stitch and glue + -

Discussion in 'Boat Design' started by William C. Wins, Dec 29, 2011.

  1. PAR
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    PAR Yacht Designer/Builder

    Working with goo and sheathing can be daunting initially, but it's not difficult, especially if you arm yourself well with the "user's guides" from the major formulators and read up on the various processes involved. Following basic procedures and rules, can insure your first "goo and go" job will be a success. This said, most have an easier time understanding hard fastener assemblies. A combination of epoxy as a glue and hard fasteners can also make an extra secure assembly.
     
  2. michael pierzga
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    michael pierzga Senior Member



    Actually the stitch and glue routine is so logical that its foolproof. Your eye will instantly sense epoxy coverage, cloth saturation and joint intergrity. Most mistakes are made in the mixing of the two chemicals, not application or engineering

    The beauty of stitch and glue is that there are no fasteners. If you look at an older plywood boat , deterioration will always be in the area perforated by fasteneres. On an epoxy stitch and glue boat water must no be allowed to enter the wood. Avoid fasteniners at all cost.
     
  3. rwatson
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    rwatson Senior Member

    On a totally different angle, a local boatbuilder down here was contracted to build the Tug from Sam Devlin's designs, and ran into all sorts of problems with the actual plans.

    I can put you in touch with him if you want to chat about the problems.
     
  4. FAST FRED
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    FAST FRED Senior Member

    A good aluminum welder is cheap if a slab sided boat is your desire , and longer life than coated plywood is desired .

    FF
     
  5. upchurchmr
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    upchurchmr Senior Member

    William,

    Milehog had a great suggestion - build a relatively simple boat with the same construction technique. Especially if you choose S&G. I have a friend who wants to build a kayak. He took the first 4 molds of mine and set up a plug for the "nose" just to try everything required for strip planking.

    Thats not a pitch for strip planking, just for making something to learn on. It could be useful if you find a "tender" for your tug. Possibly a 10-12 ft row boat.

    Lots cheaper to learn on something thats not the final product (worth lots of money and time).

    Marc
     
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  6. DGreenwood
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    DGreenwood Senior Member

    PARs take on the tape seam construction is similar to mine. It is easier to cutout a quick mold station, add some tape and clamps, put in the occasional screw, or a have a friend put his foot on it, than all those stitching holes etc.

    Build a baby cradle or a small dinghy as a trial run. Then you have something when you get done.
    (side story ) I was hired by an acquaintance to build him a cradle for fixed price. When finished he tried to grind me on the price. I threw a shop party and invited him. When he arrived the cradle was full of ice and beer. He got the picture. It has served as a cooler ever since!:p
     
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  7. Wayne Grabow
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    Wayne Grabow Senior Member

    I used 14 frames on my last boat but no permanent fasteners. No reason the two techniques can't be combined. The frames help create and align the shape, provide a structural skeleton, help support interior features, and a foundation for clamping or temporary staples/screws.
     
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  8. philSweet
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    philSweet Senior Member

    yep, you can build the boat with no screws. Then you go bolt on a hundred odd deck fittings and doodads. What's the point? I went through two bags of bungs when I reworked my 20 year old skiff. And that was just bunging abandonned hardware holes that had accumulated over the years. There were at least as many more still filled with screws. 16' boat. Use materials that will hold a screw and not rot past a 3/8 bung in twenty years. If you are mounting stuff onto thin ply, I like to add a hardwood cap and screw into that (cap first, backing plate if you still need one). Can be pretty thin, 3/16" is ok. You can take the print from a particular piece of hardware out of the boss if you need to replace, say, the stern light with a different one.
     
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  9. michael pierzga
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    michael pierzga Senior Member

    Of course. No need for permanant fasteners .

    One defect of a ply timber boat is that the bilge is " dirty" ....structure like chine logs and keels hold dirt and water. Important to have a good floor board design on a ply timber boat so that you can lift them and clean out the bilge. Stitch and glue composite construction leaves a smooth clean bilge.

    Ply on timbers works. I had one for many years....and the construction is much less messy because you dont have so much fairing work to burry the tape joints. A nice ply on frame boat is the simmons skiff.
     
  10. PAR
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    PAR Yacht Designer/Builder

    Taped seam builds can also have stringers to "dirty" up the bilge. This isn't a problem or a flaw, nor indicative of the method.
     
  11. FAST FRED
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    FAST FRED Senior Member

    I still have a problem with super light construction on a "cruising" boat.

    Problem dock access,

    Sometimes you tie on to a tug boat , sometimes the tug ties on to you!
     
  12. PAR
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    PAR Yacht Designer/Builder

    Fast Fred has a point. One of the difficult things to do when designing a relatively light craft, is to get puncture resistance in the hull shell and comfort afloat. Light boats tend to have high acceleration rates, which tend to be uncomfortable, if tolerated for very long. Also light weight hulls generally don't have enough meat between them and the partly submerged log they've just encountered. On planing craft, it's often nearly imposable to get this balance sufficient enough, though displacement craft usually can be engineered to a reasonable standard.
     
  13. philSweet
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    philSweet Senior Member

    With stitch and glue, you engineer the plywood to accommodate the initial assembly process. Thickness, species, and grain orientation is fiddled with to suite panel curvature and the angle of the chine. Then you add a laminate schedule to make up any shortfall. Hopefully, the result is a reasonable and cost effective solution. If not, go back and start again. Getting a ply panel to bend anywhere close to it's minimum radius with S&G requires a hard chine (say 70o angle or more)*. Softer chines need relaxed bends and are generally tougher to align the panels. Most boats feature flatter panels and softer chines at the ends and this works for S&G. A tug, on the otherhand, usually has 'shoulders'-tighter bends at the ends and will probably need harder chines carried farther towards the ends.

    * Maybe a better way to say this is that it is harder to work in a change of panel bend radius with a softer chine. S&G advocates always stress the lack of stress concentrations inherent in the method. Potential weight savings are the payout here, but it can make getting the shape you want a PITA. There's no free lunch; the stress concentration is transferred from the build to the builder.:p
     
  14. rwatson
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    rwatson Senior Member

    If the builder finds the stress too much, they can transfer some of it to their wallet :)

    eg. Pay someone else to build it , buy foam or other expensive alternatives,
     

  15. upchurchmr
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    upchurchmr Senior Member

    One of the formites was doing a ply panelled boat but making a soft chine. I think he was using a 3 board strip plank style in the chine only. Still waiting to see the results, but cleaver use of all the "basic" techniques might make boats that everyone would like.

    Not saying that I personally know how to design one.

    My personal hybrid thought is to make a round bottomed strip planked hull below the waterline, then use ply for vertical or flared sides to a ply deck. If I got really gung ho I would soften the deck joint in the same manner. This would not really allow sticth and glue at the deck line. This would be for a trimaran or cat. Probably someone has done this already and I could just copy.

    Marc
     
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