Optimal Heel Angle

[sailorboy1]

An Aspiring Boat Bum dissing a highly regarded boat designer with a post that adds nothing to the topic............now THAT'S SILLY!

I await my moderator PM!

[perchance]

I'm new to most of this so I hope my questions make sense. When the boat is heeled, is more of the hull is exposed to the wind contributing to leeway? I was taught that heeling allows the wind to spill off the top of the sail. If this is so how does this affect the boat?

[Bash]

Originally Posted by hummingway

The OP did specifiy the boat the question was for, so prehaps not such a silly question?

There is certainly a practical side to the question. On our boat, we call the inclinometer the "fun meter," and my wife keeps a wary eye on it when we have guests aboard. If I get anywhere close to 20 degrees of fun, she'll suggest that we reef. And the rule on our boat is that if either of the owners thinks it's time to reef, it's time to reef.

While 15 degrees of heel seems to be a good rule-of-thumb starting point for boats such as the OP sails, a more accurate way to judge the point where steps should be taken to flatten out the boat would be the rudder angle. A lot of fin-keel skippers use 10 degrees of rudder as the point where there's too much weather helm. Of course, the way to reduce weather helm is to reduce heel.

Bob's point is well taken, however. I'm faculty advisor for my university's sailing team, and almost without exception the boats who fetch the weather mark first in any regatta are the boats that were sailed the flattest. Those boats will out-point the rest of the fleet without losing any speed to them at all.

[bob perry]

Ok, let's back up a bit.
Picture all the pics you have scene of high perfrmance racing dinghies. Some even have trapezes. The crews clearly want a zero angle of heel.

Now think of any TP52 with it's entire crew hanging over the rail to the rule's limit. They clearly are working towards a zero angle of heel.

Then, just for shits and giggkles, think of a Star class boat, or an Etchels, or a Soling with the crew hiking it's hardest, within rule limits, to get the damn boat on it's feet. They clearly do not want the boat to heel.

Jee whiz, go back to the J boat RANGER and look at all those paid hands lined up on the rail. They are trying to reduce the heel angle.

Do you think they did this becaise it made for a dramatic photo?

Anyone serious about boat speed does his best to sail the boat flat.

Now, in very, very ,light air you can use some heel to help the sails droop into their sown in foil shape with the help of gravity. You can also alter Cp with some heel and trim angle changes for better light air boat speed. You can also use trim changes to reduce wetted surface.But this is dinghy stuff and it's not reasonable to apply it to Mom and Pop 35'ers. Sure, get the bow dow in the light stuff, pointy end in and fat end out. That's fast.

So carry on with your "optimum, heel angle" discussion if you like while I search for the web site where the "angels dancing on the head of a pin" discussion rages on.

[claudius2000]

Zero angle of heeling is the number I strive for!! I cannot sleep, drink, etc. in peace otherwise.

[heyyou]

I agree with bob. If I may add,even in the same design there are to many variables. How clean the bottom how old the sails whats your coarse, are you racing the list goes on and on. Once in the water it's not so much science, optimal depends on to many variables.

[Sailmonkey]

I spent 5 years dinghy racing in college. Then entire time I hiked my butt off to keep a flat boat, the reason?, it's the optimum heel angle. 0. When sailing a bene 411 the same concept applies. however since you don't have trap wires or 20 rail apes to keep the boat flat you compromise. What's the most comfortable with the most ACCEPTABLE speed. period. You can sail flat all day long, but you may not go anywhere, you can sail on your ear all day long, you might be really moving through the water but not in the direction you really want to go. And just like all things sailboat we must compromise one for the other.

[bob perry]

Damn it Sailmonkey, I think you actually learned something in college.

[cfarrar]

There is an exception. Some hard-chined dinghies provide optimum VMG to windward with a slight heel, which allows the chine to create additional lateral resistance. It's the exception that proves the rule.

[daddle]

Originally Posted by Bash

...almost without exception the boats who fetch the weather mark first in any regatta are the boats that were sailed the flattest.

So they should take the sails down?

This is why I say heel angle is the result not the indicator. Those boats were not just the flattest, they had:

The most weight on the rail.
The best trimmed, most efficient, sails.
Were driven the best.
etc...

The determined, perhaps unconsciously, that they had enough power for the conditions and needed no more. So they set the sails accordingly. They would have sailed at 30 degrees of heel if that's the power they needed for the conditions.

[cal40john]

Silly me, I thought we were talking about at what point you had to depower to not slow down, or reduce vmg if going upwind. Anybody else under that delusion? I guess I always automatically insert "max" heel angle.

John

[NotQuiteLost]

On my boat (not much like the OP's boat, but still) the point of diminishing returns is somewhere around 15 degrees. The helm starts to act up, my speeds start to diminish relative to the extra power all around me in the wind and waves, and frankly it starts to get more difficult to handle or relax which is generally anathema to a cruising approach.

I do like how Perry explains exactly what most of us understand intuitively, but didn't really recognize until he smacked us upside the head with it Good show, Bob.

[bob perry]

Cal 40:
You have a good point there and that is a complex question. Some boats like to be pressed hard and others like to keep the rail well clear of the water. I don't think there is any way for a designer to determine that other than standard VPP data and at the edges that can be suspect.

The only way to determine how hard you can push the boat and see increases in VMG or boat speed is to race the boat.

I'm still trying to figure it out.
Give me another 50 years and I'll have it.

[SweetSerenity]

Originally Posted by Saucy Sailoress

It depends what you mean by 'best'. Toe rails in the water is most fun - and it gets even more fun if I can plough into a wave whilst Skip is on the fore deck. That's what I aim for, anyway!

Oh Yeah!!! Rails in the water baby!!!

Woo hoo!

[roverhi]

Bob, it's my understanding that the flat bottomed, plumb bowed, fat assed boats need to be sailed flat for optimum performance. A largish angle of heel with this type boat gains you nothing in water line length, the immersed hull shadows the keel reducing it's performance and the side of the boat because of it's flat bottom is just digging a hole in the water. An older design with slacker bilges and/or or a less flat bottom will probably sail faster with some heel but only up to a point. These boats tend to have overhangs that increase water line with heel, the keels are not a high aspect ratio foil so aren't as negatively affected by heel and the slack bilges don't present as much resistance to forward motion as their flat bottomed brethren.

So if you are sailing a dinghy or big boat designed with an underbody that looks like a dinghy, sail it flat. If your boat is more traditional some angle of heel is important to optimum performance. In any case, a heel angle much beyond 15 degrees is going to give negative reusults but only sailing a boat will find the optimum trim. I've been sailing slack bilged boats for so long, I don't feel comfortable unless the heel angle is 15 degrees.

As far as weather helm, it's not that big a thing if you are maintaining hull speed. My current boat develops a painful weather helm and verges on loss of control as it's speed approaches 7 knots. If I trim out the weather helm, lose at least a knot of boat speed. Once again, it depends on the boat. A spade rudder is a very finicky instrument hard to keep at the optimum and prone to severe stall is pushed too far. The rudder on a full keel boat will probably have a lot of work to do to counteract the hull induced weather helm and probably never completely stalls out so weather helm goes with the beast.