Guest Posted September 22, 2011 Share Posted September 22, 2011 Anyone know how to set up the boat for a pull down righting check test? I have the opportunity to pull mine over and I'll probably have to shortly anyway. Just had word another boat may have to do that as it may knot 'calculate up' right on paper and my thinking is that boat should pass this a lot easier than mine so I maybe right out in the 'No show buddy' zone. I thought we'd have a crack now to suss before spending a pile of time and coin we may end up knot being able to use later. Do you have sails up or down, any weights hanging off the rig or anything like that? Anywhere that lists how it's supposed to be done? Quote Link to post Share on other sites
Atom Ant 0 Posted September 22, 2011 Share Posted September 22, 2011 Grab the mast head, pull it down, then let go. Never seen sails on when it's being done. Quote Link to post Share on other sites
Guest Posted September 22, 2011 Share Posted September 22, 2011 Page 27 of YNZ Regs. Rule 6.2 (d). No sails hoisted. Valid for Cat 4 and 5 only. Cheapest way for Cat 3 and 2 is to do an ORC certificate through YNZ Quote Link to post Share on other sites
Atom Ant 0 Posted September 22, 2011 Share Posted September 22, 2011 And lets face it, why would you bother for cat 4 or 5? Yeah plug the numbers in for cat 3 and you're away. got me one of those for the Ant. I declared all my downwind sails and they hammered me. Didn't care as I never intended to race under ORC Club, but it's good to know that with ALL my downwind sails declared I might need to be faster than Rambler to win on corrected! Quote Link to post Share on other sites
markm 30 Posted September 22, 2011 Share Posted September 22, 2011 Jono, not sure that's still the case. ORC went up sharply last year, now I think similar or higher than IRC. That said, I don't know how much the alternatives cost so it may still be the cheapest. Quote Link to post Share on other sites
John B 106 Posted September 22, 2011 Share Posted September 22, 2011 I know of a Cav 45 which needs to establish its righting moment to get rated. Seems a little over the top( no pun intended) Quote Link to post Share on other sites
Absolution 7 Posted September 22, 2011 Share Posted September 22, 2011 You can get a naval architect to do it. I talked to BBW about it when I was going to do the keel on Apparition. You basically have to hang weights from the boom, swing it out to the side, measure the heel and then he does a bunch of calcs to determine the stability index. Quote Link to post Share on other sites
Guest Posted September 22, 2011 Share Posted September 22, 2011 BBW did one for me a few years back - he was good enough to lend his digital level to get the heel angle bang on. We hung 20kg weights off the boom and measured heel and pitch fore and aft as we loaded her up. KM if its for the mighty 930 surely a calculation exists? The cost is in the modeling if they dont have the hull form as a design file. EE Quote Link to post Share on other sites
Fish 0 Posted September 22, 2011 Share Posted September 22, 2011 Don't know anything about the pull down test but we have done an incline test. The test itself is straight forward, get a digital spirit level and a dead calm patch of water with no tide or wind or wake, hang progressive weights of the pole or boom at right angles to the boat and measure the induced heal. BBW is the man to speak to. He needs to produce a computer model of your boat (a 930 should alredy be on file) and run your numbers. Quote Link to post Share on other sites
Guest Posted September 22, 2011 Share Posted September 22, 2011 I have zero faith in calculations and will be doing a pull down anyway for my own peace of mind. Calculations did very clearly state the many now totally fucked canting keels would be fine, Speedboats keel was fine, the Space Shuttle was fine, 3/4's of NZ Finance companies were fine, the odd E boats keels were fine, the Green Party knows economics and a massive amount of other knot good examples. Actually doing it is far superior and a lot harder to argue with. Which does make it very very bizarre actually doing it is OK for only Cats 4 and 5. Can anyone name a boat that's fallen over and stayed there or had a keep drop off while inside Auckland harbour? Can anyone name a boat that has that happen to it in Cat 1 or 2 waters? I think we all know the list would be heavy in the deep blue column and rather lite in the harbour column. To me that suggests the powers that be have the rules arse forward. Also rather bizarre that a very very top end, highly state of the art, very highly engineered that races very short handed in the most extreme waters the world has to offer have to.... what???? Do a actual pull down test. Looks like the people who do do it hard also think calculations aren't accurate. 'It must get modelled' is nothing more than a PC driven make work scheme for the buddies of the powers that be, which sadly does seem to be the way of the world these days. Sure if you own Mirribella you have little choice but I don't and I do. Quote Link to post Share on other sites
Guest Posted September 22, 2011 Share Posted September 22, 2011 Leave E boat keels out of it KM, I'll come help you do the pull down test, it could be most amusing. Quote Link to post Share on other sites
chic014 0 Posted September 22, 2011 Share Posted September 22, 2011 Is it just me or is it that the people who have no faith in calculations don't have the ability to do the calculations? Quote Link to post Share on other sites
Atom Ant 0 Posted September 22, 2011 Share Posted September 22, 2011 dunno really. I can't do calculations so I place my trust in those who can, but if I was in a boat that was going arse up I don't know if I could do the calculations in my head fast enough to stop it going right over Quote Link to post Share on other sites
Guest Posted September 22, 2011 Share Posted September 22, 2011 I only have little faith in many calculations purely as so many have been proven totally bogus or at least somewhat inconsistent causing some deaths. Just like a house Building Certificate, often worth less than the paper they are printed on as many have found out also but luckily they don't die doing so, when talking housing. Some will have detected a large amount of Grrrrrrr.... in my previous post only cause there was. Having to waste time and money on something no one will stand behind just to cover some bureaucrats arse annoys the crap out of me, especially as by Sunday nite I will actually know if she will come back up or knot in reality. What's more we will give it a crack with the sails up as generally when you get knocked down they are up. It's knot rocket science, why try to make it so? Sorry EE, they got caught in the red eyes of semi-rage Quote Link to post Share on other sites
Absolution 7 Posted September 22, 2011 Share Posted September 22, 2011 First its a fear of black boxes now a fear of science. I should have guessed that you don't believe in the laws of physics, if you did then you'd never ride a motorcycle again. Do you also believe that if someone takes a photo of you that they will steal your soul? Quote Link to post Share on other sites
wheels 543 Posted September 22, 2011 Share Posted September 22, 2011 If the boat is a common design, the the stability figures were done right back at the beginning with the first boat and the designer should be able to supply those figures. It is only when the Keel or Mast is played with that those figures go out the window. When I read that I needed to perform the stability test to get Cat 1 I thought well that blows taking a Tahitian offshore then. But the inspector I talked to said no the tests are for new unproven designs and that I would not have to produce those figures, because these Tahitians had been sailing all over the world for years. I do hope that still is the case. Quote Link to post Share on other sites
Guest Posted September 22, 2011 Share Posted September 22, 2011 And don't forget the world is flat!! It's knot the Laws of Physics Mish, it's the way in which they have been used. It's shown Physics is pretty good but the use of them has caused many 'marginal' and fatal moments. I don't fear that much but I do believe so intensely you'd find it hard to believe, that in boating and many other things, most important thing the user/owner has to have is 'The Feel Good Factor'. So if I'm sailing over 10000mts of water I WILL Feel Good knowing what the boat will do as it has physically happened and more so if I see it happen. If she doesn't come back up I will know, if she does with easy I will have that feel good factor. Calculations are numbers on a sheet. Are they right or are they wrong, how am I to know? Can Fineline, Chic014 or some dude in a office somewhere tell me with 100% certainty or at least to anything close to the level of certainty 'actually doing it' will show me, the calced numbers are correct (assuming it calculates up OK) so that if I get knocked over large the boat will come back? If you believe in what you are saying you can answer that question right here right now. Bare in mind that if I do take your word for it and then do get knocked down, stay there and die, I will make sure every time you get your leg over your missus you'll look down only to see me smiling back at you Hey, I don't mind calculations, do them myself daily and know there are often times you have no choice but to do them and hope they are right. But with my boat it's faster easier cheaper and more accurate to just pull the bitch over and let the masthead go. Inside 1 minute we'll know for sure one way or the other. To be told that is unacceptable and I have to take a punt on someones calculations is just 100% bollocks, pointless and a waste of my time. All this is about that Feel Good Factor. Get a Cray computer to calculate the living crap out of the Laws of Physics, Law of Gravity or even Murphy's Law and it ain't never gonna ever give me that. Quote Link to post Share on other sites
Guest Saturday Night Special Posted September 22, 2011 Share Posted September 22, 2011 here here I applaud you Knotty my computer design programe has all the figures required but in reality till the boiat has been through the practice nothing is proven .I know of a half tonner that spent a long time upside down off cape kidnappers in the early 70's and did not want to come upright untill some drastic rocking action was taken from inside the hull but it had all the right calculated figures. Quote Link to post Share on other sites
Fish 0 Posted September 22, 2011 Share Posted September 22, 2011 So what wind and sea state are you going to do your test in KM? Good cyclone conditions with a fetch built up over a few thousand miles, or are you going to pull it down and watch it pop up in a nice marina or calm bay somewhere? I think what you are really after is an understanding of the safety factor of your boat, i.e. the margin of error in the dreaded calculations. If you are going to do a pull down test don't forget to put plenty of heavy loose items inside to shift about and slow it coming back up, you, a mate and a couple of slabs of beer should about cover it Point is, even a pull down test wont prove your boat will come back up in real conditions, or with a different amount of shite inside / sails / people/ liferafts / food / booze etc, and a pull down test is qaulitative, i.e. it proves it pops back up on that day in those conditions. If you run some numbers you can understand your safety factors, and then determine how much more rum you can have onboard and still pop back up with... Quote Link to post Share on other sites
johnMi 2 Posted September 22, 2011 Share Posted September 22, 2011 EE One boat you do NOT have to worry about is the Elliott 7.4 If you have a look at the SRI of Trailer yachts the E 7.4 was more than double the numbers of the next closest trailer yacht. However, when I owned Elliott 7 I think it only took a few Kilos to hold the mast level with the water. But as soon as that weight was removed it bounced up quickly. Knot Me The biggest issue with a knockdown (from experience on Elliott 7) was the action of the crew, 5 guys not wanting to get their feet wet, then when the water got on top of the sail, that compounded the problem. The windage was quite high and the mast tip was being 'pushed' into the water. If there had also been big seas, I think we would have had it go completely upside down. It only took one of the crew to climb thru the lifelines for it to come back quite abruptly. As Fish said, it's the things (in my case crew) that move to the most inconvenient positions that cause the problem. Quote Link to post Share on other sites
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