epoxy on "traditional" lapstrake?

[DugT]

I really like the look of lapstrake hulls, but any boat I might build would need to be trailered. My question is this...if the new 12'Catboat Tomcat can be built carvel with epoxy between the planks, and strip-built boats can be constructed without bevels so that epoxy can be slathered into the cracks, then why couldn't one build a lapstrake boat with boards v. plywood and use epoxy to glue the laps? I know the question, "Why?" will probably come up--it's because I can get decent cedar, fir or pine boards locally but marine ply has to be shipped in. I went that route with my first boat and the shipping was as much as the plywood. TIA.

[JimD]

No reason I know of why you can't. Go for it if that's what you'd like to try

[Venchka]

The folks who really know will give you all the details. Here's the Cliff's Notes version: don't do it. If you really worry about the laps opening, and in Las Vegas that is a real concern, a small bead of Thiokol polysufide sealant in the laps will probably work just fine.

Just my $0.02 worth.

Wayne
In the Swmap. :D

[Venchka]

Whoa, JimD, based on what? If that were true, glued lap plywood construction wouldn't exist. What about all the sage advice about the planks moving, spliting and tearing the fasteners out? Eh? :D

Sometimes I worry about about our Northern cousins. :rolleyes: :eek: :cool:

Wayne
In the Swamp. :D

[JimD]

Wayne, good buddy, everybody's an expert and what the heck do I know for sure but if I were going to build a 12 foot dinghy in glued lap and preferred to use solid stock instead of plywood I wouldn't worry about it. The planks definitely won't be working against each other, the epoxy will see to that. I might add a few ring or clench nails, or rivets for added peace of mind. That leaves the argument that the epoxy won't be able to handle the plank expansion when they take up water but if plank expansion won't tear a glued carvel dinghy apart it won't happen to lapstrake, either. If the boat is epoxy coated and most likely dry sailed from a trailer these are entirely non issues. My $0.02 :D

[JimD]

If that were true, glued lap plywood construction wouldn't exist Many people find plywood easier and cheaper to come by, and easier to work with as well. It is frequently used not so much because it is necessary but because for practical reasons it is preferred.

[Jack Heinlen]

The planks definitely won't be working against each other, the epoxy will see to that. But they will be working against the framing, and dollars to dognuts will split. What you create is a solid piece of wood the cumulative width of all the planking. You can't restrain wood across that kind of width and get away with it.

For a way to do what you want have a look at Walt Simmons' books on lapstrake boatbuilding. He has a method with sikaflex that works.

[L.W. Baxter]

The planks will crack if glued together. A flexible sealant, or nothing at all, is the way to go.

See the FAQ thread for several treatise on this subject area. The thread on glued-lap construction is informative, and entertaining besides.

--Lee

[Roger Cumming]

You may find instructive Pete Culler's opinion about putting anything between the strakes in lapstrake construction: don't do it. He writes about lapstrake construction as he practiced it in his book SKIFFS AND SCHOONERS. He didn't even use epoxy anywhere in his boatbuilding but depended on good fits and proper fastenings. He advocated clenched nail fastenings in lieu of rivets in lapstrake because it didn't require a helper. I am not saying that this is the definitive word on this kind of traditional boatbuilding. However, few of use have anything like the experience he had, and no one I have read made so convincing an argument for his approach to boatbuilding. And he earned a living doing it.

Harry Truman once said, "There is nothing new in this world except the history you do not know". Before you try inventing a new boatbuilding technique, educate yourself. Find out how others before you approached it. Invest in a shelf of relevant books on the subject. You could avoid stupid mistakes. Look up Walter Simmons, a master of lapstrake construction whose books on the subject are affordable. None of this should blunt your enthusiasm, but it could prove invaluable to you.

[JimD]

Looks like I'm just gonna have to build one to prove you all wrong!

[Venchka]

There you go.

However, DugT didn't tell us what boat he wanted to build.

Now, the heavens are going to open and swallow me whole, BUT...

Pete Culler didn't live in Las Vegas. Pete Culler didn't build boats to live on trailers in garages in Las Vegas. Pete Culler's boats rarely travelled more than a few feet above high tide. Pete Culler's boats had the advantage of sitting in slings for a few days until they took up in the spring. Sure, he built sweet boats. Yes, the world is a better place for his work. However, had he bothered to look around, he might have found more than a few products invented in the 20th century which just might have made his boats better. Or, at the very least, allowed us mere mortals to build a useable boat for the place where we live and use it.

As for the Steward/Simmons polysufide in the laps treatment: The sealant doesn't go all the way across the lap. It's just a bead filling a shallow V at the lower outside edge of the lap. Not unlike the epoxy fillets on my glued lap boat. 3M-101 or BoatLife LifeCalk.

Diving under my rock.

Wayne
In the Swamp. :D

[ 12-05-2004, 04:19 PM: Message edited by: Venchka ]

[Magwitch]

Mind you, if you really must use solid stock why not not steam in a few frames and hold the thing together with boat nails and roves?
It'll be a better boat...
IanW

[Dave Fleming]

Suggest the initial poster go back, re-read the WB article on the Tomcat and, the reasons Wm. Garden listed for using that particular method on that particular boat.

[Venchka]

You know, we're running our fingers here and we don't have a clue what DugT wants to build.

DugT, whatcha want to build? We need more data.

ps: Dave's right as well.

Wayne
In the Swamp. :D

[ 12-05-2004, 04:34 PM: Message edited by: Venchka ]

[Gary E]

A friend of mine has a 1965, 36 ft CrisCraft Sea Skiff, hard chine construction, plywood lapstrake bottom, the laps are BOLTED together, this is from the factory, and the bolts are spaced aprox every 4 inches. I dont know what the sealant is, but I suspect Thiokol.

[ 12-05-2004, 04:47 PM: Message edited by: Gary E ]

[Paul Pless]

IIRC, Garden also specified a glassed bottom in addition to the epoxy construction. This leads me to believe that the wood that was most subject to expansion due to moisture, was for all intents epoxy encapsulted.

I believe glassing a lapstrake boat would be both impractical and aesthetically unpleasing.

[JimD]

Originally posted by Dave Fleming:
Suggest the initial poster go back, re-read the WB article on the Tomcat and, the reasons Wm. Garden listed for using that particular method on that particular boat.The Tom Cat article is in issue #176. The hull was fiberglassed. I quote (typos don't count...)

The hull could be traditionally caulked with cotton and seam compound. But the soft Western red cedar planking is a worry when pulling up on a rough beach...The epoxy skin forms an added tough membrane to help with chafe, plus it provides a leak proof hull. Also, thickened epoxy pressed and knifed into the caulking seams in lieu of cotton and seam compound is an excellent shell stiffener, counteracting the torsional load off the mast's heeling force against the righting moment of the crew's weight to windward. For a boat dependent on beach landings, a heavier fiberglass skin, plus perhaps bilge keels, should be fitted...

That's from page 46. Anywho, just my humble, amateurish opinion, as much as I appreciate the logic of traditional methods and the possible problems when adding epoxy to the equation I just don't see how any lightweight dinghy 12 ft or so that is thoroughly glued up as a monocoque hull is going to fall apart because it is made out of 'real' wood and not plywood, even if the planks are lapped. Maybe I really should build one and find out :D

[Dave Fleming]

the laps are BOLTED together,Yes, I have seen that method on several older boats.
Proper sized machine screws w/nuts/washers fastened at the laps.

[paul oman]

Doesn't seem like someone else's 2 cents of imput is needed, but since I get no respect at home.....

From an epoxy vendor's point of view...

Plywood has almost no expansion/contraction (at least compared to 'real wood') - that's a good thing when it comes to plywood and epoxy and might tilt things in favor of the ply method.

The edges are the weak link with plywood. Would need to be carefully epoxy sealed.

If I were building with this method I think I would use epoxy in the overlap areas of the planks, thus gluing (or laminating) the boards into a 'sold' hull. Then paint the entire inside and outside of the hull with a flexiblized or flexible epoxy (clear or pigmented). On only parts of the hull that seemed 'weak' I would epoxy fillet the seem between the two planks on the inside of the hull.

If I was being that experimental, I would so epoxy in a plexiglass 'viewing port' on the bottom of the hull too - something I always thought would be kind of cool...

regards

paul oman
progressive epoxy polymers

[Bob Smalser]

Las Vagas, fellas....Las Vegas.

What violations of convention that can be got away with in Maine, Washington and even (a big long-shot) Alberta will destroy itself in one 6% EMC Nevada summer. It ain't the rain, it's the humidity, and you don't have any to speak of. Heat just speeds things up dramatically.

Heck....you are gonna have to acclimate the dickens out of any 9-19% solid stock straight off the truck from Oregon or B.C....even without fastening a large, glued "panel" crossgrain...to keep it from cracking. Glueing that stock without facilitation for majot movement in your climate is...well, unwise.

Use plywood.

[ 12-05-2004, 08:18 PM: Message edited by: Bob Smalser ]

[slacker]

I can only add; I built a small poplar table with some inlay work while living in Denver. When I moved to western WA, the thing sucked up moisture and MOVED in a big way. I'm glad it was a table and not a BOAT.

Darren

(BTW Bob, 7/10 is me on the ww.org site... thanks for the reply)

[landlocked sailor]

Rich Kolin, who was a Pete Culler friend & protege, wrote "Building Catherine". 'Catherine', as built by ChuckG, is a traditional lapstrake Whitehall. Rich recommends a flexible sealant, like a polyurethane, in the laps. He states he has also had good luck with regular siliconized latex caulk. This is specifically for boats that will live on trailers. Walt Simmons details a method for sealing the planks AFTER the boat is planked: a groove is 'pressed' into the lap and filled with a sealant. I am sure that using epoxy in thlaps would be messy and unpleasant and would offer no advantage to the above methods. Rick

[DugT]

Thanks everyone for your info and opinions.

Wayne...I would build something small...I have the plans for Paul Fisher's Inishmore 10' and Woodlark 13' but there are lots of small boat designs I like. The Woodlark plans give the mould shapes for clinker construction. In any case, the boat wouldn't be bigger than 15' max.

Doug

[Venchka]

As I have seen in Texas and Bob said about Las Vegas, where you live plywood is probably best. You might be able to get away with totally traditional lapstrake (clinker) construction. However, if you let the boat get really wet after building it's going to swell up and do some funny things. Then it's going to dry out and do some more funny things. I think epoxy and plywood.

Hey, build a bigger boat. The more plywood you order, the less it costs per sheet to ship. Find out where the break even point is on plywood cost/freight. Order more plywood! Find other builders to split the freight charge. Take a vacation up to Washington and wag home some plywood. :D

Wayne
In the Swamp. :D

[ 12-05-2004, 09:50 PM: Message edited by: Venchka ]

[JimD]

For those interested if you can find a copy of WB issue #160 there is an article on Robb White, which describes how he builds epoxied lapstrake with solid tulip poplar planks.

[Phillip Allen]

Hey Venchka, I notice you're from Belle Chasse. My neighbors are from there ((Pichoff's). I got the impression Belle Chasse wasn't that big...?

[Venchka]

Originally posted by Phillip Allen:
Hey Venchka, I notice you're from Belle Chasse. My neighbors are from there ((Pichoff's). I got the impression Belle Chasse wasn't that big...?I work in Belle Chasse. It's not big, but it's on the edge of the Lesser New Orleans Metro area. I live in Orleans Parish about 7 1/2 miles from the office.

Wayne
In the Swamp. :D

[paul oman]

A bit off thread,

But I wnet to Schlumberger school in Belle Chase, while living in Harvey, La.......

small world sometimes...

paul oman
progressive epoxy polymers

[Venchka]

Yep. Prior to moving to Orleans Parish (so my daughter could attend Ben Franklin H.S.) we lived in Harvey also. Heck, we might have been neighbors! :D

Wayne
In the Swamp. :D

[JimD]

And as long as Robb White has been successfully building boats this way for years I wonder if anyone from Vegas has actually encapsulated a plank of cedar and floated it in a tub of water for several hours twice a week or so to simulate a hull in water to see how it holds up?

[Jack Heinlen]

Well, if you encapsulate the entire thing in epoxy it's no longer a "traditional" lapstrake boat. I've not read White's article, but...how to say it. Encapsulate poplar in epoxy and you better make sure the encapsulation stays intact. Epoxy will keep water in as well as it keeps water out, and poplar with the right moisture content will rot, quickly.

I think, if he really has his heart set on solid wood, that wood allowed to acclimate well to a dry summer will work with Simmons' method. But I have no experience with such conditions.

[gert]

While we're on the subject, are the solid planks flat or edge grain?

[JimD]

DugT, don't know if you're still with us or if you're off shopping for plywood, but just a final thought. There must be a local boat club or outdoor org in LV or Lake Mead perhaps. Can you ask around to see if anybody else has a cedar/epoxy built boat such as a strip plank canoe or kayak? If there is and the boat is holding up to the very dry climate you might still want to go ahead with glued lap cedar. Good luck

[Venchka]

DugT,

I've done a bit of research. Now I'm really dangerous.

Would you like a traditional building method enhanced greatly by the use of epoxy? A traditional hull type that will stop folks dead in their tracks?

Visit the library, use inter-library loan if you must, get this book by John Gardner:

http://www.woodenboatstore.com/store/images/300022S.JPG

Or buy it straight away from the WoodenBoat Store. It's worth owning.

Double diagonal planking. Rangely boat. Short, narrow, thin strips of cedar or doug fir. Cut around and between those pesky knots that ruin clinker planking and make lumber cheaper. Though, light, dimensionally stable, no leaks. Roll your own plywood. A dash of C.P.E.S., a couple coats of Kirby's paint and "Bob's your uncle", a boat for the desert and the water. Plywood not required!

I told ya'll I was dangerous!

Gert, flat grain I think. Verify that! :D

Wayne
In the Swamp. :D

[DugT]

Jim,

I don't think I'd be afraid to build a strip-planked boat even in this dry climate (ironically, it's raining as I type this). I can't explain the engineering, but my intuition tells me that the narrow strips would be under much less stress than the planks of a lapstrake boat. Someone in this thread mentioned that they thought the planks would split and tear out at the fastenings, but assuming I were to try this, I really wouldnt need fastenings would I? My concern is that the planks would split during contraction and expansion. But then I've got a good bit of real wood in my little motorboat that has gone through several seasons of temperature extremes in my garage(120F-25F or so) and the joints haven't opened at all. I used polyurethane glue on most of that. So, maybe like you say, I should just try it and see what happens--maybe on a small scale as an experiment, like 1/2 scale on the 10' boat.

Wayne,

I'll look for that book at the library today. I assume the double diagonal planking gives a round-bilged hull...is this like cold-molding? Anyway, thanks for your replies smile.gif .

Doug

[Venchka]

Once again, I just don't know.

Gert,

Maybe clinker planks should be vertical grain to minimize swelling and shrinking movement. Somebody with real experience will know.

DugT,

Would you believe John Gardner if he said don't glue clinker plank laps? He did.

Wayne
In the Swamp. :D

[DugT]

Yeah, I'd believe him, and I'll soon be reading his words myself as I've requested via interlibrary loan the title you recommended. In the meantime, I've been looking at one of Paul Gartside's designs--a 15' double-ended rowboat to be built carvel style. He says the seams are to be payed with elastomeric caulking to keep the boat tight out of the water. The sheer plank is lapped for aesthetic reasons. So maybe carvel is in my future...and hey, at least I'd have TWO lapped planks. Hmmm, wonder if those sheerstrakes are caulked as well...being that high on the hull I guess maybe they wouldn't need to be. Anyway, thanks again, I'm looking forward to reading that book.

Doug
In The Desert :cool:

[Venchka]

Give Paul a call. You'll enjoy the experience. He will steer you straight. You could do worse than build one of his designs.

Wayne
In the Swamp. :D

[JimD]

Would you believe John Gardner if he said don't glue clinker plank laps? He did.
I'd be curious to know the context in which he said it.

[Venchka]

He said it in the context of (paraphrasing-the book's at home) "never glue the laps of clinker planks together. The shrinking and swelling will tear the planks apart." Bluiding Classic Small Craft, combined edition. Page 24-something, as I recall.

Robb White would argue the point. Who knows for sure? :confused:

Wayne
In the Swamp. :D

[ 12-10-2004, 10:31 AM: Message edited by: Venchka ]

[JimD]

Wayne, Robb White knows for sure because he has actually taken the time to do it!!!!!!! Sure, Gardener and others are right to say you shouldn't take a trad built boat and just start stuffing epoxy in her joints in a sort of make shift way without thinking through the forces at play and having a well thought out plan to stablize the entire hull. But for example, White fiberglassses the individual planks before assembly, which is another point I have raised only to hear the pundits say 'Ohhh! You can't do that!' He also doesn't bevel the lands so the planks remain thick and strong where they join. And he points out that the poplar he uses for planking has exceptional cross grain strength. The planks are not perforated along the grain to accomodate rivets or nails which weakens them where they need to be strongest. Yet some of his boats are extremely lightweight. Some well under 100#s. It wasn't long ago that all the experts were saying it would be a disaster to epoxy between carvel planks instead of caulk for the same tired rationale that plank expansion and movement would destroy the boat, but this is exactly how Tom Cat was built. Innovators have proven there are ways to combine traditional methods with epoxy and cloth that work yet there are still so many folks out there in denial about what is already fait accompli. And until I hear that White has made a terrible miscalculation and his boats are all falling apart a couple years after being built I will continue to doubt the naysayers who parrot old wisdoms that need not apply. Rant over.

[Bob Smalser]

Fiberglass boats have been built since WWII successfully using solid, laid up balsa cores and thick polyester.

Mr White's encapsulated Tulip Poplar boats are an expensive refinement of that glass technique using thinner and stronger epoxy....pushing the envelope of crossgrain fastening in solid wood by gambling on the epoxy slowing down wood movement.

Nothing wrong with pushing the envelope if you are willing to accept the risk....and Mr White certainly does. I don't know if he's had one crack open on him....but I wouldn't advise buying any Georgia-made boat, moving it to Nevada and let it bake in the sun.

A 6" q-sawn Tulip plank shrinks only 3 thousandths going from the 9% M/C he glued it at to the 6% M/C common in a Nevada summer. Tulip is strong stock and that's probably...probably...not enough movement to cause major problems.

But epoxy doesn't stop moisture movement and the resulting wood expansion/contraction...it just slows it down. Leave that boat in the water long enough or take it to Puget Sound for the long, wet winter and it will achieve 13% M/C, where that plank will shrink 7 thousandths when taken back to Nevada....and that's surely more than enough to crack it.

Not to mention the long-term effects of unrepaired chips and abrasions exposing bare wood to moisture ingress only to be slow drying because of the epoxy. No shortage of data out there on wood-core glass boats with rotten cores.

Like anything else, it's all a matter of tradeoffs and risks....I'm only advising what some of them are. You won't have to worry about any of that as much with most plywood boats.

[ 12-10-2004, 12:15 PM: Message edited by: Bob Smalser ]

[JimD]

Thanks for the input, Bob. I've simmered down, now :D I think the Tom Cat mentioned in the original post was made in and for coastal British Colombia. Like you say, Nevada and the PNW don't mix very well. Since I am personally an amateur with dubious skills and credentials I will probably only ever build in plywood, a much safer medium for my level of ability.

[Russell Sova]

If you look close at one of the photos I posted in Kathleen Marie you'll see another boat in the garage (one car garage, two boats) that is a lapstrake epoxied hull. Some places stayed rock soild, others seeped a little water. A ten year throw away boat is what I ended up with, although I had it less than that, but that's how I looked at it. I read a book by Pete Culler that said you can get ten years out of a wooden boat. It stayed tight enough to be safe and fun and dry. I trailered it 60 miles one way all the time and it bounced over some gravel roads on the trailer. I wouldn't make another one, though.

[Frank Mehaffey]

I have a 16', 1958 outboard runabout which sat in a garage for 18 years. After the swelling period, the boat leaked big time, and much of the 3m goop used to back up the clinch nails was too hard, and had seperated. Put a thin bead of west system on the joints, from the inside, and 2 coats of normal thickness epoxy on the outside. 7 years, and about 100 or so miles a week on the water, and about 2000 miles a season, trailering it around, not always on the smoothest of roads, and it is dry, no new rot, and as far as I can see, no stress cracks. Epoxy on the outside, and varnish inside. Not exactly encapsulation I guess.