Thursday, January 05, 2006

Ask the Tillerman #1

Dear Tillerman, I recently took up Laser sailing but I have enormous problems every time I try to gybe. My sheet gets hooked round the corner of the transom and I capsize.
What is wrong with this stupid boat?
Yours in anger and frustration
Tangled & Wet

Dear Tangled & Wet,
There is nothing wrong with your boat. As the folks at Microsoft might say, the design of the Laser rear end is not a bug - it's an undocumented feature. Your problem is something that is quite common among inexperienced sailors that have been sailing the boat for less than, say, 40 years.

First of all let me explain the physics of the situation. If during a gybe the mainsheet is allowed to trail in the water then the viscous drag of the water will be greater than the tension in the sheet thereby maintaining the sheet at a lower elevation than the corner of the transom with the inevitable result that as the boom transits across the boat the excess sheet will become ensnared under the cleverly designed wrap-over transom and will be pinned below it and as the sail fills on the new side the heeling moment of the rig will exceed the righting moment of the helmsman as you attempt to get your sorry ass over to the new side with the result that the rig will adopt a new equilibrium in the horizontal plane.

Several solutions have been suggested ...

Some experts will recommend rolling the boat as you gybe so that the old leeward side is lifted into the air as the gybe commences thereby preventing the sheet from falling in the water. Unfortunately this maneuver also raises the evil hooked corner of the transom into just the right position to catch the loose sheet during the gybe. As the boat is already heeled in the direction of the new heeling force then the capsize only happens even more abruptly.

Other so-called experts recommend sheeting in before the gybe to prevent having several feet of loose sheet that can trail in the water. This method was recently debunked by Steve Cockerill in his Boat Whisperer DVD where he points out that it is bad for the boat's psyche to sheet in when you want to bear away as it is sending the beast conflicting messages that will harm its self esteem. To make a boat bear away you should cluck, "Come on gee gee!" three times and ease the reins - I mean sheet.

No. The only safe method to avoid the dreaded sheet-round-the-transom problem is to wait until the boom is coming across and then grab the sheet as it exits the boom block. Hold the sheet as you cross the boat and you will take up the excess sheet safely and all will be well. Experienced sailors can even give the sheet a little flick after it is grabbed. With practice this will create a loop in the sheet that will wrap around the end of the boom and hold the rest of the sheet well clear of the water. Of course, once the sheet is wrapped around the end of the boom you have a slightly different issue to deal with ... but we do not have time to discuss that in this lesson.

Remember, practice makes perfect.



Anonymous said...

I've seen evidence of "undocumented feature" many a time. In fact I have been a victim of this unique feature. I gave up on Lasers a few years ago when going for a swim in the bay became less desirable. "Dude, the water is COLD!"

Stephen said...

To Tangled and Wet - welcome to the world of Laser sailing. Never underestimate the quantity of such features that this boat has to offer. A similar one, one that you will probably discover soon, is the dreaded capsize-to-windward on the run.

To Tillerman - it is not always necessary to grab the sheet between the block on the end of the boom and the block on the traveller. I manage to flick the sheet enough to prevent it hooking on the transom with only a well-timed-and-incredibly-energetic tug on the loose end, which was in my hand anyway. I've even managed to correctly form "the loop" (better known as "the noose") with this method!

There's only one way to learn to gybe, and that's gybing. At some point your subconscious will get tired of swimming and you will start to do it correctly.

Oh yes, and the golden rule: make the boat gybe on your own time, not the boat's.

Anonymous said...

I find that a slight tweak of the mainsheet when the boom is coming across tends to work with no other problems

Unknown said...

Just found this info 2 years after it was posted!

Great info and discussion. Thanks.

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