To shear or not to shear...

Recently I have been contemplating the concept of the 'shear pin' as used on the Hobie Adventure and Tandem Island kayaks. In both boats there are 3 of them, one of which is the rudder pin. No matter how much wiser you think it might be to replace the default rudder pin with something stronger, it probably isn't. Under stress that pin is supposed to shear and this is to prevent anything more critical from breaking. This is generally well known and accepted by AI/TI users; the rudder pin is basically a fuse. Better the pin break than to have the gudeon ripped straight out of the transom, for example. Fair enough.

The other two shear pins are for both aka braces (both left and right) and are there for much the same reason - to prevent further breakage should stress or shock cause one of the shear pins to fail. However, in my opinion, the consequences of having one of these shear pins give way have potential to be much greater than just breaking something else. The more I have thought about it, the more I have started to think that I'd rather have a solid shear pin for the akas and risk further breakage instead of dealing with the consequences that are likely to occur should one of these snap while sailing. The very thought of it inspired me to replace my existing nylon shear pins with stainless 1/4" bolts a couple of weeks ago. This may very well void any warranty related issues that may arise from doing so, but I'm more interested in safety than I am who or what is responsible for a costly breakage.

Ironically, today my paranoia was validated when one of our members explained to me today that just last week a leeward shear pin snapped on him while sailing in on low surf, and when he told me this I knew what he was going to say next. The leeward pontoon folded immediately and physics took over as his AI toppled over on it's side. Because he was in shallow water, this did indeed result in several breakages anyway and it could be fairly said that these would not have occurred if the pin didn't give in. Nor is it likely that he would otherwise damaged the akas or connectors had he been using steel pins. In this case the shear pins didn't prevent a breakage - it could be fairly argued that they actually helped contribute to breakages, and costly ones. A mast was broken, along with a few other components (lets not mention the now multi-piece rods).

I've been using the AI for a few years now and put more miles on the water using one of them than anyone I know. So far I am yet to encounter an instance where the pontoons were put under such load or shock that was likely to break anything. Put another way, I tend not to sail my AI into solid objects. Thus, the likelihood of my sailing pontoon-first into a jetty wall are pretty much nil. So I really don't see how I'm likely to cause any inadvertant damage to any part of the hull through shock to the akas. As such, the shear pin just seems a little unnessacary.

What I have seen happen, however, are aka shear pins breaking while the boat is being sailed (usually for no other reason than wear and tear) and most often this occurs to the leeward side. The stronger the wind, the faster that yak is likely to topple over. This is bad if in the surf zone because then further breakage is more than likely. Even though extraneous breakage is less likely to follow a topple-and-turtle in deeper water, this instance might be more of a safety issue. Either way, if you're sailing in anything more than low winds, an unexpected shear pin snapping could well result in an unexpected capsizing. And as far as I'm concerned, this is not only more likely to occur than damage being caused to the hull via shock to the akas, it's also a worse case scenario.

Think it through. If you do so and reach the same conclusion as me, there's really only one obvious answer: a stainless steel bolt to replace the default nylon one. But that's a decision that could have potential consequences, so it's a trade off no matter how you look at it. It's a question of lesser of two evils.

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