Epic rudders

There is available different rudders for Epic, standard, surf and flat water. Does it make any difference to change surf rudder to flat water when racing flat water? Anybody practical experience ?

The epic guys I paddle with say.. Yes. But I can't keep up with them either way

It's interesting - there's been quite a lot of debate about the issue on the forum. Some people swear that the smaller rudders make a difference in terms of drag.

Here in SA I don't know of anyone who changes rudders for that reason; we seem only to change to low drag rudders to reduce the chances of catching weed.

If the rudder is made with a proper airfoil shape, I can't see that a cm or two of decreased rudder length would make a discernable difference...

But don't discount the mental effects! It's astounding how much faster guys will go just because they feel that they're on a faster/lighter/less drag boat!

There is a more than doubling of surface area to go from a small rudder to a larger one.

I can certainly see the difference on the GPS and on the stopwatch.

Can you tell about difference in your case, 1min/10K, or something like that?

There are a couple of aspects to this discussion of course:

- We can see quite easily (through mathematics and modelling) what the difference in drag is and what proportion of the overall drag comes from the rudder. With that you should be able to estimate what difference in speed/time would result. I still don't think it's significant, but am willing to be shown up!

- But a key aspect of racing on flat water is the ability to draft alongside or behind the diamond. Unless you can learn to draft you're toast on flat water. But a smaller rudder, rendering the ski less manoeuvrable could impact on the ease with which you control the ski on those small diagonal waves. Whether it's my own lack of ability or not I don't know, but I find it easier for example to draft on my Swordfish with its surf rudder than with the standard rudder. The boat felt to me as though it gripped the water better and I could steer positively in the messy side-wash. With the standard rudder it was more difficult and I had to provide more input (and in turn perhaps more induced drag) to get the ski back on course.

And that's my 2c...

In flat water the smaller rudder feels and turns with no perceptible difference, apart from the lack of tipping of the boat when the rudder is turned and a freer hull, in that it rolls a bit easier, having much less fin in the water to stabilise it side to side.

I have posted my times and or speed differences previously here and having not used the rudder for a long time now, I would truly be guessing.

I would have to dig back through files to give you a precise answer.

But what matters is that I made up my mind that if I ever entered a flat race it was well worth changing the surf rudder out and fitting the weedless.
So now that's all I keep in my head, testing done conclusion reached, forgot the details.

Here's an article comparing the drag and relative speed of the different Epic rudders.

www.epickayaks.com/news/news/which-rudde...i-use-on-my-surf-ski

I recently snapped the rudder on my V12 (hit a reef) and I was amazed how well the ski still tracked without the rudder all the way back. I have a 4cm tall weedguard which no doubt contributed to the tracking ability.

I might actually try a much smaller rudder after that unplanned experiment.

Here's some hard data from Mr. Epic, Greg Barton himself:

The Epic Surf rudder adds a little over 2% to the drag of a surf ski. Our Weedless rudder is 40% smaller and adds less than 1.5% additional drag to the boat. When paddling in flat water a large rudder is not needed and speed can be gained by changing to our smaller Weedless rudder.

How much will your speed increase by moving from the Surf to Weedless rudder on flat water? The speed/drag relationship is not linear, and our calculations show the Weedless rudder to be about 0.4% faster on flat water. Over a 1 minute sprint, that's only 1/4 second and nearly impossible to notice. However, on a one hour race the difference adds up to 15 seconds.

Of course if you encounter surf conditions, even a single broach or missing a couple runs will easily cost more than 15 seconds in an hour. So it doesn't pay to undersize your rudder when you need control. Size your rudder accordingly.

Here's the rest of the post:

Which rudder should I use on my surfski?

Ah - I see Greg beat me to it! Guess I should read through the thread before I post!

Thank you for the comments, I have clear picture now.
Maybe I buy weedless one or I will make very small one. In my case balance, when paddling V12 is not an issue, I can paddle K1 very well too, in principle for flat water racing the smaller the rudder is the better.

I fitted race K1 rudder to Epic. I did some simple calculation too, noticed, the hole for rudder when paddling after rudder change is three times smaller. The boat slides nicely and it feels a bit faster, but very unstable also .

I'm curious, why does the small Epic weedless rudder have that triangular shap towards the end? Has anyone chopped-off that triangle to make it a trapezoid or oval shape? Any ideas where does the shaft end inside the rudder?

As you can tell from the above, I'm very tempted to chop off an inch or two of the sharp end, which I think does nothing useful in particular as it is so thin - probably only creates drag and turbulence at turns...