Sale

Ronstan Series 75 Two-speed Mainsheet System 4:1 - 8: 1 - Bottom Block Only

$ 827.62 827.62 USD $ 919.58

779.50 €

10% Off

Block Sale

Days

Hours

Mins

Secs

Recommended line - Max Ø (mm)
Brand
Range
SWL (kg)
- 1100
NBL (kg)
- 2300
Sheave Ø (mm)
- 75/50
Purchase ratio
Weight (g)

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Mainsheet systems

Ronstan Series 75 Two-speed Mainsheet System 4:1 - 8: 1 - Bottom Block Only

~~$ 919.58~~ $ 827.62

10% Off

Add to Cart

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Brand: Ronstan

30-day money-back*

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*Exclusions apply. See our Refund Policy.

Ronstan Series 75 Two-Speed Mainsheet System 4:1 / 8:1 – Bottom Block Only – RF72900B

The Ronstan Series 75 Two-Speed Mainsheet Bottom Block (RF72900B) is a high-load cockpit control block designed as the working unit in a 4:1 / 8:1 two-speed mainsheet system for sports boats and keelboats up to 12m (40ft).

This block manages the continuous mainsheet through twin cam cleats, controlling both line tails. One tail runs on the direct 4:1 purchase for fast trimming, while the second engages the full 8:1 purchase for increased mechanical advantage and precise load control.

This dual-speed functionality allows sailors to adapt instantly to conditions—using the lower purchase for speed and the higher purchase for fine tuning under load. When manoeuvring, both tails can be worked simultaneously to quickly ease or trim the mainsail.

With a Safe Working Load of 1100kg, this block is matched to the loads generated in higher-powered two-speed systems. It is designed to pair with the Ronstan Series 75 Two-Speed Top Block (RF72900T) to form a complete system.

Constructed to Ronstan’s Series 75 standard, it features 75mm sheaves suitable for lines up to 12mm, acetal ball bearings for smooth operation, and anodised aluminium cheeks for strength and durability. Ratchet sheaves provide additional holding power, reducing effort on the trimmer.

When fitting to traveller cars, ensure adequate support for the bottom block and use a stand-up spring kit (RF324-2) for correct alignment and optimal performance.

Specifications

Specifications for Ronstan Series 75 Two-speed Mainsheet System 4:1 - 8: 1 - Bottom Block Only

Ropes
Recommended line - Max Ø (mm)	10
Boat
Load
SWL (kg)	1100
NBL (kg)	2300
Dimensions
Sheave Ø (mm)	75/50
Undefined
Purchase ratio	4:1 or 8:1
Weight
Weight (g)	1035

Product specifications are provided for guidance only, subject to error / change and without warranty or guarantee. Refer to manufacturer’s own datasheets / manuals for further information.

Specifications

Ropes
Recommended line - Max Ø (mm)	10

Boat

Load
SWL (kg)	1100
NBL (kg)	2300

Dimensions
Sheave Ø (mm)	75/50

Undefined
Purchase ratio	4:1 or 8:1

Weight
Weight (g)	1035

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Ronstan Series 75 Two-speed Mainsheet System 4:1 - 8: 1 - Bottom Block Only

$ 827.62 827.62 USD $ 919.58

779.50 €

Available on request

Block Sale

Ronstan Series 75 Two-speed Mainsheet System 4:1 - 8: 1 - Bottom Block Only

Description

Ronstan Series 75 Two-Speed Mainsheet System 4:1 / 8:1 – Bottom Block Only – RF72900B

Specifications

Specifications for Ronstan Series 75 Two-speed Mainsheet System 4:1 - 8: 1 - Bottom Block Only

Specifications

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