first time builder: futures after glassing, quad fin placement on fish


I’m a first time builder, and have been lurking on the forum for quite while, trying to soak up knowledge . Now I registered and this is my first post.

I finished shaping and laminating my first board, a 6’0 fish. I based the shape on a Fineline twin keel fish I own. The original has quite a lot of rocker, hard rails, and dual concaves, so maybe you would call it a modern fish design, despite the twin keels that make it looks more traditional? Anyway, those are just categories. The original works very well even in bigger and steeper waves.

So I built the blank from scratch (polyiso foam, PVC stringer), and laminated with Greenlight bamboo glass and RR epoxy. Two layers on deck, one on bottom. I’ve been updating my friends at, you can find lots of pictures of the project there if you’re interested. There is a link there to tons of blank production pictures as well. Don’t expect too high quality, it’s the first time I’m doing this… So far the board came out pretty well.

The remaining steps are leash plug, fins, and hotcoat. I have a set of quad Future Fin boxes that I am tempted to use. That would make the board quite different from the original I’m copying, which has these beatiful Gephardt keels. But I’d like to have something more travel friendly, and am curious how this design would work as a quad.

Here are my questions:

  • What do you think about the quad box idea, given the boards shape? Should I rather go with twin boxes? I’m hesitant putting keels in boxes for my first board, since I know those big fins create huge forces. Also I don’t own a quad, and am eager to have one.

  • I did not put the concaves of the of the original board in, wanting to keep things simple. Could I still add some concave in the hotcoat, if I make a resin dam to build up thickness?

  • I need to install the future boxes after the bottom glassing. I plan to route out by hand, and read a few post on that, but some things are not clear to me:

    • should I wrap a sheet of glass around the box when I laminate it into the cavity? Some people recommend that?

    • the football or butterfly patches that people recommend on top of the box, how big are they? Does anyone have a picture to make it more clear to me what they look like?

    • I want to ensure maximum strenght for the boxes… Some people suggest two layers of glass on top of the box. How do you then get the bottom of the board even, if you have two additional glass layers in some area? Do you just hotcoat really thick, to make it even with the rest of the board?

    • Or maybe I should just glass another layer on the whole bottom? It feels a bit weak at the moment, although I hope the hot coat will add strenhth.

    • Do you have specific suggestions (i.e. numbers) for fin placement, cant, tow-in, given my board design?

Sorry to start my first post with tons of questions. Thanks for any and all advice!

I decided on quad fin in boxes, and used placement suggestions from another thread in this forum.

So far I routed out one of the four holes, using a dremmel tool with a router attachment, and it came out ok. I’ll glue in the fins with RR epoxy, and wrap a saturated piece of cloth around the box.

So most of my questions don’t apply anymore, but two remain:

  1. I’m still not sure how to get the bottom of the board even after laminating over the fin boxes… The boxes extend through the bottom lap line, so part of each box sits in a single layer of bottom lam, while the end pointing towards the rail sits in two layers of glass. Should I just stick a football batch over the whole thing after gluing in the boxes, and then try to grind it all down as even as possible with the rest of the deck, before the hotcoat? I’m afraid either it will be terribly un-even, or I’ll have to grind a bit into the cloth. Any advice? Should I just use a really thick hot coat to even it all out?

  2. Is it feasible to create concaves in a flat lamination by doing a real thick hot coat, and sanding the concaves into that?

Horn- These problems you are having are stemming from using a pre-glass fin system post-glass (I’m sure you stated the reasons in the other thread). If you would have installed any number of fin systems you would have enough box material to grind down even with the board. That being said, I would not use footballs to glass over but a full fin section patch instead then fill with the hot coat and sand as usual.

Put one layer of 6oz or better yet 2 layers of 4oz over the boxes. Use football shapes and keep the lamination flat and tight. A normal hotcoat should be thick enough to let you fair in the patches without grinding them away. Trying to add in concaves with resin is a very bad idea. You’d just add a lot of weight and end up with an uneven (and weak) surface. Embrace the flatness, and if you still want concaves, shape 'em in on your next try.

Hi Mahana and CAHIVet,

Thank you both for the good advice.

I wish I’d put in these boxes before lamination, I’ll do that next time. I’ll probably end up combining what you wrote: I’ll put a big bamboo glass (roughly 4.5 ounce) patch across the whole tail area. That’ll make the fin area (currently only one lam layer) even with the double-laminated rails, and be the first layer on top of the boxes. Then I can add football patches on top for extra strength, and smooth out the whole thing with the hot-coat.

And I will embrace the flatness! ;D

Hi guys. The fin boxes are in. It would be great to get your advice on the last details.

I routed out the fin boxes with a dremmel tool, but went very slow, and got a snug fit. I floated in future fin boxes using plenty of RR epoxy and a piece of 4-ounce glass wrapped around each box. I ground that down after hardening, and then laminated a large bamboo glass (~ 4.5-ounce) patch across the whole tail.

  • Given what I did so far, do you think I still need a layer of football patches on top to make this sturdy enough?

  • Should I sand down and reopen the boxes before or after hotcoating? None of the many posts I searched were explicit about the order.

Can’t tell from photo, but I hope that you cut a slit in the bamboo for each box so the cloth lay flat against the box, and did not tent up over. Otherwise, when you sand most of the cloth will be ground away, leaving only resin over the box. If your cloth is flat and tight to the boxes, you should be good to go–hot-coat away! If not, then grind flat first, add football patches, then hot-coat. BTW, not a good idea to cut bamboo or any other materials in a straight line across the board, you’re only providing a stress-point for future breakage.

Yes, unfortunately the picture is too low resolution to see anything - the forum didn’t allow me to upload the full res version.

I didn’t cut slits. I was using the Greenlight “stretch” lamination technique, where the glass is stretched tight across the board. I was afraid any slits would open up too wide due to the tension in the cloth. The tension definitely seemed to encourage tenting, so I did spend a lot of time massaging out airbubbles and getting the lam tight around the boxes as the resin started to set. I think three of the boxes are pretty good, but one has a bit of the tenting. In retrospect, I probably should have made slits, or I could have placed some ziplog bags with sand over the boxes during the curing…

To play it safe, maybe I should just grind down the boxes now, and see if I end up exposing the cloth? If I don’t, then I can just retape the opening and hotcoat, and if I do grind into the cloth too much, then I do the football patches. Good strategy?

Sorry for asking about all the little details. It’s my first board, and it’s taken me so long (in between work, new baby, family etc…), that I don’t want to screw it up at the end. Thank you all for your friendly advice!

Another idea: What if I don’t grind down the “tented” box, but instead just hotcoat, and then cut open the fin slot with an exacto knife at the end? There’s be a small slope in the bottom around the fin… but would it have such a bad effect on the water flow?


PS: I posted some higher res pics at - click on the small pics there to get large versions.

you gonna baby that thing to death!?

feather in that thing that looks like a butterfly …hot coat it and sand er down

when you sand the hot coat the finbox hi spots will come down to the top of the hot coat

there will be glass covering the boxs when your done

the more you “F” with it the more you will “F” it up

Hi Ken,

I’d love to just hotcoat and be done with it!

I’m being overly cautious as it’s my first boards, and I’ve invested a lot of time in it, which included building the blank first. The shape has come out much much better than I ever dreamed of, so I don’t want to screw it all up at the end now: My nightmare is that the fin boxes will rip out of the board on the first wave.

Since it’s the first board I don’t have any prior experience to tell me if the existing glass is strong enough to support the fins boxes. Sounds like you say the single glass layers w/ epoxy under and over the boxes should be enough? In some threads people recommended a total of 12 onces on top of future boxes, which has me worried. Is 12 ounces overly conservative? I want the board to last.



you could add some football patches 4 or 6oz

but the bamboo fabric is suposedly a bit stronger then fiberglass (I think)

if youve encapsulated the boxes in glass your allready stronger than normal