Weather helm

[Bub]

After two sails with the SunDay Cat, my first Cat Rig experience I understand why there is so much discussion about how to deal with excessive weather helm by adjusting the centerboard up until the helm is balanced. But does the rudder angle require attention? I read it needed to be vertical and not allowed to ride up.. But would it also help if you rotate the rudder to the same angle as the stern and lock it down on that same reverse angle, toward the bow from the vertical position?

[Bob23]

What's up Bub?
  I have no experience with the SunCats (yet) but I cured the weather helm on my 1985 23 by doing exactly what you propose. I modified the rudder blade and installed a hold down bracket which sets the blade forward of plumb and it made a world of difference. Actually, a bit too much of a world, as I new have a neutral helm, which is not good. This year I'll tweak the mast back a degree to introduce some weather helm back in. Last year, she wandered a bit, took a bit of attention to keep her sailing in a straight line.
  There are lots of experienced SunCat guys here who will chime in, no doubt.
Bob23

[Bub]

 Thank you. Especially the warning that it's possible to overdo it.
I'm thinking if that happens, the quick cure would be to lower the CB incrementally until the sweet spot is located. Think I'll try that in light/moderate air. But do you think there is any downside to that experiment?

[Bob23]

Bub:
  No I don't  as long as you have a way to reverse the rudder placement a bit. As you know, the 23's have no centerboard so my only recourse is to shift the rig aft a bit or to tilt the rudder blade aft a bit. All in all, this has been a success and has increased the speed of the boat a little....could be my imagination but less friction at the rudder is a good thing.
  I should add that I use a custom built wood-sheathed foiled rudder blade which in and of itself, helped the performance greatly. Less rudder stall, seemed to point a bit higher and it looks great, too. I sheathed in a thin Okoume plywood, marine grade and fiberglassed it. It's held up well for 10 years now, give or take. I have some photos somewhere I can email you, can't seem to figure out how to here on the site although I suspect it's quite easy.
Bob23

[Bub]

Thanks. I'll give it a try. I have also seen the discussions about the rudder sheath accessory. I may purchase one after  I get more familiar with the current adjustments.

[Bob23]

Bub, forgot to ask if you have a foiled rudder blade?
Bob23

[Bub]

No, but I have seen it as an accessory. May try it after a few more shakedown sails with the standard rudder.

[Bob23]

Again, it makes a world of difference and all my rudder placement modifications have been using my foiled rudder blade. I can email you photos if you wish.
Bob23

[mikehennessy]

Hi Bob,

Please send me the photos also.  I'll be sailing my new Sunday Cat as soon as the weather breaks.  Snowed here last night!

Regards,
Mike

[Roland of Macatawa]

Hi, All:

Am following this discussion with interest.
I now own a 2012 SunDayCat which I have sailed for one season.
It has the factory original stainless steel plate rudder.
Am considering replacing it with a foiled rudder, but am undecided.
Reports of the foiled rudder being more effective at slower speeds and larger rudder angles are attractive.
Only boat of similar size with a foiled rudder which I have sailed, is a friend's Precision-18.

Best Regards, Roland

[Bub]

I thought I had read that there is a foil shaped sheathing product that can slide over the rudder, but I'm not sure. Does Hutchins sell such an accessory or is it another vendor?
Pictures would be great.

[bruce]

Hey Bub,

I haven't heard of a pre-made foiled sleeve product, the dimensions of the core would vary from boat to boat, making it problematic for a third party vendor. But that's basically the approach I used to foil the rudder on my PC. Starboard planks encasing the stock rudder. I believe the design is the same on the SC, the dimensions may vary.

The stock rudder is 1/4" thick aluminum, 12" wide. I decided to use a new core rather than modify my rudder, in case I wanted to go back. The new rudder was also to be 12" wide, NACA 0012-12. That shape results in a maximum thickness of 1 1/2", so 3/4" Starboard was perfect. I used a 9" core so the Starboard could extend 1" forward and 2" aft of the core for fastening and shaping the ends.

I roughed out the foil shape with a dado head on a table saw, tilted to follow the foil curve. There was a significant amount of hand shaping to fair the outer surfaces as you'd expect, with hand planes, rasps, files, and sandpaper. The Starboard machines cleanly, the biggest problem with hand tools was the static charge that would build up, and the shavings had to be cleared frequently.The Starboard was relieved 1/8" on the back to receive the core.

I considered several options to fasten the foil to the core. Starboard can be welded, but my tests with what I had on hand for heat sources weren't encouraging. HDPE isn't easy to glue, maybe West Systems G-Flex or a caulk could work, but I decided the I'd go with FH machine screws, countersunk on one face, tapped through the other. I could have used SS, the screws wouldn't contact the core, but I went with nylon. Plenty strong, easily cut off and shaped. Nylon will absorb some moisture, so continued immersion could be an issue, but I dry sail anyway. To fill the countersinks, I melted down some hot melt adhesive rods, stirred in some white pigment, and cast new rods to use in the glue gun. I wasn't really trying to get a perfect match, although it could be done, just get it close. The glue adheres well, is easily parred flush, but can be popped out if you need to dismantle the rudder. After a season, dry sailing, the hot melt fills are fine.

I had previously replaced the uphaul Com-Pac provides with a rod control system for the rudder, which is very effective (last photo). In the second photo you can see I'd left a tab, with the smaller hole, above the top edge of the Starboard where'd I planned on fastening the rod clevis end. The rudder had picked up 7 lbs. in weight with the foil, and that attachment didn't provide the leverage I needed to lift the rudder easily. I did some tests, and even if I attached the rod at the top aft corner of the Starboard itself, the leverage still wasn't right. I chose to add the arm you see in the last two photos, at some increase in turbulence.

Cost for this was basically $50 for the Starboard. The new core was another $50, but I could have cut down my rudder and saved that. A few bucks for fasteners and off cuts that I had on hand. But I enjoy making things, a foiled blade from Rudder Craft for the SC can be had for $375.

Back to your weather helm problem, as long as my rudder is held down firmly, and I haven't failed to reef if overpowered, I haven't had a problem. Besides raising the CB a bit, weather helm can be reduced by shifting weight forward. Easy to do in a nice big cockpit like you have in your Sunday Cat.

[Bub]

Bruce. VERY IMPRESSIVE, but above my pay grade!
Still looks like a useful modification for overall performance if I can locate the Vendor. I am very sure I saw one somewhere and just can't find it.

[bruce]

Please post it if you do find it, sounds very interesting.

Good luck with your weather helm. My experience with weather helm on catboats has been it is more an issue on boats with traditional barn door rudders, and much less so on boats with high aspect rudders like we have. I can recommend Bill Welch's The Competitive Cat: Racing Small Gaff-Rigged Catboats. Plenty of useful tips for experienced sloop sailors about sailing catboats in general, not just racing.

[Roland of Macatawa]

Bruce:

When you made your foiled rudder, how was the bottom edge finished? Was it encased in the Starboard? Was it flat flush with the bottom edge of the core? Because you made a new core, did the overall water depth of the rudder change?

Thanks, Roland