Another Rudder Thread

[Jim in TC]

So one of the last days in our slip this season along comes a fellow who just purchased a used Sun Cat with the Ruddercraft rudder (which we also have). He had been out maybe once or twice as I recall, and commented that he wondered if the new(er) rudder was not really big enough for the boat. Since, on our last sail of the season in substantial winds, our rudder lost effectiveness in heavier gusts I started to wonder the same thing. To regain control we had to spill wind from the sail (we would have been well served with a reef, but really only on the bigger puffs).

So the real question would be, is the stock rudder from ComPac any bigger than the Ruddercraft replacement? Since the newer ones are foiled, that is no longer an issue as I understand it.

[bruce]

I look forward to the replies from SC owners regarding the size of the rudders in question, but that's exactly how I would describe the feel of the rudder when the boat is overpowered, and past the time to reef. I notice it most dramatically when I've been sailing off the wind, for comfort, and I come into the wind, typically to prepare to drop the sail. The weather helm, not a problem in milder conditions, can be profound.

[Jim in TC]

I contacted Gerry at Hutchins. The stock rudder is still a flat aluminum (not sure where I got the idea they had changed to foiled).

Stock rudder measures 37" x 12", 34" from pivot to end. Ruddercraft (at least ours) is 38" x 10 1/2", 34" pivot to end. Not a lot of difference, but "swept" area is comes to a bit less. I think there is a thread about impressions of the difference between the way the two rudders perform that I need to search out. Or feel free to chime in here!

[bruce]

Thanks for the follow up. I was wondering about CP going with a foiled rudder.

Bub did start an nice thread about rudders and weather helm back in February '19.
https://cpyoa.com/forum/index.php?topic=11263.0

If anyone had the chance, it would be fun to hear of a few Sun Cats getting together, some stock and some foiled, doing head-to-head testing. You could play with rake as well.

[Roland of Macatawa]

Bruce,

Thanks for linking us back to Bub's thread on Weather Helm (and Rudders).
I had remembered posting there when I was researching the Ruddercraft replacement rudder.
But was unable to find that thread again. Glad you did.

Was discouraged at the end of that thread where the head of Bub's Ruddercraft replacement blade didn't fit well and had to be modified.

JIm in TC,

I believe, although I have no empirical proof, that the differences of the two style of Ruddercraft replacement rudders is significant.
The kick-up rudder assembly, like yours, has the leading edge of the foil aft of the pivoting axis.
The replacement blade-only, like Bubs, positions like the factory blade with about 12% of the chord forward of the pivoting axis.
That forward balance will tend to reduce a bit the helm load, by reducing the 'self-straightening' effect when pivoting the rudder from center.

The two Ruddercraft foils also have slightly different hydrodynamic profiles.
I posted details scattered somewhere in the thread Bruce referenced.
But my recollection is that the replacement blade-only has a slightly longer chord length and a greater width.
I'll try to find the details again, if you are interested.

Regards, Roland

[Jim in TC]

Roland, if those details come easily to hand I would be interested. But I think it would take a fairly significant difference to motivate me to change the rudder (again). Thanks, Bruce for linking the rudder thread...I was going to search around today and now here it is!

[Roland of Macatawa]

Jim in TC, Others:

I gathered some comparative data about various SunCat rudders;
Com-Pac factory stock, Ruddercraft replacement blade, Ruddercraft replacement kick-up assembly.

Most of this was reported at various times in the previous Weather Helm thread.
But Assembled and Summarized here in this table:

Edited to add Ruddercraft Item Names

Regards, Roland

[Eddie C]

Years ago I had Suncat which I replaced the rudder on with the Ida - blade only. It performed significantly better than the stock plate rudder. In 2017 I purchased a 2015 Sundaycat. Since Ida had changed and no longer supplied the foil without the entire assembly, I ordered an aluminum NACA foil section from England (about $80 with shipping). Using a wet tile saw I cut a 2 inch section out of the rear of the original rudder below the pivot point. With a grinder, I rounded the edges to enable the sleeve to fit over the cut down original. It was a very tight fit requiring lots of hammering. Empty spaces were filled with styrofoam and ends sealed with epoxy. After 4 seasons I am still very pleased with the performance. The rudder is balanced and the Sundaycat has no tendency to round up regardless of wind strength or amount of heeling. With no weather helm to fight there is no breaking effect from the rudder - the speed benefit is substantial. Without a direct comparison I can only speculate but suspect the aluminum rudder is faster and better performing than the Ida. My attempts to attach photos were not successful. If anyone is interested I can e-mail pics.

[Roland of Macatawa]

Eddie C:

I find your comment about your rudder to be informative:
"The rudder is balanced and the Sundaycat has no tendency to round up regardless of wind strength or amount of heeling.
With no weather helm to fight there is no braking effect from the rudder - the speed benefit is substantial."

Would like to see pictures of your rudder.
Do you know what foil profile your rudder is?

Note, when I post pictures, they do not show for me in the preview, but do appear when posted.

Regards, Roland

[Eddie C]

Tried again to send pics - error message said file is not supported (using an iPhone). Roland, I sent you a PM.

[bruce]

Yah, .heic files don't work. You need to convert them to .jpg, or something else compatible, .png, .pdf...

Please do, I'd like to see you photos!

[Roland of Macatawa]

Attempting to post aluminum foil extrusion rudder picture forwarded by Eddie C

[Roland of Macatawa]

More from Eddie C

[Roland of Macatawa]

Some more from Eddie C

[bruce]

Thanks Eddie and Roland.

I recall seeing these before, and was intrigued by how they shortened the cord, when necessary. Cut off the trailing edge and mount it inside to brace the open seam. Fortunately, no need to do that on the SC.
www.windknife.com

Here's the link for the product at Duckworks, and an article that may be of interest.
https://www.duckworks.com/product-p/wk-parent.htm
https://www.duckworksmagazine.com/15/howto/windknife/#.X8d-HC3MxBx

I wonder if it's possible to use this without trying to seal out the water. Maybe end caps for appearances and reduced turbulence, but drainage holes so the water can drain readily. If you wanted to avoid the foam and fiberglass.