May 14, 2013

The case for a collision mat

JUST ABOUT EVERYONE agrees that a collision mat is a good thing for a boat to carry — but very few boats actually carry them. The need for one is illustrated by the fact that a hole in the hull that you can put three fingers through will, if it’s near the waterline, let in about 80 gallons of water a minute.

If the hole is about 4 feet below the waterline, it will let in about 130 gallons a minute, which is more than any manual bilge pump can keep up with.

Taking things a step further, a hole near the waterline that you can put your fist through will admit 160 gallons a minute; placed 4 feet below the waterline, the same hole with admit more than 300 gallons a minute.

These are the kind of holes that might result from a collision one dark night with a balk of timber or a submerged cargo container. The only way to start controlling a leak like that is to block it from the outside.

You can make your own collision mat. A tarpaulin about 4 feet square with reinforced grommets at the corners will do the trick. Slide it on over the bow or stern and work it into position. Be sure to keep the lines taut when it gets near the hole or it may be sucked right inside. That tarp is also useful for catching rainwater, providing shade in the cockpit, and keeping rain out of open hatches, when it’s not being used in an emergency to keep you afloat.

Alternatively (and this is what most sailors fall back on) you could use a small jib or stormsail in place of a dedicated collision mat, but a mat is better, especially if you’ve practiced with it.

Of course, working a collision mat into place is not as easy as it sounds. Nothing on a sailboat ever is, especially if you’re on your own. And it won’t cure a leak, just slow it down enough so your bilge pumps can keep up while you make temporary repairs by stuffing the hole from inside.

Incidentally, the mat will work better if it’s on the leeward side while you’re drifting sideways. The pressure of the water will help hold it in place. And it’s obviously more likely to stay in place if you can stop the boat moving forward or aft.

Today’s Thought
One leak will sink a ship; and one sin will destroy a sinner.
— John Bunyan, The Pilgrim’s Progress

Flood damage to a game park in Texas has resulted in an extraordinary cross between a lion and a parrot. A park spokesman admitted yesterday that they’re not quite sure yet what they’ve got, but when it talks everybody sure sits up and listens.

(Drop by every Monday, Wednesday, Friday for a new Mainly about Boats column.)

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