Ericson 38 intermediate shrouds

[Nimue]

Hello,

I'm starting my research into replacing the rigging on my 1982 Ericson 38. I have the original specs regarding shroud and stay wire sizes but am puzzled by information in my copy of The Riggers Apprentice. The E38 is a double spreader rig with a Kenyon 5280 spar and double lowers so I'm using the 30 percent load upper, 30 intermediate and 25 lower model shown in the book. I've used my USYRU performance package information to calculate load values at RM30 and all the original Ericson specs work except for the intermediate shroud size. The E38 specs have the uppers as 9/32 1x9 which should give me a large margin of safety but the intermediates that Ericson recommends are only 7/32. If I use the 30, 30, 25 model shouldn't the intermediates also be 9/32 ?

Also, I would like to ask if, when calculating the RA and RM, if I should be using the displacement as specified by Ericson or use the actual weight of the boat as per travel lift haulout. There is about 5000 plus pounds difference with, of course, the travel lift weighing all the spare parts, tools, gear, tankage and extras that we all seem to accumulate aboard over time.

On another note, I want to thank you Brion for all the great information relayed to us at the Ericson Rendezvous group at Port Hudson last June.

Cheers.
C.A. Fields

[Brion Toss]

Hello,
This one just fell off my radar. Thanks for reminding me that your question was lurking, far down the scroll.
The distribution that I used in the Apprentice assumes that there will occasionally be serious loads at the 3/4 height of the mast, as when the jib is furled, the forestays'l is set, the main is reefed, and the boat is driving hard to weather. In these circumstances something like the lateral load that was at the masthead is now down lower, hence the shroud sizing.
But other designers have argued that, even if there were transitory high loads here, they aren't enough to justify the larger wire size. Only a load-cell test might settle this disagreement, though it might be worth running the more detailed calculations in Larsson & Eliasson's book. For your boat, I'd say it is safe to go with the smaller wire, particularly if you don't make much use of your forestays'l.
As for calculating loads, adding weight does not always add stability; sometimes it reduces it. Best to conduct an incline test.
Fair leads,
Brion Toss

[Nimue]

Thanks Brion,

As I don't have a forestays'l on the boat at this time and using the boat as a cruiser not racer, I agree that the forces at the intermediates would not approach masthead values. I do however sometimes find myself with main at first reef and genny furled beating into 20 knots or so as our location in Courtenay dictates a north south journey most of the time. As we all know the wind gods always choose to send the breeze from the direction we want to go.
I probably will up the size from 7/16 to 1/4 just to be on the safe side.
I will conduct a load test in the near future to obtain better specs before I re-rig.

Cheers.