My main hobby is knifemaking. To that end I have a fair stack of offcuts of pretty looking wood that I plan to use for fins by sticking them back together in some odd arrangements.
Aside from that, I also have made my own micarta handles for some knives and wondered about that process for fins. For those who don’t know, micarta is essentially cloth (cotton, canvas, linen, etc) that is layered up with resin to form a solid and tough material. It’s much the same as G10, which I know is used for fins, and that also gets used for knifehandles but the cloth is fiberglass.
So I’m wondering if anyone sees any reason not to lay up my own panels of micarta using scrap cloth and polyester resin, as I’ve done before for knives, to then shape some fins out of. I would suspect that after cutting and shaping it would need more sealing (or a fiberglass layer) but not sure if there is any other reason not to play at it.
I do not see any reason why it would not work as long as the cloth in the micarta is not wicking water. The only downside I can see is weight.
Respects to you for being a tool maker.
Sway’s does not need (gets confused by) the URL tags before and after the links, just paste the address and you will be fine. I fixed it above so the links should work now.
Stew, I started using Micarta, for surfboard fins, in 1964. Both canvas, and linen versions. Linen was preferred. I was first exposed to the material, in 1959, when I worked in the plastics dept. @ Convair General Dynamics.
thanks Stewart, the pics you linked to look really cool, looking forward to seeing some of your fins. Its always appreciated when you can post up a “build thread” featuring the process, step by step, as you have done on your blog. You can use the same content as the blog, just copy and paste onto swaylocks - but that way we can see everything without having to link over to another site. And a link to your blog or website can be kept in your signature, so that anyone wanting to see more can click over.
I had done a fair bit of searching on Micarta surfboard fin and no hits. I was surprised that nothing pinged up as the similarity to G10 seemed it an obvious choice to have been tried and is presumably an earlier material too.
I have a pair of bright white linen trousers that have been saved from the charity shop bag - either knife scales or fins!
Moisture content (humidity) will affect strength – heat/dry before use.
EDIT:
Of these plant fibers, linen/flax has the best tensile strength. Tensile strength also dependent on type of fiber, bundle vs. single filament.
Stoney, laminated fiberglass cloth aka G10 or FR4 comes in around 1.8 gm/cm^3 and is not as susceptible to humidity/water absorption as some of the more ‘natural’ counterparts.
Jim,
As you know, G10 is a composite mixture of glass fiber (2.55 g/cm³) and epoxy (1.1 g/cm³). I would expect this mixture to be less than 2.55 g/cm³.
I would also expect the desired linen/flax fiber (1.4 g/cm³) and epoxy (1.1 g/cm³) mixture will be less than 1.8 g/cm³.
I agree that Stew should move forward with his linen/epoxy fins. Seems like linen/epoxy should be easier to shape/foil than glass/epoxy. I suspect the right epoxy/linen mixture would make a solid fin. Add a fiberglass skin, even stronger.
I have been experimenting with desk blotter paper as a potential core for fins.
Seems like it should be easy enough to dry organic fiber with a “quick” stay in the microwave or oven (at the correct temp).
Bill
Bill, at the end of the day, I would expect any homemade panel laminate to be slightly resin-rich than industrial versions and I would also expect a natural fiber lam to consume more resin as part of the natural fiber’s ability to absorb liquids. This goes back to watching cotton fabric inlays consume more resin per ounce of cloth than fiberglass on surfboards.
The blotter paper core is interesting, sort of like a chopped strand mat. I made a rectangle-to-round vacuum chute for my Skill 100 using laser-cut blotter paper and 2oz glass cloth and epoxy resin.
I found Table 1 at this link useful for natural fiber comparisons. http://www.fao.org/docrep/004/Y1873E/y1873e0a.htm
I would expect fibers that absorb more resin to create thicker layers – i.e. fewer layers.
Approximately 16 layers of blotter paper will create 3/8 in thickness. Strategic placement of a “few” layers FG cloth for better strength would add a tad more thickness.
Vacuum forming would help to get lower resin : natural fiber ratios.
(While not necessarily ideal for strength, I higher percentage of epoxy, at 1.1 g/cm³, would lower panel density overall.)
Like Stew, use what you already have in the barn.
At some point you get into the flex and rebound elements. Even a G-10 fin will have some flex and recovery and a repeatable resilience if you foil it that way, and I attribute those properties to the strands in the weave distributing that stress more evenly and (after a fashion) predictably. I’m not so sure that’s the case with non-directional materials. After all, we glass surfboards with weave, not mat. We bulk laminations up with non-directional or foams in order to add stiffness, not resiliency. Even when they’re using mat or foam for a fin core they’re glassing the outside with weave and relying on that shell for their flex properties.
I would think that hemp + epoxy would make a helluva fin panel. I was thinking about doing some, but then decided its a lot easier to just buy a 1/4" 12x12 panel of G-10 for $25 or the black FR4 for $36 (eplastics.com) at which point you’re foiling shortboard fins out of industrial grade G10 for $6.50 - $9.00 /each. Or for the hipster boards I can do an aircraft ply fin with fiberglass back but weighs 20% less for about the same price.
I make fins using G10, but I’ve also made a couple using black Micarta for knife scales.
G10 makes beautiful fins, but they are heavier than wood or foam composite fins. It is very strong material.
For certain kinds of fins, G10 is the best material to use. I don’t think G10 is good for large fins, like center fins because they end up heavy.
Thickness to vary stiffness/flex.
Fiberglass skins for the benefits of composite sandwich construction. Other potential FG cloth use options as well.
To reduce composite mix density further, perhaps a wood flour/fine sawdust and epoxy core with FG cloth skins. (Wood flour has been used for plastics manufacture.)
Like Stew, use what you already have in the barn…
I’ve used G-10 in the construction of a couple of longboard fins, but as part of a sandwich, using a 1/8" panel of G-10 as the “spine” and adding ply on each side to fill out the thickness. When foiled, the spine provides the strong halo for leading and trailing edges, and ensures the fin will basically never snap. The result still comes out weighing less than a 100% fiberglass fin, but I wouldn’t try to do one for a flex fin.
Someday I’m going to do a g10+ply fin with the really fat base (like 1") and more complete base-to-tip foil. I need to get better at foiling first, though.
You could build a centerfin panel with a wet layup, too, similar to how they do the homemade micarta; by doing a wet layup of fiberglass on the inside of one panel (like 8-10 layers) and putting the inside face of the other ply panel on top, then clamping everything in a press while it sets up and cures. Except I don’t own a press.
A hemp + ply composite panel would be a real hipster fin.
I should clarify that I’ve made fins from wood, foam and fiberglass panels I made myself. Several years ago I bought sheets of G10 for fins because I thought it was more cost effective than making panels. I’ve done a handful with a wood veneer or fabric center piece as well. I don’t the mess, so I don’t make fins often. I do it to get fins you wouldn’t find in a surf shop.
The yellow and blue fins have single side foils for the twingle boards I have. The blue fins have a XPS foam core, the yellow fins are solid fiberglass, and the greenish fins are G10.
