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post #1 of 10 Old 11-07-2008 Thread Starter
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Weather Helm/Rudder Design

I have a question about my boat, a 16' Neport 16.

Background: It is a fractional rig and it actually sails OK in decent wind, but in low wind, when pointing, or in gusts it has a strong weather helm. It has a genoa, maybe 130-140%.

Here are my two theories on why that is.

1) The main sail is a little undersized, it could probably stand to be 10% bigger (just a used sail from Bacon sails, loose footed since it is a home made boom at the moment).

2) The rudder is undersized/bad design. OK, so I know a piece of 3/4 oak shelving eased on the front and with a maybe 1 inch taper on the rear is not optimal (obviously) but would this account for the very bad weather helm at times?

I am almost certain the answer is 2 as I am not a complete idiot I'd like to think and I plan on building a new rudder this weekend in any caes (1/8 ply laminated, fiberglass wrapped). I just wanted to throw it out there and see what people thought and maybe get suggestions on rudder shape/sizing.

Thanks.
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post #2 of 10 Old 11-07-2008
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Quote:
Originally Posted by tschmidty View Post
I have a question about my boat, a 16' Neport 16.

Background: It is a fractional rig and it actually sails OK in decent wind, but in low wind, when pointing, or in gusts it has a strong weather helm. It has a genoa, maybe 130-140%.

Here are my two theories on why that is.

1) The main sail is a little undersized, it could probably stand to be 10% bigger (just a used sail from Bacon sails, loose footed since it is a home made boom at the moment).

2) The rudder is undersized/bad design. OK, so I know a piece of 3/4 oak shelving eased on the front and with a maybe 1 inch taper on the rear is not optimal (obviously) but would this account for the very bad weather helm at times?

I am almost certain the answer is 2 as I am not a complete idiot I'd like to think and I plan on building a new rudder this weekend in any caes (1/8 ply laminated, fiberglass wrapped). I just wanted to throw it out there and see what people thought and maybe get suggestions on rudder shape/sizing.

Thanks.

I'd start with the rudder. Usually increasing the size of the mainsail will only increase weather helm.

There are other possibilities (like mast rake, for instance). A quick search of "weather helm" should pull up some recent threads.


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post #3 of 10 Old 11-07-2008
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IF it is a Newport 16 then there is lots of info about the boat and how things should be setup


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post #4 of 10 Old 11-07-2008
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Without sailing the boat its hard to say, but I would say of your suggested reasonsare the primary cause of your weather helmt. More likely the weather helm in a breeze is the combined result from having a blown out mainsail, carrying too much sail for the breeze, heeling too far, not flattening the sails adequately (increase tension on halyards, outhaul, vang, sheets, drop traveller, move jib lead aft one or two holes, and so on) and not pointing high enough or else over trimming the sails. The rudder might play a minor role only because it is front hinged rather than counterbalanced and the side loads increase with higher winds and its poor shape may mean that you are oversteering to hold course increasing the force on the helm. One simple way to correct weather helm is to slightly raise the centerboard.

BTW were you out sailing last weekend up by the Chester River?

Jeff
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post #5 of 10 Old 11-07-2008
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Weather helm - ah yes.

Because it is possible to sail and steer a boat with the rudder centered just by balancing the sails, then in theory, while the rudder can be an issue, the bottom line is the balance of the sails. It is certainly interesting and well worth knowing the "theory" of how sails work. But, for sure, two things a person should know about are the Center of Lateral Resistance (CLR) and the Center of Effort (CE). They work like a balance beam and when aligned sailing is more efficient.

Here is a small part from the Sail course offered by the USPS and the CPS-ECP.

Quote:
... weather helm exists when the center of lateral resistance (CLR) is located forward of the center of effort (CE). To correct excessive weather helm, you must move the center of effort forward or move the center of lateral resistance aft or both. To move the center of effort forward while underway:
  • move the mainsheet traveler to leeward
  • ease the mainsheet slightly, trim the jib flatter
  • hoist a larger jib or reef the main
  • reduce the angle of heel by shifting weight to weather
  • rake the mast forward

To move the center of lateral resistance aft while underway:
  • move weight aft, thus trimming more by the stern
  • raise the centerboard part way up
If these remedies do not work, the problem may be more fundamental. Permanent weather helm may be caused by:
  • the foretriangle being too small
  • the mainsail being too large
  • the mast being stepped too far aft
  • the centerboard being too far forward

If the remedies for excessive weather helm are carried too far, the balance of the boat will pass the neutral point and lee helm will develop. Obviously, lee helm is corrected by reversing these remedies.
From Sail, Copyright 2008 United States Power Squadrons, Sect 8, Balance

I hope that helps a little.

And yes - this is a plug for you to take a Sail course. My choice is the CPS in Canada or the USPS in the States but there are lots and lots of great courses out there being offered.

If you want to read an interesting article about balance on-line, here is one by John Ellsworth

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Last edited by rikhall; 11-07-2008 at 11:33 AM. Reason: added a link for people
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post #6 of 10 Old 11-08-2008
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Never liked the term at all.... damn sailors.
On a tiller, you pull the tiller toward the weather to counteract it.
On a wheel, you turn the wheel away from the weather to counteract it.
Try explaining that to a new crew.

We need to call it "round up tendancy", RUT, or something understandable.

Hence the term "You're in a rut".

Lee helm could be "turn away tendancy", TAT.

"You're in a tat" doesn't sound so good, does it?
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I was first going to suggest that it would be easier to reduce mast rake, to move the center of effort of the sails forward by tightening the forestay, than it would be to build a new rudder. From the sales brochure picutures on the website linked by Tommays, however, the rudder looks ridiculously too small. It could probably be another 8" to a foot deeper, though you probably don't really want it to stick down further than the fully deployed centerboard. The overall shape looks pretty straightforward to reproduce- it just needs to be extended. Before going to all the trouble of fiberglassing, it might be worthwhile to experiment with some trial rudders of different sizes, simply cut from a sufficiently strong sheet of plywood, that you wouldn't mind discarding afterwards. You'd want to cut and fiberglass a new, dry rudder after you've determined the right size. (You'd have to wait for the experimental rudder to dry out before you fiberglassed it. That could take weeks, and you'd still have to be concerned with moisture causing delamination and/or rot.)
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post #8 of 10 Old 11-13-2008
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if you build a rudder

https://www.sailnet.com/forums/gear-m...wport-30-a.htm

Then checkout this thread!
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post #9 of 10 Old 11-13-2008 Thread Starter
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Thanks for all the great suggestions. I ended up making a new rudder (starting at least) and it actually sailed a ton better. I have the info on a Newport 16 but I basically had no parts so was starting from scratch. I based the new one on the stock design, a few inches longer and a few inches wider though. The old one was smaller in both respects.

I think it was mainly the fact that my rudder had zero lift/bad shape and was basically not providing any balance. It still needs some shaping to get a little better lift but it is the ballpark of enjoyable sailing at this point. With the larger/better shaped rudder it points much better and makes much better speed upwind. It also makes a huge difference in light wind directional stbility, the old one stalled pretty quickly in light winds. It's a relatively small keel so I think the larger rudder helps to give more lateral surface area for upwind sailing.

I have been sailing on Lake Norman in Charlotte, NC.

I can't seem to find that link for the newport 30 rudder.
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post #10 of 10 Old 11-13-2008
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Url

https://www.sailnet.com/forums/gear-m...port-30-a.html

I am sorry that didn't work for you, try this again!
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