Weather helm on half tonner

Discussion in 'Sailboats' started by nemo, Oct 12, 2009.

  1. daiquiri
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    daiquiri Engineering and Design

    Hello,
    Don't want to enter the dispute between you guys, but Paul, what you just said sounds to me like a confirmation of G.H.'s and G.B.'s words about easing the main (up until pinching, but not up to luffing - that's useless drag) as a mean of preventing the weather helm. Or was it something else that you are disputing here? Sounds more to me like there is a missing episode in this movie....
     
  2. booster
    Joined: Apr 2009
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    booster Senior Member

    Regarding Wave-rider. At the World's in Australia (won by the Farr design Gunboat Rangiriri) the year before Poole Wave-rider had balance problems. Still it ended about 4th. Does Gary B. know what was modified to Wave-rider? So far the posts have been focused on the main. A common probelm is that one moves the traveller of the genoa backwards (or depower the barber-hauler). If one instead move it slightly forward and depower the sheet a little the lower part of the genoa gets fuller and the aerodynamic center moves forward and down. As a result the boat gets less weatherhelm ("lovgirig" in Swedish) and less heel. Note that the adjusments are small. By the way, in Swedish we have a word for the opposite to wheterhelm: "fallgirig". An translation could be: "nonwetherhelmgreedy".
    Regards,
    Booster
     
  3. Charly Setter
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    Charly Setter Junior Member

    In German it´s "luvgierig" and "leegierig" :)
     
  4. Paul B

    Paul B Previous Member

    Look who is talking. You posted NOTHING on this thread about the topic. You simply came here to try and start a fight. I guess you're still bitter that your nonsense in the past was pointed out for what it was.
     
  5. Paul B

    Paul B Previous Member

    In English, Lee helm.
     
  6. nemo
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    nemo Naval Architect

    Modifying the rudder sounds a good idea, although I have a large bustle fwd of the rudder, so I cannot balance the rudder without removing the bustle. But definitely I can increase the length. Did you keep the original maximum cord length or did you decrease that?
     
  7. nemo
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    nemo Naval Architect

    The design number of the boat is #65, same as Rangiriri mentioned above.
    I made some calculations on the original and actual theoretical centres of effort, and I agree that the mast movement didn't do a significant change, even though the foresail was slightly bigger in the original version.
     
  8. Paul B

    Paul B Previous Member

    Nope, not even close.

    The claim by GH was IOR boats had "buckets" of weather helm due to some design requirement in the rule, to the point that the boats needed to be reefed even in light air to make them balance, and that led to the demise of the rule. This is total nonsense.

    IOR boats had no more "buckets" of weather helm than any other tye of boat. All the competitive ones I sailed on and against were set up to sail with 3 to 5 degrees of helm, so the rudder was also providing lift along with the keel.


    In fact, most earlier IOR boats and even later masthead ones had less than optimal aspect ratio on the mainsail. So after their IOR days were over many had 10 to 20% of "E" added to the boom length, with no changes to the rig or keel position. Even this did not add the weather helm issues claimed by GH.

    Before the practice was outlawed by the rule we would fit hydraulic cylinders to the headstay and backstay, so we could rake the rig for the desired amount of helm. In light air we would rake back, as the breeze came on we would stand the rig up. After the practice was outlawed we would look at the weather report for the day and set the rig to what we thought the prevailing conditions would be. Even if we were caught out with our light air setting and the breeze built we still did not encounter "buckets" of helm as described.
     
  9. Paul B

    Paul B Previous Member

    Your rudder should have some counterbalance below the skeglet, if it is the original rudder for the boat.

    Increasing the span of the rudder would be good, since the rudders back in the old days were a bit stubby due to the available rudder stock materials. If you go with a carbon construction you should be able to have a much nicer rudder.
     
  10. Charly Setter
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    Charly Setter Junior Member

    There´s no need of a carbon rudder stock....

    Just take a 35mm stainless steel shaft, weld four strips of 30x4mm stainless steel to the shaft (2 on each side) and put a 35mm oak-plank between these strips on the front and the backside of the shaft. Cover the oak plank between the strips with 6 mm wood and give this design a hydrodynamic profile. You will get a rigid rudder design with good hydrodynamic properties and reduced drag, compared to the "light weigth" designs with large hollow shafts and acc. wide rudder profiles. The larger weighht of the shaft doesn´t matter as you need weight aft ;-).

    But never take plywood, this will break after some years (app. 5), the oak plank last 20+ years ;-).

    No, we didn´t change the chord length, there was no need. The "skeglet" is only a 50x30x300mm triangle shaped wood glued to the underside of the hull. It bears no load from the rudder bearings.
     
  11. Paul B

    Paul B Previous Member

    Hi Charley,

    I wasn't referring to your boat, but to Nemo's Farr.

    Using a rectangular carbon shaft would allow a thinner rudder profile than the original, thereby allowing a shorter top chord for the same % thickness. This is a good thing.

    The original rudder does have counterbalance (shown in detail below), but possibly could use more.

    In the end the original seemed to work pretty well for Gunboat, and 2269, at the '77 Worlds. So maybe no change should be made.

    Nemo, do you know why the rig was moved forward? Was it an attempt to get the rating back down to HT after the rule changes of '78?

    The attached photos are from the Bruce Farr Catalog of his Designs.
     

    Attached Files:

  12. Gary Baigent
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    Gary Baigent Senior Member

    Booster
    26. a class above
    IN EARLY 1977 Davidson designed a Half Ton yacht ********* that followed the theme established in Quarter Ton Fun. Farr, seeing his Half Ton Cotton Blossom outclassed by Whiting’s Newspaper Taxi, drew Gunboat Rangiriri – but Whiting and Ross decided to vacate the Half Ton series, sold Newspaper Taxi to Australia (where the new crew sunk it) and concentrated on the larger Smackwater Jack.
    Davidson’s approach with ********* was different to Farr and Whiting. Like Fun, all ballast was carried internally in lead bricks bolted to the floor like a chocolate bar but the major difference was his hull design which was narrower with less depth forward than the others. By having less beam Davidson believed his boats had less inclination to get out of balance during fresh sailing conditions and would not lift its stern or bury its bow when overpowered – which he felt was possible with the more asymmetric hull plan forms of Farr and Whiting. ********* looked small and narrow with low freeboard, shorter than Gunboat Rangiriri but had more sail. *********’s low hull made the coach roof appear prominent; it was there to satisfy the Rule’s high headroom requirement but in spite of this, ********* was a beautiful yacht and set an aesthetic standard and appearance that was to be emulated by a number of successful French designers. And like Fun, it was expertly built by John Rea in exceptionally light timber construction: two veneers that totaled 9mm over many stringers and frames. The stern was wide and low to provide power upwind and easy surfing downwind while topsides were slightly flared to get crew weight outboard. The deck was plywood on wooden beams and the rudder was fully retractable, like it was on Fun.
    Gunboat Rangiriri was similar to One Ton Red Lion but proportionately was beamier, heavier and carried more sail to be competitive in the light winds of Sydney. Ron Holland’s first daggerboard yacht, a tiger striped Silver Shamrock 111 skippered by Harold Cudmore, was similar to his fixed keelers – which turned out to be a disadvantage. *********, skippered by Tony Bouzaid with Helmer Pedersen alongside, was fastest, especially across and downwind – but in a long distance race the leaders, the Farr Swuzzlebubble and ********* fell into a hole; Gunboat Rangiriri (Peter Walker) won with a consistent 5,1,2,2,2 series.

    AFTER SYDNEY and new penalties ********* was prepared for 1978 by Davidson deepening the amidships area and fairing it out fore and aft. Bouzaid and Pedersen set up a new rig and sail combination and honed ********* before shipping to England. In a fleet of 50 yachts, 11 were centerboard designs but only three were considered in contention: ********* and two French designs, Anke from Michel Joubert and Jaunac by Jean Berret. Two British fixed keel boats were also considered but once racing began ********* was the fastest, upwind and down. While beating the main was sheeted down to leeward so the sail pumped. Although contrary to accepted sail trim, ********* was exceptionally fast in this mode, sailing freer than masthead designs but moving faster through the water which created lift for the daggerboard. The wind never rose above 12 knots, a strength some European journalists thought would lay the New Zealand boat on its side but in response Davidson growled, “If there had been a decent blow, ********* would have stamped even more her superiority over the fleet. Really the ORC has over-reacted to the results of the 1977-78 Southern Hemisphere results where centerboard boats cleaned up. But this was not the case at Poole where racing from a variety of designs was very close. There has been no conclusive evidence found that ultra-light will alter the trend of IOR racing – indeed at one stage the fixed keel Jones designed Indulgence looked certain to take the Half Ton Cup.”
    In spite of penalties being introduced to further slow the New Zealand lightweights, Davidson was in demand. The French were particularly impressed with ********* and picked up on the design continuing their own development so that later French designs gained a stranglehold on Cup Championships. US dinghy sailor John McClaurin wanted a flat hulled New Zealand daggerboard yacht and asked Davidson for a Three Quarter Ton version. The reply was Pendragon which naturally was a development of *********, again built lightly in wood by Tim Gurr and when it was finished in Auckland, shipped to the States. Pendragon won the Three Quarter Ton Cup held in the light airs of British Columbia, beating special designs from Chance, Holland and others in conditions the light boat was not expected to excel. Again the IOR was angered and unimpressed and the next list of penalties increased Pendragon’s rating by a full two feet - so much for Davidson’s attempt at diplomatic reality after winning the Half Ton Cup.
     
  13. Gary Baigent
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    Gary Baigent Senior Member

    Merde! ********* read Wave-rider.
     
  14. nemo
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    nemo Naval Architect

    I'm not sure that my rudder is exactly as shown in the picture. However, the skeglet wraps around the leading edge so maybe it just looks like the counterbalance is below it.. anyway I'll take some pictures in the weekend.
    What was the reason behind those skeglets anyway? Were they done in order to "cheat" IOR measurements?
    I believe increasing the aspect ratio would be good, even if maybe in light airs the boat would feel the additional drag caused by the increased area.
    Charly, have you got any feedback on this?
     

  15. Paul Kotzebue

    Paul Kotzebue Previous Member

    If memory serves, the idea was to have the AIGS station in the skeg and the AGS station aft of the skeg. The IOR included dimensions to establish whether or not the boat had a skeg. The net result was the boats had just enough skeg to qualify as one under the IOR.

    This is all from memory for what it's worth. My copy of the IOR rule is long gone and I haven't worked on an IOR design since 1984.
     
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