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Sunday, September 13, 2009

Convert from Glas-on Keels to a Quad with Keel Twin options

This Jeff Bushman Twin was sent to me from Hawaii to convert to Proboxes. The rider of this board do not want to change the postions of Jeff's Keels but wanted to expand the use of the board to a Quad option. This thread will take you through the process of the change.
First thing I did was remove the Glas-on Fins and mark how far in Jeff had his fins from the rail, as show in the pic below. The back marking should read 1-1/2" not 1-1/4", oops!
I then prepared the tail section of the board with a tail patch. I prefer 6oz or 7-1/2 oz glass for this stage, because your bottom lamination is the most important part of supporting a Fin System from failing.
After the lamination is completed, trim and hotcoat the tail patch for installs.
Now place your boxes for a visual and make your markings on the Hotcoat. This board the tailing edge of the Keel Fins were 7-1/4" from the tail, which put the back of the ProBox 8" from the tail. These measurements put the same Keel Fin template with a ProBox base back to Jeff's orginal placements, 1-1/2" off the rail with 2-3/8" toe to flat inside of the front of the box.
Now that we have set the first set of ProBoxes, this will dictate where the next set of boxes are placed. My choice from all the conversions I have done were to add the next set of boxes to the front of the existing set. What people forget here is, that we have a adjustable Fin System so if the ProBoxes seem alittle far forward we adjust the fins back in the box. If more adjustment is needed then we can custom make the Fin Tab of the ProBox fin to be further forward allowing more adjustment further back. Most Older Fixed Fin Systems won't allow this to be possible, which then the board builder will have to compromise this position and hope the board works. Having the boxes to far back and shifting the Fin Tab on the fin base back which allows you to push the leading edge of the fin further forward will work against you. This causes the leading edge of the fin to flex in creating drag.
Once I find where my front set of ProBoxes are placed, I will set my toe. In this case the toe of the front boxes will be dictated by Jeff's original toe set by his keels from the rear boxes. To find the toe of the front set of boxes, mark in from the rail to the flat of the inside of the box at it's rear. In this case 1-1/2" off the rail to the flat and 3/4" forward of the rear boxes. Then toe in the front box until your flat side is running parallel to the flat side of the rear set of boxes.

After all your markings are done, lay down heat treated tape. I use 1-1/2" tape. This will act as a guide in sanding and creates a good bond with our install jigs with the spray glue. DO NOT over lap the tape!! This tape build up will throw your box install off in depth. Lay the tape side to side.
After your jigs are set and the hole is routered. Spike a few shallow holes around the inside of your routed hole half way up. This helps create a fiberglass flange concept when you resin or epoxy is poured.
Cut your glass with a template for ease of cutting multiple layers of glass at a time.

Center your glass over the hole and push 2 layers in like the pic below. Then press the glass outward inside and you are ready to pour.Now do your install of ProBoxes per our instructions on our website
Make sure to prep boxes properly before installing.

When your install is done and jigs are pulled then you can deflash your boxes with this deflashing jig by Greenlight at
Now enjoy your new Quad Keel combo with no compromising (-:
Top pic is this Bushman with Glas-ons. Bottom Pic is after with ProBoxes in same placement as Jeff started with Glas-ons.
Now from Twin to Quad mode.
Here's the happy owner of this Bushman Board.