Upwind-Speed or height from gusts?

N

Nicko

New Member
Just been reading a very long thread about true wind , apparent wind and boat speed that got me thinking...

When going upwind and a puff hits(apparent wind becoming more free) I can either, ease the sheet and keep sailing in the same direction and accelerate,trimming as I get faster - or - use the puff as a lift and head up into the wind gaining hieght, then bear off as the puff passes.

My feeling is that I would take the speed over the hieght because I don't need to make a potentially slowing course change.
What does anyone else think?

Cheers
Nicko
 
I always go for height, and try to gain a smidge of speed

sometimes I'll for for MAXIMUM height and crab to windward like nobody's business
 
you should definetly go for speed because you will gain more when you go on speed then you ever would going on height. However there are always exceptions like when you are trying to point to the windward mark or trying to get clean air but those are pretty much the only exceptions.
 
Ahh, so not as clear cut as I thought.
I have an emotional tendancy towards Ross's advice after spending a while living in Newport Beach OC(The Stag rocks[if it still exists]), and spending time on Balboa(well, my friend's grandpa has a beach house there but got very cross when I pulled a cali chick and stayed out all night in Newport,ended up marrying her,coming back to the uk but now divorced,[Jane Doe] if anyone knew her, but I digress)
But then, 'I break things' idea seems more logical.
Any other opinions?
Cheers,
Nicko
 
Wait! You're both right! It's a drain clog remover AND a mouthwash! :D

The thing that's gone unspoken is the wind speed.

In light air, I'll take all the speed I can get and Betty Boatspeed's going to walk all over Peter Pincher.

But once it's breeze on, there's not much additional speed gain to be had, so it's time to work to windward.
 
I'd say the opposite - countless times I've got so much speed from powering through gusts that I've slid down to leeward of a boat in front, then tacked and passed ahead. I'm talking about when it's really windy though...

You just have to play it how you see it - if the conditions are such that taking height will slow you down too much, then go for speed (choppy etc). If you can take the height without losing too much speed - take the height!

But NEVER pinch when it's REALLY windy kids, I WILL sail through your lee!
 
LaserBen said:
But NEVER pinch when it's REALLY windy kids, I WILL sail through your lee!
Click to expand...

And I can agree with that too.

I remember one time taking a sight on my competitor upwind against the shoreline beyond.

Then suddenly, he took a great phenomenal leap forward -- it was like the afterburners had kicked in for two boat lengths.

How did he DO that?

Well, naturally, he DIDN'T. What happened was that I slipped sideways two boatlengths. You couldn't feel it or see it. It was only in comparison to the range on the other boat that we could tell that it happened.

And so we learned about flow over the keel, and keel lift, and stalling the foils.

Pinching. It's a disease. The first step is admitting you have a problem. ;)
 
'Stalling the foils', Could someone explain this term so I can get my head round the physics?(not too complex please)

Cheers
Nicko
 
Q: How do airplanes fly?
A: They use wings.

Q: So do they have to tie the airplanes to the ground so they don't flow away?
A: No, wings only create lift when there is a flow of air over them.

Q: How do they create lift?
A: The air has to take a longer path over one side vs. the other, and therefore flow faster.

Q: So you create that special wing "Foil" shape for that right?
A: Right, but you can also use a flat shape, angled against the wind. This is called angle of attack.

Q: Huh?
A: Driving down the highway, stick your hand out the window, so that your hand is flat -- parallel to the highway.

Your hand is exactly parallel to the direction of travel. It has no "angle of attack."

As long as you hold your hand completely flat, the air doesn't try to force it up or down. Now, tilt your hand so that the leading edge is slightly higher than the trailing edge. That creates an "angle of attack" because your hand is now pointing a slightly different direction than the direction the wind is coming from.

Do you feel how your hand is being lifted? This illustrates how angle of attack creates lift, even in the absense of foil shape.

Keep increasing the angle of your hand. Two things happen:

1. The "backward" force keeps increasing. As the angle of attack increases, drag increases.

2. For a while, as you increase the angle, up to a certain point. The "up force" increases as you increase the angle but:

3. BEYOND a certain point, the up force stops, and all you have left is the "back force."

When you get to step 3, the "angle of attack" is too great, and the foil (your hand) is STALLED and no longer creates up force.

Q: So what does that have to do with boats?
A: Water flowing over the centerboard/keel and rudder creates lift in the same way. This lift is what allows boats to sail to windward.

Q: So how do I create this "angle of attack"
A: The angle your boat is travelling is slightly different than the angle it is pointing toward the wind. The more you "pinch up" slowing down and increasing the angle of attack vs. the direction you're travelling, the more you increase the angle of attack. That's why pinching works. But go "too far" and just like the air over your hand, the water stalls over the foils and you slip sideways.
 
bjmoose said:
Q: How do airplanes fly?
A: They use wings.

Q: So do they have to tie the airplanes to the ground so they don't flow away?
A: No, wings only create lift when there is a flow of air over them.

Q: How do they create lift?
A: The air has to take a longer path over one side vs. the other, and therefore flow faster.

Q: So you create that special wing "Foil" shape for that right?
A: Right, but you can also use a flat shape, angled against the wind. This is called angle of attack.

Q: Huh?
A: Driving down the highway, stick your hand out the window, so that your hand is flat -- parallel to the highway.

Your hand is exactly parallel to the direction of travel. It has no "angle of attack."

As long as you hold your hand completely flat, the air doesn't try to force it up or down. Now, tilt your hand so that the leading edge is slightly higher than the trailing edge. That creates an "angle of attack" because your hand is now pointing a slightly different direction than the direction the wind is coming from.

Do you feel how your hand is being lifted? This illustrates how angle of attack creates lift, even in the absense of foil shape.

Keep increasing the angle of your hand. Two things happen:

1. The "backward" force keeps increasing. As the angle of attack increases, drag increases.

2. For a while, as you increase the angle, up to a certain point. The "up force" increases as you increase the angle but:

3. BEYOND a certain point, the up force stops, and all you have left is the "back force."

When you get to step 3, the "angle of attack" is too great, and the foil (your hand) is STALLED and no longer creates up force.

Q: So what does that have to do with boats?
A: Water flowing over the centerboard/keel and rudder creates lift in the same way. This lift is what allows boats to sail to windward.

Q: So how do I create this "angle of attack"
A: The angle your boat is travelling is slightly different than the angle it is pointing toward the wind. The more you "pinch up" slowing down and increasing the angle of attack vs. the direction you're travelling, the more you increase the angle of attack. That's why pinching works. But go "too far" and just like the air over your hand, the water stalls over the foils and you slip sideways.
Click to expand...

Great explanation - bravo that man!
 
Well done Moose and thank you,
I have it now - Don't point too high too quickly or the foils will stall, obvious now I understand the physics!!!

Maybe a moderator could put Moose's post in the FAQ section.

Cheers
Nicko
 
Here's the picture I was trying to post earlier:

attachment.php
 
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