Looking for a design

Discussion in 'Powerboats' started by Rylo, Jan 18, 2020 at 2:40 PM.

  1. Rylo
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    Rylo Junior Member

    Hi , new to the forum as a member, but very long time lurker here. Previous liveaboard on steel dutch barges in the rivers and canals of mainland Europe. We have owned 4 steel boats and one wood epoxy. Hated the wood epoxy, and love metal boats.
    We have done long term living and cruising on our 18 meter barge, and our 10 meter barge so I have a fair bit of boating experience and I know what I want.

    We are used to steel barges, so we are not looking for a yacht looking boat, or a high finish. We have refitted the interiors of all our previous boats, ourselves and I have extensive steel shipbuilding experience.

    I would like to find plans for a salty looking, fuel efficient, workboat style, steel/ aluminum liveaboard POWER catamaran intended for the main canals and rivers of Europe ( not the Midi. I know my critical dimensions needed for the waterways we want to travel. We have done most of them already) and extensively in the Med, and Baltic.

    Also, for travels much further afield if we get the notion in the future.

    I want a tough, simple, economical, and more importantly, SAFE , family live aboard.

    I like some of the points of this boat https://www.boatdesign.net/attachments/janthina-p-4-001-jpg.108201/ that was mentioned here before in a thread about steel powercats

    I like the look and layout of this boat, really shippy, but its not seaworthy (meant for lakes and rivers), it has a bad engine setup, its a homebuild with no plans...and everyone says steel is not good for a small catamaran. Its also too small really, but not by much
    Muu merkki katamaraani, omavalmiste motor boat 2000 - Heinola - Nettivene https://www.nettivene.com/en/moottorivene/muu-merkki/687609
    I love the back enclosed transom , really seems safe for children... love the access to the fly, love the front boarding ladder, ect ect.... In fact the whole thing is really exactly what I am looking for, but with a raked front window, seaworthy and long range

    I saw this, its almost right technically, but its a one off and not for sale. Good specs though and long range. Dont like the styling much of the back deck.... love the trampolines. Best part of a catamaran by far
    Photos https://bluenomads.blog/our-boat/photos/

    Also, this fellow seems to do something interesting, but Im not sure of the
    dimensions of his 40
    jutson.ca http://jutson.ca/blog/page/2/

    I need

    under 15 meters
    under 5 meter beam
    no more than 1.20 draft
    no more than 3.50 air draft.... but with a fly! so, folding?
    Hopefully trampolines on the front....
    Living all on one level....

    Anyway, maybe there is someone one here with a powercat design at this spec, or know of one?

    I dont want to blow my budget on commissioning plans/design. So Im hoping to get something stock that I can modify slightly if need be.

    I would love to build in steel, Im a steelworker and project manager by trade, but apparently, steel is a no go for a cat.
    Is this because of speed/weight?
    Because honestly, Im not looking to go more than trawler displacement speeds.
    We are slow boaters. So if it would work in steel, I would go steel. I know steel boats really well. And I love them.

    Definately want a power catamaran. We dont sail, and we dont like rolling

    I could build something similar to the steel Finnish boat above from existing plans no problem, and love every minute of it. But Aluminum is not my forte.

    Thank you kindly for any input, and please, go easy on me... :)
     
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  2. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    There is no problem using steel on a displacement catamaran of about 15 meters. If you are really set on a design in aluminum, changing to steel will not involved too many radical modifications. Which Finnish boat do you refer to?
     
  3. Rylo
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    Rylo Junior Member

    Hi Gonzo, thanks for the reply.

    That is really really interesting to hear. I would much prefer to work in steel, for many reasons, not the least being, its my expertise area. And I have capable crew for steel.

    The Finnish boat I am referring to is in the original thread above
    Muu merkki katamaraani, omavalmiste motor boat 2000 - Heinola - Nettivene https://www.nettivene.com/en/moottorivene/muu-merkki/687609

    So many aspects of this boat are perfect for what we are trying to achieve, but unfortunately, its not seaworthy, or we would just buy it, and remodel the interior. we are really modest boat people. not flashy or yachty at all.

    We in fact even had that boat surveyed, we liked it so much. Thought about re-powering, remodeling ect. I know its not typically beautiful, but it is a great living space in a small package. But we were told after survey, although the boat is really well made and in great condition, its only a coastal boat and only in very fair weather. And the fellow who built it didnt use a naval architect or plans, so ya, thats not the best I guess.

    We have a lot of experience living aboard, and everything is easier living , building, outfitting and remodeling when your boat is a boxy design. Thats why barges are such nice liveaboards.

    If it were seaworthy, and 12-13 meters, it would be the perfect boat for us.

    What are the characteristics that could make this seaworthy? Deeper draft Im assuming? Longer length?

    Sorry, I hope I dont sound stupid. Im used to building/repairing cruise ships, so in fact havent got the experience to know these kind of parameters for seaworthy small craft. I just used to look at the plans, and weld my small section.....

    Now I manage workers to build floating FPSOs but thats also a whole different kettle of fish.
     
  4. gonzo
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    gonzo Senior Member

    I tried to look at the site, but don't understand what it is asking me for. I don't want to click on something that may give access to my computer. Otherwise, it looks like a pretty straightforward design.
     
  5. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    Except that the steel structure will weigh around 2.8 times more than that of aluminum. That "smallness" will make it necessary to calculate all the hydrostatic properties of the ship, its scantlings, the stability in the various loading conditions, ... in short, little thing, "not radical modifications".
     
    Last edited: Jan 18, 2020 at 6:45 PM
  6. Mr Efficiency
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    Mr Efficiency Senior Member

  7. Rylo
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    Rylo Junior Member

    yes i do know boden plans, thanks Mr Efficiency (that looks funny when I type your name like that),. its not really what we are looking for.

    I have been scouring this forum and others for over a year and have read , I think , every existing thread on steel power catamarans. And about every thread on Aluminum ones too. It seemed to me that in the end the consensus was, don't do it in steel. not possible.
    Now i get why that is, too heavy I think, yet one thing that stumps me a little, is the Dutch have been building small steel boats for ever. Like, almost every boat in Holland is steel. Even small 9 meter cabin cruiser types.
    We have bought all our steel boats In Holland.
    Last boat we had, was 6 mil steel 10 meter canal boat. 48 hp engine. Strong as a rock and motored really well. A homebuilt boat. totally simple. And didnt seem too heavy, handled great, but what do I know.
    So , why a motor cat in steel wouldnt work is confusing to me.
    However, thats why im here, to get professional opinions, not my own musings. And understand

    Because the consensus seemed to be, no good in steel , I had resigned myself to looking at an aluminum build.
    Problem with aluminum, I'm going to have to hire out all the welding the work for sure.
    Im not an aluminum welder, and as has been mentioned its really specialised work. Im a perfectionist, and amateur work wont cut it for me. I could learn, but I havent got a year to dedicate to screwing up until I get good. I know when things should go to another professional
    Also, any welding repairs will have to be hired out in the future, and thats not too appealing to me.

    So of course I would prefer to do steel.
    But if its not a good idea, I will respect that.

    Tansl, this is why I was worried about doing steel, its like commissioning a whole new set of designs I think to have to do that, am I right?. And this could cost 10s of thosands of euros..

    Gonzo, dont worry ,its just the EU privacy regulation, in Finnish language, asking you if you accept cookies I think. its a buy and sell website, like craigslist. In the EU they have to inform you when they are using cookies . transparency or something. and yes, its a simple boat. Thats the appeal I guess.

    Thanks for all the feedback, keep it coming
     
  8. TANSL
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    TANSL Senior Member

    You do not have to discard the idea of the catamaran in steel. It may not be the right material, but it is not a material to be rejected. Probably in Denmark it is not built in aluminum because of its higher price and the difficulty of welding. Reasons that can convince you also to choose steel.
    It is not entirely true that the weight is 2.8 times greater. The steel is more resistant and can lead to smaller scantlings than in the case of aluminum, so the weight ratio would decrease. But if it is true that the design of the ship would have to be adapted to the new requirements, doing some naval architecture calculations. However, without knowing the SOR of your boat, you cannot correctly calibrate the options for one material or another. And, probably, the price of redoing the design and creating the construction plans of the structure, including information for cutting by numerical control of the pieces, is less than you imagine.
     
  9. Mr Efficiency
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    Mr Efficiency Senior Member

    If your intent is to travel at a sedate speed, then steel and extra weight won't be a problem, if you want the option of the lively pace of a fast displacement cat, it will be a tough essay. What needs to be understood, is that to get reasonably economical speed out of catamaran, you need slender hulls and relatively light weight, but if you want to plug along at six knots, it really doesn't matter if both of those requirements are not met. But to get speed out of a cat that is heavy and fat-hulled, will require a lot of engine power, and fuel
     
    Last edited: Jan 18, 2020 at 10:12 PM
  10. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    You mentioned the power cat Janthina - she was built in plywood in the 70's, but I think her hull design could be fairly easily adapted for steel by making the hulls a bit wider / fuller to give her some extra buoyancy re the increased weight of the steel.
    Attached below are scanned copies of the full article about her :

    Janthina 1 001.jpg
    Janthina P 2 001.jpg Janthina P 3 001.jpg Janthina P 4 001.jpg
    Janthina P 5 001.jpg
     
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  11. bajansailor
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    bajansailor Marine Surveyor

    I designed a 12 m. (39') x 4.88 m. (16') steel catamaran floating bar here back in 2001 for a chap who wanted to set up a beach bar, but he couldn't afford beach front land prices - I will attach a few photos.
    The only reason we went for steel at the time was for perceived (then) economy as an aluminium hull would have cost about twice as much to build.
    However in retrospect now this was a mistake - it would have been less expensive in the long run (re maintenance) if she had been built in ally.
    One reason being that the Builders were supposed to have blasted the plates and frames before assembly, but only the outside of the hull was blasted at the end, and this was our ultimate undoing.
    If she had been blasted and painted properly from the beginning, I am sure that she would still be working well today.
    RP at Mullins.jpg Rumpy Pumpy _0001.jpg Rumpy Pumpy _0002.jpg Rumpy Pumpy _0003.jpg Rumpy Pumpy _0004.jpg
     
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  12. bajansailor
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    bajansailor Marine Surveyor

    And 10 years ago I was involved in a project with BNTCL (the Oil Terminal here) to supply them with an Oil Spill Response Boat (OSRV) - we finally chose Alnmaritec in England as the Builders, and everybody was very happy with the final result.
    Here is a link to her -
    ALN 096 ‘Responder 1’ https://www.alnmaritec.co.uk/component/zoo/item/aln-096-responder-1?Itemid=289

    I later asked Alnmaritec to put together a proposal for building a catamaran houseboat for the Tobago Cays Marine Park rangers in the Grenadines, but this project never progressed further than proposal drawings.
    The vessel in the attached PDF is 12.8 m. long, and 6 m. beam; she would be a bit more seaworthy than your Finnish cat, and her hull form is basically the same as the OSRV (which we took out on sea trials off Newcastle in April 2010 in about a F 5-6, , and she coped pretty well).
    She is already pretty heavy at 12 tonnes on a 40' length; a similar size steel hull would of course be heavier, but the hull depth could easily be increased to suit (her draft is noted as being 0.6 m., but the draft scaled off the drawing is more like 1.04 m.) as I see your max draft is 1.2 m.
    Your maximum air draft is 3.5 m., which would be up to the top of the roof (the flying bridge would have to be very foldaway!).
    And her beam is 6.0 m., but your maximum is 5.0 m.; the spacing between the hulls is 2.0 m., and I don't think I would want to go less than 1.5 m., which means that your hulls would have to be narrower and even deeper again, which would probably be getting very close to (or exceeding) 1.2 m.

    But there could be some ideas here for possible inclusion re your boat?
     

    Attached Files:

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  13. Mr Efficiency
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    Mr Efficiency Senior Member

    "Janthina" looks to fit the bill, if he can find plans
     
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  14. TeddyDiver
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    TeddyDiver Gollywobbler

    Dunno why but you are maybe a bit obsessed to have a cat as your SOR fits better to a monohull IMHO. The same dimensions 5m x 15m max will produce about the same rolling characteristics as a cat, You get the the same living space with lower superstructure and thus lower CG and better stability for offshore. It's better suited for steel and you had no need above displacement speeds.

    BR Teddy
     

  15. Rylo
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    Rylo Junior Member

    hmmm lots to chew on, thanks all.
    Teddy, our feeling about the cat design was better stability on anchor. We will be anchoring a lot, Med mooring is expensive. At least where we want to spend the summers, Italy. We dont have a home, so will be living aboard full time again. We want to be able to retreat to the canals in the winter, and spend summers in the sea.
    As we are used to canals and rivers, we are not really into the rolling motion of the sea to liveaboard. Everything I've read is telling me that without some active stabilising sytem, being in a mono at anchor can be pretty uncomfortable

    I lived aboard a 8 meter catalac long ago in the Panama canal (didnt sail her ever) and even in that small boat, the roll was almost not noticeable, even when a huge cruiseship would pass by me.

    Do you really think there wont be a difference?
     
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