rough draft of 28ft trailer/sailer/power cruiser with water ballast

Discussion in 'Boat Design' started by rwatson, Apr 6, 2008.

  1. rwatson
    Joined: Aug 2007
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    rwatson Senior Member

    The static water ballast would certainly be much more effective as low in the hull as possible, just like any other ballast. The complexity and bother of pumping water ballast out to windward ( eg at the sheer clamp ) might be an option in an exotic version, but that would have to wait.

    Very good observation.

    In this version, we have gone even more radical, and made the bottom of the transom much higher than a Mac to avoid stern drag under sail. The model is supposed to test to find out if the running trim under power will be acceptable for the driving position. This is the reason for the reverse sheer on the bow.

    I have been looking up commercial trim tab products in the event that we need to modify the hull attitude under power.
     
  2. michael pierzga
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    michael pierzga Senior Member

    Yah, I suppose..all the cool goodies are expensive and time consuming to build. Simple is probably best.
    A spray chine might be worthwhile...those Macs are pretty fast under power.

    I Took a picture of one motorsailing on a reach with the main still up. Really looked funny...must have been hauling *** at 15 knots or more. Water just peeling off the bow
     
  3. capt vimes
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    capt vimes Senior Member

    interesting project...

    but i would probably have a completely different approach.
    first of all, trailerable is not on my SOR - i do not even have a car... :)
    so the starting point is very different, but you might consider my approach and probably could incorporate some into your design...

    when i see something like this, i always ask myself:
    why going from a mere sailboat hull-type and change it to be somewhat a planing motorboat, if a more motorboat style hull could be changed to a quite good sail performer?
    take a deep V-type hull with lifting strakes along the chine line and "smooth it out" somehow to cope with sailing requirements.
    the ballast would be deeper in the hull adding RM...
    form stability would be increased due to the lifting strakes... (i would build it with more beam since i do not care, if i could trailer it or not)
    even with sails it would be able to plane as easily as under motor (enough sails and RM provided)...
    a ballasted swinging keel increases RM further, but the casing would take some space in the cabin which doesn't matter that much, if it has more beam...

    well - essentially i would try to "size down" project amazon from eric sponberg - more or less... ;)
    http://www.sponbergyachtdesign.com/ProjectAmazon.htm

    but what do i understand not being a NA... ;)
     
  4. rwatson
    Joined: Aug 2007
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    rwatson Senior Member

    Changing the SOR is a way of saying 'Lets gave a totally different boat'. There are plenty to choose from. The full logic is outlined at http://schoolroad.weebly.com/hybrid-yachts.html

    I think it was Phil Bolger who said "The best boats are ones you can live in, or the ones you can take home'

    A 28ft Trailer Sailer is the closest combination to both these major benefits. Large enough to provide comfortable, fairly roomy accommodation, while light and small enough to take home, for use as additional living space

    The room in the cabin is important, and that's why I have opted for twin daggerboards, one each side of the cabin.

    More beam IS important, but being able to container carry the boat is more important to me. This means I can travel the world with my boat, without the dangerous, boring expensive ocean crossings in between.

    So many options to choose from, so many choices.
     
    Last edited: Aug 5, 2013
  5. capt vimes
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    capt vimes Senior Member

    i understand your choices and your SOR, i was not trying to convince you to change it...

    i simply tried to point out, that a flat, slightly veed hull with tightly rounded chines is not good to sail and neither is it a good form for planing under motor...
    well - sailing it, might be less of a pain... ;)
     

  6. rwatson
    Joined: Aug 2007
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    rwatson Senior Member

    haha - good of you to care :)

    Actually, you made many other 'off the point' suggestions, but the two mentioned above are worth chatting about.

    I am not sure if you are referring to the latest design, as those very points have been a subject of huge revision since the initial concept was 'floated'

    While I am not at liberty to share the total lines, here are some sample sections from the current design. As you suggested, hard chines are the 'de rigur' with added bouyancy towards the sharp bows.

    As you say, much better performing both motoring and sailing, and even better, easier to build
     

    Attached Files:

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