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Author
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Topic: Rudder vibration
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piper576
Member
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posted August 06, 2004 11:30 PM
   
I noticed the other day while out for a short sail ( force 4 winds ) that I have developed a vibration ( almost a chatter ) in my Tiller.
I do not use a bungee setup instead I have a solid line. I cant seem to see a reason the fittings seem good, could it be to tight because of no bungee stretch or does it happen when ever you sail just under the main because of misbalance ???
Any ideas has anyone else noticed itBob IP: 209.226.190.126 |
Eric
Member
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posted August 07, 2004 01:03 AM
Sorry, not me.Where you heeled heavily? Was the tiller heavy(lots of weather helm)? I assume you've checked the pintles and gudgeons on both boat and rudder. I wouldn't think the "kick up" line should cause vibration. In a heavy wind, I'd want all the rudder length I could get! Having a non stretch line here, will keep the rudder down! Interesting circumstance Bob. Eric IP: 130.63.85.93 |
2short S565
Member
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posted August 07, 2004 09:38 AM
I had this happen only once.
I was motoring with sails up in Batchewanna Bay and all of a sudden the boat slowed like the keel was draging in sand. Then boat sped back up. My rudder started to vibrate and I could here a knocking on the bottom of the boat. I figured something was caught on keel or keel was badly damaged so I screwed it up into the boat and back down. No change.
Got to dock but had trouble docking into the tight spot available, because my keel was up at that time. Backed away from dock while I screwed keel down. As looked up to go forward again I saw a large section of fishing net in the water ahead of me.
So I had snagged a net and ripped a large piece of it and dragged it across the bay with me. That caused turbulance under the boat that caused the rudder vibration. The plastic floats on the net had caused the light knocking on the hull(there was no marks at all tho).IP: 67.70.4.223 |
2short S565
Member
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posted August 07, 2004 09:49 AM
Also check the mounting bolts on the gudgeons and pintles on both the rudder head and the transome. My transom bolts lossened up once before. Now they have fender washers and nylock nuts.
I also replaced most of the screws in the rudder head with thru bolts. Those won't ever be a problem again.
Is the rudder blade pivot bolt reasonably tight? Under force the two sides of the rudder head can spread causing too much clearance to the rudder blade. The blade might then wiggle. I tighten my pivot bolt until the blade is just able to pivot freely.
Is the tiller bracket on the rudder head tight? I had heard of one case where a guy had his come right off!
FredIP: 67.70.4.223 |
piper576
Member
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posted August 07, 2004 09:57 AM
Eric - not alot of weather helm , and the pintles and gudgeons on both boat and rudder seem good ( not sloppy at all ) - My crew ( wife ) decided to stay down the bay at a relatives wind was gusting to 20-25 knots and she doesnt like heel or surprises so I was short handed comming back I wasnt heeled heavily running only the main eased out in gusts2short S565 - yes that may have been my problem weeds caught on the keel or rudder, thinking back I did go through a weed patch down near the bottom end of the bay. I never thought of that and it would have cleared itself when I raised the keel coming in.
Thank you both for the input -- Bob --
IP: 216.209.120.119 |
Ken
Member
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posted August 07, 2004 09:58 AM
My guess was that it's turbulence around the rudder. When you go fast with not too much weather helm the tiller will sing (vibrate) in your hand. That's when you know that you're having FUN!
Examine the rudder shape. The trailing edje should be filed off slightly flat....and not have a sharp edge.[This message has been edited by Ken (edited August 09, 2004).] IP: 69.158.140.154 |
elmet3
Member
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posted August 08, 2004 04:34 PM
I have experienced this exactly one time, and it was this weekend. It occured when we were moving along pretty quickly on a beam reach and I felt the tiller vibrate slightly. No noise, and it didn't last long. I thought it was just resonance set up by speed and perhaps peculiar conditions of water flow, but, I sail in a weedy lake and I had cleared the keel several times. I remember thinking I still had weeds on the keel or on the rudder just before this happened. I rebuilt the entire rudder head last winter with all new wood and throughbolted everything. I am certain there is minimal clearance and everything is stiff. IP: 152.163.253.103 |
Canadian Sailor
unregistered
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posted August 14, 2004 01:57 PM
I've experienced hull humming when planing during my bronze IV and V in Lasers. Also heard it in a Hunter, and a Petrel. From what ppl have told me, it signifies the max speed you can attain with the wind you're in (don't know if true), I don't remember any tiller vibration though.------------------
Canadian Sailor 
"Before you criticize someone, you should walk a mile in their shoes. That way, when you
criticize them, you're a mile away and you have their shoes." [This message has been edited by Canadian Sailor (edited August 14, 2004).] IP: 216.209.110.186 |
Captain Mike
JuniorMember
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posted August 20, 2004 11:52 AM
Piper,What you are referring to is called "cavitation". Cavitation can occur with the rudder and/or centre board. It is caused by turbulence in the water as if passes over the rudder/centre board leading and trailing edges. If you were to ever see a true racing boat such as a 470 for instance you would notice that the trailing edge of the rudder and centre board is almost razor sharp and the leading edges are perfectly smooth and rounded. To eliminate you cavitation problem you would have to examine your rudder's leading and trailing edges for imperfections. If there are any smooth them out. You want the water to travel at smoothly as possible over the surfaces. The faster your boat goes the more chance for cavitation. Hope this helps. IP: 209.162.248.29 |
Canadian Sailor
unregistered
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posted August 21, 2004 07:52 AM
Interesting.IP: 216.209.110.118 |
