Does rudder size affect stability?

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8 years 8 months ago #19097 by arminius
Wow, your description of winter makes me appreciate Auckland even more.

Another perfect day in paradise. A bit of sun, a bit of rain and it's not even lunch time.

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8 years 8 months ago #19100 by Newbflat
It's even harder to dress for immersion during the summer as the water only warms up a couple of degrees but the weather can be hot-ish.

Bill

FENN Bluefin S
FENN Swordfish S carbon hybrid
Epic V8 double gen 2
Lot and lots of DK rudders.


Had:
Stellar SEL excel (gen 2)
Stellar SR excel (gen2)
Stellar S18s g1 (excel)
Epic V10 Double (performance)
Stellar SR (gen 1)
V10 sport (gen 2)
V10 (Gen 2)
Beater SEL (gen 1)

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8 years 8 months ago #19101 by robin.mousley

Jmuzz wrote: The difference between a large and small rudder is fairly easy to feel.
The big rudder has less twitch since the boat is slower to wobble from side to side, the rudder is locked in place by more water.

But the big rudder will also make the boat tilt more violently when turning quickly. So in that way it is less stable.


Just my 2c - I agree completely. My Think Evo II's handling in rough water was improved significantly by moving to a big elliptical rudder, both in lateral stability (ie from side to side) and longitudinal stability (ie keeping to straight line).

Rob

Currently Fenn Swordfish S, Epic V10 Double.
Previously: Think Evo II, Carbonology Zest, Fenn Swordfish, Epic V10, Fenn Elite, Red7 Surf70 Pro, Epic V10 Sport, Genius Blu, Kayak Centre Zeplin, Fenn Mako6, Custom Kayaks ICON, Brian's Kayaks Molokai, Brian's Kayaks Wedge and several others...

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8 years 8 months ago #19102 by Newbflat
On a whim today i unhooked my bungees that i rigged to the peddles of my V10 to help keep the rudder centered. There was a very noticeable increase in twitchiness as the long weedless rudder started to flap around some. Directional stability suffered some as well. I tilt my peddles forward to keep me from moving them when driving my legs. If your feet are firmly planted on the peddles it might not make much a deference. But If you feel any extra movement in the rudder, try some bungees.

Bill

FENN Bluefin S
FENN Swordfish S carbon hybrid
Epic V8 double gen 2
Lot and lots of DK rudders.


Had:
Stellar SEL excel (gen 2)
Stellar SR excel (gen2)
Stellar S18s g1 (excel)
Epic V10 Double (performance)
Stellar SR (gen 1)
V10 sport (gen 2)
V10 (Gen 2)
Beater SEL (gen 1)
The following user(s) said Thank You: Kocho

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8 years 8 months ago - 8 years 8 months ago #19107 by Watto
To Newbflat et al off-topic and re cold weather gear - see www.chillcheater.com

On their own probably not enough for your conditions, however may work under a drysuit.

I have the aquatherm fleece trousers and aquatherm long sleeve top for chilly, rainy days or white water long day. Well made, reasonably priced gear that works brilliantly without overheating - an issue with some cold weather gear such as neoprene which can be unforgiving.
Last edit: 8 years 8 months ago by Watto. Reason: Added a bit.

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8 years 8 months ago - 8 years 8 months ago #19108 by Shackleton
I don't know if anyone would find it interesting but, here in Kansas, in summer, when temps reach 100 degrees the water temp gets into the 90's. It feels like bath water. That's when a surf ski is really nice because you are always wet.
Last edit: 8 years 8 months ago by Shackleton.

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8 years 8 months ago #19113 by Ric
If this thread is still about rudders...

I fitted an elliptical to my new Focus, and last night was my first time out with it.

First impression - the moment I touched the pedals, the boat leaned over. It was quite amazing.

So initially I'd say the bigger rudder made it harder to balance - I'm pretty sure once I get used to this effect, that I will find it is EASIER to balance with this rudder - I just need to find the correct control.

my 2c

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8 years 8 months ago #19114 by robin.mousley
"new Focus" hey Ric?! Look forward to seeing it tomorrow!

Every time I've fitted an elliptical rudder (Mako6, Fenn Elite, SF, Evo II, Genius Blu, Genius G40, to name a few) I've also experienced an initial period of "whoa!" until I've become used to it.

One thing you might want to try is adjusting your rudder pedals so that they're tilted slight forward - so that you don't push them as you take each stroke. That way the rudder doesn't move and acts as a keel, enhancing stability.

Rob

Currently Fenn Swordfish S, Epic V10 Double.
Previously: Think Evo II, Carbonology Zest, Fenn Swordfish, Epic V10, Fenn Elite, Red7 Surf70 Pro, Epic V10 Sport, Genius Blu, Kayak Centre Zeplin, Fenn Mako6, Custom Kayaks ICON, Brian's Kayaks Molokai, Brian's Kayaks Wedge and several others...

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8 years 8 months ago #19115 by Shackleton
I was thinking the larger rudder would make a tippy boat more stable in rough water. Maybe I will just get one of each and experiment.

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8 years 8 months ago #19116 by Kayaker Greg
After buying my Swordfish earlier this year and reading Robs comments on the Orka Elliptical rudder for the Swordfish I went onto Orka's site to buy one and saw they also did a surf rudder which is similar to the rudders on my Stellars. I bought a surf rudder and elliptical rudder, I fitted the surf rudder and this is my everyday rudder on the Swordfish and I much prefer it to the sharkfin rudder and do not experience this "whoa" moment when using. I thought I would try the elliptical rudder in bigger downwind conditions, to date I have not had the reason to put it on but perhaps the surf rudder would be the better option for most boats?

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8 years 8 months ago #19119 by MaxB
I went to buy an elliptical rudder on the strength of some of the comments here in a bid to increase the stability of my Swordfish. I was talked out of it by the guy in the shop, who said it would increase the responsiveness of the steering, but wouldn't make a perceptible difference to stability.

To Greg, Rob and anyone else who's experimented with different rudders on a Swordfish: what are your opinions on the practical differences that rudders you've tried have made?

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8 years 8 months ago #19121 by robin.mousley
In my experience different boats are affected differently.

For example the Mako6 was very difficult to control (for me) in our short, steep downwind conditions here in Cape Town until I installed a big elliptical rudder, which totally transformed the boat.

I found the Evo II was not only easier to paddle downwind; I also found that the tracking was improved and it felt more stable in choppy water, particularly diagonal chop where the tendency to be thrown off course was reduced.

In other boats, like the Mako Elite, I didn't find nearly such a difference; I found the Elite didn't have much tendency to broach even with the shark fin rudder.

However, the Fenn shark fin rudder does get much tighter, the higher your speed - because the meat of the rudder is behind the pin. The elliptical rudders tend to be much better balanced.

With the Swordfish I tried the original shark fin rudder; the new Fenn elliptical rudder and then the Orka elliptical. For me, as a mid-packer, but with lots of downwind experience, I found the SF quite prone to broach with the shark fin rudder (again, as I emphasise, in our short, steep, wind-generated waves in Cape Town). The Fenn elliptical rudder is too thin (in my opinion) and stalls easily. The fatter, larger Orka rudder is definitely the rudder of choice for me.

In terms of stability, the rudders didn't make much difference to me in the SF. The only reason to go for a bigger elliptical rudder is to get better handling in downwind conditions - in my opinion!

Rob

Currently Fenn Swordfish S, Epic V10 Double.
Previously: Think Evo II, Carbonology Zest, Fenn Swordfish, Epic V10, Fenn Elite, Red7 Surf70 Pro, Epic V10 Sport, Genius Blu, Kayak Centre Zeplin, Fenn Mako6, Custom Kayaks ICON, Brian's Kayaks Molokai, Brian's Kayaks Wedge and several others...
The following user(s) said Thank You: Newbflat, Shackleton

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8 years 8 months ago - 8 years 8 months ago #19123 by Kayaker Greg
Agree with Rob, the Swordfish is pretty stable anyway but the sharkfin rudder is not the best for boat handling in my opinion on waves at slow speeds, then when the speed increases it gets real heavy.

On less stable boats like my Stellar SES there is a noticeable difference between the smaller weedless rudder and the larger 9" surf rudder for stability.
Last edit: 8 years 8 months ago by Kayaker Greg.

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