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Heavy displacement vs Medium Displacement for Ocean Passages
"Bart" wrote in message ... Are boats like the Tayana 37 still popular and still a good choice for ocean crossings? When comparing open ocean vessels, Is the performace between a heavy and mid displacment boat really all that much different? If not, then maybe I wouldn't get bored with a lower performance heavy displacment vessel. I'm not sure about this and would like comments. In passagemaking, I don't see the moderate displacement boats burning up the miles significantly faster than the heavy displacement ones. I do think that you need to have adequate sail area to make a decent passage, but when you're cruising, trying to keep the boat speed up over about 1.2 sqrt WL is just too much trouble. As long as you are powered up, then waterline length is going to govern. Most heavy displacement boats have bow sprits. If a boat has a 5' bowsprit, do you add that into the total length of the boat when computing moorage charges? It would be ashame to get charged for 42' when the boat is only has 37' on deck and 37' of living space. Different policies in different places - permanent moorage usually charges LOA. I know a guy who cruises on a boat with bowsprit and when he goes for guest moorage, if they don't ask he'll tell them the LOD. He can save a few bucks that way. |
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Heavy displacement vs Medium Displacement for Ocean Passages
Matt/Meribeth Pedersen wrote: In passagemaking, I don't see the moderate displacement boats burning up the miles significantly faster than the heavy displacement ones. I do think that you need to have adequate sail area to make a decent passage, but when you're cruising, trying to keep the boat speed up over about 1.2 sqrt WL is just too much trouble. As long as you are powered up, then waterline length is going to govern. Half a knot to a knot means a lot on a passage. That is 12 to 24 miles a day which adds up pretty nicely on a 5 or 6 day run. Most of the time you are not going to be driving at hull speed so a boat that can easily be driven in light winds has a definite advantage. OTOH, the quicker motion of the medium displacement boat can get a bit tiring. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
#3
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Heavy displacement vs Medium Displacement for Ocean Passages
On Mon, 10 May 2004 10:15:17 -0400, Glenn Ashmore
wrote: OTOH, the quicker motion of the medium displacement boat can get a bit tiring. =========================================== More than a bit in my experience. A quick motion is a bad thing, and a quick squirrelly motion is absolutely the pits. There is really no substitute for length and displacement for a half way comfortable ride. |
#4
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Heavy displacement vs Medium Displacement for Ocean Passages
Glenn Ashmore wrote
Matt/Meribeth Pedersen wrote: In passagemaking, I don't see the moderate displacement boats burning up the miles significantly faster than the heavy displacement ones. I do think that you need to have adequate sail area to make a decent passage, but when you're cruising, trying to keep the boat speed up over about 1.2 sqrt WL is just too much trouble. As long as you are powered up, then waterline length is going to govern. Half a knot to a knot means a lot on a passage. That is 12 to 24 miles a day which adds up pretty nicely on a 5 or 6 day run. Most of the time you are not going to be driving at hull speed so a boat that can easily be driven in light winds has a definite advantage. OTOH, the quicker motion of the medium displacement boat can get a bit tiring. I have spent the last three years cruising the Pacific in my 42 foot medium displacement catamaran and I have observed the cruising fleet closly. A speed to length ratio of 1.2 is very fast for passages outside of the trades (eg. the islands to New Zealand). Most couples sail and motor their boats to an S/L of about 0.8 over time, but many are slower and few are much faster. Heavier boats are typically motored more often and at higher speeds than lighter ones, so the daily runs are similar. Some couples who don't like sailing as such and aren't very advanced sailors love long term cruising and some very good sailors don't. Most cruising is done at anchor anyway. It's hard to know what kind of boat will meet your needs best before you get into the life style, and, given all the boat modification that I see in New Zealand, I'd guess that most folks don't guess exactly right. I think a cruising boat should at the very least have a dry, warm place to stand watch and the ability to make ground to weather in 20-25 knots of wind without beating the crew up very much. However, given the right attitude and a bit of good luck, most any boat will get you where you want to go. BTW, motion in a seaway is largely a function of a small waterplane area to displacment. Multihulls, with their narrow hulls, can make comfortable sea boats even at light displacements. Cheers, -- Tom. |
#5
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Heavy displacement vs Medium Displacement for Ocean Passages
What is the 'speed to length ratio"? Are you referring to square root of the
waterline? Paul www.jcruiser.org "Tom Webb" wrote in message om... Glenn Ashmore wrote Matt/Meribeth Pedersen wrote: In passagemaking, I don't see the moderate displacement boats burning up the miles significantly faster than the heavy displacement ones. I do think that you need to have adequate sail area to make a decent passage, but when you're cruising, trying to keep the boat speed up over about 1.2 sqrt WL is just too much trouble. As long as you are powered up, then waterline length is going to govern. Half a knot to a knot means a lot on a passage. That is 12 to 24 miles a day which adds up pretty nicely on a 5 or 6 day run. Most of the time you are not going to be driving at hull speed so a boat that can easily be driven in light winds has a definite advantage. OTOH, the quicker motion of the medium displacement boat can get a bit tiring. I have spent the last three years cruising the Pacific in my 42 foot medium displacement catamaran and I have observed the cruising fleet closly. A speed to length ratio of 1.2 is very fast for passages outside of the trades (eg. the islands to New Zealand). Most couples sail and motor their boats to an S/L of about 0.8 over time, but many are slower and few are much faster. Heavier boats are typically motored more often and at higher speeds than lighter ones, so the daily runs are similar. Some couples who don't like sailing as such and aren't very advanced sailors love long term cruising and some very good sailors don't. Most cruising is done at anchor anyway. It's hard to know what kind of boat will meet your needs best before you get into the life style, and, given all the boat modification that I see in New Zealand, I'd guess that most folks don't guess exactly right. I think a cruising boat should at the very least have a dry, warm place to stand watch and the ability to make ground to weather in 20-25 knots of wind without beating the crew up very much. However, given the right attitude and a bit of good luck, most any boat will get you where you want to go. BTW, motion in a seaway is largely a function of a small waterplane area to displacment. Multihulls, with their narrow hulls, can make comfortable sea boats even at light displacements. Cheers, -- Tom. |
#6
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Heavy displacement vs Medium Displacement for Ocean Passages
"Paul L" wrote in message ...
What is the 'speed to length ratio"? Are you referring to square root of the waterline? Paul Yes, the speed to length ratio is the speed of the boat divided by the square root of it's sailing length. The units are feet and knots. The ratio gives a feel for how fast a boat is when corrected for length. A speed to length ratio of 1.34 is the speed of the wave that has a length equal to the sailing length of the boat and is called the "hull speed". Hull speed is a topic that has been discussed to death on this board in the past, but you could google it if you really want to know. Anyway, the speed/length ratio comes out in weird units (feet per radical knots) so it has been replaced by the Froude number in most new work... Cheers, -- Tom |
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