Any hope for this one?

Discussion in 'Boat Design' started by afteryou, Jan 29, 2013.

  1. Tad
    Joined: Mar 2002
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    Tad Boat Designer

    Short fat boats have a much bigger resistance hump to get over prior to planing, long skinny hulls have a small or non-existant hump. This is where cats have an advantage. To reliably get over that hump your 10,000 pound boat will require 400 HP.
     
  2. afteryou
    Joined: May 2012
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    Location: Southeast Alaska

    afteryou Junior Member

    Thanks for the feedback guys. :D

    I don’t feel that I’m contradicting myself by stating what I would like. I read these kinds of threads often and continually people are saying that somebody needs to make a list (I forget what you guys call it) of the things their looking for in the boat, so I made my list.

    I understand boats and how they work. I understand trolling and how it works. Boats are my life and have been since I was born. I make my living both using and fixing boats and have been since I was 12 years old.

    I admit that the end result of my research will never meet all those goals. My purpose here is to “find out how close I can get” as yipster said earlier in this thread.

    I did not draw a napkin sketch because I wanted the people who know way more than I do to be able to make suggestions based on what they thought might get me close and not be encumbered with an existing hull shape.

    I looked at a few more bowpickers 26-28’ and like Tad said all the weight is aft with an outdrive, but I just don’t see how I am really that far out in space. These boats almost do what I want it’s just all that craps in my way in the stern. I guess I could haul in front of the wheelhouse, just no sharp turns to port when you haul the starboard or vice versa.

    yipster, I really like that graph. It sure makes you think about the displacement cat. I don’t think I’ve ever seen one of those. I would imagine that the hulls are quite narrow and not good for packing weight?

    Tad, I did not know we were buying Canadian permits. That sounds sucky I am going to look into that. Thank you.

    Sorry if I came across grumpy earlier. I really do appreciate the help. :D
     
  3. Stumble
    Joined: Oct 2008
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    Stumble Senior Member

    Afteryou,

    There are two different lists. The first is a SOR, that covers the mission statement of th e boat. So in this case "a fast, fuel efficient, trolling vessel, that is able to operate in roughy weather and unprotected seas, with the ability to stay out fishing for X number of days.

    from here you work down to a detail list. Which is just the list of what the boat MUST be able to do, what is is desirable for it to do, what would be nice if it could do, then any bonus stuff we might be able to throw in for fun. These needs should be prioritized, since there are inevitable trade offs that will need to be made. For instance you might require 15kn cruise, like 20kn cruise, and heck if we can get 25kn that would be cool.

    As an example of how this may work... Lets say the boat should be able to go out for 1 day... Well me may not need as much load capacity, since we only need enough ice for 16 hours or so. If we need to stay out for 2 days, we need at least double the amount of ice.

    From here you can start honing down on what the boat needs in order to meet its operational requirements.
     
  4. yipster
    Joined: Oct 2002
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    Location: netherlands

    yipster designer

    afteryou, cats.. love or hate them, many types and with various targets and succes plus new the pricing is higher
    just read an article by kurt hughes making a point on why all the speedbows while lenght water line counts in a displacement cat
    fish weight with or without ice? estimate that fish -since it swims in water- be around a liter volume by kilogram
    cats aint freighters, could be calculated tho, graph mentions 12 ton (by 14m)
    see ob's build into the stern but why not engines midships with propshafts under the fish tanks
    long deep small hulls placed wide give best economics but also less jerking cat motion, and there is more
    you have to check it out, didnt find what'i was looking for but here some quick links
    http://www.bayacht.com/why.htm
    http://www.boatdesign.net/forums/boat-design/displacement-catamarans-40279.html
    http://www.glacierbaycats.com/site/company/world-records-powercatamaran/
    http://www.yachtworld.com/core/list...30/AK/United-States&boat_id=2443730&noOfPic=1
    http://www.2hulls.com/archive/Gen Article/powerplaning.html
    http://www.bwseacat.com/images6.html
    http://www.bwseacat.com/images12.html
    http://www.powercatgroup.com/cat-hull-types
     
  5. afteryou
    Joined: May 2012
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    afteryou Junior Member

    Thanks guys, I started a list last night. I think I got most everything, but I will update it if I find something I left out. Feel free to let me know if you think I missed something. I hope this makes a little more sense to you guys than my rambling and wishing. :p

    yipster, thanks for the links I will look through them after I'm done getting dusty for the day. :)

    Has to
    (1) Hold 2500lbs salmon plus ice /water 3200lbs
    (2) 15kn speed light (minus salmon add1000lbs/ice water)
    (3) 10kn speed loaded
    (4) Be able to run in four foot inside water chop safely
    (5) Be able to safely break gear (as described previously)
    (6) Conduct fishing operations averaging 1.5gph fuel or less
    (7) Clear open stern (one outboard is possible but not two)
    (8) Hold enough fuel to last for three days of fishing with minimal running
    (9) Be less than thirty feet in length (no beam requirement)
    (10) Self bailing decks (trolling pit may be an exception)
    (11) Be able to house one person for three to four months at a time (doesn’t have to do it comfortably)

    Would like it if
    (1) It held 3500lbs salmon plus ice/water
    (2) 18kn speed light
    (3) 12kn speed loaded
    (4) Able to run safely in six foot inside chop
    (5) Conduct fishing operations averaging 1gph fuel or less
    (6) There were no outdrives or outboards involved
    (7) There was no wet exhaust involved
    (8) The boat was twenty eight feet or less in length (beam ten feet or more)
    (9) I could fish in the ocean with winds at west 25kn (pretty nasty)
    (10) The engine was mounted fwd of fish holds
    (11) House two people uncomfortably
    (12) The boat was economical to build (simple shapes nothing fancy)
    (13) Single engine
    (14) Diesel powered
    (15) Inboard shaft driven
    (16) It was able to fit on a trailer
     
  6. midnitmike
    Joined: Apr 2012
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    midnitmike Senior Member

    Now that's a lot better!

    MM
     
  7. JSL
    Joined: Nov 2012
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    JSL Senior Member

    m.f.v. Beyond Hope
    I have done quite a few Bristol Bay boats over the years (12' to 16' beam) and using their cubic number proportions (L 32' x B 14' x D 6') but shrunk to 24' you have a boat that is 24' x 10.5' x 4.6': about 42% of the size of a 32'.
    It could work but you will have to load and operate it like the 24' it is.
    Suggest: Hire a knowlegable person to help you, look around for an existing hull (FRP), or get one built (aluminum)

    ps: In an effort to gain deck area some fishermen add platforms (deck extensions) but this could literally overwhelm the boat... not a good idea.
    oops- missed the 2nd to last reply. You could probably 'chop' a 32 down to 30' (or less) but the cost savings will be minimal (if any).
     
  8. yipster
    Joined: Oct 2002
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    Location: netherlands

    yipster designer

    why puzzle costs when riding the hump (check froude and hullspeed)
    this one more link shows the power jump needed to pass hullspeed
     
  9. midnitmike
    Joined: Apr 2012
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    midnitmike Senior Member

    Well that's kind of a handy page ...thanks.

    Yipster, am I missing something here? Because who would have thought that I only needed 85 hp to hit 14.4 knots in a 10,000lb Semi-Displacement 32' hull. Wouldn't 85hp per ton be a more accurate estimation, or in this case 5 x 85= 425hp?

    MM
     

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  10. yipster
    Joined: Oct 2002
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    Location: netherlands

    yipster designer

    at first glance you seem rite, have to check later, used the rite buttons huh?
    havent played to much with this calculator yet but saw it recomended as pretty accurate
    bet if you stay below "hullspeed" you be even more amazed on power requirement
    thats what i'm trying to say: this graph i picked from a fishers forum for crist sake explains
    http://www.ifish.net/board/showthread.php?t=391543
    [​IMG]
    frictional resistance rises gradually with speed but the added wave resistance makes at "hullspeed" (18knts in pic) a jump
    the bow wave at that speed, the "hump" you have to step to get planning
    looks like by setting desired velocity's op plans to cruise at that peek resistance bow wave
    read speedbooat essy http://members.chello.nl/jadressh/ for more of my hullspeed blabla
    hmm,.. thought was a nice calculator.. will check latyer!
     
  11. afteryou
    Joined: May 2012
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    afteryou Junior Member

    Yipster, yep that black line is messing me up. If I understand this and I’m not sure I do. I would need a lot of horsepower to maintain 15-20kn. In essence keeping the boat on a hog which would be fine for when I’m loaded, but far from ideal when running light. Should I be shooting for something above 20kn light?

    Thank you :)
     
  12. afteryou
    Joined: May 2012
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    Location: Southeast Alaska

    afteryou Junior Member

    Did you confuse hp with kw?
     
  13. afteryou
    Joined: May 2012
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    Location: Southeast Alaska

    afteryou Junior Member

    Thank you for the positive feedback and the sage wisdom. I fully intend to hire a pro once and if I feel I have a workable plan.
    Question, what does m.f.v. stand for? I hope it's nice :D
     
  14. midnitmike
    Joined: Apr 2012
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    midnitmike Senior Member

    I don't think so. If you check the screenshot I took of the page you can clearly see that the HP requirements are being calculated for a 32' 10,000lb boat with a target speed of 14.4 knots. The HP supposedly required is stated at 84.97 and the KW at 63.39. Unfortunately I clipped off the bottom of the graph but I saw no mention of HP per ton or any other applicable conversion method. Please be my guest and visit the web site to run calcs of your own. I'm just wondering if I missed something along the way...personally I'd like to use this for future reference...but only if it works properly...or if I can make the conversion on my own...I'd be happy with that.

    MM
     

  15. afteryou
    Joined: May 2012
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    Location: Southeast Alaska

    afteryou Junior Member

    Sorry I did not check the website yet. I just noticed that yipster's graph was using kw and you where talking hp in my simple mind I jumped to a conclusion. Once again I should have just kept my mouth shut and listened. I should have looked more closely. Oh well, I was really just trying to help out please don't take any offence. I am more of an eyeball kinda guy. this thinking stuff makes my head fuzzy:D
     
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