How big a boat can built with glued lap construction ?

Probably due to high price and difficult access of good timber. Used to do screw or rivet fastened scarfed in repair lam frames using dry oak from the store down the street, no need for green clear bending wood from the forests of Planet Unobtainium.
Secret was thickness just under 1/8" and good technique. Dry oak glued well and was thoroughly sealed so it would not get wet and swell. There are many Folkboats, IODs, Bird Boats, Monterey fish boats and Knarrs around California with my repaired frames from 20 years ago. These are mostly 'shell' boats without caulking except for the Bird-class sloops.

 

Totally true, like any logical comparison. Generally speaking, lapstrake frames can be lighter and have greater spacing due to riveted plank edges if you're only dealing with hydrodynamic forces. Carvel boats will 'pant' and spit caulking if frame spacing is much more that 16" unless planking is quite thick. War of 1812 American Privateers captured and examined by the English often had cedar top timbers and greater frame spacing in their ends to give better stability and speed. Examining surveyors were horrified at the rustic details but lost the war anyway.
Never personally saw a carvel Folkboat, but Hasler's JESTER was one I believe.
Plank on frame carvel is still the fastest and cheapest way to build a long-lasting boat of conventional type if you can find a good timber supplier.
Comes down to question, if lapstrake ply, is it for cheapness, long life, strength, seakeeping, cool factor, or because you have the wood?
Lapped plank boats are noisy inside at anchor, are always getting chafed and the laps bumped and damaged and are hard to paint.

 

Cheapest timber boat possible? Not lapped plywood but the lap plank, modified and smaller SPRAY with Chinese main in this photo named REDLEG was built by two of us under contract to a private owner in a corner of the old and long gone Bob's Boatyard in Sausalito in the late 70s for $5000.
She went together and was launched in about 8 weeks if I remember right. Terrible lining off job because we didn't really do one, just set up a few molds and started spiling, planking and riveting without planing the boards even. They went on the boat as they came from the sawmill, which had sharp tools and sent a good quality of wood. We did everything possible to cut labor corners and save material, using Friendship Sloops by Morse or any real Tancook Whaler as shining examples. Our bronze keel bolts were an exception. All of these boats have inside ballast, sometimes stone, which we originally put in REDLEG as it was free on the beach and kept a clean bilge.
All clear Douglas fir with bent Apitong (pain in the butt) frames, copper rivet fastened using copper Lincoln pennies for some of the roves (which cost 4cents each at the time so 1/4 the cost), no shaft log or machinery, but included mast and bowsprit. I think she's still around, last heard of in Tomales CA.
A second owner let rainwater sit in the bilges too long and rotted the deadwood so I was hired to replace same with a shaft log which I did maybe 15 years later. The rest was in good shape aside from a few broken frames at the hardest bends. I think we fixed those with sistered (at least an inch from the broken frame and taper the ends out) oak steamers and copper clench nails as the budget was very low.

 

its very likely Peter that they laminate because they are epoxy builders, and dont know how to build a boat without glue

 

Peter, you could be absolutely correct. My experience is in timber build and repair as seen in photo but I always used epoxy where it would do the most good, even a few places in BERTIE back in the 70s and glad I did.
Nigel Irens and Ed Burnett favor the methods and their boats are pretty impressive. I think one of Nigel's huge cold-molded trimarans holds the circumnavigation record, or did recently and the WESTERNMAN series of Pilot Cutters is very good. I lust after ROXANNE (pic) with her unstayed carbon fiber lug rig, fiberglass backbone/centerboard trunk and sheathed strip planking and blistering performance under sail on all points combined with comfort for such a small boat due to stability and room inside with few frames.
Absolutely these except the multihulls can be built in timber to a high standard probably at a lower cost but the glue boat will not soak up water or work its seams or have a wet bilge and it's easier to keep the weight lower I would think due to greater flexibility in scantling specs.
Only an opinion but from 50 years of boats.

 

There is only one aspect of an epoxy glued boat that i require .That is the dry storable aspect . Other than that ,I'd prefer carvel .

 

I remember Herman Hermanos from a WB story a very long time ago ,built in a SF boatbuilder's coop ?

 

Then sheathed strip or diagonal veneers would make sense I think. Sheathed strip is chosen by very good designers Burnett and Irens, can be ordered from abroad already milled with a cove and round, is very strong and long lasting and generally better than lapped ply in my mind.
A timber backbone and light framing structure go well with this build and have been long proven. The sheer stringer and edge is very simple and strong. The surface is smooth and easy to maintain a good finish with polyurethane paints. There is no problem with the garboard seam.
It dry-stores very well.

 

Yes, the Gate 3 Boat Co-Op in Sausalito, just North of SF. Gate 3 because it was in the rich ruins of a WW2 shipbuilding yard that built over 100 Liberty ships and Tankers in 3 years and that was the particular entry gate. The boat was HERMANAS Y HERMANOS, Spanish for "Sisters and brothers", a reflection of the rather strongly held politics of the owner/builder.
Several of us needed a facility and had the generosity of Mr. Donlon J. Arques who rented us the land for a tiny sum, loaned us a 42" ship-saw, sold us incredible boat things at 1939 prices and generally supported our efforts and taught us how to do real things.
When he was teaching me to hew masts he sold me his fine broadaxe but said, "You know I paid $15 for this in 1925 so I'm going to have get $20 for it." I have it today and it has created a dozen fine masts that still stand on vessels and take them where they wish to go.

 

Yep ,but essentially the result is no different to a glued lap structure .The only problem Ihave now is the garboard seam .....speaking of which ...why can't I just mechanically fasten it and caulk it ? That would allow some movement while allowing the 2 monoblock halves to remain stable .


BTW ,congratulations on falling on your feet as a young bloke .That must have been a great experience !

 

Thanks I was very lucky but also seized the moment. Here's a pic from those long-ago happy times. As to the caulking- you can't drive cotton against the plywood edge especially in the stem rabbet really without crushing and causing damage, even separating veneers a little, so might have to fasten well to a hog or keelson and bed in some rubber like 5200. One trick is have a fairly large (1/4"+) seam to allow for some movement and the rubber room to give. Thin rubber pulls away. A problem is making it stick to the oily keel wood. Just filling the gap and not sticking will work but it's not optimal. One reason for driven caulking on trad boats is to tightly jam the adjoining pieces together with great friction so they cannot move, like driving wedges, that would be missing here but may not be necessary in this case. Down the road if it leaks, it may be hard to make it stop if you can't caulk it.
Of course as you say in all these cases you are making two monobloc shells and joining them to a conventional backbone, though in the strip and veneer cases the shell is sometimes glued and nailed to the rabbet with no caulking. Don't forget the stopwaters at the keel joints.

 

I’m not a NA but I am a engineer who builds boats; I have a few observations to make.

Size: I don’t see any structural reason why you cannot build as big a boat as you wish using glued plywood lapstrake. It’s a great method and a great material.

Weight: construction will be harder than necessary if skin thickness is overdone.

Scantlings: a lapstrake hull is a monococque structure in which the strength is provided by the continuity and integrity of the skin rather than a frame. There is no merit in overbuilding or increasing scantlings and it may well be counter-productive if it results in stress concentration in one place that initiates a local failure that can spread.

Glassing: lapstrake is a great way to build a hull but it is incompatible with glassing, although it can be done. There are other ways to build a dry-storable boat which is to be glassed like ply-on-frame, stitch-and-glue and cold-molded, and glassing is part of the process with modern strip-planked hulls.

Worm: is worm really is a consideration in a dry-stored boat?

Mods: when it comes to modifications, as a general rule, build the boat the way the designer intended, or run your desired changes by him first before you build.

Mixed construction methods: both modern and traditional construction methods are systems. Each system was developed over time and bugs were worked out over many design and build cycles. If you mix methods you are designing a new system, and you only have one design and build cycle in which to find and work out bugs.

Par: of course, my advice doesn’t apply to me. Hope you are feeling better soon!

 

I love those Nigel Irens Roxanne's. Not popular in the US, but I see a few used Roxannes for sale in Europe....when I grow up, throw down my sea boots and give up sailing for good, Im gonna get A Roxanne and go sailing. .

 

Here's something interesting .

I've just been reading ,''Cold Moulded and Strip planked Wood Boatbuilding '' ,Ian Nicholson ...designer of some famous boats Galway Blazer ,Myth of Malham,
On Pp 65 and 66 he says it is acceptable to use , laminated , solid or a combination of the two on a cold moulded hull ,the same rational ,ie two monoblock hull halves joined to a central backbone would apply as much to his discussed method as to glued lap .I'll read on .


I also came up with some very nice oregon (douglas fir ) today as well .The thinking continues .

 

Since I wrote that I discovered a Wiki article: I quote this para which nicely summarises the factors that limit lapstrake hull size -

"There is an upper limit on size of clinker built vessels, which could be and was exceeded by several orders of magnitude in later large sailing vessels incorporating carvel built construction. Clinker requires relatively wide planking stock compared to carvel, as carvel can employ stealers to reduce plank widths amidships where the girth is greatest. The need for sufficient lap to accept the clench fastenings drives towards wider planks in proportion to thickness that can be employed in carvel. In all other areas of construction including framing, deck, etc. clinker is as capable as carvel. Clinker construction remains to this day a valuable method of construction for small wooden vessels."

- the plank width limitation can be solved by the use of plywood. The handling challenges of large thick ply scarfed into long pieces seems like the major limiting factor. On a smaller scale, I can vouch for the difficulty of handling a 14' (4.2 m) ply plank only 4 mm thick and 5" (13 cm) wide, especially with a curve that makes it hard to transport without breakage.