Join Date: Jul 2000
Thanked 328 Times in 312 Posts
Rep Power: 21
Re: What if No-Chain?
Chainless anchor rodes are possible. Such would depend on: 1. the 'penetration power' of the anchor, and 2. the fluke angle of the anchor. Inotherwords, the 'trigonometry' (especially during the 'setting phase') has to probably be equal to a partly chained rode.
The obvious functional 'advantage' of part chain or all chain rode is during the 'setting' (and re-setting under changing wind direction and changing current direction) of the anchor; the chain holds the anchor stock essentially level with the bottom and thus enables an approximate 15° 'extra' angle (with 7:1 scope) during the 'penetration into the bottom phase' of anchoring.
In all probability one would have to initially 'set' such a chainless anchor with a ~10:1, or more, initial scope then haul in to ~7:1 ... all to get that initial setting angle of the flukes 'into' the bottom as is done with a part chain rode.
The Fortress double angle (choice of 32° fluke angle for 'sand' and 45° fluke angle for soft mud) would probably be my choice for a chainless rode ... just set it at the 45° angle and forget it; but, use an initial scope of 10:1 for sand and 7:1 for soft mud.
(However, Ive found that double angled Fortress anchors sometimes don't always easily 'reset' during ~180° current and wind shifts, as does the heavily-weighted tip 'plow-type' anchors)
Trigonometric (implied free body force diagram) analysis as attachment. The implication is that added chain gives weight/catenary and thus holds the anchor flukes in a much deeper penetration angle, especially during the 'setting' process. The analysis seems to imply a LOSS of ~10° scope angle due to NO catenary during the initial setting/digging-in phase; hence, the probable need to set such with a much longer scope during the 'setting' phase.
Correction to attachment: (TAN ^-1) 1/7 = .17 = 8°
Last edited by RichH; 10-30-2017 at 01:09 AM.