Anybody remember high school physics/

yeah, my brane stil herts. You're right.

Physics aside, it's all about leverage. I think of it as claw hammer pulling out a nail. The further up your force on the handle of the hammer, the easier it is to pull out a nail. Hence, the further your weight is south of the hulls, the less force (weight) it will take to right your boat. Righting poles act as the handle of a hammer.

Alfred: Forget wracking your brain with the physics and take my word that it has been empirically proven that 200 lbs. on a pole is not enough to right your boat in all conditions. Forget the pole and get a bag. It is hooked to the boat like a righting line, so you're just using your strength to push it out away from the boat, not hold it up. If you wish, you can buy/rig a 3:1 tackle system with cam cleat to make it easier to deploy. To further reduce the load on your arms, put some strategically placed knots in your righting line that you can easily slip (and unslip) your harness hook over. This also frees your arms to deal with balancing the bag over your shoulder.

First things first...make sure you're mast is sealed.

Jerome Vaughan
Hobie 16
Clinton, Mississippi

[quote]
So if a crew weighing 300lb can right the boat using a 5ft pole, then the torque is 300lb x 5ft = 1500lbft.
sm [/quote]

I have a new boat and we haven't been over yet. My wife and I weigh 300 lb. The boat has a mast bob float.

Are you saying we will always need a pole or bag to get it up ?

I have been researching this topic for a few weeks now. It seems that the obvious has been stated. If poles worked, they would be more available commercially at this moment. Since righting bags are what you find, they must be the simplest and easiest to use.

I wanted a righting system so I can sail solo. I don't weigh enough to bring the boat up by myself. Having a pole sounded like the easier of the two avialable options with quick setup and fewer moving parts.

Please, build a few poles and try them out. Let us know the empirical results of your endeavors. Post photographs!

_________________
sittin and floatin, waitin for the flush

I believe the instruction manual says that a total weight of about 230 lbs. is required to right a Hobie 16. That weight hanging out on the righting line would act through the center of gravity of the people which probably is at their waistline. That would be about 3' from the down hull with a resulting turning moment (or torque) of 3'X230lbs.= 690 ft.lbs. For one person at 200 lbs. hanging on a pole to achieve that torque, the length of the pole out from the down hull would be 690 / 200 = 3.5 ft. To replace a 300 lb. weight of people, 3'X300 lbs.=900 ft.lbs./200lbs.=4.5'.

The pole would have to be longer since it would start at the crossbar. The length has to be out from the down hull.

TonyB should be able to easily right an H-16 with the combined 300 lb. weight without any devices.

In a strong wind, it is possible to use the jib to help lift the mast by travelling it out on the low side and pulling in the jib sheet ahead of the cleat. With the mast angled part way off the wind and not directly into it, the jib traps air and adds lift as you hang out on the righting line.

_________________
Howard

Tony: My daughter and I are about 300 lbs. combined and can right my '98 Hobie 16 fairly easily without any help from the wind and just a righting line....no bob, pole, or bag. I'd recommend that everyone practice in controlled conditions with help nearby, though. It really helps ones confidence to know you can right your boat well and quickly when it counts!

Jerome Vaughan
Hobie 16
Clinton, Mississippi

Howard: I have not read that manual, but I do not believe that 230 lbs. is nearly enough.

Just to add some specific experiences to this important thread.....My friend and his wife (~250 combined) could not right his H-16 using a ~ 8 foot righting pole. Without help from the wind, I (~180lbs.) must have my large Murrays righting bag VERY full in order to right my H-16 solo. On the other hand, in a blow, I've righted it a couple of times solo without the bag.

I believe it's best for everyone to be able to right their boat reasonably fast in all conditions. You can't always count on the wind to help. I've had a puff knock me down when I wasn't paying close attention, and didn't have enough wind to right solo the rest of that day (plenty enough to blow me onto some rocks, though!). I've also had a trap rope break while on a beam reach....again, plenty of wind to capsize fast(!), but not enough to help me right solo.

Be safe all....and be prepared so you can push your limits more safely!

Jerome Vaughan
Hobie 16
Clinton, Mi'sippi

Jerome,

The 230 lb. number sticks in my mind from some time ago. I have never had a problem with two people to right the boat, though alone, it takes some help from the wind and the jib. I have only done that once. I have been sailing the same boat for 23 years and don't go over too often. I tried to find the manual but I can't locate it. I might not remember it correctly. They say when you get old there are three things that go, the first is your memory but I don't remember what the other two are.

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Howard

Thanks Howard for weighing in on this topic.
I have a 1987 manual and they say you need 300 lbs for the Hobie 16. I was really hoping you were right about 230.



That is what I am seeking, empirical proof of what it would take, to see if there is a practical solution.


Crayfish- Thanks for the encouragement. I have been relearning the physics of torque and have emailed to local physic teachers to see if they will help me with the calculation.



Here is what I think I understand so far. The lower hull or pylon is the fulcrum point. The frame to upper hull is the moment arm.
Torque is generated at 90 degrees to the direction to of the force. 100 lbs applied perpendicularily on 10' moment arm generates 1000ft/lbs of torque. If they angle of force changes from 90 to 37 degrees the resulting torque is only 600 lbs. see this site for full details:
http://physics.uwstout.edu/statstr/stat ... tat131.htm
This means that 300 lbs hanging down & out on a righting line(s) is not generating its full potential of force.
This is all I am sure of so far. I still have questions about calculating the torque that the 300 lbs on righting lines is actually generating, so I stopping here until I get more info. Once I understand how to calculate this (I have the forumulas, but I am not sure what the effective length of the moment arm is), I can then figure where you'd have to place 200 lbs to equal it.
It still may end up too far out to be practical.

_________________
Alfred
'87 H16 Sail 89907
If you aren't sailing on the edge, you're taking up too much room.

Alfred,

I am surprised that I was so far off on the weight necessary to right an H-16. As to calculating the moment from the 300 lbs. holding on to a righting line, you need to know where the center of gravity is (about at the waist) and how far out horizontally that is from the point of rotation (the down hull). The weight acts vertically due to gravity and the horizontal distance gives the moment arm length. That compensates for the trigonometric calculations you are trying to make. If you assume 3' as the horizontal distance from the hull the turning moment is 900 ft.lbs.

If you wanted to calculate the torque required to right the boat in ft.lbs. you would have to calculate all turning moments around a single point and that point can be anywhere. Usually you would choose a point like the down hull since that force (the supporting water) would be multiplied by 0' and cancel out. All forces but one act vertically due to gravity. The one that isn't is the wind on the tramp. In addition you have the weight of the boat, center of gravity probably near the tramp, and the buoyancy of the mast acting vertically up. The sum of these moments being careful to use + and - values will give the required moment. The wind force in inches of water can be calculated by (velocity in fpm divided by 4005)the quantity squared. 4000 fpm gives a force of 1" of water column. The truth is, trial and error would give the best answer.

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Howard

[quote="hrtsailor"]

The 230 lb. number sticks in my mind from some time ago. [/quote]

If it is 230lb, the bob weighs 5.5lb and the mast is 25ft. If the righting moment arm is assumed to be 3ft, this makes the righting weight required close to 280lb ... a 20lb margin for us !

(I added the bob after an end over end, turning turtle and having my wife trapped underwater beneath the tramp.)

Tony,

I can see where the extra weight of the mast bob adds a lot to the turning moment needed. I believe that the comptip mast is heavier than the all metal mast. If so, it too would add a lot more to the load, especially since it is the upper end of the mast. I wonder it is heavier and by how much. I have pitchpoled but never where it turtled. That sounds like a terrible experience. I hope you wife wasn't hurt.

_________________
Howard

I will add, that at minimum weight, (285lbs), and not much wind a HC16 is hard to right.



I'm real good at tipping over in not much wind. Lots of wind too for that matter.

As I recall the 16 weighs 320lb. I'am guessing each hull weighs about 100to 120. The mast&sail weighs(30-50)? Tramp&beam&crossbars(20)? the tipping point is to get the mast a little more then parallel to the water. At that point the upper hull will be at the fulcrum point of the lower hull. The mast angled in the water (without a mast float) puts it at 20 ft from the tramp. So the upper hull's center mass should be about 2ft from the Centerline of the fulcrum. The lower hull's mass effect is negligible, the mast&sail center of mass is about 12ft, so it's affect is perhaps 6 times it's weight compared to the hull. Together this gives about 300 lb at 2ft from the fulcrum. When you hang on to a righting line you form a 'V' with your butt sticking out usually. the center mass is 2 to 3ft out.
So a righting weight of 280 (if you don't stick out your butt) to 320 will pull the boat up in calm winds. A righting pole (6 ft long)will work great for one guy if he walks out hand over hand on it. But here the rub, the upper hull will hit you in the head!!! (you could attach a small bag to the pole (50lb water would be enough).