rudder size

Has anyone had any success using a smaller rudder to get more speed from their boat. In a sea kayak I have there is a 1kph difference between rudder up and rudder down. I had an xt with 5cm foiled off the length and I felt it was faster. Unfortunately it was my only rudder so I couldn't swap to make a comparison (or if the chop was bigger). I was curious if anyone has done a comparison.

I use a Select marathon rudder on my V10 when the waves are smaller than 1 meter :
select-kayaks.com/en/news/rudder-line/
I have size L and it works very well on flat water and small waves.
My average speed on 4 minutes intervals changed from 12.8-12.9km/h to 13.1-13.2km/h.
Seaweed is no problem anymore.
The rudder is too small when the waves are big, but the XL size might work.
The rudder shaft length is long enough, but the shaft is only 6mm while the original shaft is 3/8 inch (9.5mm).
I use 3 metal tubes to make the shaft thicker, but tape is also OK.
The metal tubes have dimensions:
6.1mm inside, 7mm outside
7.1mm inside, 8mm outside
8.1mm inside, 9mm oustide

Regards,
J?rgen

Hi,
I do agree that the Select rudders are great. I have fitted them to my ocean racing kayak and there is a definite gain in terms of speed and control. If seaweed is not a problem I do prefer the racing type rudder over the marathon version. It is much more effective in turning and tracking. The medium racing rudder gives me more control than the large marathon model. This is especially true in small chop where the wavelength is shorter than boat length.
Carbon tubes can be used as adapters to make larger diameter shafts. They come in a variaty of diameters, thicknesses and are manufactured with very tight tolerances or can be sanded to a precise fit. No issues with corrosion either. I use them to fit standard racing rudders with 6mm shafts to marathon boats which commenly use 8mm shafts. Works great!

cheers, rojo

I stumbled upon your article and put some thought into it. I've recently been transplanted from South Africa to Bermuda. An amazing variance in conditions - from flatter than a bath tub - to huge wind swell (extremely short and steep). It would be an interesting experiment to play around with different rudders. I had a look at the select-kayak site. What is the general rule of thumb when looking at different rudders. I understand a longer rudder can lead to greater instability. Will these new rudders further obviate the need for a weed deflector?

Cheers