Larger Steel version of PARADOX

Discussion in 'Metal Boat Building' started by ImaginaryNumber, Oct 6, 2015.

  1. SukiSolo
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    SukiSolo Senior Member

    Not sure about bow centreboards. They work for lateral resistance but make the boat hard to steer as you have the rudder at the stern, so the 'pivot' is a long way forward. Also on faster planing craft, just for fun I know that the steering reverses ie you have extreme opposite to usual rudder movements to make to keep the boat tracking....;)

    I believe this is because you start to lose the centreboard as partly it is out of the water, and works in combination with steering around the new 'pivot' point, which is dramatically different lengthwise and of course it can skid sideways more. Might not matter so much on pure displacement craft though. Tacking is definitely slow so not a match racing ideal...;)
    In pure straight line it does work OK, check also Bill Koch's America 3 hull some years back which tried it on an Americas Cup challenger prospect.
     
  2. Angélique
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    Angélique aka Angel (only by name)

    Two chines per side, the mid section is flat and on a flat surface she's able to stand firmly without the aid of any supporting devices, draft is 0.85 m (2' 9 1/2 ") with the board up, and 1.70 m (5' 6 15/16 ") with the board down.

    -- Link -- Link -- Link --
    P.S. - The flat bottom is extra thick for ballast reasons.
     
  3. Angélique
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    Angélique aka Angel (only by name)

    Note: the Skoit is able to make safe offshore passages in reasonable weather windows, but she's not an all oceans all weather boat.
     
    Last edited: Oct 13, 2015
  4. Angélique
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    Angélique aka Angel (only by name)

    For comparing the minimum size for plywood replacement by steel here another style light shallow boat, the Parker Sea Bright series, for the 33' Parker says ‘‘construction: marine plywood’’, for the 36' he says ‘‘construction: marine plywood, steel or aluminum’’.

    Reuel Parker - - - Sea Bright 33: Link -- Link - - - Sea Bright 36: Link -- Link

    In the below quote the Sea Bright 36 of which Reuel Parker says ‘‘Ocean Voyaging Cruiser’’
    Here's a thread on the Wooden Boat Forum about the Parker Sea Bright 33 where you can see they are lapstrake or multi chine with a flat bottom / box keel on which they can stand upright like the Lunstroo Skoit . . .

     
  5. Angélique
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    Angélique aka Angel (only by name)

    Here's a trick how Grahame Shannon saved weight on his 23' 10" (7.26 m) steel Tom Thumb design . . . .

    Blue Water Boats ---> List ---> Tom Thumb 24
    For a steel Hogfish Maximus style boat I would add to the above weight saving measures a plywood deck on laminated beams.
     
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  6. ImaginaryNumber
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    ImaginaryNumber Imaginary Member

    Angelique, you're the Queen of Internet research. Thanks for your helpful posts. [​IMG]

    Why is Skoit not an all oceans all weather boat? Maybe it can't recover from a knockdown or capsize?

    The narrow keel of the Skoit causes the boat to tip slightly when grounded. I prefer the wider keel shoe that Sea Bright has, which is able to keep the boat upright. Of course, the flat-bottomed sharpie is even more stable when dried out.

    I am attracted to the much more square interior shape of a sharpie, compared to curved bilges and pronounced deadrise of many traditional designs. Seems much easier to fit out the accommodations in a sharpie.

    In the Woodenboat discussion you referenced some were advocating tandem centerboards/daggerboards as a way to avoid having the case in the middle of the accommodations. They also said that by differentially raising or lowering the two centerboards you could get the boat to sail balanced on any course. Maybe Matt Layden was thinking about this when he designed LITTLE CRUISER to have a bow centerboard and a large rudder. Does anyone have experience with tandem centerboards? Is the hassle of having to maintain two centerboards worth the sailing and accommodation benefits?

    It's helpful to see where different designers felt they could they could transition from wood designs to steel designs. I want to learn more about the construction details of Shannon's TOM THUMB. It may offer good ideas transferable to a small steel sharpie. What problems can be expected when joining metal to wood? Is their difference in thermal expansion a problem? Thanks again for posting this information.

    One of my ideas is to use a thick (1"-2") flat steel plate, the width of the hull, as the base and 'strongback' for a sharpie. The plate might be stiff enough to need little framing, would be gauged to provide the needed ballast, and would provide huge protection if a reef happened to pop up in a location not previously noted by the chartmakers. :(
     
  7. Angélique
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    Angélique aka Angel (only by name)

    This Dutch magazine article has a stability curve of the Skoit, she recovers from over 130° knockdown in flat water without taking into account the external forces that brought her in this position in the first place, so when this happens in a gale with 10 m plus waves than before recovering she could get knocked further by a wave hitting her exposed bottom and so turning her complete upside down. Once 180° inverted she has quite a bit upside down stability and has to pass that 165° point far below the dotted horizontal neutral line again, while the keel-less bottom offers only low impact height and little grip for waves to knock her back over that 165° point, while the rig in the water damps the motions to get her there. So in those conditions she might stay upside down in the middle of an ocean. This doesn't come from this article that I read many years ago and didn't reread now, but it's my personal impression of the shown stability curve.

    The stability curve of the Paradox looks much better to me....

    P.S. - Here's an magazine article in English about the Skoit.
     
  8. Angélique
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    Angélique aka Angel (only by name)

    Hundreds of Shannon's Tom Thumb 24 were built over the last three decades (300+ sets of plans were sold in the first year alone) and I didn't came across any reported problems in this respect.

    Research for joining wood to metal also the Composite Ships, which were built the other way around, wooden planking over a wrought iron frame, and were the final stage in the evolution of the fast commercial sailing ships, this composite construction was also used for some steamships.

    Some composite built examples: Cutty Sark -- HMS Gannet -- City of Adelaide -- Ambassador -- PS Oscar W

    City of Adelaide ---> Construction
     
  9. Angélique
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    Angélique aka Angel (only by name)

  10. ImaginaryNumber
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    ImaginaryNumber Imaginary Member

    Thanks for all your research, Angelique. There's no mention on the Tom Thumb web page if both the hull and deck are steel, or if only the hull is steel but the deck is wood or fiberglass? It is the watertightness of a metal hull to wood deck that I was wondering about.

    If I understand this table of coefficients of linear thermal expansion correctly I see that steel has a coefficient of 6.7x10-6 inch per inch per degree F, while 'wood' (not pine or fir) along the grain is 1.7x10-6, yielding a difference of 5.0x10-6. For a boat 30 feet long (360 inches), and a temperature difference of 80oF between summer and winter, this gives a difference of expansion of .144 inches between the wood and steel (if I did the arithmetic correctly). If the amidships section of the joint is fixed, then the joint at the bow and stern would each have half that slippage, or .072" (~1/16" or 1.8mm). So whatever sealant one uses between the steel hull and the wood deck might need to be able to move this amount and still remain watertight. Are there fastening systems and sealants which can tolerate that sort of movement?

    Wandering through some of the links you provided got me to a page on the history of copper sheathing. Interesting how wood ships, even with the added weight of the copper, were much faster than unsheathed boats because they were more streamlined, and because they had less fouling. But they struggled for quite a while to get iron hulls and copper sheathing to play well with each other. Even iron spikes in wood planking didn't fair well when the hull was sheathed in copper, so they eventually started using copper-based spikes.

    And I found this incident amusing:
    Starting at 1:18...FINALLY!
     
  11. Angélique
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    Angélique aka Angel (only by name)

    Here's the steel Alcyone, a multi chine flat bottomed centerboarder with a liftable rudder installation, designed by Max Max Guning, and built in many versions.

    The original Alcyone I has a flush deck and an aft cockpit. The original Alcyone II has a flush deck and a center cockpit and a high aft cabin.

    Check the Alcyone archives for info, they're wide and deep . . :idea: - Dimensions - Drawings - Brochures - Articles - Pictures - Etc... - Etc... - Etc...
    Note: the ‘‘Cormorant’’ type in those archives is a more traditional Dutch flat bottomed yacht of the ‘‘Zeegrundel’’ type, but with the leeboards replaced by a centerboard, and is a boat for use on kinda protected waters.

    Gunning-yachts.jpg
    click pic to enlarge

    Below the Alcyone I, L 10.50 m x B 3.09 m x D 0.80 / 1.75 m, weight 8.10 tonnes (metric) and 49.20 m² sail.
    Valentijn-Alcyone.jpg - - Valentijn-Alcyone_open.jpg - - slide10.jpg
    click pics to enlarge

    Unfortunately, like the Lunstroo Skoit, Alcyones have a off center companionway and to make this worse many have washboard vents in in the doors. Never the less some Alcyones have traveled all over the world. This PDF of a 1959 magazine article in Dutch about the Alcyone II shows a Alcyone I visiting Zanzibar.

    Below an Alcyone I that looks pretty original... (pic source)
    zomer2006-7.jpg
    click pic to enlarge
     
  12. Angélique
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    Angélique aka Angel (only by name)

    The below attached Cormorant brochures don't agree with the restricted use in my note, however the brochure in English does explain the above quoted mistake with the imperial units, it should be the below the brochure says, the same kind of mistake could apply for the other imperial units in the Alcyone archives.

    click pics to enlarge
    vs_pro_corm2_engger.jpg - - vs_pro_corm1_A_nl.jpg - - vs_pro_corm1_B_nl.jpg
    Cormorant brochures: the first one is in German and English, the next two is one brochure in Dutch.​

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    Below some Alcyone brochures....

    click pics to enlarge
    vs_pro_alci_A_nl.jpg - - vs_pro_alci_B_nl.jpg
    Alcyone I brochure in Dutch.​

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    click pics to enlarge
    vs_pro_alcii_A_eng.jpg - - vs_pro_alcii_B_eng.jpg
    Alcyone II brochure in English.​
     
  13. Angélique
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    Angélique aka Angel (only by name)

    -
    Below not a sharpie, but just saw a Martin Bekebrede Yacht Design one off Mytilus for sale here, maybe some more ads show up from this link.

    From the pics and specs she looks like a serious ocean going shoal draft steel boat in good nick to me.

    Don't know if she's shallow enough for you, but sure you can't build anything reasonable of that size in steel for that asking price, which might drop in the time to come . . :idea:

    And since she looks like ocean going, you could sail her home . . ? ?

    But on the sailing pictures she has only her main and yankee aloft, I wonder why . . :confused:

    - Designer: MBYD = Martin Bekebrede Yacht Design (Note: MBYD has a good reputation!)
    - One off design type: Mytilus
    - Builder: ? ?
    - Hull + superstructure: Steel
    - Dimensions: L 12.5 m (incl. bowsprit 13 m) x B 3.98 m x D 1.15 m / ca. 2.75 m (D centerboard up / down)
    - Fully rigged + fully tanked empty ship weight: ? ?
    - Max displacement: ? ?
    - Stability curve: ? ?

    Note:
    - The links in the first line are in Dutch.
    - The hotlinked quoted pics will disappear when the sources go offline...
    - Unless someone makes attachments of them.
    - I wonder what happened to the forum's feature to upload pics from an URL* . . :confused: - (since I'm not behind my own computer right now and can't download + upload from here)

    P.S. - * Got an adequate answer from the Moderator. Thanks Mod [​IMG]
     
  14. Angélique
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    Angélique aka Angel (only by name)

    -
    Grahame Shannon's Tom Thumb 24 has a steel hull + a steel deck + steel cabin sides + a steel cabin roof.

    But there are other designs with: - [​IMG] - - [​IMG] - - [​IMG]

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    [​IMG] a steel hull + a steel deck1 + steel cabin sides + a plywood cabin roof on wooden* beams.

    An example of this is the original Wylo II scroll down as designed by Nick Skeates.

    1 I'm not fully sure about the deck of Nick's own Wylo II, it could be wood like the cabin roof.

    We talked a bit about the Whylo II in the thread Cruising sailboats with no or minimal cockpit in the 30-40 ft range, from post #13 to #27, and later maybe even further ?

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    [​IMG] a steel hull + a steel deck + plywood cabin sides + a plywood cabin roof on wooden* beams.

    An example of this is the original Nienke II Dutch as designed by Evert de Boer from Delfzijl in the north of the Netherlands.

    She has double off center boards in her 0.8 m wide box keel, on which she's able to dry out.

    PDF's: Original Nienke II Dutch - - Full steel Nienke II Dutch

    The latter is heavier on top and so has a higher center of gravity and consequently a lesser stability.

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    [​IMG] a steel hull + a plywood deck on wooden* beams + plywood cabin sides + a plywood cabin roof on wooden* beams.

    See for an example of this: George Buehler Yacht Design ---> 70’ 8” WUNDERBURG (a “kayak” yacht!)

    Here some tips and tricks how it's done: George Buehler Random Thoughts ---> Wood Decks on Steel Hulls

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    * Prefered is laminated beams, especially when curved.
     
    Last edited: Nov 26, 2016

  15. Sailor Alan
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    Sailor Alan Senior Member

    I have some experience with tandem 'Dagger Boards' and Thor Hyerdal also used them successfully on the balsa raft to control direction in the trades quite well. Yes, indeed you can control direction using the dagger boards deferentially. Any way you can spread the rig, or lateral resistance, along the boat helps both directional stability and the ability to control direction. It's why I now favor double mast rigs for cruising, having had my fill of racing (though I still race every second weekend all year) on single stick rigs.

    I also used a thick steel plate as a bottom/ballast in the distant past. I wrote about it in this forum I think. Attaching ply to steel, you need many small fastenings, I use 1/4" or 3/8" at 4" centers, though I always try to have a thin steel flange for the actual interface to the plywood. I used liberal amounts of tar in my joint, messy and cheap then, probably illegal now. I 'galvanized' the steel using hot caustic soda (I think), and Zink.
     
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