Sheet Load Engineering

[lavery]

Brion,
For your reference I have sent a calculation sheet to rigging@briontoss.com.

BASIC SHEET CALCULATION:
I have run numbers using Harken and Lewmar. At 20 knots of relative wind the Harken calculator is about equal to the Lewmar reference. So here is the first area requiring judgment:

Harken results vary significantly with windspeed – as you have pointed out.

Harken and Lewmar are credible references, but results vary widely for main and 100% jib.

I went to 25 knots worst case, then selected the highest of either Harken or Lewmar, and settled on 2,000 pounds main and jib.

How would you play these calculations?

RUN THE NUMBERS
Exactly. Having calculated steady state load (2,000 lb.), would not one add pounds of shock load to arrive at design (working) load? Then divide by 20% to arrive at rope tensile strength?

Or are shock loads included in the Harken and Lewmar calculations?

Or are shock loads absorbed in the 20% calculation?

Like shock loads, elasticity is not quantified. Apparently elasticity is like the 3 bears’ story: not too big and not too little. But where are the guidelines to find just right?

Many thanks,

Jim