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Nice post Spuuut, look forward to reading more, now I’m off to look for plastic road signs to steal um I mean recyle.
Great thread, I made a 6" squirrell fin recently from 12mm lexan. It extended the range of my 7’6" bonzer egg. The thing now flies in mush and small waves. It chips easily though.
I used a hard backing pad and 40grit paper for the foiling.
s.
we are dying to hear how to make 2 identically foiled fins, with in and outside foils!!!
thanks for sharing with us
w.
cool info, thanks for sharing.
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Polycarbonate is the ‘bulletproof’ clear plastic that they use in banks. Its strong and you can mill ( shape) it with slow tools like sandpaper /drill/ handsaw.
Is it possible to get the finished fin clear again after foiling/sanding? Any info wrt the flex characteristics of this material?
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(this is a great thread) So the only downside of plastics vs fiberglass I see so far is that you don’t get those layer lines that fan out so nice and show you how your foil job is going and tell you where to feather in to smooth it out etc. Love watching those lines appear and walk their way across the fin. Oh well. Heck of a lot less work and cost than fiberglass. No laying up of panels of expensive materials…
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…so somewhere in here we need discussion of flex characteristice. I imagine different plastics have different flex. Any readily available plastics have nice snappy memory similar to glass/resin?
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To all the foilers,
All the info is g8 but practice is were you should focus after 10,000 fins foiled I think you have to start at the beginning and practice get your self partical board our old scrapes of MDF cut out your template and practice nice even strokes from tip to base. I have a stand, 60 drum with a bag of concrete in it ,a post in the wet cement and an engineers vice attached to the top at elbow height. This bull shit about chord lines and marking your fin surface is a crouch which you will not stop if you use it. If you have fingers and eyes you will get a better fin in the end. FEEL THE SURFACE AS YOU GO.
LOOK AT YOUR FOIL AS YOU GO dont start on fibreglass and resin do 10 or 20 wooden prototypes you will learn a lot more by foiling up wood and if you make a mistake into the bin with it
when you think your close to the standard foil hold it up to the wall of your shed to check out the lines of the foil and keep stepping to finer paper remember PRACTICE PRACTICE PRACTICE.
Rod
finfektion
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...so somewhere in here we need discussion of flex characteristice. I imagine different plastics have different flex. Any readily available plastics have nice snappy memory similar to glass/resin?
Fiberglass stiffness can be achieved with some exotic plastics (PEEK), or some very common plastics filled with glass.
It is a REAL b1tch to work with glass filled plastics. They are both tough to work and tend to melt, the worst of both worlds. The exotic ones like PEEK are also difficult to work with and as an added bonus cost a lot.
Stiff plastic fins are glass filled plastics. Up to 60% glass by weight. Glass filled plastics are easy if you are molding pop-out fins.
The other way to get stiffness is to make it thicker.
Most of the foilers I know use small angle-grinder style sanders with rough grits and soft pads (28 grit on a soft pad), 4 or 4.5 inch diameter. Some put the grinder in the vise and hold the fin, others put the fin in the vise and hold the grinder.
I always follow contour lines and make longitudinal strokes. You can get to really good fin foiling with just a dozen fins or so if you do. It is definitely a more mathematical approach. I made some series with the wide point further forward and further rearward, and ultimately decided in my application a WP 20% worked real well, better than the industry standard between 25 and 30%.
There are HEAPS of fiberglass fin making tips in the archives. HEAPS.
The better fin foilers do a fin in 2-3 minutes MAX. These are pro fin makers. No nonsense. I take about 20 minutes to do a thruster set (single foiled) with a few dozen sets under my belt. If you are starting I would be happy if my tenth fin was decently rideable…that’s a good goal. And I would start with glass layups not plastic or wood.
YMMV and I HTH.
…well, Im a board builder
and I foiled (foil) several hundreds of fins (fiberglass and several wooden ones) may be Thousands; and I tell you that I spend 20 minutes in a thruster set too
but the worst part is cut the outlines from the panels…I really hate that
some one said that he goes from tip to base
well, I sand from base to tip, its easy and fluid
I used a metal bandsaw for cutting the fin panels out. I make my templates on the computer and print them. Then I cut them out with scissors (here is where kindergarten came in handy). Tape them to the fin panel, mark with a sharpie pen, and cut them out right quick on the bandsaw (made for cutting metal, not wood). If you were making that many fins I would highly recommend it. I had access to a large machineshop for my work, so I tried lots of high end tools to get the job done. A bandsaw is not that high end.
I found the angle-grinder to be a much nicer tool than a belt sander (not to mention easier to control the dust).
The basic plastics, delrin, nylon, polycarbonate, are all substantially weaker in modulus than fiberglass. If you try to make a fin using normal dimensions with such a plastic it will be WAY too floppy for serious surfing.
The fin companies are ALL using glass filled plastics in their stiffer fins. That means you cannot reasonably make fins like those from FCS or Futures by hand, because hand-shaping glass filled plastics is a royal pain. You need to make a mold, and mold them. Or just deal with the difficulty in working with glass-filled plastics.
I did all my R&D on fins (templates, thicknesses, foiling) using plain-jane glass. I think it is the best approach for ease of getting a reasonable result, and starting with materials that are most comparable to those used in surfing. YMMV.
I agree that doing R&D in the garage is quite rewarding. Its easy to screw up in many ways that others probably had not thought of, and I sure did plenty of that! But with consistent practice comes understanding, and that is the cool part.
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OKay some honest answers to some questions about foiling sheets of plastic.
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Yes, you can get a glossy finish on sanded polycarbonate. You need to sand to finish surface to 400 grit and flash it with torch. It will gloss right up.
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No, you can’t get the same physical characteristics as injection molded plastic of the sametype for two reasons. a) When injecting plastic into a mold we’re packing the mold shape out at several thousand psi and flowing into the contours with a uniform pattern. b) the control we have over the tool movement is with in 2/1,000,000" in three axis.
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Unfilled polycarbonate breaks in shards and can be very nasty.
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Hand shaping laminated panels is a great way to test out new shapes with stiffer flexular modulus than most plastic sheets and definitely more cost effective.
But, you can make some pretty fins useing polycarbonate sheets and shaping them to your ideal foil.
Plastic seems to me a great way to whip out a bunch of different templates and test the shapes only but in answer to
“You dont need fibre filled fins to make suitable surfing fins”
There’s suitable and then there is suitable. My flex question was directed at more for those needing flex like in a ferinstance Liddle fin or such. Glass and pu and glass and epoxy each have their twangy stiff flex patterns. I haven’t seen fins like a GGIV in plastic. Perhaps there is a reason besides lack of market for them?