Selfmade fiberglass fins

[Amberjackass]

hi all, I was thinking of building a fiberglass fins for spearfishing with infusion system,
hardness:medium.
I'm 1,83 cm for 80 kg weight.
How many layers i have to use?
of which thickness ?
Thank's before

 

[Mr. X]

Anybody tried 3-D printing fin blades yet?

 

[landshark sa]

hi all, I was thinking of building a fiberglass fins for spearfishing with infusion system,
hardness:medium.
I'm 1,83 cm for 80 kg weight.
How many layers i have to use?
of which thickness ?
Thank's before

The problem is one manufactures medium is not the same as the next. So it's best to work from something that you have already found to work well for you.

A very rough estimate of the amount of layers needed is to take an existing fibreglass fin with the characteristics you like then measure the thickness and calculate the amount of layers needed based on the fibreglass cloth you have.

So for example, I have a set of Spearmaster fibreglass blades which is rated as medium. At the very back (foot pocket side) they are 2.14mm thick and that the front 1.02mm.

So if I where to use 200gsm twill weave fibreglass with a thickness of 0.2mm:

2.14mm / 0.2 = 10.7 layers at the back
1.02mm / 0.2 =5.1 layers at the front / tip

In practice my layup will be: From the back 11 layers of fibreglass staggered so that I end up with 5 layers at the very tip.

As I say this is just a rough estimate, you'll have tune the layup quite extensively in order to get a fin that works well for you.

 

[REVAN]

Don't just copy what others make. If that is the plan you should just buy what they make.

Use more taper than usual. I don't think blade makers have been making the fins soft enough at the end. Regardless of how thick the fin blade is at the root, it should be very flexible at the tip (probably more like 0.5mm than 1.0mm thick in most composite materials). It should be so soft the last 6 to 8 inches of the blade that you think it's not going to be able to make any thrust. That's when it is soft enough, because it shouldn't make any thrust. The end of the blade should only direct the thrust to point the right way, not try to make it.

 

[Amberjackass]

how can I design the staggered layers of mat, the distances from the tip, the thickness, etc.? have you a standard reference scheme for the layers?

 

[REVAN]

how can I design the staggered layers of mat, the distances from the tip, the thickness, etc.? have you a standard reference scheme for the layers?

The layup of the laminate is dependent on the materials and weaves of reinforcing fibers that you use. You can take engineering classes that will teach you how to design and predict structural properties of composite layups. There is a lot of matrix math involved, and you have to have some idea of what you want structurally from the fin before you start designing.

Most people who make fins will just pick a set of materials and make 4 or 5 version until they get something that works the way they want. This is why I said that if you want what something that is already made by someone, just buy it. By the time you manage to faithfully duplicate it, you will spend a lot more money trying to get it right. Get into prototyping and fabrication for the right reasons (hint - it is not for saving money, it's to create something that doesn't presently exist).

IMO: Vacuum infusion is unnecessary overkill for making fin blades. My recommendation; just make a wet-layup by hand, and use peel-ply and debulking mat in a vacuum bag to compress and debulk the layup. The end result is just as good and it is a lot easier to do for small jobs. Infusion involves a lot of setup and flow design. The infusion method becomes advantageous for large production jobs. Not so much for what you are going to be doing. Another piece of advice - work with fiberglass and vinylester resin. I think fiberglass makes better fins than carbon, and I also think vinylester will be better than epoxy for making flexible fin blades. - Free advice if you want it...

 

[Rafael Abella]

Revan,
Great comments, specially this one: (hint - it is not for saving money, it's to create something that doesn't presently exist)
But the only thing I will say is: if you are not post curing vinyl-ester is a great option but if you posture the epoxy you will have a better product, you will need to look for a better epoxy than just wood glue epoxy, some epoxy with higher Tg.

 

[Rafael Abella]

hi all, I was thinking of building a fiberglass fins for spearfishing with infusion system,
hardness:medium.
I'm 1,83 cm for 80 kg weight.
How many layers i have to use?
of which thickness ?
Thank's before

Like Revan said, do not infuse small parts, wet vac is all you need to do.

 

[REVAN]

Epoxy is stronger than vinylester and has a higher modulus of elasticity. But strength is not what we want from fins. We want flexibility. Granted, this is just a hunch of mine, as I haven't tried it myself. I make my fins differently. But, if I were going to make custom laminates for bi-fins, I'd start with the fiberglass and vinylester. It is less expensive, and I think it will have a really good chance of being better than epoxy. If nothing else, it is less viscous as a resin, so it will start with fewer bubbles in the layup and it will debulk and compress easier when you vacuum bag it. Statistically, I think it will be easier to get good parts, and the parts have a good chance of having superior flexible properties.

FYI: The fins I made are like this (quite a bit different from the usual)

 

[Rafael Abella]

Vinylester is a hybrid form of polyester resin which has been toughened with epoxy molecules within the main moleculer structure
Epoxy resin has far more to offer in its ability to flex and prevent delamination. Using epoxy resin leads to better quality products.
In areas that must be able to flex and strain WITH the fibers without micro-fracturing, epoxy resins offer much greater capability.

Interesting concept, do you have pictures from the ones you made?

 

[REVAN]

Interesting concept, do you have pictures from the ones you made?

 

[Rafael Abella]

Hi Revan, looks great, will love to test it one day, thanks for sending me the pics and video.

 

[Afiev Dewanta]

nice thread.. hope this thread is never ending so any of you can show the finished fiberglass blade project..

this thread helps a lot of people btw. include me. haha

I'll give some shot, and post my fiber fin when I'm done the experiments

 

[RiaanLR]

Hi

I would like to know how the camo colors are put into freediving fins. Or any design for that matter.
Is it a cotton type of cloth?

Thanks for a great thread. Helped me a lot.

 

[Dromilious]

Hello people have a happy new year! I tried to make carbon fins but as you can see i have this problem.I have tried before with fiberglass and i had the same problem .I don't use vacuum but pressure and the resin is layed with a brush .I use 2 layers get coat for release only with no wax.Also i used bubble roller for the air . Do you think i need to apply more resin to be richer ?It seems to me like air bubbles created stoping the resin to infuse in the carbon.What is your opinion?

 

[REVAN]

Do you think i need to apply more resin to be richer ?It seems to me like air bubbles created stoping the resin to infuse in the carbon.What is your opinion?

No. More resin will not help.

You need to use a porous system to extract the air bubbles and excess resin. Buy peel-ply, usually made from woven mesh polyethylene. Lay down the peel-ply against the free side of your wet layup, and then a bleeder material on top of that. Often people will use a perforated polyethylene sheet and a breather on top of that to get even pressure. Then bag it and vacuum to 21 in-Hg. Those air bubbles and the excess resin will extract through the peel-ply and into the bleeder material where you can peel it away after the resin cures. Your fin blades will come out consistently strong and beautiful.

Using pressure instead of a vacuum can also work, but not as well. If your molds are about 1m x 0.25m, the vacuum pressure will be similar to the pressure of 700 Kg of mass resting evenly on top of your mold. I'm guessing that you are not using that much pressure and probably have no method of applying that much with weights or by mechanically squeezing. Vacuum pressure is the easiest way to do this, and that's why everyone uses it.

Oh - and wax your molds! It's the last line of defense against having to discard them and start over from the very beginning.

 

[Dromilious]

Revan thanks for your advice.For squeezing my metal mold i use 5mm of sheet metal using bolts and tighten them with my black and decker at full newton scale.I bought yesterday a vacuum pump with 1/4 hp power and i plan to use it in the next few days.As i can see vacuum is the most reliable and safer method for this kind of job.For the first time i will use hand lay up and vacuum .In the future i will try and the infusion .More pictures will come when i start the new project.My manometer is in bar scale ,21 inhg is about 0.7 bar i guess.

 

[Dromilious]

Hello.this is my second vacuum try .The first one had air leakage and i couldnt stop it so i bought today a vacuum bag for clothes .

A friend told me that the best is to use an oven and start from 40 o Cecius and increase the temp every 30 minutes gradually to reach the 80 o celcius.After about 4 hours the blade will be ready for dive or else it needs about 2 weeks for the resin to dry .What is your opinion?

 

[REVAN]

If heated too hot, a resin's strength may be compromised.

Some resin systems are designed to use a prescribed temperature profile to properly cure. These are usually high strength and/or high temperature resin systems. Look for what the manufacturer of your resin prescribes to determine what to do. Most room temperature set resins can be safely heated to about 150F (65C) and achieve a rapid cure. I have a hot box I use that heats to the 140 to 150 F range. This will cure my room temperature resins in about an hour (2 hours if the mold makes a large and cold heat sink that needs to warm).

On sealing a vacuum bag leaks, get tacky tape to seal it up. It is also good to have a bag full of small clamps that can be used to squeeze the tacky tape if the bag isn't sticking good enough (very useful for when the tacky tape gets old).

 

[Dromilious]

Hello.Indeed Vacuum bags are leaky .During the night the pressure went to - 0.3 bar. Also the temperature was not ideal ,about 12 o C.But i used a selfmade oven after taking out the peel ply and the breather.I cured at about 45 oC for 3 hours.Next project will be much better and accurate with a temperatre controller .In this project i used 200gr/sq carbon fiber 2x2 twill.2 layers top and bottom and in the middle 2 layers at x position.Also I added and one 15x15 cm piece at the top .The result is a very soft blade that is not usable.It needed at least 1 more layer to catch the soft hardness.