Small Steel Workboat Design

Discussion in 'Boat Design' started by Ozparker72, Mar 24, 2014.

  1. Mr Efficiency
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    Mr Efficiency Senior Member

    I think you are right, if it is 3mm steel, shapes with lots of surface area are doomed as you put it !
     
  2. rustybarge
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    rustybarge Cheetah 25' Powercat.

    If you look at the Tv program 'Burma Wild', on BBC 2 'On demand' from a couple of weeks ago, the expedition transported two tons of camping and camera equipment on a plastic pipe raft up a fast flowing river.

    So the idea has legs :D
     
  3. Ozparker72
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    Ozparker72 Junior Member

    Well ive done a drawing for my workboat, my hope is that it will plane with a 25hp engine (my mates got a spare).

    If I build with 3mm steel plate, the total dry weight will be 347 kgs, I know that sounds low for steel but I have done the calcs, the plate comes to 15.1 meters sq (including buoyancy tanks) @ 23kg's per sq meter.

    I would really appreciate any opinions, please feel free to rip it to shreds,
    I always prefer to make mistakes on paper!

    "If" this design is any good, but its just too heavy to plane,
    then I might consider building wood on frame, with a heavy lay-up of fabric and epoxy. Then just fender it to death

    14ft 5" Length
    5ft 5" Beam

    Thanks Oz
     

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  4. Ozparker72
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    Ozparker72 Junior Member

    And If built from 9mm marine ply and epoxy (heavy cloth) approximately 140 kgs.
    This would be quite "robustly built".
     
  5. waikikin
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    waikikin Senior Member

    Is that the total steel weight including any additional framing/stringers... are the buoyancy tanks/seats? longtitudinal? An angled transom to suit the outboard will help to gain full range of trim 12 degrees rings a bell. The angled portions of the bottom wont add so much planing/effective lift area.
    Ply will give you more payload, there's always plenty of stuff to weigh you down. I see you have some lift in the sheerline, anything with a "swim end" will float a little bow down at rest due to lower buoyancy & the overhang.
    Jeff
     
  6. Ozparker72
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    Ozparker72 Junior Member


    Hi Jeff
    thats the total weight of the finished boat seats tanks etc, maybe add 10 kg's max, to beef up the transom.
    I was going to put in 2 buoyancy tanks, sort of tank/seat combo's
    I at the stern and was thinking of building the other midships, trying to keep the weight as far back as possible.
    But I'm open to any suggestions.


    I was thinking of adding a bit more lift to the sheerline for that purpose


    "The angled portions of the bottom wont add so much planing/effective lift area."

    should I reduce the size of the angles? or maybe just have a single chine?
    I put in the double chine to give the boat a stronger shape/form, so that I would need less framing (weight saving)

    so if I put the transom at 12 degree angle, then do you think this could work in steel at 350-360 kg's with a 25hp outboard?

    and or, would this design work in ply/epoxy at 140 kgs?

    cheers mate
     
  7. waikikin
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    waikikin Senior Member

    I think your going to struggle with 25HP. The aluminium oyster punts here of around 6 meters seem to use 40+ but more often 60
     
  8. Ozparker72
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    Ozparker72 Junior Member

    Well, as much as I would love to build a small steel workboat, I now realise that I can not fulfil my requirements with steel, at the size of boat I need!

    Instead, I am going to buy plans for John Welsfords "Trover"
    Build it strong and encase the gunnels with thin gauge stainless steel.
    Thankyou all so much for your help and advice.
    it has stopped me making an expensive mistake, that I can't afford to make.

    Regards Oz
     
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  9. rustybarge
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    rustybarge Cheetah 25' Powercat.

    Good decision!
    I use an very old 13' Del quay dory['70's], the one with the GRP cathedral hull, and it is super stable and easy to drive; your 25hp will put on the plane with 3 people onboard and max out at about 20kts. It would cope with 500kg no problem. The bottom is protected with ss bands, so it won't get damaged grounding. You can walk around the boat on the gunnel and it will only tip a couple of inches!!!!

    You can pick an old one up for buttons. Highly recommended.
     
  10. waikikin
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    waikikin Senior Member

    Looks like a great choice..... or a choice choice, with some valid roots.
    http://jwboatdesigns.co.nz/plans/trover/index.htm

    Jeff.
     
  11. Ozparker72
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    Ozparker72 Junior Member

    Hi Rustybarge
    The Dell Quay Dory sounds great, think it would suite my needs well.
    I've had a quick look on apolloduck they seem to be selling for £3500+
    That's a lot of buttons!
     
  12. rustybarge
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    rustybarge Cheetah 25' Powercat.

    There are cheap copies which are just as good; google 'Wilson flyer', you can buy a new hull moulding from him without any fittings for very little.

    NB: he doesn't have a website, you can find his adds in Sea angling magazine. From memory a new 13' hull is about £800.

    Look for very old Dell Quay hulls from the 1970's, they are built like the proverbial brick house with unsinkable heavy duty foam infill. Ours is still going strong, been outside for 45 years, either full up with water on a trailer, or floating in the river over that period; all the wooden teak bits are shot but the hull is still in A1 condition.

    Guess about £250 for a 70's dell quay Dory. The old ones will probably be lying abandoned pulled up on the riverbank. Just up the river from my mooring in Ireland there are two abandoned dell quays.....ask the harbour master or river bailiff if they have seen any.

    ....or place a wanted add on the local sailing club board.

    Here's some cheap one's >http://www.ebay.co.uk/bhp/wilson-flyer
    http://www.ebay.co.uk/itm/Wilson-Flyer-17ft-6ins-on-trailer-/111319594645
    http://www.ebay.co.uk/itm/Dory-Fishing-Boat-/251497293075
    http://www.ebay.co.uk/itm/17ft-wilson-flyer-dory-fishing-boat-/251494465968
    http://www.ebay.co.uk/itm/148-White-Dory-/281299321516

    ....you get the idea!!!!!
     
  13. Ozparker72
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    Ozparker72 Junior Member

    Thanks thats helpful, at least I know what to look for.
    I will have a look over the next few weeks for a cheap one, at least it give me an alternative to building a new boat.

    It will cost me approx £850-900 to build Welsford's Trover. But it should last a few years.
    If I can pick up something like the boat you suggest cheaply, then that might get me out of a hole for the time being.

    thanks for the links rusty barge
     
  14. rustybarge
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    rustybarge Cheetah 25' Powercat.

    The design is surprisingly seaworthy. We used ours in the west of Ireland for sea angling, no problem going a couple of miles offshore, but the ride is very hard; ok in 2~3' seas, but check your fillings before you go out in anything rougher.
    20hp will only plane with two people onboard, you'll need at least 25hp for three passengers, and you may have to ask someone to sit in the bow to get it on the plane.
     

  15. Ozparker72
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    Ozparker72 Junior Member

    I have finally found a design that fits all my criteria for size, speed, stability, longevity and cost of build.

    The Lumber Yard Skiff , 16'

    I've been reading up in them, very quick to build and no epoxy needed.

    I'm ordering the plans today
     
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