new user, old questions

Discussion in 'Boat Design' started by Freaky_1, Jan 10, 2010.

  1. Freaky_1
    Joined: Jan 2010
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    Freaky_1 Junior Member

    Hello all,
    Frank here. I'm looking to step into my next boat build and I'm looking to go a little farther than I have in the past. I'm looking for suggestions as to hull design at this point.

    I'm looking to build my first all steel hull ocean going cruiser. I'm currently uncertain on overall size, but we're looking between 32 and 56' long and as wide as is feasible. She'll be a pwr only vessel.

    My primary requirements are:
    Rough sea stability and durability
    ease of maintenance at sea (looking to spend months at a time out)
    fuel efficient (without giving up stability and durability) (more on pwr further down)
    ease of slipping (something that's going to be easy to find a slip for here and there)
    safety on the hook (expect to spend many a night on the hook)

    Now more on what the vessel is to be and do.

    The best way I know to go about this is to compare this vessel to be, to my last project. A few yrs ago, I rebuilt a 52 Thompson Trawler. She's a great boat and was a blast to do. I started on her as a bare hull. The superstructure had been burnt out. Completed, she is a snapper boat. Single 6v71 (that does not puke oil, yes that took work). She's got a covered deck and on deck fish boxes. She's a fine boat, but she's not what I'm looking for here. I do not want to build a commercial fisher, or even a sport fisher. I want a comfortable cruiser.

    I'll most likely be powering her with twin Perkins 4cyls. The main reason for this is that I have an abundance of them available, I know them backward and forward and can rebuild one in situation quickly, easily and cheaply. Another reason is that they are happy at many many operating load ranges. I'm not strictly tied to the Perkins 4 and have many other options, but at present this is on the top of my list.

    As you've probably realized by now, she'll be twin drive. The many reasons for this all apply, but the most obvious (if something goes down, U still have power) is the primary one for me.

    She's not meant to be a fast vessel by any means.

    I plan to cruise 3 people full time and I'm certain more at times, so I really want her secure in a wide range of conditions.

    She WILL be a single hull design in steel. This is the one solid stance.

    I am currently thinking of a radius chine design, but as I know little of ocean going vessels, I'm open to suggestions. I'm expecting deep vee, but still wonder about rocker or no.

    Lastly, this is a long term project. I've built many fresh water vessels over the years, but this will be my first of this sort.

    I'm certain there are things I've not covered here so please ask :)

    Thanks in advance
    Frank
     
  2. Freaky_1
    Joined: Jan 2010
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    Freaky_1 Junior Member

    Knife bow? low angle or more vertical?
    Hard chine or radius?
    Rocker or straight?

    These are the questions that occur to me at the moment.

    Oh and I'm planning a full keel with 2 skegs for protected wheels.


    Thanks again,
    Frank
     
  3. Gilbert
    Joined: Aug 2004
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    Gilbert Senior Member

    I would vote for single chine and a rather vertical stem but not necessarily plumb. Whichever choices you make, I would like to see a lot of straightness in the sections close to the bow. This will ease the motion when bucking into it.
    By rocker do you mean rocker in the chine aft in the profile view? If so I would vote for some of that but not a lot.
     
  4. apex1

    apex1 Guest

    "Ocean going" in this case means: passagemaking, blue water cruising, right?

    A deep V for sure is NOT what you want. That would be found on a runabout, not on blue water yachts.

    As Gilbert, I would recommend a hard chine for ease of construction. With twin keels (for sitting on the mud) a twin engine arrangement makes sense. I otherwise recommend single engines for passagemakers. The prop is easier to protect and you have less issues with a single diesel.
    When engines die, they do usually due to dirty fuel or fouled prop. No advantage for a twin setup. (the opposite)

    For economical cruising, and for always sufficient load on the engines choose a CPP. More info here:
    http://www.boatdesign.net/forums/props/controllable-pitch-propeller-summary-30695.html

    Due to your obvious demand in space, the upper end of the range of length sounds to be the one to go for.
    Width and economy are not going hand in hand on a displacement vessel. So, go for a longer and narrower boat if long journeys are planned. Brings another knot or two extra for free when the same space (displ.) is spread over the length not the width.

    Regards
    Richard
     
  5. Tad
    Joined: Mar 2002
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    Tad Boat Designer

    Frank....there's a great deal to your questions and I won't try to cover the entire thing, but here's a start.

    First two questions for any powerboat design are "How big?" and "How fast?". These two questions are closely interrelated, for instance a hull has to be big enough to carry the fuel required for a given speed and range.

    A range of 32' to 56' LOA is huge, so large a difference as to make any comparison meaningless. For instance the required power might double between the two. Fuel load for substantial range will be a huge factor in the smallest boat, while it would be a minor issue in the larger vessel.

    Longer will be faster, easier to push (lower resistance), more expensive in most other ways, and far more comfortable at sea. You mention spending months at sea, where? What sea voyages specifically are you intending? This tells us a great deal toward the speed/range issue which is the heart of the "How big" issue.

    See this for my thoughts on size..... http://67.15.157.5/~trawlerc/viewtopic.php?f=33&t=52&sid=7e0e702bba6cad1d6430e036e645465b

    On hull form a double chine hull can have very similar resistance to a radius chine....I have tank data to this effect somewhere. The only reason to do a radius chine (IMO) is if you are concerned about the aesthetics of the hard chines. Radius chine may add slightly to a vessels resale value.

    As to rocker...I assume you are talking about lifting the bottom aft? This is totally dependent on the design speed......you have to establish the length of the hull to state how fast she is moving through the water, only then can the form be finalized.

    My PL56 MKII in double chine steel is below.

    5602views.jpg
     
  6. Freaky_1
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    Freaky_1 Junior Member

    You are correct and thank you.
     
  7. Freaky_1
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    Freaky_1 Junior Member

    First off, thank you and "Deep Vee" was a typo of sorts. . while explaining what I was talking about (while typing) to my wife, I was comparing draft to our current fresh water cruiser and our runabout. The deep vee cruiser had a deeper draft (what I meant to post) and is much more stable. Apologies and thank you for pointing out that I even typed that.

    Length is a concern I'm working up to. My thoughts put my needs closest to 60' without hitting it. Again a typo of sorts 36 was taken from a vessel we worked a long time ago and was actually 44 LOA (which I should have typed) and 36 LWL. I've pretty much discounted the shorter LOAs but am willing to hear from anyone who would care to pitch for shorter vessels. We actually took the 44 (LOA) from HI to NZ in 1987. Wasn't the most pleasant voyage, but then again, she was a shallow draft vessel with no true keel. Not to mention that our fuel arrangement wasn't fun at all if you over look the hazards of how we carried extra fuel. At any rate for the purpose of this discussion, let's stick with 56 LOA as my intended.

    I should also mention that I left out a large portion of what this vessels use would be. In the off months, she'll be working the ICW as a live aboard "shop" while I work on other vessels (which our current Thompson 44 is used for). I don't want to get so long with her that she's hard to maneuver in tight quarters.

    Efficiency is a far greater concern to me than speed. I'm happy at 8 knots cruise.
     
  8. rasorinc
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    rasorinc Senior Member

  9. Freaky_1
    Joined: Jan 2010
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    Freaky_1 Junior Member

    I've corrected a couple "typos" above about LOA and "deep vee", but suffice it to say that I'm fairly certain that I want to go with a 56 LOA.

    As to width being as wide as is feasible, I mean feasible to design and use, not as wide as can be concieved.

    As to where, well, that's the catcher. I wont to have a vessel as equally at home for my work (ICW) as in open water (well as closely as the two can be related when in fact they are not). Where do I plan to go. I plan to retire to the vessel as a full time live aboard, not too far down the road and want to be as closely capable to going wherever we wish on our journeys.

    After some more reading and yours and other's thoughts here, I've discounted the radius chine. I'm looking for the best stability under pwr and on the hook as I can do and still retain the ability to take longer voyages. Now I'm curious as to the advantages and disadvantages of singer v/s multichine. Our earliest trawler experience (worked it for 4 yrs, did not own) was a multichine and now that I think of it, she was the worst roller on the hook in poor conditions. She was otherwise the typical trawler, 52' with full keel.

    Speed means little to me here. I'm currently happy with my 8 knot cruise speed. I'm more interested in fuel economy for the longer voyages. I realize the two share some design work.

    You are correct as to my terminology of "rocker". Again, my concerns here are fuel efficiency and blue water.

    I should add here that I'm currently holding Bruce Roberts design to the top of my list and if I go this route, I will send the cut files to a company that specializes in such and is experienced with his designs. In other words, I'm most likely to work from a kit here. It's not carved in stone, it's just where my current ideas lead me.

    I plan to start this project in the Fall of this year or the spring of the following depending on how long it takes to nail down the ideas to design and receipt of the cuts "kit". If it takes longer, it takes longer. I have the means and hopefully the life span. Since I have a current working Thompson, I can afford patience, which to me is the greatest factor.

    Current powering ideas are just that as I need to nail down my design to know what power I need. I have many options available to me here including a 350hp JD on the current "already have" list, and many more on the "can easily acquire" list. The only thing I'm relatively set on here is the use of a keel cooled system v/s raw water cooled, and this is only from my own experience, so open to discussion as is all.

    This is getting into a wide range and there is much more to decide, but right now I want to focus on the general hull design for my purposes, then pwr. I've still got to learn more about wet exhaust and many more topics that I want to focus on after the hull.

    Thanks again all!
    Frank
     
  10. apex1

    apex1 Guest

    If I were in your shoes, I would reconsider my choice of designer!!!!!
    I assumed already (as for sure some others here), where your "choice" came from.
    There are others, pretty able to design a true blue water motoryacht.

    No, I am not a competitor, I´m a boatbuilder.

    What is ICW?

    Regards
    Richard
     
  11. Freaky_1
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    Freaky_1 Junior Member

    Would sure like to! He has no true blue water designs, but he's the only designer I have any experience with and well, to have other options, I need other suggestions. LOL I'm actually considering working hand in hand with a design school and seeing how well the designs come out.

    ICW. Inter Coastal Waterway. Eastern Seaboard of the USA.
     
  12. apex1

    apex1 Guest

    Ah, thanks. I know the ICW! Went down there when i made my shakedown run with my first motorboat, a Hatteras. Centuries ago............

    TAD has some passagemakers (click his name), Michael Kasten (Kastenmarine.com) has some twin keels too. There are lots of good designs on the market. Nothing as cheap as the BR stuff, but you know: you get what you pay for. (sometimes even less)
     
  13. Tad
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    Tad Boat Designer

  14. Tad
    Joined: Mar 2002
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    Location: Flattop Islands

    Tad Boat Designer


  15. Freaky_1
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    Freaky_1 Junior Member

    lol thanks to those of you who posted to the thread rather than loading my inbox. BR is out. I know he has no real blue water designs and I know his structure isn't exactly desirable. Sadly I will now confess to first hand knowledge of the later.

    Even after paying for the plans, I ended up having to pay a great deal more for the final plans as the firm I had provide my cuts enlightened me on some large issues and put me in touch with the man who did the redesign, holding to the original look. I've actually been trying to get the man "Lisle" to design this one, but he's no longer a "free agent" and can't take on anything outside the firm he works for. Basically he summed it up to the firm won't take on a one off design unless it's a high end and they get the build. Not complaining, just mildly depressed not to use the one man I actually know capable.
     
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