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Thread: Plywood lapstrake with copper rivets

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    Default Plywood lapstrake with copper rivets

    Hello everyone!

    I am about to start planking a Morbic 12 by François Vivier (https://www.vivierboats.com/en/product/morbic-12/).

    The construction is glued lapstrake with 6mm marine plywood.

    I was thinking if it's possible to build the boat with 6mm plywood but instead of epoxy, to use copper rivets (2X25mm nails / 8mm roves) at 50mm intervals. Also the laps will be beaded with 3M 5200 marine sealant.

    Do you think it can be built this way or it can affect the boat in terms of rigidity, strength durability etc?

    Thanks

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    Default Re: Plywood lapstrake with copper rivets

    All three will be reduced.

    I once spoke with a startup boat building team. Their first trial boat was a pram dinghy, in glued lap ply. It slipped from their grip when they were lowering it down the stairs from their workshop. It rattled and ricochet down the flight of stairs and bounced on the concrete floor at the bottom
    Apart from cosmetic scuffs, it was unharmed. No clenched ply hull would have survived without loosening the fastenings.
    Damp will soak in past the nail heads, and the exposed end grain on all the laps, to penetrate the lams in the ply. Less of a problem with solid tree wood
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: Plywood lapstrake with copper rivets

    + 1

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    Default Re: Plywood lapstrake with copper rivets

    how does one come up with an idea like this?
    rivets and devil sperm is not an improvement over epoxy
    per Nicks story above, here is a ply/epoxy boat that hit the beach and flipped on the rocks @30 mph. Tore a 3 foot by one foot hole in the chine.
    Flipped her back over and drove her 15 miles home

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    Default Re: Plywood lapstrake with copper rivets

    Are you allergic to epoxy, or what's the reason? If you want to do it you need a better ply then okoume, try sapeli or meranti.

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    Default Re: Plywood lapstrake with copper rivets

    I was also suspecting that the exposed edges of the plywood could create a problem. In my case the boat will live on a trailer, so do you think that with the proper paint it will be a serious problem?

    To be honest, I don't like working with epoxy, monitoring for times, temperatures, sanding like crazy, fumes, etc.
    According to Harry Bryan and Walter Simmons they say it can work (off course they are writing this on their books for Fiddlehead canoe and Building Lapstrake Canoes respectively) and this is what made me consider this option.

    I have also sent an email to François and I am waiting for his reply on the matter.

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    Default Re: Plywood lapstrake with copper rivets

    Quote Originally Posted by rogtek View Post
    I was also suspecting that the exposed edges of the plywood could create a problem. In my case the boat will live on a trailer, so do you think that with the proper paint it will be a serious problem?
    This may be adequate for sealing the ply edges, International UPC is the best primer that I have found
    https://www.charlescamping.ie/store/...mer-375ml.html
    Ensure that she is well-supported on the trailed, on bunks, so that there is no flexing over hard spots that will crack the paint..
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: Plywood lapstrake with copper rivets

    I know it's a crazy idea from the beginning (the fact that I couldn't find any info says a lot). And definitely I don't believe it's an improvement over epoxy, but I am sure that working with epoxy is no fun.

    In matter of fact my initial plan was to build a traditional lapstrake, but because of my lack of experience and talking with Vivier and Gartside both told me it's a big no for the climate here and for a trailerable boat.

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    Default Re: Plywood lapstrake with copper rivets

    I built one of Oughtred's ply lapstrake boats and used Resoltech resin. You are only using the epoxy as a glue, unlike tape and fillet methods, so not very much exposure. When it came to coating the hull, I used Re 1010 water based resin. No smell, non toxic and leaves a smooth, clear, varnish like finish. That was in '07 and it is still OK, but kept undercover (and trailered)
    A2

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    Default Re: Plywood lapstrake with copper rivets

    Learn to handle the epoxy better maybe ?
    No mixing in yogurt cups, no popsicle sticks substitutes for putty knives. Use "hawk" boards and well shaped knives.
    I find 5200 to be ten times messier than epoxy.
    If one wants to build a trad vessel using no modern dukee, I totally get that and respect it, but this is not what you're attempting, have I got that right?

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    Default Re: Plywood lapstrake with copper rivets

    Well using 5200 and mechanical fastenings is not a *completely* crazy idea. I do agree with all the advice against it, for all the reasons given, but there are some precedents. Search for "Sikaflex quick and dirty boatbuilding". The makers of Sikaflex, a polyurethane adhesive similar to 5200, have sponsored boatbuilding competitions for decades. Builders use plywood, Sikaflex, and cable ties in much the same way that you are thinking of using rivets and 5200. But it's worth noting that the resulting boats are pretty basic, built fast and rough, not intended to last for more than a few hours, and many of them sink. Which may have more to do with "quick and dirty" nature of the competition than the building method but it's something to consider.

    I think the real reasons not to do it are that it's inferior to epoxy, likely more expensive, and I doubt that it would be any less messy, as Bruce (wizbang 13) notes. It might be possible, but there is likely no benefit and a lot of downside. But if you are compelled to try it then maybe build something smaller and simpler than the Morbic 12 and see how it comes out first? Perhaps the Steir 8 pram from Vivier?
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    Default Re: Plywood lapstrake with copper rivets

    Build a traditional lapstrake boat or a glued ply boat. A hybrid begs for trouble on many levels.

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    Default Re: Plywood lapstrake with copper rivets

    If you want to do that great little boat justice and sell it for a good profit, I'd try to build it to Vivier's plan at every stage.

    You're already well invested with his plans cost and probably a kit.

    Do nothing original. Have no bright ideas. Don't try his patience.

    Don't waste time thinking. Just do plan A...'exactement'.



    Pictures of a pro built one I saw at Southampton Boat show on this thread.

    http://forum.woodenboat.com/showthre...2838-Morbic-12



    Last edited by Edward Pearson; 08-30-2022 at 11:09 AM.

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    Default Re: Plywood lapstrake with copper rivets

    I'm not going to say yea or nea,
    but I will say that in my experience with repairs that a lapped plywood join with Sika/5200 is far more difficult to get apart/remove than an epoxy join...
    Construction can be messy but if you have good work habits, everything taped off well, and clean it up before it "goes off" I think that method will work just fine.
    I would use temporary sheet rock screws or clamps with a batten to draw it up and put the rivets in (the same holes) after it has cured, which is the same method I used for epoxy glued lap. Because both will tend to "pillow" between the screws without a batten to contribute even pressure.

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    Default Re: Plywood lapstrake with copper rivets

    Quote Originally Posted by Canoeyawl View Post
    I'm not going to say yea or nea,
    but I will say that in my experience with repairs that a lapped plywood join with Sika/5200 is far more difficult to get apart/remove than an epoxy join...
    Construction can be messy but if you have good work habits, everything taped off well, and clean it up before it "goes off" I think that method will work just fine.
    I would use temporary sheet rock screws or clamps with a batten to draw it up and put the rivets in (the same holes) after it has cured, which is the same method I used for epoxy glued lap. Because both will tend to "pillow" between the screws without a batten to contribute even pressure.
    To the OP: It's worth noting that to have any chance of success you would need to use 5200 as an actual adhesive, as in Canoeyawl's description here, not just applied on top of the joint as a "bead" per your original post. But to be clear, I do agree with everyone recommending that you stick with the construction method specified by the designer.
    - Chris

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    Default Re: Plywood lapstrake with copper rivets

    I built a 21ft skiff doing exactly what you described - it's worked fine for 20+ years BUT the boat was trailered with day trips - I'd leave her in the water for a week at most. The ply edges were epoxy sealed thoroughly & the paint was kept up. So it's a perfectly decent way to build a boat & I loved using the copper...Glued lap however is superior in every functional sense as pointed out.

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    Default Re: Plywood lapstrake with copper rivets

    Gluing the laps will have a couple of other advantages.First it will save the weight of a few kilos of nails and roves and second it will eliminate the task of holding a dolly on the heads of thousands of nails while securing the roves.It gets even better when refinishing as sanding around roves between coats is a miserable pastime.I know of a few glued boats that have been in use for 60 years or so with no more than regular painting or varnishing-no hardening up of the slightly loose nails that aren't there.

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    Default Re: Plywood lapstrake with copper rivets

    I have built 3 glued clinker hulls and would say that you can avoid your concerns about using epoxy - mainly by being protected (gloves whilst gluing and facemask when sanding) and cleaning up the squeezeout before it fully cures.
    Remember when you build a glued clinker upside down part of the sequeezeout comes out above the lap. So, when you cleanup the excess epoxy you do not scrape it all away, instead create a small fillet with the end of your finger (in a plastic glove) and this will push epoxy both into the lap but also cover the exposed edge of the ply for the plank you are just gluing on. It works!
    And, before you paint, seal the hull with 2 part epoxy pre-paint sealant which is the consistency of water (Norglass Norseal or International Everdure). Again because the hull is upside down the excess sealant runs into the exposed ply edges and seals that edge even more.

    I have 2 boats in the water & a CY in build - no water coming in apart from when the goofy builder who did a bad job of gluing in a centreboard case - now fixed.

    Oh, and these boats are lovely:
    IMG_0228.JPG
    Good Luck Regards Neil

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    Default Re: Plywood lapstrake with copper rivets

    Thanks for the info!

    I understand now that the benefits (if any) of this build method are significantly lower than the disadvantages and because, in any case, I will use epoxy for others parts, the best way is glued lapstrake.

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    Default Re: Plywood lapstrake with copper rivets

    Hardened epoxy squeeze-out is easily removed with a heat gun and a sharp scraper. It doesn’t take much heat to soften cured epoxy to the consistency of cheddar. The epoxy that’s within the joint is insulated by the wood.

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    Default Re: Plywood lapstrake with copper rivets

    My initial reaction was that of many posters, that this wasn't a good idea combining copper rivets with lapstrake plywood construction. Then I glanced out my window.

    This is the 1959 Dunphy I have waiting patiently for me to get around to restoring. Plywood and not rivets but small bolts. Appears to have lived a good life on it's trailer and even after all these years the seams look pretty tight. The stem is in terrible shape but the rest is in remarkably good condition.

    I wouldn't consider it as an option for a boat that lives in the water, but dry sailed? It might not be a completely ridiculous solution. It does seem like an awful lot of work and I'd be hard pressed to not simply glue up a Morbic.
    Steve

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    Default Re: Plywood lapstrake with copper rivets

    If you glued the laps with 5200 I'm not even sure you'd need rivets. The boat would probably have a few sawn frames and if screws were run from the outside of of the boat through the planking and into the frames, I'm guessing everything would be fine.

    Man, what a mess that would be to try to glue the laps with 5200 though. Not my boat, however.

    You would definitely want to seal the edges of the plywood. Old Salem / Petit ezsealer is a non-epoxy option. Couple that with primer and paint you're probably fine. "Probably" is the operative word here. But we do a lot of things around here that are "probably" fine.
    Quote Originally Posted by James McMullen View Post
    Yeadon is right, of course.

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    Default Re: Plywood lapstrake with copper rivets

    Aside from all the other comments people have made, is 5200 as strong/structural as epoxy? One of the benefits of glued lapstrake is that the epoxy joints become structural elements on their own, meaning that frames that would be necessary in traditional construction aren't necessary (or many fewer are). All the mess aside, would 5200 be able to accomplish the same?
    Daniel

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    Default Re: Plywood lapstrake with copper rivets

    The original version of Ilur uses epoxy glued and also riveted planks. As far as I can tell, and there are 20 odd year boats for sale now and again, they seem to have held up. I think in France alot were built with more durable mahogany planking rather than Occume back then, and the idea of putting a fixing through plywood to allow end grain exposure to rainwater etc isn't something I wanted to do (and put me off the design until it changed recently) it has to be said that the Ilur's so built seem to have not suffered for it. A mechanical fastening would probably help in a collision, the laps are effectively a weak butt joint, but in most cases the internal furniture reduces unsupported panel length by a considerable fraction. I think Vivier (a NA) or was it Dix, had done the calculation of a foot stamping on a lap and it needed mechanical reinforcement to avoid splitting potentially. Same reason people keep stringers in to reinforce the lap, like Welsford and Dix.

    Dad had an Oughted Whilly boat (d'you know its actually a shrunk Caledonia Yawl by 30 odd percent) that was Occume, unpainted and Deks oil finished with riveted laps, and at 20 years old maybe when he gave it a light restoration after buying it, that boat was fine too. So in practice, rivets through plywood doesn't always end in tears, even with Occume, no paint, and the boat looked to have been left with water in it for some time. It wasn't a garage queen. This was it after a spruce up.



    Perhaps 3 or 4 strake boats which infers slightly more acute lap angles, which then means a relatively narrower lap width in places at the bilge turn might benefit from rivets if the boat was to be an open boat and used roughly and were taking regular hard knocks. I saw a St Ayles skiff blog, that had got free and founded on some rocks, puncturing a hole in the planking, and it appeared to unzip the plank laps some distance also. So the laps are strong enough in normal use but are potentially a weaker spot because of the butt join in an accident. Again an open boat has more unsupported plank seam, a boat with bulkheads and tanks etc has much smaller unsupported panel lengths in general.



    Decent 3M adhesive isn't cheap, and copper rivets will cost money on par with epoxy adhesive when I did some figuring on price differences with traditional construction. Having glued internal bulkheads and a lap with some flexibility isn't likely to be a great synergy. Remember seeing a boat stuck together with 3M at a boat show, it can be used, but I wouldn't undermine your investment in time and materials cost buy doing something not standard, especially with a Vivier. Even if it held up, people will walk away at resale one day.

    I glued my boats centreline and foils with Resorcinol where I could get tight clamped joints for max durability to compliment the AYC lams, however looking back it mean't I had the cost of two adhesives as epoxy was necessary elsewhere. It will help the boat in 50 years though.
    Last edited by Edward Pearson; 08-31-2022 at 04:08 PM.

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    Default Re: Plywood lapstrake with copper rivets

    Quote Originally Posted by dbp1 View Post
    Aside from all the other comments people have made, is 5200 as strong/structural as epoxy? One of the benefits of glued lapstrake is that the epoxy joints become structural elements on their own, meaning that frames that would be necessary in traditional construction aren't necessary (or many fewer are). All the mess aside, would 5200 be able to accomplish the same?
    Those long winding faying surfaces would probably be fine with 5200. That stuff is sturdy beyond belief. I'm sure it's been done, just not done by this group on this thread. (Or maybe it has been done here. I haven't actually read most of this thread, and probably won't.) Personally, I'd build the boat with epoxy in the laps and no fasteners other than what goes into sawn or laminated frames. And I don't even like epoxy.
    Quote Originally Posted by James McMullen View Post
    Yeadon is right, of course.

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    Default Re: Plywood lapstrake with copper rivets

    Just use West Systems epoxy in the laps.
    She will be tight and secure.
    My last build was plywood lapstrake, epoxied laps, with screws into the frames.
    She is rock solid and has not leaked one drop since her launch nearly one year ago..
    I thought about what you are suggesting to start with, but have no regrets at all about using epoxy now.
    It is the best way to go in my opinion.

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    Default Re: Plywood lapstrake with copper rivets

    Quote Originally Posted by Edward Pearson View Post

    Dad had an Oughted Whilly boat (d'you know its actually a shrunk Caledonia Yawl by 30 odd percent) that was Occume, unpainted and Deks oil finished with riveted laps, and at 20 years old maybe when he gave it a light restoration after buying it, that boat was fine too. So in practice, rivets through plywood doesn't always end in tears, even with Occume, no paint, and the boat looked to have been left with water in it for some time. It wasn't a garage queen. This was it after a spruce up.


    That will be because Deks is a penetrating oil that will have soaked in around the nails and pickled the wood in the nail holes. Excellent stuff.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: Plywood lapstrake with copper rivets

    Thousands of mechanically fastened plywood planked lapstrake boats have been built over the decades.
    Every lapstrake Chris Craft was built this way (and with Thiokol in the laps).





    Every post war Lyman, every Thompson, Penn Yan, Cruisers, EM White and many more were built this way.





    So what is the difference we are talking here?

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    Default Re: Plywood lapstrake with copper rivets

    Quote Originally Posted by nedL View Post
    Thousands of mechanically fastened plywood planked lapstrake boats have been built over the decades.
    Every lapstrake Chris Craft was built this way (and with Thiokol in the laps).

    Every post war Lyman, every Thompson, Penn Yan, Cruisers, EM White and many more were built this way.


    So what is the difference we are talking here?
    All true Ned, but the difference is that the OP wants to build a design that doesn't have frames because it's intended for glued lap using epoxy. The bulkheads and thwarts *might* take the place of frames but it's still a pretty big change.
    - Chris

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    Default Re: Plywood lapstrake with copper rivets

    Quote Originally Posted by cstevens View Post
    All true Ned, but the difference is that the OP wants to build a design that doesn't have frames because it's intended for glued lap using epoxy. The bulkheads and thwarts *might* take the place of frames but it's still a pretty big change.

    Ahhhh, thank you. I wasn't paying attention to that. (knocking head against wall now). That is a bit of a different story for sure,

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    Default Re: Plywood lapstrake with copper rivets

    Quote Originally Posted by cstevens View Post
    All true Ned, but the difference is that the OP wants to build a design that doesn't have frames because it's intended for glued lap using epoxy. The bulkheads and thwarts *might* take the place of frames but it's still a pretty big change.
    Weeeelll.

    Norse and their derivative Shetland boats frames are at 3' spacing.
    Are the close spaced timbers in treewood planked boats intended to stop the plank splitting, which is not a problem in ply planking.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: Plywood lapstrake with copper rivets

    Quote Originally Posted by Peerie Maa View Post
    Are the close spaced timbers in treewood planked boats intended to stop the plank splitting, which is not a problem in ply planking.
    I'd think that as much as having something to fasten the planks to once they're persuaded into their proper position as the build progresses. When done they become part of the boat as extra support for the planks, which over time and during use can and will 'move' a little being solid wood. Ply doesn't move quite the same.

    To my mind the biggest issue with using nails would be the risk of splitting planks at the edges when nailing. Ply ought to resist this better than solid wood to a degree being that the cross-laminated grain structure of it is more forgiving of that kind of activity. At the same time though that cross-grain structure makes a plank of the same thickness less stiff in the long dimension as half the plank's thickness is cross-grain. That's where the glued lap effect with epoxy begins to show its stuff for rigidity in a hull.

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    Default Re: Plywood lapstrake with copper rivets

    Quote Originally Posted by sp_clark View Post
    I'd think that as much as having something to fasten the planks to once they're persuaded into their proper position as the build progresses.
    Not really, timbers or frames are fitted to clinker boats after the planks are hung, and the nails are clenched. Sometimes when the bottom is finished, then when the topsides are complete, or for steamed timbers and some sawn frames, when all the plank is hung and clenched.
    You may be thinking of the carvel, frame first tradition.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: Plywood lapstrake with copper rivets

    Quote Originally Posted by sp_clark View Post
    I'd think that as much as having something to fasten the planks to once they're persuaded into their proper position as the build progresses. When done they become part of the boat as extra support for the planks, which over time and during use can and will 'move' a little being solid wood. Ply doesn't move quite the same.

    To my mind the biggest issue with using nails would be the risk of splitting planks at the edges when nailing. Ply ought to resist this better than solid wood to a degree being that the cross-laminated grain structure of it is more forgiving of that kind of activity. At the same time though that cross-grain structure makes a plank of the same thickness less stiff in the long dimension as half the plank's thickness is cross-grain. That's where the glued lap effect with epoxy begins to show its stuff for rigidity in a hull.
    As Nick said, typical lapstrake construction calls for ribs going in after the hull is completely planked.










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    Default Re: Plywood lapstrake with copper rivets

    Umm, OK.

    Point taken.

    I wasn't thinking thru what I was gonna post (coffee hadn't soaked in yet) & hit a little too soon.

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