Jib Sheet angle

[Island Time 1,214]

Check out this on Quantum Racing;

I don't think I've ever seen a jib angle that small....

 

 

[Fish 0]

Its the latest thing apparently.

SA have been running photos of mains massively over-sheeted on premier boats like Quantum as well. My understanding (although likely very poor) is something along the lines of getting the main up means you can get the jib up further as well.

I don't understand the physics of it, but these teams have enough lectronics to tell it is an improvement to about 5 decimal places.

 

Slightly related but different, I've been trying to understand the 'apparent centreline' of the new beamy twin rudder boats. The ones verging on scow bow, but primarily the really fat bottomed girls.

When a beamy boat is heeled over on its chine, and only a single rudder of twin rudders is in the water, the centreline runs from the bow to one of the aft quarters, not down the centreline. That has to change the angle of attack of the rig, sails and keel. I know the angle of attack of the rudders can be adjusted very easily, but I haven't got my head around the rest of it. Luckily its not much of a problem on a classic kauri log...

I'll see if I can find a picture that shows what I'm on about.

[Fish 0]

Not the widest arse around, but this shot of the JPK 1080 shows the general principal of the centreline of the boat shifting out and on an angle from the bow to the aft quarter when beamy boats heel onto the chine. Surely this changes the angle of attack of the sail and rig?

 

Edit, or these two of Quantum Racing getting half the boat out of the water when heeled.

[Frank 157]

I wonder how they resist the tendency to round up with such close angles and beamy hulls/sterns.

The wider the hull the greater the lateral separation between the  drive of the sail  and the hull drag, at its worse when you are on the wind , less so when reaching.This force couple tends to make the boat want to round up more, I suppose you could argue that the heel angle moves the centre of drive to leeward compensating for this. Either way there must be some interesting design challenges for the naval architects but its all solved on puters I suppose. This wee trailer sailer used lee boards which would have been interesting for balance.

 

https://www.google.co.nz/imgres?imgurl=http%3A%2F%2Fwww.boatersresources.com%2Fimg.php%3Ft%3D1%26id%3D7518174&imgrefurl=http%3A%2F%2Fwww.boatersresources.com%2Fboat-for-sale%2F1993-RedFox200EGreatTrailerSailer-Used-482326&docid=by1Ap8EJCuDlYM&tbnid=WLlsC8vlMpnMzM%3A&vet=10ahUKEwjGkt3-iaPiAhUMT30KHW8oD-sQMwg7KAIwAg..i&w=599&h=401&bih=625&biw=1366&q=red%20fox%20trailer%20sailer&ved=0ahUKEwjGkt3-iaPiAhUMT30KHW8oD-sQMwg7KAIwAg&iact=mrc&uact=8

 

[madyottie 82]

Ok, I'm a bit late to the punch here, but surely moving the hull drag to leeward of the Coe would reduce weather helm? It shortens the lever from the rig, at least compared to a circular hull form, where the combined hull/keel drag moves to windward as the rig moves to leeward.

 

Then comes the issue of pushing that angled hull sideways through the water. I'm guessing the foils rotate slightly to weather to minimise leeway, so the trick would be in creating the right amount of lift without too much drag from the foil, versus the reduction in hull drag as it slides sideways through the water.

 

To my way of thinking, this would allow wider sheeting angles, hence more drive, for any given direction.

 

Although, I guess making the hull as skinny as possible would allow for narrow angles, as the shape is easy to push, which could lead back to...

 

Designing a very narrow hullform, replicating it for the other side, and joining them together with a flat wide planing surface.

 

But I still don't get the really narrow sheeting angles