Hull up offshore lifeboat project in front garden

Discussion in 'Boat Design' started by Trevor Richard Hunt, Feb 13, 2023.

  1. Trevor Richard Hunt
    Joined: Jul 2021
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    Location: POOLE

    Trevor Richard Hunt Junior Member

    Hi All,
    Just a few pic's of my 27ft alloy lifeboat project. TNLB Elsie May should have an LOA of 31ft when I fit the bowsprit to help increase the sail area. My design is based on a sort of modified version of the famous USCG 36500 series of offshore boats. The rig is in the back garden and consists of an A frame with a seat on the cross beam for a lookout. Square sail for downwind with twin forestays and backstays planned. 2 main watertight bulkheads, and should be unsinkable anyway, if the side lockers are stuffed with enough bags of pasta or noodles. Most of the topsides parts are from dumpster diving. Alloy hull and mostly wood topsides with alloy non slip or factory glass panels. Installation of a keel cooled Beta 30 in progress. Steel ballast beam and will coat the underwater hull section with epoxy glass layers to prevent leaks and electrolysis. Tiller steering.
    Long job !!
     

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  2. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    I would be rather dubious about this plan - I think that by doing this you might just compound any problems in the future.
    If there are any leaks, then the only proper solution is a welded repair.
    And re electrolysis, so long as you have good anodes correctly located, and you are very careful with your electrical installation, and you don't moor your boat in such a fashion that it can act as an anode for something else made of steel, then you should not have to worry about electrolysis.
    How old is the hull that you are re-fitting, and what thickness is the hull shell plating?
     
  3. Trevor Richard Hunt
    Joined: Jul 2021
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    Location: POOLE

    Trevor Richard Hunt Junior Member

    I'm copying what the RNLI do with their older alloy lifeboats, They have a heavily galvanised steel beam along the bottom, partly for ballast and partly for rock slides. There will also be 2 strengthening beams underwater, that will also act as rub rails when the boat is beached. All lifeboats should be beachable, and it helps a lot in terms of keeping the hull clean.

    There has been some alloy welding done already to the main beam which was damaged by electrolysis, but the rest of the hull is good, except that there is a risk of a leak through a rivet, and that is another reason to glass over the hull below the waterline.

    I will place an anode on the prop which will be painted with clear epoxy, (Probably West System), but apart from that the intention is to use 5 dangling anodes to cover for electrolysis that results from any damage to the glass coating. Hull anodes are a pain to change, but I could reach the prop with the boat in the water.
    The hull is 50 plus years old, as the offshore ships lifeboats were used from 1960 to 1968. After that they switched to cheaper glass. The plates are a bit thin, although I've not measured them excatly. All of them are in perfect condition, although a number show she has seen some action with assorted dents.

    If she survives the test program in the Portland race on RNLI training days, I plan to build a second version with a steel hull and similar topsides for a production model. Main market is offshore fishing, suveillance & rescue, plus private owners that want a safe sink resistant boat that is beachable.

    3ft 6in draught and just under 9ft beam. No idea what the final weight will be, but trying to keep it light enough to surf with a following sea. I try and follow the lifeboat design regulations, so dual start batteries not connected to the house batteries, other than an emergency cross feed switch. 2 fuel tanks with 2 primary fuel filters and a 5kW 48V DC motor on the same shaft as the Beta for slow trolling, canals or 3kts on a real sunny day. Although she will have a sailing rig, there is supposed to be an auxillary power system. Regen drive system for the batteries and might make 500W max in panels.
     
  4. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    So, then no more welding ever?
     
  5. Trevor Richard Hunt
    Joined: Jul 2021
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    Location: POOLE

    Trevor Richard Hunt Junior Member

    No more alloy welding. I've used high grade West System epoxy to repair aluminium defects before and it does work. It's also essential not to need a haul out, so it will list at around 30 degrees when beached, that allows the bottom to be cleaned or painted one side at a time. In reality the design should be just as good for fishing as it will be for on station rescue or surveillance operations. I might see if I can find a company to put my design into production, BUT with a steel hull, as an alloy one is too expensive. Unlikely as safety does not sell, just bling, bling sinkable designs with the right image.
    Aluminum Boat Repair Kit - with WEST SYSTEM G/flex Epoxy

    650-K Aluminum 4-panel.vp (westsystem.com)

    G/flex Epoxy - Wessex Resins & Adhesives
     
    Last edited: Feb 14, 2023
  6. Trevor Richard Hunt
    Joined: Jul 2021
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    Location: POOLE

    Trevor Richard Hunt Junior Member

    Started working on the A frame mast. The 20ft pole is a few feet too long to fit within a 4 foot bow sprits length that I'm planning to fit. I'm not going to buy another alloy pole for the loose footed square sail for some time, but I do want to raise the A frame to allow me to wind an HF long wire around one of the 2 backstays and down part of a forestay. Using low stretch halyard types lines for the twin forestays and backstays. Kenwood T-120S transceiver with an AT-120 AMU. I already have an HF twig fitted to the port stern quarter that feeds a Kenwood R-600 via a Sigma AMU. 2 way power switch to stop me frying the R-600 H receiver.
     

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  7. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    That pole looks rather skinny (re compressive strength) - are you going to have a horizontal spreader bar between the two legs of the 'A'?
    I presume that you will want to lower the A frame mast (forwards) - but if so, wouldn't the forward cabin get in the way if the hinge point is at deck level? The hinges would probably have to be positioned higher up than deck level.
     
  8. Trevor Richard Hunt
    Joined: Jul 2021
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    Location: POOLE

    Trevor Richard Hunt Junior Member

    The poles are thick walled alloy certified for use as scaffolding in the UK. You can buy them in most countries, although in far Eastern countries they use Bamboo for saffolding and that is nearly as tough. A frames have a cross bar normally in the middle, in in my design it will support a seat for a lookout. You will see a lot of A frames used by trawlers, although those are normally steel.
     
  9. Trevor Richard Hunt
    Joined: Jul 2021
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    Location: POOLE

    Trevor Richard Hunt Junior Member

    Anyone got a rough idea what a 27ft offshore lifting keel or mini gin palace has for total ballast weight. I can do the calculation for a canal boat, which will be used for the steel beam mass, BUT no idea of the difference. I will get a travel lift to visit me in the Davis Yard near Cobbs Quay marina in Poole, as I need to know the dry weight and use the old waterline for the displacement figures, then once a surveyor is found, do a full rail down tilt test during a lunch hour to figure out the internal and trim ballast. Bit of a pain to secure so it's not going to try and kill someone if the boat gets rolled. Target vanishing point will be the same as a steel Van Der Stadt 34 I fitted out in the Cannery Islands, or rather Gran Canaria where I used to skipper a commercial sport fishing boat or three. Billfish Fever 3 in fact. Lovely Chris Craft 46, a wood expoxy jobbie with 2 350hp Detroit diesels with very tune-full Garrret turbos.
     

  10. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Then you should not be "guessing" this then.
    You need to perform a proper weight and centres calculation and then investigate what range of stability she has and if it meets your target and if not, what mitigation is required.
    Stability should never be guessed when doing mods like this without hard data.
     
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