How big a boat can built with glued lap construction ?

Discussion in 'Boat Design' started by PeterSibley, Feb 10, 2011.

  1. ancient kayaker
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    ancient kayaker aka Terry Haines

    Those old builders were incredibly ingenious, and let's not forget the tremendous strides made in design and construction well before the advent of modern materials such as ply and epoxy. They worked with what they had, which included old-growth forest products, natural crooks, no forest conservation laws, cheap labor and perhaps a local foundry but they had no objection making a boat lighter if it did its job better as a consequence.

    There is no lack of ingenuity today - and as with the builders of yore - we work with what we have. That might be good plywood, fantastic adhesive, expensive lumber and bronze from far away or cheap stuff from the hardware store down the road, and for some of us limited knowledge and abilities. This forum is full of new ideas some of which will make it and some perhaps need to be quietly forgotten.

    I am convinced that - given the material and labor situation we have today - those clever folk 100 years ago would have come up with construction methods that would be familiar to us. I know that one place I look for inspiration is the history of boating building, trying to see how old methods can be adopted to newer materials and imagining what could have been done if those materials had been around earlier.

    There is many a design that - as Bataan puts it -“has an ideal construction method” and a boat designed for heavyweight construction will not be improved by lightweight construction or vice-versa, but there are usually choices. Each builder has his preferences and makes his choice. I don’t understand why one would want to make any creation heavier than it has to be to do its job, certainly not to use up a piece of wood lying around however nice, but that’s just my view. Each to his own ... Peace!
     
  2. PeterSibley
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    PeterSibley Junior Member

    Hi , well the piece of wood isn't just lying around ,it's cut out and shaped as a keel .It's a 24 foot 9x6 yellow stringybark stick ,however I understand the reason for rejecting it .I am loath to do so but understand it may be necessary .If so I'll find someone to put it to good use .

    As for making a boat heavier ? There have been a very large number of heavy craft over the years ,most of which meet the disapproval of the light is best crew .Some of them are very good ,some not so .Weight doesn't necessarily mean slow ,in fact sometimes in a displacement craft it is a sure road to pushing though a chop or ghosting in fluky air .The lines Bataan posted are of a type that is old but has it's uses .

    There is a US built version of the same design ,''Corenius'',built in 1927 and still going strong ...and very well spoken of by all her owners as seakindly and very comfortable in a rough seaway .''Corenius '' is ever so slightly lighter and of slightly less displacement than Bataan's'' Marie Michon'' ,being 7.17 tons on a 25 foot WL and 28' overall .Both boats are successful examples of a boat that I think would be good singlehanders for our waters ,having primarily a non tiring motion ....one of the most important factors for a small singlehanded cruiser .
     
  3. PAR
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    PAR Yacht Designer/Builder

    Peter, I understand your desire for a "well founded", possibly very stout craft, but 100+ year old design concepts aren't necessarily the most "efficient" route to this end. I do understand traditional construction as well as modern and it even has a soft spot in my heart (the other half says it's rot, but what does she know). I've even owned a Spray that I finish up the traditional build on, when the owner lost interest.

    When I see a body plan like that of Marie Michon, I see many things, but most are undesirable. I see a huge amount of wetted surface, which translates into displacement, which translates into build cost and weight. On one hand this can be a useful thing, particularly when the weather gets bad, but most sailing is done in reasonably nice weather, so it's just along for the ride 90%+ of the time. I see very slack bilges, which means you'll sail her on her ear, to get anything out of her and considering her weight and ballast ratio, requires more structure to support these types of dynamics underway. I see a long, "draggy" built down appendage that will surly require assistance in a tight anchorage when attempting to maneuvering among a crowded mooring, though does protect the prop well, but will be all but imposable to turn and back up at the same time.

    In my mind you can have your "cake and eat it too" in regard to a comfortable sea boat that can easily cope with anything your area can toss at it, plus not need 7 knots of wind just to get away from a dock. With the exception of small craft, you can have more then enough displacement to make the boat comfortable in a sea way, yet nimble enough to spin crisply on her well defined appendages, in a tightly packed anchorage or short tacking up a channel. In fact, it has been this trend since the end of the 18th century.

    These progressively lighter boats aren't overly light, just more refined. Let's use George Buehler as an example. Most are familiar with his work and concepts. His Dragonfly design is in keeping with his massive scantlings schedule and long and lean sailing ideas. She has 1.5" planking on 3"x6" frames, which are placed on 12" centers. The keel is a 10"x12" laminate, the chine logs are 3" thick, the deck 1.5" of plywood over 2.24"x4.5" beams, the floors 4" thick timbers. Not a weenie boat by any stretch of the imagination, but a very stout, workboat like scantling list. She has a long deadwood assembly, which means she'll handle like a freight train, but this could be revised to separate the appendages for better handling. In spite of all this, she's only 16 tons on a nearly 43' LWL. As a result her D/L is very low for a Buehler design (217) and though I think this it a bit too low for your needs, it proves my point, in that even a stout, massively built 50' yacht, like Dragonfly can employ the numbers, most every living designer would suggest are more conducive to sailing enjoyment and maintenance.

    Personally I think you need a modern(ish), moderately heavy displacement boat, with well defined appendages that are optimized for your rig preference. To this end, I'd recommend a D/L in the 260 to 290 range. 260 if you're more likely to be in moderate weather, 280 if you expect the Tasmanian sea to stomp on you regularly. With both of these D/L's, you'll be comfortable and secure, without the violent motion often associated with modern sailboats. I designed a small sailor for your area few years ago and after studying the patterns, you have a nasty little puddle down there, but not unlike many other places in the world. Given this, your SA/D should remain on the moderate side of the coin, say 17 or less, though this does depend on the rig a great deal. 17 on a divided rig of moderate aspect, maybe as low as 16 for a single stick with some height. I'd recommend U shaped forward sections with a fairly stiff, nearly flat floored midship section, followed by V sections aft. This will offer the best roll motion and still have good flow characteristics. Keep the over hangs fairly short, even though this is a boring look, it's a more comfortable and safer one, in a nasty lump of sea. Rather then a deep fin keel, I'd opt for a "3/4" fin keel, which elongates the ballast casting enough to make the ride less harsh and is usually far enough aft to protect the prop, maybe even a shoe attached to the skeg, for more protection.

    The styling can be anything you like, from a 16th century warship to a 1920's art deco. The advantage of the modern hull shape below the waterline is better preformance, better maneuverability, better light air ability, higher stability, both initially and ultimately, lower build cost because of less materials and labor.

    As Terry mentioned, I too have repeatedly looked at hull form evolution. The first thing you'll notice is the ends got narrower and the displacement curve pushed aft. Then the bilges firmed up amidship and the forefoot progressively became shallower. This was followed by the aft quarters also "firming up" and straightening out the buttock angles. Then the deadwood assembly became more and more hollow forward, until it was removed entirely (actually moved inside the planking) in favor of just planking as the cutwater. The narrow, deep cod's head shapes were replaced with shallower hull forms, of considerably less wetted surface and most importantly with the displacement shifted to most sailing benefit. Then the appendages became refined, separated and more refined (this is still occurring). A 40,000 pound yacht uses just a sliver of a fin and a similar rudder, though still manages to sail the roaring 40's with regularity. Now, we're getting to a point where the hull form is just a container to hold the crew and gear, while the craft is foilborne. I can easily see this as the "norm" in 100 years, with old farts like me looking back and fondly remembering the good old days when we still had wire stays, manual halyards and you actually steered the boat BY HAND!

    I don't suspect this last bit is for you, but don't hold your breath, because it's happening now. Have you looked into the Bob Perry type designs? Again the topsides and rig can be anything you want, but the fairly high displacement, cruising hulls with good attributes under the LWL are worth considering. These "spirit of tradition" designs are the big thing now. I just did a Friendship sloop that looked every inch a Morse built classic, unless you happened to see it hanging in the slings of the travel lift, where her divided, foil shaped appendages and well shaped under belly, stuck out like a sore thumb. It used metal floors and composite backbone, with a strip planked hull, birdsmouth mast and an aluminum gaff! You'd never know it to look at her, but she'll out point anything in her class and she'll easily out maneuver a full keel version, which was the whole point of the design other then the cost savings that come along with less material and boat parts. Her D/L is 194, as she's a 3 ton boat on a 24' LWL. This is a little light for your needs, but his sailing area is light winds, so a reasonably light boat was necessary to offer some level of preformance.

    I guess my point is you can have your cake and eat it too, but it's truly false to believe that a 100 year old hull form is any better equipped to handle the sea. Most of the time, when you plug these designs into VPP you come up way short of a modern hull form. More importantly is the stability curve, which more often then not, isn't what most folks would expect from an off shore yacht, let alone qualify for a cat A rate. So, if your old school design needs tweaking, just to get the AVS to an acceptable degree, then I'm suggesting it's time for a fresh "interpretation" of that design.
     
  4. PeterSibley
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    PeterSibley Junior Member

    Here's an image of the lines of ''Corineus'' ,I'm absolutely sure she is not to your taste , but that's alright .I'm also pretty certain you didn't open the link I provided ... but I guess you could have had you been interested .

    [​IMG]

    I'm sure the boats you like suit you perfectly , but the one in the link is my design. Ed Burnett ( who is a very competent designer of displacement yachts ) gave her his seal of approval and had some considerable role in advising me .She will be fine .Not your taste ? Such is life .

    Thank you for your lecture on hull development ,strangely enough I did know that .I also know precisely what I want from a yacht .I very much doubt it is the same as you .

    BTW ,she will heel to 15 degrees then set up nicely and carries 90 square foot of sail per ton .Full headroom on 5 foot draught with a 12'' high house . .
     
  5. BATAAN
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    BATAAN Senior Member

    I know modern, scientifically developed hull shapes perform much better under sail than the traditional types in windward ability, ease of tacking and close quarters maneuvering. But the factors that influence design go beyond the simple sailing stuff.
    I also know that fat old BERTIE, a modified and developed SPRAY, has weathered bad gales for days at a time lying a'hull with no attention and giving great comfort below, can be reefed to any degree in 90 seconds on any point of sail by one person, will steer herself dead downwind without a vane indefinitely, averages 100 to 125 miles a day at sea, can be run up on a tidal beach and laid on her side for a scrub, and is so strong she has crushed anything she has hit or run aground on. The 1000 sq ft Chinese main along with headsails and mizzen makes the rig large enough we don't use light sails much and still sail, tack and have steerageway when you can barely feel the breeze.
    The anchor gear and windlass and bow are stout enough to rip the pilothouse off a sunken steel wreck we were foul on in Mexico and lift it to the surface. Replacement parts would require a tree and an axe and a little time.
    The modern boat is quite a bit faster, can make (uncomfortable) passages to windward that are impossible for us without motor sailing, has a low maintenance structure, but is very difficult to haul out without a modern boatyard facility because of it's finned and delicate underbody appendages. The efficient, highly stressed rig requires light weight very strong parts, which are not cheap. This type of rig is subject to total unexpected failure if not properly inspected and operated. The sails generally are too sophisticated to be home made, so again a specialist gets your money, and again in a few years because the cloth is light to enhance light air performance. The owner of the type is often in love with systems so wiring, plumbing, antennae and tanks get complex and useful, but require more money and maintenance.
    These are two different kinds of boats we're discussing here, for different kinds of owners and different purposes.
    There is no "best" design for watercraft because the job required designs the craft, not the other way around. I needed a boat big enough to raise my family in, be safe at sea under any conditions, to last at least 50 years, to cost $15000 hull and deck and be built quickly, in the open in bad weather, by one man with available and proven materials and techniques. These things designed my boat rather than hydrodynamics and performance curves and ideal material specs, none of which affect the requirements above really.
    It's fine to shell out lots of money, buy or have built a modern yacht that sails like a Ferrari, and go out and enjoy it for an afternoon or a circumnavigation, just don't think it's the only or the best boat. Some of us are not rich so we do it the old, cheap way, with local woods building antique designs suited to the traditional materials and techniques and well proven for centuries at sea.
     

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  6. PeterSibley
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    PeterSibley Junior Member

    I'm afraid I get a little peeved when someone takes it upon themselves to tell me I'm wrong in my choices ,without reading a link provided (that explains said choices and the process involved in making them ) and then assumes I'm ignorant of other possibilities available .

    There is a certain lack of politeness involved .
     
  7. PAR
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    PAR Yacht Designer/Builder

    I've read your WB thread and am aware of your choices. I just don't think revisiting designs that haven't a lick of yacht design evolution in a 100 years or so, is the best approach. It's like selecting a newly designed Model T and forgetting about anti lock brakes, air bags and built in crush zones that are incorporated into modern designs.

    The only real point I'm attempting to get across other then dispelling the myths (like modern appendages being delicate) is that you can incorporate the majority of yacht design revelation and evolution into a wholesome, world cruising vessel that does everything a modern boat does, except looks like it floated out of the 19th century.
     
  8. PeterSibley
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    PeterSibley Junior Member

    1927 actually .I strongly suspect that certain types have been overlooked for purely financial reasons .Weight ,as you say is material ,but when you live in an area with plentiful good timber that need not be a determining factor . A 25 foot WL boat that can sail 100 mile days is entirely adequate for my uses .We have wind here and lots of it .

    I really can't understand your dislike for something that is not modern .It does all the client desires and satisfies his aesthetic sensibilities . Some people actually like the aesthetics of earlier eras ,personally I'd be more than happy with a 27 Chev , but not it's brakes .Fortunately for this discussion boats don't have brakes and those accessories that might act as such are portable .

    Design evolution ? That particular design was pretty well the end of an era , heavy displacement and a slow easy motion at sea .There is no comparison to a modern light weight craft .

    My main requirement was an easy ,non tiring motion .I think I have achieved that .

    Did you by any chance notice that when reading the link ??
     
  9. rwatson
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    rwatson Senior Member

    I had an interesting experience in the world of traditional boat design and building this week. The discussions here reminded me of the wide variety of boat building methodology and personal values I encountered.

    So, by way of tedious explanation in case you have nothing to watch on tv, I called in at the local 'wooden boat' association this week, and was pleased to see that someone had done a wonderfull job of creating a scaled half hull design of a ~50ft 'Coastal Trader', and someone said excitedly 'Thats what we are all going to build'

    I should have thought before I asked 'Have you done the weight table and righting moments for it yet ? ' They looked at me blankly, and said 'It will be all right, he has done a few of them before'. I didnt ask for other 'nice' things to know like the planned weight, sailing geometry, sailing performance, hull speed and a dozen other things that boat designers like to work out in theory.

    Of course, there had been no formal calculations and drawings, either on paper or pc. They are just going to loft the full size frames on the shed floor, and start building.

    Fifty, maybe Thirty years ago, that would have been the accepted technique because it had mostly worked before, and frankly, without computers, the calcs would have been just too mind boggling.

    But I had also visited the head surveyor for commercial boats in Tasmania this week, about my project, and discussed the requirements for craft that were to take paying passengers, and discussed the formalities. He had said ' I am glad you are doing all the prep work before asking for accreditation, so many dont'

    The funny thing is - thats what the 50 foot coastal boat is intended for. But they plan to build it before any 'paperwork' is done. That might be a recipe for problems, but more importantly, maybe its a recipe for 'lost benefits', like accreditation, sailing ability, weight optimisation etc etc

    Of course, once you start a design, and have it on pc or paper, there is that wonderfull 'opportunity' to tweak, optimise, re-invent etc. But that all takes ages and a lot of emails and discussion. What a tempation to take that half hull out to the shed with a stringline, carpenters pencil and building square, and just start the bloody thing! Hell, probably 2/3rds of the boats in the world are started like that ,and a lot of them do the job.

    And if the building methodology isnt diverse enough, there is the differing design values. In the same 'wooden boat' shed there is a little 22foot yacht undergoing restoration. Its all diagonal planked, lovely lines and great workmanship. There is quite a bit of work gone into her already, but I nearly had my throat cut when I said 'its all a waste of time'. My reason for saying that was that I had been up in the bow chopping out rot in the stem, and just to get through the tiny cabin, I had to be a contortionist - its just so small !! What the heck would someone do with a yacht with so little usable space. The 'whole reason for being' of this boat (to provide comfortable shelter on the water) is just a big fraud.

    I reckon that 80% of a boats appeal is in the mind of the builder/owner/designer, and the reason for designing/building boats has very little to do with solving living, travelling or exploring criteria, but just the urge to build something, to create and solve problems. How about that gem of a saying earlier in the discussion "and very well spoken of by all her owners ". Well, who one earth would admit that the boat they owned was a pain in ***, and very few would admit they made a mistake after they sold one. But just the fact that the boat was sold at all shows how usefull or not it was.

    I suppose then that the people with the most 'authority' on what makes a boat 'right' are the ones that actually use them a lot - its the real proof.

    Mind you, I wouldnt start a boat until I had thoroughly investigated all the options in theory first.
     
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  10. peter radclyffe
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    peter radclyffe Senior Member

    quote
    Mind you, I wouldnt start a boat until I had thoroughly investigated all the options in theory first.


    Peter Sibley is one of the most thorough people i know of
     
  11. PAR
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    PAR Yacht Designer/Builder

    I can think of many modern designs that have easy motion in a rough slosh. By modern design I don't mean shallow canoe bodies with spindly fins and spade rudders. These are just what you don't like, nor do I for a real cruiser.

    Jay Benford, Ted Brewer and many other designers have stock designs that are well balanced (like Ed's hull form) so they'll steer easily and offer good motion characteristics. It's not that I dislike older designs, it's just that I dislike how they handle without the evolution of the 20th century.

    I agree that many of these older types are discounted just from a glance at their BOM or possably from perceived notions of their preformance envelope. I'm moderately familiar with Ed's work and if this boat is typical, you're not going to need much epoxy, possably none at all. The same would be true of the other elements of the project, which in some ways can be a good thing.

    I look forward to your project coming to fruition. There's not enough of this type of build any more and I'd appreciate a well documented one (lots of pictures), as well as many others here too I'd guess.
     
  12. PeterSibley
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    PeterSibley Junior Member

    Thanks Peter , nice to see you here .

    Rwatson ,that would seem a fairly idealistic route to take for a commercial venture ! in my case I'm reasonably happy with ''parametric analysis ''.Looking at a lot of successful boats that have been built within similar parameters with a small non commercial boat .Were I trying to design a new type ,something outside the well proven I would be guaranteed to submit my ideas to a NA .In this case I was lucky enough to have Ed Burnett take an interest ,despite it being a very ordinary project.
     
  13. ancient kayaker
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    ancient kayaker aka Terry Haines

    Peter: you will exercise your own choice regarding design, of course. Good luck with the build and please keep us posted as you progress. Lapstrake should make an attractive and durable boat. I did a little research on planking design lately and the lining off seems quite an art. Iain Oughtred's book on Clinker Building gives some guidance. What will you do about the early advice you received on choice of ply, impregnation, glassing and such like?
     
  14. PeterSibley
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    PeterSibley Junior Member

    Thanks Terry , yes ,I will very carefully line out the laps then look at at therm for a long while ! Nothing looks worse than a pinched up clinker job .
     

  15. ancient kayaker
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    ancient kayaker aka Terry Haines

    A half-model might be good for eyeballing the laps. It is hard to tell from a three-elevation drawing and there is a lot of work involved in preparing a good perspective view. Most hull design software does not handle lap changes easily. Sheer lines are also difficult to judge, I have read, although I have had good luck so far using conics and splines which are easy to model on a computer.
     
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