BYYB Forums

For anyone out there who may know, would increasing the width of the rudder from 11 1/4" to, say 14", do anything the vibration issue? Or is this just another issue that affects only a few?

Quote:For anyone out there who may know, would increasing the width of the rudder from 11 1/4" to, say 14", do anything the vibration issue? Or is this just another issue that affects only a few?

Changing the rudder brings its own issues - weather helm, lee helm, stalling and more. I would recommend that you go with the stock configuration and then play with alternatives. It only takes a minute to change rudder blades.

Of course, this advice is worth exactly what you paid for it.

I used the plans for my rudder and have no vibration at all. Mine is a Vacationer so the plans do vary. You might want to check the shape of the edges making sure they are the same on each side. I'll bet Paul will have some words of advice for you as well.

Keith

brit I will go with Richard on this one,build the stock first then the expermintal ones. I have built some real nice expermental rudders but the stock does the best all round job for me. I would also suggest you save your exp. rudders till early spring and you can make some real nice blue bird houses out of them, that is what I plan on doing with mine. I have noticed that most people that have bad vib problem have slack in the rudder usualy at the gudgens. This advice is worth exactly the same as Richards. :wink: Bud

Am I that predictable Keith?

Most all rudder issues can be sorted back to one of a few things that are easily checked.

How secure is it's mounting? Pintals slopping around in their gudgeons will cause some noise and/or vibration. There are a few ways to remedy this, one is to use a bushing and a recent post had a good photo of this idea, to insure the blade doesn't have any play.

Does the steering system have play in it? The lines in the steering system need to be under some tension to provide some feed back and to remove any sloppiness. Loose lines in the steering system will cause the rudder to "hunt" around between softer and harder areas of tension. Tighten up the lines.

How well shaped is the rudder? This issue isn't as important as some may think, particularly near the top of the blade at the intersection of the box and the surface of the stern wave, where the rudder's ability to "bite" is minimal. Lower down the blade, the effects of asymmetrical shapes can cause vibration. This one is harder to check, but if it looks "out" to the eye, it's probably pretty far off. I don't see this one as much of a concern at the speeds of a typical Weekender.

How much rudder deflection does the helm need to hold a course when close hauled? This is the usual suspect and difficult for the novice sailor to figure out, especially if this is their first boat. Your rudder should deflect (in the same direction the sails are flopped over on) no more then 5 degrees from the centerline of the boat. If it is, you're carrying too much weather helm which causes you to crank in more wheel (or tiller) to compensate. This stalls or partly stalls the rudder blade. In this state the rudder has a bunch of very turbulent water flowing around it (ventilation), causing the vibration (it should be smoothly flowing around). It real bad cases, sudden, temporary, lose of steering control is possible. This also seems to happen when you can ill afford to have a lose of control, like when coming into a dock or in the middle of a heavy air jibe. It's easily checked by noting where the tiller is in relation to the centerline of the boat, then checking this relationship with an angle gauge. Sail the boat on several close hauled courses, noting the location of the tiller, maybe marking the aft deck with some tape. Then at the dock or on the trailer, use a framing square or suitable thingie for angles, find the angles you needed to stay hard on the wind (close hauled) average them out for each tack.

This will be the amount of rudder deflection. I've seen boats carrying over 15 degrees of rudder angle, so don't be to alarmed if badly into the heavy end. If you are over 5 degrees (unless the winds were particularly heavy during the tests, pick a nice day) then some other issue is causing you to carry some weather helm. It's called "carrying" because when it's bad (weather helm) you feel like you are carrying the boat at the helm. Just ask any cat boat owner about stiff winds and their helm. It's normal for the "weight of the helm to increase as wind strength picks up, but most boats will be manageable until you need to reef, when the rig is properly balanced.

Weather helm is almost always solved with rigging adjustments. In a boat the size of Weekender, you can adjust weight(s) to correct minor needs, in fact you can steer the boat, just by shifting your weight forward or aft. This weight shifting also can help helm balance, many times being all that's necessary. Other things that can affect this balance are, mast rake and main sheet leads or tensions.

Playing with rudder shapes isn't a task I'd recommend for the budding designer. A good one is hard to do and most spend many hours getting it just so for a specific boat. Reducing it's aspect ratio (as you suggested) will decrease weather helm, but you have to know if you have excessive weather helm first, then decide if this is the fix you want, compared to some of the other options to rectify the issue. Of course there are other possibilities also.

Okay, I built the first one to plan:



Not really interested in redesigning the rudder, just wondering if some previously noted issues could be easily fixed. I may or may not play with it later, most likely not, unless it acts up.

Thanks,

Brit.

C'mon Barry, you have something to add... :lol: :lol: :lol:

I started out with my rudder shape just like the plans called for but eventually changed the leading edge to be round and the trailing edge is sharper, much like and aircraft wing but sumectrical. Haven't had any problems, seems to work just fine.

'nother rudder.... I started out with the designed rudder too.... THEN, I made the ol' sculling oar/barn door rudder because the water around here is shallow and you could not get the rudder down until you were way off the beach at low tide and I often go without a motor. I had trouble with stalling and weather helm before, it is tender but it doesn't stall and I have just enough weather helm that if I let 'er go she'll round up. Got rudder?

http://groups.msn.com/SandbarsandDriftwo...hotoID=599

I agree with what Paul has to say about it almost entirely.

I've had the opportunity to sail on a few Weekenders, all with minor differences and for the most part stock design below the deck level. First one was in Hawaii and 2-3' seas with froth blowing off the tops. Standard Jib, main reefed. Two miles to a headland protecting a bay to sail in. Helm felt as Paul has described, Heavy weather helm under these conditions. No vibrations in steering/rudder system at all. Rudder was offset a few degrees to maintain headway and once we cleared the headland and into more protected waters it handled quite nice. Still some weather nelm but not much and not much pressure on the wheel.

Couple others had major steering issues, from loose steering box to slipping line on the steering shaft and loose rudder in box to name a few. Major work to just sail the boats. They would both need quite a bit of work to get them tuned to handle well. One has had some of the changes made and I don't know about the other. But I won't go out on either of them again until they have been made.

One had mast angle off by about 9 degrees, (too much rake), once that was taken care of the boat handled well with stock wheel, rudder box and rudder. No vibration or handling issues. Mild to moderate weather helm but not a lot of rudder offset to maintain headings. Quite responsive to any wheel movement and positive reaction to rudder. Steering was tight with a turnbuckle on the tiller to the rope to keep it tightened. Simple clean system and once the stretch was taken out of the system it was great.

Couple have tillers, and one had vibration in the rudder. That was corrected by taking the slop out of the pintle/gudgeon in the manor I posted. Once that was tight everything was smooth. Both of the tiller steering systems are quite postive in their action and centering. In heavier winds, they both reqire a bit of offset to maintain heading with moderate weather helm. I've not experienced a "Heavy" helm on either of these. But both of the boats have well balanced sail plans with Lappers on both of them and stock main on one and loose footed main on the other.

Stalling of the rudder is a common experience on a these with most of the issues being related to too much swing on the tiller. Under these conditions the rudders do tend to vibrate or want to as they stall. The condition was corrected by installing blocks to limit the tiller swing to about 30-35 degrees either side of center and tightening up the slop in the system.

In shallow water situations like Angie has, her solution makes perfect sense. Other wise, school is out on thicker rudder with more foil shape or stock rounded leading edge and tapered trailing edge. Larger area or shape changes would be just asking for more trouble trying to find out what is happening with your boat.
Most importantly to me would be to get it out on the water as designed. Work with the stock system as designed to tune it and get the bugs out of it first. Don't be in a hurry to make a bunch of changes. Every boat is a little different and every boat will need its own "tuning" and minor adjustments to get things working well. Trying to build to take care of everyone elses minor issues to prevent them from happening on your boat is likely to cause you to have a whole bunch of other things going on that may take a lot more to correct or adjust to get working under your particular conditions and type of sailing.

Give it a season, try it out under as many different conditions as possible and gradually stretch the limits and push the envelope a little at at time. Once you learn what your boat is all about, then it is time to fine tune and make small adjustments that may or may not make any difference. What works for one may not work on another under different condtions at all.