After reading the excellent post by tkanzler I've decided I'd like to figure the loads on a planned system for my V25. The one bit of info that I'm missing is the mast weight. Anybody have that?
What is the weight of the Mast?
- Thread starter RonRock
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OK, it is a little more than the weight that I need help with. Here is a copy of the info,
Variables are as follows:
Wmast - mast weight, taken at the center of gravity
MAmast - moment arm of the mast about the hinge
MAhoist - moment arm of the mast raising hoist about the hinge
MAhalyard - moment arm of the jib halyard about the hinge
The total tension force in the hoisting system is easily calculated by summing moments about the mast hinge, and setting it equal to zero (static equilibrium).
M = 0 = Wmast*MAmast - Fhoist*MAhoist where Fhoist is the tension force in the hoisting system
I have figured MAhoist with 5,6,&7 foot poles.
But am unable to see how to get the Fhoist figure.
How is Fhoist determined?
Variables are as follows:
Wmast - mast weight, taken at the center of gravity
MAmast - moment arm of the mast about the hinge
MAhoist - moment arm of the mast raising hoist about the hinge
MAhalyard - moment arm of the jib halyard about the hinge
The total tension force in the hoisting system is easily calculated by summing moments about the mast hinge, and setting it equal to zero (static equilibrium).
M = 0 = Wmast*MAmast - Fhoist*MAhoist where Fhoist is the tension force in the hoisting system
I have figured MAhoist with 5,6,&7 foot poles.
But am unable to see how to get the Fhoist figure.
How is Fhoist determined?
Rearrange the terms to solve for Fhoist. It's basically just the weight of the mast times the horizontal distance from its CG to the hinge, divided by the perpendicular distance to the halyard (for halyard force) or the gin pole rigging (for gin pole rigging force).
Wmast*MAmast = Fhoist*MAhoist for static equilibrium.
Fhoist = Wmast*MAmast/MAhoist
To get the lengths of the moment arms at various angles without trigonometry, it's easiest to just graph on quadril paper or some other graph paper (to scale, or use a CAD program), and draw a line from the hinge to the piece of rigging in question, at 90 degrees to that rigging. Measure that perpendicular distance to get the moment arm. It changes as the mast is raised, but the worst case is usually with the mast horizontal, though not necessarily, depending on what kind of gin pole and how it's oriented.
Remember that this is static force, with no impact loading (like bouncy raising or lowering), and you must apply a generous factor of safety to all rigging and structure, as always with rigging.
Wmast*MAmast = Fhoist*MAhoist for static equilibrium.
Fhoist = Wmast*MAmast/MAhoist
To get the lengths of the moment arms at various angles without trigonometry, it's easiest to just graph on quadril paper or some other graph paper (to scale, or use a CAD program), and draw a line from the hinge to the piece of rigging in question, at 90 degrees to that rigging. Measure that perpendicular distance to get the moment arm. It changes as the mast is raised, but the worst case is usually with the mast horizontal, though not necessarily, depending on what kind of gin pole and how it's oriented.
Remember that this is static force, with no impact loading (like bouncy raising or lowering), and you must apply a generous factor of safety to all rigging and structure, as always with rigging.
Thanks, tkanzler. I went back after my last post and actually printed the drawing you posted. It was legible in the print, from my computer screen I could not make out the wording. Makes much more sense when it is readable.
So as far as mast weight, would 100 lbs be a reasonable figure? Mast length is 28 foot. I checked on Dwyer and their mast material (DM-6 3X4) is figured at 1.55 lb/ft. That makes mine 43.4 lbs. That figure seems very light. Even with hardware and cable at that figure my mast would not weigh 100 lbs.
Could that be true? Sure seems heavier than that.
So as far as mast weight, would 100 lbs be a reasonable figure? Mast length is 28 foot. I checked on Dwyer and their mast material (DM-6 3X4) is figured at 1.55 lb/ft. That makes mine 43.4 lbs. That figure seems very light. Even with hardware and cable at that figure my mast would not weigh 100 lbs.
Could that be true? Sure seems heavier than that.
Sounds ok to me, but I don't know your mast. I just used 100 lb to be on the heavy side, with roller furler and head sail, plus hardware. Probably also safe to assume the CG is lower than the midpoint of the mast, with furler and sail attached, so using the midpoint is conservative.
The mast on my 26D with just the head stay is almost equivalent (a bit lighter) to raising a 32' ladder. The mast is easier to raise because the foot is attached and hinged.
I kind of run (2 steps) and throw my 40'er down at the foot and up on the end while getting underneath and walking it up. I much prefer the mast even if I have to walk through the cockpit and climb up top. (Means I'm not at work too!)
I kind of run (2 steps) and throw my 40'er down at the foot and up on the end while getting underneath and walking it up. I much prefer the mast even if I have to walk through the cockpit and climb up top. (Means I'm not at work too!)
if you figure your mast and rigging complete, at 75lbs, you will be figuring a bit heavy, but really close. error on the safe side... but if you have a furler, it will be heavier.
mine is 24ft long made from the same material and no furler. when i set mine up with a gin pole, I figured it at about 50lbs.... because I have moved it around enough to know i can handle it easily at the balance point with one hand. yours will be a bit more, but not very much.... you are going to have around 175lbs of force on your hoist line. I have less on mine but I have an 8ft gin pole and 2ft less mast. in my opinion I would not go less than 6.5 ft on your gin pole... longer is better.
mine is 24ft long made from the same material and no furler. when i set mine up with a gin pole, I figured it at about 50lbs.... because I have moved it around enough to know i can handle it easily at the balance point with one hand. yours will be a bit more, but not very much.... you are going to have around 175lbs of force on your hoist line. I have less on mine but I have an 8ft gin pole and 2ft less mast. in my opinion I would not go less than 6.5 ft on your gin pole... longer is better.
For some reason, I'm more willing to drop the ladder...Man, I remember pushing/standing up some big ladders in my past!
I do appreciate my gin pole, nowadays.
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