Question Re: Building Method

Discussion in 'Powerboats' started by tpelle, Dec 22, 2009.

  1. tpelle
    Joined: Nov 2007
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    tpelle Junior Member

    I am considering a small express cruiser in the 18 ft range. This boat would see exclusive use on inland rivers - the Ohio and its tributaries - and midwestern lakes such as Kentucky Lake, etc. This would be a "retirement" boat, and would principally be used to haul an old retired guy and his mountain bike on cruises, visiting some of the old river towns, sightseeing, etc. Economy of operation would be a definite consideration.

    I've given this a lot of thought, and I think that a boat with simple sleeping quarters in the cuddy, along with a kind of bimini top with side curtains to form a cockpit shelter would fill the bill. Sleeping and lounging would take place in the cuddy, with cooking done in the cockpit. A porta-potty stored under one of the cockpit seats, enclosed in the shelter, would complete the accomodation.

    My "heartthrob" design is the old Rabl Puffin. I have Sam Rabl's book, and the plans are published in there, but I don't think I could build from the information there.

    I have run across a few modern candidates, such as the Bateau.com Classic 17. I picture this boat with the cabin sides extended and curved downwards to form a cockpit coaming and the addition of a windshield.

    The Rabl Puffin is spec'd with 15 to 20 hp outboard power. The Classic 17 looks to require more. I recognize the necessity to keep the loads light, and not burden the boat down with heavy gear and complicated structures. Operation at slightly-above minimum speed to stay on plane would be the norm.

    My question concerns the weight resulting from varying construction methods, as well as the ease of the construction itself. My intuition suggests that "plywood on frame" such as used for the Puffin will result in a lighter hull, as the structural frames are few and the plywood skin seems to use thinner sheets. Also it seems that it would be easier to build a straighter hull by setting up and securely bracing a frame before applying the skin. Epoxy sensitivity as is so often mentioned in stitch and glue construction is also a concern.

    Has anyone updated the Rabl Puffin design and published large-scale plans?

    Are there any other similar designs that I should consider?
     
  2. rasorinc
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    rasorinc Senior Member

    Go to the Glen-L site look at Wanderlust, Sea Knight, Bravado, Cuddy Sport Carioca, nomad, Vera Cruise, plus others. Many others. Build out of wood. Wood lasts Generations
    picture did not come yhru. look under outboard boat plans






    Characteristics
    Length overall 19'-0"
    Beam 7'-10"
    Hull draft 9" (with skeg)
    Hull depth 3'-7"
    Hull weight (approx.) 950 lbs.
    Height overall 6'-3"
    Cabin headroom 4'-6"
    Cockpit size 6'-2" x 8'
    Sleeping accommodations 2
    Hull type: Vee bottom, hard chine, developed for sheet plywood planking.
    Power: Single or twin short shaft outboard motors to 150 hp total. Long shaft motor can be used if transom modified. Optional power, single stern mounted inboard motor to 700 lbs connected to an outdrive.
    Can the hull be extended or shortened? Extended: No. Can be shortened up to 10% by re-spacing the frames from the aft end of the stem to the transom a proportional amount. We do not recommend increasing the beam.
    Trailer: Designed for use with Glen-L Series 3800 boat trailer plans.

    Photographs Bill of Materials Notes Return
     
  3. tom28571
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    tom28571 Senior Member

  4. tpelle
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    tpelle Junior Member

    So I see that the Glen-L Sea Knight is comparable in size and layout to the Puffin. But I see that the one in the video on Glen-L's site is equipped with a 100 hp motor.

    Note the the Puffin is supposed to perform with 15 to 30 hp.

    This begs the question: What is the minimum horsepower outboard that the Sea Knight will perform adequately with?

    Keep in mind that I would not be towing skiers, nor would I really WANT really high speeds - I'm thinking about 15 - 20 mph would be plenty fast enough.
     
  5. apex1

    apex1 Guest

    Why are´nt you polite and provide some links or (better) pictures?

    Why do nearly all questioners expect that the member willing to assist, is as willing to do the related recherche about the basics of their choosen design first?
     
  6. tpelle
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    tpelle Junior Member

    The only "on line" reference I've ever seen to the Puffin was on this site, but I can't find it now. Even googled it, and nothing comes up.

    This design appeared in Mr. Rabl's book "Boat Building In Your Own Back Yard" - my issue is the 2nd edition and was printed in 1989. It's an 18' express cruiser for outboard power, reverse sheer, plywood over oak frames.

    The Bateau Classic 17 is here:

    http://www.bateau.com/proddetail.php?prod=C17

    My question was not so much design-specific, but general in terms of comparing the two construction methods, and in their relative minimum practical power.
     
  7. tom28571
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    tom28571 Senior Member

    OK, the question is about construction. It is almost always possible to build a suitable design lighter in S&G than plywood over frames and logs. Mainly because no frames or logs are required. There are special cases both ways.

    On the question of power, the lighter boat will always require less of it.

    Epoxy sensitivity is a serious issue for those that are sensitive to it. It is fairly rare. I have known hundreds who build with epoxy and only a very few have become sensitized. On the other hand, a nearby builder who has built several of my designs has had to stop using large quantities of epoxy because he became sensitized on the last one, a 28 footer. Bad news for both him and me.
     
  8. liki
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    liki Senior Member

  9. PAR
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    PAR Yacht Designer/Builder

    There's one for Tom's heart, Iiki.

    Construction methods boil down to familiarity mostly. Most novice builders are more comfortable with plank on frame methods, because they can cut out the parts, assembly them and these things are comfortable and easy to understand. It's often difficult for a novice to get their head around plastic coatings, encapsulation techniques, "liquid joinery" methods and other high "goo factor" construction ways.

    Ultimately, what I tell folks to do, is to forget about the building technique and focus on the results that you may find desirable.

    For example, a taped seam or other wood/composite build (like Graham's Outer Banks 20), will have a relatively frame free interior, with the bulkheads and furniture providing most of the hull reinforcement. This makes things easy to clean, is less likely to collect dirt and debris and makes for an uncluttered interior. On the other hand, you just can't drive a big 'ol nail in a frame to hang up you coat either, you'll probably have to plan out and glue up a block that can accept screws for a coat hook. Also, working with goo's (epoxy and stuff) is messy, sometimes difficult and costly for the novice. Once you get used to it, it's an asset, but this takes practice.

    A plank on frame boat almost always results in a heavier product. This isn't such a bad thing in this size range as it can smooth out the ride to a degree. It does mean you'll need more engine and fuel to get the same performance as a lighter boat, but I read "performance" isn't a big item on the list, so long as she is reasonable. Framed boats permit interior changes on a wholesale level fairly easy, because the boat will not fall apart if you pull out the furniture, so long as the frames stay in place. Lots of people (me included) like the look of frames in the cockpit and cabin spaces, plus there's a real sense you're in a boat that can take a beating, maybe bash it's way through if necessary. This sense of heft can be reassuring in a rough patch of water or when the wife elects to bring it up along side a dock "way harder then she estimated" on her first time in the skipper's seat. Couple this with the simplistic nature of most plank on frame builds, it easy to see the romance, especially if you are or suspect you might be epoxy sensitive.

    The percentage of people affected by this is low, but enough are to warrant concern. Some seem predisposed to be sensitive, others force it down their own throats (literally). If you are allergic to particularly alkaline materials, you may have issues with some types of epoxy. Those that are or suspect they might be, will be well served to use "non-blushing" epoxy formulations, which seem much less prone to cause issues. It goes without saying you need to protect yourself from the dust.

    In the end, a new builder needs to consider many things, but the final result is the big picture, so what do you want this to be? One filled with traditional frames and stringers, where adding a shelf is as simple as screwing one to the frame faces or the modern smooth surface look with rounded corners and filler under every inch of paint.

    Modern construction methods do produce boats with much less maintenance requirement, but there's much to be said about the old ways of planks over frames too.
     
  10. rasorinc
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    rasorinc Senior Member

    Go on the Glen-L forum and ask what speeds can be expected for the Sea Knight with 100 hp or with 50 hp. The builders of these boats will give you actual facts re: speed.
     
  11. tom28571
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    tom28571 Senior Member

    I am bound to give some points to the other side of the plank/frame vs S&G construction although I like both in certain cases.

    My first boats over 50 years ago had no frames although S&G had not been developed yet. S&G got its start in Norway in the late 1950's in the form of plywood racing boats built in an open basket type female mold. The joins were made with fiberglass and polyester resin. Not ideal resin but, handled properly, some very successful boats were built in Europe. Once finished, a mold built boat and a S&G boat are indistinguishable from each other because the stitches disappear in the finished product. The resultant construction is called monocoque and takes its lead from aircraft construction where strength/weight ratios are much more critical than in boats. In automobiles, its called unitized bodies and most all cars are now made this way. The construction of almost all fiberglass boats also fit this description as well as cold-molded wooden ones.

    When I'm in a well built S&G boat, I get a warm fuzzy feeling from the fact that the hull in a single bonded unit as opposed to having hundreds of individual pieced fastened together with screws or nails. This is obviously a personal issue and there are plenty of adherents on both sides. Either can satisfy and its an individual choice.

    Being a woodworker, I do appreciate the value of a boat built with wood as it comes from a tree. The basic material is also more pleasant to work with. Being a long time racing sailor, I also appreciate the value of a lightweight, strong and stiff hull. Its your choice. I try to put some of both in every boat I build.
     
  12. gonzo
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    gonzo Senior Member

    I can't see much advantage in many S&G builds. A chine and sheer log can be fitted very fast if the fit is not critical. With epoxy only an approximate fit is necessary
     
  13. PAR
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    PAR Yacht Designer/Builder

    There can be a huge weight difference between plywood over frames and stringers and a well engineered taped seam build (stitch and glue). Secondly, without all the internal structure, the surfaces are easy to clean, plus any moisture that might collect will not be "compartmentalized" with a plugged up weep hole as it can in a traditional build. There are several advantages to S&G, but there are also disadvantages, just like everything.
     

  14. gonzo
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    gonzo Senior Member

    I mean that you can fasten to the logs instead of stitch and glueing. I've built some small boats like that.
     
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