Trailerable, approx.26ft, aluminum sail/motorsail plans

Discussion in 'Metal Boat Building' started by MrNewman, May 24, 2021.

  1. MrNewman
    Joined: May 2021
    Posts: 6
    Likes: 1, Points: 3
    Location: non-US

    MrNewman Junior Member

    Hello,

    Who else, except Mr. Bruce Roberts, offers plans of trailerable or at least truck-transportsble sailboats - steel/alloy version
    ?

    I can find a lot of ply projects, so perhaps it would be ok to use them as a starting point (probably adding more longt. stringers, and replacing timber bars with alloy-extruded elements)?
     
  2. Alik
    Joined: Jul 2003
    Posts: 3,004
    Likes: 298, Points: 93, Legacy Rep: 1306
    Location: Thailand

    Alik Senior Member

    But why? In this size, You can buy a second-hand one for fraction of construction cost...
     
  3. bajansailor
    Joined: Oct 2007
    Posts: 2,043
    Likes: 672, Points: 113, Legacy Rep: 37
    Location: Barbados

    bajansailor Marine Surveyor

    Do any of the boats designed for plywood construction appeal to you such that you would like to build it if plans were available in aluminium?

    For a 26' vessel, if you have a couple of chines you should be able to have less stringers than a plywood boat, rather than more, depending on shell thickness and frame spacing.
    But as AliK mentions above, there are so many cheap second boats available everywhere now, buying one of these would be logical if your primary aim is to go sailing.
    But if you are more into the building experience than the sailing aspect, I can see why you want to build your own boat.
     
    Last edited: May 24, 2021
  4. MrNewman
    Joined: May 2021
    Posts: 6
    Likes: 1, Points: 3
    Location: non-US

    MrNewman Junior Member

    Mostly intersted in gaining experience, in many meanings.
    And yes, certainly, purchasing some 40yo rotten luxury is also a sort of experience...
    :)
     
  5. Milehog
    Joined: Aug 2006
    Posts: 423
    Likes: 38, Points: 28, Legacy Rep: 215
    Location: NW

    Milehog Clever Quip

  6. bajansailor
    Joined: Oct 2007
    Posts: 2,043
    Likes: 672, Points: 113, Legacy Rep: 37
    Location: Barbados

    bajansailor Marine Surveyor

  7. TANSL
    Joined: Sep 2011
    Posts: 6,626
    Likes: 446, Points: 93, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    It's not just about recalculating the scantlings. The structure should be redesigned, new construction solutions, very similar pieces but with slight variations that must be taken into account, redrawing of some parts, ... It is not easy to convert a plywood / wood structure into its aluminium equivalent. Not to mention the change in total displacement, which should be evaluated in all its aspects.
     
    bajansailor likes this.
  8. Skyak
    Joined: Jul 2012
    Posts: 1,219
    Likes: 37, Points: 48, Legacy Rep: 152
    Location: United States

    Skyak Senior Member

    There is a good reason that boat designs go to wood as they get smaller. As you scale down in metal you run out of stiffness because moment of inertia is thickness to the third power. To make a boat that doesn't oilcan and flex you would have to maintain thicker metal making an overweight boat. By going to formed, rounded shape you can get a little smaller before hitting problems but that is a huge amount of work just to get close to the performance of wood.
     
    ExileMoon likes this.
  9. ExileMoon
    Joined: Oct 2009
    Posts: 58
    Likes: 18, Points: 8, Legacy Rep: 45
    Location: Shanghai

    ExileMoon Junior Member

    Smaller boats use low-density materials, which helps maintain the rigidity of the boat plate. Another problem is corrosiveness. Metal ships will be reduced to a certain thickness due to corrosion every year. This value is constant and has nothing to do with the size of your ship. Obviously, larger ships have an advantage in dealing with corrosion because they have thicker plates.

    The 26-foot boat seems to rarely see metal plans. Maybe you can find some plans for aluminum, but there are very few steel ones. I checked another master, Dudley Dix, and his boat only had a metal structure over 30 feet.

    If you are determined to be a metal 26-foot boat, aluminum is recommended. If there is no suitable drawing, you can refer to Multi-chine's plywood ship drawing. The thickness of the aluminum sheet can be considered 1/3 the thickness of the plywood, and the minimum should not be less than 4mm. Add a proper longitudinal frame to the area of the flat plate with lower curvature to increase the rigidity of the aluminum plate, especially in the middle of the hull, because this area is the most stressed.
     
  10. MrNewman
    Joined: May 2021
    Posts: 6
    Likes: 1, Points: 3
    Location: non-US

    MrNewman Junior Member

    Let me clarify: I'm just not the biggest fan of plastics and phenols.
    That's now my plan: to get some single/multichine design (but not too 'multi') and then adjust it, to use 5 or 6mm alloy plates instead of 9-10mm ply.

    Why 'less multi'? Here must be a consensus on how the hull functions and the number of welded seams.

    As for design itself - main adjustment expected to be with frames/bulkheads: to cut additional nests for stringers, in order to add more support for alloy plates: approx 1,5" aside the seems, and [a few] in the middle of the plate.
     
    Last edited: May 29, 2021
  11. bajansailor
    Joined: Oct 2007
    Posts: 2,043
    Likes: 672, Points: 113, Legacy Rep: 37
    Location: Barbados

    bajansailor Marine Surveyor

    MrNewman likes this.
  12. Rumars
    Joined: Mar 2013
    Posts: 1,145
    Likes: 511, Points: 113, Legacy Rep: 39
    Location: Germany

    Rumars Senior Member

    Trailerable is very difficult, the boat must be under 3t for it. It's doable in Al, but not for all types of boat, and very hard in steel. Regardless of material this type of construction is very demanding due to the thin plates used (forget 5mm, think 3mm for Al, and 2,5mm for steel). You better be a professional metalworker if you want to attempt this.
    If trailerable means using a 7.5t truck, then the situation is different, there are some designs out there, and already buildt, all you have to is buy and refit to your liking.

    Example of trailerable Al boat: Speedlounger 8500 from FCY Design – Fast Cruising Yacht Design https://fcydesign.nl/ It's professionally buildt and expensive, needs a wide load permit or tilting trailer for towing. But you could commission a custom design from them.

    Example of steel sh boat: Wibo 820, 830, 835, Sneekermeer 800, etc. A not to bad example can be had for under 5000€ in northern Europe, the dutch buildt enough.

    Plenty of plans for amateurs, if you go to 30ft and not trailerable (truck only), for example Hermine 31 from Lucas Hermine 31' http://www.fr-lucas.com/hermine-31-1583 or Vita 30 from Van de Stadt Van de Stadt Design - Vita 30 https://www.stadtdesign.com/designs/stock_plans_sail/vita_30
     
    bajansailor and MrNewman like this.
  13. MrNewman
    Joined: May 2021
    Posts: 6
    Likes: 1, Points: 3
    Location: non-US

    MrNewman Junior Member

    True. That's why I will build a model first, to evaluate weight, mass center, perhaps visualize flow etc.
    And trailerability for me important not as for driving every weekend, but to relocate fast e.g. from Baltic to Ionic, or to move her to winter storage.

    @bajansailor thank you for a priceless hint - exactly what I was looking for. Just need to redraw it a bit, to reduce beam a little (-6..10cm), and think about keel mechanisation.
     
    bajansailor likes this.
  14. bajansailor
    Joined: Oct 2007
    Posts: 2,043
    Likes: 672, Points: 113, Legacy Rep: 37
    Location: Barbados

    bajansailor Marine Surveyor

    The Ovni 25 is good proof that a 25' aluminium sailing yacht can work well.
    Maybe you could modify the design a bit to have a vertical lifting keel?
    Or have a long shallow keel with a hinged centreboard in a trunk?
     

  15. Rumars
    Joined: Mar 2013
    Posts: 1,145
    Likes: 511, Points: 113, Legacy Rep: 39
    Location: Germany

    Rumars Senior Member

    Is building a requirement? If not, just buy an existing boat and modify to suit. First on my list would be a Sund 27. 2,5mm steel hull, can be made trailerable with a lightweight interior. Oversize permit up to 3m is cheap for winter storage, use a truck for long distance relocation. With a modern keel, rudder and sails it will outsail a lot of boats.
    Right now there are three on the market, ~10 000€ asking, ready to sail.

    If you want a modern swinging keel, look at how it was done on the Pogo's.
     
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.