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 Post subject: Rudders
PostPosted: Fri May 22, 2009 4:21 am 
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Joined: Mon Jun 23, 2008 7:37 am
Posts: 12
Location: Western Australia
Hey people
Hows the sailing.
My tiger is giving me the (censored).
As soon as I get 2 on the wire I loose the rudders. They cavitate and put the brakes on and it is a dog to sail.
I have faired the rudders and mucked around with the alignment with no sucess. I have kicked them under and layed the back which only succeeds to make the helm lighter or heavier and hasnt altered the cavitation. I have faired and polished the blades. Nothing.
When the Kite is up is steers like a dream.
When 1 or none on the wire it is also good.
It is also ok when in excess of 25kts.
I think it is the Mast rake. I cant see it could be anything else.
Any sugestions
Cheers and thanks in advance
Bevo
Perth Western Australia


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 Post subject: Re: Rudders
PostPosted: Fri May 22, 2009 11:11 am 
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Joined: Tue Apr 05, 2005 12:44 am
Posts: 85
Also check your daggerboards. Turbulence may develop there and continue to the rudderblades. If everything is fine with the kite up however, I dont think this is the problem. Maybe its related to the way you are stearing. If you drop the tiller, what does the boat want to do? (it should have a slight tendency to go upwind, on both tacks). You have to counterrest this tendency with the tiller, but with VERY smooth movements. One fast move and you get what you describe. If the tendency towards upwind is very exaggerated, try to open up the main a little and see if it gets better. If so, mast rake more forward might help. The boat however goes faster with more rake, so you'll have to find the sweet spot. Also try to move around crew weight (backwards).


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 Post subject: Re: Rudders
PostPosted: Fri May 22, 2009 12:01 pm 
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Joined: Mon May 09, 2005 10:25 am
Posts: 2518
Location: Jersey Shore
Any weeds or seagrass where you're sailing? Having that stuff on your rudders will cause you to stall and totally mess up your steering.

Also make sure you've got enough downhaul pulled on when you're powered up. Too little downhaul will allow the draft to move back in the mainsail causing the rudders to overload and the boat will want to fly a hull too much. Pull the downhaul hard to keep the sail's center of effort forward and low. This keeps the boat balanced and going fast.

Otherwise, make sure your rudders totally faired and the shape looks good and consistent (no hollow spots).

sm


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 Post subject: Re: Rudders
PostPosted: Sat May 23, 2009 8:52 am 
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Joined: Mon Nov 22, 2004 7:18 pm
Posts: 73
Location: League City, Texas, USA
What is your total weight and were are you placed when it is cavitating? I sail about 340 lb (154 kg) and if we have our weight too far forward with the main sheet full on then the rudders will sometimes cavitate. Moving a few inches back helps. We sail with the rake about by the top of the transom in most conditions - dropping as far back as the top of the lower gudgeon in a big blow.

I found the latest generation Tiger rudders seem more prone to cavitate then the old ones - but have a lighter feel on the helm. Overall I like them though.

Chris.

_________________
2008 Hobie Tiger


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 Post subject: Re: Rudders
PostPosted: Mon May 25, 2009 9:10 pm 
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Joined: Sat Sep 13, 2008 10:03 am
Posts: 14
We had a similar issue and were chasing a few different issues. After discussion with several sailors in other high performance boats we removed all teflon/low friction polish and wax which we now believe was causing the flow to become unattached - this has seemed to fix much of the cavitation for us.

We went as far as lightly sanding with 400 and then leaving it....


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 Post subject: Re: Rudders
PostPosted: Mon Jun 15, 2009 9:38 pm 
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Joined: Mon Aug 04, 2008 8:23 pm
Posts: 13
Location: Perth, Australia
You trying to get some tips before the nationals Bevan???

Maybe you should try sailing the boat backwards. I try the upside method all the time so we can compare notes.

I'm going to be training at NYC with Mark shortly - once July starts hopefully every 2nd weekend. Let's get together and do some work. Looks like a good fleet with QLD and VIC both sending a number of boats. NSW may have some also, I'm waiting to hear.

_________________
"This should be interesting..."


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 Post subject: Re: Rudders
PostPosted: Tue Jan 19, 2010 4:05 am 
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Joined: Mon Jun 23, 2008 7:37 am
Posts: 12
Location: Western Australia
Ha ha Gav I have just as much trouble keeping the rudders from pointing skyward as you.
Here is an update. I stood the mast up about a whole chain plate length which give me a mast rake at the back of the hatch cover. This appeared to help significantly I dont seem to stall the rudders anymore. BUT now I have severe weather helm uphill and lee helm downhill with the kite up. Also the rudders are stalling out when they re-enter the water with the kite up. This can be quite unsettling as I loose the ability to steer for a brief moment which induces severe panik.
Also it appears to be different with different crews. My sister who I sail with when I want to win (want to as opposed to getting to) the boat seems to settle but when I sail with the co-owner of the boat (40kg heavier) the boat sails like a dog.
I leant my boat to someone else for a bit and told them about the rudders and they come back saying I was Dillusional as they thought it steered perfectly. The boards and blades have been faired and I have a set of old style blades which I am yet to try.
This is not making my tiger experience very happy.
Can anyone help me
Cheers
Bevo
AUS 1887


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 Post subject: Re: Rudders
PostPosted: Tue Jan 19, 2010 9:47 pm 
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Joined: Sat May 23, 2009 4:13 am
Posts: 6
Location: Victoria, Australia
G'day Bevo

You need to rake the mast back so as you have control downwind, this is a must. Rake back to at least the back corner, most of us are at least a couple of inches down the transom.
The weather helm you have going to windward is only where you are trapping from, you need to move your combined weight back until steers in the sweet spot. This seems aparent from when you say your other crew is 40kg heavier and this is when you notice it most, when your lighter crew is on the front it steers better.

Hope this helps

Mark
Tiger AUS1856


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 Post subject: Re: Rudders
PostPosted: Wed Jan 20, 2010 3:24 pm 
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Joined: Thu Nov 13, 2003 10:00 am
Posts: 383
Location: Long Beach, CA
I think WickedF18 is exactly right.

If you are not balanced upwind to downwind it can be the mast rake (for weight of 330 I like it at the second rudder gudgeon screw from the top). Once you get that fairly balanced you can adjust the rudders to allow for more or less helm (I think I remember it was 1 1/8 inches of rudder in front of a straight line down from the transom). Try making these your base and work it from there.

The main will make your bows go to weather and the spinnaker will make your bows push downwind. You are trying to balance the rake of the mast upwind with the pressure on the spinnaker downwind. The further forward your mast is the greater difference in helm you will have upwind to downwind.

You cannot let the crew stand forward if you are double trapped. Their position should be straddling the shroud, as the most forward they can go, or back from that. Also keep your weight right next to them. That will act as a smaller fulcrum for you to steer around letting the rudders do their thing and not cavitate.

If you keep changing the weigh of your crew (different people) the boat will not be tuned for each sailing session. Find a crew you will race with and keep that setting all the time. When sailing with friends who are heavier just accept that the boat will not sail exactly the same.

Also if you sail a little lower (footing) you will not be on the edge of stalling the boat all the time. When the boat stalls you have to pull the tiller pretty hard to get it going again and this will stall the rudders. Try just about 1 to 1 1/2 degrees of foot.

Later,
Dan


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 Post subject: Re: Rudders
PostPosted: Wed Jan 20, 2010 3:52 pm 
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Joined: Mon Jun 23, 2008 7:37 am
Posts: 12
Location: Western Australia
Cheers guys I will run with that for the weekend as I have a 3 day regatta so that should let me test and adjust. I moved the mast rake forward during the winter series and I thought it helped but we didnt have enough wind to double trap for the whole series so i didn t really get to check it out and havent sailed the boat since.
So From what I get from you guys is rake the mast back a little to get the downhill steering right and trap furthur back and tune the rudders to minimize the upwind weather helm.
Thats great advice Ill let you know wednesday how it went


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 Post subject: Re: Rudders
PostPosted: Thu Jan 21, 2010 9:57 am 
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Joined: Thu Nov 13, 2003 10:00 am
Posts: 383
Location: Long Beach, CA
Best of luck to you this weekend. Hope to hear the report later.


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 Post subject: Re: Rudders
PostPosted: Tue Jan 26, 2010 4:17 am 
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Joined: Mon Jun 23, 2008 7:37 am
Posts: 12
Location: Western Australia
Hey Guys
Well.
I have sailed for a weekend (4 races) in varing breezes from 10-25 knots
I raked the mast back a bit and lost the lee helm with the Kite. Thanks for that tip. But I re checked the rudder alignment and it was a little out so I adjusted that and had a little success. I now have a fairly neutral helm upwind but once double trapped the windward rudder stalls on re-entry after flying a hull. Once it stalls the helm goes very light and unresponsive and the leeward rudder stalls and I can see a vortex coming off the tip of the leeward rudder and a rooster tail that is impressive. I sailed with 2 crews on the weekend one combined weight of 200kg (I know its a little heavy) and the other a combined weight of 170kgs (A little more reasonable) It made no difference with either crews. The boards are straight and not twisted as with the rudders. I am now getting the (censored) and a new Windrush Edge or Nacra Infusion is looking pretty attractive right now. The rudder issues make it hard to change gears and I am getting whooped by a F16 because I cant maintain my speed upwind.
I also have the newest style rudder blades and I also have the older ones aswell.
Any suggestions??


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 Post subject: Re: Rudders
PostPosted: Tue Jan 26, 2010 9:27 pm 
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Joined: Sat May 23, 2009 4:13 am
Posts: 6
Location: Victoria, Australia
G'day Bevo

I'm glad it was better for you down wind, thats a start.
The cavitation is now to do with where you are trapping from. You need to move your weight further back. 200kg is heavy but so what I sail heavier than that every weekend. As soon as you notice any cavitation get your crew to move further back with you.
You said in your prevoius posts that when other people sail your boat they don't notice any problem. This make me think it is something that you are doing differently, the most obvious it where you are trapping from.
Can you answer some questions with as much detail as possible.
Where are you trapping from?
How much tuck is on your rudders? Run a straight edge doen the back of the hull and tell us how much rudder is forward of the straight edge.
Do you have the early style or newer rudders?
Where is your jib car positioned? How far from the end?
Does your boat point well with regard to others?

Hopefully we will get to the bottom of the problem

Regards


Mark


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 Post subject: Re: Rudders
PostPosted: Wed Jan 27, 2010 12:42 am 
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Joined: Mon Jun 23, 2008 7:37 am
Posts: 12
Location: Western Australia
Thanks Mark for helping.
Rudders leading edge is parallel with the straight edge for most of the way untill the rudder curves obviously.
I have the latest style blades.
Jib car is half way between the last 2 posts on the jib track and I point excetionally well. Out point Tornado's with ease but not quite as high as a Nacra 16 square. I run a sailtech Jib not a hobie.
And I (skipper) trap with my back foot at the back beam and my crew rubs shoulders with me. The bottom of the nose of the boat skims the top of the water. I personally would like to see the nose a little furthur under but that is how it has to be.
It is dog slow and very hard to (change gears) as it feels like I am dragging an anchor or forgotten to take the trailor off. Quick downhill and I usually have to make up a bit of ground anyway but I dont seem to have too many hassles down wind. But sometimes if the nose goes under with the kite up the rudders will grab a gut full of air but it clears quickly and doesnt bother me too much. I have tried footing a little which seems to help

I am getting desperate here and I am also going to try to get some dealer help When I see them otherwise I will just go out and buy an infusion or windrush.
Cheers
Bevo


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 Post subject: Re: Rudders
PostPosted: Wed Jan 27, 2010 3:41 am 
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Joined: Sat May 23, 2009 4:13 am
Posts: 6
Location: Victoria, Australia
OK now we're getting somewhere.
You are definately trapping far enough back (probably to far but we will get to that later) so my original thoughts on you not being back far enough were wrong.
Rudders need to be tucked under more. Thats why they changed to the latter version so that they could get more tuck under the boat. They should be about 15-20mm forward of the transom straight edge, basically as far forward as you can get them.
Next steering balance is effected by weight position or sail effort, so if we have established that it is not were you are putting your weight it has to be rig related.
Do you use a loos gauge, if so what is your rig set at in 20 knots? If you don't how much prebend is in your mast. I am starting to think it may be sail/rig related e.g. diamond to loose etc. But I'm confused when you say other people don't notice any problem.

Keep trying it can be fixed.

Mark


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