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Sail & Rigging - Forestay and Backstay Overall lengthsS&S57 No 20/81sloop
19 August 2016 - 00:44
#1
Join Date: 11 February 2014
Posts: 8

Forestay and Backstay Overall lengthsS&S57 No 20/81sloop

Could you please advise overall lengths of forestay and backstay

Backstay has Navtec ram 1.14 m fully extended intend to use

-30 straightened Round rod for forestay and 15T Kevlar for backstay

Rig out of boat so measurement a little difficult

19 August 2016 - 17:41
#2
Join Date: 02 January 2008
Posts: 1547

Dear John

There are also other things to consider.
If there is a 12 mm wire forestay now, it must be noted that a -30 rod forestay with high fatigue jaw terminals has slightly bigger pins, and there are also differences in the toggle gaps. Is a rigger involved here, and is he aware of these differences? 
 
For the backstay it is suggested that a stretch equivalent Kevlar size is considered, and for 12 mm wire this is the 20T size.
Kind regards
Lars

22 August 2016 - 00:25
#3
Join Date: 11 February 2014
Posts: 8

Dear Professor

Thank you for your incites as to end toggles and clevis pin sizes.

Navtec in USA ,me in Aus and rigger in PI usual remote area 

considerations.Forestay has Harken Furler and link plates for 

elevation of the Furler spool.Concerned about my measurements

of forestay and backstay lengths.wondering if I put on the new V's

and D's then make another measurement with mast installed in 

yacht .Would hope designer has accurate lengths of rig V's, D's,

forestay,and Backstay but cannot find legible rig drawing anywhere.

Will go up to 20T on backstay.Thank you

22 August 2016 - 08:41
#4
Join Date: 02 January 2008
Posts: 1547

John
Thank you for the information
Would recommend a toggle at the lower end of forestay also with linkplates. Do you have the original toggles?
I can provide lengths scaled off a large paper sail plan, but the paper may have distorted slightly during 39 years. Would you like me to measure the mentioned dimensions?
How are the lower spreader ends configured? Eyes between link plates should not cause problems, but if there are double jaws these need to be specially ordered, or the configuration changed.
 
The headstay upper and lower end pins have been 19 mm originally, and Navtec -30 pins are 22.2 mm. The recommendation is to use 19 mm hi-strength pins, and put sleeves around them to fill up the gap.
The mast top headstay eye is 25 mm thick, original toggle fits, but the Navtec toggle has to be opened some 3 mm in order to fit around the eye.
Kind regards
Lars
 

24 August 2016 - 03:52
#5
Join Date: 11 February 2014
Posts: 8

Dear Lars

If you could provide lengths from the plans this would be of enormous 

assistance .The lower spreaders measure 1.49m and ss plates are 

attached to the outboard end to receive the eyes of the V1,V2,andD2

V2 and D2 are attached to the ss sandwich plates by 3/4 "clevis pins

51mm long .The 1" clevis pin for the V1 is 57 mm long.

Thank you for your last info which I have passed on to

the rigger in Subic Bay.

24 August 2016 - 14:06
#6
Join Date: 02 January 2008
Posts: 1547

Dear John

The P-measurement scaled off the paper sail plan is 19744 mm, if your actual P is 19766 mm a scale factor of 1.0011 should be applied to the measurements given below.
 
Headstay total length including toggles and link plates 22976 mm, backstay total length incuding link plates and tensioner 23968 mm. This assumes 350 mm of rake measured along the aft side of the mast.
 
V1 from deck surface to center of spreader end 8800 mm, D1 fwd 8768 mm, D1 aft 8864 mm, V2 between centers of spreader ends 6784 mm, D2 6848 mm, D3 5824 mm.
The D1 and D2 upper ends assumed to terminate at the spreader root centers, the tang pin distance below spreader center to be deducted. Also D3 tang length to be deducted.
 
It is possible to compensate for slight deviations in standing rigging lengths by cutting or adding at the bottom end of the mast tube.
For hi-strength pins a material denoted Aquamet 22 is recommended.
Kind regards
Lars

29 August 2016 - 03:54
#7
Join Date: 11 February 2014
Posts: 8

Dear Lars

Thank you for your help just what I needed to check

the measurements for the standing rigging.

Many Thanks

John

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