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Customizing Your UDTs: Increase Flex & Reduce Weight

Two inches removed from blade and center ribs removed.

Side view showing a thinner blade.

Side ribs after being ground flat on the top
of fins, 3 inches back from the tip.

After a couple of years of intermittently grinding away on my UDTs, I think I finally have them tuned-in.

Modifications. A lot of stock were removed from the fins, including all of the center ribs, top and bottom. Initially,
2 inches of the original blade were cut off. Then a 1/4 to 1/2 inch were removed from the side ribs. Lastly, the side ribs on the top of fins were ground flat, 3 inches back from the tip. This final modification gave the fins the extra snap and quicker return on the upstroke that really dialed it in. (Click on images for a larger views of the fins.)

Test & Evaluation. Yesterday's test session in some waist-to-chest high wind swell confirmed that these modifications delivered the thrust I had been looking for without punishing my feet like the unmodified UDTs.

Change in Technique. I had to change to a slower kick to take advantage of the slower oscillation, but I paddled outside more quickly than with my other fins and generated plenty of power to get me into the wave earlier. The natural rubber really felt like it was doing it's thing. With a 3mm bootie they are actually reasonably comfortable. I need to get them out in some bigger conditions to confirm my impressions, but these modified fins feel like a winner.

Additional Benefit. The modified UDTs are considerably lighter than the originals. They weigh in at 4.5 lbs for the pair, good enough to make them manageable travel fins.

Tools Used. I found the ultimate fin grinding tool: a 4-1/2 inch Norton Rapid Strip wheel for my Dewalt metal grinder. The wheel I used was the non-woven fiber wheel -- they are blue in color. This set-up zips right through the rubber without clogging. The same wheel was used to do the final shaping as well. Here is a link -- they cost about $10 bucks. Most hardware stores have them.

John Hughes
e-mail of November 30, 2011

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Last updated on: 11/30/11