Improving IOR Stability?

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

  1. Paul B

    Paul B Previous Member

    This is not correct. If this is what was written in the article then the person who wrote the article should not have been writing it.

    That was part of the original intent. However, in parctice the boats evolved to something very different.

    Actually, the rule always favored the fractional rig. In parctice, with the materials available, the masthead rig was easier to get the best out of in the early years. As materials and techniques improved the masthead rigs went away. This started fairly early in the smallest classes (1975 in the Quarter Ton Class) and slowly made the way into the largest boats. By the end of the IOR all the competitive boats were fractional rigs.
  2. Paul B

    Paul B Previous Member

    Wrong again. The later IOR boats were much lighter and fuller in the stern, and capable of planing. This was a big improvement over the early pintails that were so dificult to control downwind.

    You must have been dreaming. No 43' boat from 1956 was going to beat a late 70s 43'er on any point of sail, and especially not upwind.
  3. Paul B

    Paul B Previous Member

    As much as we talk about the flaws, we should talk equally about the good points of the IOR era. There had never been a worldwide, universally accepted offshore rule to compete in. It allowed for great racing across the globe.

    It also spawned great ideas in hull shape and sail handling equipment. It allowed the industry to have a real-time R&D where sail shapes, materials, etc could be tried out.

    The thing we don't usually mention is the fact that the early IOR boats were faster and better handling than the boats they replaced (CCA and RORC types). If you didn't try to carry huge spinnakers DDW or on a close reach in too much wind they were pretty well behaved. Many old IOR boats were converted to cruising interiors and are happily living new lives.
  4. michael pierzga
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    michael pierzga Senior Member

    IOR wasnt to bad.. the boats were rugged and capable of long daul use life spans.

    Admirals cuppers lived long lives.

    The death of IOR and the great regattas came once designers had exploited all the rule measurement loopholes and had no where to go but exotic materials for a performance edge. Rugged fast alloy boats like Merrythougth, Toscana were out competed by expensive , lightweight, fragile composite cored boats who had no future. .
    A TP 52 goes to the scarp heap after its few seasons of racing.
  5. CT 249
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    CT 249 Senior Member

    Rudder fences, mentioned earlier, were tried and discarded in IOR days.

    I sailed IOR boats offshore from '79 to the mid '80s, including four Sydney-Hobarts and on a variety of boats from almost metre-style Peter Cole designs through to Kaufmans, Farrs and Dubois designs. MHO one significant issue is the rolling (itself partly caused by heavy displacement and pinched ends, plus large spinnakers) which caused the C of E to sometimes end up well off the centreline. Part of the reason this is less of an issue now may be better kite cloth, perhaps?

    My own boat, a pre-IOR half tonner by John Spencer of Ragtime fame, has a narrow stern but with no distortion in the buttock lines. She displaces about 2000kg on a 28' LOA (so much lighter than her contemporaries) and while she rolls heavily at times despite having chines, directional stability was excellent with the old shallow skeg-hung rudder and remains so with the current deep spade. There has been no significant in downwind stability with the big spade, which tends to indicate that a big rudder may not be a major issue in this case. In boats that are on the limit downwind in a breeze, things may be different.

    Some time ago I talked to a couple of legendary Sydney-Hobart winners who had owned top boats from before IOR all the way through the IOR period and on to IMS and IRC boats. They both emphasised that minor tweaks to an IOR design could have enormous benefits to handling. For example one of them (Lou Abrahams) noted that when his 1970 S&S design had her mainsail foot shortened for rating purposes, the rig imbalance downwind turned it into a bit of a pig. The same theme of minor tweaks greatly affecting boats was followed in Lou's later boats and in Fisher's "Ragamuffins".

    Directional stability may not come without issues. We've recently started racing my boat again, this time doing beer cans right up the end of Sydney Harbour, where the channels can get down to a couple of hundred metres wide and the wind bounces down in very fluky gusts. I'm just sailing with the wife and kids and rushing a half-rigged boat to the start so things are far from perfect, but I am still struck by the way that because the boat is so directionally stable, we are struggling a little bit in handling fluky gusts in big breezes, compared to boats that can turn faster when you get a 20+ knot increase in breeze and a 45 degree angle shift in a couple of seconds.

    Modern wide sterns can certainly be an improvement, but back in the IOR days when sailcloths and rigs were less well developed, the extra drag of the wide stern did cause a significant speed loss in the light winds that most boats normally sail in. For many people, speed downwind in a breeze was less important than light wind speed. And while modern boats use bigger and better rigs to get around the issue and therefore can drag wide sterns, those rigs cost a lot more than the smaller older ones and dollar for dollar, we may not have gained too much in some ways.

    PS - as noted, the J/24 was not an IOR boat and not noted for nosediving. On the other hand, my experience with old RORC designs (including owning my own for decades and doing two Hobarts on another) indicated that plenty of them handled better than later IOR boats, although that was not universal.
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  6. CT 249
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    CT 249 Senior Member

    It's not hard to do a bit of googling and see that that's wrong.

    Yassou/Wot Ever/Sailors with Disabilities was launched 2001 and still racing in events like this year's Sydney-Hobart.

    Bright Star, 9 years old, is now racing as Quest, won the 2008 Sydney-Hobart and is still doing Hobarts.

    Frantic, formerly Trader, is also 9 years old and still doing the Sydney-Hobart.

    Cougar II, ex Rush, was launched 2005 and at 8 years of age is still doing the Sydney-Hobart.

    Ragamuffin, ex Pegasus, was launched 2005, was 3rd in the 2011 Hobart, and is still doing Hobarts. So are Shogun and Calm (2006).

    So rather than being on the scrapheap, these boats are still getting on the podium in major events like the Hobart even when 4-6 years old and still winning their division when even older. I think Sailors with Disabilities was the first boat built to the rule and she is still racing hard. PEndragon, which was even earlier and inspired the rule, still seems to be doing long races.
  7. jakmang
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    jakmang Junior Member

    I am not sure if I understood you completely. You replaced the skeg/rudder combination on your boat for a large spade and it did not have that much affect on the rolling stability?

    Also you mentioned the stern "buttock" and/or "bustle". The SJ24 does not seem to have that (picture in earlier post), but is noted for bad rolling. I have heard the buttock makes the roll worse.

    I am more worried about rolling stability. I don't think the directional stability gets way out-of-hand until the roll maximizes.

    The picture shows the problem. If you look at the direction of the other boat and the wake, it is not pretty.

    Attached Files:

  8. Paul B

    Paul B Previous Member

    The Buttocks of your SJ24 tuck up a lot at the stern. This is the problem that can be helped by lowering the counter and making the stern fuller (as the IOR 50 pic I posted earlier).

    The boat in your pic is a SC27. The SC27 is known for good downwind characteristics. It has very fair buttocks. It has no IOR bustle. Yet it can still round down.

    Your boat, even with transom modifications, will never be as good as a SC27. So even if you do a lot of work to minimize the possibility of a wipeout, you will not eliminate the possibility.
  9. Paul B

    Paul B Previous Member

    There are probably a dozen TP52s here on the West Coast. After they get out designed and cannot compete in the MedCup Circuit they are purchased and raced all over the place. As 249 said, many are now in Australia, here on the West Coast, on the Great Lakes, the East Coast, the UK, etc.

    As far as I know none have been scrapped for structural reasons.
  10. Principles

    Principles Previous Member


    Fasnet 1979 Revisited

    The basic problem is the LCG (Longitudinal position of Center of Gravity) in relation with the CLR (Center of Lateral Resistance)

    Unstable/manouvrable Boat = Little Cargo Ship

    Transom ------------ LCG ----- CLR ----------- Bow

    Stable Boat = Weather vane = Aircraft = Dart

    Transom ---- CLR ----LCG --------------------- Bow

    (1) IOR Boat with rudder in action =

    Transom --- CLR -- LCG ------------------- Bow

    (2) IOR Boat without rudder (or 0.5 x rudder or 0.25 x rudder) (loss of rudder power) =

    Transom ----------- LCG -- CLR ----------- Bow

    (3) IOR Boat with ineffective rudder AND Bow down = Fasnet 1979:

    Transom ----------- LCG ------------ CLR -- Bow
  11. gonzo
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    gonzo Senior Member

    Paul B: I am not dreaming, we won several trophies on Gypsie III. Also, if you bothered to read my post, I specified that we only did well when the wind was off the bow. From a close reach to a broad reach our speed was higher. The extra handicap made a difference too. In really heavy weather, force 7 or more, we did well too.
  12. DennisRB
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    DennisRB Senior Member

    It has been mentioned that many IOR designs are still competitive. I think this is due to the shape being great for upwind performance. Many modern designs with wide sterns are fast and stable off the wind but slower to windward.

    I have been reading Eric Spoonbergs Design Ratios. Regarding the center of flotation. Boats with wide sterns tend to shift CF to the stern causing the keel to point in the wrong direction as the boat heels. DESIGN RATIOS.pdf

    I think IOR boats don't appear to have this issue which is why most can sail to windward on their own easily and faster than many newer boats. But the narrow stern is a liability downwind at or over hull speed, just as a huge transom is a liability for upwind performance. So its not all bad for IOR.

    If it were my boat, I would update the rudder. Just because I think it would be a fun project. And or possibly fair out any rule cheating water line meaurement points around the rudder area. If you do this you would do it at the same time as making the new rudder.

    I think many IOR boats are still the nicest looking. As long as you don't look side on at the stern with your head near the water level. Many I have seen have nice lines then right before the rudder the hull bottom takes a 90 deg turn upward for 5 inches (obviously the waterline measurement point) before continuing on just above the water line for several feet to the transom. I assume that when the boat is moving at speed the stern sucks down and the full waterline is then being used. However that ugly bump is in the way of the water flow which has to create huge drag and add to the instability issues.

    I'm no expert obviously.
  13. sean9c
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    sean9c Senior Member

    Don't agree that IOR boats are faster upwind than modern designs. The advances in spars, sails, foils alone make modern designs significantly faster upwind. Advances in materials and construction techniques have made hulls lighter and stiffer. Hull shapes are a lot more efficient.

  14. michael pierzga
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    michael pierzga Senior Member

    performance wise You cant compare IOR to modern boats.

    Im sailing an IOR boat right now. 1985 Ron Holland. The boat is 72.5 feet loa , 58.3 feet lwl, 13 ft draft and 40 tons.

    A modern 70 footer like a swan is 70 ft loa and 61.6 lwl , 13ft draft and 11 tons .

    The modern swan is longer, lighter and more powerful...The differences are too great.

  15. Paul B

    Paul B Previous Member

    Maybe you should learn to write well before you critisize those reading your nonsense. You said, "we could beat any new boat in wind directions up to 55 degrees or so." "Up to" indicates inclusive all below to the specified number. That would be Zero to 55 or so degrees.

    Your claim you could beat ANY NEW BOAT (offwind) is just ridiculous. Just as ridiculous as your other claims in this thread about the reason IOR boats spin out (nosediving!), those IOR designs called J24s that also nosedive, etc.
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