Over the past year or so I've seen many reports of rudder failures and/or loss in cruising boats. Apart from age and "cycles" like we've talked about in the past, I'm wondering what the cause is. And I'd love to get feedback on this from the great designers we have around here - as well as the salts.
I'll lay out my hunch to get things started, based on my own experience...
Last year the boys and I did a 150-mile offshore delivery of a friend's Pearson 365 in some relatively "rough" conditions. The seas were maybe 3-4 meters, and steep (left overs from a big storm in the Gulf) and winds were in the high 20s. We were, unfortunately, sailing with that stuff just forward of our starboard beam. So, though it was a gentle beating for the most part, it was pretty jumpy and rolly. We were steering with AP.
The next morning things were calming down and we suddenly lost steerage. I grabbed the wheel and confirmed we could
still steer, while my friend's son reset the AP - thinking it had just been a glitch. It was fine for a minute or so, then we lost steerage again. I asked him to take the wheel and I opened up the lazarette.
The AP, a ram arm model, had ripped off its base, where it had been bolted, and was rolling around. At least we still had the rudder. We obviously shut down the AP and steered the rest of the trip by hand.
I remember thinking about the fact that there had been a lot of force applied there to rip that thing out. Then I started thinking about all the offhsore races I'd done - hand-steering only - and never recalled feeling that kind of force through the wheel - even in rough conditions.
So, my first question...is AP (especially ram arm versions) a liability in big seas? My hunch is that it is and that is one of the primary causes in these rudder losses we're seeing on cruising boats.
AP is almost continually used by sailors (especially short-handed cruisers) these days on long trips. And it especially used (I think) when things get tough because it seems to be safer than standing in the cockpit steering 24/7.
But when you look at the boat motion in these videos - you see that there is a tremendous amount of lateral force being applied to the rudder:
Now, that is an F10/11 in the second video. If I were unfortunate enough to be caught in that I'm pretty sure we'd already be on a drogue...not pushing the boat like that. I'd be way too scared.
But, you'll notice that in both of these cases, the boat is being hand-steered. It seems to me that this provides a great deal of "cushioning" (response time and give) for the rudder over a mechanical ram.
If your stern is swinging through 20-30 degrees at surfing speed on AP...what kind of force are we talking about on the rudder and stock? It seems astronomical.
I this a cause of the failures we're seeing?