SC 17 Asymmetric Weather / Lee Helm

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kclo4
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Joined: July 19th, 2022, 2:09 pm
Boat Make/Model: Supercat 17

SC 17 Asymmetric Weather / Lee Helm

Post by kclo4 »

Hi all, I have read the thread by T Peterson on the exact topic and will refer to it, but I figured I would start a new one since this is a different user and boat.

I have a fairly new to me SC 17, I believe the marking on the starboard hull indicates it's a 1981. I am also pretty new to sailing with only something like 7 months experience, starting on a 20ft keel boat, but are partnered in the boat with an experienced sailor.

We are experiencing pretty significant weather helm on a starboard tack with light lee helm on port, pretty much exactly as T Peterson describes but I suspect our starboard weather helm is more significant.

Things that have already been done:
1. The starboard rudder had significant play at the roller stop side as well as the pivot bolt. I built up a layer of epoxy on the roller side and drilled out the pivot hole and installed a bronze bushing with 5/16" ID. There is some slop at the top but it's minimal now. Really it looks like the pivot bolt is in the wrong location preventing the rollers from engaging fully and I may press the bearing out, fill the hole and start over.
The port rudder had less slop in both areas. They both appear to rake under the transom with light rearward pressure applied. I believe I have the side to side slop within each casting under control.

2. I believe the shrouds and bridle wires are the same length. I measured them for replacement while the boat was on it's side. I don't know if I did it perfect but certainly within 1/4".

3. The rudders were repainted previously but the finish was not so good having speckles and heavy runs. I made an attempt at smoothing things over being careful to maintain profile. By eyeball template it looks OK But I didn't print out any templates or anything. On that topic, are the rudder hydrofoils public? I could actually print templates and work towards that.

Things that have yet to be done:
1. There is significant slop in the tiller arm double swivel to crossbar connections. Need to replace these with new yokes. Also planning on making some modifications to the crossbar to allow for adjustment. I don't believe toe is set correctly as there may be some tow out right now. I also believe any problems manifesting from toe or crossbar slop should present symmetrically not asymmetrically. This may not be right though if the amount of slop pulling from one tack is different than from the other. Thoughts? I will probably make a new topic on this part.

2. I am not entirely sure that both rudders are perfectly vertical with respect to the vertical line through the hulls. I may have to play with this.

3. I have not yet tried swapping rudders in each casting. The rudders actually don't fit as nice in the opposite castings but maybe I will just take some added slop from that to see how it performs.

3. I have not yet tried disconnecting the windward rudder from the crossbar while under sail to see how it feels. It's on the list. How useful is this?

4. I have not yet measured the crosswise distance from tip of hull to opposite transom to looks for hull misalignment. It looks OK but I know it could be subtle.

I will update as I collect more information but any help would be great.
Thanks!
Last edited by kclo4 on August 1st, 2022, 11:15 am, edited 5 times in total.
Matt Haberman
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Re: SC 17 Asymmetric Weather / Lee Helm

Post by Matt Haberman »

Hello,

Your experience with weather helm on one tack and lee helm on the other is not all that uncommon. You are looking at all the right things and I suspect you will find the problem with one of two things. Either one or both of your rudders are not symmetrical and the pivot point is not correct and the rudder tip is not raked forward enough. Since you have redrilled the holes I would focus on getting that corrected first. IF the problem persists then you need to look carefully at the rudder shape and see if it is symmetrical. Typically what you will see is one side of the rudder is flat whereas the other side has some shape, either concave or convex. Ultimately you will one both sides to be the same, if they are not you will have helm issues.
Matt Haberman
Aquarius Sail Inc.
http://www.aquarius-sail.com
kclo4
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Joined: July 19th, 2022, 2:09 pm
Boat Make/Model: Supercat 17

Re: SC 17 Asymmetric Weather / Lee Helm

Post by kclo4 »

Thanks Matt. I did add another point that I had sanded down a bad paint job , but it didn't seem to affect much, maybe a little less drag.
kclo4
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Joined: July 19th, 2022, 2:09 pm
Boat Make/Model: Supercat 17

Re: SC 17 Asymmetric Weather / Lee Helm

Post by kclo4 »

So this might be a dumb question but are the rudders supposed to be symmetric or specific to port and starboard? I have 1 with the extra partial down notch and one without.

Looking at them I am seeing some asymmetry in the profile. It sort of appears as twist rather than one one side being flatter.

I will switch the rudders in the castings and just see how it feels. Maybe the other slop and stuff will cancel each other out.
Matt Haberman
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Re: SC 17 Asymmetric Weather / Lee Helm

Post by Matt Haberman »

The rudders are identical, no difference between the port and starboard side.
The original super cat rudder had three notches, up, down, and a mid position for going out through the surf. I don't recall when the change was made to remove the mid position, but I'm going to say it was probably before 1982.
Matt Haberman
Aquarius Sail Inc.
http://www.aquarius-sail.com
kclo4
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Joined: July 19th, 2022, 2:09 pm
Boat Make/Model: Supercat 17

Re: SC 17 Asymmetric Weather / Lee Helm

Post by kclo4 »

Gotcha. I definitely have some warpage I think then. There is somebody in Florida with rudders that I can hopefully pick up.
Worked on the boat all day Saturday then sailed most of Sunday.

1. I redrilled the pivot hole on the rudder that was not allowing full engagement of the rudder lock rollers. The new hole is more perpendicular to the face than the old one. This rudder is definitely raked forward more in the locked position than previously.

2. Switched rudders left to right.

3. Tightened up the crossbar swivels by wrapping twine in the center to take up slack.

4. Bent the tiller bar on the starboard side to match the shape of the port. This ended up bringing the system from some toe out to about 3/8-1/2 inch of toe in, which I guess overshot a little in the opposite direction. Will be working on an adjustable system.


The verdict *drum roll......*
It's exactly the same. Neutral or very very slight lee helm on port tack and still heavy weather helm on starboard tack. Maybe it's a little less, but the wind wasn't that high. The force it takes to hold it in place ramps with wind, (or sail power anyway). The moments we were powered up and lifting a hull felt just as bad.
Really surprised swapping the rudders didn't result in a major difference. I did forget to try disconnecting the windward tiller bar from the crossbar to see how it changes. I think that would tell is if one rudder is really trying to freestream in a wacky direction.

So now I guess I am looking at trying different rudders or looking for a symmetry issue in the hulls/beams?
T Peterson
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Re: SC 17 Asymmetric Weather / Lee Helm

Post by T Peterson »

I'm kind of glad someone else has this problem...

During my testing I did switch the rudders from side to side and it made no difference. Starboard tack has acceptable weather helm, port has slight but unacceptable lee helm.

I have a little bit of slop but it is in each rudder.

I know that this boat, before me, had stern damage and it was repaired, very well. But, if both sterns aren't perfectly vertical, then one rudder will have a different rake. Normally, I would shim the rudder brackets where they bolt into the hull to change the rake a bit and see what happens, but someone, maybe me, glued them in with 3M 5200 or something else pretty hard. I think there are ways of cutting through it.

Your post revived my interest in fixing this. Last year, while out alone and trapezing the lee helm messed me up, I lost my balance, a gust knocked me over, I lost my glasses and fell off the boat. I managed to grab a rudder casting while the boat dragged me through the water at a pretty good clip. (The weather helm would have turned me upwind but the lee helm just kept me going.)

I thought I was going to have to let go of the boat (major sin and embarrassment) but I finally got it into my head that since I was hanging on to the rudder casting, I could turn the boat. I tried to turn it down wind and tip it over but that didn't work. I turned it upwind enough to get to the side shroud and pulled myself onboard but it was pretty hard because every time I let go of the rudder the lee helm turned us downwind and the boat took off with me trying to get to the side stay. I really don't want to go through that again.

I think a lee helm is pretty dangerous.

My plan now is to try and measure the stern verticalness on each side.
Then try to shim the bad side one way or another to get the lee helm rudder tip farther aft.

I'll let you know.
Matt Haberman
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Re: SC 17 Asymmetric Weather / Lee Helm

Post by Matt Haberman »

I suspect the issue in both cases is symmetry of the rudder profile...
I suspect both rudders are either asymmetrical in the same direction OR one rudder is symmetrical and the other is asymmetrical. This would result in Lee helm on one tack and weather helm on the opposite tack. This would also hold true regardless of which side the rudders we're Installed on.
You could try sailing with your windward rudder up and see if the symptoms persistent on both tacks. If it goes away on one tack then you know you have a good rudder. If it doesn't go away then you have issues with both rudders.
Matt Haberman
Aquarius Sail Inc.
http://www.aquarius-sail.com
kclo4
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Joined: July 19th, 2022, 2:09 pm
Boat Make/Model: Supercat 17

Re: SC 17 Asymmetric Weather / Lee Helm

Post by kclo4 »

So time to update this.

I was able to borrow a different rudder stock from another SC sailor but the exact vintage of that one was unknown. He hadn't sailed on it but it was in good condition.

Between my rudders and his I rotated it through in 2 different configurations but unfortunately it didn't appear to make a different and still resulted in weatherhelm on starboard tack.

I got new standing rigging rigging and chainplates from Tom. My chainplates were the old thinner design and twisted up, and rigging was of unknown vintage. That by itself didn't change the situation either. It did feel like I got more even mast rotation from any given shroud position setting.

Still trying to get another newer set of rudders, hopefully out of the vintage of the poor foam core.
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