Dit stukje komt uit de Mantus knowledge base (
www.mantusmarine.com):
The role of the bridle/snubber system is to be able to absorb the shock loads by stretching and yet be strong enough not to fail when exposed to these high loads conditions. Thus we make sizing recommendations keeping this in mind.
Boat Size 30 – 40 feet 40 – 50 feet 50 -70 feet
Line Diameter (inches) 5/8 3/4 1
Bridle Length feet 25 30 34
Effort should be made to protect snubber/bridle line from chafe and inspect it for wear regularly.
Snubber should be properly sized and if done so can significantly decrease the loads on your rode.
For example:
So for a 40 foot boat in a 60 knot sustained wind storm, worst expected loads as predicted by ABYC would be 4800 lbs, most experts would agree that this is an inflated number that accounts for the dynamic loads that could be induced by waves and wind gust on top of the static wind loads and assumes the worst drag coefficients.
ABYC loads already account for the dynamic loads induced by the use of a non-elastic chain a condition mitigated with the use of a snubber.
A properly sized snubber can reduce these loads by 2/3. In our example from 4800 lbs to around 1600 lbs for a 40 foot boat in 60 knots.
Practical Sailor article on snubbers, by Drew Fry March 2016, studied this issue and tabulated the loads for a 40 foot monohull boat in 60 knots in the following scenarios:
Chain no Snubber – 4,140 lbs (exceeds working load limmit for 5/16 Grade 30 chain)
ABYC worst case – 4,898 lbs
Chain with a 30 foot ½ inch three strand nylon bridle – 1,574 lbs (the only scenario where load on the chain is below working load limmit for 5/16 chain 1,900 lbs)
Chain with a 6 foot 1/2 inch three strand nylon snubber – 3,249 lbs
Working Load Limmit for 5/16 Grade 30 Chain 1900 lbs, Breaking Strength 7600 lbs.
-62% reduction in peak loads or about 1/3 of the ABYC worst case with the use if 30 foot bridle
-Only 22% reduction in peak loads with the use of the 6 foot snubber.
Thus the use of the a properly sized snubber can significantly reduce the loads on your anchor and you chain, by as much as 2/3 with a 30 foot bridle.
Volgens dit artikel kan een goede "rekker" de belasting van het ankertuig met 2/3 verminderen.
Een beetje in tegenspraak met het verhaal van teveel rek van Rocna.
Het smelten van nylon lijnen bij veelvuldige rek geldt niet voor de diktes die hier ter sprake komen: bij Smit zeesleepdienst gebruikten we nylon rekkers, dubbele 28" (omtrek, dus ca 24 cm diameter. De stalen voorloop op de sleep moest zo lang zijn dat de rekker onder normale omstandigheden onder water zat ivm koeling. Bij zwaar weer kwam de rekker regelmatig boven water, en na een slechte reis kon je merken dat de kern gedeeltelijk gesmolten was: de rekker werd dan stijf.