Your feedback

What is your experience of using small blocks? An interesting block test and the general principal of the larger rope/sheave diameter ratio is well accepted. That is why we stipulate the maximum line size suitable for the 16mm Airblock is 5mm. Hence the friction is a bit high when tested with 6mm. I worry that your test is perhaps a little flawed on a couple of fronts.

Firstly our blocks are designed for repeated cyclic loadings. A short test on a new block is not necessarily an indication of how it will perform over a period of time. Throw in a bit of salt and dirt and the results can be very different. The reliability of a block under working conditions is what we particularly look for. This is one reason why we use quite a large clearance between the balls and the sheaves so that the balls don't jam or skid on any trapped debris. Also, it is important to size the block so that it works within its capacity without permanent deformation.

That is why we stipulate a workload of 91kgs for the Micro block against the break load of 544kgs. Yes, the block can operate at a higher load, however if the deformation is such that the friction builds up then the block will have a short, brutal life. As we have seen over the years it is very tempting for people to use the smallest, lightest blocks they can get away with, but this approach can sometimes disappoint.

From Matt West
What is your experience of using small blocks? Peter didn't need to go through all this scientific testing and review work to establish which blocks work best.... just ask the worldwide 49er and 18ft skiff crowd who use tiny blocks under extreme loads in the spinnaker halyard/hoist system.

On a 49er, particularly the spin halyard block at the masthead is tiny (28mm or 30mm), as is the line used (4.5mm spectra) and the load from the spinnaker is enormous. I have demolished approximately eight (Harken and Ronstan) spinnaker halyard blocks in one season, sailing in a muddy bottom /shallow water bay off a sandy beach. However, not all of those failures were due to mud/sand jamming ball bearings.

Plastic sheaves under load are useless, as modern man-made fibres just saw through them, even when the blocks don't jam - alloy sheaves as used in wire bullet blocks are a must. Plastic cheeks are also a waste of time, since off-centre loads saw through these like the proverbial hot knife through butter, and then jam the line in the neat little groove slots. Full stainless cheeks are also a must. And finally there is the unexplained disappearance of my Harken 304 wire bullet block from the masthead one day during a 35kt blow.

It was there when we left the beach, and gone when we returned. We can only assume that it shook out the split ring / cotter pin arrangement at the head of the block (without breaking the Kevlar loop it was tied to), then the cheeks swivelled allowing it to release the spinnaker halyard without undoing either end of the halyard system. Very strange.

From Mike Peberdy
What is your experience of using small blocks? My experience is with using small blocks on the 49er and 18 foot skiffs. The main problem is durability (not breaking strain, even on the 18). Three areas of concern:

1) Sheave burn out. Particularly when used on halyard blocks. Ronstan high load blocks are an option but do not run freely enough as they do not have bearings.

2) Cheek burn out. The line may be release on a slight angle resulting in the destruction of the cheek.

3) Accidental breakage. Sheaves that are deck mounted get broken easily underfoot resulting in loss of bearings etc. The ideal block would have an alloy sheave, metal cheeks similar to the air block and bearings. I guess if a company came up with the perfect block you wouldn't need to keep replacing them...built in redundancy I suspect!

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