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Thread: STIX and tinkering with PHRF

  1. #1
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    Default STIX and tinkering with PHRF

    Later this year I'll be selling my Lapworth cruiser and buying something a bit newer. I'm on the east coast, so the singlehanded racing scene is a bit slim. But I'd still like to get something that I can race singlehanded if I get a hair to do so. Initially I've been hankering for something like a Beneteau 33.7 or similar, but I'm slightly concerned about the bugaboo that has come up the last couple of years: Stability entry requirements.

    One by one each of the major ocean races (Chi-Mac, Newport-Bermuda, Pac Cup) are starting to invoke either Cat 1 or Cat 2 stability requirements. SSS Transpac hasn't done it....yet. If I want to enter a Cat 1, then it must meet a ORR Stix of 115. My conundrum is: all the newer boats with wide back ends less than 36 ft. don't meet the 115 requirement.

    So I'd like to know what the folks on the forum think about the stability issue. Will SSS require minimum stability in the future? What happens if it's 115 where many of the smaller sleds won't fit? In my investigation, most that would work are (ugh!) IOR influenced designs. What designs should I look at that are 32 - 35 ft. and have some furniture?

    Let the thoughts flow free.

    Jack
    Last edited by BobJ; 08-30-2013 at 10:40 AM. Reason: Changed thread title only.

  2. #2
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    not super relevant to your question, but my old Mount Gay 30 that traveled across 760 miles of open ocean with no keel doesn't even meet the STIX requirement...... Boat is not legal for OSTAR because of that. I think J105's are one of the relatively modern boats that comply. They're also relatively common as solo boats and should be fairly easy to singlehand. one of our local SSS guys has a J92 that he does quite well with.

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    As our friend Slacker pointed out on another forum, the Olson 30 has a stability index of 100, below the threshold even for Cat 3 as I recall. Yet the Olson 30 is the most popular and successful boat in the Singlehanded TransPac over many years. The J/105 is a favorite OD on San Francisco Bay because of its stiffness, yet it barely meets Cat 2.

    The problem is the calculation and use of these stability indexes. Boats from the same class have been measured with wildly differing results. Because of this, I will fight tooth and nail to keep STIX requirements out of our race rules around here. Are you sure Pacific Cup requires them?

    Here's part of one of my posts elsewhere about this:

    "LPS (limit of positive stability) for the J/92 varies depending where you look. Here in the US, ORR shows a STIX (not LPS) for the J/105 at 112 and for the J/92 and J/92S of about 110, so they're close. Neither the J/92 or J/105 (nor a bunch of other boats with ocean racing pedigrees) meet the cutoff of 115 for the LA TransPac, but Vic-Maui cuts off at 110 I think. No other West Coast races use a stability factor, to my knowledge. Chicago-Mac uses one in response to the WingNuts casualty but its use has eliminated some long-time participants so it has already been modified.

    There were two long threads on Sailing Anarchy about all this, where a couple of designers pointed out the inconsistencies in most of these indicies. You need to do inversion tests like the Minis and Open classes require - the calculated stability numbers are pretty bogus. In my observation, excess beam and cockpit layout have a lot to do with a boat's ability to right itself, yet it seems most focus on B/D and draft."

    If you want to compare some largely bogus numbers, go here, sort by Class and then scroll to the right hand columns:

    http://offshore.ussailing.org/ORR/OR...ward_50_50.htm
    Last edited by BobJ; 01-22-2013 at 07:12 PM.

  4. #4
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    pogen is offline Sailing canoe "Kūʻaupaʻa"
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    In PacCup, if you race PHRF there is no stability requirement. If you are Div F (fast), they race under ORR, which I think has stability minimums. I think Newport-Bermuda is entirely ORR, and some boats need to be modified (e.g. adding weight to bottom of keel) to meet some minimum.

    For our diverse, aged fleet, everything would have to be physically measured for it to be fair or make sense. Many of the numbers on many PHRF certs are erroneous.

    Interesting link there Bob -- for the Olson 40s the spread in stability index is from 119.4 to 138.7. Probably arising from using numbers from a sales brochure or some such, vs. weighed with all crap on board.

    The Tartan 10 fleet has their shit together, though, every single one of them right on the money at 128.3.
    Last edited by pogen; 01-23-2013 at 04:04 PM.

  5. #5
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    Yes, BobJ and I are in violent agreement on this issue. STIX is bullshit. The 115 level is basically arbitrary. The measurement is dubious, not taking deck & rig into consideration. The measurements are pretty wildly inconsistent. It's a static measurement to a highly dynamic problem, the likelihood of a wave capsizing your boat. There is no consideration for rolling inertia & the energy required to roll the boat. A T10 can race to Bermuda but a heavy cruiser with shoal draft cannot? Please. Olson 30's, Moore 24s, Mini's (i think) don't meet the standard.

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    The minimum of 115 (or ISO Cat A) in the LA TransPac is there for one reason and it has nothing to do with stability. It's to keep anything competitive and under 35' out of the race. Look at the entry list.

    That's fine if that's what they want - I just wish they'd be honest about it.
    Last edited by BobJ; 01-24-2013 at 09:52 AM.

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    is that a new requirement? a Hobie 33 was in our class in 2011 when i was on the 1d35. what does the hobie rate for stability?

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    According to that ORR chart, somewhere between 115 and 119. That Hobie just squeaked by.

    35' is not the rule but my point is that most competitive yet ocean-capable 35 footers wouldn't qualify for the race. e.g. you have a J/35? Sorry, not stable enough.

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    Thanks for the responses. I'll chime in again.

    The Hobie passes because it's skinny. Give it 1 more foot of beam and it would fail.

    I understand it is a field of competing problems: organizing authorities need to cover their a#$$# and to a certain extent, protect us from ourselves (whadoyamean I can't race my Laser in the Chi-Mac?), and competitors want to show up in their Laser...okay I exaggerate for effect. But I'm the first to admit that I would like to cover my a#$$# as well. This whole topic has me rethinking stability. For example, one boat I kinda like is the Beneteau First 35.7 (35s7). It has a stability number around 100. Now if I get caught in a good blow, 25-35 kn with 15-18 ft. seas, and I'm surfing down a good greybeard and at the bottom the autopilot decides to pack up. As I hang on during the wipe-out I'm pretty sure I'd be thinking that a boat with a stability number around 120 would be better at that moment. It might not be as fast or sexy or collect the same amount of silver...

    No, I'm not planning on getting an Luders 33, if that's what your thinking...

    Another choice is to get a boat that's close and bolt an extra 300 lbs. of lead to the bottom, like some have done to their Beneteau 36.7s, but I think that's playing with a bit of engineering fire.

  10. #10
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    PacCup positive stability requirement is 105 degrees... not as tough as LA Transpac. Though some common race boats still don't meet the 105 degree requirement... like a Santana 35 (wide boat with a relatively short modest weight keel). Took a Hobie to Hawaii one year... yes due to being so narrow and so light, they are initially very tippy (light shallow keel), but when heeled way over, they still prefer to float upright (narrow hull).

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