Olivier's story excited a lot of comment, including several that a 27 foot boat is "too risky" for an ocean crossing. I see surviving at sea in two parts - seamanship, and boat handling when upright in the wind, and - boat survivability if it is rolled by a breaking wave. The first deals with seamanship, rigging set-up, strength and redundancy, reefing, storm sails, drogues, hatch/hull strength against blue water, ability to shed water, and protection/comfort of the crew. The only place length enters this equation is comfort. But the h27 has 19 percent overhangs (LOA/LWL-1) to offset its short length. Olivier's seamanship, North Sea experience, and willingness to take advice convince me he will be ready on the rest of these issues. Surviving a roll requires a hull design that will get you back upright quickly, a waterproof cabin (with an emphasis on latching down the companionway hatch-boards), proper stowage, and rig strength to keep the stick up underwater. Waterproofing, stowage, and rig strength/redundancy can be assured by modifications and have nothing to do with length. But the length is a key variable in stability of the hull design. A recent article in Yachting World rightly focused on the stability curve of the design. At what angle does the hull lose positive righting moment? (120 is good) What is the area under the curve where stability is negative and the hull will tend to stay inverted until another wave rolls it to a positive righting moment? I have not seen stability curve for the '75-'83 h27, but the hull shape (rounded shape of the decks and high cabin roof) does suggest good performance on this issue. We can look at the capsize screen numbers to get an idea of how length affects stability (in the abscence of stability curves.) The h27 has a capsize screen of 1.93 (less than 2.00 is considered suitable for ocean cruising.) I surveyed the modern Hunter offer (designated by 3 digits in the model list on this site.) The shortest hull in this category with a capsize screen below 2,00 is the 430 at 1.94. You have to go to the 450 to get a better number than the h27 at 1.89. Based on capsize screen, the Cherubini design of the h27 is equivalent to the modern 430 for seaworthiness in a roll. For our friends who are circling the glode, or cruising the South Pacific in modern hunters, I am _not_ saying that these boats are not blue water worthy. And I think the modern designs are excellent for the coastal cruising, and less than gale winds for which they are designed. But I am saying that a properly prepared and strengthened Cherubini h27 shows every promise of handling blue water as well as much longer modern boats. So it is design, not length that is the critical variable - as we know from the many successful roundings in 27 to 30 foot boats. A final word. A 40 foot boat presents significant issues in quickly handling the much more powerful sails and rig they carry - a major issue in the seamanship category. David Lady Lillie '77 h27
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Fascinating stuff. What about a 37?
David, That is really very interesting information, and valuable to know for anyone planning to take on serious cruising. Can you share how to calculate the "capsize screen" for a H37c, or better yet, perhaps you know what it is since I am moderately math challenged. But I am curious how my boat would rate in this sort of scale, as it seems an interesting indicator of the survivability of a partcular hull/boat design. The seamanship, we'd probably agree, is up to us to develop and practice. Thanks again, Sanders s/v Good News
David, That is really very interesting information, and valuable to know for anyone planning to take on serious cruising. Can you share how to calculate the "capsize screen" for a H37c, or better yet, perhaps you know what it is since I am moderately math challenged. But I am curious how my boat would rate in this sort of scale, as it seems an interesting indicator of the survivability of a partcular hull/boat design. The seamanship, we'd probably agree, is up to us to develop and practice. Thanks again, Sanders s/v Good News
Some light reading.
OK, if you are "math challenged" Sanders it might be considered moderately heavy reading. See the Related Link where our H37Cs make John's list of acceptable ocean cruisers under $100K. On the web-site there is lots of good discussion, click on "Technical Articles". At the bottom of that list is a link to "Best under $100K". That is a good read as he explains how he arrives at his list. The capsize screens of both the H37Cs, shoal and full keel, are under the magical 2.0 value.
OK, if you are "math challenged" Sanders it might be considered moderately heavy reading. See the Related Link where our H37Cs make John's list of acceptable ocean cruisers under $100K. On the web-site there is lots of good discussion, click on "Technical Articles". At the bottom of that list is a link to "Best under $100K". That is a good read as he explains how he arrives at his list. The capsize screens of both the H37Cs, shoal and full keel, are under the magical 2.0 value.
37c is 1.81
and, as Ed says, clearly blue water capable if modified and sailed to meet the other requirements. The only Hunter model with a better capsize screen is the 54. That hull was designed by Cherubini, and has a beam less than your 37c! Here are some other blue water rated hulls to compare with your 37c (source is Choosing a Cruising Sailboat by Roger Marshall.) 37c 1.81 Island Packet 37 1.84 Cabo Rico 38 1.67 Island Packet advertises their stability curve. It's almost all positive - that is, the hull shape is close to a cylinder, and the decks do little to hold the boat inverted if it ever got there in a roll. Read Ed's review, and archive modification discussions to get an idea of the mods he is doing to get ready for blue water. David Lady Lillie - Capsize screen 1.93
and, as Ed says, clearly blue water capable if modified and sailed to meet the other requirements. The only Hunter model with a better capsize screen is the 54. That hull was designed by Cherubini, and has a beam less than your 37c! Here are some other blue water rated hulls to compare with your 37c (source is Choosing a Cruising Sailboat by Roger Marshall.) 37c 1.81 Island Packet 37 1.84 Cabo Rico 38 1.67 Island Packet advertises their stability curve. It's almost all positive - that is, the hull shape is close to a cylinder, and the decks do little to hold the boat inverted if it ever got there in a roll. Read Ed's review, and archive modification discussions to get an idea of the mods he is doing to get ready for blue water. David Lady Lillie - Capsize screen 1.93
Cherubini Capsize Screen numbers
David, Site lists 37C at 1.91 rather than 1.81. Just for comparison H33 is 1.85, H30 is 1.90, H36 is 1.86, H54 is 1.67.
David, Site lists 37C at 1.91 rather than 1.81. Just for comparison H33 is 1.85, H30 is 1.90, H36 is 1.86, H54 is 1.67.
37c Capsize Screen Error
The formula for the capsize screen is: =Beam/(Displacement/64)^(1/3) which yields 1.81 for the 37c. I'll input the correction today. David Lady Lillie
The formula for the capsize screen is: =Beam/(Displacement/64)^(1/3) which yields 1.81 for the 37c. I'll input the correction today. David Lady Lillie
Capsize screen
The link is an informative exchange between John Rousmaniere and Don Casey concerning the capsize screen formula and its limitations. The exchange points out that the index formula doesn't get directly at the stability issue which is the real interest....but it is easy to calculate and useful. I calculated the H37c posted on the site and agree with David Foster that it seems to be calculated in error with 1.81 being the right answer for a displacement of 17800 and a beam of 11.83 feet.
The link is an informative exchange between John Rousmaniere and Don Casey concerning the capsize screen formula and its limitations. The exchange points out that the index formula doesn't get directly at the stability issue which is the real interest....but it is easy to calculate and useful. I calculated the H37c posted on the site and agree with David Foster that it seems to be calculated in error with 1.81 being the right answer for a displacement of 17800 and a beam of 11.83 feet.
Give me a 40
... with lots of beam. Mathematical formulas are great, even the widely criticized capsize screen formula. Or, we could remember that every single person who died in the 1979 Fastnet race was on a boat under 40 feet in length. Maybe that was just a coincidence.
... with lots of beam. Mathematical formulas are great, even the widely criticized capsize screen formula. Or, we could remember that every single person who died in the 1979 Fastnet race was on a boat under 40 feet in length. Maybe that was just a coincidence.
Also easy to calculate = Gullibility Index
For those who believe in easy formulas here is another one: GI (Gullibility Index) = $$/5 x 1/D x (1.Y) (where: $$ is price paid for boat in US $$; D is displacement in lbs; and Y is age of boat in years). If your GI is >2 your personal finances are likely to capsize before your boat does. Just kidding, of course. However, if you have just found out that your Capsize Screening Formula is >2 and are very worried about that you may want to hoist a 1000 lb weight to the top of the mast and then recalculate the CSF. You will be pleasantly surprised!! (Warning: before doing so double up on your dock lines or you may be have to do this calculation upside down). Have fun!! Flying Dutchman
For those who believe in easy formulas here is another one: GI (Gullibility Index) = $$/5 x 1/D x (1.Y) (where: $$ is price paid for boat in US $$; D is displacement in lbs; and Y is age of boat in years). If your GI is >2 your personal finances are likely to capsize before your boat does. Just kidding, of course. However, if you have just found out that your Capsize Screening Formula is >2 and are very worried about that you may want to hoist a 1000 lb weight to the top of the mast and then recalculate the CSF. You will be pleasantly surprised!! (Warning: before doing so double up on your dock lines or you may be have to do this calculation upside down). Have fun!! Flying Dutchman
numbers are great but
Very interesting and info to help evaluate your boat and against other, but not shore if I would be think my boat is better when chasing third significant figure as your best number only has two. Bottom line, great info but as mentioned so in the weather forecast, seamship and knowing your boats overall capabilities. I guess I will not see you out in the deep bue with my boat having a CS of 2.153177203
. Great discussion.
Very interesting and info to help evaluate your boat and against other, but not shore if I would be think my boat is better when chasing third significant figure as your best number only has two. Bottom line, great info but as mentioned so in the weather forecast, seamship and knowing your boats overall capabilities. I guess I will not see you out in the deep bue with my boat having a CS of 2.153177203
. Great discussion.- Status