New to cats and just picked up '81 Prindle 16 and trying to decide if it makes sense to upgrade current Hawaiian system lines or just go with righting line. Usually solo and wonder if anyone has any thoughts on which may be more effective.
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J.D.
1981 Prindle 16
1978 Y-Flyer
Akron,OH
USA
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Hawaiian Righting Systems
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Posted: Jun 15, 2015 - 10:14 PM
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Posted: Jun 15, 2015 - 10:51 PM
jdb,
The reason for all the extra rigging of the Hawaiin righting system was to speed up deploying and stowing the righting line to lose less time during a race.
So normally a simple large diameter non-water-absorbing line tied to the dolphin striker post that you can throw over the top hull is simpler.
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Damon Linkous
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Posted: Jun 15, 2015 - 11:38 PM
Makes sense, I'll go the righting line for now. Thx
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J.D.
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Posted: Jun 17, 2015 - 09:18 PM
Simpler and more effective than most Hawaiian systems because you throw the line over the hull, giving you more leverage on the boat. The Hawaiian systems are mostly under the tramp and under the hull.
Tie knots on the righting line to help you pull yourself up out of the water, and consider making the line long enough to tie a loop in the end that drops into the water to help you get a leg up on the issue.
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Posted: Jun 18, 2015 - 01:06 AM
Well not actually, with the throwing over the hull thought. Righting a cat is a buoyancy problem. IE its all dependent of your righting weight being as far out as possible. Kind of like a keel on a mono hull. The physics of the problem doesn't care how the weight gets out there. Balancing your weight out by pulling under the hull, pulling over the hull, or pulling from the dolphin striker all have the same effect in righting a cat. Now if you were righting a boat on land the higher you have a line the better, but in the liquid the math doesn't care. -
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Posted: Jun 18, 2015 - 10:47 AM
I like the Hawaiian system, not only for the very quick deployment, but also for the ease of hooking into my harness. And I have also been sold on the theory that the righting force generated is independent of whether the line pulls from over or under the hull. You can search the catsailor open forum for some extensive posts on the physics involved if you wish.
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Posted: Jun 18, 2015 - 10:09 PM
This is wrongful thinking. It is simple engineering problem, you are just dealing with a glorified teeter-totter. It does not matter where the line travels, or is attached.
The problem is simple math. You have a lever arm,(mast) on one side trying to keep you on your side. You have your mass hiked out on the other, trying to right the boat. If your lever arm is greater than the mast lever arm, the boat comes up.
Draw out a vector diagram, you will see that the righting line angle will make it easier, or harder to hike out, but the summation of moments,(and whether the boat rights) remains the same.
Rope over the hull better= old wives tale.
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Posted: Jun 19, 2015 - 01:17 AM
Chris, you may want to draw out your vector diagram again. Remember that you upper hull is not vertical it is past vertical on the mast side. Say X is horizontal and Y is vertical (with respect to gravity). Taking moments about the lower hull: the moments that are resisting your righting moment.
A line load representing gravity on the mast multiplied by the distance to the lower hull (note that the mast it at an angle so the moment arm will change depending on how deep the mast is) , a similar load representing the weight of water on the sail (if any, which is why you let out your traveller and mainsheet when you are righting), the weight of the boat multiplied by the distance to the lower hull.
On the righting moment side you have the bouyant force of the mast provided its sealed (very important to righting), and the two components of the moment for your righting line (x and y), because the righting line is at an angle you have the x force multipied by the distance between the point at which the force is applied (above or below the hull). If it is above the the distance is approximately 8 ft (for most boat), below the hull this distance is closer to 6.5 ft (depending on the thickness of the hull) and the y force which is multiplied by the distance from the point of contact to the lower hull center of gravity. If under the hull the y force applied at the maim beam and multiplied by the distance to the pivot point on the lower hull (say about 2 ft) this moment is actually resisting the righting of the boat because the top hull is past vertical. Now if you threw the rope over the top of the hull the bearing surface is at the keel (that is where the pressure is being applied) so the y force is multiplied from the keel to the pivot point on the bottom hull. If the boat is past vertical by 2 ft and the hull is 2 ft deep then the moment arm is 0 and the force isn't hindering you.
Probably easier to to draw a diagram of that and sum up the moments, I'll see if I can find time to draw it up tomorrow.
OK to sum up what the above says to me:
1. Keep you mast sealed and make sure it floats as high as possible, this reduces the moment arm of the keeps the weight of boat and reduces the potential of your own righting force from acting against you.
2. Get that sail as close to vertical in the water as you can, you likely cant right a boat if you have any water in the sail. Its hard enough with just an 80 lb mast and some rigging.
3. Hike out as far as possible, the closer that the righting line is to vertical the more of that x* boat width force you will get, the y*hull width is a much smaller moment.
4. Throwing the rope over the hull extends the moment arm farther than under the hull and therefore will give you more righting moment and will also bring the vertical moment are closer to the pivot point and may in fact help you.
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Dave Bonin
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Posted: Jun 19, 2015 - 11:28 AM
Well, Not actually on this point.
This is correct if your boat was on land when your pulling the boat over. But, were talking about righting a boat on the water -
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Posted: Jun 19, 2015 - 01:20 PM
It makes no difference to the calculation if you are on the land or the water. The only difference is on land the pivot is ant the bottom of the hull and in the water it is at the water line in the middle of the bottom hull. The only thing that changes between the two calls is the length of the moment arm for the righting moment. Under the hull the force is applied at the main beam so the x component is closer to the pivot and the y component is farther. Over the hull the righting force is applied at the keel of the hull so the moment arm for the x component is longer and the moment arm did the y component is shorter. I.e. Over the hull gives you more force provided the angle of the righting rope is the same. Given that this isn't the case it might be a wash, but anecdotally I find over the hull easier in all cases.
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Dave Bonin
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Posted: Jun 19, 2015 - 01:42 PM
Since I just did this two days ago....
I would have preferred to have a big ass honking dia. line over the hull with knots, one for front and one for the rear guy to hold, instead of a smaller looped line attached to underneath the hull. Less moment. Thin lines=quicker burnout of hand muscles...
The leverage /arm would have been greater I suspect with more applicable force for righting. Also, I ended up on the tramp with the loop around my waist and I was pinned! Took a few minutes to maneuver to get out of the righting line. (I left this out of my 3 Splash edition... HA)
Most critical: mast must float and you must teeter totter on the hull to get the right ballast to allow the bow of the boat to weather into the wind. If not, its not coming up. How do I know this: after 15 minutes tugging on the lines while sail was directly down wind, I said, we need to get air underneath the sail..... hence the ballet routeen on the hull...
Not hard, just have to have the right technique and dia rope attached in the right spots.
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Posted: Jun 19, 2015 - 04:02 PM
I've seen this argument before but can't remember how it came out, carry on. I do remember it didn't change anyone's opinion. My only input is that on my Hobie 18 I had the Hawaiian system rigged and found that it was harder to hold the line from below the hull and lean out because of the angle. Instead of hanging from the line from over the hull I was pulling straight out.
Next we can discuss whether to trailer with the rudders on or off.
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Posted: Jun 19, 2015 - 05:05 PM
Vertically challenged sailors have difficulty reaching a system that can't be tossed over the hull such as a Hawaiian Righting System even on a narrow boat like a Hobie 16.
I was waiting for that also Damon. I'm a rudders off guy but there was a time I did trailer with rudders on.
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Ron
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Posted: Jun 19, 2015 - 05:34 PM
I did sketch out the vectors today and ran the equations but nothing legible enough to post. I'm quite sure about the geometry and forces. If you really want me too I can probably get one of my cad minions to draw it up pretty. Not that it carries any weight on the internet but I am a hydrotechnical engineer so I think I understand the physics pretty well. :)
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Posted: Jun 19, 2015 - 06:53 PM
Skyward hull appeared to cant towards you as you moved further aft on lower hull. Not sure how that would aid moment...
Edited by goodsailing on Jun 19, 2015 - 09:22 PM.
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Posted: Jun 19, 2015 - 09:08 PM
Rudder on or off on my Venture 15 is simple. Since they are bolted on and have shim washers on each side and a lifting lever ? bolted on top. Bolts hold the whole assembly to the hull. The only time I have had them off was when I first got it 5 years ago. End of meaningful discussion.
Edited by goldwingnut on Jun 19, 2015 - 10:52 PM.
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Posted: Jun 20, 2015 - 03:59 PM
Many an engineer has argued this one.....'bout half were right and 'bout half were wrong!
Referring to your earlier post, the angle of the righting line can't be the same for over vs. under and that's the key. Over makes it easier to hold the line but doesn't change the righting moment. Ironically, this discussion was just debated (for the 1,000,001th time) over on the Hobie forums. For the record, I use a strategically knotted large diameter (1/2"?) line that I can fling over the upper hull. I'm one of those vertically challenged people who'd have to run the Hawaiian style under.
No one's biting on Ron's rudders off comment? Then maybe we should argue the merits of waxing?
Jerome Vaughan
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Righting line over ('cause I can)
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Edited by rattlenhum on Jun 20, 2015 - 04:01 PM. -
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Posted: Jun 21, 2015 - 12:22 AM
Yeah that angle is the one thing I'm not sure about. My gut still tells me I'm getting better leverage over the hull though. To each his own.
I have no good opinion on the rudder debate. I've trailered with and without. With them on they are a pain to tie up so they don't move. With them off you save a few minutes of setup but have to lash then to the tramp. Depends on how lazy I feel. I've never waxed my boat. Again too lazy, I'd rather be sailing.
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Posted: Jun 21, 2015 - 05:59 AM
That was my first thought Dave, & I believe it has merit, IF the righting force could be applied parallel to the water.(The longer the lever the easier ) In fact, we had a brilliant idea to rig up a 3' "extender" that would slip into the end of the Nacra beam, then put the righting line into a notch at the end. With that extra leverage my daughter should be able to right the 5.7, no?
It didn't make a damn bit of difference. That's when I realized the length of that lever arm didn't matter, it only changed the force,(and ability to hang on) on the righting line.
The end result of all the vectors is the mast/sail/water on one side of the equation, & amusing you can hike straight out, your mass, & how tall you are on the other. It's sort of like a cable stayed bridge. If you place an 18" block of dense foam, with a wedge cut into it to make it stay against the hull, then stand on the block, you can easily solo right a 5.7.
We tested this last summer, but the foam was kind of bulky, & a bit of a pain to secure to your leg, or the boat.
On the 20' Mystere, it took 2 of us to right, until we put the wings on. Then it was a be-itch, with a Capital B. The wings were not that heavy, but all their mass was over center with the Cat on its side.
That required 2 of us + the bag, & a Hobie bob to prevent turtle.
To hack with wax, I think we should dimple our hulls, like a golf ball.
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Posted: Jun 21, 2015 - 12:43 PM
Ed nailed it. His beam extender made the line easier to hold, but could not change the righting moment so long as his weight was in the same place. You'd get the same moment with the righting line tied down closer to your feet, but at some point, it would be impossible to hang on. To increase the moment, you'd have to get your body out further from the lower hull (without it going into the water and neutralizing your weight) ....like with Hobie Gary's Solo~Right or some such pole system.
If I sailed in Canada, I probably wouldn't waste a second of the season waxing either!
Dimpled hulls.....hmmmmmm.......they'd probably just make an H16 pitchpole easier!
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