Cruising anchors?

[Munz]

(Slight) thread drift: What length (and type) of snubber rope do you use?
I use 5-10m of nylon 3-strand, enough so that it can stretch the best part of a metre if needed - never done so yet...
Most boats I see have only a couple of metres of snubber out, way too short?

Also using 3/8 dynamic climbing rope on a heavy 35ft mono. Snubber is 45ft. I think you generally want at least a boat length of snubber out once the waves get up a bit

 

[mckenzie.keith]

That's a "Dynamic positioning system". - DP for short. If you want to get really accurate you use more than GPS for postion. You'll have fixed sonar beacons or land beacons you can bounce a laser off etc. Then you have cm position accuracy (GPS drifts a meter or two)

Did you ever read "The Crest of a Wave" by Willard Bascom? There was a bit about using taut moored buoys as position beacons in deep water. It was for an oil rig, I think. Or maybe it was some type of research vessel. My first exposure to the concept of a taut moored buoy.

The weight is heavier than the buoyancy of the "float," and the line is shorter than the water is deep. So the buoy is pulled below the surface. And the buoyant force is a substantial fraction of the line's breaking strength. So the buoyant part remains nearly stationary above the weight, even if there is current. The buoyant part was where the acoustic transponders were.

Its an old book and kind of a career retrospective. So this must have been in the 60s or 70s. Certainly an interesting read. Or I thought it was, anyway.

 

[Zonker]

There are ton of different ways of establishing a position for a DP system. Taut wire isn't used as much these days.

DP Position Reference Systems - DGPS, acoustic SSBL/LBL, taut wires etc

Position Reference Systems used in Dynamic Positioning: DGPS, Hydroacoustic position reference, Long Baseline systems (LBL), Short Baseline systems (SBL), Ultra-short baseline systems (USBL), Taut wire, Laser-based systems, Artemis. Key topics: DGPS, Hydroacoustic position reference, Long...

www.offshoreengineering.com

(1) DGPS – Differential Global Positioning System
(2) Hydroacoustic position reference (HPR) systems
– Long Baseline systems, LBL
– Short Baseline systems, SBL
– Ultra-short baseline systems, USBL
(3) Taut wire
(4) Laser-based systems
(5) Artemis (microwave bearing/distance)

Depending on the vessel DP class you need either 2 (bare minimum) or 3 minimum different systems. If 1 seems off the other 2 vote it off the island. Just like a space shuttle computer.

 

[mckenzie.keith]

There are ton of different ways of establishing a position for a DP system. Taut wire isn't used as much these days.

DP Position Reference Systems - DGPS, acoustic SSBL/LBL, taut wires etc

Position Reference Systems used in Dynamic Positioning: DGPS, Hydroacoustic position reference, Long Baseline systems (LBL), Short Baseline systems (SBL), Ultra-short baseline systems (USBL), Taut wire, Laser-based systems, Artemis. Key topics: DGPS, Hydroacoustic position reference, Long...

www.offshoreengineering.com

(1) DGPS – Differential Global Positioning System
(2) Hydroacoustic position reference (HPR) systems
– Long Baseline systems, LBL
– Short Baseline systems, SBL
– Ultra-short baseline systems, USBL
(3) Taut wire
(4) Laser-based systems
(5) Artemis (microwave bearing/distance)

Depending on the vessel DP class you need either 2 (bare minimum) or 3 minimum different systems. If 1 seems off the other 2 vote it off the island. Just like a space shuttle computer.

The system described by Bascom (as I recall it, anyway) used a taut wire to position the acoustic beacons. The distance to the beacons was used to position the vessel. So it was a combination of 2 and 3, I guess. The acoustic baseline was short. But the taut wire was long.