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 :p

[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]

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/ProductDetails.aspx?StockID=2588

[Lovre]

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/ProductDetails.aspx?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?

[Poida]

Sigurd my friend, you are reading into people's posts, points that are just not there.

Myself and my I say Marshmat did not say that the project was not impossible.

If Lovre had said that he wanted to experiment with making fins that would be fine and I for one would not have responded because it would be quite an interesting project.

However what we have commented about, is that Lovre wanted to do it to save money. This is where he is drawing adverse comments. The fins on the market have been made from years of experimenting with material combinations, thicknesses, tapers and stiffness.

Of course his satisfaction with the result of his work depends on the seriousness with which he persues the sport.

Perhaps some enquiries on a diving forum would help.

Best regards
Poida

[eyes]

I was not saying that it can't be done, i was just telling him to haave a good look at the details. I admire people who doesn't get scare in any job.
"Those who say it can't be done, can't be interrupting those who are"

[John Olson]

Hello Lovre,

I hope you go for it and don't let your enthusiasm and ambition be dampened by anyone. I think you will be faced with challenges, but maybe you will come up with something better too. I have seen many products touted as the best design, materials, etcetera, come and go. Look at all the changes to tennis rackets, skis, bicycles, and diving fins in the last thirty years. Fact is, the ones from thirty years ago mostly do the same as the ones now. In my opinion much of this is spin and marketing hype for the purpose of selling people replacement products. I've seen diving fins go from vented designs, to non-vented, and then back again in this time. Admittedly there are many improvements to materials in this time frame, though function mostly remains the same. I made a wetsuit more than thirty years ago that remains very similar and as functional as the new ones today - except for the colors and wear. I did it to save money I did not have, and I was successful. Only real problem after thirty years is that it seems to be a very tight squeeze to slip into these days! :)

Another factor that has not been considered is your economics - possibly a good reason for your ambition in the first place. My wife comes from Ukraine, not so far from Croatia. In Ukraine, $100 US is a month of wages for a medical doctor! So go ahead and spend a month if this is your economics. The Italian product whose website you linked is definitely not worth several months of salary! Any reasonable person would see that. Experimentation and creation can be rewarding and educational. If it makes you happy all the better.

If you could find some thin high quality model aircraft plywood, you could easily experiment with shapes, flexibility, features, and blade to foot holder attachment issues. I believe you want to keep the flow going lengthwise and not across the blade with some form of ribs, whether they are reinforcing ribs or not. Then laminate your higher cost composite materials to match the characteristics of your best plywood prototype.

Carpe Diem and Best of Luck to You! John

[sigurd]

Probably oversensitive, yes! I probably didn't say my piece some time when somebody told me to spend on a "tried and true" insted of wasting time making something i thought would be cheaper and better. no matter, and if he goes to diving fora for help (good idea) i hope he brings here what he learns of these propulsors and their construction!

amortization and market mechanic is probably the main reason for the high C fin price. His fin may come cheaper than a "hi end" plastic unit. Come to think of it if I cut off my longblades and put carbon I bet they will improve. But the socks are sloppy and painfully tight so I probably won't sacrifice them.
Also, if I haven't tried fins before, then it will be next to impossible for me to choose the fin that I would choose a year from now. such, education is economics and if you can educate cheaply it goes faster.

But I digress, in this thread we should try to identify the desireables and solve how to make it so!

Far as I know it's only carbon/pox, no need for any combinated materials. It is just a flat spring with a sock.

About the channels, maybe they work a bit like winglets, reducing induced drag, or maybe they add thrust. maybe they add dynamic stability, roll or sideslip/yaw. Maybe they are hype. I can certainly see that it would be impractical with high AR bi-fins! I think the c4 site were trying to convey that it was a problem that the H sides added too much stiffness. my beauchat goldfin evolution has H edges (non parallell, as is the norm from what I've seen) from the same rubber as the sock only in the first 2/3 length. could be for better bond, certainly not very stiff. Then there are 2 little "kiteboard fins" on the top near the end. However I don't think beauchat have a monkey clue what they are doing with regards to performance. there are longi stripes of rough surface, and the logo is huge and embossed! clearly, there are enough idiot buyers that plain smooth un-pimped does not sell well.

I can't resist: this is the best backpack i've tried for its use, and it was my first made, locating parts in a 3rdWcountry for less than a beer here. But I am particular when it comes to feet and packs among other things. sorry for the hijack.

John ohlen, most all the examples of sport equipment you mentioned are relatively IMO very improved, top end and general, from 30 yrs ago.

[sigurd]

Some characteristics:

1: Angle from foot sole to blade. Does it depend on other characteristics or?
2: Width: Maximised against the tendency of the fins touching each other?
3: Stiffness distribution and length. Is torsional stiffness important?
Both stiff and long gives hp but tires the muscles, but what happens if stiffness and length are not balanced against each other? Should the tip be so soft that it has close to zero angle through the water, in order to not make lateral axis vortices?
4: Fragility.

I'd make them a bit longer than the ones I have, and too stiff, then cut and sand down later. Should there be any flex at all under the foot and close to the toes? If not it may be more feasible to use a ply core there to save carbon.

[diverdon56]

I have seen the locals in the Philippines useing two boards with strips of old tire's screwed to them for foot pockets. I have oceanic V-12's and I find them well worth the USD $160 I paid for them http://www.divingfrontiers.com.au/Dive%20gear/FIN%20PAGES/Fins.htm

Here is a list of top fins test results: http://www.divingfrontiers.com.au/Dive%20gear/FIN%20PAGES/Fins.htm

[Lovre]

Thank you guys for all the effort about fin design. Thats the part that I will try to resolve myself. But I need some help with technology and working with carbon and fiberglass,and thats what you are so much better than I am.

Someone mentioned only the money, that is not so much of a problem, but I don't want to pay so much money if I'm certain that I could come close to performance that commercial fins are offering, or maybe even get better than some of them.

Can someone tell me what I would get if I would make 200 gram fiberglass clothes and epoxy resin together? Only one layer ?
Can someone tell me what materials I need to put together ?
Can someone tell me about books or internet resource on vacuum bagging?
Would I need to use mold to make only blade 20 x 80 cm, made of carbon clothes, fiberglass clothes and epoxy ? Could it be done only in plastic bag ?
This is what I'm most interested in ... Is vacuum bagging the technology that I can use to make this high performance things ?