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.