Feedback request on sailing-rowing-cruising design and materials

Discussion in 'Boat Design' started by scotdomergue, Mar 9, 2010.

  1. scotdomergue
    Joined: Jan 2009
    Posts: 114
    Likes: 3, Points: 18, Legacy Rep: 45
    Location: Twisp, WA USA

    scotdomergue Scot


    Thanks for much very helpful additional information! Again, lots for me to think about and consider! It’s certainly easier and less expensive to build with glass!

    I need to review the formulas and figures I used in my spreadsheets, but I think there are just over 20 sq.m. of hull, topsides, partitions/bulkheads, etc. I think that’s area of core material, so it would be twice that if you’re talking fabric/epoxy surfaces. At 2 kg/sq.m. I think 20+sq.m is about 90 lbs, which is well within my weight goal; but 40sq.m would be almost 180 lbs which is significantly more than I‘d like.

    I’ll spend some time reviewing everything, considering appropriate changes, figuring materials, etc. I imagine that the interior partitions (bulkheads) can be lighter construction than the hull. For example the storage spaces under the cockpit floor and on each side are split into fore and aft watertight sections by partitions - what I think you’re suggesting as “partial bulkhead under the rowing deck“. I’ve been planning 9.5mm CoreCell for the hull, but only 6mm for most other panels, and I would think that a lighter fabric would also be fine for the bulkheads/interior partitions. On the other hand, a heavier fabric or multiple layers might be appropriate for the cockpit floor and the side decks.

    A model and test panels make sense, as does design review as long as it doesn’t enormously increase the cost. Lot’s of issues to balance, including just how serious I am about going offshore! I’ve imagined doing initial trials on local lakes, then cruising in the protected waters between Vancouver Island and the mainland (San Juan Islands, Gulf Islands, etc. - areas I‘ve kayaked and sailed my old Venture 17). Only then, if I’m really enjoying it all, do I imagine heading up the inside passage to Alaska, and later farther if still enjoying. If design review would only cost $200, no problem, definitely worthwhile once I’ve done everything I can to get the design as good as possible. If it would cost $2,000, then I’ll need to get serious about going offshore to be ready to spend it.

    These communications give me confidence that I can move forward successfully. Thank you! Scot
  2. messabout
    Joined: Jan 2006
    Posts: 3,105
    Likes: 271, Points: 83, Legacy Rep: 1279
    Location: Lakeland Fl USA

    messabout Senior Member

    Scot; I must read the books you mentioned. Sounds like some tales of high adventure. I am still clinging to the idea that such events are the exception rather than commonplace.

    One of the forum participants (most of us believe him to be foolhardy in the extreme) has a home built sharpie like skiff about 18 ft LOA. He routinely takes the boat 100 miles off the California coast. Single handed, single outboard power, tiller steering. He must be a helluva good seaman or else he is a charter member of the Luckiest People On Earth Club.

    My experience in hurricanes has not been in boats, i'm pleased to say. I live in Florida and over the years we have had collossal storms aplenty. Hurricane Charley, our most recent, was not a particularly powerful one. Still it ripped thousands of oak trees out of the ground, it decimated the small inland town of Arcadia. It completely destroyed many concrete buildings, turning them into dust and rubble. Frame structures and particularly mobile homes simply disappeared. The town was shut down for weeks in the aftermath. You have to see one of these things to believe the incredibly destructive power.

    I believe that you can build a boat that can survive a storm of hurricane intensity. Like the corked bottle, it will come back to the surface even after it has been submerged, and rolled around under water for a while, by a huge breaking wave. Three cheers for Archimedes. The bottle or the boat might well remain intact. That is one thing but the human occupant is quite another. Sailors are not made of CF and besides that, we must breath air not water.

    I like your boat. It shows some shrewd features that reflect your engineering ability. If I am to pick on it, I will question the seemingly long length of the centerboard. Yes. it is probably more efficient than a short fat one but it has some disadvantages. Depth is one of them, strength too. Think of it as a cantilever beam. If you use a section, like NASA 008 then it will not be very thick.

  3. Guest625101138

    Guest625101138 Previous Member

    The area is the 20sq.m not only one side. You would add weight for joining, fairing and painting plus local strengthening around openings and high wear or impact zones. I expect the factor that will control the strength is your weight impacting at a point. With a good foam you should get away with around 600gsm glass on each side - will end up a bit over 2kg/sq.m. This is something you can use the test panels for - weight and impact strength.

    A strength review will be more like $2000 unless you have a good friend who can do it.

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