How big a boat can built with glued lap construction ?

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

  1. Steve W
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    Steve W Senior Member

    To answer your question, "How big a boat can be built with glued lap construction" The late Peter Spronk designed and built a series of large catamarans up to about 75ft in length in glued lapstrake plywood. They were quite beautiful and were used in the daycharter trade in the Carribean in the 80s.
    Steve.
     
  2. BATAAN
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    BATAAN Senior Member

    MARIE MICHON has always been on of my favorite designs and I'm a SPRAY owner. Glued lap works well in ply but the trick seems to be scarf the planks full length on the bench then sheath them both sides with Xynolite (sp?) cloth and epoxy then hang them on the boat. This makes the ply well sealed, puts two layers of cloth in the lap and strengthens the whole thing nicely. Ruell Parker's Pilot Schooner 28 is built this way and I watched two of them being fitted out 90 days after the keels were laid so it's certainly an efficient way to build.
    If I built the MM it would be cold molded the way I was taught by New Zealand builders: at least 5 diagonal layers of 1/8" planking all at 45 degrees to the keel for a 7 tonner, sheathed with cloth and epoxy and either built on its interior or simply over a male mold of ribbands. I saw two guys build a 40 footer's hull in a week this way.
     

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  3. PeterSibley
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    PeterSibley Junior Member

    Thanks Bataan , I can't seem to find a source of veneer here in Australia and sawing it myself is not on ! A little bit is OK but the amount required for a boat this size is intimidating .

    I will have a look at the Ruell Parker book though ,I have a copy here .I intend to scarf the sheets together to full length and then cut planks out on the floor .I'm interested in the glassing first idea but it could complicate planing lap bevels in place !

    Is there any chance of getting a scan of the text pages containing the MM lines ? I have Cooke's book ,''Cruising Hints'' but it's the wrong edition ! No MM .I saw a tiny bit of the text on the link I posted at the top of this one but not enough to read it all .
     
  4. BATAAN
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    BATAAN Senior Member

    These pics of BERTIE (see SPRAY thread) in build I've included because it shows a bit of the HERMANAS Y HERMANOS in the background. She is a SPRAY type with lapped Port Orford cedar planking and sawn PO cedar frames, glued futtocks and joggled, all copper-fastened. I was delivery skipper of her when she sold and we went through a really vicious gale off of Cape Mendocino in CA. The laps definitely channeled air the length of the boat at speed and you'd see lines of bubbles in the wake at every plank edge. When running a breaking bar, she'd squat and suddenly accelerate down the face of a steep wave and out ahead of it as the laps grabbed air. BERTIE does not do this.
    The lines of MARIE MICHON are in a 1927 English yachting magazine at my home. I am far away on a job but will be back there next week and I'll try to accommodate.
    Fitting glassed lap bevels- I did some research this time-you don't-you cut a rabbet on the inner lower edge of a plank to loosely engage the upper outer edge of the plank below and make the fit with epoxy and the proper filler. This also positively locates the plank in place when hanging it, no sliding around. No cloth on rabbet, fasteners are SS screws buried and sealed and only enough of them to pull the lap together, or use removable clamping fasteners if needed and fill holes after. My friend Ray Speck of Port Townsend WA has built about 90 to 100 lapstrake boats of various sizes (he teaches at the NW School of Wooden Boatbuilding) and he recommended the rabbet method for ply lap, though he does not cloth coat the planks on smaller boats. His conventional timber boats are jewels. Here's a pic of a solid teak Whitehall he did many years ago.
    Or, fit the plank with conventional bevels, then remove and coat with cloth both sides, clean up and re-hang. MM's shape is so gentle there are few extreme bevels and properly glued laps are stronger than riveted.
    Few frames are needed with this build and they are best sawn, and joggled to the planking and glued into place with fillets. Two layers of 3/4" ply (purists screaming in background) will work for this job but compass timber is best of course. In your part of the planet I'm not familiar with most of the woods but I've done repairs to 50 year old vessels made entirely of Kauri and found no rot.
    One great advantage of Ply lap planking is that the planks can be quite wide in comparison to other methods. Do a careful lining off job and don't be in a hurry to start planking. Some builders hang battens representing the laps on one side of the molded shape and fiddle around until it looks really right.
    Some large English sailing Trawlers of the middle 19th century had lap plank below the waterline and carvel above. The idea was the lap gave more strength and better sea-keeping while the carvel took the chafe and abuse of the nets.
     

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  5. gonzo
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    gonzo Senior Member

    Lapstrake, or clinker, is basically the equivalent to having closely spaced stringers. That minimizes the need for frames.
     
  6. Perm Stress
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    Perm Stress Senior Member

    All the traditionally built solid wood clinker boats I did see in flesh or in drawings had closely spaced frames.
    Glued Waarships on the other side so not have much more framing as comparable plastic boats.
     
  7. PeterSibley
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    PeterSibley Junior Member


    Bataan , thanks for taking the time to respond ...much appreciated .
    I'll give some thought to the rabbeted lap although the idea of running it with a motor plane jigged to run on a batten representing the top edge of the new plank does seem easier .

    I'll definitely spend a fair bit of time lining out the plank runs with light stuff ...nothing upsets the eye more than a bad clinker layout !

    I have some sawn material suitable for sawn frames it's heavy though , material I had sawn for the MM I had started earlier ,all sawn 45mm (1 3/4''), but in a glue ply construction I had thought just to laminate frames in place on the inside of the hull (over plastic sheet ),.glue in joggle fillers then take them out ,plane them pretty , drill all holes required (plank fastenings , floors etc ),number them ,then have them CCA impregnated and install .The reason for all this being my sawn bends are tallowwood , good strong heavy (60# cub ft ) durable wood that doesn't glue worth a damn .It has too much greasy oil in it .....copper bolts only .

    Kauri is a NZ timber ,beautiful and rare these days .

    If you remember the scans when you get home I'd be grateful !

    regards ,
    Peter
     
  8. gonzo
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    gonzo Senior Member

    Perm Stress: they do have frames, but they are very light compared to a caravel planked hull of the same size.
     
  9. Perm Stress
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    Perm Stress Senior Member

    What I did see on traditional build boats, difference was not so dramatic to be immediately obvious.
    From engineering standpoint, lots of long thin stringers, supported on lots of long thin frames do not present possibilities to win on strength.
    For wooden hull, however, the limiting factor could be the movement of planks relative to each other, and consequent loss of watertightness. Here clinker offer significant advantage, as planks are reliably fastened to each other, and planks could be sized for strength, with less concern about watertightness issues. Hence the win would be more likely in thinner planks, on basically same frames.
     
  10. gonzo
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    gonzo Senior Member

    I don't know how the build in Lithuania. My experience is in South America, North America and Western Europe. In those places, the framing of lapstrake is markedly lighter.
     
  11. BATAAN
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    BATAAN Senior Member

    Long rambling post about laminated stuff in boats. My 10' Herreshoff lapstrake pram by Ray Speck, new in 1984, had 1/4" planking and 3/8 x 5/8 frames, copper fastened, very trad. It was totally worn out in ten years. I replaced it around 1994 with a lapped ply 11' modified Claude Worth Auray Dinghy in 3/8" birch ply, epoxy saturated, with only one lap that formed the seat stringer, no frames except the flotation tanks, no chines, and cloth only on the outside bottom and lower plank. This tank has had its bow chopped off by a big prop and been fixed, dragged over oyster covered rocks and many rough beaches, been squished in docking, run into rocks, dropped, neglected and generally abused. It's incredibly dry motoring to windward in a good chop. I've never managed to flip it in surf which is more than I can say for inflatables.
    It's still on the original Awlgrip paint job and is looking a bit shabby.
    Absolutely no comparison in value to a timber boat as I would have gone through two or three of them and spent a lot of time painting and fixing in between.
    On my drawing table there's a new one planned, same model but lighter (old one is obviously over-strong) and another inch of freeboard for those especially rough beaches. But since I'm lazy I want to wear this one out first, which may take the rest of my life.
    If you plan a MM with stiff glued monocoque shell like you propose, it would be best to be like Ruell Parker or Covey Island Boat Works (builders of Nigel Irens designs) and go all laminated from keel to deck with a structural glued in interior. This is by far the strongest as well as the easiest to keep clean.
    Closely check out Ruell's glued-lap-ply Pilot 28 because he has worked out all the kinks and details of the method and quite a few have been built. On seeing two in Key West I was very impressed as to the solid, though unconventional, structure.
    I detest laminated gaff masts and have seen many poor ones fail, but a good job of a hollow spruce bird's mouth spar would help the stiffness of MM a lot and would work fine since she has a pole mast with no bolts through in the original rig.
    The idea of riveted frames seems weak as it makes thousands of holes, and remember that those darn rivets stretch after time and have to be 'hardened up' where a dolly is held on the inside and the nail head given two whacks with a finish hammer. This means access, destroying finish etc.
    Make the frames of something glue-able, even pine. The 90' square topsail schooner CALIFORNIAN I was once bosun of has laminated pine frames and never would squeak or work, even once doing 14 knots on CG radar in the Santa Barbara Channel when I was sure the topmast and jibboom would go over the lee side but they didn't.
    A MM with laminated oak frames fastened with non-rusting screws, buried and epoxied over (I dip bronze or ss screws in catalysed epoxy before I drive them in re-fastening jobs and they never break in driving with an air tool or give me any trouble ever again) and the frame really saturated with resin and sealed, then kept dry under a good deck, will last a very long time.
    For many years I repaired frames (not sistered) with oak laminations, though they were mechanically fastened as these were regular carvel boats. The technique was to paint the plank then staple down the first lam with monel staples and an air stapler, then build up the lams in place with WEST system and laminating filler, covering and saturating the whole thing. The frame is scraped when the glue is not quite hard and then trued up with the 4" grinder the next day. These are fastened as any frame but the fasteners are always dipped in epoxy and all holes carefully looked after. When a frame is bad at the bottom where it meets the floor timber you can scarf a piece on that gets wider at the frame/floor joint, making a stronger join and easier to put the frame/floor bolts in without removing planking.
    If you want to build a timber frame boat with a glued shell, it seems to me to be like getting half wet and calling it swimming. I'd go for all glued wood construction, with glued ply lap plank.
    MM is one of the best small fast traditional cruiser models, being truly based on the fish boat roots, but less displacement and lots of outside ballast on a moderate draft. I want one and would choose this model (did ten years ago) to replace BERTIE, as my needs have changed. I even drew a Chinese mainsail that fit the same mast. Where is that sketch?
    Oh, here's a part of that MM article in my photos. Will try to scan the rest next week.
     

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  12. Perm Stress
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    Perm Stress Senior Member

    Folkboats were mostly the same all over the world. The ones I did see were built in Sweden :p.

    To compare like with like, there has to be frames on same boat, with same spacing, the only difference being clinker or carvel build.
     
  13. PeterSibley
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    PeterSibley Junior Member

    Bataan , thanks for the ramble mate ...good stuff .

    Re the keel ,stem ,stern timbers .The problem for me is that I already own a lovely 24 foot 9'' x 6'' hardwood timber , dry ,straight and beautiful plus the same material for stem and stern ..I'd need a damn good reason to toss it ! It should be as stable as any glued section ,maybe more so ....can you explain this to me ? Every book says laminate the timbers but I can't work out why . All I end up with is lots of smaller bits glued together with the possibility of delamination .The big bit will be that shape for a very long time !
     
  14. gonzo
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    gonzo Senior Member

    Glued laminated frames are all the rage nowadays.
     

  15. BATAAN
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    BATAAN Senior Member

    The modern approach is don't let the wood get wet and it won't move and break the glue joints. I can't explain it all due to lack of personal experience, but I guess a glued shell on a conventional timber frame would work if you don't sheathe the keel, because the large timber swelling will break the sheathing fabric. Keel lams are all individually sealed and coated in laminating and then covered with the hull sheathing so they don't get wet and swell and move.
    The only problem that seems apparent is the slight movement of the keel timber and the garboard/stem rabbet where this is concentrated. You can't caulk the edge of plywood like you can timber with cotton or oakum so I guess a good fat seam (not tight) and some 5200 might do the job. Possibly you could have a tight seam glued with epoxy but I wouldn't do it that way. BUT 5200 doesn't stick to some oily woods as I have found out the hard way. Of course riveted frames will work and have for thousands of years, just that I think you may be building in future problems and should research thoroughly. Ply doesn't like its surface layers battered and this occurs in riveting when you drive the nail and hold the dolly. Screws might be better. The only way to make the ply planking last is to keep the water out of it and holes don't help. Screw holes are sealed on both ends, rivets aren't.
     
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