Kaholo 14 fin box reenforcement photos

After deciding to go with a single fin and fin box design for my Kaholo 14 build, (giving me and the board greater versatility) I created a reenforcement sandwich that would also serve as a leash plug foundation. Using balsa sheets from a craft store and some of the extra ply that came with the kit I designed the sandwich. Solid and incredibly light. While other designs for a fin box reenforcement only attach to the hull bottom I opted to make it as rigid as possible by running it to the deck. 


Created balsa/ply sandwich that will butt against #11 bulkhead and tailblock, hull botttom and underside of deck...

Balsa/ply sheets glued together...

..while positioned in hull, but NOT to the hull at this point. Note wax paper separating sandwich and hull as sandwich is glied together.

Sandwich glued into place and then sealed with coat of epoxy. I also glued another small piece of ply at the stern end of the balsa sheets to complete the framing. 

Measurements taken off a centerline string running from bow to stern. fin box traced and ply and balsa cut cout using blade

Fin and centerline string used to assure proper alignment. 

Created a "weighted box frame" to secure fin box into epoxy and glass as it set up. Flash Gordon would have been pleased...

Once set, ground fin box down flush with hull bottom. 

5 replies:

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RE: Kaholo 14 fin box reenforcement photos

I'm working on the same thing. So you did this before glassing the hull? 

RE: Kaholo 14 fin box reenforcement photos


Sorry I haven't responded sooner. I hadn't checked the foum recently until now. In answer to your question, I did all the fabrication before glassing the board. I inserted a piece of balsa into the slot of the box and then covered the exposed balsa and a few mm of the Bahne box with tape. I was careful on the glassing to come right up to the edge of the tape so as not to have much to cut away.

The end result gave me a flush hull bottom and a fin box completely fixed in place under the glass and subsequent varrnish. Smooth and clean.

It's certainly possible to put the box in after the glassing but this is the way I went and it came out beautifully.

Happy to offer any more info. Drop me a note at danjbright@gmail.com for a more prompt reply.



RE: Kaholo 14 fin box reenforcement photos

I'll add my $0.02 here in case you haven't finished this step. With help and inspiration from Dan Bright (thanks, Dan) I installed a fin box in almost the exact same way. I haven't tried adding permanent fins as described in the manual, but ultimately I think think the fin box is a simpler route. My only deviations from the above described method:

  • I used a laminated block of cedar instead of balsa. Probably added a few ounces, but I had it on hand and it worked well.
  • After fretting over how best to cut out the recess for the fin box, I wised up and parted with $10 to buy a cheap 1/4" pattern cutting router bit (the type with the guide bearing at the top of the bit, not the bottom). With a plywood template, cutting a perfect recess took all of 2 minutes. If you have a router, get one!
  • I didn't add fiberglass to the recess, and frankly, I didn't research this choice. Given the neatness of the cavity I had very little "slop" to fill and decided the added glass would only complicate matters. The Bahne box has a groove along its entire perimeter to key into the epoxy. I'm counting on this to offer adequate "mechanical restraint." I simply painted a coating of thickened epoxy to the box and then coated the inside of the cavity. With the box weighted down there was plenty of spillout. I wiped away as much as I could and the rest was removed when the box lip was ground flush to the board.
  • I covered the hole in the fin box with masking tape and glassed over the entire assembly as if it wasn't there. After the epoxy began to kick, I used a razor to cut through the glass at the perimeter of the tape and simply pealed it away. You may want to cover the hole again to avoid drips into the cavity when adding fill coats, but I found this wasn't difficult to work around.

Good luck!


RE: Kaholo 14 fin box reenforcement photos

Here is my $.02 as well.  I completely plagiarized Dan's skeg box set up but my reasoning was for a flush mounted leash holder.  I went with the stock fins but now I have the option of removing them and placing a skeg box when (and if I ever do) refinish the board.  I copied Dan's pictures to the letter almost.  I made a laminate out of balsawood strips before mounting into the hull.  When I plained the hull to accept the deck, the skeg box was plained accordingly.  The whole box was glued in with thickened epoxy and fileted.


In hindsight after installing the stock fins?  I wish I had just gone with the built in skeg box.  Cleaner and simplere plus the fins are removable.


I'll post up photos soon.  I'm at the varnishing stage now.

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