Mac wont fall over if climbing mast

[mastreb]

You could probably pull the boat down from the dock using the gin pole winch, presuming you could bolt it to something.

[Dawgfish]

gin pole ? ill hafta look that one up, just used a strap come-a-long to lower my mast. im bettin itll work for a tilt or two.
so storms and even medium winds makes droppin sail difficult @ best, found out on an easy wind...25mph gust abeam. later i tied an additional rope to the top o th main and ran it to the base o th mast through th ring then to the cockpit, im hopin ill be able to pull it down if it wont drop on its own next time.
hope its not during a "heel clicker" though

[Dawgfish]

oops guess i sent that to the wrong discussion the storm part anyway....

[Hamin' X]

neat topic , tipping , climbin, monkeys & torque i was thinkin of swimmin around my with a brush for a quick scrub, but ya'll got me gears goin! id like to c this "tippin boat video" can anyone point me in the rite direction?

Here's a short version: http://www.youtube.com/watch?v=5jNkkz8X ... re=related

~Rich

[seacatcapt]

Going from my fully ballasted weight of 260 lbs., the lever arm length would be 4420/260=17 feet. The tipping point angle is sin-1(17/32) or 32 degrees. Beyond 32 degrees of heel, I would pull the boat down.

Find your own heel angle with this formula: sin-1(138/Y) where Y is your weight. 138 is 4420/32.

Matreb, I respectfully don't think that it is that simple. The righting torque produced by the ballast is not constant as the boat tilts. It is apparently at the value of 4420 when the boat is on held on its side per the Mac video with the supposed weight at the mast head. Clearly at 10 deg of heal, there is not 4420 ft-lbs of righting torque out of 1100 lbs of water ballast and a little lead at the daggerboard.

[Tomfoolery]

The righting torque produced by the ballast is not constant as the boat tilts.

And neither is the center of bouyancy unless the hull is semicircular. A flat-ish bottom boat like the will shift its center of bouyancy towards the low side rather rapidly with small angles of heel, thereby increasing the effective moment arm rather rapidly. That would explain why the boat is quite tender at first, then stiffens up rapidly. That, and the very high center of mass, with all of the ballast being within the confines of the hull. Unlike a keelboat, where the ballast is very low, effectively lowering the center of mass of the vessel with respect to the water surface (or instant center of rotation for a given heel angle, more accurately), and increasing the moment arm between the vessel center of mass and the center of bouyancy.



Since it would be very difficult to predict the angle at which there is no coming back, I'd rather just lower the mast. The boat is made for that, after all, and I've done it at least a half dozen times in the few short months I've owned it. Twice on the water, in my slip, so I could work on the mast head from a short ladder on the dock. No big deal.

[mastreb]

Going from my fully ballasted weight of 260 lbs., the lever arm length would be 4420/260=17 feet. The tipping point angle is sin-1(17/32) or 32 degrees. Beyond 32 degrees of heel, I would pull the boat down.

Find your own heel angle with this formula: sin-1(138/Y) where Y is your weight. 138 is 4420/32.

Matreb, I respectfully don't think that it is that simple. The righting torque produced by the ballast is not constant as the boat tilts. It is apparently at the value of 4420 when the boat is on held on its side per the Mac video with the supposed weight at the mast head. Clearly at 10 deg of heal, there is not 4420 ft-lbs of righting torque out of 1100 lbs of water ballast and a little lead at the daggerboard.

Of course not. The righting moment of the boat when vertical is 0, which is why my 50 lbs. Daughter can start it rocking. In increases from 0 to 4420-odd as the angle of heel increases and the boat tips. That's the inverse of what this forumula describes, and it's precisely why the boat increasingly want to return to upright the farther over it is tipped.

Any simple formula is of course talking about an ideal system as opposed to an actual system. There are a myriad of minor and modate forces also acting on the boat and this formula describes only a pendulous ideal lever. However, this is the force that dominates, and the values predicted by it reasonably estimate what you would measure if you actually winched the boat over. All the other forces and inaccuracies combined would be less than 10% off, the leverage is so dominant.

All mathematical formulas are simplifications--Math is the language of simplification designed to idealize the real world so that we can make predictions. You choose the degree of simplification every time you write a formula, and the simpler they are, the more factors are being ignored. The important thing is finding the simple factors that dominate so that you can quickly make decisions like "Should I climb to the top of the mast if I weight 300 lbs?" which this formula answers with a resounding "No."

[seahouse]

"Should I climb to the top of the mast if I weight 300 lbs?" which this formula answers with a resounding "No."

OK. So in the real world then. If I weigh 130 lbs should I climb to the top of the mast? What is the resounding answer to that? It's not at all resounding, but I would pick yes. (I would also be more likely to pick yes if I were doing it with someone elses' boat, though).

I'm also willing to bet that the 5 feet of extended daggerboard would effectively damp oscillations so the inertial forces would not accumulate significantly enough to play a role, particularly at the more horizontal attitudes. And a person would tend to shift his weight to counteract the oscillations, much like you did when you wanted to stop a swing when you were a kid. (OK, so I'm lying, I just jumped off).

I also think that if you pulled only from the top of the mast (such as with a block and tackle from a point 30' or so horizontally from the mast base) that you might possibly break/ permanently deform it from the point loading that it would never normally experience, and that it was not designed to take.

Love this thread. Not much "groupthink" going on now.

[LOUIS B HOLUB]

IDEA
Hows 'bout someone (weight range of 130 to 180 lbs) go ahead...climb your mast, to the top, hang on, shake your booty ... and report back with a few noteworthy comments, such as:

1. did you get wet ?
2. did you break your neck?
3. anything else of interest...(if you survive).

good idea, huh ? Any takers ?

[Phil M]

I doubt any takers on climbing the mast for discussion purposes.

Just wondering, has anyone lowered an M mast single-handed by muscle power alone? (My admiral would be safer down below.) I always have used the mast-raising system. If you were out on the water somewhere, and did not have the mast-raising system with you, that knowledge might come in handy before attempting to lower it manually.

Climbing a mast ...

Phil M

[robbarnes1965]

I doubt any takers on climbing the mast for discussion purposes.

Just wondering, has anyone lowered an M mast single-handed by muscle power alone? (My admiral would be safer down below.) I always have used the mast-raising system. If you were out on the water somewhere, and did not have the mast-raising system with you, that knowledge might come in handy before attempting to lower it manually.

Climbing a mast ...

Phil M

Even with the less weight of no furler I don't think it can be done safely (for the boat at least) with one person. With two people it is probably easy but not safe as one has to be under the mast. With the mast raising kit priced at $155, it's just not worth the risk doing without it. Virtually ANY mishap will cost more than that

[Sumner]

..Just wondering, has anyone lowered an M mast single-handed by muscle power alone? ..

Even with the less weight of no furler I don't think it can be done safely (for the boat at least) with one person. With two people it is probably easy but not safe as one has to be under the mast. With the mast raising kit priced at $155, it's just not worth the risk doing without it. Virtually ANY mishap will cost more than that

We lowered our mast once on our S on the water since someone was coming to get us with the Suburban/trailer and they wouldn't be there until after dark...



http://purplesagetradingpost.com/sumner ... ll-09.html

...It was easy, but we always have the mast raising/lowering gin pole and bock and tackle with us on the boat. I also strongly agree about "it's just not worth the risk" part. I put the mast up and down by hand a couple times on the trailer, but one slip and the damage to you and/or the boat isn't going to be pretty.

I like the newer systems with the winch on the gin pole, but won't go to that as the older system takes up less space I feel and stores easier. Also the block and tackle could be put to other uses if needed,

Sum

Our Endeavour 37

Our Trips to Utah, Idaho, Canada, Florida

Our MacGregor S Pages

Mac-Venture Links

[Tomfoolery]

I keep mine (old style) below the cockpit for just such an emergency. It takes up very little room, and that space is just storage for me anyway, but even if it wasn't, there's still lots of extra room back there even with two people sleeping in it. I used to put my 23 ft Aquarius mast up myself, but that's about the limit for me, and I'm not getting any younger. With the furler and genoa on my , it would be tough with two people, and my usual crew is my FIL, who's pushing 80. I also pull extra hard at the top to make the headstay connection, which would be tough without the gin pole.

But I don't ever stand under the mast when the headstay is not pinned to the bow fitting. Some of the hardware used is a bit light for my taste, especially where it connects to the cabin roof. I don't know what's backing it up, and I don't plan on having a mast take me out should it prove inadequate. But that (not standing under) is SOP for lifted loads anyway.

“Give me a place to stand and a lever long enough and I will move the world”

Archimedes, 220 BC