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