Yet another weather helm problem....

Technical discussion of ARC products
Mac M
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Boat Make/Model: SC17
Location: Lugoff, SC

Yet another weather helm problem....

Post by Mac M »

Trying to resolve this weather helm problem on my SC17. Here's what I've done so far after talking with Tom....

I replaced my tiller crossbar with a new one from Aquarius and have the toe in set to 1/8".
I've pulled my rudders and the pivot holes don't appear to be ovaled. (Picture below)

My next step is to adjust my mast rake. When I took the mast down the other day it appeared that it was raked back further than the recommended 5 degrees. Will this make the helm pull significantly?

The other possible issue I found was movement in the rudder from the top notch, ill attach a video. I have the parts to rebuild the lock down system that I ordered from Tom recently. Will the slop shown in the video be enough to cause the weather helm? I was thinking the new plastic rollers would be larger than the old ones and stop some of that movement?

When I got the toe in set I thought I had the problem solved until the wind started picking up. Once the wind came up the helm got pretty heavy and the need to pull on the tiller returned. I would hate for the problem to be the rudders themselves as they look to be in great condition and I just bought them! Advice welcome.

Here's the boat with the Mylar square top and jib I picked up from Franklin!
Image

Rudder pivot hole
Image

Top notch on the rudder, doesn't seem to be worn.
Image

Video

http://youtu.be/5-KDpz7PJnM

Video

http://youtu.be/iDUtuK7qAec
fjviola
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Re: Yet another weather helm problem....

Post by fjviola »

Mac
Weather helm issues have always been a mystery to me.
Somedays it is to port. Other days to starboard. And then no weather helm at all .. until the mullet start running in Galveston Bay and slap the snoot out of my rudders :lol:

Wish I had an SC17 down here in Panama.

Your SC17 looks Great and your Lake front is Fantastic!

Hope it all comes together.
franklin
Mac M
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Re: Yet another weather helm problem....

Post by Mac M »

I wish that was my lake front haha. Our 'saling club' shelter is located there.


Does anyone know of a way to check of the rudders have become flawed? Tom mentioned that the heat can warp them and even make a big swell on one side. Mine seem true to the eye but I've read that it doesn't have to be much of a difference to cause problems
Matt Haberman
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Re: Yet another weather helm problem....

Post by Matt Haberman »

Mac,

Mast Rake could cause the weather helm as could the slop that is shown in the video. Generally speaking both of those things will cause similar weather helm on both tacks. If the weather helm is always only present on one tack I would say that warping or symmetry of the rudder could also be contributing. It is also worth noting that with both the mast rake and the rudder slop it is quite likely that the problem would only manifest itself as the wind increased, where a warped rudder or a symmetry problem would likely show up under all conditions.
Matt Haberman
Aquarius Sail Inc.
http://www.aquarius-sail.com
Mac M
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Location: Lugoff, SC

Re: Yet another weather helm problem....

Post by Mac M »

It is present on both tacks. Am I correct to assume that the rudders should not move at all when locked down? I'm hoping the new plastic rollers will solve that issue. The notches on the rudder heads show no wear. If the new rollers don't tighten the slop up, what would be the best way to do it? Maybe brush a coat or two of gelcoat to add some thickness back to the notch?
Matt Haberman
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Re: Yet another weather helm problem....

Post by Matt Haberman »

Correct, there should be very little movement of the blade tip when in the locked down position. If the new rollers don't cure the problem you can add material to the cam groove to reduce the movement. Usually it is best to use a little fiberglass instead of just gelcoat. Regardless I would talk to Tom about the correct way to fill the cam as doing it wrong can make the weather helm worse.
Matt Haberman
Aquarius Sail Inc.
http://www.aquarius-sail.com
Tinkersailor
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Re: Yet another weather helm problem....

Post by Tinkersailor »

I too have been chasing a helm problem around my SC17 for a couple of years. This year I had an idea....measure the diagonals of the entire boat. To my surprise one is 3.5 inches longer than the other which means that one hull is ahead of the other making one shroud longer and one shorter.

Initially I had lee helm on port and tons of weather helm on starboard. It changed the shroud attachment points to compensate and the problem has been reduced.

Now I need to remove the beams and totally refer the beam beds in the hulls and put it back together dead square and level. So my question...how do you get a too inside the beams to undo the inner bolt? It's TIGHT in there!

Advice?

I was very surprised. My beams appear to be square and solid but someone must have messed up the set up before I owned her.

Leigh
Kevin Keller
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Re: Yet another weather helm problem....

Post by Kevin Keller »

Leigh,

Unless I am misreading your post.... I am trying to picture one hull being farther ahead than the other. I think the only way that would be possible is if saddles were put in the wrong place! If that is true you should be able to compare the distances from the tip of the hull to the saddles on each hull.

It sounds like one of the hulls is pointing in the wrong direction. I think maybe that could be caused by a couple of things. Maybe over the years the hulls have bent a little. Maybe your locating pins, if you have them have moved in the saddles. Or the locating holes were drilled wrong.

I think over time my hulls have bent a little inward but I am not sure. I have weather helm on both tacks.

I am not sure how to undo the bolts in your boat.

Kevin
Last edited by Kevin Keller on August 12th, 2014, 9:24 pm, edited 1 time in total.
Tinho Dornellas
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Re: Yet another weather helm problem....

Post by Tinho Dornellas »

I am new to this Forum and pretty green in catamaran matters, but I own currently 5 cats, and weather helm on any of them has been cured by decreasing mast rake. This moves the center of effort forward. Also I find most cat users around here use too little downhaul so when the wind increases, the CE moves aft, and therefore weather helm increases with wind strength. I am amazed at the fiberglass battens present on so many of the older cats, or so little attention paid to the shape of the battens- this also has an effect on the position of the ce and its movement aft when the sail gets loaded. What I say here is my perspective coming from the windsurfing world where I have extensive experience at high performance levels. With our sails we play to within 4 mm +or -downhaul to achieve vast improvements in control and better speed as consequence.
I hope some of this helps.
Tinkersailor
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Re: Yet another weather helm problem....

Post by Tinkersailor »

Tinkersailor wrote:I too have been chasing a helm problem around my SC17 for a couple of years. This year I had an idea....measure the diagonals of the entire boat. To my surprise one is 3.5 inches longer than the other which means that one hull is ahead of the other making one shroud longer and one shorter.

Initially I had lee helm on port and tons of weather helm on starboard. It changed the shroud attachment points to compensate and the problem has been reduced.

Now I need to remove the beams and totally refer the beam beds in the hulls and put it back together dead square and level. So my question...how do you get a too inside the beams to undo the inner bolt? It's TIGHT in there!

Advice?

I was very surprised. My beams appear to be square and solid but someone must have messed up the set up before I owned her.

Leigh
Ok DISREGARD! My boat is not out of square. Sorry, I must have made a measurement error. I have measured again. The whole thing is within 2mm of square and parallel. I did however notice evidence of a possible beam mounting issue. See below. I have attached pictures of my forward beam outside ends. Notice that the port beam protrudes approximately 1/2" beyond the position of the starboard beam. Is this indication of attachment problems? (Disregard middle picture it is rear beam for reference).

Regarding helm I guess I will need to rehab the rudders.

Leigh
Attachments
image.jpg
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Kevin Keller
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Re: Yet another weather helm problem....

Post by Kevin Keller »

Hi Tinho,

I understand the principle of reducing mast rake. My problem stems from putting a self-tacking jib on which I believe has a smaller area than the original sail. It's not bad enough to really bother me but it is not as nice when my helm was very balanced. I need to pay more attention to heading than I used to. I could reposition the location of my daggerboards but that would be a little more work than I have time for these days.

Kevin
cyberspeed
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Re: Yet another weather helm problem....

Post by cyberspeed »

We had the same issue when we added a screecher/reacher. I never had an issue before the screecher. We added a shim under each upper gudgeon and it solved the issue. Make sure the other settings are correct and your rudder assembly is not sloppy before adding them, because you will just be masking a setup issue.
Eric2101
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Re: Yet another weather helm problem....

Post by Eric2101 »

just curious but if you bring the windward rudder uo could you eliminate a toe issue?
Eric Arbogast
Supercat 15
Kevin Keller
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Re: Yet another weather helm problem....

Post by Kevin Keller »

Craig,
I must have missed your post regarding shimming the upper gudgeon, how thick was your gasket? Great idea!
Kevin
Matt Haberman
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Re: Yet another weather helm problem....

Post by Matt Haberman »

Just a quick comment on shimming the upper gudgeon. While it does change the angle of the rudder, it does not have the same effect as redrilling the rudder and thus may not cure your weather helm issues.
Matt Haberman
Aquarius Sail Inc.
http://www.aquarius-sail.com
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