SailNet Community banner
  • SailNet is a forum community dedicated to Sailing enthusiasts. Come join the discussion about sailing, modifications, classifieds, troubleshooting, repairs, reviews, maintenance, and more!

Loads & Forces on a Sailboat

5K views 6 replies 6 participants last post by  sailingdog 
#1 ·
As I gradually replace all the gear on my sailboat, I've come across a consistent problem. Rope, winches, blocks, anchor chain, cleats, etc. are often rated with a "safe working load." Great to know, but this information is useless unless I know what kind of load these components will be under once installed on my boat. Right now I'm clueless as to how strong something like my headsail halyard needs to be, or what kind of load my winches will encounter. I just take peoples advice on what I need, but this is inconsistent and I'd like to know more. Any thoughts? Anybody know a website or book that gives a way to figure out what kind of loads & forces are happening on my boat so I can more accurately buy gear?
 
#2 ·
The tensile strength of ropes used on a boat are much more h'gher than the loads. 12.5 mm rope has a tensile stregth of at least 10.000 lbs. This value can decrease as much as 50% depend'ng on the knot used. The expected load on any corner of a sail is not more than 2000 lbs. This means you have at least a safety factor of two including knotting.

The main factor for rope diameter is the handling properties. A thin ropewill be difficult to handle.
 
#3 ·
The expected load on any corner of a sail is not more than 2000 lbs.
That's not true. It depends on the size of the sail. Open 70's have sheet loads that are over 15k lbs. There are ways to calculate the loads on various sheets and halyards. IIRC Harken has some calculation formulas in their catalog; and they were posted on the mauriprosailing.com website. Harken had them as calculators on their website where you could just enter in the numbers but for some reason they took them down (possibly for liability reasons if loads were exceeded).

Here you go:

Harken Loading Formulas
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top