View Full Version : Traditional/Glued Lapstrake Hybrids?
Clinton B Chase
04-09-2006, 11:28 AM
As I was scraping the interior of my Shellback hull and thought about the next project, i wondered if anybody had built a glued lap boat up to the waterline and then riveted the topsides or perhaps the sheerstrake, gaining the advantages of glued lap and having a bit of a traditional look. A sheerstrake on a glued lap boat that was riveted would make it look traditional w/o adding weight and extra framing. Or could one even rivet the broadstrakes that are above the waterline? I imagine one would have to add some framing to compensate. Part of my thinking is that I want to find a boat to build with kids that won't leak but also teach some traditional skill. Anyway, my random thought of the day...what do people think? Thanks.
Years ago I built a "Marisol Skiff" (Plans bought from our host) that was glued lap as well as copper riveted. A great little boat that would be a good project that seems to have some criteria that you're looking for.
edited to add that Gifford Jacksons plans for "Marisol" call for rivets as part of construction
04-09-2006, 10:46 PM
I am trying to convince the engineer Dad that we should rivet the bright stuff if only for looks. He is being resistant because "it isn't in the plans".
04-10-2006, 03:08 AM
That is about the only thing that would be the difference that would show any difference between the two,new and old. I think it would look the part. They almost do without the rivets, being most modern stuff is slab sided.It would be easier than using tiny screws and then puttying the holes too. I am sure many have done this.With the glued laps and if was plywood,would maybe not even have to retighten rarely if ever.
04-10-2006, 03:25 AM
I am currently building an Iain Oughtred "Elf" in glued ply lapstrake and am clamping the planks as I glue them up by screwing them on with stainless screws which get removed once the epoxy has set. I intend to fill the holes left by the screws with copper rivets and roves bedded in epoxy. This is not really for any structural strength but just for looks as I have built the hull from hoop pine ply and will be finishing it bright.
04-10-2006, 05:48 AM
I am becoming a bit of a heathen about glued lap ply.
I built a tender 15 years ago by this method.
On the plus side - it has proven robust and is fairly light.
On the negative side the epoxy encapulation with UV resistant polyurethane over it has proven a mixed blessing - when this starts to fail, as it does, it does a fabulous job of wicking fresh water in and if not spotted rot ensues.
I'm just fitting out and I reckon the work involved with the very orthodox larch on oak lapstrake 16 footer is not so different to that involved with the 9ft glued ply lapstrake boat
04-10-2006, 08:12 AM
Not trying to hijack Clint's thread, but I don't think Lee has posted any pics of his Elf project... How about it Lee? Gavin and I are working on the dagger board trunk and rang frames on our Elf.
Clint, did you get a chance to fool around with the laser level over the weekend?
04-10-2006, 08:25 AM
I was wondering why Clinton would want to do this - then I realised that I was approaching the subject from the opposite end, so to speak.
I live near water and my boats are kept afloat, so I was wondering "why do the wet bit in plywood and the dry bit in tree wood?".
The penny has just dropped, and I now understand the proposal!
04-10-2006, 09:12 AM
To address the topic, it seems to me the boat would be, like many other hybrids and mixed-materials constructions, a bas*ard in all senses of the term -- and look pretty strange too boot. If you want lapstrake or carvel, build the whole boat that way.
If you want added strength under the water with a carvel planked boat, build it stronger. If you want the "splash-shedding" part of the lapstrake advantage, build it that way ALL the way from keel to gunwale.
One thing to consider with "faux riveting" is the issue of refinishing / repainting the interior. Rove rivet heads are VERY difficult to work around, and unless heavily peened, can also pop off when the interior is sanded / scraped down to the wood -- not to mention be nicked by scraper blades or bent by sanders. I know this from personal experience, and still haven't worked out a way to "wood" the interior of my trad fir over oak Chamberlain dory skiff without, in effect, refastening much of it.
Seems to me that if you are gonna go to all that trouble, why not just build the durn thing outa solid wood from the start? You'll really get the traditional experience, and with modern sealants / epoxies you get a good seal between the strakes and bottom planks -- 5200 or Vulkem 116 for the flexi bits and epoxy for the stiffer joins.
04-10-2006, 09:28 AM
In general, i try to avoid extraneous ornamentation and let the design and materials speak for themselves.
04-10-2006, 10:02 AM
Mixing solid wood and plywood planking is I suppose possible, but you'd have to put in as many frames as with all-solid-wood construction. If you really like the look of rivets, I suppose it wouldn’t do any harm to build a glued-lapstrake boat and then put in rivets. In fact, you could make it almost indistinguishable from a boat built with solid wood if you used the traditional number of frames. The advantages would be entirely cosmetic. I can see a few disadvantages, but they're not that large if you really want a boat with that look:
- More weight
- More cost
- More work
- More frames with nasty little pockets between them and the planks where crud will accumulate.
- Much harder to stip and refinish, as Thorne points out.
- Holes in the plywood where the rivets go through. It might be best to dribble a little epoxy in the rivet holes to seal the end grain - for that matter, it might be a good idea in traditional construction too.
I dunno - IMHO glued-ply lapstrake produces a boat that's functionally superior to solid wood construction in almost every respect except perhaps ease of repair (not that easy in traditional construction either). You don't lose much with the cosmetic rivets, but there's something offensive about putting them in just for looks - sort of like glued-on false through-tenons in furniture (I'm an engineer too).
There is one case where I think mixing solid wood and plywood is a VERY good idea - that's dory-style construction with caulked carvel seams in the flat bottom. Keeping those bottom seams tight in a trailered boat is not something you want to try to do. I know this from bitter experience.
This is larger hybrid http://www.boatproject.org/?page=progress the bottom and first strake are ply with four (4) cedar planks rivited above. The boat was designed around the construction method.
These are smaller hybrids, http://http://www.barefootwoodenboats.com/sale01.htm (http://http//www.barefootwoodenboats.com/sale01.htm) of which four have now been built.
The bottoms are sheathed outside, easy to keep clean inside, and always watertight. They visit the beach often with little worry, and mostly they are quite pretty.
04-10-2006, 01:58 PM
Not sure what you mean by 'hybrid' -- the boats look like they are lapstrake ply all the way, and riveted all the way. From the website you list -
Hull : Glued Lapstrake using 3/8 Okume BS1088 plywood sheathed inside
and out with 2oz cloth and West System epoxy resin. Bulkheads are 1/2 okume
Bs1088 plywood. Stem and keel are laminated Douglas fir.
"Hybrid" is "The offspring of genetically differing parents" from Merriam-Webster.
The bottom and lower strakes are epoxy bonded plywood and the topsides are cedar planks rivited to sawn frames and each other in the traditional manner. The plywood is sheathed and painted, except in the Hunter Bay boat it's bright inside, and the topsides are finished bright.
The BareFoot site is a bit chaotic, the above specs are for my boat, Ratty, a 20' ketch.
04-10-2006, 05:05 PM
How does the differing expansion between ply and cedar impact the hull? I've seen Gardner's plans calling for a solid wood transom on a ply boat, and (I think) vice versa -- but I've never heard of mixing the materials in the hull in this way. Sure looks pretty in the pictures, Ratty in particular!
Clinton B Chase
04-10-2006, 08:04 PM
Interesting thoughts...my thinking was that I'd love to build and use a traditional lapstrake planked boat if it weren't for the fact that I will be trailering and thus go in and out of the water frequently and probably not staying in the water long enough for the planks to swell and the leaking to stop. By the way, how long does it take for the planks to swell and shut off the water weeping in (assuming one does nice tight bevels)? I very much like a clean, dry boat on the inside, one reason I love glued lap. But the truth is I have been up to my ears all year in goops and glues and wouldn't mind doing a project without. I do not want to mix solid and ply planks. It would be all ply. I sm not a purist, but got into this through using boats...so I am into function as well as form. So, faux rivets don't bother me philosophically, but a few good points were made about having the added weight of rivets and the framing that makes it tougher to keep the inside clean. Rivets in a sheerstrake and nowhere else may indeed look weird so that is a point. So tell me...a 15 or 16' clinker peapod with quality cut bevels and evrything else...how much heavier would it be and hw much does it leak when put in the water?
04-10-2006, 10:19 PM
I'm trying to upload some images but it tells me I have exceeded my quota every time I try, I have reduced the images to about 35Kb but still keep getting rejected
04-10-2006, 10:25 PM
Lee, are you trying to upload them directly here? What you need to do is put them on a website then you just link them to this site. I use Imagestation but others use Snapfish or photobucket or one of the many web based photo hosting services. I took some pics of our Elf today, I'll dig up an old post and bump it to the top. :)
04-10-2006, 10:28 PM
Well I have managed to upload a small image but how do I put it in a post
04-10-2006, 10:32 PM
Lets try it the old way
04-10-2006, 11:03 PM
Glued lap plywood is a dry boat and really the best for a trailered boat. The Simmons is glassed on the whole bottom well above the waterline creating a watertight pan so to speak.Then the remaining side strakes are installed over that with glue and screws. What difference does glue make as to something else like seam compound or anything else? Use PL premium and pretend it is seam compound.
If you want it to look traditional,paint it with a brush and traditional paint and leave the brush strokes.
04-10-2006, 11:24 PM
I've bumped up an old thread with some pics of our Elf. Yours look so familiar.
On the impact of differing materials expansion; so far this has not been an issue, the joint between ply and plank is done with Sikaflex and rivets closely spaced. The plywood (almost) doesn’t move and the plank is solidly held by the rivets, no leaks. Also the joint is above the usual waterline and so normally at (high) atmospheric moisture content, but not underwater. The boats are in and out of water year round.
The method was first suggested by Richard and Quill at BareFoot Wooden Boats, but I doubt it's the first time it's been done.
That was part of the reason for arriving at this construction system, everyone was just tired of dealing with so much deadly goop. In this case it's epoxy and ply in the early construction stage, and after that just traditional boatbuilding with few bad smells.
This coming Saturday we'll be launching an 18' Mower dory built using this "Hybrid" method at the Silva Bay Shipyard School, one of four boats built over the past 6 months. http://www.boatschool.com/jan2006.php (http://www.boatschool.com/jan2006.php)
And I'm developing a new 17' Raid boat design for next year's Shipyard Raid using the same construction except with a double plywood bottom of watertight tanks.
All the best, Tad
04-11-2006, 08:03 PM
I'm looking forward to building an epoxy coated bottom/planked topsides boat for a personal project. Mine will be plywood up to the chine logs and clenched lap with a bead of sealant in the laps above. Walt Simmons has written about this method (the lapstrake part) in one of his booklets. I just need to find a source for good copper clench nails so the cleaning/sanding/painting problem can be minimized.
David, you and Clint' should wander over and lok at Dave Corcoran's Coquina. It's built that way.
I ought to say that when his picture was on the cover of WoodenBoat mag. he took his phone off the hook, because he was getting so many calls from Amaeur builders. So tread carefully!
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