Mast rake and pre-bend

[Czarina Blue]

Hi there, do we have any info on suggested tuning of the rig. My 38 is 1973 with the gold-anodised masts by Proctor. I’ve had a bizarre tune-up by a rigger in Colombia and it’s made me take more interest in my standing rigging tension and tune.
from what I can glean from the web, older boats with thicker-walled masts like ours should have only gentle curves of any kind and only very moderate prebend.
what about rake? The usual 1-2%?
My previous two riggers have given very little rake and a tiny bit of prebend towards the top only. The new riggers have put on a comical amount of rake and a lot of pre-bend from the spreaders upwards. It looks quite bizarre. Also they’ve put way more tension on the backstay than that by previous riggers.

Any thoughts gratefully received.

thanks

[Czarina Blue]

Also tensions nearer to 10-15% of breaking point rather than 15%+ on modern rigs?

[Van]

Rainshadow is 1974 also with the gold anodized spars. The original Nic 38 manual does not comment on rig tuning.

Because the mast is pretty stiff, I typically introduce some aft rake, but not much.  I would guess 3-4 inches at the top of the mast based on just looking up the mast from the deck to view the bend (which I estimate is 1%).  Most of the bend occurs in the upper part of the mast.  The lower shrouds are used to help define where the bend happens.

I tighten the shrouds to 10% or a little more, and the stays to 15% or a little less.   Then, take it for a sail and see how it behaves, and adjust as necessary.  I use the ruler method for measuring tension. I like the Loos gauges but we have 5/32, 7/32 and 9/32 wires, so we need three of the gauges, that’s hundreds of dollars…..

I guess if I were you, I would defer back to the old way of doing things. A lot of rake is going to add weather helm.

The mizzen standing rigging is unusual.  There was a famous rigger in Port Townsend, WA called Brion Toss, who happened to be walking by Rainshadow when she was on the hard there.  I found him standing just behind the boat staring up at the mizzen with a puzzled look on his face. I struck up a conversation and we talked about the unusual arrangement of the shrouds.  After a couple of minutes, he smiled and said he understood what the designers had done.  He was very pleased, and asked me if I would mind if he brought around his class later so they could all look at it. (He taught rigging).

What he found interesting was how the designers used the two upper shrouds to combine to act as a forestay, and the lower shrouds to control the shape and provide much of the the tension counter to the upper shrouds, with the running backstays to finish the balance. (OK, this is my poor version of his explanation).

Van

 

 

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