New 14'-16' Daysailer/Weekender Design: Raison d'etre

Discussion in 'Sailboats' started by Doug Lord, Nov 11, 2011.

  1. CloudDiver
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    CloudDiver Senior Member

    I am resurrecting this thread to see if anyone can be more specific about the pros/cons of Cracker's conceptual drawing above.
    I like the scow bow concept because carrying the full beam width for nearly the full LWL creates so much more interior volume (which is why Doug started this thread, no?)
    I agree with many people who have said the scow bow, performance advantages aside, isn't so pretty. I had the idea some time ago to try some kind of twin bow design, but Cracker's conceptual drawing above really nails it, just IMO (and his drawing ability far exceeds mine, lol).

    I'm interested in the scow bow concept (just like Doug) to build a smaller boat that maximizes interior space. In my case I'm looking at an LOA of 25 feet due to restrictions of a local mooring I want to use. I feel like I can build a boat that is just a shade bigger than my Catalina 22 but with far superior performance and a modest increase in interior accommodation.

    So does the twin bow concept proposed in Cracker's conceptual drawing worth a shot? does it really offer similar performance to a rounded bilge scow bow? A down-wind flyer but not so good up wind?
     
  2. CloudDiver
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    CloudDiver Senior Member

    This is the drawing I was talking about... I think this looks fantastic. Cracker, I hope you are still around the forums!

     
  3. CloudDiver
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    CloudDiver Senior Member

    If anyone has any info on this old tunnel hull Sharpie design please speak up, my Google searches have turned up squat, except for this thread, lol!
     
  4. CT249
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    CT249 Senior Member

    Tunnel hulls were seen in the Moth class initially, although the tunnel's dimensions were restricted to prevent them from turning into cats. The later scow Moths had fairly flat tunnel sections at the bow. The drawing previously shown could have been a Hurricane, a scow designed by Peter Milne who also drew the Fireball. I don't know if any were built or how well they went.

    Scow Moths are great fun, but they crash around in a chop and improved techniques and materials meant that the conventional sharp-bow boats dominated the class from the late '80s onwards.
     
  5. CloudDiver
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    CloudDiver Senior Member

    What do you think of the conceptual drawing by Cracker on the previous page of the twin bow concept? Seems like some don't believe it provides the same benefit as a rounded hull scow bow.

     
  6. CT249
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    CT249 Senior Member

    I don't really know. I never found any details about the Hurricane's performance. When heeled, the twin bow boats like the one Cracker posted could have quite high wetted surface from what I can see; that deep Vee shape (which is what the Cracker design would become when heeled) has little volume or planing area in comparison to its wetted surface area.

    Experience in the scow Moths indicates that a scow can suffer major nosediving issues. If the bow on a conventional boat drops under the water there's no big problem because the surface area is small. If the bow of a scow drops under water you can catapult. Obviously this is also affected by the angles you sail downwind and the freeboard. In the last of the scow Moths the nosediving issue was improved by making the stern narrower, but that means that you lose some of the advantage of the bouyancy moving to leeward.

    I sail windsurfers (which are almost all essentially scow shapes) and the first boat I ever owned was a scow Moth. They can be wonderful craft, but the problems they suffer in chop are serious. It may be OK in something as small as a Moth or a board, but Moths (like Mini 6.50s) have very big rigs for their length and boards are very slender for their length. In a boat with more conventional dimensions, you can't normally afford to slam such a wide surface into chop. The concept of heeling the boat to reduce wetted surface is good in flat water, but in a significant slop it doesn't really work because too much of the boat is slapped around by waves.

    The scow concept is well over 100 years old and was used even in the most "establishment" of boats - Iselin wanted Herreshoff to make Reliance into even more of a giant scow than she was, but Herreshoff refused. He then created the Universal Rule to ban the scow-type bows because they were so uncomfortable and created such severe structural problems. Other "round bow scows" suffered similar issues just about everywhere, which is why the scow shape basically retreated to inland waters.

    The concept may work in the Mini class because of its vast and expensive rig and foils and quite sophisticated construction. That's great, but it doesn't mean that the concept would work particularly well elsewhere.
     
  7. Cacker
    Joined: Sep 2013
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    Cacker Junior Member

    Le Petit Baigneur 1968

    Le Petit Baigneur 1968...
     

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  8. pogo
    Joined: Mar 2010
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    pogo ingenious dilletante

    para double hulled and massively pounding in waves ----- offically i name this type of craft

    " Bangaram"


    pogo
     
  9. CloudDiver
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    CloudDiver Senior Member

    I get what you are saying... I think, LOL! I'm trying to go along with the question posted by the OP (in relation to the scow bow Teamwork 747 min 6.50 by David Raison) which is to have a design that satisfies "the crux of this challenge is to use the room the concept offers yet have the boat perform exceptionally well!"

    I'm thinking of 7.6m version of the mini 6.5's that maximizes interior space, but delivers a higher level of performance than the average cruiser of that class/size. I'm planning to try a unique build method with foam core/S2 Glass/epoxy, but this method only really makes sense with hard chine designs. So Cracker's conceptual drawing makes sense for it hard chine, but also because some people don't like the 'look' of the rounded scow bow... I could care less about the look, I'm more about the performance aspect, and David Raison has proven the concept in his Mini Transat finishes. If the twin bow concept does not prove to provide a similar benefit to the rounded scow bow, pounds hard in chop, and does not generally perform well in anything but relatively flat water downwind... then I guess its back to the drawing board, or simply modify my build plan to achieve the rounded scow bow.

     
  10. CloudDiver
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    CloudDiver Senior Member

    I also need to mention, in regards to the 7.6 M concept, the beam has to be limited to 2.5 M (over the road maximum without wide load permit). the Mini 6.5's already exceed that, so extending the LOA to 7.6M but narrowing the beam to 2.5 M throws off the proportionality, and to make things worse (or better, lol) I would want to bring up the freeboard and cabin height for a drier ride and reasonable headroom in the cabin. I'm not trying to win races with this design, just trying to capitalize on the concept of full beam width from transom to near bow, and hopefully get a little performance boost vs traditional hulls.
     
  11. pogo
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    pogo ingenious dilletante

  12. Jamie Kennedy
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    Jamie Kennedy Senior Member

    Looks a lot like an Optimist Pram shape, with its very blunt but somewhat narrowed bow pram. It is much less beamy than an optimist though, which should help some.
     
  13. CloudDiver
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    CloudDiver Senior Member

    The Musard 29 is a very interesting design, although it exceeds my maximum allowable LOA of 25 ft.

    the reason I am limiting myself to 25 feet is because of the least expensive mooring in my area is $600 USD per year, but limited to that LOA of 25 ft.

    Bouncing this idea around my head, I'm wondering if I can even get the Hull to plane if its at 7.6 M with a 2.5 M beam. Raising the freeboard and cabin height may add too much weight without having the same ratio of beam to LOA like mini 6.5's have.
     
  14. Cacker
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    Cacker Junior Member

    5.9 m plywood scow... :D
     

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  15. Cacker
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    Cacker Junior Member

    And another one 15 ft...
     

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