Statement of Requirements – Foveaux Strait Commuter

Discussion in 'Boat Design' started by FoveauxSailor, Sep 4, 2015.

  1. FoveauxSailor
    Joined: Apr 2004
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    FoveauxSailor Junior Member

    The requirement is for a powered vessel to carry 4-5 persons (one or two of whom may be children) and their weekend baggage across Foveaux Strait. Total Payload 550 Kgs. Seated shelter from the elements is essential for all persons. A toilet with privacy is highly desirable. The vessel will live on a swing mooring so needs to carry a small dinghy on deck.

    The speed requirement is a flat water plane of 20 Knots, and a rough water speed of 8-10 knots, with an effective range of 100 NM.
    The vessel is to be as simple and plain as possible, built in either wood or aluminium. Basically the minimum cost to achieve the requirements but there is no constraint on dimensions particularly length.

    So can you suggest suitable designs for either amateur or professional build, or existing craft for inspiration? Or maybe considerations to submit to a designer?

    Background:
    Foveaux Strait, between the southern South Island, New Zealand and Stewart Is. is a somewhat challenging waterway about 20 NM wide. It has frequent periods of light weather (considerably more than most people think) but at short notice can produce the atrocious conditions common to waterways that are shallow (its average depth is about 30 meters) with strong tidal flows and strong winds. The water is very cold, and it is a high rainfall area. The Strait is very “open” so one feels very exposed even quite close to each end.

    Weather forecasts by both professionals and locals are frequently “surprised” by actual conditions.

    I have crossed Foveaux Strait about 50 return trips in my current boat “Otter”, a 24’ double ended sloop which is a wonderful sea-kindly boat that really looks after its crew. It takes a minimum of 4 hours, and frequently upwards of 6 hours, which even on the best weather forecasts allows a lot of scope for things to change. It is not a trip that is made lightly and I have never taken anyone but experienced persons along with me, one misjudged crossing can literally put women and children off the sea for ever.

    So I want the minimum vessel that can zip across fast in good conditions (considerably reducing the chances of a weather surprise) but one that will be able to plug along briskly in relative comfort should conditions deteriorate – the maximum anticipated sea-state would be that raised by 30 knots of wind after one hour i.e. having to make the home port of Bluff directly into a Nor-west wind that has come on much stronger than forecast. In this scenario there is a nasty wind against tide sea-state in a 5 mile radius around Bluff Hill.

    I do have some designs in mind as “likely candidates” but would rather hear what “open minds” suggest before disclosing my thoughts. I have read as many of the light displacement/efficient planning threads on various forums as I can find.

    Thanks
    Foster (aka foveauxsailor@gmail.com
     
  2. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    The Bartender 22'. It'll take care of you when it gets rough and can zip along when it's nice.
     
  3. Mr Efficiency
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    Mr Efficiency Senior Member

    Are you planning on relying on one engine ? If so, what prospects are there of getting timely assistance in the event you lose power ?
     
  4. FoveauxSailor
    Joined: Apr 2004
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    FoveauxSailor Junior Member

    That is a question I've been giving some thought to . . . we do have a coastguard but relying on them is pretty fraught as they do not "patrol" and are reliant on volunteers for crew.

    It seems that modern outboards are a good bit more reliable than in the past, a good number of commercial craft "in survey" here are now gaining compliance with single engines where 10-15 years ago they would have had to carry an auxiliary.

    However if the craft could bear the weight penalty of say twin 40's then I'd seriously consider it as an option. The further problem is that often its factors beyond the mechanical function of the engine that cause issues e.g.dirty or contaminated fuel - and that can kill both engines . . .
     
  5. Mr Efficiency
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    Mr Efficiency Senior Member

    With children on board you don't want to be bobbing around for hours waiting for assistance. Dirty fuel is largely fixed by fuel filters and water traps. If it is just an occasional trip, 40 Nm round trip is not going to break the bank fuel-wise, but twins always use more. I'd be looking at power cats in the 7m range. But you'd need 2x100 hp at the very least. Should be an easy two hour one-way, but of course it won't always be possible, and you'd probably want to pick your days whatever boat you select.
     
  6. Pericles
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    Pericles Senior Member

  7. whitepointer23

    whitepointer23 Previous Member

    That is not a design i would want to be caught out in when the weather blows up. We have similar conditions here to the o p. Bass straight can go from glass calm to 40 knts and rough as guts in minutes. Here you only see deep v mono's . Sharkcats and displacement hulls. Never flat bottom skiffs. I realize this one has a slight v but not much. If i was a kiwi i would see whats around in local designs because every boat i have seen from there has been a good rough water design.
     
  8. whitepointer23

    whitepointer23 Previous Member

    What about an easy driven cat with long slender hulls. Have a look at gropers thread.
     
  9. PAR
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    PAR Yacht Designer/Builder

    Again, hits every box on the list. Economical, seaworthy at both low and high speed, well regarded, 2,200 pounds with modest outboard, small cabin when a squall pops up, etc. It's a traditional build and I'd like to see it updated for taped seam, but none the less . . .

    http://www.bartenderboats.com/22-foot-bartender.html

    Tad Roberts has done a new one, specifically to address slow speed operation.

    http://www.bartenderboats.com/images/TimberCoast 6-9-2009.pdf

    While I don't think this version can get up and plane off, but it doesn't need much engine either. A 15 - 20 HP engine with 1/2 a gallon per hour fuel use, isn't anything to brush aside. Stately, economical progress in the conditions you anticipate.

    https://www.youtube.com/watch?v=fCD-1ozEbbI

    This is an old video of USCG trials for the 22. Check out the low speed handling at the beginning and end of the clip. I'll let Tad comment on their low speed handling qualities, as I'm sure he's been on more of them than I.
     
  10. whitepointer23

    whitepointer23 Previous Member

    I like the look of the bartenders. I remember them back in the seventies but they were not popular here for some reason. . hartleys are a good boat too.
     
  11. PAR
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    PAR Yacht Designer/Builder

    Australia used them as surf boats. Pretty tough duty for any boat, if you ask me.
     
  12. tom28571
    Joined: Dec 2001
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    tom28571 Senior Member

    This was posted on another site but the OP repeated his SOR here.

    My Bluejacket was mentioned and while I am happy with the design, I agree that they are not the best choice for your needs. I will say the same about the Tolman or any other similar monohull as, legend aside, no low deadrise monohull is going to be comfortable in rough water over 20 miles. A Bluejacket will make this passage as well as any other similar boat, regardless of legends. It is possible that a catamaran could do the job but the problem of slamming on the underside of the bridge deck can make them even more uncomfortable than a monohull in rough going.

    An unavoidable fact is that all boats can be uncomfortable in some conditions. Deep V hulls can make the most speed in rough water but even they can be tough on the occupants. Perhaps the best choice would be a semi-displacement hull. The German Schnell boats of WW2 were probably the best monohull sea boats ever built. A smaller version would be my choice. Look at this video for a first hand look at a Schnellboot: https://www.youtube.com/watch?v=ec4XwB1Jg94 William Hand designed such boats a hundred years ago and his Piute design has been copied by others such as Doug Hylan with his Top Hat and Harry Bryan with the Handy Billy. The Piute is known as a good seaboat for speeds up to the high teens and able to run at your desired speed in rougher water.

    Calkin's Bartender is popular with inlet runners. Its a good boat and extremely seaworthy but don't think the passengers aren't getting some rough treatment inside while it bangs and plunges around. Its virtue in waves is based on the hull bottom having severe twist with very a very sharp forward entry that carries much further aft than the usual warped V type. That is combined with a modified dory (narrow) waterline beam to give its seakeeping while sacrificing interior room for the length. Bartenders will usually have horizontal plate wings under the waterline aft to help it get on plane. May be the best if length is a factor.

    There is no magic and no free lunch.
     
  13. Mr Efficiency
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    Mr Efficiency Senior Member

    It is particularly difficult to select a suitable small boat to operate in adverse conditions, "on demand", I don't think where children are involved there is any such vessel. If you have a lot of latitude to pick your times to cross this strait, it opens it right up, but if these are "weekender" trips, you will need assurance out to two days at least, that conditions will be OK for the return. I'd look at what the local volunteer rescue people use, because they do get called out where it is unwise to be out, so they need something that is seaworthy for local conditions. But they don't have the very young or the old on board, as crew, if you do, it is fraught. I think really you have to select a boat that will be best suited to the return leg of your trips, taking into account what are the most likely axes of wind and weather changes, that bring the worst conditions, on that return trip, the one you are more forced to take, perhaps, or be stuck till the weather and sea improves. I have forgotten one of the most important matters, of course, the women.....they won't (bar the odd atypical dare-devil) look kindly upon uncomfortable or seemingly unsafe boats.
     
  14. FoveauxSailor
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    FoveauxSailor Junior Member

    Hmmm - for my sins I was on the committee that assisted the local coastguard on their new vessel project (I was included for my funding expertise, but participated in the design evaluations) and I can assure you that the qualities they seek in a boat are very different from a pleasure craft.

    In any case I am not talking about extreme conditions, rather the beginning of what happens when it starts to blow. I have made many crossings by ferry when it was deemed in-appropriate to go out in our own boats. The ferry by the way is a Cat, but I don't really like catamarans in the size I would be thinking of, even if I could afford one.

    This thread is one that I keep referring to http://forum.woodenboat.com/showthread.php?52991-The-Perfect-Powerboat-Design and it contains a huge amount of great data and opinion, very generously given I might add by some talented and knowledgeable folks.

    The "The-Perfect-Powerboat-Design" design thread offers tantalizing ideas of very carefully designed "V" angles for conventional length and displacement boats but doesn't pursue the "making these boats longer" paradigm to any extent.

    Just for example - how could Tad Roberts wonderful 26' Berry Point or Tom's great Blue Jacket be expected to perform at lengths of around 32' on similar displacement (noting that I don't require much in the way of accommodations, so I would hope a stripped out longer version would maintain something not far from the original displacement).

    Am I explaining this clearly . . . . I want to "plane" in nice conditions, but be able to slow down to a respectable speed based on waterline length when it gets rough. That way my passengers may get little anxious and seasick, and we'll take an extra hour of discomfort to get home, but at least I'm not pounding them to death like I see the contemporary craft doing, or taking a very long time to get in once they can no longer plane.
     

  15. Mr Efficiency
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    Mr Efficiency Senior Member

    The link to the other forum is not working for me.
     
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