Daggerboard position: Maneuverability VS. Acceleration

Rudders are designed to resist high angle of attack loads, load ascociated to 4° to 6° drift angle is not really a problem, and if you balance the rudder, you don't feel any weather helm !

 

Loading the rudder a lot Upwind with the force of the Sails is not bad, but good

A different issue is a rudder loaded by the HydroDynamic Yaw Moment of the hull, this is dangerous Downwind with large waves ... and even Upwind

---

Valkyrie II, the victim of The Satanita

The Satanita - Wikipedia https://en.m.wikipedia.org/wiki/The_Satanita

Roll --> Pitch --> Yaw

HydroDynamic Yaw Moment of the Hull
+
the Wind Force by its Leverage arm (= sine of the Angle of heel x vertical distance between the wind force and the lateral force of the water)

threw the yacht against Valkyrie, sinking Valkyrie and killing a crew member

 

(HydroDynamic Yaw Moment of the Yacht)

Suppose these estimates were correct...

if we do the Numbers, they turn out to be terrifying figures (Newtons meters) for the rudder.

 

The striking thing about this story is that it is a problem that appears in 1880-1890 and that appears again in 1980-1990

Let's remember Hiscock's first sailboat, Wanderer I, which was from the end of the 19th century, and then he had a modern sailboat from, say, 1930 that did not have the hydrodynamic problems of the sailboats of the 1980-1990.

 

"Suppose these estimates were correct ..."

---

But it could be even worse

since that estimate is from Roll + Yaw

and does not include Pitch

 

From 32 to 40

"Freaking Frustrating"

(And let's keep in mind that he is an English gentleman of moderate and restrained expression)

 

The funny thing is that many Tank Testing Models are 6 meters in length

And we have 6 meter models sailing in a magnificent Tank that has cost a fortune to build: the Atlantic

 

This model, for example, glided like a magic carpet flying over large waves and reaching a top speed of 20 knots, a clear sign that it dissipated the powerful forces of the Sea and the Earth in a good way.

Luckily, the navigator was an old retired sailor known for his precision, so the data from the experiment are good.

 

From 1979 is the article by professor Kensaku Nomoto of Osaka University, and when Andrew Claugthon got funding (by joining a group that investigated oil platforms) to create Waves it was in the early or mid-80s of the last century.

In short, everything is so disconcerting. The darkness of supertitions seems to be really powerful.

 

(thee little boats of Andrew Claugthon)

 

The little old modern (1930) boat

There is no mismatch between Center of Flotation, Center of Buoyancy and Center of Gravity

The bow tolerates pitch better

The bow does not produce a lot of High lateral pressure, and the yacht's Yaw moment is not very large.

The stern creates Low pressure, suction, vertical Suction, and the boat Surfs with an adequate Hull Attitude, stern Down; bow Up

 

The old hydrodynamic problems of the old 1880 yacht reappear in 1980 and, on top of that, the HydroDynamic center of a powerful keel is forward of the center of gravity of the yacht

 

My proposal for a modern yacht

Obey the Center of Flotation

Obey the Center of Flotation

Obey the Center of Flotation

And move everything (keel and mast) towards the stern to reconcile with the center of flotation

A bow capable of creating a lot of Lift based on High pressure, and a stern that helps trim the hull bow Up thanks to Low pressure, Suction.

 

-No, no way, I don't want to move the mast aft

-Well, okay, we welcome good traditions: your yacht will have a very wide bow and a fine, slender stern

 

Upwind

Upwind we have to fit four Forces

1) Force of Sail

2) Force of Keel/Centerboard

3) Rudder Force

4) Hydrodynamic Yaw Moment of the Hull with Heel/Roll and Yaw/Leeway (M, Max Michael Munk Moment aka "Munk Moment")

Max Munk - Wikipedia https://en.m.wikipedia.org/wiki/Max_Munk

Well, let's assume that we have already fitted it, and all the work is done

No

The puzzle is Upwind ... and... Downwind with Waves