Tips, Tricks & Thoughts:
There’s a headline to attract attention!
Fender washers, or penny washers, as guys of my advanced age with British backgrounds call them1, are much beloved by us yachties. Heck, I have a bunch of them, just in case I need one…except now I know I probably never will.
OK, that headline was a test of how clean your mind is. If you didn’t immediately assume that I was writing about my current fixation, bolted joints, you failed.
Anyway, one of the things that never ceases to amaze me is how common sense can fail us non-engineers.
In that vein, here’s something I only learned in 2019 when I hired an engineer to advise on what I needed to do to solve the excessive flexing in the plate that takes the thrust from the Aquadrive on the McCurdy and Rhodes 56 (M&R 56) that had been installed by a welder and machinist some years before.
Common sense would say that if we want to double the resistance to bending of that plate (engineers call this stiffness) we should double the thickness.
As you might have noticed, I have become a bit fixated lately on how bolted joints work. And now I understand more about the subject (thanks Eric and Matt) I see poorly put-together ones everywhere I look.
This would be bad enough if it was limited to stupid stuff I have done in my 60 years of fixing boats, or even dumb stuff I see in boatyards, but, sadly, that’s not the case.
I would bet that a significant number of the gear failures, and a huge percentage of the leaks on boats are because the builder completed a bolted joint poorly. And that sucks when we consider that it’s bolted joints that hold fin keels on, and most every fitting on the deck and many on the rig.
While I would guess the most common bolted joint sin among yachties, yards, and builders is not using a properly calibrated torque wrench every time a bolted joint is put together, as well as checking the torque at least a couple of times afterward to take up creep, there’s another error that I have found in a couple of places on our J/109 that I suspect is all too common:
Like most owners with a new-to-us boat that is far from new, I spent the first couple of winters focusing on stuff that just had to be fixed.
This winter I have had the luxury of moving on to things that need doing, but are not immediately obvious. In this case torquing the keel bolts.
Out of interest, before removing the nuts, cleaning them up, lubricating (or not1) and then torquing to specification, I immediately torqued each nut with the wrench set to one third of specification.
