DIY Diving fins

Discussion in 'Fiberglass and Composite Boat Building' started by Lovre, Apr 24, 2007.

  1. Poida
    Joined: Apr 2006
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    Poida Senior Member

    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
  2. eyes
    Joined: May 2006
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    Location: Dominican Republic

    eyes Junior Member

    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"
  3. John Olson
    Joined: Apr 2007
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    Location: Northern California

    John Olson Junior Member

    Carpe Diem!

    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
  4. sigurd
    Joined: Jun 2004
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    Location: norway

    sigurd Pompuous Pangolin

    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.

    Attached Files:

  5. sigurd
    Joined: Jun 2004
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    Location: norway

    sigurd Pompuous Pangolin

    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.
  6. diverdon56
    Joined: Apr 2007
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    Location: buffalo

    diverdon56 New Member

  7. Lovre
    Joined: Aug 2006
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    Location: Croatia

    Lovre Junior Member

    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 ?
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