How big a boat can built with glued lap construction ?

Thanks mate , a few interesting thoughts .I'll see if anyone else comments on this .

 

S/S screws or nails disolve if sealed off from any air with epoxy. There is a name for this effect but it is to late for me to find it. Never seal of S/S screws or nails from air. Found it.......In a Boatbuilder Connection thread a while back, it was pointed out that stainless will corrode terribly and possibly completely in the absence of oxygen (needed to oxidize and therefore passivate the surface). This did not sit well (not fitting with common sense to me). That coupled with a recent thread on rec.boats.building gave me the drive to find the answer. In addition, over the years I had found a number of bolts and screws that had oddly "necked down". I had blamed this on vibration and mechanical erosion, but with some misgivings since the threads were still present but at a reduced diameter. With further research, a light (finally) went on and I realized what I had seen was the corrosion of the metal.

Stainless steel is "stainless" due to an outer oxide layer forming which resists further corrosion. If the oxide layer is damaged or abraded, then oxygen from the atmosphere will react with the newly exposed metal to form a new oxide layer.

If immersed in liquid containing chlorine or other ions (courtesy of salt water, fresh water impurities, and solutes from the wood itself) in an enclosed space, the metal is attacked. The oxygen becomes depleted from the solution before the other (attacking) ions, and the metal erodes quickly and sometimes completely.

Because of this, bronze is definitely

 

I'm sorry you've had such a bad experience with lapstrake hulls, but this isn't the problem you're making it out to be, other wise Thompson, Owens, Lyman, Chris Craft and all the others that have had excellent service live from their lapstrake models must be just lucky, right?

The only catch point for moisture in a lapped hull is the lowest point of the sweep on each strake. This location often has a saw kerf or two in these locations to drain off accumulated moisture, though honestly I don't see the need for this treatment as all that necessary. No more so, then having a bilge pump remove every drop of water from the bilge.

3M-5200 in the seams of a lapstrake is against what all lapstrake builders do, in spite of what "Reuel Parker" might have said. Chris Craft was one of the first to employ this technique, Lyman was one of the last to jump on the goo'd seams bandwagon and all found that polysulfide (like the stuff used in deck seams) was far better then polyurethane (like 3M-5200). I've personally pulled hundreds of nearly continuous yards of cured polyurethane bead, out of the seams of lapstrakes and carvels over the years. It releases easily and you end up with a handful of rubber like rope. The only occasion I've seen polyurethane work effectively (under the LWL) is under pressure during the full cure (several weeks). This can happen in the hood ends as described above, but not in the laps (not enough pressure).

Stan, stainless can break down, but it needs a few things to happen; moisture, a specific temperature range and captured oxygen or free oxygen. Technically, you're right, if buried in wood, it will break down quickly (moisture and O2), but if buried in epoxy, neither type of oxygen can get at it, so no crevice corrosion or oxidation can occur. I've disassembled boats that have had good stainless and bad stainless buried in both plain wood and epoxy coated. Two things have been generally found, first the good stainless (316 and 316L) was much more tolerant of crevice corrosion, then 304 and the epoxy buried stainless look pretty damn good, most looked new. I recently did a repair on a transom I installed many years ago (about 20). It was backed into buy a truck and needed some repairs. The stainless screws I used to tie the three plywood layers together where still there (I now remove them) and 95% of them were in near new condition, each having been inserted into an epoxy filled hole as they were driven home. The few that showed signs of corrosion had been nicked by a drill bit, as I drill holes for putting the engine and other assorted equipment on the transom (one of the reasons I now remove all the fasteners). After nearly 20 years, and nearly perfect 316 fasteners, I can assure you that epoxy is an effective moisture barrier for crevice corrosion.

 

PAR ,could you comment on the Green high lighted above ?

 

Where seamanship and engineering meet

Can't disagree with anything of the above.
And, yes, of course, going for salmon in conditions you described is stupid.
However, the failures of this kind do excellent service for innovative builders, structural engineers and Class Societies: if breakages occur at random locations of hull (or whatever), than the boat design and build is sound; if breakages occur at some specific parts, like splitting hull along the keel in your example -this is the weak part and need to be redesigned, built differently, etc..
Please do not understand me in the way "the improper boat let down good people".
What I mean is "whatever the level of stupidity or arrogance of guys who vent for a death trap, there are lessons to be learned, both in seamanship and common sense, and boat design/build/engineering".
In this case, ignoring the question if structurally more homogeneous boat would have saved them or not, lesson in design/build methods is there, and we better learn in.
That's it.

 

The first comments about a T shaped backbone are not understandable. There are many ways to make a keel, each has advantages and disadvantages, none being best or better.

I would never bed a lap in 3M-5200. If considering this, you should just use epoxy and stop screwing around with sealants. Epoxy solves the problem that sealants attempted to fix, which was leaking laps. Interestingly enough, I've repaired polysulfide laps in Chris Crafts as old as the late 1950's, that still had, water tight seams on their original planking.

The choice (again) of using epoxy, means you have to encapsulate the pieces (planking, frames, etc.). Anything less then this means you are using epoxy as an expensive paint, not a waterproof coating, because only encapsulated parts become moisture stable. So, if you elect to 'glass lapstrake planking (not as good an idea as you'd think) you have to fully encapsulate.

As to using 'glass cloth or high elongation fabric (Dynel, Xynole, etc.), well the two different types of fabrics have hugely different physical properties, so you have to be real careful which you employ. Anyone that's owned or repaired a lapstrake can tell you where the majority of damage occurs, which incidentally isn't where the 'glass or fabrics are.

As to what appears an assembly list or procedural arrangement for strake layout, well who knows here. There's really only two ways to build a lapped boat and both require a similar assembly approach, with the only planking differences being glued or fastened seams. Repairs are a different story. There have been times I've had to treat each plank as a shutter, just to make things easier on me, which is completely different then a new build.

I completely disagree to the ease of repair on an epoxy/fabric sheathed lapstrake plank, compared to just a plywood or solid plank. Restoring epoxy and fabric covered surfaces is a much more work then scarfing in a repair on a traditional or glued lap build. Comparing plywood planking with solid wood, particularly woods like cedar, which tend to split just by looking cross eyed at it, just isn't a fair comparison. Plywood holds fasteners better, glues better, has considerably more cross grain strength, etc. Plywood is the sole reason that lapstrake cruisers took off after WWII. If it wasn't for the ability to use a dimensionally stable material (plywood) and their eventual sealed seams, lapstrake hulls would have been just another build method, that went the way of batten seam.

As to fitting the hood ends (or any other structural element) less the tight, as mentioned, well I'll just let that statement stand for itself.

As to the comment about a 45 degree piece glued to the top of a strake to ease dirt and moisture collection, well again it's tempting to just let it stand for what it is. If you look at a set of well drawn plans for a lapstrake build, you'll notice the laps aren't cut at 90 degrees to the face of the plank. On the outside of the plank the angle is less then 90 and on the inside the edge is more then 90. Naturally, in some areas of the boat, you can't "back cut" the tops of the inside lap with enough angle to permit drainage, but you can in most and those areas just aft of midship where the moisture might collect can be heavily rolled or kerfed, which solves any issues.

Part of the problem with this thread is the mixture of glued lap techniques with that of traditional lap. The two aren't interchangeable and generally don't mix well, plus they rely on wholly different engineering techniques to produce a non-leaking boat.

 

Agreed . That came from me wanting to use the keel timber I have already .It's an excellent piece of timber and the idea of substituting fir for it is unsettling .It will never rot but the fir will .....a lot sooner .My problem is my attachment to trad methods , at which I am reasonably proficient .

I'm not sure what I want to do is achievable .

 

Mixing the two processes just isn't advisable. If you have a traditional build, you're married to it. If you have modern build, you can incorporate some traditional elements, but it's a belt and suspenders approach and could bring more trouble (and weight) then it's worth.

Big timbers are nice, but more often then not, overly heavy for their structural role. I'd much rather have a built up element then a big hunk of something, as it makes repairs easier, it's usually lighter, which you pay for during installation and in the preformance envelop.

 

Agree that sealed SS lasts well like the epoxy-sealed wood it fastens. I dip them in activated epoxy before driving also which seals them and the hole they are in as part of a system, not used alone.
Problems happen when used in other ways and they live in still salt water and no oxygen. Then, life is shorter than galvanized due to crevice corrosion. Same thing happens to SS or Aluminium tanks where they sit on mounting blocks and are wet with saltwater.
The Polysulfide (we put PS mixed by the gallon and shot in with air tools in a lot of deck seams in the 70s through the 90s) or shellac and gauze/anything but dry wood/whatever, was only intended at the one ply/plank lap at the broad, all the other plywood plank laps should be glued by the book with WEST and Laminating additive, the laps in and out coved with WEST and filleting compound, a little more at the low point of the sweep, not put together with rubber, that would be stupid and require heavier fastening too. The shell would be quite stiff, especially building with 3/4" ply, giving almost 1 1/2" of thickness at the laps. I don't think I was clear in my earlier post.
Stem rabbet of 'glued shell' cannot be caulked like plank because it's end-grain plywood, so some sort of rubber is necessary here. Likewise at the transom, which hopefully would be mitered to cover the endgrain of the ply if timber, or best if laminated from ply like the shell and sheathed with it.
Polysulfide may be much better than 5200 in this place, I don't know as I have much more experience with oakum and cement below the waterline having only used PS for decks as a yard worker and 5200 to bed fittings when ordered as I don't like it much.
I agree it's difficult and experimental to mix two well developed building styles and expecting something better than either used alone.
Plank and frame is the cheapest, quickest way to get a one-off build of conventional type.
Glue boats are for things you can't get light enough and strong enough to work any other way, like racing, or that must remain dry when stored ashore.
The shape is very easy to plank and if I were to build one of these it would probably be conventional 1 1/8" thick carvel with 1 1/4" square steam bent white oak frames on 12" centers, fastened with copper rivets, and, if bidding in my own town, would say 90 days labor in plain finish for two skilled men.
In the end, even though it's difficult to get planking material sometimes, it's often cheaper and longer lasting, with fewer hidden headaches just to do it the old ways.
The only problem with that approach in this case is the requirement for dry storage without drying out and leaking, which rules out regular carvel or lap.
I would recommend strip build with sheathing over a laminated backbone and stem as best way to do that job, but we are exploring some interesting areas here.
With a heavy timber keel, this too can dry out and check badly when dry-stored, causing leaks that are difficult to stop totally.

 

This doesn't work that well on stainless fasteners. The pilothole will usually wipe the threads clean of any epoxy, before it seats home. The only way to make this work is to drill an extra deep pilothole and squirt epoxy into the hole, before inserting the screw. This offers a place for the epoxy to live as the screw is inserted and when the screw is driven home, this pilothole/epoxy well is pressurized, which distributes the epoxy throughout the hole and surrounding wood fibers. Standard pilothole depth for this technique is 5% longer then the fastener.

There is no reason to caulk a "glued shell" rabbet. You glue the damn thing, because this is the method. Mixing methods just invites problems.

This is complete contrary to what every designer and most experienced builders have found. The reason is simple, bulk, weight, mass, displacement, huge timbers, etc. all cost money. It costs a lot more to make frames, floors, stringers and hang thick planks, then it does to skin a hull with a monocoque wooden shell that has no frames, floors or stringers. You pay for the parts installed, you have to carve and fit these parts. If a modern build is used, you have 2/3's less parts to buy, shape and install, plus you're only paying for 1/3 of the materials of the traditional build. If this wasn't the case, then we'd all still be building boats from massive timbers with 2" planking on 40' yachts that wight 20 tons.

I'm not sure where you're getting your information, but this is (again) directly contrary to what we know as true. You know why you need 2" thick planks, on a 40' yacht built in a traditional fashion? Because solid wood planking doesn't have the cross grain strength necessary to keep from splitting. It's flatly absurd to suggest, that glued boats are heavy and must remain dry. You're kidding yourself in a George Buehler like fantasy. This might have been true in the 1950's but it's time to wake up as over a half a century later we're building 40' "glued" yachts with single digit displacements.

I designed and directed construction of a 42' sailboat several years ago. She was 37' on the water, a smidgen under 11' in beam, fin keeled, carried nearly 700 sq. ft. in working sails and displaced 9,300 pounds! She's a racer of course, but she's also been afloat ever since, hauled in the winter naturally, but other wise ready for action. Try that with any traditional method you like. I don't care who the designer is, they can't do it in traditional methods. Again, you pay for the materials that go into the boat, so a light weight traditional build at 20,000 pounds is a much bigger lumber bill, then my less then 10,000 pound modern design and the best part is I didn't go nuts trying to make it ultra light!

One of the biggest reasons we employ these modern methods, other then lowering the displacement (which of course lowers costs) is to solve the usual traditional issues, such as leaks, drying out and routine maintenance. Modern methods don't need to be refastened, they don't need to be re-caulked and they don't suffer from seams opening up during storage.

In fact, the best thing you can do for a traditionally built yacht, is pull it's traditionally built deck off and replace it with a plywood deck, simply because it doesn't do what traditionally built decks do, which is leak!

This talk of antique design, monolithic monstrosities, of hideous hull form, as if they are better and superior then a modern wood/epoxy build is utter nonsense. There's very little about these old designs that can't be improved on. History and reality have born this out repeatedly. Fasteners replaced lashings for a reason. Adhesives replaced fasteners for a reason. Wire replaced hemp for a reason, plywood - solid wood, etc., the list is endless and you can bet on two things.

First there will always be those that look back and speak of the "kinder and gentler times" when men were men and boats - boats. These are the folks longing for the "good old days" when you could leave you windows open and the top to your car down without worry. They're kidding themselves of course, because they forget these "kinder times" also meant you had no Miranda rights and the cops would just beat a confession out of you, if they so desired and if your 15 year old sister got ***** and was pregnant, uncle Harry would give her an abortion with a coat hanger, because it wasn't legal to get one in a hospital. You know, the "god 'ol days". The other thing that is true is that those who actually study and work within the industry, will constantly look for improvements in speed, handling, safety, convenience, security, build costs, reliably, repairability, maintenance, etc. There's no stopping this looking forward portion of the industry, which fortunately greatly out numbers those that continue to look back. Personally, I'm not looking back at the cat gut they used for sutures, but do prefer the super glue they now employ and am quite grateful for the advance.

 

Whew, not sure how we got to **** and coat hangers, I'm just trying to help some boat thoughts. I'm not a Master who knows absolutely everything like you, just a journeyman boatyard guy who repaired anything wooden that floated in the SF bay area in many yards from 1969 to 2002.
That means very light construction of all types like folkboats, IODs, Knarrs, not just the heavy, money-making things like tugs, charter schooners, barges, fishboats, you disparage so strongly.
I know very well the weaknesses of wooden vessels and that's why I used epoxy to fix them whenever it was appropriate, like repairing tiny frames in place in Dragons or replacing a curved transom on the railway overhanging the high tide with no shop to work in. Glue boats are great. I love them. I want a Nigel Irens ROXANNE as my dream ship.
I'm not sure who you're arguing with but I wish it wasn't me.

 

The answer is your description " hardwood timber , dry ,straight " - very few straight bits go into a boat - you have to curve them.

Sure, you can steam them, but then you encounter the vagaries of a natural product, faults, imperfections, knots etc, and steaming is no picnic for hardwood.

It is so much easier to slice them, and build up a curve with epoxy ( which isnt going to delaminate in your lifetime or the next).

If you come across any cranky bits (knots that will rot, faults that will crack) in the sliced up wood, simply chop them out, and use the rest of the plank.

Finally, a laminated beam is much stronger than the same size wood that has been steam bent, as fibres have had to be compressed and broken in the bending process, even with steam applied. This means you use less timber to achieve the same strength, and that is good in boats.

 

Never mind Bataan, I thought Par made some great points, but I think a lot of it wasn't so much just at you, but for all those who might have intimated that carving big bits of wood produced a better boat than joining small bits ( like my comments on laminated beams )

I thought the whole philosophy that things have been improved and made better in this age was right on the money - for boats and knocked up kids

Sure, you have to do it right, but I think that we can produce longer lasting, tougher and better performing boats and everything else from the more modern techniques and materials.

Mind you, you have to take your hat off to the old guys who had to take almost raw materials and cunningly fashion them into a workable craft. It was a great example of ingenuity, skill and tenacity that we dont seem to have as much of in these 'enlightened' times.

 

Any particular boat has an ideal construction method.
A modern cruiser/racer with an aluminum mast and tall rig is not suited to plank on frame or any other method than glued laminates of some kind, either glass or carbon fiber or wood, bonded and filled with various products. Most modern designs sail well, within a narrow range of displacement for the most part, and are wonderfully durable when properly built of the designer's specified materials.
The objective often seems to be lightness over all else including puncture resistance, grounding and squeeze, load carrying etc.
That's one class of boat.
Then there's the boat that has to take grounding shock combined with gross overloading, neglect, poor handling, collision, squeeze in big raft ups, and be repaired quickly and cheaply, in other words, your average work boat.
Glue boats are not seen in the commercial fleets here in the Pacific NW, but many old wooden vessels are still making money. All the replacements are steel or aluminum. The larger vessels in the sailing charter fleet seem to be wood or steel. I like glue boats but as either durable heavy work skiffs that can be neglected and are easy to fix, or light displacement racer/cruisers used as such.
If building a heavy displacement boat for greater capacity, stability and room or some other use than yachting or competitive racing, there doesn't seem to be a huge advantage to glue, other than much easier maintenance.
I don't know about 'carved' timber, I never carved one but used the Shipsaw and set up and framed this 23 ton boat single handed in 30 days. She has been smashed into docks (oops), rammed, knocked down and many times aground in iffy places while exploring. The glue boat would have suffered where this one just gets scratched paint, and the man hours and dollars per ton to build were very much cheaper.
I needed a big boat because I had 3 kids to live in it, I needed a cheap boat because I had no money, I needed a durable boat because I didn't want to repair it. If I went for a glue boat I'd still be planning and drawing like so many I have known over the years trying to build the perfect boat.
I built an un-perfect boat and I sail the pants off it every chance I get.
It has worked out so far.

 

PAR, you apparently know a great deal about glued construction sir , but you have absolutely no idea what design parameters were chosen for this design .If you don't like ''antique design '' and are not sympathetic from the start you are the wrong man to ask .

Some designs are supposed to be heavy ,there is merit in that and a completely different feel to the boat .Speed is not the objective , comfort in the Tasman Sea is .This may be at odds with your own choices , but then I'm not choosing for you am I ?

If by any chance you ARE interested in the design and why it is so ,I refer you to this thread
http://forum.woodenboat.com/showthread.php?97232-A-discussion-....-quot-Marie-Michon-quot
where the design process and the parameters are discussed at length .If you would then like to assist I would welcome your input .