Installing 10.5" Bahne Box on Vee Bottom

Starting to shape my second surfboard soon, a 6’ 5-fin modular type board that I can use any fin setup with. I’ve had experience installing FCS Fusion boxes on my first board and found the process relatively simple. I want to install a 10.5" Bahne box as a center-fin option for this next board to have the option to ride it as a single or 2+1. I plan on shaping a single concave into a slight vee at the tail with a flat spot between the two and am anticipating some difficulties installing the bahne box on the vee as the bottom wont be flat for the jig to rest on. Has anyone made a solution to this or have any ideas on how to shape the vee so it’s easier to install the box? I was thinking of either leaving a flat spot at the center of the vee so I can easily route out the hole and not have to worry about grinding down the box to match the vee. I’m also thinking of just wedging cardboard underneath the jig when I install the box to keep the jig level. Any input would be appreciated!

Buy some door shims. stack and slide. Tape them in place to keep jig level when router vibratrions want to make them move.

  Make sure board is level too.

 

Cardboard compresses. No good.

 

 

Yes wood shims will work, but you’ll have better luck with the foam shims like you get with a Futures “One Pass” set up.  Line the jig up on center and then shim the sides…  You can check for level with a torpedo level ascross the jig.  Does not sound like any problem to me.  You’re not talking Extreme V.  It is possible to set the box a hair shallow and then grind at the hotcoat in such a way that the box blends to your V.

Something to remember about what I just suggested;  Yes you can set the box shallow leaving the box sitting higher than usual and then grind it off to match or come closer to your V at the tail.  Just remember that we are talking about a very small distance.  Perhaps 1/8 or 1/4" max.  By doing this you will also possibly exspose more of the base of the fin.   Everything can be compensated forwith some fine tuning.  Bruce Fowler does a lot of the old style deep V’s.  His look good.  I see no problem.

After you get your jig all set up tape it to the board to prevent movement

…Dead shaper s boards are laminating by others so would look ok due to the glasser not due to the shape.

In his boards or similar the thickness there is good so actually you do not need to cut too much of the thickness of the box so no problem exposing the base of the fin.

Should I install the box before or after hotcoat, or just install after hotcoat and cap w 4oz+glass over. I normally install fcs plugs before hotcoat on color lam, not sure if this is different. 

Install after the hotcoat is the norm.  If you feel that you need to cap it, you can do that by sanding the area at the fin, cap the box and then hotcoat that.  Then sand the entire board. Or;  Sand the hole board and then, cap, hotcoat and sand the area at the box.  Either way will work.  Any time you are concerned that your saturated cloth might not stick;  You can take the added precaution of applying a coat of lam resin to the area your are working on and let it go off.  Then laminate your cloth.

If I install after hotcoat do I even need to cap it? it’s not like an fcs box where only the tabs need to be exposed. 

If you do a good job on the install with no voids or pinhole around the box;  No, you do not need to cap it.

In my BFV8 - which is a deep vee bottom design, an homage to the old V Bottoms of yesteryear I am primarily using the Bahne aka Fins Unlimited 15" long fin box. On the shorter V8’s under 7 ft. I’ll do the 10.5" Bahne box unless the customer wants the extra long box.  The 15" flex more, so we are very careful when installing them that we don’t have shrinkage or separation of the sidewalls from the resin and glass we install it with. 

As far as glassing, we use an additional layer of glass in the tail section (tail patch pf 4 or 6 oz) when we do the bottom lamination. Then hotcoat the board before doing the routing and fin box installation.  The boxes come with 4  “alignment tabs” at the corners of the box which was designed so that you could rout the box cavity deep enough for the tabs to sit flush to the board’s bottom.  The idea was, with a properly shimmed router jig, you should be able to rout for the box then the box will self align using the tabs for the fin to sit upright without being cocked to one side.  We don’t trust that feature and use a dummmy fin when installing the boxes so we can eye ball the installation for correct alignement to the bottom. 

Using this method, with my deep vees, there isn’t an extreme amount of box to grind off.  We don’t add glass over the box because we are experienced at installing the boxes carefully avoiding bubbles or void during installation.  Any voids would require a secondary fill.  On sailboards in the 80’s I regulalrly capped the fin boxes by sanding them rough then capping with two layers of 4 oz. over the open cavity,( which we could do carefully with the viscosity the polyester resin had at that time) - no tape, just squeegeed over then hotcoat, sanded, routed the channel open and rounded the edges so there was no lip for a tight fin to lift the glass up off the box.  

If you leave the box up high, you are asking for problems with too much fin base sitting up. It also is weaker being set in shallower, and sometimes the bind & pin action doesn’t work in extreme cases.  Some guys wash their boxes with acetone before installing, I’ve always given them a rough sanding for a bit more mechanical bonding.

 

 



https://swaylocks7stage.s3.us-east-2.amazonaws.com/s3fs-public/Hotcoated%20V8%204+1.jpg



…you said what I mentioned, but without the power of synthesis

“Mention” -  refer to something briefly w/o going into detail.

Sways is kind of the antithesis of that.

P.S.  How do you know what I glass & what I don’t… do you have hiddern cameras @ my house?  lol.

spy robots; no; because long time ago, in a thread somehow I was talking about board builders etc and you uploaded photos of the boards that you did the shape and glass. Then you put more photos from the glassing shop that is doing your work. Then; few years ago; I was in the Saturday s shop in Tokyo, and see one of your shapes with the glass shop logo.

BUT; actually I put those words to bring you again to the forum.