I’m going to try my hand at making a 9"ish glass-on fin for 9’6" and it seems the archives focus on marine grade plywood and/or baltic birch plywood. Is there a drawback to using a solid wood? Also are there any suggestions for wood thickness to start off with - 1/2 or 3/4?
Thanks,
HerbB
you can use any kind of plywood, check the archives and you’ll find a post with step-by-step pictures and instructions on how to build plywood core fins. i’ve used pine and a combination of cedar-pine in two 7’’ fins, and pine plywood in my fish’s keels. everything glassed with choped strand mat and poly resin. also check www.hollowsurfboards.com there’s a section on how to make wood fins. for a thickness, i would recomend something below the final thickness you wish your fin to be, so when you glass it, it won’t go too thick. Jack.
i made twin keels out of a solid piece of pine and they came out great so i would say just use whatever you have
Solid wood is a bit more difficult, too,because you don’t have the layering to help get an even foil on both sides. Mike
I’ve always used a 10 ply fiberglass panel either sandwiched between wood (on a single or trailer) or laid up on one side (for side fins)
John,
Is the 10 ply used to create a aesthetic bead, strength, or for less flex? Also for your singles, what thickness wood are you using per side of the sandwiched glass?
Thanks,
Herb
You can go with most any wood. If you’re after more of a traditional look, go with redwood and glue up a few basswood stringers. Make it about 1/2" thick though I prefer a thicker fin (up to 3/4"). Tom Wegener has some things to say about thickness www.tomwegenersurfboards.com ). Mark a center line all around the finished shape for reference and foil it out. Have your glasser put a bead around the peremiter, glass it on, and you’ve got a show-stopper to be proud of.
Richard
Richard,
First, thank you for that really great tip on the center line mark as a reference when foiling. My plan was to more or less wing foiling and that will really help keep it symmetric.
Wegener’s comments are very interesting. Before reading them, I was leaning towards a thinner fin but now would like to try something around the suggested 3/4" thickness. Also the board I will be making this fin for has very soft rails so his comments on placement (further back) also has me thinking about my original intent of placement.
By the way, you have have a great webpage - very well laid out and enjoyable to read.
Best,
Herb Bean
BerbB,
Just came in from the shop for lunch and checked messages. Glad to hear the Wegener site helped you out. When marking that center line around the outside edge of the finished fin shape you can use a marking gauge or compass, but I prefer to simply hold a thin point felt-tip marking pen and use my 3rd finger as an edge guide and pull the pen around all sides. Sounds like it would not be accurate, but actually works very perfectly and quickly. Figure out a clamping situation to hold your skeg while foiling. I prefer to have it about the same hieght as a surfboard when shaping (a little above bellybutton high or so). I use a 4 1/2" angle grinder with a 36grit wheel and pass from one end to the other exactly like doing rail bands on the surfboard. I do the back side, spin it around, re-clamp, then do the front side, then flip it over and same. Super light touch with the grinder with no “oops”. I’ve seen guys just grind away randomly back and forth when using an angle grinder, but even straight and methodical sweeps will give you really clean results with no dish-outs and bumps. I use the grinder to go all the way to finished shape then follow with sanding to only about 180 grit. If you go to 220 or beyond I find the resin doesn’t like to stick as well. (60,100,180 are really the only grits I need on softwoods for doing this job). Be sure to seal coat the wood with resin before glassing (sometimes even a couple brushed on coats. I’ve got a few skegs in my website in case you’re interested for reference or design ideas. Enjoy the ride!
PS: I’ve been off Swaylocks for about a month and it’s good to be back.
Is the 10 ply used to create a aesthetic bead, strength, or for less flex? - Primarily for impact resistance and to provide a glass bead to which the outer layers of cloth can bond. Edges on solid wood (especially the leading edge) are subject to dings leading to water absorption and eventual delamination. That 10 ply center panel can take a pretty good shot and still not leak.
Also for your singles, what thickness wood are you using per side of the sandwiched
glass? - It varies with foil thickness. You can also laminate foam strips to increase the foil thickness without adding much weight.
I use Ply wood, However any wood could work. The Glassing makes the biggest difference.
Josh,
Depends on what you’re after…
Say you’re making a high aspect ratio single fin and want it to exhibit some flex characteristics. Plywood will work better in that case (solid wood fins tend to be stiffer).
I’ve made some extremely flexy yet strong fins with a birch plywood sandwich around a polycarbonate core. Also, epoxy works much better for flex fins than polyester dues to its far, far superior qualities in terms of flex.
On the other hand, marine grade plywood was originally used for Fish fins mainly due to its strength (the fact that it is easier to foil with its multiple layers was a bonus).
Also check out Paul Jensen’s site. He makes very nice fins and a “how to” on his site.
Rich
I wish I’d read this a week ago, the tip on glasspaper grade would probably explain the problems I’m experiencing with the fins I’ve just made for my 7’4" Hollow. The resin is indeed reluctant to stick, particularly around the edges. Real shame cos I think they look fantastic apart from that, obviously haven’t finished em yet. Think I’ll try to salvage rather than start again, any suggestions?
Jase (MMM)
I have only made 1 fin. It was with 3/4in.cherrywood riped in half. I made it to fit a fin box. It works great and looks even better.
Fat,
On the edges where it didn’t “stick”, you might want to sand back through the glass just to the bare wood, then brush coat the wood with resin to seal it (two coats may not be overkill and cheap insurance), then re-glass. I’ve read posts where guys have suggested sanding balsa to 320 or even more, but my limited experience says 150 gt. or so is all you need for beauty and “stick” with the resin. Believe I remember a recent post where J. Phillips stated that Dale Velzy used to bring in balsa boards sanded to 36. Don’t know if that means Dale knew about the “stick” issue or if he was too lazy to sand. I’m going to assume that since he was likely doing poly resin glassing he wanted his wood a tad rough. If Phillips reads this he can give you his expert opinion, but that’s my take for what it’s worth.
Richard,
I just cut out my template and tomorrow I’m going to foil my fin. Thinking ahead, I of course would like the wood’s grain to show as much as possible - is there any preparation that would help highlight the grain prior to sealing it with epoxy? Everything that I can think would most likely cause delam.
Thanks,
Herb Bean
Herb,
I don’t use epoxy but know others do. No prep on the wood. The wood grain will “pop” beautifully without any prep work. I just seal coat with resin and after glass and polish it will be nice and clear showing the grain.
Cheers Rich,
good to know as that’s pretty much what I’ve done. I still need to do a bit of work on them but looking the dog’s now.
Thanks again
Jase (MMM)
