Disclaimer 1st: I haven’t (knowingly) ridden other plastic fins than FCS.
But, I distinctly remember using Lexan, or similar plastic, for side runners on the Eaton bonzers we were glassing at Channin. In fact, I believe the sander(Ed Hagan) was cutting the glass, and glueing them in with hot glue(?). They were sanded down to I think 600, just on leading/trailing edges.
Anyway, they were super clear, and stiff. Granted they were also only 2 5/8 or 3 1/4 tall…
Might try a set, and see what happens. Can’t hurt, much.
Quote:
Primospire is an UNfilled ( so no fibre or filler reinforcement) transparent thermoplastic, it is nearly 3 times 'stronger' than aluminium or carbon steel.
2 X stronger than Stainless steel.
And just not quite as good as Titanium.
Suitable applications are aerospace and surgical components.
Primo… may be at the high end of quality unfilled plastics but some unfilled ones are just as strong as the popularly used lower grades of plastic that are beefed up (strengthened) with fibre reinforcement.
You dont need fibre filled fins to make suitable surfing fins.
The “Wavegrinder” fin is polycarbonate, and at any big Sydney boardshop you’ll see heaps of other polycarbonate fins on the shelves, been around for 20+ years, they are the funky see-thru coloured ones, mainly lots of big longboard fins.
S.
Primospire is about the same stiffness as fiberglass.
But how much $$?
The others, Lexan, high density Nylon, delrin, ultem, are all 2-3 times less stiff than glass. If you make a replica of a glass fin with one of these materials the flex will make a noticeable difference. I didn’t like it. I never liked the unfilled plastic FCS fins like the G5s or Occy’s because I felt the flex gave too much away. Lexan fins do have a cool “icicle” look to them, though, so there is that.
As for molding fins like the Wavegrinder…I suspect they are at least partly filled with glass to raise the stiffness.
I really don’t want to dissuade people from making custom plastic fins. But they should not kid themselves that the same dimensions as a fiberglass fin will be equally suitable, or that the materials are as stiff as fiberglass or even stiff enough for most surfing applications. I think if you wanted to make FAT 1/2" thick thruster fins, plastics would probably be stiff enough. Possibly a bonzer side runner, I dunno.
I just never felt like doing a fin layup (which takes less than an hour) was that much work to get 3 sets of thruster fins or 3 large singles.