Up the mast in theory.

Impaler

Impaler

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For the mathematicians, a theoretical question. If I wanted to go up my mast could I tell whether the boat would start to heel over and dump me in the oggin? Obviously it would depend on boat size, mast height and the weight of the climber. Just an idle thought really. I have a Hunter 245 with bilge keels so I'd probably dry her out before I went up. I wonder if anyone has seen someone flapping about up a mast as the boat rolls merrily to shouts of anguish from aloft.
 
A./ Multiply the weight of the climber by his height above the axis about which the boat will roll.
B./ Multiply the weight of the boat by the distance below the above axis of the centre of gravity of the boat.

When A exceeds B the boat will capsize.

It as simple as that. Levers and moments. You learnt all about those in the first year of secondary school.

Only trouble is its not that simple because the position of the axis above will change as the boat heels and so will the effective CoG of the boat.
 
Put your full weight on the halyard from the pontoon or shore, if you can pull it over then you will going up there.
 
Well...

If the mast is vertical, however heavy the bod up the mast, there is no moment, therefore no force to capsize the boat. You need a sin(theta) in there as well. That is, until the boat heels, all is well (which is why you will do it when the boat is aground). The effect when the mast is not vertical (at angle theta to vertical) is the force capsizing you further is proportional to the (mast height x weight - boat's righting moment)x sin(theta) , or Vic's (A-B)sin(theta).
 
Climb into a bosuns chair linked to a masthead halyard on your boat. Go (with permission) to a neighbour's boat a masthead distance away. Using a winch, winch down the masthead of your boat until it reaches you. Now slip off the halyard from the winch.

Now if:

(a) your boat returns upright and you go with it to the masthead. You've answered your question. And you have the benefit of doing that repair at the masthead! Don't forget the tools! /forums/images/graemlins/smile.gif

(b) your boat remains heeled over. You've answered your question. Do it ashore. /forums/images/graemlins/mad.gif

(Sorry couldn't resist it! I know it was serious question. Please don't try this)
 
There is another factor;-

Me, 21ft loa boat, top of mast to free a halyard, forgot screwdriver, shouts to wife to fetch it, she makes off halyard, steps smartly to the side deck, boat rolls alarmingly, as she reaches cockpit, steps to centre line, nicely synchronised with back swing = recipe for a pendulum.

Petrification ensues.
 
Me (12 stone) racing a 30 footer mast head rig with a fin keel, spinnaker halyard at top of mast, topping lift onto harness, ran walked wriggled up the mast and mainsail one foot on each, retrieved said halyard.

It was only after the event I even though about how much further boat heeled, but it did make my climb easier at the time.

Have been up the mast many times in the harbor, have also used the wharf and halyards around a bollard to do maintenance.

Always use an extra safety line and take a bucket with a long cord when going aloft.

Avagoodweekend......
 
I'm amazed that nobody in that thread mentioned the word Metacentre!
Basic Stability Theory.
The vessel will be unstable if the centre of gravity is above the metacentre, not the waterline or the centre of buoyancy. I've done a lot of stability calculations on crane barges and the centre of gravity is often above the waterline but they remain stable because of their high metacentres.
 
Mathematics (and mathematicians) are counter productive here. Get into bosun's chair attach to appropriate halyard & take up the slack so it takes all your weight. Swing about a bit at deck level. See how happy (or otherwise) you are about how much the boat moves. The stability of the boat will be the same as if you were at the masthead. (See the previous thread referenced /forums/images/graemlins/smile.gif )

Andy
 
That doesn't work Tillergirl. We tried it this afternoon with my mates Grandson. All we managed was to fire him across two pontoons into the stinging nettle patch over on the river bank. Still, at least his squealing made him easy to find. Back to the drawing board with your idea, I think... /forums/images/graemlins/laugh.gif
 
The boat will be a lot more stable on dry land. ie dried out.
If it is the water as you go up the stability (stiffness) of the boat decreases.
You will find that with someone moving on the deck or a passing boat will cause the mast to sway. The higher you go the more it will sway and continue to sway. (take longer to stop ) I suspect long before it is unsafe you will get the message and give up. (come down) If it is a bigger boat no problems. olewill
 
That's a good idea. I did Latin at school and was thoroughly beaten for being useless at maths and have no idea about theta beta and tangents. This will be a good project for my wife to whom I have recently been paying many compliments about her slim figure. I'll give it a bash onshore methinks.
 
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