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sail611

Pulsing in rudder/tiller

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Racing yesterday on a new to me Tartan Ten.  While on most points of sail, I noticed there was a pulsing of sorts in the rudder/tiller.  There was not any excessive helm, though the boat felt slow, and indeed was as we got passed while reaching by other Ten's (which is unsurprising due to the amount of turbulence I am sure was coming off the rudder).  The crew could see the tiller moving as I was driving, and could feel the pulsing through the hull.  The boat has never done that before, so I am somewhat concerned.  

Before racing I did go below and set the key way on the prop shaft, and put the transmission in gear, so it seems unlikely it was an issue with the folding prop.  

I went for a swim at the dock to check for growth on the rudder, but didn't see any.

We did tension the uppers one turn above our base, and left the lowers really loose.  

So the only thoughts I have are that we picked up a weed on the rudder while sailing (would that/could that cause a significant disturbance as we observed?) Or is the integrity of the bond between rudder and rudder shaft compromised?

Is there anything else that could cause such a disturbance in the rudder?

Thanks.

 

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I'd still suspect the folding prop. Did you put the tranny in gear before you set the keyway? The prop may need stronger, cleaner flow than it used to in order to reliably fold, especially if it's been a while since your last haul and inspection/lube.

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Okay.  I believe I did put the tranny in gear before setting the key way.  But then put it back to neutral to turn the shaft when I went below.  Then put it back into reverse when I went back on deck.

Being as the tranny was in gear, I don't think the prop could spin, but you are thinking maybe it didn't fold, and I was getting turbulence from the open blades?

 

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A good size weed or piece of 3 ft piece of rope will flutter and vibrate the hull....

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Okay, I knew weeds would slow the boat down, but wasn't aware of the extent to which they could vibrate a hull.  So Occam would tell me that I most likely had a weed on one of the foils, and it came off somewhere between the race course and the dock.  

I will pay close attention to the helm next time I sail the boat, hopefully in a couple of days, and if those symptoms are gone, I will assume weeds.  If not, I'll be back.

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10 minutes ago, sail611 said:

Okay, I knew weeds would slow the boat down, but wasn't aware of the extent to which they could vibrate a hull.  So Occam would tell me that I most likely had a weed on one of the foils, and it came off somewhere between the race course and the dock.  

I will pay close attention to the helm next time I sail the boat, hopefully in a couple of days, and if those symptoms are gone, I will assume weeds.  If not, I'll be back.

Could easily be weed, a plastic bag, a school of Coney Island Whitefish or something else.  Did you ever back the boat down to shed crap from the keel/rudder?

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Didn't back down during the race, and afterwards turned the engine on to get back to the dock.  Of course with the prop turning there was all sorts of pulsing in the tiller.  I checked the keel and rudder for weeds once we were tied up at the dock, but didn't find any.  If it was a weed or other foreign body, it came off somewhere between the race course and the dock.

I will know for sure next time I sail.

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2 hours ago, sail611 said:

Okay, I knew weeds would slow the boat down, but wasn't aware of the extent to which they could vibrate a hull.  So Occam would tell me that I most likely had a weed on one of the foils, and it came off somewhere between the race course and the dock.  

I will pay close attention to the helm next time I sail the boat, hopefully in a couple of days, and if those symptoms are gone, I will assume weeds.  If not, I'll be back.

The rudder will be shedding vortices especially upwind or reaching - kind of like the video below: which would tend to excite any weed wrapped around it - so you can see how it could cause vibration.

 

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27 minutes ago, 12 metre said:

The rudder will be shedding vortices especially upwind or reaching - kind of like the video below: which would tend to excite any weed wrapped around it - so you can see how it could cause vibration.

 

With a proper rudder profile it should definitely not shed carman vortices - it can be a lot of drag.  The vid you posted is of carman vortices around a rod - not a rudder

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When you set the prop, with most gearboxes you can rotate it by hand when in gear, but only one way. 

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34 minutes ago, Christian said:

With a proper rudder profile it should definitely not shed carman vortices - it can be a lot of drag.  The vid you posted is of carman vortices around a rod - not a rudder

Yeah,  my bad...but I thought it made for an interesting video nonetheless...;)

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Is it a 'pulse'? What time period? or is it a 'hum'?

Latter can be solved easily. Grind a chamfer on one side of the trailing edge of the rudder.

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1 hour ago, SteveC said:

Is it a 'pulse'? What time period? or is it a 'hum'?

Latter can be solved easily. Grind a chamfer on one side of the trailing edge of the rudder.

Not class legal.

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I didn't even think plastic bag. that's probably the culprit.

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19 hours ago, fucket said:

Which 10 did you buy?

Hull 334.  Was called "Woody" before I got her.  She needed the usual T Ten stuff...recore here and there, new cabin sole, etc.  But now she's sailing.  And I am learning how tough the Ten is to sail really fast.  I haven't had my butt kicked as badly around a race course as I did this season since I was 13.  But its a fun ride and a great step up from a J24.

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19 hours ago, SteveC said:

Is it a 'pulse'? What time period? or is it a 'hum'?

Latter can be solved easily. Grind a chamfer on one side of the trailing edge of the rudder.

It was definitely a pulse.  I didn't time it, but around 2-4 cycles/second is a ballpark estimate.

I did not have time to check the keel and rudder profiles before the boat was splashed in the spring.  I am going to make a set of templates this winter and see if the boat could benefit from a keel/rudder job.  I am assuming these things are faster when both are faired to minimum thickness.  Previous owner noted that the bottom was barrier coated, but did not mention anything about work being done to the foils.  

If anyone out there knows the history of 334, or knows a guy who knows a guy, or whatever, that would be great.  Feel free to PM me.

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That's a Lake Erie boat, right? From Mentor, I think. I'd call Heidi Backus, probably.

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2 hours ago, fucket said:

That's a Lake Erie boat, right? From Mentor, I think. I'd call Heidi Backus, probably.

Correct.

As for rudder bearings, there is a small amount of play between the rudder shaft and tube, but its been there since before I bought the boat, and did not oscillate before.  I am thinking it was a foreign body on of the foils.  There has been all sorts of weeds growing in the basin and floating around in the lake as of late, so that is the most likely culprit.

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On 9/17/2018 at 12:12 PM, sail611 said:

Okay, I knew weeds would slow the boat down, but wasn't aware of the extent to which they could vibrate a hull.  So Occam would tell me that I most likely had a weed on one of the foils, and it came off somewhere between the race course and the dock.  

I will pay close attention to the helm next time I sail the boat, hopefully in a couple of days, and if those symptoms are gone, I will assume weeds.  If not, I'll be back.

Yeah, weeds can be wicked.  On the tartan I used to race on we actually put a small piece of lexan looking down at the leading edge of the rudder.  We used to do a lot of distance races and seaweed is a killer.

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Woody was Dan Jackett's boat, out of Mentor.

  she was a good boat.

  Try to get any play out of the rudder using mylar tape at the top and bottom of the post.

    Probably was a growler on the rudder.  Blades open won't cause that vibration.  

  How fast were you going at the time?  Ten's tend to go the same speed when reaching, particularly if you're close to hull speed,  6.5 kts or so.

  if the other tens passed you that quickly, and you were in clear air, you were most likely dragging something...

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Yup, talked to Dan a lot during the purchase and restoration.  We are still learning the boat and tuning.  Its a touch different than tuning a J24.  Will look into the mylar on the rudder post when the boat is on the hard.

Sailed last night in similar enough conditions to Sunday, and there was no pulsing whatsoever in the rudder/tiller.  So that tells me we picked something up on Sunday, slowed us down, and cost us that race (went from 2nd to last over the race course....the weed or whatever slowed us down like crazy)...but at least it was just a weed or similar, and nothing super serious.

Raked, I see a 10 in your avatar.  You still sailing on one?  

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On 9/18/2018 at 11:25 AM, sail611 said:

It was definitely a pulse.  I didn't time it, but around 2-4 cycles/second is a ballpark estimate.

I did not have time to check the keel and rudder profiles before the boat was splashed in the spring.  I am going to make a set of templates this winter and see if the boat could benefit from a keel/rudder job.  I am assuming these things are faster when both are faired to minimum thickness.  Previous owner noted that the bottom was barrier coated, but did not mention anything about work being done to the foils.  

If anyone out there knows the history of 334, or knows a guy who knows a guy, or whatever, that would be great.  Feel free to PM me.

As you're a new owner, you need to get measured anyways and your local measurer should have templates. NAC is in Lake Erie this year, (probably Mentor) so more urgency than there would be otherwise.

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11 hours ago, sail611 said:

Yup, talked to Dan a lot during the purchase and restoration.  We are still learning the boat and tuning.  Its a touch different than tuning a J24.  Will look into the mylar on the rudder post when the boat is on the hard.

Sailed last night in similar enough conditions to Sunday, and there was no pulsing whatsoever in the rudder/tiller.  So that tells me we picked something up on Sunday, slowed us down, and cost us that race (went from 2nd to last over the race course....the weed or whatever slowed us down like crazy)...but at least it was just a weed or similar, and nothing super serious.

Raked, I see a 10 in your avatar.  You still sailing on one?  

told ya!

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21 hours ago, sail611 said:

Yup, talked to Dan a lot during the purchase and restoration.  We are still learning the boat and tuning.  Its a touch different than tuning a J24.  Will look into the mylar on the rudder post when the boat is on the hard.

Sailed last night in similar enough conditions to Sunday, and there was no pulsing whatsoever in the rudder/tiller.  So that tells me we picked something up on Sunday, slowed us down, and cost us that race (went from 2nd to last over the race course....the weed or whatever slowed us down like crazy)...but at least it was just a weed or similar, and nothing super serious.

Raked, I see a 10 in your avatar.  You still sailing on one?  

Yep, she's still kicking...

  this season was slow, sailed a 70 mostly.

  Next yrs T10 NA's are at my home club MHYC,  

  You should come !  always a good regatta & Party !

 

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We are definitely sailing Nats next year.  Considering its a (reasonably) quick sail from Cleveland, no excuse not to.  Looking forward to it.  

 

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8 hours ago, Raked Aft\\ said:

Yep, she's still kicking...

  this season was slow, sailed a 70 mostly.

  Next yrs T10 NA's are at my home club MHYC,  

  You should come !  always a good regatta & Party !

 

Lame that NAC is a conflict with the Verve.

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