Sunday 4 June 2017

'Laser Ketch' rig

To balance the rig better, we tried a laser 4.7 rig at the back.


For those unfamiliar with this rig, it uses a shorter bottom section of mast, with a slight bend to put the centre of effort of the smaller sail in the same place as the normal one, when used on a laser. That's why it's tipping back. It looks a bit silly and I should move the mast foot to keep the masts parallel, but it worked.

We had a nice sunny day with the force 3 that's typical summer weather at our lake, with a few gusts up to force 4. Liz's boyfriend Mathew joined us, which I think is only his second time sailing. With an extra willing pair of hands, carrying everything down to the beach and rigging up went faster than usual and we were soon afloat and chasing a Laser2000 that was the only other boat out. Most of the time we were similar speeds, in the gusts we were slightly faster but he was much faster to tack.

We discovered that I could cleat off the aft sheet and Liz could balance the sails and even steer with the fore sheet, leaving the steering oar for when we needed to steer quickly or tack. Mostly we'd tack without the oar, just letting the fore sail go and allowing the boat to round up into the wind, then backing it to force the nose around. Backing both sails on opposite sides also spun the boat usefully but we didn't usually bother.

I could speed things up with a few strokes of the oar but it wasn't really necessary. Using the oar to steer around a tack required it to be on the right side, and it's quite unwieldy to move around so I mostly left it on one side. It could still be used very usefully to row the boat around once we'd slowed down. The oar isn't as good as a rudder for normal sailing. While it is now quite powerful and precise, and doesn't twist or bend (much), the handle end is at about shoulder height and can catch on the boom. When I was standing up in the aft cockpit it feels great. When I was sitting on the hiking bench or safety ama I could still reach but it's a bit high for comfort and I don't have the range of movement that I'd have with a tiller extension. That said, the ability to scull, and to row the boat in a circle are huge benefits that I wouldn't have with a rudder.

I'd made a new off-centre board from 2x4s, cut in half to make 2" blocks, planed smooth, switched around to alternate the grain direction and spread the knots around, epoxied and shaped with an electric plane. Other build-logs make this sound like a huge amount of work - maybe they used a hand plane because it only took an hour or so to form the aerofoil shape. It did generate a huge amount of wood shavings though - I filled my 50lt dust collector and blocked the hose a few times. The finished board is about 40mm thick in the middle and feels immensly strong so I see no need to glass it, just a coat of Woodskin. I turned the old steering oar into a second paddle and Woodskinned the steering oar. Did I meantion that I love Woodskin?

It's hard to say how effective the centreboard is, but there's clearly a fair bit of force on in when we're sailing so it must be working!  Putting it down when it's to windward was tricky as its handle wanted to jam under the gunwale. I had to put my foot on the far end of the board and push it down and under the boat, which created a lot of spray and a noticeable amount of drag. Once down, this board created a lot less spray than the old one.


Back to the sailing: we tacked up to the top of the lake and then goosewinged back down for lunch. Running with this rig was lovely, fast and effortless. The two different sized sails didn't quite balance and needed a small amount of correction from the steering oar. We tried putting more weight on the ama side but it didn't help much - I'm surprised how little drag the ama has, even with 3 meters of leverage. Liz tried to balance the boat with the ama flying, so we alternated between dragging the ama, flying it, and dragging the safety ama for a while, but there was very little affect on the steering. Surprising, but nice.

After lunch the wind had risen a bit and we needed two people on the hiking seats to stay level, and the safety ama saved us several times. There's no warning when the ama lifts unless you're actually watching it or watching for gusts. It's quite a gentle process, taking about a second from the sudden quiet as the ama leaves the water to the safety ama touching down on the other side. Initially the safety ama rides along smoothly, but as it gets deeper it splashes more.

Here are a couple of short video clips that Mathew took:

https://youtu.be/zl5cHORcUcs
https://youtu.be/EUeRqE9pf1w

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