What size standing rigging, H.C. 36

[county]

Hi, I was hopping someone might let me know what diameter cable was used on the H.C. 36 or other models close to that L.O.A.

My boat a Mao Ta 36' had 5/16 cable on the very heavy wooden mast with antiquated external Forespar furling main unit.

The new to me aluminum mast came with almost new 9/32 cable, its seems to me that a reduction of 0.032 in diameter would be acceptable considering the substantial loss of weight aloft.

Any Thoughts?
Thanks.

[mimoza]

You want the cable to be able to withstand the righting moment of the vessel, regardless of the weight aloft. Think of it this way: If the stick is in the water, its weight is of very little consequence.
Rig design and spreader angles have a lot to do with the calculations. Brion Toss' book The Rigger's Apprentice treats all these subjects in good detail. If you don't feel comfortable running the numbers yourself, get a professional rigger. Bob Perry designed the 34, but treats the 36s as his illegitimate children. For a modest fee, I think he would provide you all the info you need. For the money spent, you can have peace of mind with the 9/32, or perhaps end up saving your rig by getting 5/16 wire

Robert Perry
11530 Tulare Way West
Tulalip WA 98271
Phone: 360-652-7771
E-mail: info@perryboat.com
Bob Perry: RHP@perryboat.com



What's your HIN?

[mimoza]

[county]

Thanks for your comments!

Yes I do get your point.

When running the numbers with Brion Toss's formulas I get a R.M. of (33' L.W.L RM=45,000)(shroud load 12,097#) but I feel like some of the necessary data is still not available thru The Rigger's Apprentice. How do I know what % of the load is divided between the shrouds. Even using Toss's example he shows 45% for the uppers and 32.5% apiece for double lowers, but then what % do the intermediate backs take up and how does he come up with those % in the first place? Also doesn't having double lowers and intermediate backs reduce the 45% load that the uppers carry? Its also confusing to me how displacement doesn't effect R.M.

Any insight on this? Maybe I need Skene's.

I have had some contact with Bob perry in the past and he has been helpful! I like to try to figure things out as much as possible before I bother a man that has better things to deal with than a 35 year old design that was basically stolen from him.

[mimoza]

Displacement plays a part in R.M., but geometry is much more important. Think of a cat, which can have a very high R.M., but a relatively small displacement. The wide hull gives the displacement more leverage to work with, and so increases the R.M. There isn't much room for heeling. How heavy should the wire be? Lot's of food for thought here. Could the forces exceed the R.M.? In a gust perhaps.

A monohull spills wind by heeling, so the total force on the rig should (theoretically) never exceed the R.M. In a gust? Perhaps. Neptune always seems to offer his own opinion.
I haven't looked at Toss lately, so I won't comment on your actual numbers.

I think Bob has reached a point of philosophy w.r.t. the 36s. If he needs anything from you, I suspect he will ask for it in the form of an invoice.

Please post your findings, Thanks.