I usually make my fins in G10 and use either FCS Fusion or 4WFS boxes…
G10 is stiff, which I like, but it is also VERY heavy.
I have a sheet of 3/16" aircraft ply that I plan to make some fins with for some upcoming boards. These boards will be twinzers and the main fins will be over 5" tall. I plan to glass them with 4 oz S cloth…
I am thinking three layers of 4 oz S cloth on each side. Layer one will be laid out 45* diagonal up to the right. Layer 2 will be laid out 45* diagonal down to the right. Layer 3 will either be horizontal or vertical.
Hi Chrisp. I usually use one layer of 6 oz. Then when I glass them on they get another layer of six plus the patches, roving, etc. If i just had 4 oz laying around I would put two layers on, two more when I glass them on. Oh, I put a bit of roving around the perimeter, too. Laminate one side, cure, flip it over, lay down a bit of roving, cure, laminate the other side, cure, clean it all up. Glass them on. Mike
Thanks Rooster…
I haven’t bought the glass yet so I could use 6-ounce. These will be very solidly attached at the base to the board I am mostly worried about the fin tip being floppy. What thickness are your wooden fins usually Mike?
How I do it is…
I add several layers of glass to the “flat” side of the fin panel before templating. Then when you foil you get an FG halo that’s structural, not just glassed to the edge of the fin. With aircraft ply you don’t need to leave it thick near the edges, you can foil it pretty finely without it breaking down.
Fin damage usually occurs to the leading edge of the fin, not the flats, so if you already have an FG back and halo you really don’t need any glass to the foil side of the fin, you can just seal it with a few coats of epoxy. Which is what I’ve done a couple times with fins being used with fin systems. If you’re glassing the fin on then just extend one layer up onto the foil and blend that in.
You want to bear in mind that the more glass you add the more the stiffness/flex will resemble FG rather than wood, same as when we glass over veneers.
Thanks GDaddy, I remember reading before where you said that you might not even put glass on one side of the fin and your logic makes sense. When you do them that way do they end up too flexy? I do like my fins to be stiff…
You’ve worked with veneers before, right? Just sealing them with epoxy tends to stiffen the wood up. Aircraft play has twice as many layers relative to the thickness as regular play so it’s already stronger and stiffer (and a little heavier) just because of that. By the time I add 4-6 layers of 6oz to one side because I’m shooting for a nice halo without the razor sharp trailing edge I’m already stiffening that panel even more.
I probably wouldn’t even consider using fins made of regular ply with FCS plugs, but I think the aircraft ply is strong enough to do that without undue risk of shearing. It’s way stronger than the bamboo fins.
IMO the main reason you would add glass to the foil side of the panels you’re using is in order to seal and protect them, not because that panel needs to be stiffer. YMMV If you’re making your own fins to use with a fin system these are cheap enough that you can experiment with the build a bit without going broke.
Hi Chris - There are lots of opinions on this sort of thing. When I do wood-core side fins I usually use about a 10 layer lamination on the inside. As mentioned, when this gets foiled down, it leaves a glass halo around the edges. Once the wood is smoothly sanded and sealed with a coat or two or resin, I add about 4 (or more) layers to cap the wood. On center fins, I still use about 10 layers for a ‘spine’ but use either thinner wood, or sand to desired thickness followed by the same amount of capping glass only 4 layers on each side… This might seem like overkill but if I wanted flex, I’d just use solid glass and sand it thin. When I glass to the board I use enough glass at the base to again be accused of overkill. Once you have a fin bust off on a good wave, you’ll understand my reasoning. Many glass-on fins these days are (IMO) notoriously weak - lots of crackage along the base and fins missing entirely. Light weight vs durability. The endless battle!
Hi Chris. The same thickness as your ply, in general. I get baltic birch scraps from my buddies cabinet shop. Whatever he has in the bin. You can get a pretty good foil over a thicker fin. Mike
The part of this idea like to see a video of is the glassing of the edge. I don’t know how people hold any roving in place and how the epoxy doesn’t just drip off, or slowly slide off if already part set.
Hi jago… that’s another reason I try to incorporate that halo. It gives you something around the fin to which you can attach your caps. A wooden fin without that halo is practically disposable.
For those coming along later.
I made some fins with the 3/16 ply.
I glassed one side with 2 layers of 6oz then I cut them out and foiled them.
Then I glassed 2 layers of 6oz on the foiled side…
They are too floppy imo.
Will probably scrap these fins.
I could probably fiddle with these fins adding a layer of 6oz to each side but, the time and effort will be a lot.
Instead, I’m gonna add another layer (maybe 2) of 6oz to my flat panel and start over.
Gonna shoot for 3-4 layers of 6oz each side…
Will report back…