Just returned from a 10 day trip to the Bahamas. These are my impressions of the Dolfin x18, the prototype for the production model, x20. I used it 5 days straight and got a pretty good feel for the fin.
Impressions:
It feels like a continuation of how it felt in the pool(described farther back in this thread), but a little hard to explain The fin is highly adaptable. I had the feeling that it would do just about anything I asked it to. Very different from the feeling I get with other monos and much more like bifins. Very very comfortable, partly because of the bike shoes but something else too. I'm not too sure what it was.
Might just be me, but Eric F's comment about taking 1000 dives to get comfortable with his orca is looking more and more accurate. The fin is instantly usable, but very subtle. Its taking me a while to really mesh with it. Still, others have different experience. Azapa had previously worn a mono all of 5 minutes total, ever. He took to the x18 instantly, like he was born with one, and was diving deep before we turned around good. He will chime in directly.
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I can spearfish with it. This was the key unknown issue for me and it works fine. Still a little difficulty in turning sometimes, but that is just a technique issue. For Bahamian conditions, I think the fin will end up maneuvering for spearing as well as bifins.
The fin is relatively negative compared to bifins, has a much smaller surface area and far less drag than other fins or the body, which makes it try to fall faster than me. Temporarily solved by continuing to stroke it just a little while falling, but my trim needs adjustment.
Vertical movement is entirely different from horizontal. I had only used the fin in a pool and the surf and was caught by surprise by the difference. Weighting trim is absolutely critical. A neck weight is required, something I'd never used. I borrowed one from Azapa and the action of the fin changed dramatically. The neck weight was a little too light and I still had some weight on my belt, would have been much better on the neck. With the weighting I had, I was still tail heavy, and could not get the negative flying thing to work.
The fin is a joy to surface dive with, far far better than bifins or the monos I've tried.
Spotted dolphins go ape for the fin. They come from all around to get a close (very close) look at it. There will be videos of this action in Freediving Stories when we get the thread up. Pretty amazing.
The acceleration the fin is capable of is great. In the past,when playing with dolphins, there was no chance of catching up to them, even when they were going slow. With the x18, I could sometimes catch them from behind. Real fun and they acted surprised. I haven't needed it yet for spearing, but know it will come in very handy.
Stroking the fin uses a much wider array of muscles than bifins, which rely on relatively few, large muscle groups. Because of this, and maybe because it is more efficient, my legs did not get near as tired as with bifins. Thats good. The flip (bad) side is that relaxation is relatively hard for me. With bifins, I've gotten fairly good as using only what is needed and relaxing the rest . Can't do it yet with the x18, which makes for a much less relaxed dive. I think this is just a technique issue, but would like to know others experience.
-After 5 days, I knew what I needed to do to beat the trim issue but could not do it on the boat, so I switched back to bifins for everything but dolphins. Next time out I should have the trim issue solved.
Overall, I liked it very much. In lots of ways it is far superior to bifins or any other mono I've tried and where it is not (yet), mostly that is fixable. I'm pretty sure I'll be hanging up my bifins.
Two things to fix the trim issue. First a series of neck weights of different sizes. Second, I'm going to play with adding some incompressible flotation under the shoes where drag won't be an issue. I can make blocks of 4 lb density foam and shape them as needed, or maybe find out where Eric got his micro-balloons. Don't think it will take much flotation and too much might interfere with the fins action on the surface. Time to tinker.
Ron, we got some killer video and stills of the fin, spearfishing and dolphins. Check out the links when we get them up. Might be some useful marketing stuff there.