lev-o gauge placement question

[priceless9192]

does a lev-o -gauge need to be placed in the center of the boat? my friend has one and its on the port side of his boat but i think that it should be centered to be accurate, right?

[GreenLake]

Something like this?



As long as your DS is stiff (and not floppy like a partially inflated inflatable) all hull parts will rotate around the same axis by the same angle. Therefore, it does not matter where you mount it, as long as it's on a plane perpendicular to the axis around which the boat heels.

I should think the bulkhead on a DSII is close enough to a vertical for that purpose.

[jdubes]

I moved mine to the center so it's clearly visible from port and starboard. I found it difficult to see when it was on the port side.

[hectoretc]

And for those of us that don't know very much about anything...

How would a gauge like this be optimally used? Is there an ideal angle of attack that balances drive vs heel?

I surmise that since it only goes to 45 degrees each way, one should try to avoid exceeding 45 degrees? But since there aren't any Green, Yellow, Red areas, (like on a Jeep Inclinometer) that assumption may not be a relevant comparison.

Obviously 90 degrees is bad (we'll call that red), is 50 degrees bad, or just a step in the wrong direction toward bad?

b.t.w. my lake is officially frozen today... I wouldn't walk on it yet, but we're now counting down the days until ice-out.

[GreenLake]

The best angle of heel is 0°.

The orthodox reply would be that in most conditions, you want to sail your DS flat. And I see several reasons why that would be the correct answer.

The minute you heel your boat, four things happen.

1. The shape of the immersed hull becomes asymmetric
2. The wetted surface is reduced
3. The effective area of the CB is reduced
4. The effective sail area is reduced

The CB on a DS is, if anything, undersized, so reducing its effective area will make the boat drift faster to leeward. If you can keep the boat upright, by sitting out or hiking harder, you maintain larger effective sail area, and that gives you more drive force. Asymmetric hull shape will result in the boat trying to steer, adding to the weather helm. To correct, you need to give more rudder, slowing down your boat.

At really slow speeds, in light winds, many dinghies are sailed with an artificial heel (by shifting weight, not from wind pressure). This will reduce the resistance due to wetted area (something that you might not care about outside a race). Whether this makes any difference for a DS I haven't been able to verify myself - there's nobody nearby with whom I could do boat-on-boat trials.

Now, if you are already overpowered (not enough weight to keep the boat flat) then letting it heel a bit helps spill power. But at a cost of causing more leeway and requiring more rudder. You'd be better off letting out some mainsheet.

Back to the use of the gage: it's surprisingly hard to know when you are sailing completely flat. So the gage would be most useful near the 0° mark. Not much past 30° or so your rubrails and then your coamings will be in the water. At that point, you are going to be too busy to read small gages and would be better off keeping the water from rising higher on the lee side - something you can nicely judge "live" without the need for additional gadgets.

[jdoorly]

Generally sailboats have a particular heel angle that balances the many forces in a beneficial way. The DS seems to like very low angles and at some times small negative angles. Certainly comfort goes away after 15 degrees or so but boats are generally controllable to about 45 degrees; at that point the rudder is becoming ineffective due to its angle. I don't know exactly the angle but somewhere beyond 45 degrees water starts coming into the cockpit. Yes, avoid going over 45 degrees if you can. I have had a bunch of times when so 'in the moment' of flying over water at speed, keeping the yarns on the jib just so, enjoying a long gust and screaming like a rebel, that i later find a few gallons of water in the cockpit and think "where did that come from?"

Mostly I'd say of an inclinometer it's not the reading that's important, it's the remembering to flatten the boat when you see it and recall that's why it's there.

When the wind acts upon the sails there is a driving force component moving the boat forward and a heeling force component pushing the boat over. When you heel the boat some negative things happen (not mentioned above). if the boats waterline shape is not symetrical, and few are, or the boats very wide aft the rudder will start to come out of the water increasing the steering problems, the heeled waterline shape will now be less streamlined and the breakaway point of the laminated flow will move forward slowing the boat. There will be less sail area projected toward the wind and therefore less driving force, all that meat on the rail moves in closer to the center of gravity and is less effective, and , of course, the more heel the closer to capsize you are.

I guy called Czesaw Marchaj has written the definitive books on sailing theory, he's very interesting if you enjoy physics and/or want to win races.

[Alan]

"GreenLake:
At that point, you are going to be too busy to read small gages and would be better off keeping the water from rising higher on the lee side - something you can nicely judge "live" without the need for additional gadgets."

"jdoorly
flying over water at speed, keeping the yarns on the jib just so, enjoying a long gust and screaming like a rebel..."

Hmmm. In my first of two lessons in a Hobie 33, I was entrusted with a jib sheet. Before we got to that point, our guest captain, a friend of the owner, didn't respond to the owner's instructions to let out the mainsheet. The rail went under for a goodly while, and those of us on the lee side got our butts soaked. I thought that was how it was supposed to be, so I was woo-hooing and making jokes.

I really look forward to planing. I may though, since I'm sailing married, hold off on the rebel yells. Or not...

[TIM WEBB]

Best advice I ever got: sail with your head and eyes outta the boat ...

Gizwizzies inside the boat are just distractions. Par exemplar: I find myself looking less and less at the GPS I installed about a year ago that I thought would tell me more than I knew already. I thought I was wrong, but I was mistaken ...

[Mike Gillum]

I would highly recommend the Lev-O-Gage mounted anywhere centerline between the top of the centerboard trunk and top of the Cuddy Cabin.
Biggest reason is that even when you really believe you're sailing your DS flat you probably aren't.
I've had a Lev-O-Gage in just about every Thistle I've owned.
Over the years my crew and myself have started to come in from a full hike assuming we're flat or even heeled to weather only to find out we're still heeled 5-10 degrees to leeward.
Keeping your DS flat in just about every condition than a drifter is paramount as it allows the centerboard and rudder to operate at their maximum effect.
If the conditions are puffy it's even better to be healed 5-10 degrees to weather in anticipation of a puff as your DS will shoot forward rather than to leeward in the puff.
Also a great way to judge heel when running downwind as heeling to weather helps to reduce wetted surface area and project the Main.

[Mike Gillum]

I forgot to mention the Lev-O-Gage is a really cheap performance tool.
Next time you break that expensive Windex Windvane think about replacing it with a 15"+/- long piece of galvanized 1/8" Hanger Wire rolled into a half circle with a 6-8" piece of yarn taped to the end.
Really cheap, easy to fix, and I find a better wind indicator than the Windex.