Daggerboard versus keel fin on cruiser

Discussion in 'Multihulls' started by Mick@itc, Oct 6, 2011.

  1. cavalier mk2
    Joined: Mar 2010
    Posts: 2,123
    Likes: 55, Points: 48, Legacy Rep: 214
    Location: Pacific NW North America

    cavalier mk2 Senior Member

    Ballast Oldsailor, ballast.....The licensing only applies to combinations using their movable ballast the way I read things. It would be kind of hard to patent pre existing inventions in use for decades.
     
  2. oldsailor7
    Joined: May 2008
    Posts: 2,097
    Likes: 40, Points: 48, Legacy Rep: 436
    Location: Sydney Australia

    oldsailor7 Senior Member

    You are right Cav. But the US patents office took a lot of criticism for allowing that patent to be passed and the CBTF people have been very strict in enforcing it. You should see their schedule of fees. :eek: Ie:- Maximus had to pay $100,000.00
     
  3. cavalier mk2
    Joined: Mar 2010
    Posts: 2,123
    Likes: 55, Points: 48, Legacy Rep: 214
    Location: Pacific NW North America

    cavalier mk2 Senior Member

    Another reason to get the lead out...
     
  4. waikikin
    Joined: Jan 2006
    Posts: 2,381
    Likes: 150, Points: 73, Legacy Rep: 871
    Location: Australia

    waikikin Senior Member

    Probably small change in the style of boats its being used on............ not that I can afford it!

    Bit of uncoolness of vibe running on this thread apparently........... no need to get catty about it.

    All the best to all from Jeff.
     
  5. oldsailor7
    Joined: May 2008
    Posts: 2,097
    Likes: 40, Points: 48, Legacy Rep: 436
    Location: Sydney Australia

    oldsailor7 Senior Member

    At the risk of boring everybody I am going to tell you about my history of dealing with "Leeway reducers".
    I built my first boat, a pram dinghy, in the Northern winter of 1957. It had a daggerboard and I have resented the space they take ever since. After a bevy of sailboards (not windsurfers), I got a lot of experience in a Hurley "Silouette", an 18ft mono trailer sailer. It had two fixed bilge keels made of flat sheet metal.
    Being clueless at this time I didn't know any better and it sailed OK. It was never raced. After this I was lured to the dark side and built a Piver Nugget.
    The daggerboard case took up too much room in the hull and since I wanted a double berth there I thought I was really smart in putting two pivoting, surface piercing daggers at the outboard hinge points of the wing deck. I won't go into what bad news surface piercing boards are, but I soon found out.
    I subsequently fitted the Nugget with a Norm Cross LAR keel and it transformed the boat. It was faster, closer winded and, to use the overdone saying, it tacked like a dinghy. I also raced it, but that was a bit unfair because all the opposition at that time were monohulls and it cleaned their clocks. At that time my young teenage son had a girlfriend who lived on the other side of Lake Simcoe, so I quickly built him a Piver Frolic, which of course had a daggerboard. The hull was big enough between the crossarms for one person to sleep in, with a boom tent over, except the boardcase got in the way. So I ditched it and put in two fixed daggers on the inside of the outer sides of the floats. They extended down to the same level as the mainhull keel, and worked very well supporting the boat level on the beach as well as being leeway reducers. The Frolic was an amazing boat and my son sailed it in any weather and mostly at nightime, of course ;)
    (To be continued)
     
    1 person likes this.
  6. cavalier mk2
    Joined: Mar 2010
    Posts: 2,123
    Likes: 55, Points: 48, Legacy Rep: 214
    Location: Pacific NW North America

    cavalier mk2 Senior Member

    Uncoolness ? Time to lighten things up...

    So you want to build a boat and the bank wonders why?
    Stand straight and tall and look them in the eye.
    Does it have a keel,daggerboard, some other sort of fin?
    Will the GPS tell us where you've been?
    If the bank says "No we can't let you try."
    Smile and wink as you show a little thigh.
    Tell them a good multihull will surely never sink
    But if they say "No" you're stuck building a dink.
     
    1 person likes this.
  7. ancient kayaker
    Joined: Aug 2006
    Posts: 3,497
    Likes: 147, Points: 0, Legacy Rep: 2291
    Location: Alliston, Ontario, Canada

    ancient kayaker aka Terry Haines

    Interesting thread; I noted the earlier discussion on fitting flaps to keels to reduce leeway. An idea occurred to me:

    - since performance cats tend to sail with the windward hull out of the water much of the time daggerboards could have a little toe-in or even asymmetrical lifting profiles to minimize leeway. When sailing with both hulls wet the windward board would be raised to reduce drag.

    It seems simpler as well as more efficient than flaps. Has this been tried?
     
    Last edited: Oct 12, 2011
  8. Mick@itc
    Joined: Jan 2011
    Posts: 98
    Likes: 4, Points: 0, Legacy Rep: 49
    Location: Melbourne

    Mick@itc Junior Member

    Chris White's flap idea

    Was lucky enough to corrospond with Chris and he is currently working on this concept in an upcoming design. I will be keeping an eye on Chris's web site for when he announces the feature on a boat. So watch this space.

    Isn't it great that designers like Chris and Richard Wood (as examples) are generous enough to give their time and knowledge to us here on this and other boards.

    A big thumbs up to these guys.

    Mick
     
  9. oldsailor7
    Joined: May 2008
    Posts: 2,097
    Likes: 40, Points: 48, Legacy Rep: 436
    Location: Sydney Australia

    oldsailor7 Senior Member

    Yes this has been tried and can be successful if done properly.
    The early MacGregor 36 Cat had one board in one hull which was arranged so that it automatically rotated about 4deg on each tack. Since this cat was not normally sailed on one hull this arrangement worked just fine.
     
  10. oldsailor7
    Joined: May 2008
    Posts: 2,097
    Likes: 40, Points: 48, Legacy Rep: 436
    Location: Sydney Australia

    oldsailor7 Senior Member

    Leeway Reducers---continued.
    After a two year lapse due to job, home, family changes etc:I bult a Buccaneer 24 in a hurry. I had sailed to Bermuda on a Crowther Kraken 40 two years before and was expecing to do it again in a Buccaneer 33, however it didn't eventuate.
    I decided to build the B24, as the multihull Bermuda race was always won on Handicap by the smallest boat in the race. So I built this B24 with a non-ballasted fin keel, seeing as we would be sailing only in deep water. :rolleyes:
    Since water is 800 times heavier than air and incompressible I figured that any underwater foil could be considered as "Supersonic" at all but the very lowest speeds. So I chose a 6% symetrical supersonic airfoil section for the keel, with a plan form identical to the Concords wing and an area 4% of the working sail area. The rudder had a skeg in front with the bottom hinge on it and both conformed to the same plan form, but with a 12% symetrical section. I didn't have a motor for it at that time, so in its first race we had to sail to windward to the start line, and of course we were late for the start. It was a multihull race with ten boats in it, from 24' to 45'. We crossed the start line 200M behind the last boat on a windward/ leeward course, but ended up 1/2 mile ahead of the next boat at the finish. The fin keel was a success, ----BUT.
    We hadn't finished the boat in time to make the Bermuda race and the delicate fin keel was soon ruined on the concrete blocks littering the shores of Toronto harbour during the building of the outer harbours arms.
    So, the following season I replaced the keel with a vertical daggerboard, with an NACA 0008 section and a "No Nonsense" rectangular planform, with a wetted area equal to 2% of the projected sail area, (mainsail + fore triangle)-- and an AR of 2.5:1
    This was a little larger than the board in the B24 plans and helped make the boat very close winded
    The original rudder was maintained as it was perfectly satisfactory.
    The B24 was sailed happily for another season and then sold pending the building of the Buccaneer 28.

    Ah!! The Buccaneer 28, the last boat which I built for myself.
    It had a pivotting centreboard built strictly to the plans.
    Fully retracted it had a neoprene seal on the bottom and the box was totally sealed. The fully floating pivot pin was set in solid epoxy both in the case sides and the CB, with SS rubber sealed plates on either side of the case.
    The case top was removable, being screwed down on rubber seals in case of needing access to the board---which we never did. The semi-circular head of the board had two braided lines epoxied in at 180 deg to each other. These led forward to a double pulley, up a pvc tube to the cabin top, thru another double block,over the cabin top to a double plastic jam cleat at the cockpit.
    Control of the CB was thus easily and conveniently done from the cockpit.
    The only time we ever went aground the lines pulled out of the plastic jam cleats and the board retracted without damage. Nobody can tell me that a fully pivotting centreboard is not a good idea.
    Now --how about LAR keels. (to be continued).
     
    Last edited: Oct 16, 2011
    1 person likes this.
  11. cavalier mk2
    Joined: Mar 2010
    Posts: 2,123
    Likes: 55, Points: 48, Legacy Rep: 214
    Location: Pacific NW North America

    cavalier mk2 Senior Member

    An interesting history and a nod that done correctly many options can get the job done. In many cases identifying the usage determine what trade offs to make. I like the SST fin idea, air at those speeds has to seem solid like water. It would be interesting to see a study on high speed air sections applied to the water.
     
  12. oldsailor7
    Joined: May 2008
    Posts: 2,097
    Likes: 40, Points: 48, Legacy Rep: 436
    Location: Sydney Australia

    oldsailor7 Senior Member

    Leeway Reducers (continued).

    As mentioned earlier, the Piver Frolic and my Nugget had LAR keels.
    It wasn't until I was living in Victoria, sailing monos at the Sandringham yacht club on Wednesday afternoons and mullties at Warneet on the weekends, that I had the best of both worlds.
    I had a half share in a fibreglass Crowther International 23. It had an LAR keel cunningly fashioned into the bottom of the hulls. Basically round bilge hulls with fin keels smoothly moulded in.
    With Ian Johnston and Garth Morrison crewing it we won the 1979 "Round French Island" trailer sailer race.
    The race is in a clockwise direction around the Island starting at the turn of high tide on the West side. The tides are high and the level falls rapidly after change of tide. The East side of the island is mud flats which dry out at low tide. All of the boats give this area a wide berth going round. We were moving quickly and took a chance, scooting across the shallow water with our small draft. One of the trailer sailors saw us doing this and followed us over.
    Half way he grounded and the falling tide soon had him marooned on his beam ends until the next high tide could float him off. Here is a pic of us in that race. (coming shortly).
    The lesson learned is :- Horses for courses. LAR keels are a viable choice for cruising boats where the advantages can out weigh the disadvantages.
    LAR keels for racing are almost always outweighed by well designed Daggerboards. Pivotting centreboards are somewhere in between. Just MHO.
    When we moved from Melbourne to Sydney "Silent Runner" was sold to a chap in the Hindmash Island yacht club, SA. He fitted it with a prodder and a huge assymetric and still successfully races it I understand..LAR keel and all.
     
    Last edited: Oct 20, 2011
    1 person likes this.
  13. oldsailor7
    Joined: May 2008
    Posts: 2,097
    Likes: 40, Points: 48, Legacy Rep: 436
    Location: Sydney Australia

    oldsailor7 Senior Member

    Please see attached photo as promised!
     

    Attached Files:

  14. Alan.M
    Joined: Sep 2005
    Posts: 37
    Likes: 2, Points: 0, Legacy Rep: 27
    Location: Australia

    Alan.M Junior Member

    If you're going to have saildrives, I would go with LAR keels, at least deep enough to protect the saildrive legs. Saildrive legs are too expensive and delicate to have hanging down unprotected.

    You'll lose some performance though.
     

  15. michael pierzga
    Joined: Dec 2008
    Posts: 4,862
    Likes: 115, Points: 0, Legacy Rep: 1180
    Location: spain

    michael pierzga Senior Member

    As Oldsailor has pointed out...you must decide between Racer and cruiser. Performance wise, My experience says that an oceanic cruiser is optimised for reaching, a coastal cruiser is optimised for windward work. Daggerboards are not needed for an oceanic cruiser.
     
Loading...
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.