AI rudder modification experiment

Author: josh

Category: Equipment, rigging & preparation

Published on Friday, 06 August 2010 18:36

Written by Josh

Taking one for the team

I've recently discovered a fairly accurate way to go about determining the age (or to be more accurate, how much use it's had) of an Adventure Island trimaran. The amount of scratches visible on the base of a hull is one way to check for how much wear and tear a kayak has, but I think an even more accurate way to determine how much use an AI has had is to inspect the rudder up/down lines. The furrier they are, the more chafing they have endured (at the drum guides) and this will always be proportional to how often the up/down lines have been engaged, and thus, how much use the boat has had.

Spectra line as used in Hobie kayaks is incredibly abrasion resilient stuff and even more incredible breaking strain specifications. First-time Hobie buyers are often quick to question how long they may last (I was one of those myself) and they're always pleasantly surprised to hear what I have to say in response, which is that not only have I naver had to replace a line through breakage or even wear personally, it's also extremely rare for us to ever have to do it for a customer. I couldn't tell you what the average life expectancy of the up/down rudder lines on an average Hobie Mirage kayak is because I still don't know. For almost every single user in most models of Hobie kayaks, wear and tear on rudder lines is simply not an issue they have had to contend with.

That changed for me this week for two closely related reasons. One of them is that while busy installing a new sounder onto my kayak I took the time to inspect the yak from bow to stern. As a part of this I paid close attention to the up/down rudder lines and I was inspired to do this after paying close attention to a recent modification to the Tandem Island rudder, which is to have part of the guide cut away, as pictured here.

The reason for this is that (and I quote Hobie tech notes here): 'This portion of the rudder line entry point exerts a severe load on the 2:1 down line when turning hard to the left. By removing this section, up / down function is improved and wear against lines and the rudder head are reduced'.

This is obviously due to the extra size of the rudder and sail combined by the new 2:1 up/down system and it's not something that has come up with solo AIs, but it got me to thinking. I wonder what cutting that piece away on the solo AI might achieve? And are my up/down lines chaffing at the very same point, albeit at half the rate of abraision. When I took a moment to inspect, sure enough, the up/down lines were showing signs of wear right where they pass through the guides. For a 2008 AI thats had more use than... well, any other AI I'm aware of, this came as no surprise at all. If anything, what was surprising was that despite the obvious signs of chaffing, the lines still had plenty of strength (I certainly couldn't break them by hand).

Still, being the cautious sorrt of guy that I am, I figured now might be a great time to replace the up/down lines. And while I'm at it, I may as well cut away that very same piece on my own rudder and see what sort of effects it has, positive, negative or neutral. So I did. I purchased a universal rudder line replacement kit and used 2 (of the 4 lines supplied) to replace the up/down lines. My steering left/right lines were just fine and I saw no need to replace those, so I now have 2 spares, one of which now lives in my safety box, along with a coil of spare spectra line that comes with the kit).

As soon as I'd pieced it all back together I played around a bit, actuating the rudder up and down, left and right. And I couldn't see any reason why having cut away this piece might cause a problem. But I can certainly see how it might help extend the life of the up/down line on an AI, which although isn't under the same pressures exerted by the TI, is still under considerable pressure at times. Instead of the line having two guide holes, my rudder now has only one. It's taken about 2 years of near constant weekend use for it to reach this point, so thats my measuring stick. How will these replaced lines look in 2 years time? Or will my TI influenced modifcation result in catastrophic failure long before then? Time will tell. But after inspecting the finished job and seeing it in action (on land at least) I've no reason to expect that what I have achieved here is to reduce the amount of points of guide wear from 2 to 1, and I'm willing to bet these newly replaced lines will last longer.

I'll report back in 2 years time... or sooner if things go wrong!

Edit: nothing went wrong :-)

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