Somewhere along the way on this site someone posted a method using two pieces of glass instead of one to compress the cloth and resin to create a panel that was precisely the desired thickness. The person used nuts or washers between the two panes of glass to establesh the thickness. Never tried it that way but always thought it seemed like a good way to get the thickness right.
If I recall correctly, I've seen resin infusion techniques like that
Not to hijack the thread, but I have a question on panels. Actually its not so much a question, but an idea I couldn't find any info in the archives. Hopefully some of the more experienced members have experience they can share.
If one wanted to build a thick fin panel (3/4" +), but didn't want to use a ton of cloth. I'm not a production shop so my scrap glass pile is limited. What would be the best way to go about this, without the obvious wood core. My thought is to use glass mat, the stuff used in boat building and autobody repair, to build up a thick panel. Roughly shape it. Glass with 4-10 layers of cloth on each side to the final thickness, sand it, and ride it. Other thoughts also include making a thick panel using resin and qcell or some other addative to add volume. The major downside to mat is the resin to glass ratio isn't great, but might be lighter than G10.
I know someone (Mr. Mik if I remember) was messing around with molded fins and styrofoam core. This isn't exactly what I'm after, but hopefully he can chime in on his experience anyways.
I am not an expert with mat, but I am pretty sure that "Chopped Strand" mat would be cosmetically visible. The type of mat that we commonly use to to pull strands off for fin rope would be a possible choice as a mid-section. More cosmetic.
That which can be assorted without evidence was read in an illegal magazine.
While the resin of choice was not mentioned,
Fiberglass matt and epoxy are not happy together, the binders holding the dry matt together, are not dissolved by epoxy.
I have a bunch of Woven roving. Last several fins i made, I did not have a bunch of good cloth to layer, but I did have 24 oz woven roving. I think I used 3 or 4 layers and 3/16" of cedar laminated onto waxed glass, to come up with ~ 3/8"+ thick rail fins.
Epoxy does not seem to wet out woven roving completely, even with a bubble roller and warmed, slow epoxy and lots of pressure, and time to soak in.
3 or 4 layers of 24oz woven roving gets about 1/8" thick and it is amazingly stiff, even when it does not appear to wet out completely by epoxy resin.
I believe the woven roving has the same , but a lesser amount of, binders, that hold fiberglass matt together before saturation.
I suspect Woven Roving works much better with Polyester resin.
Its my opinion One can make a fin panel with horribly layered, warbly, multidirectional cloth off cuts going every which direction, and achieve a good fin. Far stronger and stiffer than needed
I think a great fin requires precision and finesse of that layering.
Perpindicular layers all pulled tightly
A bahnebox, all fiberglass fin, at 3/8" thick, might not be thick enough, but it is certainly heavy, and strong.
A thick, well foiled fin, pushed through a hard turn, is enlightening.
A 3/8" thick fin with a flat spot on both sides, is not.
Even if my brain were not addled with wood dust, I think wood, in a fin, saves fiberglass and resin and weight, and can have a more desirable flex pattern, but laminating foiled wood stiffens it up to a ridiculous degree, and then there is the halo to worry about.
Much easier and faster to foil wood, than fiberglass.
but a perfectly laidup solid fiberglass cloth fin panel makes achieving an accurate foil much easier.
An imperfect fiberglass layup can instill a thousand curses, when trying to foil by the layered pattern
Wood grain can also trick ones eyes/brain into frustration and imperfection though, making sharp, adjustable sidelighting, imperative, in trying to achieve the desired foil.
Theres a million different ways to make a fin.
I dont think I've used the same method twice, and I would have a long ways to go before coming close to achieving, what I would consider ideal.
"I think a great fin requires precision and finesse of that layering". When it comes to fins, this is probably the most correct statement I have heard. You are right about chopped mat not saturating completely and probably the reason for its poor cosmetics. Some people like the look though. Lowel
Sorry WRC I should have mentioned that I typically use polyester resin so any binders in the glass mat or woven mat wouldn't be an issue for wetting it out. With regards to shaping being easier with nicely layered glass cloth you are right, but my "shaping" is done with a small cnc router. It give pretty good foils as long as the operator is paying attention. I do like making wood core fins, but you hit the mark with all the down sides. I have at least 6 toolpaths that I run for a wooden fin to get a decent result. I'm hoping some of your tips will help me make a thicker panel that would only need 2 toolpaths on the cnc. I think I will try and find some of the woven mat to use before trying chopped strand. Although chopped strand might give a crazy look with some colors mixed in.
Nice work. I rarely foil, but know a nice fin when I see one. Unique and beautiful.
Agreed, nice looking fins.
I've lost interest in making and testing fins, as I've also lost my surfstoke with the extra entitled adult learner wavestorm/softtop covid shitshow.
I need to get over it, and get back into it, for my mental health.
I've got 3 fins cut out, and ready to foil, somewhere.
They've been ready for 15+ months.
How did you make the base for that pivot fin? Do you have a mold?