BRIDGE DECK CLEARANCE AND SLAMMING ?


On Catatonic's maiden voyage, it was blowing 25-30 knots right on the nose all the way to the keys, from Ft. Myers until we turned the corner at Yacht Channel.  Forecast said waves were 3-5 and then 4-6 all day.  Maintained 11-12 knots and was moored in Key Largo by 6:00PM that night.  No slamming and very comfortable ride but with a fair amount of spray.  But the spray didn't keep our friend Jewel from spending most of the day on the deck cushions.

Jim Kaufman
Catatonic, EndeavourCat 44


OK. Here's the poop on bridge deck clearance.

It makes a difference how far forward or aft you take the measurement.  The transom is the lowest point and also the least important point.  The farther forward you measure, the more important the clearance is.  As you get closer to the stern, the more the boat has already risen up on the wave.  So several things are in play here.  Probably the most important is the flotation of the hulls ahead of the bridge deck.  The sooner the boat starts to climb the wave, the less bridge deck slam you can expect.  Some cats tend to go through the waves and some tend to ride up and over.  Also overall beam and the distance between the hulls factor into it.  The greater the beam the more likely it is to slam .

Another factor is the speed of the boat through the water.  EndeavourCats tend to rise up by several inches when underway, and the faster you go, the more it rises.  This is caused primarily by the hulls acting like water skis.  So bridge deck clearance is by no means an absolute measure of the amount of slamming you'll get.  

Bottom line is that bridge deck clearance is more than adequate on all of the newer generation EndeavourCats (38, 40, 44 and 48). The older 36 design has much less clearance, which under certain conditions, can be a problem.  Endeavour minimized the slamming on the 36 by presenting to the waves a multi-faceted bridge deck which breaks up the wave so it does not hit the deck with full force.  This worked quite well, and while the 36 had pretty scant clearance, the slamming was less than other cats with more clearance.  Of course the ideal is to have more clearance, which they have done with the new generation EndeavourCats.  Having said all that, for the money, the sailing version of the 36 is still my favorite cruising cat.  The minimal clearance was not an issue over 99% of the time and the boat sails so well. 

Capm Woody
CharterCatatonic.com