I am building a wooden hollow board from plans and need some help; is it easier to install a fin box or glass on a fin? I am an experienced woodworker but have not built or glassed boards before. The plans don’t show how to do either one.
Thanks
I say glass on. Learn the basic skills first.
My personal favorite for making fins, Berts fin primer. There are more in the archives.
My suspicion is that it would be easier to get a good final result with a fin box. Try the Fins Unlimited box. They make several sizes, and they work well in an all wood installation.
Thank you Pompano for putting up Bert’s fin primer, and thank you Bert! I’m a begginer, just did some glass ons, went fine, stuck the fins in place with a little super glue, dug yarns out of some heavy cloth to make the rope to lay up alongside the fins. I’d do the same again.
I’m with Bill.
Fin boxes will be easier for a beginner who has woodworker skills. Glass-ons are a messy, time-consuming, labor-intensive bit of work, and to get 'em looking just so, is usually a lot of sanding. Granted if you’ve done a few the work is minimized, we can all learn from experience. But for a first timer? Box it. Case closed.
Unless you know exactly what fin will work best with your board a fin box is nice to have.
Just make shore you put some blocking into your frame to suport it. I have used foam or
wood, both work, foam is lighter.
In my honest opinion, you should foil your own fins, and glass them on. This is what I did on my first board, and although with much anxiety at first, I found it is not as hard as I would have thought. Glassing them on is no worries at all. If you decide to go this way, I got some info I could pass on to you, to help you out. Just PM me if you’d like.
Peace,
Tyson
Were you not an experienced woodworker building a wooden hollow, I’d say glass-on. But… given that, a Fins Unlimited box is the way to go, like Bill said.
Have a look at the photo dontask posted, you’ll see the big block of foam ( and wood will work fine too) inset at the tail. Call it at least 3/4" oversize in every direction. Note that he’s got a cross-member or two off of it and it ties into the perimeter at the tail too. It’s maybe the one point where it’s stress that needs to be tied into the whole structure. Fit something like that, close enough that it’s a glue-fit, put the skins on ( again, glue well) and then you can set up a jig for a plunge router with a collar to go through skin and into the block. I might hold off on doing that router thang until you’ve given it some glass.
Secure your jig Real Well. There was a time or two I didn’t on some refurbishing/repair projects ( being the multi-year poster child for Blithering Idiot that I am) and I am here to tell ya that when a plunge router and a straight bit get loose, it ain’t pretty. Hot glue, AND clamps, AND anything else you can dream up, that’s about enough. Don’t even think about freehanding it - been there, done that, added the vast globs of filler to the botched job, and that wasn’t pretty either.
Let it stand proud of the glass at least 1/16" - the fin box will come with some ears on it so that it’ll set flat on top of the glass. I might leave 1/16" all around, so that you will have room to bed it in some cloth and resin, to tie it all together with the skin…a little bit extra strength never hurts…
Set your box ( and a couple layers masking tape over the slot in the box, in case a little resin goes astray ) with the cloth and resin, let it go off and then grind the box down to flush with the skin or just the faintest skosh proud, tape the slot again again and apply your gloss/hotcoat and so forth. And there ya go.
Hope that’s of some use
doc…
The fin box sounds easy enough to install with a router and some guide rails/templates, however I’m not sure I have enough structure to add the box. I cut a notch a few inches long in the top on the spar near the tail to install a light wood block for the vent plug (threaded insert installed into the block), and this reduced the thickness of the spar to about 3/4 inches thick. Even if I glue another block into the structure, I’m concerned that the spar section will be too weak when I rout into it from the bottom to install the box. Thoughts?
Uhmm, yeah, I see where you’re going with this. Catch me when I go off course, but let’s say you have something like this, currently?
Details of perimeter structure, etc, not shown because frankly, I’m lazy. I am also assuming that you don’t have the skin on either side yet.
Okay, this will involve a little surgery with something like a dovetail saw or one of those Japanese saws everybody but me seems to be using these days:
Remove your centerline spar from one cross-member to the tail, pick one that’s appropriate. I’d probably put a couple of temporary cross pieces in there so you don’t lose your curve where you’re removing that center piece. Scribe and fit a wood block as shown up above.
That doesn’t sound like a whole lot of fun, does it. And the chances of ruining all your work so far are pretty good. So, plan B. Especially if you have one of the skins in place.
Sister some blocks of wood alongside your current centerline spar, glue them Real Well with Very Good Glue. You may have to remove the vent block you put in and make a dutchman or something to fill in that spot, so you don’t have a notch or something, but you’ll have plenty of meat there to put it in someplace else, maybe forward of or behind the box? The drawback to this is that the glue will prolly be harder than the wood and it can lead your router bit astray if you’re not careful.
Leaves the original structure intact, though, and you won’t have to worry much about losing your fair curves back there. As you’ll have seams running along there, plus a few other potential problem spots, bedding the fin box in cloth and resin will be kinda imperative, I think.
Anyhow, that’s a couple of ideas, hope they’re of some use
doc…