How to use this calculator
- Measure pin to pin. Use bearing pin centers for the stay or shroud and note whether the measurement was loaded or slack.
- Enter hardware lengths. Use exact terminal allowance plus safe closed and open turnbuckle dimensions from the hardware or drawings.
- Pick a setup position. Set the turnbuckle near the desired build position so there is adjustment in both directions.
- Enter wire stiffness data. Use selected wire breaking strength, target tension, diameter, modulus and area factor only for the stretch allowance.
- Check reserves. Review cut wire length, take-up reserve, turns to closed/open and stretch before qualified rigging review.
How it works
Turnbuckle setup length is interpolated between the safe closed and safe open dimensions: L_setup = L_closed + (L_open - L_closed) x setup_percent / 100
The target wire span is the overall pin-to-pin length minus the hardware allowances: L_wire = L_pin - A_fixed - L_setup
When the entered pin-to-pin length is a loaded/tensioned length, the cut
wire length subtracts estimated elastic stretch:
stretch = F_target x L_wire / (E x A) L_cut = L_wire - stretch
For a slack/shop basis, L_cut = L_wire.
For strength and target-tension checks, use the standing rigging wire size calculator and standing rigging tension calculator.
Worked example
Verified against the live calculator
A measured 30 ft loaded pin-to-pin shroud with a
5 in fixed-terminal allowance and a turnbuckle that is
12 in closed, 18 in open and set at
45% travel uses a 14.7 in turnbuckle setup
length. The target wire span is about 340.3 in. With
5000 lbf wire at 15% target tension, the elastic
stretch allowance is about 0.252 in, giving a cut wire
length of about 28.34 ft.
Frequently asked questions
How do you calculate a replacement standing rigging cut length?
For this first-pass worksheet, cut wire length starts with the target pin-to-pin length, subtracts the fixed terminal allowance and the turnbuckle length at the chosen setup position, then optionally subtracts estimated elastic stretch if the measured length is a loaded/tensioned length.
What is turnbuckle setup position?
It is where the turnbuckle sits within its safe adjustment travel when the replacement assembly is built. A mid-travel setting leaves adjustment both shorter and longer after installation.
Can this replace a rigger or terminal manufacturer drawing?
No. Exact terminal take-up, swage or mechanical fitting allowance, thread engagement, toggles, chainplates, fatigue, corrosion and final rig tune require manufacturer data and qualified rigging review.
When should I choose loaded versus slack measurement basis?
Choose loaded/tensioned when the pin-to-pin length came from a rig under target tension and you want an unstretched cut length. Choose slack/shop when the entered length already represents the intended untensioned build length.
Method & assumptions
- Requires exact hardware dimensions or measured fitting allowances; nominal catalog names are not enough.
- Turnbuckle open length must already respect safe thread engagement.
- Elastic stretch uses nominal wire diameter, effective modulus and metallic area factor as a screening estimate.
- Does not model terminal stretch, swage set, constructional stretch, mast bend, spreaders, toggles, chainplates, fatigue, corrosion, dynamic sailing loads, survey condition or final tune.
- Standing rigging is safety-critical. Use a qualified rigger, surveyor or naval architect for final replacement specifications and inspection.