Selfmade fiberglass fins

[Dromilious]

Hello. I use peel ply but the finish is not smooth.What else i can use ?Release film ?

 

[REVAN]

The peel-ply will leave a rough finish behind. That's normal and common on most composite fin blades. Composite parts normally have a control side (against the mold) and back side (against the vacuum bag). If you want a mold smooth control finish on both sides, the only way to get that is to have molds for both sides and use an infusion/injection process to add the resin. It will be way more complicated and involved and it will only affect the esthetics of the fin. The vacuum bagged fin will work just as well, if not better, as it has a very well controlled reinforcement to resin matrix ratio.

 

[landshark sa]

Hello. I use peel ply but the finish is not smooth.What else i can use ?Release film ?

There are different types of peelply, some with a finer grain which will give a bit of a smoother finish but in the end you will still have rough / matte finish on the peelply side.

When used with infusion, perforated release film must be used in order to get resin into you reinforcement layup. The perforations will leave a pattern and you will also, depending on what type of cloth you use, get weave pattern print through.

RTM or Resin Transfer Moulding will give you smooth finish on both sides but your mould will have to be specifically designed and built to allow adequate resin flow through the whole part.

If you have an oven / heat box that can handle reasonable temperatures (above 100 deg C) low temperature prepreg in combination with vacuum bagging can be used but you will end up with a slightly resin rich part that although it will look better than a standard infusion won't be as strong.

The best way of getting a smooth finish on both sides is using an autoclave but this is outside the scope of most diy projects.

 

[Dromilious]

Thanks landshark for your reply and you Revan !So there is nothing i can do ,with this method i work i will always have a rough side ! I don't find it ugly but of course the other smoother side is perfect .

 

[landshark sa]

Not much really.

You could add a coat of resin after but it will still not have the same finish as the glass side and you could also then end up with the resin blushing because it was not through the same cure cycle as the the blade itself.

You could also spray on a clear coat over the peelply side but again the finish won't be the same and it will wear differently to the glass side so may look shoddy after some use.

 

[Dromilious]

I buy all the products from Fibermax . They have a variety of peel ply .I have used VC009 .I wonder what the VC007 and the HT 260 are https://www.fibermaxcomposites.com/...language=en&osCsid=seov8uve0q49mksghu857on0l6

 

[landshark sa]

It looks like different weight fabrics, so for sure they will give a different finish but what the difference is I can unfortunately not say.

Best will be to get some samples and do a test.

I see you are using carbon for all you tests - pretty expensive way to work through the learning curve. I highly recommend that you do your testing with normal glass fabric - it works out MUCH cheaper!

 

[REVAN]

I see you are using carbon for all you tests - pretty expensive way to work through the learning curve. I highly recommend that you do your testing with normal glass fabric - it works out MUCH cheaper!

I second that. In fact, I think fiberglass makes a better fin blade anyway. The design of the layup and taper of the fin blade is WAY more important to the fin's performance than is the material choice of carbon vs. glass reinforcement.

 

[Dromilious]

This is the blade ! You can see from the back the difference from the rough surface and the uper section i used vaseline to get it more shiny.

 

[Dromilious]

Finally i made 2 pairs of blades and tested them yesterday.
The 1st pair is 100% carbon fiber with plain and twill weaving styles and different areal weight, combination.
The second pair is a hybrid carbon-kevlar .The up and down layers are 61% carbon / 39% aramid twill 2X2 and inside i used 100% carbon layers .I am very excited with the performance and how agressive the blades are.
Next step is to try to find the ideal footpocket to match them .

 

[REVAN]

I am very excited with the performance and how agressive the blades are.

By "agressive", do you mean stiff?

Don't underestimate fiberglass as a reinforcing material. I actually think it is the best known material to use in diving fins. It's not hydroscopic like aramid and carbon fibers and will be more resilient against water and freeze damage. Plus, it is more flexible than carbon and has better energy return than aramid composites.

Consider a fiberglass and carbon hybrid layup with the carbon reinforcing used near the foot attachment and the fiberglass laminating the outside of the blade and all fiberglass for at least the last 8 to 10 inches of the blade.

 

[Dromilious]

Agressive i mean the energy return.I agree with you.I noticed that fiberglass is more flexible so my next project will be a hybrid carbon-fiberglass.

 

[landshark sa]

Well done on creating your own fins!!

I fully agree with Revan. For fins, fibreglass is a much better choice as a combination with carbon than Aramid / Kevlar. Aramid is not great with UV so UV degradation and discolouration on your outside layer will be an issue even when you use UV stable resin.

There are materials out there that exhibit better characteristics (hydrophobic, UV resistance) with similar tensile strength that are also much easier to work with than Kevlar.

 

[Dromilious]

Hello there! These days i am working on a new fiberglass blade. I used 390gr twill fiber . This time i tried the vacuum infusion resin and i used vinylester because it is cheaper and it is a test project to see if i can do a correct vacuum resin infusion.
I used 5 layers af 390 gr twill and 2 layers at X position .Also 1 layer at the top -about 25 cm length- for reinforcing the footpocket area.The vacuum is at -1 bar . The temperature was 18 oCecius for 12 hours and for the last 12 hours is 45-50 oCelcius.Some photos of the process.

 

[daweasel]

Hi there !
I'm interested in starting my own fiberglass fins project and have a question (and will probably have a lot more in the coming weeks/months !) :
Do you guys have some feedback on long-term (multiple years...) durability of homemade fins ? Like how are they aging comparing to fins of known brands ?

 

[daweasel]

I forgot my other question : I see epoxy is the most recommended resin but does someone have more detail about which epoxy to use ? Because on the website I went on, there is a multitude of choices (standard, surf, high performance, flexible,...)

 

[CarbonSpearo]

Hello! I am currently making carbon fiber/fiberglass fins for a project at school. Do you guys know where to get the rubber rails for the side of the fins? In addition, any information you guys can give about tapering the fin would be greatly appreciated. Thanks!

 

[daweasel]

@CarbonSpearo Hi ! Seems like experts are away for the moment, so you'll have to do with my newbie answer.
I found some water rails on Diveinn, there is multiple models and prices but those seem to be the cheapest : https://www.scubastore.com/scuba-diving/sigalsub-t-profiles-for-blades-4-pcs/136455561/p
I did not yet try them though...

 

[CarbonSpearo]

Nice! Those look like they will work just fine!

 

[landshark sa]

Hi there !
I'm interested in starting my own fiberglass fins project and have a question (and will probably have a lot more in the coming weeks/months !) :
Do you guys have some feedback on long-term (multiple years...) durability of homemade fins ? Like how are they aging comparing to fins of known brands ?

I'm no expert but I'll chime in anyway...

As with off-the-shelf fins, I have self made fins which broke after very little use and I have fins I made quite a few years ago that are still going strong.

Unfortunately I don't have any empirical stats, i.e. fin A lasted 10000 kick cycles compared fin B which lasted 8000, but for sure it's possible to build diy fins that last as long and work as well as known brands, the trick is to find that perfect match between performance and durability - something that takes A LOT of reading, learning, experimentation and testing.

I forgot my other question : I see epoxy is the most recommended resin but does someone have more detail about which epoxy to use ? Because on the website I went on, there is a multitude of choices (standard, surf, high performance, flexible,...)

There are so many different types of resins, each with different properties, it's actually a huge field in itself. If you do decide to go down the rabbit hole of composite development, it will be best to use the resin technical specification sheet to do comparisons between them in order to find what will work the best for your design and for that you will have to know how metrics such as tensile modulus and strength, flexural modulus and strength; interlaminar stresses; elongation etc impact your design.

Probably the most import thing is, you want match your resin to your reinforcement - for example carbon fibre can handle a lot less elongation than fibreglass so you want to resin to be able to work well within the parameters of your material.

Some other things that I can think of off the bat that may not initially be obvious:

As its dive fins which could possibly spend a lot of time outside you want UV Stable resin.

Match the viscosity of the resin with the application method - i.e. for infusion you want a lower viscosity as the resin has to run through the whole part.

Consider your work environment. In a diy setup where one doesn't have a perfect temperature and humidity controlled lab to work in you may want to compromise on ultimate strength vs flexibility handling the resin.

If you are beginning, look for a resin that has a longer pot life. Although these type of resins usually take longer to cure and possibly require post curing they will give you more time to figure things out and optimise on the fly like routing up infusion lines etc and will provide more flexibility to guard against uncontrolled exothermic reactions.