Warthog 25 off-shore pocket cruiser

Discussion in 'Sailboats' started by kvsgkvng, Jul 9, 2018.

  1. kvsgkvng
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    kvsgkvng Senior Member

    I would like to discuss and ask for opinion about a sailboat for off-shore voyages and gunkholing at the same time when in shallow water.
    My first thoughts would be to have these specs:
    heavy displacement
    sufficient pay load for crew of two traveling extended period of time
    hull made of flat panels allowing construction in plywood, steel, aluminum sheets
    manageable to build by small/custom yard, or DIY project in plywood
    self-righting and self-bailing
    unsinkable (sealed compartments, flotation chambers)
    shallow draft and lifting keel
    6 ft headroom
    LOA 25 ft and 10 ft beam​
    I tried to satisfy the above parameters with this model and would be most appreciative if there are people who would kindly express their opinion, add something or critique any blunders. If there are questions about this model or the concept I would be most happy to answer them. Thank you.

    Edit: After listening to a few suggestions, I changed a little the drawings. Indeed it will not be a speedy vessel, but it should handle wind and waves well. I designed it so it would keep the course well. It has heavy ballast and enough payload weight for crew of two. The bilge keels and lifting ruder are designed on purpose to allow shallow draft of only 2.5 feet. It would allow gunkholing in shallow water. At the same time, while heeling at cruising angles, the bilge keel would allow sufficient performance. Theoretically it should cruise at around 5 knots in moderate wind and pickup with higher winds. Smallish sail area should do well in high winds. But it is all on paper, I wish I could build one. Thank you for help and your time.


    Below is unedited original design.

    Edit: removed excessive calculus material
    Last edited: Jul 12, 2018
  2. sharpii2
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    sharpii2 Senior Member

    It all depends on if it is built strong enough and has sufficient ballast for self righting. Are the bilge fins going to be ballasted?

    As for the hull shape, it seems a bit complicated. You will have to use many panels and some of them will have a lot of twist. The bilge keel will have to be thicker in order to survive accidental groundings. But other than that, it looks like a classic British bilge keeler.

    The sail plan is not shown. What do you have in mind? I suggest a low aspect ratio rig, which will probably extend past the ends of the hull.
  3. kvsgkvng
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    kvsgkvng Senior Member

    It took me some time to figure out how to paste images and videos in my posts and the print could be better.
    I did not concentrate on sail plan for now, just wanted to get a working hull.
    I would appreciate and value anyone's comments.
    Thank you.
  4. Doug Lord
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    Doug Lord Flight Ready

    Seems to me the forefoot(at the intersection of the stem and keel) is maybe a bit too deep and could cause steering problems downwind in some conditions.
  5. JosephT
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    JosephT Senior Member

    Not bad, but it looks a bit slow. You'll be going nowhere fast. The Sadler boats like the 26 below is a popular bilge keel type boat. They have a narrower beam and were good cruiser/racers in their day. It's got a bit more rocker for easier steering and & less drag. Solid, proven design. They don't make many of these types of boats any more. If you like to wake up in low tide and catch clams for a meal this boat might be for you.

  6. kvsgkvng
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    kvsgkvng Senior Member

    I listened to suggestions of Doug Lord and also updated sail plan.
  7. CT249
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    CT249 Senior Member

    Why such a narrow stern? You are losing form stability, payload, speed and cockpit space.
  8. Dolfiman
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    Dolfiman Senior Member

  9. kvsgkvng
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    kvsgkvng Senior Member

    Thank you for you questions, I think they are very appropriate for all sailboats.
    In this academic example I presented my understanding, approximation and interpretation of things.
    However in my mind narrow stern would be more appropriate for the intended purpose of this sailboat.

    Some factors are major and others are secondary offering much less influence to the design of this sailboat.
    The main purpose of this vessel is to withstand off-shore rough conditions as the main goal, to have compact body, be serviceable in shallow water, to have minimal moving part.
    Everything else is consequential.

    Here are a few reasons why I chose to have narrow stern ( it is not prohibitively small -- it measures 7' x 8' for 25' hull meanwhile).
    Closed cockpit offers drier, safer and more convenient sailing.
    Small cockpit offers less volume to be flooded and subsequently drained (not to compare to open cockpits).
    Smaller cockpit allows skipper to be near everything when needed.
    In following seas it provides less area to be pounded, flooded and subsequently drained.
    Narrow stern helps this sailboat to right itself in case of knockdown or capsizing.
    Narrow stern provides symmetrical waterlines at most cruising healing angles.
    Narrow stern makes hull structure more rounded, stiffer and stronger.

    Now I address complicated shape with many panels.
    For small production boatyard or DIY hermit smaller panels are easier to manufacture, handle and work with.
    Convex shape adds lateral stiffness to the hull, creates less wind drag and allows the hull to right itself with less effort.

    This sailboat is indeed heavy displacement, as it was originally envisioned, nevertheless it has payload of approximately 3,500 pounds sufficient for the crew of two for long passages while providing 55% ballast ratio.

    I agree the RM890 sailboat is very gorgeous and very indeed very modern looking 30-footer. I would love to be able to afford one at "about €83,000 (2017)," but I doubt it will right itself if capsized.
    Last edited: Jul 12, 2018
  10. valery gaulin
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    valery gaulin Senior Member

    Nice looking design! Like the look. What software did you use?
  11. Steve W
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    Steve W Senior Member

    Why such heavy displacement? Half that would still be on the heavy side for a boat that size .
  12. kvsgkvng
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    kvsgkvng Senior Member

    I use Delftship (older version) for general layout and building rough outline, then I use PolyCAD for stability and GZ curve, AutoCAD for detailing and I combine screen captures in Paint.NET. The numbers crunching is done with LibreOffice Calc spreadsheet. For video capturing I use OBS Studio. All of software except AutoCAD are free on internet to download.
    valery gaulin likes this.

  13. kvsgkvng
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    kvsgkvng Senior Member

    Agree, you are correct in that this sailboat is on the heavy side. But other small off-shore capable boats also are no ballerinas. Just look at a few of them:
    Flicka 20 2.5T 409
    Dana 24 3.3T 337
    Warthog 25 5.0T 324
    Aquarius Pilot Cutter 24 4.0T 496
    Blue Water 24 3.6T 466

    My idea is to have heavier sailboat to provide better stability and motion comfort at the cost of speed. Also, slow speed translates in longer time between landings, and it means more supplies weight required to drag along. Not to forget, there is 55% of ballast weight in this hull. The payload is about 5500 pounds. For a crew of two it is 2750 lb per person, which is in a ball park for long passages including spares, repair supplies, equipment, food, etc. I agree Warthog could be just a bit lighter, but not less than 4.5T
    Looking at most off-shore sailboats, they all have similar specs. The shorter the boat the heavier it becomes relative to the length. And yes, you are correct, it is possible to cross oceans in proa, open lifeboats and reeds-made Kon-Tiki
    It all boils down to what one particular person likes, because any hull, heavy, medium or light weight have their own advantages and flaws.
    Are Heavy Displacement Hull Forms the Best Choice for Offshore Cruising? https://www.sailboat-cruising.com/displacement-hull.html
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