Question about lateens (explanation in caption)
Posted by nestor_d@reddit | sailing | View on Reddit | 20 comments
I'm sure there's something I'm mising or misunderstanding, but here's my question: in my badly drawn top-view diagram of a sailboat, the red lines are two lateens, placed symetrically on each side (I know that's not how it's done). Yellow is the mast and green is the lines.
As I understand, lateens work by generating lift, like plane's wings, rather than just by being pushed by the wind. If I'm understanding correctly how they work, in this case, the lift sshould be generated in the direction of the two blue vectors. That would mean a resulting vector traight forward. Wouldn't this make for a faster, or at least more balanced sailboat?
OptiMom1534@reddit
Di anyone else think this was something else
kerberos824@reddit
I should call her.
BaggyLarjjj@reddit
Rub the bow as you are going into the companionway hole
Mad_Oats40@reddit
instructions unclear, dick stuck in daggerboard hole
314314314@reddit
La teens, sounds like a bunch of French girls.
bannlyst3@reddit
Is she lateena?
brouk111@reddit
Buy some book like RYA trimming sails
Westar-35@reddit
Let’s break this down a bit. Sails, any kind of sail, are wings in every wind condition except directly downwind (when the wind is directly behind the boat, pushing it). The keel is also a wing, and is a critical component you missed.
I’m glad you are thinking about vectors, but you want to think about it in terms of the fore/aft and side/side components of those vectors.
The boat here is white, the sails are blue, the force vector (and components) are blue, the keel and it’s vector (and components) are green, the wind is red, leeway is red even though the direction of water current from leeway is the opposite direction.
Most of the force from the wind is pushing the boat sideways creating a sideways drift called “leeway”. The current from that sideways drift and forward motion create lift on the keel that ideally balances against leeway.
Sorry for the 1 second drawing on my iPad, but it communicates what is needed albeit very simply.
Raneynickelfire@reddit
Only when it's a wing. A lot of them aren't hydrofoils.
youngrichyoung@reddit
Still a wing. Not because it lifts the boat away from the center of the earth, but because it lifts it laterally against the pressure of the wind
Westar-35@reddit
I think they’re referring to a full keel without a foil profile. BUT even the full keel would behave like a symmetrical airfoil but a horribly inefficient one.
nestor_d@reddit (OP)
The keel I'm assuming is the vertical stabilizer-looking thing (sorry, im more of a planes guy) that ships haave pointing downward right? It's the only part I cn think of that functions as a wing. But what is leewaay? even though I'm pretty fluent in english, there's some technical terms I don't know
CodeLasersMagic@reddit
Leeway is the drift of the vessel in the downwind direction. If you sail at 90 degrees to the wind then the actual path you take is more like 100 - you end up downwind of the point you initially aimed at.
Westar-35@reddit
Yeah, thats what I described, but I first wanted to set the basis of understanding of “lee” so the other uses of it would be more clear.
Westar-35@reddit
Yes, the keel would be the fin like vertical foil roughly in the middle of the boat.
The direction the wind is coming from is “Windward”, the opposite is “Leeward”. So you could be on the “Leeward side” of an island, which would shield you from the wind. “Leeway” is sideways drift caused by the wind. That sideways drift causes the keel to see a water current from the opposite side of the boat as the wind. Like, if you are being pushed through the water you’d feel an apparent current from your motion in the water. If you’re also moving forward in the water there’s a forward component of the water’s flow on the keel. As-in, if you are moving forward at 4kph, and you have a leeway of 3kph, you’re actually moving diagonally at 5kph. Now think of the keel as a wing with a symmetrical airfoil. Symmetrical airfoils require a positive angle of attack to generate lift. The diagonal current from the combination of forward motion and sideways “leeway” motion basically creates the necessary positive angle of attack to generate lift.
SnooRecipes1301@reddit
Is that where it is?
DemandNo3158@reddit
Build a model with rigid sails and post results. Good luck 👍
high_yield@reddit
In your diagram, which was is the wind coming from?
Same_Detective_7433@reddit
Only one of those sails would be generating any lift, the other would be being pushed backwards by the wind. If you are asking why not run two at the same time.
The wind needs to come across at the correct angle, and it is not straight into the front of the boat, it is about 30 degrees or more to one side or the other.
foilrider@reddit
Which way is the wind blowing in your diagram, and how does it create two opposite vectors on the two sails?