Fin Foiling

General Discussion
1

Preface note:

Ben ~ chipsfish61 asked me to begin a fin foiling thread and discribe how to get through the process.

There a many ways to approach the process this one is what works for me.

Saftey glasses and dust protection is a must. The best way to get rid of fiberglass on the skin is first top blow it off with high pressure air. Then put the GoJo on scotchbrite pad and scrub with cold water. It works pretty well.

It seems to me that starting with a symmetrical fin make the most sense. I like to have a central layer of colored material as a reference to work toward aids sighting for a symmetrical foil. Once the fin plug is cut out I find that fitting the fin tab into the fin box should be the first step. Once this is done it’s time get to the foiling process.

I use a couple of high speed 4" grinders, a low speed sander at about 1600 with a small soft pad, a 1"x3"x8" sanding block with 60 grit paper, and a dremel tool with a fiberglass cutting wheel on it. I start by fairing the outline of the fin with the 4" 24 grit pad and touching the tight spots with an 8" half round bastard file.

Trace the vertical cord on the fin with a posca pen.

With the dremel tool cut along the top of the fin tab to mark where the fin base foil will begin leaving some extra material to work into.

Start with the base of the leading edge and foil up into the tip leaving the leading edge slightly full.

Go to the base trailing edge and foil up toward the tip with nice even strokes.

Then thin the tip out.

Always work the foil from the edges back into the thickness of the fin. Working from the center will tend to leave gouges in the work that are hard to remove.

Leave extra material in the whole foil and then go to a 4 inch 80 grit wheel and fine tune the foil with the same order of approach watching the fiberglass layers manifest themselves. When I am about one layer from where I’m headed. I’m off the high speed work.

Take the sanding block with 60 grit and fair the whole foil the scratches tell the story. This step is the one that really trues all the machine work and makes the fin look like it should. Spend time sighting the work from all directions during this fairing process. The spots that are tough to work like the ones along the tab can be worked down with the half round bastard file. Wrap a piece of 80 grit around it the smooth things out.

Go to the low speed rotary sander with 80 or 120. I put the sander in a workmate with the paper down so I can watch the material come off the fin. I prefer to hold my work not the tool at this point. Here extremely light strokes and a very soft touch is the call. Look to have the fiberglass lines on either side of the fin be a reflection of each other.

Once it’s all foiled out if there are any surface bubbles put a finish coat on and fine sand again.

During the whole process stop regularly and feel you work. Those dusty fingers or the wet ones at the end of the process often sense imperfections better than you eyes. If you sighting the fin their no better background than the sky or letting the sun reflect of a smoothened surface.

Final sanding is done by hand with water going from 80~220~400~600 with soft rubber backing on the two course grits and finished with nothing but wet fingers behind the paper.

Keep in mind that once the materail is gone you can’t put it back very effectively so don’t hurry because your haste will deminish your sensitivity.

Good Surfin’, Rich

2

Thanks Rich !

would it be pushing a friendship if , on the next fin you make , you might be able to get a shot or two of each step you mentioned , please ?

I’m more of a visual learner , when I SEE it , as well as having the process described , it seems to “sink in better” for me .

The parts I have difficulty with , particularly on small side fins , are getting a nice even curve from front to back [when looking from the base of the fin up towards the tip , I seem to have an abrupt line where the rear edge foil begins ].

How far “in” from the trailing edge do you begin foiling ? Is it about halfway along the length of the base [“?cord?”] of the fin ?

And , do you sand the WHOLE fin , when finished , to “blend” those grinder / sander marks?

If so , do you sand from the base of the fin to the tip [vertical strokes] …that’s what I do , down to 600 wet and dry [sometimes even 1000 …] , but I still see scratches !

Anyway , I hope that’s not bombarding you with too many questions at once , Rich !

I REALLY appreciate you taking the time from your busy schedule to do this thread …thanks !!

Finfektion , Bert , Blakestah …anyone else making fins [Tom , Lokbox] …I’d love to hear from you as well …any fin tips [oops!] and advice you have that you’d like to pass on, would be gladly received !!

hope you don’t mind answering a few of my questions , either ?

thanks again !

ben

the "fabric inlay side fins I made recently "hummed " on a few lefts [backhand for me] this morning …so , I think I still need to “round” that foiling transition line I mentioned , plus thin the rear [? %?] of the fin till the hum goes…thoughts , comments ?

[if you like , I could scan a few of the fins that have given me …well , not trouble , as such…I’d just like to get more flow to / out of them …if that makes sense ?]

3

good onya…that is great info…can I copy and use it for my surfschool students?aloha cheyne

4

A tip fo making fish keels, I had a German guy teach us to make Boomerangs at High school, He used 1/4 or so inch thick 5 layer marine ply. The foil on a boomerang is much the same as a side fin on a thruster foil one side and flat the other. to keep the foil level and true use the glue lines . if the glue line is straight the foil is straight if the glue line is jagged or wavey the foil is jagged or wavey.

5

I would also find pictures to be very helpful (something like in the middle and end phases of sanding with the 24 grit disk then the same for the next grit).

6

Hey Cheyne ~Good to hear from you ~ Sure thing mate.

Dan and Chips – I’ve added a few tips to the text to help you visualize things. Frankly I don’t have the time right now to do a pictorial on the process. Sorry.

No Worries, Rich

7 
1. How far "in" from the trailing edge do you finish / blend the foiling ? Is it about halfway along the length of the base ["?cord?"] of the fin ?
  1. And , do you sand the WHOLE fin , when finished , to “blend” those grinder / sander marks? If so , do you sand from the base of the fin to the tip [vertical strokes] …that’s what I do , down to 600 wet and dry [sometimes even 1000 …] , but I still see scratches !

thanks ! ben

8
  1. How far “in” from the trailing edge do you finish / blend the foiling ? Is it about halfway along the length of the base [“?cord?”] of the fin ? <<

Blend the whole fin. It’s the only way to get a true foil. Flat spots are dead spots.

  1. And , do you sand the WHOLE fin , when finished , to “blend” those grinder / sander marks? If so , do you sand from the base of the fin to the tip [vertical strokes] …that’s what I do , down to 600 wet and dry [sometimes even 1000 …] , but I still see scratches! <<

Follow the same proceedure at ever stage. Always start at the base of the fin at the outside edge. When grinding vertical strokes work best during the majority of the foiling but you can do some fine tuning with a soft horizontal strokes when you working the central part of the fin. Block sanding is done at several diagonals and the edges can be tuned with the file. The soft pad a slow speed with 120 or 150 gets rid of the deep scratches followed by hand wet sanding.

Happy foiling, Rich

9

thanks Rich !

…I definately need / want to buy myself a dremel , for those fiddly areas , like around fcs tabs …

 ben
10
Quote:
1. How far "in" from the trailing edge do you finish / blend the foiling ? Is it about halfway along the length of the base ["?cord?"] of the fin ?

The foil must run end to end, the full length of the chord.

Most of the foiling with the grinder, the grinder along the major fin axis ie: from base to tip. Light touch-ups going the other way are necessary, but BE CAREFUL.

I mark the max camber point - or point of maximal thickness - on the fin and use that to guide the foiling process (Rich says he does this with a Posca pen above). This will be between 20 and 40% back from the front of the fin. At least one major fin manufacturer claims he uses 25-30% on just about everything as a happy medium.

Quote:
  1. And , do you sand the WHOLE fin , when finished , to “blend” those grinder / sander marks? If so , do you sand from the base of the fin to the tip [vertical strokes] …that’s what I do , down to 600 wet and dry [sometimes even 1000 …] , but I still see scratches !

thanks ! ben

Hand sand with 220 and gloss it, and it’ll look real purdy.

11

chipfish61,

I’d like to like to help you out. But, the tools I use are kind of expensive. Then there’s all this math. And, finally you gotta hand sand steel for a few days, which is reaally no fun.

12

…Chipfish, i can add that better you should check a couple of times with the fin template…so you can achieve outline accuracy…

13

thanks for your tips , everyone !

if anyone else has any photos of the process , that would be great to see …

I was thinking diagrams , if not photos, of the step by step process may be helpful .

Lokbox / Jim , do YOU make and foil the “Lokbox” fins ? or , do you know if the person who does would be willing to share that here , by any chance ?

ben

I find it interesting how much info / books / videos there are on making boards , yet [to my memory ]I haven’t seen the same on fins …

Maybe it’s the one holdover ["finmaker’s top secrets / dark arts "] area of the surfboard industry ?

Or , maybe, with so many plastic moulded fins on the market , it’s a dying artform / forgotten art …except for a handful of experts …

14

Hey Ben,

I bought a Dremel “copy” for $50 at Bunnings Hardware here in Vic. It had the flexible extension shaft and a whole bunch of cheap tools included with it. It is very, very handy.

Cheers

Rohan

15

Howzit blakestah, Little off the subject, I was looking for something in my storage junk shed the other day and came across a 70’s Brewer finbox fin in great condition, pretty classic fin. Aloha,Kokua

16

…‘’‘‘Where’s the photo’’‘’ , he said …

WHERE’S the pho…

ben

17

is there a computer foiler? or are they all hand made?Im loving this thread…I remember watching BK trying to get a flat panel fin before he started to foil it…he spent over an hr finding the blank…theres my memory coming back again

18

i havent seen one but i reckon it wouldnt be to hard to set

one up (if you got a bit of engineering experience) with a small cnc overhead router and a vacuum table with locators.

i thought about it doing thick foiled glass reinforced poly carbonates cut out on a cnc

they would look pretty flash but they gotta be thick cause the polycarbonate is pretty flexible

19

I was interested in getting foiled fins for my fish - it has probox hawaii boxes with Fibre Glas Fin Co keels. I asked Robin Nair (pbox) and Larry (Fibre G F co) about how to buy foiled skegs. They said they weren’t doin them yet.

I’ve only had the board about a month, and wanna play with it a bit more, as is. But eventually i’d like to try foiled keels.

question: even tho the profiles are different, I’m thinking I could follow some of the advise above AND use the foiled Futures fins I have on my other board as as a guide. I pretty well visualize what you mean about marking the thick part of the skeg from base up with a pen, and then grinding out in proportion and fairing out.

whacha think? use the Futures (VF?) as a guide??

20

All fins are foiled…

If you’re talking about double foiled keels, well, you’re not going to be able to buy any that will work on your board regardless…cause your boxes will be pre-set with toe and even with the adjustable cant, you still won’t get it under 4 degrees.

No point in running double foiled keels with toe and cant…kinda defeats the purpose…

Your alternative would be to cut them yourself and mold tabs on that account for these inherent angles on the box such that when you mount your fin it ends up near vertical and parallel to the stringer…I’d imagine if you don’t account for the cant, they’ll still surf fine, but I’d make damn sure they were parallel with the stringer. And putting something like this together won’t be all that difficult; just make sure you get your mold set up right.

If you don’t, you’re pretty much running a double single-fin with the fins installed wrong…if you get my drift…

Good luck!