Rudder question

[HenryC]

Why are after-market rudders such an improvement in performance?

Isn't a rudder just a rudder?  It seems to me as long as it is sturdy and long-lasting, and roughly the right shape, whether or not it is hydrodynamically tuned (a foil) should make little difference.  It seems the keel and hull shape does most of that work anyway.

And if they are indeed that much of an advantage, why doesn't Hutchins offer them standard, or as an option?

Just curious.
Hank

[Shawn]

"It seems the keel and hull shape does most of that work anyway."

Next time you are sailing lift the rudder out of the water.... what happens?

The rudder does quite a bit of work. Esp. when you are turning.

"whether or not it is hydrodynamically tuned (a foil) should make little difference."

Think about this when you turn the rudder. On a flat plate the rudder will create a lot of drag at a fairly shallow angle to the water flow. A foiled rudder can turn further with less drag. The foil will also generate lift (in the pivot direction of the boat) when it isn't head on to water flow. The lift also helps to pivot the boat or to fight weather helm.

"And if they are indeed that much of an advantage, why doesn't Hutchins offer them standard, or as an option?"

Hutchins offers them as standard on most (all?) of their current boats. And they sell them as an upgrade to earlier models.

Shawn

[Bob23]

Trust me, Henry:
  It made a world of difference. Any mine was designed and built by me so there are some inherent flaws in it. After I installed the new foiled blade, I was able to come about under mainsail alone. With the old flat blade, that was impossible.
 
   Not much of a photo but you can see the foil shape. My rudders biggest flaw: the blade is way too wide. The next one will be simpler: Fiberglass over foam or wood frame and much narrower.
I had fun building this one. I'm a wood nut so to have a wood veneered blade finished bright is a real treat. But it was a long process. 
Bob23

[HenryC]

Excellent answers to a dumb question.

[skip1930]

The young sailors in Sailing School at Sturgeon Bay, upon graduation must sail their last trip around the three buoys with out a rudder in the Optimum Dinghy they all trained on.

No small task to be sure and often times includes un intentional bumps. No foul and no penalties. It's all great fun.

I would suspect that if one could see the flow around a flat slab of aluminum versa a foiled rudder's flow; that many drag inducing 'eddy' currents could be seen twirling off the surface when water is flowing over a slab. Like air off the wing tips of aerocraft. Reduced turbulence saves gas.

Much like an aeroplane wing, there is a reason why the leading and trailing edges are not flat-slabbed edges. Unless your flying a F-117.

Gotta be smooth baby.

The other thing you guys who build your own foiled rudder may be missing is that some of the rudder is under and ahead of the transom with the IdaSailor Rudder, giving that rudder that feeling of power steering at the tiller. A balanced rudder. Again often used on aeroplanes to lighten the controls.

HenryC mentioned rudder protection-->Rudder protected by a skeg...

skip. Kind of an interesting boat below.. Either tiller or wheel for bad weather...

[HenryC]

The other thing you guys who build your own foiled rudder may be missing is that some of the rudder is under and ahead of the transom with the IdaSailor Rudder, giving that rudder that feeling of power steering at the tiller. A balanced rudder. Again often used on aeroplanes to lighten the controls.

skip.

A rudder that is hinged at the leading edge may be harder to turn than one where the rudder post is aft of the leading edge (that "power steering" you mentioned).  But it is also less vulnerable to damage from floating debris, particlarly if the leading edge is protected by a skeg.  Does anyone care to comment on the pros and cons of these two rudder design approaches?

[crazycarl]

our 1st sailboat was a bristol caravel. 22'.  it had an encapuslated keel much like our compacs, only deeper.  it had a foiled rudder the was pivoted about 2' forward of the transom.  you hardly had to have a finger on it to manuever the boat.


we also owned a starwind 19 with a foiled rudder that extended under the stern.  again, one could sail with a finger or two, and neither tiller had that vibration i get from our stock compac rudder



if i ever have $$$ for an ida, i'll get one.  i'm thinking about incorporating the starwind rudder to the compac, but i don't know what is in it's core.  it is about 2" thick and would have to be milled down.  if the core is only foam, it won't work.

[Bob23]

Along the lines of this thread, do you know of anyone who has converted a Compac 23 to an inboard rudder? My amatuar engineering mind says it's possible and even advantageous but that kind of thinking has gotten me in trouble before. It seems that all weather helm would be elliminated thus resulting in a faster and easier to sail boat. We could probably do away with the kick up feature of the rudder because it would not need to be deeper than the keel.
Any thoughts?
Bob23

[capt_nemo]

Bob23,

Ever thought of  decreasing weather helm by moving the total sail area center of effort forward by adding a bowsprit and either moving the working headsail forward or flying a larger headsail? Should work, and its easier than messing with a hole in the hull.

Just finished installing my homade bowsprit, bobstay, and whisker stays for my Sun Cat today. Now I have a platform to play around with various headsails to improve my boat's sailing performance.

capt_nemo

[Bob23]

Nemo:
   My 23  is a 1985 with a bowsprit. Weather helm is just inherent in the 23's. It is greatly reduced with the foiled rudder and new sails. If anything, a longer bowsprit might be nice. No reason I'd have to stay with the factory arrangement, eh?
Bob23