DIY Diving fins

[Lovre]

I'm interested if anyone has tried to make his own diving fins ? It should not be much of a problem to make them, and it seems to me that comercial fins are too expensive for what they offer ... So if anyone tried this I would be gratefull is he would share some of his experiance ... Sory for offtopic but this is only site that i know of that discuss composite materials ...

Thank you

[sigurd]

how you going to strap them to your foot?

[Poida]

Diving fins expensive?

Is this for scuba or free diving?

If they are for scuba diving the cost is minimal compared to the overall cost of equipment.

Fins are designed to propel you through the water with the smallest amount of effort. This is where the design comes in to it. The cost of the material that goes into it is only a fraction of what you pay.

This is true in most cases. If you looked at a car engine, and calculated its material worth, it would probably only be worth a few dollars.

I also doubt that you could in fact make them cheaper, my guess is you haven't sourced materials and costs yet, and you deffinately would not without a few hundred test pieces get the correct flexibility, weight distribution and shape to be as efficient as a bought pair.

Poida

[Trevlyns]

Quote sigurd - how you going to strap them to your foot?

I have this vision of carefully shaped 2mm composite ply and duct tape

[Lovre]

Straping it to foot is not so much problem, cause I thougt of using foot pocket from some of known manucacturer, cause this is really cheap. What costs a lot are blades, carbon 250-400 Euros, or fiberglass 150-... Euros. Footpocket is about 25 Euro, so it is not mouch of a problem.

I talking about freediving fins all the time, cause for them you have to use composite materials and to get as much thrust as you can, because efficiency is of most importance. You dont want to waste any air from your lung.

I understand that you would have to experiment a lot till you would get perfect result, but I honestly think that for less then 100 Euro one could make very good blade, and that is why I find this interesting.

I think that with vaccum bagging and 50-100 Euros of material, and 2 hours of my time I could make very good fins. I'm very interested in what all of you think about this cause you have much more experience in working with composites than I do.

[marshmat]

The cost of those high-end commercial fins isn't in the materials. The fibre and resin are worth only a few tens of dollars. The cost is in the design process, getting the exact hydrodynamic shape and flexibility that you need. A top-grade fin at the dive shop is probably the 50th or 60th variation of the design that was tried before the performance was exactly what the designer wanted. That's a lot of building moulds, building fins, testing them out, analyzing the flow over the blade, redesigning, etc.
You can of course make much cheaper ones. But they won't perform as well as the ones that have thousands of hours of testing and design work in them.

[Pericles]

Why are you trying you re-invent the wheel?

http://en.wikipedia.org/wiki/Lo%C3%AFc_Leferme

Pericles

[Lovre]

Actually its not so hard I think, blades have only one shape. Its rectangle wide 20-30 cm, and long 70-100 cm. Its very easy to design them, only thing you have to design is hardness or better to say flexibility. Holy grail is to get enoguh flexible and in the same time hard enough to push you and not to get broken ...

[Lovre]

Originally Posted by Pericles

Why are you trying you re-invent the wheel?

http://en.wikipedia.org/wiki/Lo%C3%AFc_Leferme

Pericles

I did not understand this ?? It was tragic death. He tried to even his best dive ... 171 m . I dont think that somebody would try do make his own fins and try to break WR ?!

Rest in Peace Loic

[eyes]

Fins are not only a plate, the most efficient ones a re H shaped sometimes with a cut straight in the middle to help with propulsion. The H shape adds stiffness and moves the water straight to the back not sideways.
Take a look at:
http://www.simplyscuba.com/ProductDe...x?StockID=2588

[Lovre]

Originally Posted by eyes

Fins are not only a plate, the most efficient ones a re H shaped sometimes with a cut straight in the middle to help with propulsion. The H shape adds stiffness and moves the water straight to the back not sideways.
Take a look at:
http://www.simplyscuba.com/ProductDe...x?StockID=2588

These all are scuba fins, its much more different from freediving fins. Some thing like this ...
http://www.c4carbon.com/eng/sub/superfalcon/art.htm

And this is maybe the best freediving/spearfishing fins ...

[eyes]

I know, but they still have some H shape, take a look at the pics of your link.

[Lovre]

ok ... now try to see all types of fins that c4 makes ...

http://www.c4carbon.com/eng/sub/fins/fins.htm

[sigurd]

Lovre, don't listen to the people who believe everything they don't know anything about is magic.

I think too it should be easy to make good fins. especially since you can make lots of fins, and learn stuff. when you have some sort of mold for the sock attachment part, it should be really quick. If the socks can be screwed right on, then you just need a bent plank as the mold.

Do you have a link to some good socks? Since I hate my toes being squeezed together, I have difficulty finding proper shoes. I think you can see the effect on the feet of nearly everybody who uses shoes regularly, the big toe points inward and the little toe is creeping under the next toe. Then the big toe attachment knuckle grows.
So for me I think it might make sense to use a sandal principle, by just screwing bands to the fin. that way it is easier to put pressure in the places that creates a solid connection without being uncomfortable. Even it should be possible to mold a rubber heel cup.

I imagine there should be some taper in the stiffness.
For instance the outer layers could be full length, then shorter and shorter layers towards the center. And if you put wrong flex somewhere, you just add a layer or sand away. Or you could use a tapered core and save weight (is that desirable?) and money.
I suppose you should have most fibers longitudal.

The c4 text about the "channels" on the flap I can almost not understand one sentence of.

I'd like to make a monofin soon. but when i swim like that, i feel there is too little opposing force, so I'd like to try some hand-fins or some fins on the hip.

[sigurd]

I think splitted blades are only good for low power fins.

But about the material, I thought fiberglass springs were almost 100% efficient in returning the input energy, so how come carbon is better?

What is a good angle between the blade and the foot sole?