Plywood / Epoxy /"Stitch and Glue" hull limitations?

[dokondr]

I wonder what are the size and sailing area limitations for stitch and glue hulls. Is it feasible to build 43' ocean sailing cruiser with plywood hull built using stitch and glue method?
Please advise on the research, books, etc. on the applicability and limitations of different construction methods and most of all on practical tests of hulls in different sailing conditions.
Thanks!

[Boatsmith]

Sam Devlin has been building large stitch and glue vessels for years. Reuel Parker's boats are not exactly stitch and glue but are built of plywood and epoxy. David

[Lewisboats]

Possible...yes...but practical....not really. It would be simpler and easier to build using more traditional methods. You would bankrupt yourself using the amounts of epoxy needed to do the build and gain nothing in return. Past about 25 ft the -s are outweighed by the +s.

[Steve Paskey]

Is it feasible to build 43' ocean sailing cruiser with plywood hull built using stitch and glue method?

Sam Devlin's "Hope of Glory," a 38-foot fan-tailed stitch-and-glue ketch:

http://www.devlinboat.com/images/hopeofglory.gif

[Steve Paskey]

Devlin's "Sockeye 45," a 45-foot stitch-and-glue West Coast style tug yacht:

http://www.devlinboat.com/images/sockeye45profile.jpg

[Steve Paskey]

A photo of the Sockeye 45 under construction. Yup, it's stitch-and-glue:

http://www.devlinboat.com/images/constructionsockeye452.jpg

[Steve Paskey]

You would bankrupt yourself using the amounts of epoxy needed to do the build and gain nothing in return. Past about 25 ft the -s are outweighed by the +s.

If that's true, how would Sam Devlin find customers for the numerous stitch-and-glue boats he's built over 25 feet, up to and including that Sockeye 45?

[James McMullen]

Devlin's larger boats are built up to the necessary hull scantling thickness by cold molding extra layers of plywood over the initial panel structure because too thick of panels won't make the bends. Lotsa, lotsa, lotsa epoxy involved for sure--almost certainly >50 gallons for a 40+ foot boat.

Plus you will be saddled with the limitations of those necessary hard chines--not ideal for a sailboat, surely. I think I agree with Lewisboats that by this size, a different construction method is perhaps more suitable for a sailboat--cheaper and easier to build even. If you were going to go with a chined design anyways. . . .well I sorta hesitate to say it on this forum, but a steel hull really comes into its own on a cost/weight/performance basis by the time you get to this size. . . .

[dokondr]

. . .well I sorta hesitate to say it on this forum, but a steel hull really comes into its own on a cost/weight/performance basis by the time you get to this size. . . .

How about traditional carvel-planked hull? For 43' and bigger ocean sailers it is feasible to build and maintain with modern tools and paints, isn it?

[wizbang 13]

50 gallons is too much for a 45 footer? I don't think so. My 34 'strip plank has 80 gallons. Thats not throwing money away, it's the best spent money. Not too many old steel boats around. "Modern" carvel? yer killin me

[Chris Ostlind]

...Plus you will be saddled with the limitations of those necessary hard chines--not ideal for a sailboat, surely...




The difference in hull efficiency between a smooth shape and a multi-chined version?... How about 1 - 1.5%? If you're not building a full-on racing machine, does it ever matter? You'd lose that much speed/VMG by simply not staying right on top of sail trim and point of sail. The argument is essentially moot for cruising boats.

I know little about steel hulled boats, but I bet that an email to Sam D would get you a ton of info about the tradeoffs.

[john welsford]

I cant see why people grumble about the cost of epoxy resins. The amount of money involved in the epoxy glue is only a tiny percentage of what the total project costs, and there is a considerable saving in that there is less money in the framing and stringers.

John Welsford


Possible...yes...but practical....not really. It would be simpler and easier to build using more traditional methods. You would bankrupt yourself using the amounts of epoxy needed to do the build and gain nothing in return. Past about 25 ft the -s are outweighed by the +s.

[john welsford]

There are not really any limitations to the technique, but its gets more difficult to build as the boats get bigger and I'd not build much beyond 25 ft in stitch and tape as a first time build with the system. Sam Devlins book will give you some good direction, but I'd say that if I was to build a 43 footer I'd build it cold moulded, especially if I were building on my own as among other considerations the piece sizes are much more manageable. ( Imagine, mixing the epoxy, buttering up a near full sheet of half inch plywood, getting it up there, secured at one end and bent into place and fully fastened before the glue kicks off on a hot day.)

JohnWelsford


I wonder what are the size and sailing area limitations for stitch and glue hulls. Is it feasible to build 43' ocean sailing cruiser with plywood hull built using stitch and glue method?
Please advise on the research, books, etc. on the applicability and limitations of different construction methods and most of all on practical tests of hulls in different sailing conditions.
Thanks!

[James McMullen]

The difference in hull efficiency between a smooth shape and a multi-chined version?The difference in hull efficiency is one matter, but there's other factors. I'm talking about the difference in resale value for one, which is way more than a loss of 1.5%. Chined sailboats just plain look less sexy to a public used to gleaming, glossy, smoothly curved glass sailboat hulls. A hard chine that's not done really well looks amateurish. There's also the difference in time fairing and longboarding to get a chined boat fair at those corners. It's actually pretty laborious to make a hard chine not look lumpy and wavy--add 15% more time to sanding for every pair of chines if you're shooting for a yacht grade finish. Sure, there's some hard chined sailboats out there that have been successful, but they're definitely not most people's first choice.

[Timber]

When considering plywood as an engineering material for hard chine hulls it is far and away the best. Also the cost of plywood per square foot is far lower than clear hull timber. Chines are problematic for plank on frame boats as stresses concentrate toward the chine = maintenance.
As the size of any boat gets bigger framing and structural support of rigs and accommodation gets much more complex.
My view is that a stitch and glue boat are and will be a better value than traditionally built boats.
The aesthetics of chines versus round hulls is in the eye of the pontificator. Often times too much so.

[James McMullen]

My view is that a stitch and glue boat are and will be a better value than traditionally built boats.
The aesthetics of chines versus round hulls is in the eye of the pontificator. Often times too much so.

Whether or not that's true for tiny, trailerable sailboats in Pagosa Springs, Colorado, it sure ain't the case in the boat market for 40+ foot cruising sailboats here in the salt, amigo. "Plywood" and "hard chine" automatically command lower prices in this category--be it fair or not.

None of that is necessarily true for powerboats. I am currently building a custom 25' lightweight planing powerboat cruiser on commission that has a stitch & glue, single-chine monohedral hull form. For that purpose, S & G epoxy/ply composite is probably the very best possible construction method out there, if you're not going to be building a dozen hulls to the same design. Be assured, I'm in no way against stitch & glue across the board. I've probably built two dozen boats that way, all told. I just don't think it's optimal for a 40 foot bluewater sailboat.

[Bill Perkins]

I’ve wondered if the practical size limit for stitch and glue hulls is going to be determined by Rolling Shear stresses .This is shear load in the plane of the plywood large enough to “roll”the cross plies . It’s a concept I was introduced to when designing some stressed skin panels ,and can be a limiting factor “for certain applications involving stress concentrations “, especially at panel edges . This sounds a lot like the chines on a big stitch and glue . My source of info was ( now old) pamphlets produced by the American Plywood Association. Maybe a wider current search of engineering literature would reveal some work done on this subject more specifically relevant to boat hulls .

[Chris Ostlind]

... Chined sailboats just plain look less sexy to a public used to gleaming, glossy, smoothly curved glass sailboat hulls.



Well, I'm gonna have to disagree with you, as the interpretation of a form is entirely subjective and shall remain so. If it weren't so, Jim, then every car for sale would wind up looking exactly like the one next to it from another manufacturer.




A hard chine that's not done really well looks amateurish. There's also the difference in time fairing and longboarding to get a chined boat fair at those corners. It's actually pretty laborious to make a hard chine not look lumpy and wavy--add 15% more time to sanding for every pair of chines if you're shooting for a yacht grade finish.


Any boat built that doesn't have nice execution will look amateurish. Plywood boats are not the only ones to suffer from this malady. Most folks would like to get there, but they either don't have the time, or they don't have the driving interest. That's why the term work boat finish was developed. ;-)




Sure, there's some hard chined sailboats out there that have been successful, but they're definitely not most people's first choice.

So, instead they pick incredibly ugly SeaRays, etc. as their form of expression. Boat buyers, like any other slice of the public and their ability to appreciate aesthetics, are a fickle and pretty much lazy bunch. They look at what is plopped down in front of them and make their choices. This process would indicate that design aesthetic appreciation is driven by marketing budgets a whole lot more than the customer's ability to actually discern the differences.

Nicely, I seem to be doing OK with a portfolio that is predominantly hard-chined and made in an S&G style with marine plywood and my customers are sending me letters that say that they find the boats beautiful. Go figure.

So, clearly, this entire argument is pretty much about what rings your own personal bell.

[James McMullen]

How many in your portfolio are 40+ foot cruising sailboats, Chris? (those hideous Sea Rays aren't in this category either, by the way) I thought that you were a multi-hull guy, which is a different niche to be sure.

I admit freely that my own view of what does and does not sell is focused pretty much on what is going on here in Anacortes, Port Townsend and Seattle, and that other areas of the country may or may not conform. In the cruising grounds of the Salish Sea, a hard-chined sailboat of the same size, type and displacement as a round-bilged boat will not command the same selling price--not that a whole hell of a lot of yachts are selling right now anyways :(

By the way, I'm not down on stitch and glue as a building method across the board and Sam Devlin is a personal friend of mine, so don't read too much into my criticism of it specifically with regards to 40+ foot cruising sailboats, okay?

[Chris Ostlind]

I do have a preference for multihulls, that's true, but they are not the only boats I have designed. There are many other kinds of boats that have never been shown... as it is for most designers.

Still, the aesthetic questions remain no matter how many hulls a given vessel may have.

As to resale value... it's all about what someone else will be willing to pay and nothing more. If any of you guys have a truly firm grasp of how that music plays, please share it with all of us. I've seen junk go for remarkable prices and I've seen really nice boats go for peanuts. It all has to do with who walks up at any given moment and the particular need a seller may have to move said boat.

In short, there are no rules... especially in this market.

[Balanda]

Stitch and Glue plywood has its main advantages in speed and ease of construction. Great for dingy hulls , but once one starts laminating sheets of ply together or crawling around inside a hull adding stiffening stringers and bulkheads to a hull shell, one has to wonder , why bother. The hull skin is such a small part of a complete 43 footer.

With the cost of ply and epoxy these days, once one laminates a couple of sheets together and applies protective glass to the outside, then foam /glass/polyester starts looking mighty attractive.

In regard to epoxy usage, I've recently completed a strip plank epoxy 33 footer and used around 120 US gallons of system 3, with minimal wastage.

As far as fairing chines go, in Oz the chine flat panel schionning wilderness catamarans are popular , and nothing screams amateur louder than if the builder hasn't spent the time and money to get the chines fair.

[dokondr]

Are there any advocates of traditional carvel-planked hull (steamed or double-sawn frames) for 43' ocean cruising sailer?
Leaving aside all other issues, such as being able to resale the boat, and concentrating just on these major themes:
1) Seaworthiness and reliability
2) Maintenance and repair *in cruise*
3) Building efforts and investments

Compared to:

- 43' stitch and glue hull
- 43' strip-planked hull
- 43' multi-chine plywood or plank hull

What are the pros and cons and what method address best all these three 1), 2) 3) above formulated objectives?

Also it would be interesting to answer the same questions for 37' sailer of similar cruising kind and purpose.

Thanks!