• Welcome to the DeeperBlue.com Forums, the largest online community dedicated to Freediving, Scuba Diving and Spearfishing. To gain full access to the DeeperBlue.com Forums you must register for a free account. As a registered member you will be able to:

    • Join over 44,280+ fellow diving enthusiasts from around the world on this forum
    • Participate in and browse from over 516,210+ posts.
    • Communicate privately with other divers from around the world.
    • Post your own photos or view from 7,441+ user submitted images.
    • All this and much more...

    You can gain access to all this absolutely free when you register for an account, so sign up today!

Selfmade fiberglass fins

Thread Status: Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.
Hello, well first I want to congratulate you on taking on souch a rigorous project. I was also interested in making my own fins, and was wondering if you could make a step by step instructions of the construction,and some of pointers of what to do and not do. please
 

I have planned to write down the instructions including pictures and video. But I would like to make the final iteration first. The last one is OK and easy to build, but I would like to make the fin tip a little softer - exactly as I want it to be.

I am planing to make it over the weekend.

Zmago
 
Reactions: trux
rtena said:
could you also tell me how to build a vacuum pump please
Click to expand...

There isn't much to tell. Find an old fridge and remove the compressor:


Then buy a plastic tube. Connect one end to the vacuum side of the compressor and the other to the vacuum bag.

Vacuum bag in my case has bottom side made out of ordinary 4mm glass and the top out of PVC foil. Use a two sided scotch tape or silicon glue to get an air tight seal.

Between the wet fibres (covered with peel ply) and PVC cover add a breading material. You can use paper towels (5 layers or more). That will provide vacuum to all the area, and suck in the excessive resin.

Search the youtube, There is a lot about vacuum bagging.

Just an example:
[ame=http://www.youtube.com/watch?v=mgBSMmqzSJM]YouTube - How to vacuum bag epoxy laminate[/ame]

Zmago
 
Zmago, Your fins look great!! I would nominate you for the manly man awards !! Thank you for such a great thread and keep up the innovative spirit!

:friday
Cheers, matt
 
Hey,
I am planning on trying to make a pair of blades like this,
Could you please post a picture of how you laid out the fiberglass strips.
Also, what type of fiberglass did you use, (weave and thickness) and what type of epoxy did you use?
Thanks in advance, Pat
 
Last edited:
Hi all!

I am running against clock lately and I couldn't write the manual I promised.
Well, I am planing to do that this weekend.

In most of the fins I used 200 and 280 g/m2 twill glass cloth, 600g/m2 UD (100 mm wide), low viscosity epoxy for RTM and PVA demoulding agent.

Zmago
 
Here it is, the final one.
It weights 300g, of witch 195g is fibre content! Find that on any commercial one.

[ame=http://www.youtube.com/watch?v=ANVog4R7iAM]YouTube - Making a fiberglass freediving fin - part 5[/ame]

Zmago
 
Very nice job Zmagoj!! What about that step by step process you promised us? The last video is great but I have no experience in this, and I have to solve this puzzle alone by checking out other videos on Youtube.

Summer is coming here in Greece, so come on neighbor, give it a try!!
.....please???
 
Well, I've thought that the video gives a clear enough information about the process. I agree, didn't include the details of the mould construction and fin layout since I assumed it is a straightforward process.


If you want more thorough information about a specific detail just ask and I will try to answer and also include the information in a possible future video.

Zmago
 
Hi Zmagoj, you just need to make one more post & we can then give you deeper blue reputation points.
(you need to make 25 post before you can join our points sytem)
 
I've stumbled over this searching the web:

Google Prevedi

I don't want to advertise the product! (Hope they will fund my experiments though)

The site is of my interest because they have revealed the carbon layers from which their fins are made of.

If you want to build a carbon fin use the tech I described with the carbon layers shown on this page.

Btw.
The second pair of my fins is in the annealing phase and will soon see the water.
There it comes, my 25th post; If you believe I really care

Zmago
 
Last edited:
hi zmagoj,

i have left a comment on your youtube video and you asked to continue any further questions on this thread !

you say in your answer that having in mind cost and performance that you prefer fiberglass over carbon.

have you made any experiments (swimming etc) with both carbon fins, and the fiberglass you have made and how do they compare to each other ???

very interesting to hear your thoughts and ideas !!

Thanks,

George
 

hi,

i odnt actually read all topics here...just a few here and there...

the one you mention i havent read !!!

thanks for the link....

ill make myself a frape (cold coffee) and read it !!!
 

I will try to answer this one in a more thorough way. I am not an expert in composite’s mechanic, so I could be wrong at some point, but I have a good general knowledge over general engineering mechanics.

1.What is a good freediving fin?

A good fin is the one that absorbs the energy of the kick and returns that energy at the end of the kick (spring effect) – good efficiency. A bad fin (cheap plastic) would transform most of that energy into heat – bad efficiency.
Besides the energy return there is also the concern of proper stiffness, which will be described later. The stiffness is a matter of the thickness of the blade and the Young’s module of the material. It has a very low effect on the energy return of the fin itself. However, the stiffness has an effect on overall efficiency – the diver and the fins.

To conclude: You need the fins with good energy return (depends on material and building technology) and proper stiffness that suits your needs.

2. What are the differences between glass, Kevlar, carbon fibers?

They have different strength values – the values at which the fibers break. The values are not really important, because the stress inside the fin material is far lower than these values (for any composite material).

They have different stiffness coefficients determined by Young’s module:
Young's modulus - Wikipedia, the free encyclopedia
Carbon has higher module than glass, what results in thicker glass fin comparing to the carbon one – for the same stiffness. But that is a concern for the builder not the user. It is true, that thicker means more resin and therefore more energy transformed into heat, but only a very small amount.

To conclude: If you are not a real professional diver you won’t notice/feel any difference in performance.

3. What is the price difference?
Huge if you ask me. You can make your own calculation from this catalogue (R&G):
http://download.r-g.de/catalogue_2010_en.pdf

4. Conclusion
It is all marketing not engineering!

I will also write a builder’s view on carbon/glass differences in next post, where the carbon has some advantages.
 
Last edited:
As I said, this post will describe carbon/glass fibres through builder/designer's point of view. I've got the knowledge from experienced builders and from my own trial-error attempts.

To get high energy return fins, the unidirectional fibres should be used (regardless the material). The fibres must be orientated along the blade. A biax or twill cloth may be used only on the surface layers to get a compact laminate.

There is hidden the drawback of glass fibres.
You can easily get unidirectional (UD) carbon of many different weights and sizes. Glass UD is hard to get, especially heavier then 500g/m2 and if you succeed and get it, it is pre-impregnated for polyester or vinyl-ester resin. Epoxy doesn't wet out the fibres completely. Using carbon, you would not even know for these difficulties.

However, I managed to find 600g/m2 UD, but is only 100mm wide and two strips are needed to cover the blade width. The wet-out problem was solved using low viscosity resin for infusion, which was heated up (and also the mould) to 35°C to lover the viscosity further. The pot time of this resin is 300min at 25°C - a very long time also helps to wet out the glass cloth.

Using the steps above, I managed to get a nice transparent laminate from cheap glass fibres. It would be much easier to use carbon, but my wallet (and health) still screams NO.
 
Last edited:
gserghiou said:
hi zmagoj,
have you made any experiments (swimming etc) with both carbon fins, and the fiberglass you have made and how do they compare to each other ???
George
Click to expand...

No, I am just a rookie in diving sport. My writing is more theoretical then practical. It would be interesting to invent an experimental method which would compare the blades in real life. It would be worth a PhD also.
 
We were talking the other day about how to rate fins. This hard, medium, soft or 1, 2, 3, etc is not very scientific and in fact purely subjective. I wondered if a simple measurement of their resistance to bending would be a starting point. Fishing rods are often measured like this. The amount of force required to bend the tip to 90 degrees of the butt is called the test curve and is usually in pounds. As rods are a bit like fins in that they transmit force through bending and are made from carbon or glass fibre seems a good starting point. So how about rating fins in pounds for their test curve. I know it wont tell you everything about a fin (as it doesn't with fishing rods) but it is a start and it's measurable and scientific.

Ye? No?

Dave.
 
You must log in or register to reply here.
Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…