Design Suggestions

Discussion in 'Boat Design' started by messman, Nov 21, 2008.

  1. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    As I mentioned, the dory, as we now know it, really is a new type unto itself, vastly different from the "antique" craft of which so much has been written. I have to admit to a bit of historical interest so I'm happy to pass along some of the evolution, which most (exceptions noted) aren't aware.

    The dory has a very interesting evolution. It's an area specific type, so much so that as the model moved from one area of the country to another, it had to be modified to suit the new conditions. It developed quite differently in different parts of the USA as a result, each being better dressed for it's local environment.

    I built a 27' St. Pierre about 30 years ago. I sailed it for a few seasons and then converted it to power fishing operation. I sold the boat only a few years after building, because it sailed poorly and as a fishing boat, lacked a lot of things. It was a reasonably accurate representation of the modified dory seen today, with a wider bottom then the antiques, but not as wide as currently is fashionable, wider stern and less flare. If I was to do one again, it would retain the narrow bottom of the originals, a little less rocker, a little more beam carried aft and considerably less flare. This would make a much less volumes hull, but one that would drive easier when pressed.

    If I were in Chris's place, I'd be looking at a flat bottomed skiff as the most economical way to get on the water, with his desires, but possibly not the best suited for his wishes. The V bottom of moderate deadrise would be a better choice, but at slightly more building difficulty.

    For a cabin boat, you need hull depth, which is difficult if the boat is to work Florida's waters. Getting hull depth in a flat bottom is difficult and much easier with a V bottom. The benefits of course are the cabin doesn't look like a Winnebago isn't parked on the foredeck and you can keep the CG in a reasonable location.

    Cats are an option as are other hull types like the Sea Sled.
     
  2. messman
    Joined: Nov 2008
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    Location: Florida

    messman Junior Member

    I am loving this discussion all, just thought I would let you know that. Ok back to subject.
    Ok, so what I am hearing here is that a dory, even the one I am looking at probably would not be the best choice. For the following reasons:

    1. hull design is not the best for all intended purposes, ie hard to get in and out of for swimming or diving.

    2. It basically handles like a rat (dead) in a trap

    3. probably would not do well with a cabin (even the more modern types)

    Now the question is what should I go with. The Cat, Sea sled, and a V bottom design have been suggested so far. Here is what I want to use the boat for (In order of preference).

    1. Family outings
    2. Fishing
    3. Swimming/diving platform

    These activities shall be done with over night outings, none currently planned for longer than 3 nights. Time does not allow for longer ventures.

    My woodworking abilities should be able to handle most of the challanges that will come along with what ever design I finally go with. But I would really like one that will be fairly easy to build, I want to enjoy building it, but I would rather be able to enjoy using it, if you know what I mean.

    So what would you suggest and if you feel inclined to explain, why do you suggest it?

    Thanks everyone. I am really enjoying this and I am actually learning alot.

    Chris
     
  3. Boatpride
    Joined: Oct 2008
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    Location: UK

    Boatpride Boatpride

    Hi Chris

    your welcome! Yes he does seem to have a business incentive, but his niche is a strong one.

    Best of luck and let us know!
     
  4. tom28571
    Joined: Dec 2001
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    Location: Oriental, NC

    tom28571 Senior Member

    Chris,

    It you assume that the guys who buy, build and use boats for these purposes have some insights to the better boat for the job, then the order would be like this. Monohull V, cat, and sled, with the sled being almost non existent. Some will say that the sled or inverted V (IVB) is the best boat though. So, it boils down to you making the decision anyway.


    If a cat is to have much room inside, the connecting bridge must be high enough off the water that chop does not strike it. I recently took a 45 mile trip in inside coastal water in a 36 foot power cat that was miserable because the designers/builders had sacrificed underway comfort for dock comfort. Chop would hit the underside and make the whole boat shudder. The return trip was fine in calm water. If the underside is high enough that chop does not hit it, a small trailerable cat gets pretty top heavy and prone to capsize even though the initial stability is very high. The designer has to cut a fine line between these competing objectives.

    The sled is probably similar to the cat but I don't have any experience with them. Very few people do have experience with sleds and many of them may have vested interests, so caution is advised.

    Within the monohull platform, there are many different types, flat bottom, deep V, shallow V, lobsterboat, the dory, etc. In general, I think the monohull has more to offer for a broad spectrum of uses than the others but that is my opinion, for what its worth. A self draining cockpit is high on my list and for diving, a gate in the transom to a platform would be great.
     
  5. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    I have experience with sleds and they are easily the best rough water, shoal draft boat going. One ride in a nasty chop and you quickly see it's advantages. Unlike a cat, it gathers it's bow wave up and stuffs it under the boat. The resulting lift and air do several things one of which is swallow up chop like it's not even there. The other nice thing is it's efficiency, which is quite high, especially compared to deep V monos or well burdened cats. This is because the interface between boat and water doesn't cast a high percentage of water aside, but employs it to cushion the ride and generate dramatically more lift. This means more speed from the same HP on other, similarly sized and equipped hull forms.

    My first experiences with a sled was on a real Hickman racer. It was an eye opening experience. Next was a modified sled, which had wider chine flats and built lighter. It literally hops up on plane with no transition, just a smooth rush.

    Honestly there are many designs, in all the hull form categories, that could suit these needs.

    Chris, the design selection process can be a difficult one. There are so many things to balance and counter balance during your considerations. Building ease, in both the design type and construction method, material choices, hull type and accommodation requirements, a target performance envelope, the list is pretty involved.

    As Tom has pointed out, the decision is ultimately yours. You are the best skilled person to access the merits of specific designs. Try to find designs that incorporate as many of the features and desired qualities as you can. From this assembly, you can make a "pro and con" list to see how each stack up.
     
  6. tom28571
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    tom28571 Senior Member

    Paul,

    One thing negative about sleds that I have heard, from Bolger, I think. He said that that in rough water the sled can slam down and puff a wall of spray back out the bow and over the cockpit, creating a new form of misery. Have you had this experience? If so, how bad was it.

    We had one forumite who extolled the virtues of the IVB. Trouble was, his message was so messianic that he was mostly ignored. It's an interesting concept though.
     
  7. messman
    Joined: Nov 2008
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    messman Junior Member

    PAR and Tom,

    And everyone else who has participated in my education here, again I thank you. I do understand that I have to make the final choice. I asked the question because my knowledge is limited and I want to make the most informed decision I can. I have been reading what I can, when I can to help get over the learning curve. The information that is being given to me by you all is being very helpful, even though I have more questions now than ever before. But these are questions that I know I need to answer prior to saying yes this is the boat I am going to build. And many of the questions I know I have are questions that never even crossed my mind, thank you so much for that.

    I very much welcome everyones opinions and experiences, as these only allow me to see things I need to think of prior to committing to a design. As I see it I want to choose a design that is stable overall in most all conditions. Speed is not an issue for me, I am not going to firewall my boat unless there is some sort of emergecy that requires it. But I do want a vessel that is going to sip fuel at it's cruizing speed. (everyone is probably saying he wants it all and he can't have it all) :D What can I say call me crazy :p I know that something has to give somewhere.

    There was a boat featured in a 1973 issue of Mechanix Illustrated I called the Budget House Boat (attached file). I liked the concept of the boat but have shided away from it because it would appear to be for only calm waters such as lakes. Do you believe I am correct in this assessment?

    Again Thanks all
    Chris
     

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  8. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Yes, Tom the old Hickman style designs were prone to this. They also had other bad habits, but you must remember the originals were racers designed many decade ago. Some of the other issues are the anti trip chines on the Hickman style, tended to still permit the boat to trip in high speed turns, they attempted to use a "sneeze guard" to stop the blow back in rough going. These worked to a degree, but there are better ways around it.

    Bill Jackson and a few others starting in the 50's when the military's interest was re-kindled, started to refine the design, but it still fell short on some points.

    Newer designs, like mine and others, have addressed all the issues. The sneeze issue was a function of the quick bow turn and entry angle in profile. With more rake this problem disappears. A re-shaped chine and centerline, removal of the reverse deadrise at the transom, introduction of topside flare plus considerably wider and steeper chine flats solved the other issues. With a jack plate you can run in just inches of water with these things. They are gaining popularity all along the gulf coasts.

    The PM Budget House Boat is really a house boat, though capable of motoring around protected waterways (lakes and rivers). For your needs it's very unsuited, as it would beat you to death waiting on a diver in moderately deep water. Picture a large concrete mixing tub with a small shack on top of it and this is pretty much what this boat is all about.

    http://www.bateau.com/studyplans/HB20_study.htm?prod=HB20 this is a much better version of this style of boat. Again, you wouldn't want to venture into deep water with this.

    http://www.bateau.com/studyplans/P19_study.htm?prod=P19 this is a better choice for your needs.
     
  9. Loveofsea
    Joined: Jan 2007
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    Location: Southern California

    Loveofsea New Member

    I designed and built a 19ft flatbottom dory back in '91, since then i have logged over 60,000nm of open seas here in Southern California. Forgive me for making such a brazen ststement, but i have never seen a commercially available design that gets it right. If designed correctly, the dory is an extraordinarilly safe and sea worthy hull configuration. I couldn't run the seas they way i do in any other hull type. I am pressed for time at this moment, but i would be happy to share some of my design innovations with you.

    Brad

    (loves the sea)
     
  10. tom28571
    Joined: Dec 2001
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    Location: Oriental, NC

    tom28571 Senior Member

    Paul,

    Liz and I are off to the beach for family turkey day but I would like to look at your innovations to the sled when I get back. Some of them I have heard of. I thought Hunt's cathedral hull (Boston Whaler) grew out of the sled and avoiding Hickman's temper and patents.

    I've corresponded with Brad and seen photos of his boat. He goes after the rough riding habits of flat bottoms in a similar way to that which I use on some V hulls and successfully runs them in the ocean. I'll let him write on just how he does it.

    Happy Thanksgiving everybody,

    Gotta run.
     
  11. CET
    Joined: Sep 2005
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    Location: Utah

    CET Senior Member

    Brad, I too would be very interested in your design modifications and innovations for the flat-bottom dory. I am actually in the process of playing with some dory designs right now for use as an inshore fishing platform for So. Cal. waters. Would love to hear what you have to share and see some photos, if possible.

    Happy Holidays!
     
  12. messman
    Joined: Nov 2008
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    messman Junior Member

    I would love to hear and see what you have done as well.

    Chris
     
  13. messman
    Joined: Nov 2008
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    messman Junior Member

    Brad,

    I would love to hear and see what you have done.

    Chris
     
  14. Loveofsea
    Joined: Jan 2007
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    Location: Southern California

    Loveofsea New Member

    Here are a few things that make this hull work so well. The hull is flat all the way to the bow. The widest part of the hull is 2/3 forward, and 8" wider than the transom. i carry 54 gallons of fuel in the fwd 1/3 of the hull (in portable tanks that nest under the deck) I use a SST lifting strake across the transom with a cutout for the engine to create exagerated transom lift..

    __in other words, most of the weigh is pushed max forward. The impact point of the hull is 2/3 fwd where the hull is the widest..

    two opposing factors come into play here--the inherent bow lift from pushing a wider fwd hull over the water and the exagerated trasom lift from the SST lifting strake across the transom. The hull creates lift both fore and aft---that has the effecy of keeping the hull stuck to the surface. if it doesn't lift, it will not slap back down. The impact point (the widest point) uses the extra weight of the fuel along with the exagerated transom lift to crush the water and send it out the sides.

    Here is a link to a stroy that was done about the 'Good Skiff' last year...

    http://www.oceanskiffjournal.com/
     

  15. TeddyDiver
    Joined: Dec 2007
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    Location: Finland/Norway

    TeddyDiver Gollywobbler

    I know quite well what you are talking about. I started a project with quite similar preferences.

    Some exceptions:
    1. Longer cruises. Up to some weeks
    2. Not only for family but also for ugly gents talking dirty:D

    I was unable to find any designs for diving and fishing meeting my demands so here's some sketches what I'm currently building (there's some pictures of the hull under construction etc) but you get a general idea what I'm doing, and maybe it will give you some thoughts and help you to find design for you
    http://www.boatdesign.net/gallery/showphoto.php/photo/9948/ppuser/23741
    BR Teddy
     
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