Saturday, March 16, 2013

Bridge deck clearance and some old boats.

I'm a little strange I guess, because I enjoy walking around boat yards when I have some spare time.  On this walkabout I had several questions pop to mind, like when do you know you've left the boat in the yard too long? One possible answer, when a 6 ft tree is growing in the cockpit. Actually it's not quite that bad, the tree has grown up between the two long sitting boats. So I guess the real answer is, when a chainsaw is needed to make access for a travel lift:)
Or how about, when is it time to call it a day and dumpster a sailboat. Another possible answer, when then mizzen mast AND the hull are broken in half.

First a definition, on catamarans the structure between the hulls is called the bridge deck. This structure can be as simple as a Hobie cat tramp to the massive apartments as found on many larger cats. For real performance its necessary to keep this area between the hulls clear of obstructions.

Knowing the above then I have to scratch my head and ask what were they thinking with the following designs. Here are a couple boats that the average person would call a catamaran. But these couple of boats certainly aren't going to live up to the sailing performance generally attributed to catamarans dragging those center pod through the water. These boats were probably initially designed to carry those pods above the water by a few inches, but in the real world as soon as the between hulls bow waves get started those pods are in the water. Added to this basic design problem is that the average owner then fills these boats with every shore side connivence. The result is that most of these boats end up sitting well below their lines. So the pods are always in the water as evidence by the bottom paint.

And these final catamarans are just as poorly designed with respect the the bridge deck. It looks like a nice 36 inches, but quickly drops to about 10 inches. I can only imagine the pounding in any kind of seaway.

Low bridge deck clearance is a pet peeve of mine. I learned the hard way. My first big cat, a Catalac 10M, had about 24 inches clearance back aft and would pound so hard water would spout up the cockpit drains. Then my next catamaran, a Heavenly Twins 26, had a center pod and had to be kept nearly stripped to keep the pod out of the water.

And don't think this ridiculousness is limited to just old cats, here is a relatively new boat, a 2009 I believe. Not only is bridge deck clearance vanishing, those steps on the side of either hull certainly don't help performance.  The outboard is a nice feature if it actually lifts well clear of the water when sailing. Speaking of drives, there is nothing quite as absurd as a "sailing" catamaran equipped with that travesty called a "sail drive"in each hull. I'll rant on those some other time:)

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