Main block shackle twists and bends

I have a very annoying problem with the shackle that connects my main block to the traveler car.
The block (original 1981 H18 seaway block) connects to the traveler car with a stamped shackle. Every time I go sailing, I end up with the shackle twisted/bent.
I don't notice anything wrong with the block itself, and the cylinder at the foot of the block to which the shackle attaches is rotating freely without any friction. I have tried a stronger bow shackle but I get the same results (to the point where it is very hard to unscrew the shackle pin).
Is this a known design flaw, or is there something wrong with my setup?

Here are 4 pictures that illustrate the problem

Hard to say without seeing your setup. I've never had a problem with a bow shackle. I also usually leave the traveller car attached to the mainsheet blocks. I never really seem to find any reason to remove it.

_________________
Mike

'79 H18 standard 'Rocketman II' sail #14921 RIP
'78 H18 (unnamed) sail #14921
'08 H16 sail #114312
'97 H21SC sail #238

My guess is the block rotates freely when under no or low load, when it's loaded up, it is probably binding up.

You could try using a swiveling shackle, but your best bet would be to swap out the lower block with a Harken. You will find the Harken blocks are superior to Seaways in every respect.

sm

My two cents. You are using two light a weight shackle for this connection. The shackle you are showing in the pictures looks like ones use for the stock boom triple single blocks. If you are sheeting in hard while on the wire the angle you are pulling and the light weight of the shackle might explain why its bending.

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Corkguy H18, Tiger, Wildcat

It's true that those shackles are a bit thin. Before those I had a stronger shackle with a screw-in pin. It was much thicker, but still got bent. The bend wasn't as bad, but because it was a screw-in, it made it almost impossible to unscrew, so I switched to this lighter shackle with a quick release pin.
What does the stock Hobie shackle look like? I couldn't find a part number for it, as it is probably simply just part of the block assembly.

I still suspect it is a matter of the swivel binding up under load. Rig your boat on the beach, sheet in hard on the main and see if the lower block will rotate. Eventually, if you keep twisting that shackle back and forth, it is going to fatigue and break off. I would definitely carry a spare on board.

sm

Agree... check that the post in the block actually does swivel in any loads. Some posts can be locked. This one should spin easily.

_________________
Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)