Open 60 & 50 (IOMCA) rule should be changed

Discussion in 'Stability' started by Stephen Ditmore, Dec 25, 2006.

  1. BOATMIK
    Joined: Nov 2004
    Posts: 293
    Likes: 14, Points: 28, Legacy Rep: 190
    Location: Adelaide, South Australia

    BOATMIK Deeply flawed human being

    There is an Americas Cup Class thread on this forum where I go into this to more depth that is strictly necessary :)

    I think the interest in the AC has waned, largely because the tradition of innovation and ground breaking boats has gone from the game.

    Like I stated above - if the boats are fit for their purpose then open the rule up a bit to allow further innovation.

    Look at the America's cup.

    First lightweight hollow masts, the first light metal masts as we would understand them today, first winch systems, first effective trim tabs, the wing keel, outrageous ballast ratios, first crosscut sails, first rod rigging

    At times the innovations have meant that one of the boats has been completely outclassed.

    Perhaps one could argue that the match racing was relevant because it had the chance of equalising a speed advantage because of innovations.

    And that's how it should be! (IMHO)

    No probs with that at all.

    But the public interest is on the wane whereas boats that are more interesting in design terms and more open in rules have a good following.

    VO70s, Open 60s, the French Multihull scene.

    That's why I personally wouldn't like to see any further restrictions for the Open 60s etc.

    Phew - back on thread.

    MIK
     
  2. Vega
    Joined: Apr 2005
    Posts: 1,606
    Likes: 26, Points: 58, Legacy Rep: 132
    Location: Portugal

    Vega Senior Member

    Mik and all, I would like to point one of the most interesting points of the Open60 rule.

    Take a look at the constitution of the technical commission, take a look at how the rules are changed, who has the right to vote:

    Sailors, and only the ones that have raced Open60's. The technical commission has in it the best racers.
    I believe that in other expensive big boats ocean racing scenes, the power is more on the money, the owner's of the boats, Sponsors, big Sail clubs presidents and so on. The sailors are paid to race, not to say how the boats should be made.

    On the Open60's all the power is on the racers in what regards boat change. It is not amazing that they end up with seaworthy and fast boats. The contrary would seam quite improbable.
     
  3. sharpii2
    Joined: May 2004
    Posts: 1,875
    Likes: 87, Points: 48, Legacy Rep: 611
    Location: Michigan, USA

    sharpii2 Senior Member

    Wider or deeper, but not both

    I've got an idea.

    Why not make them trade Beam against Draft. The deeper your boat gets, the more narow it has to be.

    For example: What if the TOTAL of Draft and Beam could be no more than half the over all Length of the boat. Draft, of course, will include fully extended center boards and dagger boards as well as keels. And minimal freeboard will have to be a certain proportion of Beam, say 35%.

    I don't think you would see either wide, keel less boats, or narrow, deep splinter like hulls. I would imagine the Draft and Beam under this proposed rule would hover around equality. Say a Draft of 15 and a Beam of 15. Or close to that.

    Make it much wider and you will fail stability requirements.

    Make it much deeper and you will lose sail carrying power.

    Wider boats would probably end up being much heavier than narrow ones under this proposed rule as well. First, because there will have to be much more bulk (freeboard being 35% of Beam) and there would have to be more ballast (due to much less Draft and somewhat higher CA of the sails).

    A narrow boat would lose much more initial stability by cutting it's Beam than it would gain by increasing its Draft.

    I wouldn't be surprised, though, to see boats 10ft wide and twenty feet deep, as well as ones 20ft wide and 10ft deep.

    Bob
     
  4. bobothehobo
    Joined: Nov 2004
    Posts: 63
    Likes: 4, Points: 0, Legacy Rep: 47
    Location: Newport

    bobothehobo Junior Member

    I lean towards the view of keeping an Open Class as 'open' as possible however I also understand (I remember the 97-98 Vendee) the need to impose minimums on stability. What I would prefer would be to do away with the Static 20 degree rule while still maintaining the 127.5 AVS. I feel the 20 degree rule forces the designer to go wide (which may be beneficial for other reasons as well). With that rule in place you MUST go wide to generate enough initial stability, otherwise with a narrow boat and the limited keel cant angle, you could never have the Power (sail plan) to be competitive. Without this rule maybe someone could successfully attempt being competitive in the Vendee with a narrower boat. Maybe.

    I would like to see the basis of the IMOCA rule to be:

    60 feet long
    4.5 meter draft
    monohull
    Positive righting moment to 127.5 degrees
     
    1 person likes this.
  5. Man Overboard
    Joined: Oct 2006
    Posts: 246
    Likes: 13, Points: 0, Legacy Rep: 129
    Location: Wisconsin

    Man Overboard Tom Fugate

    I hope that this is not the end of this thread, as I think Stephen has raised an excellent question.

    Yachting World did a short interview with Juan Kouyoumdjian that expresses his views on the subject, an excerpt;
    YW,
    Am I correct to say that the race organizers and class authorities are responsible for the design rules and you design to the rules. If the rules need changing it's up to them?
    Juan,
    "That's exactly how it works. And because the advances on these designs put limits in a very grey area then the involvement of the crew and particularly the skipper on the decision-making or how much you push the design is fundamental."

    Source:
    http://www.ybw.com/auto/newsdesk/20051020140348ywvolvo06.html

    I have a question concerning rule D.2. Somewhere in this thread someone called it 20 degrees of heel; But D.2 states Amplitude from a vertical axis shall not exceed 20 degrees. Is that not 10 degrees of heel? If there is both canting keel and water ballast, than you have to take the worst case scenario between the two. This seems very restrictive for an open class, what is the rational behind this rule. What if a team(designer, sailor, sponsor) wants to limit beam and accepts 20 degrees, or even 30 degrees from movable ballast; what implications would this have in real world sailing? Let’s say for instance that you design for 15 degrees of heel due to canting keel, and 15 degrees of heel due to water ballast. Except for the fact that you can drive the boat harder and faster, I’m not certain it makes the boat less safe. In a worse case scenario, you could swing the keel the opposite direction to balance out the heeling force due to ballast. There seems to be little emphasis on the center of gravity which I would think should be addressed when scrutinizing the limits of safety of movable ballast.
     
  6. bobothehobo
    Joined: Nov 2004
    Posts: 63
    Likes: 4, Points: 0, Legacy Rep: 47
    Location: Newport

    bobothehobo Junior Member

    Man Overboard,

    The way they test the 20 degree rule (I have been a participant in one measurement and have observed 3) is with the boat at a dock the skipper puts all the movable ballast to one side (keel and any off centerline water ballast) and they measure the heel angle with an inclinometer on the transom (measurer in dinghy off transom, no one on board and boat in light ship displacement-most gear removed). Then the skipper gets back on board, moves all the ballast to the other side and the heel angle is again measured. The two angles are added together and cannot total more than 20 degrees. If they do, rubber stops are added to the keel to limit the cant to a point where total heel angle becomes 20 degrees or less. These stops are checked and photographed at the beginning and end of the race (as well as any stopovers).

    One of the rationales for the rule is to control the risk when the skipper is inadvertently caught with the ballast on the wrong side. You must remember these are long distance single handed races, most of the time the skipper is down below not at the helm. When, for example, the autopilot fails while surfing down a 20 foot wave and the skipper is below, the boat crash jibes and is knocked on her side with all the ballast now on the wrong side it becomes a very scary situation very fast. The further the keel is canted the worse the situation. The 20 degree rule is intended to somewhat control and or lessen this risk.

    Cheers,
    bobo

    Boat is placed head to wind, there must be minimal waves/wake, and minimal breeze. Basically, the inclinometer needs to be giving consistant readings.
     
    Last edited: Jan 14, 2007
    1 person likes this.
  7. sharpii2
    Joined: May 2004
    Posts: 1,875
    Likes: 87, Points: 48, Legacy Rep: 611
    Location: Michigan, USA

    sharpii2 Senior Member


    Good point, Bobo.

    But they should have anticipated that this rule would lead to wide boats AND shifting ballast.

    It would seem to me that if the limit was set at say 40 deg instead of twenty, the boat with the ballast on the wrong side would tend to round upr into the wind because of the changing shape of the under water hull.

    Maybe its time to put an absolute limit on Beam.

    I have thought of penalising it some other way, such as requiring the minimum freeboard being a certain percent of Beam. This would make beamy boats so high sided that it would wipe out much of the advantage of going super wide.

    Bob
     
  8. bobothehobo
    Joined: Nov 2004
    Posts: 63
    Likes: 4, Points: 0, Legacy Rep: 47
    Location: Newport

    bobothehobo Junior Member

    Bob,

    Agree that the shift to wide boats could have been anticipated and I think was at least by the skippers and the designers. The wide flat boats provide a lot of perks. Much better planing surfaces and the sooner (lower wind speed) you break away makes a huge difference. If you break away in 12kts of breeze vs. 12.5 it is huge in race which is dominated by offwind sailing. The wide flat surace also allows for much higher power (sail area) for a given displacement because a major portion of your stability is coming from beam, not righting moment due to a heavy bulb (very multihull like, no?). Also, with the wide flat boat wide on centerline water ballasts provide a unique advantage in that because the boat is flat they will have little to no effect on the heel in the 20 degree test. However, when sailing heeled 15 degrees the center of buoyancy shifts to leward and the centerline tanks now provide righting moment as they are windward of the CB. This is FREE righting moment (ie: not counted under rule). Again, allows for added power to the rig at very little weight gain.

    I think the wide, flat, fast boats are what the skippers, designers, and race organizers wanted and the IMOCA rule delivered just that. As with any rule type-forming you also get disadvantages. They pound like a beast to windward and can prove to be stable when inverted (again, multihull like).
     
  9. Man Overboard
    Joined: Oct 2006
    Posts: 246
    Likes: 13, Points: 0, Legacy Rep: 129
    Location: Wisconsin

    Man Overboard Tom Fugate

    Bobo
    Yes, in fact that is how it is described in the rule; that is, the heel angles are measured both to port and to starboard and totaled together. Then it is as I thought 10 degrees of heel. It is as you have stated more correctly called the 20 degree rule and should not be referred to as 20 degrees of heel.

    "I think the wide, flat, fast boats are what the skippers, designers, and race organizers wanted and the IMOCA rule delivered just that."

    I think you are right on this, radical, yet still have some measure of safety. When taken to the extreme (in beam), they do have multi hull like similarities, although they have to pass the 180 degree test. The 180 degree test seams to favor canting keel, as water ballast tanks are not permitted to be used to self righting. (There is a provision for this for fixed keel boats)
     
  10. bobothehobo
    Joined: Nov 2004
    Posts: 63
    Likes: 4, Points: 0, Legacy Rep: 47
    Location: Newport

    bobothehobo Junior Member

    Indeed, no canting keel Open 60 has yet failed the self righting test, if I recall correctly.

    The reason I refer to it as the 20 degree rule as opposed to 10 degress of heel is b/c the former is more correct. A boat that heeled 13 degrees to port and 7 degrees to starboard would be just as class legal as one that heeled 10/10.
     
  11. DGreenwood
    Joined: Aug 2004
    Posts: 714
    Likes: 34, Points: 28, Legacy Rep: 507
    Location: New York

    DGreenwood Senior Member

    With regard to the ten-degree rule, now that it’s tempered by the introduction of an ultimate stability factor in the shape of the 127.5 AVS limit I think it’s here to stay. It would be devastating to the old boats to change such a fundamental rule which is now working fine. Even though the boats pass the capsize test now you can’t get rid of the ten degree rule without replacing it with something (Volvo have a minimum beam stipulation) to ensure some measure of form stability in the hull. No, I think the ten-degree rule is here to stay.

    The fairly well informed words of Merfyn Owen.
     
  12. Man Overboard
    Joined: Oct 2006
    Posts: 246
    Likes: 13, Points: 0, Legacy Rep: 129
    Location: Wisconsin

    Man Overboard Tom Fugate

    yes, I wondered about that, although that would be a bit unorthodox. I find the open 60 class interesting, even though I am designing a blue water cruiser, because many of the rules are solid safety rules. I don't think to many cruisers would pass the strict open 60 safety requirements. I know that these are purely racers, but in many ways the new technology in sailing that the open 60's bring are more relevant than say, the Americas cup, at least for blue water cruisers expected to be single handed or handled by a couple. For example, there is not much data on movable ballast used in larger(over 30 ft) ocean going yachts; the open 60's are pushing the envelope here. More design data would be nice, that will trickle down in time.
     
    1 person likes this.
  13. DGreenwood
    Joined: Aug 2004
    Posts: 714
    Likes: 34, Points: 28, Legacy Rep: 507
    Location: New York

    DGreenwood Senior Member

    Two points:
    1)Stability without being penalized by weight makes for fast boats. That is what drives desire for width.

    2)The wide monos existed before the 20 degree rule and, if I am remembering correctly, the rule was a result of wide BOC boats having accidents they could not recover from. (water ballast)
     
  14. DGreenwood
    Joined: Aug 2004
    Posts: 714
    Likes: 34, Points: 28, Legacy Rep: 507
    Location: New York

    DGreenwood Senior Member

    Imagine a cruiser having to meet the boyancy rules for example (water tight bulkheads). That right there would make them way too expensive.
     

  15. Man Overboard
    Joined: Oct 2006
    Posts: 246
    Likes: 13, Points: 0, Legacy Rep: 129
    Location: Wisconsin

    Man Overboard Tom Fugate

    DG,
    In fact, our own Tim Troy had to pull out of the VELUX 5 because he did not meet the 127.5 AVS. You can read his statement here http://www.sailamericaone.org/americaone/tim_withdraws.htm
    I am not sure I understand why he didn't know that he would fail the test. Is it not possible to determine from the previous measurements? Why would he wait till the last minuet to do any testing on his own.
     
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.