Improving IOR Stability?

Discussion in 'Sailboats' started by jakmang, Mar 6, 2013.

  1. Paul B

    Paul B Previous Member

    Not correct. Modern boats with wider sterns (TP 52s, IMS designs, IRC desings, HPR designs, etc) are much faster upwind than the old IOR types of a similar size (or even a similar waterline length). They are much more powerful, and closer winded.
     
  2. Paul B

    Paul B Previous Member

    Interesting way of looking at the issue. I do think you have overstated the effect of bow down trim on CLR.
     
  3. sean9c
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    sean9c Senior Member

    Bow down trim was a measurement trick. After measurement anything that could be moved aft was. The boats didn't sail bow down.

     
  4. gonzo
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    gonzo Senior Member

    Paul B: I would appreciate if you were polite. Your rude remarks are the same as in the past. At the time we could and did beat the new boats on a reach, particularly on heavy seas. Some other Frers designs like the Cadetes and Supercadetes also did better on a reach than the new designs. On triangle courses the new designs had a distinct advantage. However, your comments amount to you calling me a liar. Look at the racing records of Gypsy III and UPA before doing that.


     
  5. DennisRB
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    DennisRB Senior Member

    Yeah, you are correct. I was thinking about todays cruising boats. Which I was using as a comparison as most IOR boats are now used as cruising boats. Just like the original posters boat is. As mentioned full blows race boats are so light and advanced that obviously they kick *** over anything 40 years old. Most IOR boats sail higher to windward than the flock of newer cruising boats like my Hunter and bene etc.
     
  6. Paul B

    Paul B Previous Member

    You made this claim, referring to IOR boats, in this thread: "They broach not because of the rudder, but because the bow and deck are under water."

    Is this statement true? No.

    Then, to try and buttress your argument you made this statement: "The regulations for spinnaker poles forces the sail to be really full on the upper side."

    Is this statement true? No.

    You compounded your error by adding this: "By the way, J24s are known for nose diving."

    Are J24s designed to the IOR rule? No.

    Are J24s "known for nose diving"? No.


    If you continually post things that are not true, then the way you are percieved is your responsibility.


    Please feel free to post results of the races where these boats beat all the latest IOR designs of the late 1970s.
     
  7. Paul B

    Paul B Previous Member

    Many Beneteaus with wide sterns are much faster to windward than corresponding old Pintail IOR designs. A Bene 40.7 is a good 20 sec/mile faster than an old 2 tonner pintail.

    The inability of your Hunter to get up the hill has little to do with the shape of the stern.
     
  8. gonzo
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    gonzo Senior Member

    J24s nose dive and are well known for it. Whether they are designed to IOR has nothing to do with the comment. Any photo of a IOR broaching shows the stern and rudder out of the water and the bow down. Therefore the statement is true and you are wrong; photos don't lie.

     
  9. sharpii2
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    sharpii2 Senior Member

    Did fractional rigs have to have bendy spars to be competitive? I've seen a lot of pre IOR boats with fractional rigs that had 'jumper struts'. These seem to be intended to keep the mast as straight as possible, or at least to keep maximum tension on the head stay (with a back stay). I also recall 12 meter boats having fractional rigs pretty much during that era. What was available later that wasn't available earlier to make the fractional rig more competitive?
     
  10. CT 249
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    CT 249 Senior Member

    Having done a few miles on IOR boats, I can't remember the rudder coming out and causing a broach. Given that something like a one tonner had a rudder probably 5' high and the stern wave was above mean water level, getting the rudder out would require the stern to be about 6' above normal level and I certainly cannot recall that. I know there are pics of a Farr 1 tonner (Cha Cha?) doing it, but it certainly wasn't endemic.

    Please see

    http://www.boatdesign.net/forums/stability/seaworthiness-14860-52.html

    It shows an IOR 50 broached without the rudder and stern out of the water. That was the first pic Google brought up.

    Out of interest,

    http://www.classicboat.co.uk/wp-content/uploads/2011/07/Cervantes-broaching-at-Cowes-Week-1967.jpg

    shows a clear case of a pre-IOR boat with a bad, bad case of downwind blues.
     
  11. sean9c
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    sean9c Senior Member

    Not really sure what your deal is with nose diving. J24's aren't known for it. Wasn't the issue with IOR hull shapes.

     
  12. CT 249
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    CT 249 Senior Member

    Gonzo, googling Gypsie III (or Gypsie III as IIRC you wrote it earlier) brings up nothing. Links?
     
  13. gonzo
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    gonzo Senior Member

    This was way before the Internet. In 1975 there were microfiches at best. I'll see what I can dig. It would be interesting to find something. UPA is still doing well for a 70 year old or so. I was onboard her two years ago.
    sean9c: When IOR style boats broached, the rudder got completely out of the water. The photos show that clearly. The problem started when the rudder ventilated and loss control. I find that boats with finkeels and attached rudders, even though less efficient in some aspects, have less tendency to lose steering.
     
  14. sean9c
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    sean9c Senior Member

    I'd think it's fair to say that any boat that is laying on it's side has it's rudder out of the water. So how is that possibly relevant to the conversation? The problem started because the boat started rolling, once it starts it amplifies until the hydrodynamics get so out of whack that it spins out. The problem is not the rudder it's the hull shape. Isn't saying a boat with a fin keel and an attached rudder a contradiction?
    Even if you could have a boat with a fin keel and an attached rudder if they were so efficient and great why don't we see a lot of them today?


     

  15. gonzo
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    gonzo Senior Member

    Finkeel boats with attached rudders were very common until the early 60s. After that only designed targeted for cruising had them. They are not as efficient or tack as fast, but the rudder stays in the water at higher angles of heel and bow down attitude. This link has drawings with different types of keels
    http://www.cruisersforum.com/gallery/showimage.php?i=2367&c=
     
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