion as traditionally framed and planked hulls, running planks at alternate angles, with two, three, or even more layers of plank stacked one upon the other. In this construction method, the planks were fastened with traditional fasteners, generally screws, often driven from both the outside and the inside of the hull. The exterior-most planking was run parallel to the baseline, as in regular carvel construction, with the planking in between run at alternately opposing angles. In the earlier builds, muslin soaked in heavy-cut shellac or white lead paint was used between the planking layers to ensure water-tightness. This construction method was favored for lightness and the ability to resist the usual "opening up" when boats were dry stored. (This construction method was often employed in lifeboat construction.) L. Francis Herreshoff specified this construction method in a number of his designs.

    For whatever reasons, this later layered-planking construction was always particularly popular with NZ builders who raised it to a high art. Many of their boats built in this fashion of kauri wood have lasted for remarkable lengths of time. I was familiar with one LFH Araminta sloop (one of LFH's very last authorized builds... he designed the sloop rig as an alterative to the original ketch rig.) built of kauri in NZ in the early 1970's. She was a beautiful boat to be sure.

    In this layered planking method, the planking was generally thicker than the plywood-thin veneers used in the "cold molded" boats. The planking in the multi-layered construction had its grain running the same as any traditional carvel planking and the planks were generally of uniform thickness. Because the planking was thicker, and was generally of standard planking stock species which resisted impacts well, they were not sheathed in fiberlass or epoxy resin, as far as I know. Kauri is, as I expect you know, damn near bullet-proof in terms of its hardness.

    If your hull is built on traditional framing and is serving its purpose well at the moment, I would offer for your consideration the maxim, "If it ain't broke, don't fix it!"

    Sheathing a hull is a huge undertaking. (Yes, to be done correctly, the ballast must be dropped and you pretty much have to turn the hull upside down to accomplish the task with any measure of fairness.)

    If you are laboring under the misapprehension that sheathing a hull in cloth and resin is going to make it "water-proof," disabuse yourself of that foolishness. You can read many discussions about the myth of "encapsulation" in this forum. (Fortunately, most experienced boat workers have figured it out by now. It was a big fad for quite some time.) If your boat is truly a "yacht," then treat her like one: Preserve and maintain her in just the way her architect designed her. The odds are overwhelming that he knew better and more than your surveyor and certainly more than you. Fibreglass sheathing was well known and widely practiced at the time your boat was built, most frequently on cheap plywood production boats. If the designer thought it needed sheathing, he'd have specified it.
    Bob as usual is correct with his information and his sage advice. My 1967 Gary Mull sloop was the psuedo strip plank/cold molded prototype in this construction method with her sisters made by Hank Easom in even more so with a more complete cold molding process. Boat builders all began to use the method going forward where the kiwis perfected it to a high art. As a side note, the boats that Hank made have had some minor sheathing and epoxy to fair the hulls without going overboard as well as all had their keels redone or addressed. Not much more has been done and they all are in great condition after 50 plus years. Undoubtedly - there will some fiberglass and epoxy around the keel joint anyway. I imagine this is going to be some simple fairing project from the fill from the keel joint and spanning a little over the hull to create a nice flow.

    As you hit this project - I would check the keel bolts. I am guessing they are stainless J-bolts which hook into the leaded keel and thread up through the keelson. You should address this as you restore yours. Doing a hull and not checking the bolts is not advised as you may be back sooner than you think or even loose the boat entirely. Looking at the nuts and the first several mm of the thread would mean you missed a lot. My boat appeared normaland good and then I managed to suck up one with a shop vac while cleaning and reading to paint the bilge. Rather than cut the keel off and redrill or recast the keel entirely, I sistered more the bolts in with silicon bronze. Something you should consider too and if done with care, an inexpensive proposition.

    Here is a plug pounded into the keel bolt hole after I sucked it out. Quite a fright to see water bubble up 3 meters high and in such high volume from the void.

    Last edited by Ted Hoppe; 07-13-2018 at 02:24 AM.
    Be wary of your critics, at peace with your decisions, and work hard to be a better man.

  28. #28
    Join Date
    Jan 2016
    Location
    Auckland New Zealand
    Posts
    3

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    Kishmul was built by Brin for Ted Buchanan.
    When first launched she swelled and some of her outer skin cupped and popped so Ted returned her to Brin with a bit of a moan about the state of the top sides.Brin promptly had her resanded and handed her back to the owner “there you go all sorted”.
    From memory she was chartered by the Swedish for the 1971 One Ton Cup?
    I nearly purchased her many many moons ago and she was sound then but in need of a major birthday which she obviously received and promptly sat on the market for yonks so it will be bloody great to see her being used.
    Her sister Young Nick may well be sheathed but that was done from birth.
    I would be very cautious about letting her stand and drying for any considerable time.
    Effectively she is what I call a “wet” hull and she has always been so.
    Sheathing her for cosmetic purposes with light weight cloth is not in my opinion a prudent path to follow.
    Kishmul is a earlier crossover multi skin build , ie bent frames close centred with heavy longitudinal deck shelves and stringers, strong as the proverbial and as your survey showed still in rude health after all these years.
    As others have stated to properly skin her in either epoxy or polyester you would need to go quite heavy weight or multilayered to achieve a durable result and all the existing movement in the outer skin issues will need to be addressed first and then you face the many challenges of successfully marrying differential materials.
    Also how do you propose dealing with the keel hull joint as it is best to separate and glass right through rather than encapsulate the lead.
    Better off spending your loot on quality sails and cruising around our beautiful coast rather than stuck in a shed covered in epoxy imho.
    Also remember to frequently "turn "your moored timber yacht so the sun does not bake the one side only.
    Last edited by Priscilla; 07-13-2018 at 03:30 AM.

  29. #29
    Join Date
    Aug 2017
    Location
    Melb, Vic, Aus
    Posts
    177

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    Quote Originally Posted by Priscilla View Post
    Kishmul was built by Brin for Ted Buchanan.
    When first launched she swelled and some of her outer skin cupped and popped so Ted returned her to Brin with a bit of a moan about the state of the top sides.Brin promptly had her resanded and handed her back to the owner “there you go all sorted”.
    From memory she was chartered by the Swedish for the 1971 One Ton Cup?
    I nearly purchased her many many moons ago and she was sound then but in need of a major birthday which she obviously received and promptly sat on the market for yonks so it will be bloody great to see her being used.
    Her sister Young Nick may well be sheathed but that was done from birth.
    I would be very cautious about letting her stand and drying for any considerable time.
    Effectively she is what I call a “wet” hull and she has always been so.

    Sheathing her for cosmetic purposes with light weight cloth is not in my opinion a prudent path to follow.
    Kishmul is a earlier crossover multi skin build , ie bent frames close centred with heavy longitudinal deck shelves and stringers, strong as the proverbial and as your survey showed still in rude health after all these years.
    As others have stated to properly skin her in either epoxy or polyester you would need to go quite heavy weight or multilayered to achieve a durable result and all the existing movement in the outer skin issues will need to be addressed first and then you face the many challenges of successfully marrying differential materials.
    Also how do you propose dealing with the keel hull joint as it is best to separate and glass right through rather than encapsulate the lead.
    Better off spending your loot on quality sails and cruising around our beautiful coast rather than stuck in a shed covered in epoxy imho.
    Also remember to frequently "turn "your moored timber yacht so the sun does not bake the one side only.
    +1.

  30. #30
    Join Date
    Aug 2015
    Location
    Canberra, Australia
    Posts
    140

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    Fair points, all, and food for thought. Thank you for the detailed responses, and for some history of the boat of which I was not aware! I won’t enter into sheathing lightly. I’ll discuss it with some ‘old school’ NZ boatbuilders to whom I have been referred (operating out of Half Moon Bay) and get their take on it. I’ll update the thread as that progresses.

    Amazes me how much NZ boaties seem to know about NZ boats, it seems like a very tight-knit scene compared to Australia. Or maybe Kishmul is better known than I thought.
    Sailing - the fine art of getting wet and becoming ill while slowly going nowhere at great expense.

    - Henry Beard

  31. #31
    Join Date
    Jul 2011
    Location
    Lindstrom, MN
    Posts
    2,059

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    You are fortunate that this is not about a cat boat or catamaran because I would have had to start out with "There is more than one way to skin a cat".

    I am NOT RECOMMENDING sheathing. I am providing information. Hopefully some of it is worthwhile.

    While cold molded and stripper construction can be sheathed, any other wood construction is usually a disaster. This video is a good starting point:
    Gar Wood Ensign Please Do NOT Fiberglass Wood Boats!

    If you insist on doing it with glass anyway...
    https://www.jamestowndistributors.co...t.do?docId=405
    https://www.youtube.com/watch?v=5gcut7RLho8
    One of the better forum discussions:
    https://www.boatdesign.net/threads/c...en-boat.14561/

    There is always the Vaitses approach. It seems to be a very thick shell. It has worked if done by the book. <<link to book>>
    https://www.boatdesign.net/threads/f...d-boats.42736/

    Sheathing a Tired, Old Hull This time in wooden veneers by Eric Blake
    https://www.woodenboat.com/sheathing-tired-old-hull

    There is a forum member S Downey(?) who coated a boat with polyurethane rubber. As expected it generated the usual controversy. He also experimented with PL Premium and some people have used 3M 5200. After reviewing the tech data sheets, I would rank them from best to worst as:
    Sanitred Permaflex > Sanitred LRB > Spirit Line > 3M 5200 >>> PL Premium I would prefer a harder coating, possibly a hard Shore D 50 polyurea like Versaflex, but the gel time is 3 seconds. As always, the substrate must be dry and sound, painting rot just makes an expensive bag of mush.

    Last option, and no longer available is Cascover. It was a very labor intensive and not really a DIY coating. A nylon 12.5oz cloth skin was applied with resorcinol adhesive. The directions are available here: http://www.eventides.org.uk/tip.21.htm It had a good reputation. A modern alternative might be Ballistic Nylon set in one of the urethanes above or a rubber raft coating.
    Management is the art of counting beans. Leadership is the art of making every being count. --Joe Finch

  32. #32
    Join Date
    Aug 2000
    Location
    Auckland ,N.Z.
    Posts
    24,661

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    She was a quality build from a quality yard, the keel bolts will almost certainly be monel.

  33. #33
    Join Date
    Jan 2016
    Location
    Auckland New Zealand
    Posts
    3

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    “Amazes me how much NZ boaties seem to know about NZ boats, it seems like a very tight-knit scene compared to Australia.”

    It is pretty common knowledge around these parts that most Kiwi woodnuts are related in one way or another.

    Wish you all the best with your new family member and there is nothing more pleasurable and tasking than owning a wooden yacht.
    From your comments Brightwater you fall into the bracket of those of us who reach to others for not only advice but also to undertake the works required.I am sure the Halfmoon Bay people will be more than capable of accomodating your needs but from my perspective Kishmul was built unglassed and has survived for all these years some very neglectful and others not.
    My log of wood is 45 years old edge butt and glued Honduran mahogany non sheathed and 2 pack finished and I too initially pondered the task of wooding and glassing for all of the time it took me to run the numbers and then I chose to just go sailing.
    15 years on she is in fine functional fettle and still to this day when I spy her settled in her berth or at anchor I smile.
    You have purchased a working operative classic wooden yacht so why not just use her as is for a while and interestingly she may well tell you what her most pressing needs are.

  34. #34
    Join Date
    Feb 2006
    Location
    NZ
    Posts
    2,167

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    When anyone gets a new boat there is a tendency to "improve it" and off one goes changing all kinds of things. Then a bit down the track you realise why the previous owner did it that way and change it back again. The remedy is to take your time before making big changes. It seems a given that epoxy/glass sheathing is the done thing on a timber boat but its not automatically best practice. The sheathing will do about zero for abrasion and impact resistance so the only real reason is to stop water getting in and to do that you will need to scrape the hull right back to bare timber let it dry for a few months, fill and fair it then glass it, fair it again (trust me this is a big job) Then to justify the sheathing you will then have to do a LPU paintjob. It's a massive job, if you get the pros onto it expect to pay 30-40k, if you do it yourself then expect weeks of work including many days on the longboard. All that for an arbitrary goal that you read about, nice theory and feelgood factor but that's about it!

    As I mentioned earlier, its not broken, its not rotting, there is absolutely no need for you to go down that route. This is coming for someone who trusts epoxy and who has had a three skin boat and who also has filled faired and painted it. I also race on a mates three skin 1960 boat that has never been glassed and has a LPU paintjob and its perfect, not a sign of movement anywhere. Before you rush in, it may have been done anyway, check it carefully as the standard practice at the time was to sheath the boat in a light tissue, just to hold a skin of epoxy to it. Its almost imperceptible if you dont know what you're looking for.
    whatever rocks your boat

  35. #35
    Join Date
    Aug 2017
    Location
    Melb, Vic, Aus
    Posts
    177

    Default Re: Epoxy sheathing a cold-molded Sparkman Stephens - is fibreglass necessary?

    Also as Priscilla mentioned. Its a "wet boat". If you were to dry it out for several months/years, you may start popping skins, glue joins... jeez. Who knows? Potential massive can of worms. Sail that beauty, that's what I would do.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •