Mantus Chain Hooks: Load testing data revised

posted in: chain hook | 0

We reported earlier that our chain hooks matched the strength of the high test (G4) chain, and we did testing to verify this assertion. However, when doing preliminary testing we made an assumption that the load will be applied in the same plane as  the hook:  sample chain hook test. In other words we tested without chain as you see here…

imae for testing

website post on strength

 

 

 

 

 

 

 

 

 

 

 

However when the hook is loaded with chain the chain loads the hook not only in tension but also introduces as bending load, so we had to retest the hooks, the new loads data takes account of this asymmetric loading and thus had to be down graded. Loads currently published on the website reflect Independent tests by SGS using chain integrated with the hooks.

To date we did not hear of any any reports of failed Mantus Chain Hook, this is after being 3 years  on the market with thousands of hooks sold.

 Mantus Hook Strength Ratings

Hook Size WLL UBS Shackle (Size) Recommended Bridle Rope
1/4 in (6-7mm) 1074 lbs 4,294 lbs 3/8 in or 7/16 in Shackle 1/2 in
5/16 in (8mm) 1,878 lbs 7,511  lbs 7/16 in Shackle 5/8 in
3/8 in (10mm) 2,215 lbs 8,859  lbs 1/2 in Shackle 3/4 in
1/2 in (12-13mm) 3,442 lbs 13,767 lbs 5/8 in Shackle 1 in

The safety factor we use to determine the safe working load is 4, where other manufacturers use the safety factor of 3 or lower thus UBS is the best way to compare strength between products.

For comparison here is a chart of the relative strengths of other hooks available on the market.

Table: Stainless Hooks Breaking  Strength as reported by manufacturers

1/4 5/16 3/8 1/2
Wichard 3,520 lbs 5,280 lbs 6,600 lbs
Mantus 4,294 lbs 7,511 lbs 8,859 lbs 13,767 lbs
Victory Hook No Data Published No Data Published No Data Published No Data Published
Kong 5,500 lbs 11,000
Ultra Chain Grabber 7,000 lbs 7,000 lbs 11,000 lbs 17,600 lbs
C.S Johnson

Capitains Hook

No Data Published No Data Published No Data Published No Data Published
Seadog 4,630 lbs 6,830 lbs 8,800 lbs 16,200 lbs
Suncore No Data Published No Data Published No Data Published No Data Published

 

Why we think its acceptable to use a stainless steel hook inline with a snubber/bridle?

One first look one might make an argument that stainless steel hooks are too weak to use for snubbers and bridles especially when using hi test chain. But let us examine how snubber is stressed and how these loads differ from the ones chain experiences in the absence of the snubber. For examples lets assume we have a 40 foot boat and according to ABYC loads table at 42 knots of wind we can expect a load of 2400 lbs  on our anchor rode, and a load of 4800 lbs at 60 knots of wind. A typical 40 foot sailboat will be outfitted with 5/16 chain WLL 1900 lbs and breaking strength of 7600 lbs. So why does the chain have to be so strong? Shock loads produced without the use of the bridle or a snubber can produces loads on the chain that are 3 times (or more) the average load experienced by the chain.  The ABYC table already includes the shock loads in their calculated values (no snubber), so in this  worst possible situation in a 60 knot blow load on the chain is estimated to be around 4,800 and the chain with the UBS of 7600 lbs will likely survive the storm even without the bridle/snubber. This is why chain is tasked with having the breaking strength to 4 times the recommended working limit, and if we were using the hook to connect two pieces of chain the same requirement would necessitate.

However, the very fact that we are using the hook to connect a snubber to the chain these shock loads are to be dissipated by snubber and the snubbing hook will never see the loads the chain can see when used without shock dampening. The maximum loads on the rode are reduced as much as three fold with the use of a 30 foot bridle as the shock loads are absorbed. So a 40 foot boat in 62 knots of wind using a snubber will see loads of around 1600 lbs, well below the working load limmit for the 5/16 Mantus Chain Hook  1,878 lbs (UBS 7,511 lbs).

When an argument is made that the chain hook weakens the chain, the answer is yes if it is used a to connect two chains together or is used to shorten the chain without a snubber.  With the use of  properly sized snubber one should never even approach the breaking strength of the chain as exemplified above.

What gives our hook an advantage over competition is it is easy to take one and off and yet it positively locks onto the chain. In a storm a dislodged hook could be a disaster… or try to pay out chain in a storm when the hooks keeps falling off is at best frustrating and possibly dangerous. So we are still of a firm opinion that Mantus Hooks is the best pick for a serious cruiser outfitting his/her boat.

Greg Kutsen, Co-Founder, CEO, CTO of Mantus Anchors.