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Sail & Rigging - Hydraulic Backstay Adjuster S&S 57 1981
11 February 2014 - 01:19
#1
Join Date: 11 February 2014
Posts: 8

Hydraulic Backstay Adjuster S&S 57 1981
Hi John here

Could anyone indicate maximum and working loads and required travel for Navtec hydraulic back stay ram please.

11 February 2014 - 10:19
#2
Join Date: 02 January 2008
Posts: 1547

Dear John
It would be necessary to know which size tensioner it is, either shown on the manufacturer label, or by measuring the piston rod and rigging pin diameters. Backstay and headstay diameters, wire or rod, sloop or ketch also required. Assume the tensioner is connected to a control panel.
Kind regards
Lars

12 February 2014 - 02:15
#3
Join Date: 11 February 2014
Posts: 8

Dear John It would be necessary to know which size tensioner it is, either shown on the manufacturer label, or by measuring the piston rod and rigging pin diameters. Backstay and headstay diameters, wire or rod, sloop or ketch also required. Assume the tensioner is connected to a control panel. Kind regards Lars

Dear Lars
Unfortunately,the back stay tensioner is no longer there Lars.
The 57 is sloop rig 1981 model.I was thinking 5 ton with 15 inch
stroke may do but really have no idea.Thank you for replying
Kind Regards
John

12 February 2014 - 04:10
#4
Join Date: 11 February 2014
Posts: 8

Dear Lars
Back stay 3/8 inch rod with 3/4 inch clevispin
Headstay is1/2 inch 1 by 19 wire Norseman
marine eye aloft with 3/4 inch clevispin.

12 February 2014 - 10:58
#5
Join Date: 02 January 2008
Posts: 1547

Dear John
The tensioner should be the same size as the backstay, in Navtec terms this is -22, and the standard 10" throw is sufficient. The wire headstay is the limiting factor here, and assuming a safe working load 35% of breaking strength this limits the tensioner pressure to 2.8 kpsi.
If the headstay is 12 mm instead of 1/2" this reduces the pressure limit to 2.5 kpsi.
What is the hull number of your yacht?
Kind regards
Lars

19 February 2014 - 06:50
#6
Join Date: 11 February 2014
Posts: 8

Dear Lars
Apology for delayed reply .you know work!
Boat number 20/57.thank you for size of the
Navtec ram.I understand the engineering
principles a little better now
Kind Regards
John

10 March 2014 - 18:45
#7
Join Date: 09 August 2010
Posts: 15

Dear Lars Apology for delayed reply .you know work! Boat number 20/57.thank you for size of the Navtec ram.I understand the engineering principles a little better now Kind Regards John

Hi John & Professor,
I am the happy owner of Lianda 57 CB ketch built also in 1981, Hull 40, is that possible that 20 Hulls of this model were built during one year Time ?

11 March 2014 - 12:46
#8
Join Date: 02 January 2008
Posts: 1547

Dear Busschots
Your observation is correct, but the reason was not a tight production schedule, but that hull 020 was postponed from its original delivery slot, so much that this affected the year.

On average nine 57s were built per year, and in addition to that about sixty yachts of other sizes. In principle it would have been possible to build twenty 57s by cutting back on the others.
Kind regards
Lars

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