Budget long range cruiser fit for Pacific crossing - Ideas ?

Discussion in 'Powerboats' started by KeithO, Jul 5, 2019.

  1. trip the light fandango
    Joined: Apr 2018
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    Location: Rhyll Phillip Island Victoria Australia

    trip the light fandango Senior Member

    "what type of foam is used to make surfboards." Polyurethane , it's very consistently fine and easy to shape, and the finished surface will absorb resin a little. Microsperes/Qcell can be applied before glassing, making the surface less delicate, it has slightly more resistance to sanding depending on ratios and stops the absorption, so potentially lighter overall.Epoxy should stop water ingress, it may become slightly damp permanently immersed[ moored] using polyester resin without a complete seal of epoxy to finish, inside and out.
     
  2. KeithO
    Joined: Jul 2019
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    Location: Michigan

    KeithO Senior Member

    I have been stuck with using any boat design software by the fact that I have been using a 32 bit linux distribution and I need 64bit... So that has taken a while to sort out since I needed to back up all my data and do some large file downloads. After a few days of investigation and collecting the files I now have a 64 bit version of Mint loaded and in the process of restoring files....

    I will shortly find out if Freeship works with my new OS and may need to investigate if Delftship will run under Wine....
     
  3. Niclas Vestman
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    Niclas Vestman Junior Member

    Hello! Interesting topic. I do have a clear favourite in this category. Not sure if it has been mentioned before.
    Kurt Hughes Multihull Design - Catamarans and Trimarans for Cruising and Charter - 38' Trimaran Trawler http://www.multihulldesigns.com/designs_stock/38tri.html
    And as far as I know, the good mr Hughes does have a few more iterations in mind. He posted a few fantastic renderings on his FB-page recently. I believe of a slightly larger version. And in adition to being crazy fuel efficient, it would also be suited for 20-50% solar propulsion, and/or small kite or simple fold up biplane freestanding cheap windsurf style rigging. Point being. With super low resistance hull, needing only about 5-15kW for economy 6-9 knots passage making (depending on size and conditions). The kite/biplane rigs or solar needed are very small, and cheap to buy/maintain/ replace. And solar is quite useful even at anchor for all systems inc AC. And an electric drivetrain does have significantly less components, wear and maintenance costs. And also offers safety, as a totally independent 2nd backup to the primary diesel engine that is needed when solar/wind does not suffice for propulsion, or as generator. And also useful for heating warm water or cabin air when needed.
     
    Last edited: Aug 16, 2019
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  4. Niclas Vestman
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    Niclas Vestman Junior Member

    After having given the concept some more thought, I like it even more. And I feel even more that the KHSD power tri koncept should be a winner.

    As far as I can see, he has done at least 3 versions. 38', 50' and ca 60'. The concept has also been tested by the US Navy, as well as a few iterations by other designers. Some as high speed ocean crossing vessel. Some as super economy cruising variants. The Ady Gill from whale wars, and Solar Odessy being exempel of Both. If googling trimaran trawler, you will find an orange 40'+ variant. And if googling solar trimaran, you'll fins pictures of RA, who did the great loop on solar and I imagine sub 100k budget, building his own 48'er. The latter averaging about 5mph on 2kW solar from a 4kW array. With 2x2kW Torqueedo for propulsion. And the hullshape of that boat being clearly sub optimal, making 8 knots with 8kW array plausible.
     
  5. Niclas Vestman
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    Niclas Vestman Junior Member

    There is really just one thing all these designs have in comon, that is really off putting. And that is the ridicously narrow beam. Making any livable layout impossible.

    Only there is absolutely no reason that needs to be the case. Those sleek designs come from traditional monohull sharpies and designers wet dream speed boats. Espescially when utilizing the trimaran form factor. The Amas will keep a 12:1 ratio waterline upright, even if the hull has a substantial flare and widens 3-4' either side above the waterline.

    And at a 35'-55' size range (maybe ca 48' being a budget optimum), the hull should be large enough not having slamming issues at the flares. Making it possible to build a super efficient hull, that van be shorter despite same cruising speed as the 55' mono. There by also lighter, cheaper and with significantly lower fuel consumption. Again leading to lower weight and load carrying capability. Combined with a watermaker we are talking a displacement low enough for mainly solar and support rigg sailing.
     
  6. Niclas Vestman
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    Niclas Vestman Junior Member

  7. KeithO
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    KeithO Senior Member

    Niclas, I have followed the work of Kurt Hughes closely, Im just not sure I am up for a multi hull vessel. The structural integrity part of the design and build is non trivial and you are automatically committed to using high modulus materials since multihulls have to be light to perform. I also question their survival in the worst possible conditions, if you read "surviving the storm" by Dashew (free PDF download now) there are many personal accounts where monohulls survived with damage, that many multis would not survive due to too much vulnerability from large cabin windows and flooding from waves breaking over the stern. For now I think I am in the monohull camp....


     
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  8. Niclas Vestman
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    Niclas Vestman Junior Member

    About software; Delft ship doesn't require any processing power to speak of. My suggestion would be to pick up a cheap used laptop, or cheap new mini-media computer. Should be possible to get for 100-300USD depending on preferences. Very useful for other similar situations, as well as back up unit. Especially when boating, those thingies tend to have their life expectancy cut in half ;-)
     
  9. Niclas Vestman
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    Niclas Vestman Junior Member

    About hullshape and design strategy/ form factor. I did a few calculations for comparison. Mainly on fuel consumption numbers in this thread, as well as for Kurt Huges 38' power tri, Pogo 32 and a few other.
    The results did surprise me, although they shouldn't have.

    As long as you don't put a brick shaped hull in the water, but a well designed boat, the fuel economy will be extremely similar at the same multipel of hull speed per 1k pounds. Especially when adjusting for differences such as lower energy content in petrol vs diesel, aso. Turns out that Nordhavn 46, Dashew 64, IW55, KHSD38 all have an adjusted burn rate around 7,5gph diesel per 1k nm and 1k pnd displacement (some what in exact numbers) @ around 0.85x sqrt(lwl). And actually that doesn't change much up to 1.1 or 1.2 times sqrt(lwl).

    And that is what shouldn't surprise us. As long as you keep speed well below hull speed. So the sharpie/ wave piercer 4-5:1 L/B or even 9:1 L/B trimaran don't have a clear advantage at those speeds.
     
  10. Niclas Vestman
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    Niclas Vestman Junior Member

    Well, there are other benefits as well as drawbacks to the narrow hull shapes. Mainly seakeeping and wind resistance as well as energy losses due to wave induced motions. But... there is an almost liniar relation between displacement and fuel consumption. And here's the main point. You only gain fuel efficiency with the sqrt of increasd length. But displacement increases almost by the cube of increasd length.

    My conclusions for fuel economy. 1) Decide on smallest adequate layout/space and load carrying capacity needed. 2) Plan for maximum weight saving, water maker being the most important. 3) Decide on requirements for rough weather and impact structural requirements (size also being part of the safety factor, and weight to a certain degree being related to durability). 4) calculating light weight high tech build expenses against increasd resale value.

    My guess is that a smaller design would be a wise choice. As well as not opting for a to narrow design. 1) A slightly wider form factor offers much more volume for the same weight. 2) It probably has a higher resale value and lower mooring fees. 3) A slightly smaller boat has a much broader 2nd hand market. 4) It has lower maintanence cost. 5) Needs lighter engine=less fuel capacity aso. 6) Is easier to single hand.

    I guess the main thing about IW55 was to build in alu, and keep interior/fitout/engine/systems spartan and light weight. 15k pounds is light for 55'. But if you only need 42', it's compareably heavy. A light weight 42' could be almost half -> half the fuel burn. The alu choice might be good from a durability/resale value point of view. And also environmentaly, since it is possible to recycle at 100%. Foam composite being not very good at all in that respect. On the other hand, a well built conposite and maybe part carbon hull, might be considderably lighter, and have a higher resale value. But to me, alu does really make sense, while steel on the other hand seems like a terrible choice.

    So as long as the more economical route of buying used is not an option, I would chose a smaller 40-45' design, that is a middle road between extreme narrow(IW55) och chunky trawler (Nordhavn). And buying used would have little to do with hull shape, and more to do with excelence of light weight structuraly sound durable engeneering/build.

    Just a few thoughts from a novice. Sorry for the lengthyness. And pls keep us updated on the development. :)
     
  11. Niclas Vestman
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    Niclas Vestman Junior Member

  12. KeithO
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    KeithO Senior Member

    https://www.hiswasymposium.com/assets/files/pdf/2006/Gelling@hiswasymposium-2006.pdf

    Sorry but those fine folks dont agree with your conclusion at all. They find a longer vessel more efficient to operate, more sea kindly with lower accelerations in severe weather and only slightly more expensive to build. Hull cost being only a fraction of total cost. Of course the longer vessel is loaded less per foot of length since the assumption is that one builds for equal load capacity when stretching the hull.

    length impact on operation.jpg

     
  13. Niclas Vestman
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    Niclas Vestman Junior Member

    "https://www.hiswasymposium.com/assets/files/pdf/2006/Gelling@hiswasymposium-2006.pdf

    Sorry but those fine folks dont agree with your conclusion at all."

    Well, as I wrote in the last post. I do agree regarding seakeeping and in sea efficiency. But... the paper you linked does not specify how the claimed efficiency benefits where measured. But they do mention fast vessels like patrol boats at around 81' operating at 0-50 knots. Those boats seldom operate at lower speeds than 1,5x hull speed and up to about 4x hull speed. The economy cruising speeds we where talking about earlier where 0,6x to 0.8x times hull speed. That is an entierly differet range where frictional resistance is more important than wave making resistance. So i belive that paper is 95% irrelevant reagarding slow passagemaking. But I would really be interested in some input from any of our forum gurus.
     
  14. KeithO
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    KeithO Senior Member

    The class of vessel being discussed is 50m in length with a "hull speed" of 16kts and I see a max speed of 27kts. So certainly a fast boat but Im sure they are not doing max speed when they have storm conditions, nor max speed all the time..... Even semi displacement boats have a fuel consumption that is proportional to boat speed.
    The point being that there are many reasons to want a longer more slender vessel with a fine entry, of which reduced propulsion thrust is just 1 factor.
    This thread is filled with expert opinions on how the entire project is going to be worthless without a $500k yacht interior and since it doesn't comply with the typical formula for slips in marina's that charge by the foot. I have detected a certain glee in the fate of Idlewild, which could not sell for a fraction of the money invested in it. So lets not waste time with thoughts of resale value.... For that school of thought you need to go out and buy a Dashew which are now no longer being built.
     

  15. Rurudyne
    Joined: Mar 2014
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    Rurudyne Senior Member

    Ultimately people seem to have a choice to make: do they want a yacht optimized to move far for relatively not much (longer, narrow) or optimal for sitting at the dock like some small get away apartment (shorter, wide).

    ... or a cat or tri...

    ... actually those amphibious RVs make a lot of sense...
     
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