Request your input on my design

Discussion in 'Boat Design' started by richardf, Jul 15, 2013.

  1. PAR
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    PAR Yacht Designer/Builder

    I was working up to a "Principles" recommendation, though thought at this stage of the game, he absorb some of the lighter reading, as "Principles" can get a bit thick, for the uninitiated.
     
  2. tunnels

    tunnels Previous Member

    When all the facts have been presented and a lot of options explored is best to put all and everything to one side and go with your gut feelings ! what do you want to do ?? :confused:.
     
  3. hambamble
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    hambamble Junior Member

    Yes, the "principals of Naval Architecture" books are quite wordy. This is not part of that series, but an independent book on yacht and boat design. I think its a step up from Gerr's books, but not so much that it requires an expert to read it. It goes through the process of designing a 40 foot yacht from scratch, through the design spiral, weights and moments, scantlings, etc.

    Although its probably not an ideal starting book, its probably one of the few that shows you how to design a boat from start to finish, and for that reason, i think its one of the best books out there.

    As PAR suggested, I must say that Gerrs boat strength is great for the home builder as it covers most materials and has relatively simple scantling rules, so that's worth a look.
     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    Vanity should not be part of the equation. If the thought of being able to proudly announce that you designed it is the chief motivation, start with a project other than a boat, something where failure can't hurt anything more than your pride.
     
  5. nzboy
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    nzboy Senior Member

    boat design books

    I think by the time you have mastered "principles of yacht design "you could be well on the way on a build .Paul Gartside has couple of designs that is in Richards style .Single chine and strip plank .My fathers Pelin empress was ply but the forward sections were still double diagonal because of the flare. So Im a little bias towards strip plank, designing a ply boat is best left to people who can enjoy principles of yacht design for a light afternoon read.
     
  6. HakimKlunker
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    HakimKlunker Andreas der Juengere

    I meanwhile do all my drawing on the computer, too. And I also love all the time saving and increase of accuracy.
    But I find myself often in the workshop and sometimes it is much easier and faster to use the 'old fashioned procedures'. If I need the centre of a circle - I'll find it without mouse.
    The 'lost arts' can help to convince your drawing program to do what it actually tries to refuse.
     
  7. PAR
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    PAR Yacht Designer/Builder

    All of my conceptual work is done by hand, which I find faster. The same is true of styling clues and the first rough GA. Once preliminary figures are roughed in, satisfied with where the project will go, the sketches get "plugged in" and the process started in earnest.
     
  8. richardf
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    richardf Junior Member

    Amazon has Gerrs' book so I am sending for that as a start. Thanks for all of the advice and information. When you are 72, "vanity" is not part of the motivation to design your own boat, nor does safety take a back seat. The typical conversation when someone sees my Senica for the first time is "Wow, did you build that? Sure is neat." Once in awhile someone will ask if I also designed it; not often though. The designing end is strictly for personal satisfaction. The problem here though is I am not trying to design a 14 foot 300 pound boat, but a 24 foot 1500 pound boat. The investment in time and money is monumentaly more for the latter. The Seneca took 6 months, the wife thinks the 24 footer will take the rest of my life. Maybe she knows something I don't.
    Richard
     
  9. richardf
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    richardf Junior Member

    I was looking through the Glen-L catalogue and came across the following boat:

    https://www.glen-l.com/designs/hankinson/kh-images/057vandal-l.gif

    She is a beauty, and would fit the bill for what I want, except it is not purpose built as a displacement speed vessel. It coincidently looks very similar to the design I was proposing, and is also built using plywood panels. I just like the look. Funny that their panels are developable but my lines were not. I guess the entry is a lot less sharp than what I was proposing. In any event, I don't want the expense of power and fuel to run this boat at planing speeds. How do you think she would do with low power and just cruising around at 6-7 knots?

    Thanks,
    Richard
     
  10. DCockey
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    DCockey Senior Member

    My guess is Vandal would consume 10% to 20% more fuel at 5 knots than a boat of similar design, displacement and engine with the hull modified for lower drag at slower speeds.

    Vandal is listed as 4500# displacement which is considerably heavier than what you have been considering.

    I would mock-up the V-berth and try it for size before committing to building Vandal. Also contemplate on whether the head between the berths will be satisfactory for you and your wife.
     
  11. DCockey
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    DCockey Senior Member

  12. PAR
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    PAR Yacht Designer/Builder

    Of the Devlin designs listed, none are especially light and all require some power, though Dunlin would be sort of close at 2 tons and needing 60 HP for 15 MPH. This is a far cry from displacement cruising, in a light modestly power craft, which typically could live with as little as 10 HP.

    Vandel is a modified warped bottom with a good bit of deadrise and as you'd expect a good bit of displacement, requiring a lot of power. She'd eat 4 or 5 gallons per hour easily, which compared to a real displacement craft would be considerably more then 10% or 20% more. More realistically she'd be 2 or 3 times more in fuel consumption. Unless you mean 10% - 20% more then a typical 23' powerboat David, in which case I'd agree, she's a bit heavy, though not overly so for a cruiser.

    My 26' displacement cruiser is 1/3 less in displacement as the Vandel and at cruising speed literally sips fuel in comparison.

    Aesthetically, all of the above designs could be incorporated into a real displacement hull form. It seems he's more interested in a tug or troller type of boat, then the houseboat he initially requested.

    [​IMG]

    This is a wholly different design, not displacement (I don't have a tug design), but full plane with reasonable semi plane ability. Nothing remotely close in terms of efficiency, again compared to a real displacement craft, but closer to what Richard has listed as other possible design candidates. It too is a warped bottom and needs power to shove along and is fairy heavy, but the goal on this design was a cold weather full plane cruiser, with standing headroom through out.

    To answer your question Richard, semi plane mode is an odd place for a boat to find itself and difficult to design for. You can take the approach of a modest warped bottom and just under power her. You'll need tabs or a hook to keep her bow down and top speed will be limited by these "tricks" but she'd do okay. Getting over the "hump" as we call it is costly, in terms of power and fuel consumption. It's just physics and designing a hull to travel in the no-mans land of semi displacement speeds, can be difficult. Other then driving a full plane craft at slow speeds or under powered, the only other way is to make a displacement craft so efficient, it can push through it's theoretical hull speed limit a little. Since the two hull forms are so different, there's no real good "in between". Atkins has had some success with well crafted hooks and box keel designs, that do fairly well in semi plane mode. Of course, being a half a century old or more, these designs will be heavy and traditionally constructed, but modifications could be made. Maybe look up some of Atkins Sea Bight or his box keel designs.
     
  13. richardf
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    richardf Junior Member

    Paul,
    You sure design beautiful boats!
    The boat I want has to be simple to build, cheap to operate, handle ICW waters in Florida, and have standup headroom, with overnight comfort for two, and entertainment for four, and trailerable.
    It seems to me that could be met with about 3000-3500 displacement in a 24 foot boat, if properly designed. But, I obviously no little about boat design. It has been interesting to talk to you guys and listen to what you have had to say. It really has opened my eyes. What I want is a far cry from a flat bottom skiff! But, maybe a flat bottom and box keel is a possible path, as you mentioned. I don't understand the concept though.
    Richard
     
  14. DCockey
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    DCockey Senior Member

    Back in post #1 Richard gave his requirement as "displacement speed". He was also talking about an overall length around 24 feet. So I assume his speed requirement is around 5 to 6 knots, not "semi-planning speed".

    Here's a link to a previous discussion on powering Devlin's Surf Scoter for displacement speeds only. http://www.boatdesign.net/forums/bo...t-hull-hp-displacement-hull-speeds-40536.html It includes a report on Sam Devlin's suggestion about the power to use.
     

  15. tunnels

    tunnels Previous Member

    To add a boarding platform and a bracketed outboard would be the answer !
    a Honda outboard is really quiet and smooth running something in the region of 30 to 40 hp maybe ! would have battery charging capabilities for any lighting tec . should move the boat with easy and be very economical to run at slow speed :)
     
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