Weather helm

[bruce]

I kept the depth the same, didn't feel a need to change. As you can see, the core is exposed on the lower edge. I considered encasing that too, but I don't have a perfect seal along the fore and aft edges so I knew water would get in there. I considered cutting in some drainage channels in the Starboard, and still could, but so far I don't see any corrosion issues.

[Zephyros]

Hi Bruce,

Amazing craftsmanship, you are very talented. I'm afraid that may be beyond what I would like to tackle and have looked at the two replacement rudders offered by Rudder Craft, could you please share your insight with us on the pros and cons of each of them:

Com-Pac Sun Cat High Performance Foiled Replacement Rudder Blade ($375)
https://store.ruddercraft.com/index.php?route=product/product&path=181_29&product_id=135

Com-Pac SunCat High Performance Kick Up Rudder Assembly ($599)
https://store.ruddercraft.com/index.php?route=product/product&path=181_29&product_id=136

[Roland of Macatawa]

Bruce:
Thanks for all your comments!

Zephyros:
I too am considering those two Ruddercraft replacements.
But am leaning towards the replacement blade rather than the entire rudder/tiller assembly.
Have asked Ruddercraft for more detail about the blade, and am awaiting their reply.

Regards, Roland

[bruce]

Hi Zephyros,

I have little first-hand experience Rudder Craft products, but I do moderate the Yahoo Picnic Cat Group and several members there have installed the replacement blade (same one as the CP 16) and liked it. Of course they had spent $295, in their case, so they were predisposed to give it good reviews. Made of HDPE, as is Starboard, so should be durable and easily maintained. I did see a post here regarding a bent blade, not sure how that worked out. I see that Rudder Craft does offer a lifetime warranty to the original purchaser.
http://cpyoa.geekworkshosting.com/forum/index.php?topic=11063.0

I don't know of any full rudder assemblies on a PC, but I did run across a guy at the ramp who had an older sloop, about 18', with one. I don't remember much about the boat, although I did note that he was sailing without a motor, credit for that. He said he liked the rudder, performance wise. He did point out the damage that was caused when the rudder dropped to the pavement as he was trailering the boat. Wore away the bottom edge. Since them, he'd been holding it up with a bungee as a back up. I don't know if this was an isolated incident or not, but I'm sure you're checking the reviews.

I can rationalize dropping lots of money on my boat. I'd considered the Rudder Craft blade, but didn't really feel the stock rudder was holding me back. Since I like to DIY, I investigated what it would cost to foil the stock rudder. When I found the Starboard on Ebay for $50, that was sufficient motivation to give it a shot.

Full disclosure, do I think my foiled rudder is an improvement, yes. But I wouldn't say I notice a big difference. I did do it off season, so to be fair I should mount the old rudder for comparison. It would be fun to try it head to head with a Rudder Craft blade, if that ever worked out.

[Zephyros]

Hi Bruce,

Thanks for your reply and insight. The post by BellaCat is scary to see the Starboard bowing like that, makes me rethink Rudder Craft. It sort of looks like BellaCat's is the taller Kick Up Rudder Assembly. I wonder if the shorter Foiled Replacement Rudder Blade has the Aluminum attachment plate running the full length to strengthen it, my best guess from the photo is no, you only see two rivets and there is a shadow that runs down to a little less than half way.

Roland,

Thanks, I look forward to what you hear from Rudder Craft, maybe you can get to the questions I mention to Bruce when you talk with them.

[bruce]

I'll be interested to hear any feedback from Rudder Craft.

Looking at BellaCat's photo again, the rudder looks fairly thin. It may just be perspective from the camera, but anything less than 1 1/2" seems light, even with a stiffer core. Foils with a cord of 12" typically have 1 1/2" thickness to be effective at the low speeds we're talking.

[Roland of Macatawa]

Zephyros, Bruce:

RudderCraft misread my inquiry.
Although I inquired about their Foiled Replacement Rudder Blade #BladeCPSun,
they replied about their Kick Up Rudder Assembly #KUCPSun.

Note that the Kick Up Assembly appears to use a rudder blade different than the Replacement rudder blade.
I have made a follow-up inquiry, and am awaiting further reply.

Copy of their reply about the Kick Up Rudder Assembly follows:

Thank you for asking about our Unifoil Kick/Up Rudder.

I'll start with dimensions and materials.
The rudder head and gas strut are stainless steel.
The rudder blade is HDPE (High Density Polyethylene),
and the included tiller is laminated white ash and dark mahogany.
The rudder blade for that boat is 1.25" thick, chord 10.5", and overall length of 48"
(roughly 11" in the head, max. draft 37").
The total weight including the tiller is 31 to 32 lbs.

The big advantages are the rudder is shaped to an airfoil shape of NACA 0012,
which provides the maximum lift with minimum drag.
Customers tell us it is like adding power steering to their boat.
The gas strut holds the rudder down while sailing until you hit something,
and then allows the rudder to kick up without damage to anything,
and when you clear the obstacle resets the rudder automatically.
It also holds the rudder blade up (vertically)
when you use the one line uphaul/downhaul system
to lift the rudder for launching/retrieving and trailering the boat.

If I can answer any other questions feel free to write or call 208/375-2204.


Regards, Roland

[bruce]

Thanks, Roland. They confirm they use the NACA 0012 foil, with a chord of 10.5" on the full rudder assembly.

I have a scrap of 3/4" Starboard, 19" x 3", that for yucks I compared earlier in its stiffness to a similar piece of white pine. I supported both at their ends and applied weight at the centers. The Starboard deflected about twice as much as the white pine. Although somewhat flexible, at 1 1/4"+ the Starboard seems suitably stiff IMHO.  A stiffer core would help of course, as would the apparent shorter and wider dimensions of the replacement blade.

[Roland of Macatawa]

Bruce, Zephyros:

I got today a little information from Ruddercraft about their replacement SunCat rudder blade #BladeCPSun.

Quoting:
Our blade is designed to fit into your existing head.
The blade is a little different is size as ours has a hydrofoil shape and is sized accordingly.
The blade is 25.25 long, 1.5 inches wide and has a cord of 11.75 inches.
The plate (which attaches to your head) is 11.75 inches high and made from 3/8 alum.
This gives you an overall height of 37 inches.
The overall weight is about 18 to 20 lbs
The 3/8 alum plate is wrapped in a high density plastic (HDPE), which is shaped to provide the hydrofoil.

Note that the hydrodynamic foil shape is different than their kick-up rudder info in my earlier posting.
Longer chord, Thicker maximum width.

Of course, I replied with more questions. I'll keep you updated.

Regards, Roland

PS. Are you aware that there is a lengthy posting on the TSBB about installing a Ruddercraft Com-Pac 16 Kick-up Rudder assembly onto a Com-Pac Legacy?
https://forum.trailersailor.com/post.php?id=1471491

[bruce]

Thanks, Roland, good info. I'd go with the replacement blade, but I'm happy with my hold down.

[DanM]

On the other hand, there is this:     https://store.ruddercraft.com/index.php?route=product/product&path=181_29&product_id=136

[Roland of Macatawa]

Bruce, Zephyros:

There is a feature of these rudders which I have not yet commented on.
That is their 'balance', meaning where the leading edge is positioned relative to the steering axis of the rudder/tiller.

First, my flat plate SS factory stock rudder is partially balanced.
It has a 'chord' of 12 inches.
Of that 12 inches, approximately 1+1/2 inches is forward of the steering axis,
for a nominal balance of ~12%

Second, the Ruddercraft kick-up rudder is unbalanced.
Its entire blade, when down, is aft of the steering axis.
The leading edge itself is just slightly aft of the steering axis.
This can be seen in the photograph on their website.


Third, I have asked Ruddercraft for more complete dimensional information,
to determine how their replacement blade will be balanced
if/when mounted to my existing rudder head.

Would be pleased if it has similar balance to my factory stock rudder.
Note: Designer Dudley Dix suggests a balance of approximately 15%
in a recent Small Craft Advisor magazine issue #115, page 42.

Regards, Roland

[bruce]

Thank you Roland for bringing Dix's current 3 part series into the discussion, the third part dealing with rake and aspect will appear in the next issue of the SCA, rake ironically being the first issue that Bub questioned. Dix discusses balance in the first part of the series, but states that with a longer tiller a zero balance may be better than the 15% he typically targets. (Note the TSBB post they reference mentions an overly long tiller.) In the second part of the series, where he addresses foils, he isn't clear if or how foiling the rudder effects the balance. I suspect it might, as much as the increased leverage of a longer tiller does.

I elected, in my naivety, to balance my NACA 0012 foiled rudder consistent with Com-Pac's offering. I feel no significant change in the helm, it retains a slight tendency to round up as desired. Nobody, including Ruddercraft, is rigorously testing rudders on the SC platform. It's all rather subjective I'm afraid, and probably the best decision would be based on taking these things for a test drive, if that were in any way possible. It would be fun to compare these things on the water!

[Roland of Macatawa]

Bruce, Zephyros:

Our discussion has drifted away from Bub's initial question into discussion of rudder detail.
I'd like to comment on Bub's initial question since we apparently have the same hull, rudder, and sail.

Bub:

It appears my SunDayCat has the same rudder as your SunDayCat.
Raking the rudder forward will lessen the tiller load on your hand, because it 'balances' the water flow over the rudder. It doesn't greatly effect the tendency of the hull to turn into the source of the wind; in fact it will slightly (probably unnoticeably) aggravate it by moving the center of effort forward relative to the sail.That turning-into-the-wind tendency is determined primarily by the lateral centers of effort of the hull and of the sail. What is commonly done is raising the pivoting-to-the-stern centerboard which moves the lateral center of resistance of the hull aft a bit relative to the sail, reducing the tendency of the boat to 'weathervane' into the wind.

All that being said, I sail my SunCat with the rudder raked forward. The tiller loads onto my hand are reasonable.
It was configured that way by the delivering dealer to the original/prior owner and has not been changed.
I also keep the centerboard slightly raised.
If I wish to heave-to, lowering the centerboard and releasing the helm causes the boat to turn into the wind.

I am considering getting a hydrodynamic foiled rudder, but will experiment a little more first with what I now have.

If you have access to Small Craft Advisor magazine, be sure to reference designer Dudley Dix's 3-part series on rudders: issues Jan/Feb 2019, March/April 2019, and upcoming May/June 2019.
I am looking forward to the upcoming issue which promises to discuss rudder aspect ratio and rudder rake.
Probably will not even consider purchasing an alternate aftermarket rudder until after reading the upcoming article.

You are welcome to reply to me here or directly, if this prompts other questions.

Regards, Roland

[bruce]

Roland, your rudder is raked? Didn't see that one coming. It would be useful to know the details of the modification, and how the helm compares to an unmodified rudder.

Dix is quite clear that fixed design factors effecting helm balance are so interrelated that empirical testing is critical, and made more so by variable factors such as weight distribution, CB position, and wind and sea state. Nothing against raking, but there's no reason the boat couldn't be designed to use a plumb rudder. We haven't heard complaints of excessive weather helm by other SC owners, raked or not.

Bub, if you do rake the rudder, based on Bob's experience, I would strongly suggest that you install a variable stop so the rake could be adjusted over a range, or backed out entirely, once you had a chance to try it.