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post #19 of Old 09-18-2007 Thread Starter
Join Date: Nov 2006
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RichH says,
“Sea KINDLINESS is by the design of a boat, etc.”

I agree with you but isn’t everything “by the design of the boat”. Is sea kindliness something separate and above other factors in the design? Or is just one more factor making up the overall package called seaworthy.

RichH goes on to say,
“SeaWORTHINESS is due to the inbuilt strength of the boat.”

I think seaworthiness is more then just the ultimate strength of the boat. A strong boat that can’t claw off a lee shore is not seaworthy and a boat with such a violent movement that the crew can’t sleep or work the boat is not very seaworthy.

RichH then says,
“A 'seaworthy' boat is usually built with on-purpose *redundant strength* to handle all conditions possibly encountered. A 'seaworthy' boat, a boat built to take care of itself in ALL conditions possibly encountered on a LONG voyage or ocean passage, will typically be built 5 to 6 times STRONGER than the 'design' loading. This 5 to 6 times 'stronger' than functional design is called 'factor of safety' .... and usually defines a 'blue water' boat. Historical or insurance 'scantlings' show that a boat built at FS=5 FS=6 will be capable of long passages ... without often having them pay a 'loss' claim.

Blue water boats typically have a safety factor built-in at 5X or 6X; (although a 'balls to the wall' racing effort will use/chance less safety factor to save weight, etc.)
a 'coastal design' will have ~3X safety factor;
an 'inshore' design will sometimes only have a safety factor of 2.

Once again RichH you are by yourself as far as the numbers go. I can understand your not wanting to take my word for it but why ("why" added 9-21-07) you do you dismiss the body of work in print that says you are wrong. Have you looked at any of the references I pointed out? Not that long ago you asked Bob Perry what his office uses for a safety factor. You have said in the past that you like Bob Perry’s work so why do you dismiss his direct answer to you. He said in a response to you on 8-16-05 on the CSBB forum and I quote,

“We use safety factors varying from 2.00 to 4.00. We never use more than four and we never use less than 2.00. It depends upon the boat and it's use. For our typical cruising boats of moderate displacement we go with four. For our "cruising sled" series of light cruising boats we drop the safety factor in order to help reduce weight. It's my attitude that there are components of your cruising boat you should be able to take for granted: rig, rudder and laminate schedule.”

In engineering there is a very large difference between something designed to withstand 4 times a strain and the same thing designed to withstand 6 times a strain and of course the difference between 2 and 6 is extreme. The only boat that I have seen with a safety factor larger then 4 was a 37 foot steel ketch with telephone poles for masts and ” galvanized wire for rigging. But this isn’t your typical boat by anybody’s definition. Also scantling rules come from places like the ABS, RCD, and ISO/CEN Standard 12215-5 to name just a few. Insurance companies have nothing to do with this.

RichH finishes by saying,
”Has nothing to do with the 'experience' or 'lack of experience' of the crew; although, an inexperienced crew can easily structurally destroy even a FS=6 boat in no time.”

This is very true and many boats survive after the crew abandons them. Since the beginning of offshore sailing or in fact since the beginning of boating it has been possible for an incompetent captain to drive a boat under. A skilled captain with a marginal boat will do just fine but an idiot with the best boat is in trouble.
All the best,
Robert Gainer

Last edited by Tartan34C; 09-21-2007 at 08:23 PM. Reason: Added the word “why”
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