I agree with the understanding, On a larger boat, the knot is to secure a sail shackle (in my case), on a small boat, I would use the knot on the sail (tying and untying when raising or putting the sail away in covered storage).
I do not assume anything of the such. Please do not attribute things to me that I did not state. I listed the data to examine the function of the model. It is a model that may have use in considering the size of a halyard in the specific case the main halyard. The model provides a calculated load for the main halyard.
The model uses the P length (height of the main luff) to calculate the load on the halyard. I shortened the P value to 60% of my total P Value and used the 40knot wind speed to see what the models load would report. 60% height of the main corresponds to about double reef for physical sail reference on my boat. The loads reported were for 2 different diameter halyards. No reference to the effect of double reef or mainsail position was considered.
It also shows a coefficient number which appears to be an attempt at a load number above the base load. Considered to be a "safety factor" calculation. No detail as to the formulae used was evident. The model is a take it as such or leave it consideration by me.
The mainsheet was not even considered in the model. I did not reference the mainsheet in my post.
The wind speed in the model was just that wind speed. The model calculated loads on the main halyard based on the model calculation and assumptions in the formulae. The model formulae was not defined in my post nor was it evident on the website. Perhaps someone interested in the model formula could explore the details and report back.
I found the model an interesting effort by the creator to preform a complex calculation. I made no judgement as to the accuracy. I listed the data inputs and the calculated outputs. While they appeared to be relevant to my experiences with halyards the numbers have not been scientifically examined. I made no warranties other than to list personal observations.
Thank you Drew for your post.
Sorry. I thought I was only pointing out things I am reasonably certain the model assumes for you. This is a weakness in using models without an explaination of the basis and assumptions. However, note that the model does NOT give a provision for reefing. What use wouold it be to the rigger or to anyone without this provision? The reason is because it is already in there. You enter the reefing windspeed and you are done.
Mainsheet tension is a little higher when reefed, but typically not that much higher than at the reefing point. The heeling moment is the same, the lever arm/area has been reduced by perhaps half or so, and the traveler is nearly always eased a bit and the main twisted a bit to drive through waves. In my experince, the mainsheet tension, and by proportion the halyard tension, might increase by 50%, not more than triple. I certainly do not sheet 3 times as hard. I could not and the boat would go over. And I have measured this with a load cell on two boats.
The main sheet tension is implied in the model. Obvious mechanics. Without it there would be no relationship between wind speed and halyard tension because the sail would simply flog. The model certainly assumes the mainsheet is hauled tight, the boom centered, and the boat on her feet, into the wind, no feathering.
The safety factor was almost certainly a working load factor for polyester rope, rather than a fudge factor. No additional factor is added beyond that.
It was not an attack an please don't take discussion that way. We'll never learn anything. Just food for thought. I do this sort of engnieering, so I have some experience regarding how such a model is built.
