Wind/Wave limits for old IACC yachts - SailNet Community

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Old 09-23-2011
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Wind/Wave limits for old IACC yachts

you might remember some of the '95 and newer boats breaking in relatively benign conditions (example one Australia 35 in San Diego in 1995, even though arguably there was some crew error involved) ). If I recall correctly, IACC race comittees would cancel races above 20 knots, but often wind speed is not even so critical as compared to sea state. Does anyone have knowledge of the design briefs for these yachts, specifically '92 and '95 vintage. Some of the charter outfits have taken these yachts out sailing in pretty strong breezes but usually flat waves.

For example, would you want to be on one of the old '95 vintage yachts beating into 6-10 foot waves for hours without a life raft on board ?

then, as a follow up question: Many of these older IACC yachts doe not have a lot of stringers / bulkheads..
has anyone seen people owning these yachts going ahead and retrofitting stiffening inside the boats to make them
more sea worthy. What about the keels? are they designed to last one season of IACC racing ?

apparently high winds are not the problem, it is the sea state and "user error". Once beating into steep choppy 6 foot plus waves, all bets are off ? I saw some IACC yachts inside, and there seem to be very few stringers / bulkheads forward. Also it seems - looking at some finite element analysis of IACC yachts (saw a stress distribution diagram of AUS 35 published somewhere) the highest loading is at the leward genoa track in the deck. so, shock loads there and slamming loads in the lower bow section would be the worst case scenario. What about the keel box? most IACC yachts have the "slotted" keel -hull connection which seems to be much stronger than the more conventional keel flanges bolted against the hull. Yes keels have fallen off but in many of those cases prior grounding or other issues were at fault..
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Old 09-26-2011
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Originally Posted by lead_ior50 View Post
you might remember some of the '95 and newer boats breaking in relatively benign conditions (example one Australia 35 in San Diego in 1995, even though arguably there was some crew error involved) ). If I recall correctly, IACC race comittees would cancel races above 20 knots, but often wind speed is not even so critical as compared to sea state. Does anyone have knowledge of the design briefs for these yachts, specifically '92 and '95 vintage. Some of the charter outfits have taken these yachts out sailing in pretty strong breezes but usually flat waves.

For example, would you want to be on one of the old '95 vintage yachts beating into 6-10 foot waves for hours without a life raft on board ?

then, as a follow up question: Many of these older IACC yachts doe not have a lot of stringers / bulkheads..
has anyone seen people owning these yachts going ahead and retrofitting stiffening inside the boats to make them
more sea worthy. What about the keels? are they designed to last one season of IACC racing ?

apparently high winds are not the problem, it is the sea state and "user error". Once beating into steep choppy 6 foot plus waves, all bets are off ? I saw some IACC yachts inside, and there seem to be very few stringers / bulkheads forward. Also it seems - looking at some finite element analysis of IACC yachts (saw a stress distribution diagram of AUS 35 published somewhere) the highest loading is at the leward genoa track in the deck. so, shock loads there and slamming loads in the lower bow section would be the worst case scenario. What about the keel box? most IACC yachts have the "slotted" keel -hull connection which seems to be much stronger than the more conventional keel flanges bolted against the hull. Yes keels have fallen off but in many of those cases prior grounding or other issues were at fault..
I have no experience at all with these boats but I recall the incident in S.D. where the boat folded up at the mast and went down. I had seen photos of the boat before that and remember thinking the layout of the cockpit was dumb - it went right up near the mast and had sharp corners where it turned straight across athwartships. I thought at the time that was a major stress riser since there was essentially no side deck after that point, no bulkhead or anything else. To my eye, the cockpit opening should have swept aft in a long curve from tangent at the mast, to distribute the enormous stresses. The way it was laid out was just like a scribe mark on a piece of glass - that's where it breaks, every time.

I was proven right shortly after making that observation to myself when the boat folded neatly in 1/2, right at that point, and went down.
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Old 09-27-2011
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I know nothing of this boat. Is this the one?
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Wind/Wave limits for old IACC yachts-wbfloponeaustralia_gallery__600x362.jpg   Wind/Wave limits for old IACC yachts-oneaustralia_-_aus_31_simpletopbig.jpg  
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Old 09-27-2011
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I know nothing of this boat. Is this the one?
I'm not certain - the sinking photo looks right but the overhead shot of the deck isn't as I remember - I recall it as much more extreme - right at the mast and straight across.

How often has it happened?
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Old 09-27-2011
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From photos I've seen of these boats used for 'tourist' daysails they always seem to be heavily reefed. I'm sure they are sailed rather conservatively relative to race conditions.. though ironically the wind speeds in the Caribbean where many of them reside are often in excess of the 'race limits' that were in place at the time....
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Old 09-27-2011
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thats right, it is the sister of AUS 35, the yacht that sank in San Diego. Their deck layout is similar. I agree with the previous poster, not having a deck section in the highly stressed area was detrimental to the stability.
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