Righting Bag Test

Nice shots. Looks like the water (and air?) is still a bit on the cool side. It should be warmer there than where I spent many years- Whidbey Is.

_________________
Alan
'86 H16, Sail #89057

Eric,
If you are still watching this, can you post the dimensions of your bag? I need to make one too this off season, and I thought I could avoid re-inventing the bag. Thanks for such a great post.

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

Alfred...
I'll have to look in my notes to find the construction dimensions. I'll provide them one way or another.

Thanks,
-Eric

_________________
Eric
H16
Sail# 11500

i like the new ideas building a new bag. but just a new idea, not sure if it'll work, would putting a 5 pound lead bag in the bag help keep the bag from loosing water? so the bag will sit upright and when you pull it up to raise it the lip won't loose water?

i have a bag myself and havent had an oppurtunity to try it all out yet

The five pound weight idea doesn't address the cause of the original design flaw. Let me explain: Think of an Isosceles triangle. The top of the triangle represents the connection point of the four lines to the pulley line. The bottom of the triangle represents the base of the righting bag.

Imagine the lines connecting the top lip of the bag to the connection point. The radius is outside of the adjacent long legs of the triangle. When the bag (or triangle) is full of water and lifted, the lines-of-stress extend from the connection point directly to the base. Since the radius of the lip is outside the lines-of-stress, the unreinforced lip will collapse toward the long leg of the triangle. The reduction in the volume of the bag is what causes the loss of (ballast) water. The lip needs to resist being pulled in, which is why I added the circular stiffener.

I think adding a weight to the bottom of the bag would only cause an earlier collapse of the lip.

Hope this clarifies,

_________________
Eric
H16
Sail# 11500

Bag height = 21", Diameter = 15"

Cheers,
-Eric

_________________
Eric
H16
Sail# 11500

ive always wondered about this. Why dont we use the mast at all to right the boat. The first time i ever capsized i couldnt get the boat back up and was left out in the water high and dry for over 2 hours. granted these 2hours were spent thinking of alternative ways to right the boat. I trieed to swim up the the top of the mast and tie a line to the mast tang where the jib and all rigging connects. unfortunately my rope wasnt long enough and i threw that idea away. But i have been thinking about it ever since


Wouldnt tying a line to the mast tang or the very top of the mast, throwing it over the hull in the air, and leaning back off that line, be the smarter way to get your boat up? Since thats where all the weight is thats keeping you capsized. It would give you 100x more levarage than using the hulls to right the boat.

Anyone have any ideas about this

_________________
1971 H16 (sail #1768)

To all of you on the Hobie Forum... I love you guys!!!
thanks for all the help!

There is a pole righting system you can purchase that gives you more leverage, but the bag and the normal way to right it seems to be the quickest and most efficient.

_________________
1992 Hobie Cat 18 #16943
Hobie Fleet 198, Rapid City, SD

It doesn't matter where you tie a line, if it draps over the upper hull then to your hands or shoulder that provides the same amount of leverage as if the rope were tied to a pylon! You get no better leverage until is off and away from the hull- by that time the boat is on its way upright anyway. It is mechanics- you can't get something for nothing.

The two choices are (1)better geometry- better location of the line and pressure point, away from the upper hull (better angle of the dangle) which is possible with a righting pole, etc. or (2) better Newtons- more weight like from a righting bag.

Those are your ONLY options.

_________________
Alan
'86 H16, Sail #89057

see that just doesnt do it for me.

Yes it may be too much stress on the mast for it to be a good option so i guess thats a good enough answer for me.
(((But i think that is debatable too. That little tang is under huge amounts of stress while under sail. its basically has the whole load of the mast plus all the energy from the main and jib sail pulling on it. That little tang basically holds the whole boat together in a way)))

But you saying that you wouldnt get any levarage doesnt sit with me. Of course it would give you more levarage. That is why powerboaters lift the top of our masts when we cant get the boat righted ourselves. Thats also why you have to have someone lift the mast a little when your stepping the mast on the beach. To give you that extra little bit of levarage. Simple physics

Heres a simple pic of what i am imagining in my brain:

if that pic isnt showing heres a link to the image
http://i32.photobucket.com/albums/d22/s ... ghting.jpg

_________________
1971 H16 (sail #1768)

To all of you on the Hobie Forum... I love you guys!!!
thanks for all the help!

you forgot about the side stays... they act as your rope.

You either have to increase the Force (more weight, like the bag) or increase the distance.

_________________
1992 Hobie Cat 18 #16943
Hobie Fleet 198, Rapid City, SD

You got it right Tom. The moment force or as you describe torque is the rotational force required to lift the mast. This rotational force is around the pivot point and is the hull in the water. Therefore, the force is applied to the point at the upper hull.
Generally speaking....If you assume the mast is 85 pounds and 28' long, the rotational force of the mast is 14'x85=1190 pounds that needs to be counteracted by your body, crew and water bag. If we assume your shoulder height (or distance from the boat of 5') and you weigh 170 pounds, your weight would have a rotational force of 2.5'X170=425 pounds and your water bag would have a rotational force of 5'x150=750 pounds. Therefore, these combined forces of 425+750=1200 ponds is greater than the mast force of 1190 ponds and you will slowly lift the boat. Any way to move the weight out away from the boat farther will create the most force. Thats why the closer your body gets to horizontal or closest to the water the more your body weight is rotated by a larger distance.

ok ok.. i guess i was wrong

so the levarage is actually coming from how much weight and how far you get that weight out from the side of the boat your standing on when capsized? (in the picture: how much weight and how far your getting out from the left side of the boat)

_________________
1971 H16 (sail #1768)

To all of you on the Hobie Forum... I love you guys!!!
thanks for all the help!

Yup! The optimum application of force for righting is as far away from the point of rotation as you can get and tangential to a line from the point of rotation. When you attach a line to the pylon, unless you are really really tall, the righting force force falls inside the circle- not the best geometry. I think the bigger righting bags hold between 60-70 lbs of water.

_________________
Alan
'86 H16, Sail #89057

is equal to:
2.15 Cubic ft (ft)^3
16.06 Gallons

Water is 8.345404lbs per Gallon

so... total bag weight when full should be 134.027lbs.

_________________
1992 Hobie Cat 18 #16943
Hobie Fleet 198, Rapid City, SD