Talk about a rough day!
- Thread starter Bad Obsession
- Start date
- Status
I saw that last year.
Looks like some miscommunication between the captain and the bridge there.
Looks like some miscommunication between the captain and the bridge there.
Deck/keel step and can a sail make a mast stronger
Norman L. Skene said “…the capacity of the yacht engineer is nowhere more clearly indicated then in proportioning the various elements of the rig … Nothing will take the place of a thorough knowledge of the strength of materials and of the methods of determining stresses.” But L. Francis Herreshoff said “The best way to learn about spars is to study successful ones and forget about mathematics; for the spar, old as it may be, has developed mostly by trail and failure, and if there is any place in the whole design of a yacht where common sense is more useful then mathematics it is in the design of spars”. Confusing isn’t it when two great designers can’t agree and how a mast should be designed. This morning I read here on this forum that a deck-stepped mast is stronger then a keel-stepped mast if everything else is the same. This is contrary to what I understood so I looked it up in my trusty and well used copy of the eighth edition (1973) of Skene’s Elements of Yacht Design by Francis S. Kinney. And believe it or not on page 168 he discuses the differences among columns having pin ends and fixed ends. He makes it clear that a keel-stepped mast is considered to have a fixed end and is stronger then a deck-stepped mast with its pin end on deck. Because the opposite was stated on this forum I decided to take no chances and also looked at the fifth edition (1935) of Elements of Yacht Design by Norman L. Skene. After all Kinney might be just repeating the same old mistakes from the original book by Skene. And yes on page 118 he says the same thing about pin ends, fixed ends and Euler’s formula. Knowing that this might be just a mistake that has been repeated time and time again by both Skene and Kinney since the first edition of Elements of Yacht Design was published in 1927 I decided to look further. I next looked at a paper presented before the 71 Annual Meeting of the Society of Naval Architects and Marine Engineers in New York, NY. The paper, with the title Sailing Yacht Design; An Appreciation of a Fine Art, was written by Henry and Miller and was presented as a statement of what was the then current state of the art for design. And yes this paper also uses Euler’s formula as the basic building block for the design of the mast. And it gives the same information about deck and keel stepped masts. Then I looked at the work by Larsson and Eliasson, Principles of Yacht Design third edition. This is today’s definitive work on yacht design and has a more rigorous approach to engineering. And there it is on page 227, the formula, which at first glance looks like Euler’s with some refinements but it has the same factors to account for the difference between deck and keel stepped mast and a sidebar describing the added stiffness of a keel-stepped spar and the advantages you can have if you design a smaller section (because of the added stiffness of the keel stepped spar) such as less windage and decreased weight aloft. After a quick glance at 8 other books I am convinced that a keel-stepped mast is stiffer and stronger then a deck stepped one if all other factors are the same. Does a sail ever contribute to the strength or stiffness of a mast? It never makes a mast stronger but having a main up under some conditions with some arrangements of shrouds will improve the masts stiffness. And anything that keeps a mast in column will make a mast stronger so if you stretch English a bit you can say a mainsail can make a mast stronger. I think that’s tortured thinking but you can make a case for it. It’s your choice. All the best, Robert Gainer
Norman L. Skene said “…the capacity of the yacht engineer is nowhere more clearly indicated then in proportioning the various elements of the rig … Nothing will take the place of a thorough knowledge of the strength of materials and of the methods of determining stresses.” But L. Francis Herreshoff said “The best way to learn about spars is to study successful ones and forget about mathematics; for the spar, old as it may be, has developed mostly by trail and failure, and if there is any place in the whole design of a yacht where common sense is more useful then mathematics it is in the design of spars”. Confusing isn’t it when two great designers can’t agree and how a mast should be designed. This morning I read here on this forum that a deck-stepped mast is stronger then a keel-stepped mast if everything else is the same. This is contrary to what I understood so I looked it up in my trusty and well used copy of the eighth edition (1973) of Skene’s Elements of Yacht Design by Francis S. Kinney. And believe it or not on page 168 he discuses the differences among columns having pin ends and fixed ends. He makes it clear that a keel-stepped mast is considered to have a fixed end and is stronger then a deck-stepped mast with its pin end on deck. Because the opposite was stated on this forum I decided to take no chances and also looked at the fifth edition (1935) of Elements of Yacht Design by Norman L. Skene. After all Kinney might be just repeating the same old mistakes from the original book by Skene. And yes on page 118 he says the same thing about pin ends, fixed ends and Euler’s formula. Knowing that this might be just a mistake that has been repeated time and time again by both Skene and Kinney since the first edition of Elements of Yacht Design was published in 1927 I decided to look further. I next looked at a paper presented before the 71 Annual Meeting of the Society of Naval Architects and Marine Engineers in New York, NY. The paper, with the title Sailing Yacht Design; An Appreciation of a Fine Art, was written by Henry and Miller and was presented as a statement of what was the then current state of the art for design. And yes this paper also uses Euler’s formula as the basic building block for the design of the mast. And it gives the same information about deck and keel stepped masts. Then I looked at the work by Larsson and Eliasson, Principles of Yacht Design third edition. This is today’s definitive work on yacht design and has a more rigorous approach to engineering. And there it is on page 227, the formula, which at first glance looks like Euler’s with some refinements but it has the same factors to account for the difference between deck and keel stepped mast and a sidebar describing the added stiffness of a keel-stepped spar and the advantages you can have if you design a smaller section (because of the added stiffness of the keel stepped spar) such as less windage and decreased weight aloft. After a quick glance at 8 other books I am convinced that a keel-stepped mast is stiffer and stronger then a deck stepped one if all other factors are the same. Does a sail ever contribute to the strength or stiffness of a mast? It never makes a mast stronger but having a main up under some conditions with some arrangements of shrouds will improve the masts stiffness. And anything that keeps a mast in column will make a mast stronger so if you stretch English a bit you can say a mainsail can make a mast stronger. I think that’s tortured thinking but you can make a case for it. It’s your choice. All the best, Robert Gainer
Elementary, my dear Watson!
Mr. Gainer you are quite through, have no 'agenda' other than a serach for the truth, and a definite asset to this forum. Methinks anyone with experience knows intuitively which mast support system is the stronger.A tabernacle mast has its obvious advantage, but I have been dismasted on three separate adventures, so am partial to a keel-stepped mast. True, you end up with a rather large opening into your craft, but that can be quickly plugged with rags to lesson the flow.A keel-stepped mast has the advantage of being a straight-forward job whence dismasted; you already have the hole in cement to place you 'fencepost' for jury rigging. Two of my dismatings were deck-stepped third was keel-stepped.I always choose a boat with a keel-stepped mast for ocean work, but do not have a choice when woking a delivery job. As far as storms go, and I have said this before too, keep it simple watch the glass ALWAYS.Check the weather via ssb always, and have a plan worked out well before hand. If you are going to cruise, you WILL get nailed by gales, maybe not a full STORM, but gales for sure. Read 'Fatnet 79' by John Rousmainere (sic) out of over THREE HUNDRED yachts that were abandoned it their own devices in hurricaine force winds, btw a really STUPID tactic especially for experienced seamen, only one I believe sank.The others, not full-keelers, but racing craft, were fine with NO ONE ABOARD to guide them! What does this tell us? Hoving to is fine for a blow but not a storm. Active storm tactics are okay for racing crew, like Robin-Knotts-Johnson, and Peter Blake on the EnZa.Not for a 'normal' cruiser who is not out for world records or just wants to survive. When hit with a gale, NOT a squall line, do you know it will only get up to 50 knots wind, with 20 ft seas overnight then quit? NO! you don't, cannot even tell that from the glass or weather reports for sure. I have tried everything in the book. "Passive" tactics are best.Many injurys occur when attempting to 'fight' with a storm and run off, tow a warp or "hove to" (a silly taktic in a real storm) but lie to a sea-anchor (a series drogue is the best nowadays, a great invention) off the bow, 50 degrees from the confused sea.Have all nailed as best you can EARLY before the storm arrives. get down below, batten hatches and lie down with mattresses round you. If you do this in an ordinary gale, what I started doing (gitting a few 'extra' miles is neglegable compared to the injury you can suffer) where's the harm, and it oculd develope into a full-blown-STORM!So, you are as ready as you can be, and this is the final postition all the hot-shot idiots that wate their time trying to 'fight' the storm witll end up in anyway. True, if you find yourself off a lee shore you will need to off, but you should of had sea room shouldn't you?+ knowing the weather you would be further off or safe in a port before getting nailed too. Be prepared if you are going cruising, the only help you can reasonably expect is from yourself.Don't think for a secon that you can circumvent all weather, even ships that can maintain 25 knots cannot do it, so you can? I haven't been here much as I have been working the oil-spill in the bay for the ships insurance carrier, carry on mates...;-)
Mr. Gainer you are quite through, have no 'agenda' other than a serach for the truth, and a definite asset to this forum. Methinks anyone with experience knows intuitively which mast support system is the stronger.A tabernacle mast has its obvious advantage, but I have been dismasted on three separate adventures, so am partial to a keel-stepped mast. True, you end up with a rather large opening into your craft, but that can be quickly plugged with rags to lesson the flow.A keel-stepped mast has the advantage of being a straight-forward job whence dismasted; you already have the hole in cement to place you 'fencepost' for jury rigging. Two of my dismatings were deck-stepped third was keel-stepped.I always choose a boat with a keel-stepped mast for ocean work, but do not have a choice when woking a delivery job. As far as storms go, and I have said this before too, keep it simple watch the glass ALWAYS.Check the weather via ssb always, and have a plan worked out well before hand. If you are going to cruise, you WILL get nailed by gales, maybe not a full STORM, but gales for sure. Read 'Fatnet 79' by John Rousmainere (sic) out of over THREE HUNDRED yachts that were abandoned it their own devices in hurricaine force winds, btw a really STUPID tactic especially for experienced seamen, only one I believe sank.The others, not full-keelers, but racing craft, were fine with NO ONE ABOARD to guide them! What does this tell us? Hoving to is fine for a blow but not a storm. Active storm tactics are okay for racing crew, like Robin-Knotts-Johnson, and Peter Blake on the EnZa.Not for a 'normal' cruiser who is not out for world records or just wants to survive. When hit with a gale, NOT a squall line, do you know it will only get up to 50 knots wind, with 20 ft seas overnight then quit? NO! you don't, cannot even tell that from the glass or weather reports for sure. I have tried everything in the book. "Passive" tactics are best.Many injurys occur when attempting to 'fight' with a storm and run off, tow a warp or "hove to" (a silly taktic in a real storm) but lie to a sea-anchor (a series drogue is the best nowadays, a great invention) off the bow, 50 degrees from the confused sea.Have all nailed as best you can EARLY before the storm arrives. get down below, batten hatches and lie down with mattresses round you. If you do this in an ordinary gale, what I started doing (gitting a few 'extra' miles is neglegable compared to the injury you can suffer) where's the harm, and it oculd develope into a full-blown-STORM!So, you are as ready as you can be, and this is the final postition all the hot-shot idiots that wate their time trying to 'fight' the storm witll end up in anyway. True, if you find yourself off a lee shore you will need to off, but you should of had sea room shouldn't you?+ knowing the weather you would be further off or safe in a port before getting nailed too. Be prepared if you are going cruising, the only help you can reasonably expect is from yourself.Don't think for a secon that you can circumvent all weather, even ships that can maintain 25 knots cannot do it, so you can? I haven't been here much as I have been working the oil-spill in the bay for the ships insurance carrier, carry on mates...;-)
Stu, I mean sailing with the jib alone.
I think I may have made up the word. Is jibbing the right word or is there another word for it? I not sure is decked stepped or keel stepped is stonger. I am sure that depends more of the boats construction specs then how the mast is stepped. I do think that a keel stepped mast would survive a single point of failure better than deck stepped.
I think I may have made up the word. Is jibbing the right word or is there another word for it? I not sure is decked stepped or keel stepped is stonger. I am sure that depends more of the boats construction specs then how the mast is stepped. I do think that a keel stepped mast would survive a single point of failure better than deck stepped.
- Status