Trad vs Mod - Yet Another

Discussion in 'Boat Design' started by Capt Ronrico, Nov 3, 2015.

  1. Steve W
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    Steve W Senior Member

    I don't know how you would think the Tahiti ketch does not have a deep forefoot, it does. A local guy built I know built a beautiful example of the Tahiti ketch back in the 70s with the idea of taking the family cruising, which he did sailing out of the great lakes and eventually ending up in Florida where they sold the boat as apparently it hobby horsed unmercifully and was not what they wanted to cruise in. He has since built many superbly crafted boats including several trimarans, I think all have been light displacement with rudders. I have not discussed his choices with him so draw no conclusions.
     
  2. FAST FRED
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    FAST FRED Senior Member

    Sandbaggers weren't really narrow (although some other 19th-century racers were).

    Sandbaggers were beamy when FLAT on the water, when sailed they rolled up on the hull presenting a canoe shape to the water.

    Think of them as single hulled cats while underway. with only a long skinny surface in the water .

    That was the reason for their speed. 10 or 12-1 LB ratio when at speed.
     
  3. CT249
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    CT249 Senior Member

    Can't see a 10-1 L/B ratio here;

    [​IMG]

    and can't see how this shape would ever get to a L/B ratio higher than than of an international Canoe or Moth.
    [​IMG]

    All the pics of heeled sandbaggers show them with at least the centreline immersed, which gives them about 5:1 length to beam ratio. The old sketches seem to show them sailed even flatter.

    The closest hull shape still being raced is the Sydney Harbour Historical 18s, including some which have a similar L/B ratio, and they don't come close to a 10/1 heeled L/B ratio, and they are not at their fastest when heeled.

    [​IMG]
     

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  4. FAST FRED
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    Rolling the boat up and out of the water to go faster is a common concept on todays racers.

    My point is this racing concept would suck on a cruising or voyaging boat.
     
  5. sharpii2
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    sharpii2 Senior Member

    IIRC, a Tahiti ketch has a level, long keel, which fairs into a skeg and cutwater. This was to limit draft as much as possible without going for some sort of 'board.

    Full keel boats often had considerable aft, down slope to their keel bottom edge. This did two things:

    1.) it moved the latteral area aft somewhat, and
    2.) it allowed for a deeper, more powerful rudder.

    Both would be quite helpful in quartering seas.

    My guess as to why early fin keel, separate rudder sailboats may have been slow is because they probably didn't get the balance right (center of effort of sails too far fore or aft) and the rudders may have been of poor shape and insuffiient area.

    As noted in numerous threads by numerous poster, a big, efficient rudder can cure a lot of ills.
     
  6. Capt Ronrico
    Joined: Oct 2015
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    Capt Ronrico Junior Member

    bpw:
    Your post is very thought-provoking. I read it with great interest, especially since you introduce something new into this thread. Every previous defence of this hull type has centered on speed and agility, so I appreciate your comments.

    If I understand you correctly, you are saying that a discontinuous keel provides a sort of safety margin with respect to a following sea striking the vessel at an angle. That is, a continuous keel towards the rudder provides purchase aft for such a sea to turn the boat broadside to the wave, a broach. A discontinuous keel - separation of keel and rudder - provides less purchase to a skewed, following sea.

    But to play devil's advocate... wouldn't this be most important to a vessel with a cutaway forefoot? A moderate forefoot would provide some purchase forward to counteract the turning effect of a keel continuous-aft, to some extent, would it not?

    If so, does it not follow then, that a boat with both a continuous keel aft and a cutaway forefoot would be a very questionable choice? I shall try to attach a pic to illustrate hull designs that might be deprecated under this rule.

    They are, top-to-bottom (or truck-to-keel, as we nautical persons say) the Alberg 30, Cape Dory 36, and Hans Cnristian 33T.

    To the best of my knowledge, there is no hue and cry about these boats being particularly prone to broaching. Indeed, they seem to have a good reputation, and large following. Even the tiny Alberg 30 has made a number of circumnavigations. ( I cannot imagine circumnavigating in a 30-footer - no matter how big! ) Granted, they do not have ZERO forefoot, but they have a modest forefoot and continuous keel. They have not only a continuous keel, but also a deep-keel.

    Back to you.
     

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  7. CT249
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    CT249 Senior Member

    Doesn't a deep forefoot move the centre of lateral resistance forward, all else being equal, and therefore make a boat less likely to track well?

    Look at other devices - aircraft, surfboards, arrows, water skis. They all have the centre of lateral resistance well aft. As the late and great Australian yacht designer Joe Adams once noted, arrows don't have feathers all the way along their length.

    We can try this pretty easily in a small rowing dinghy. Move to the front of the boat, to give it a deep forefoot with the CLR well forward, and it develops a strong turning motion and does not want to track straight.

    If I recall correctly, the idea of the deep forefoot in Colin Archer designs and similar types was to allow a boat to lie ahull or heave to well, not to run before the seas well. As noted earlier, many other traditional long keel boats normally had a lot of "drag" (ie the aft end of the keel was much shallower than the front) and therefore although their keels were long, their forefoot was significantly shallower than their aft sections.
     
  8. bpw
    Joined: May 2012
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    bpw Senior Member

    It isn't so much that the full keel boat gets turned more easily by the wave as that it is much harder to get the full keel boat back on course.

    I think people put way to much emphasis on the idea of full keel boats holding a course well. In any sort of seaway it doesn't matter what kind of boat you have, you will be getting pushed around. When that happen the priority becomes getting back on course quickly and with minimal load on the steering gear.

    You may not be hearing a hue and cry, but that has more to do with most any boat being good enough for the average cruiser or circumnavigation. It's interesting that when we were down in Chile and surrounded by folks with lots of high-latitude, bad weather experience just about the only people with full keel boats where those who couldn't afford anything else. All the purpose-built southern ocean boats had fin keels or centerboards.

    Our slow, full keel boat put us at a significant disadvantage when it came to weather routing and picking good weather windows. We also ran out of options a lot quicker in bad weather since we could not fight up wind like a modern boat could. We did fine, but I am pretty sure we took more risks in our boat than if we had been in something faster and more modern. Our new boat has a fin keel.
     
  9. Capt Ronrico
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    Capt Ronrico Junior Member

    Mason 31

    MASON 31
    Not so much off topic as tangential to it, my latest obsession is the Mason 31 (pictured, I hope).
    I'm sure the spade-and-blade Mods will howl over it, but I like it, fool that I am.
    Can't find info about the Mason 31 - does anyone have knowledge or illustrations of it?
    And - is there any general source for Al Mason's designs? It would be a shame if his work was lost.

    Speaking of Al Mason - at one time, there was a sort of fashion for a piratical-looking craft with the unfortunate name of Cogge ketch. I know "TAD" was involved in one - the "Blackfish", I think.
    My question is - Is it true that there were 3 designs for it - the Urry brothers, Mason, and Garden?

    Thanks,
    Commodore Ronrico
     

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  10. PAR
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    PAR Yacht Designer/Builder

    Mason worked for S&S for a long time and did plenty of independant design work too. I'm not aware of the Mason 31, but he's given credit for designing "Finisterre" at S&S in the mid 1950's, which really changed the CCA and cruising yachts around the world. He died in the mid 90's I think and has many designs to his well crafted eye. I think his daughter is working on a book about her father's thoughts on the ideal cruiser. She's stopped in here a few times, if memory serves me correctly, but it has been years since I heard anything about Anita's efforts. I hope she's okay and in good health.
     
  11. Capt Ronrico
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    Capt Ronrico Junior Member

    MASON Intrepid 31

    Thanks PAR. I found out that the correct name for the Mason 31 is the Mason Intrepid. Designed in 1946 for steel, wood or aluminum. Featured in the Rudder magazine Jan, Feb, Mar 1946. Trying to find copies. Turns out there's a blog on the web, for the Eleanor Tarr.
    And no sign of Anita Mason. Last trace of her was a few years ago.
    - Admiral Ronrico, KCGP
     
  12. gonzo
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    gonzo Senior Member

  13. Capt Ronrico
    Joined: Oct 2015
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    Capt Ronrico Junior Member

    Southern Ocean and Rudder magazines

    bpw -
    I enjoyed hearing from someone who has time in the Southern Ocean. By sheer coincidence I am reading "To the Great Southern Ocean" now. Be nice to hear more.
    But I have to ask - You introduce the subject of centerboarders. I recall a couple who sailed the ice in a purpose-built steel-hulled boat. It was a centerboarder - with ice-breaking capability. They would yank the board, start the engine and run the boat up on top of the ice thus fracturing it. That's a basic technique of the naval ice breakers.
    So my question, at last, is: were the boats you encountered built as centerboarders for ice-breaking purposes?

    gonzo -
    yes, that's the link. Couple of nice Intrepid drawings. Mystic Seaport has the Rudder articles. Attached is an Intrepid in green with wooden coach. Pretty boat.
     
  14. Capt Ronrico
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    Capt Ronrico Junior Member

    2nd attempt

    try try again
     

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  15. Geno
    Joined: Jul 2017
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    Location: Portland OR

    Geno New Member

    I have a 1972 Mason 31 sloop in Portland OR. I have pictures but not sure how to upload them as I am new to this site...but if you're interested in what she looks like let me know Capt Ronco I can email them too you.
     

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