Here’s a build thread for a channel bottom timber veneer board. Rails are balsa ( 3 x 6mm strips), core is Styrofoam and deck will (?) be Corecell. I’ve included some hotwiring techniques as well.
First step involves hotwire cutting of the blank. I use a 3 stage hotwire process to first cut the deck roll, then the profile thickness (foil) and finally the outline.
Deck Roll
Deck roll is cut using a nichrome wire slightly longer than blank length. I connect power wires from my Variac transformer to each end of the Nichrome. Identical deck roll templates are placed at the nose and tail end of the blank (templates shown have a constant radius of 1800mm). If there are 2 people to do the cutting they can have an end each. If you are doing it by yourself then the 2nd end is connected by string to the shed wall, slightly lower than the template edge. I have small up-stands on each template to suspend the Nichrome wire when powering up the Variac. When powered up tension the Nichrome, bring the wire down from above at blank centreline and cut outwards to the blank edge. Do this to both sides of the blank.
Tape the deck roll offcuts back onto the blank and flip it over. Place foil/thickness templates either side of the blank and hotwire along length of blank use hotwire bow.
I’ve made a neat little hotwire unit that works like a router with a follower collet/sleeve. This allows me to follow an outline template to cut the blank outline.
I’m using balsa rails for this board, 3 x 6mm. I’ve always had problems getting the balsa to bend in both outline and rocker combined so I evenly slice the ends of each rail piece to help bend/laminte in the rocker during vac-bagging. Ive made a small tool to evenly split each rail strip. Stanley knife blades held apart by equal sized spacers. It’s all clamped together with small bolts.
The blank out of the vac bag. Router in grooves where the channel edges will be. These grooves a 6mm wide an about 10mm deep (deeper than the channels). The centre groove is 4mm wide.
Glue in balsa channel stringers. Only glue the bottom and outside face of each channel stringer. The centre stringer can be glued both sides.
When glueing in balsa channel stringers only glue the bottom and outside face of each channel stringer. The centre stringer can be glued both sides.
Once the channel stringers are glued in sand them flush with the foam blank. To sand each channel I’ve made a simple block (same width as channel) with #60 grit sandpaper glue to the bottom only with a small 5mm edge sand paper free. Using this block and a straight edge guide I sand in the channel. I’ve also got some tape over the adjacent channel/centre stringer. The sand paper free edge of the block rides over the tape. The foam should sand easily as it’s not glued to the channel stringer. Don’t sand fwd of the channel stringers.
Clean up and fine tune the channels with #120 grit.
Roughly cut the veneer to the outline of the board. Tape over where the channel edges will be. The veneer has the 4oz cloth underneath with a peel ply finish.
Carefully take measurements off the shaped blank, mark out and then cut each channel edge in the veneer. A number of passes per cut is better than trying to cut through in one go as you are cutting through tape-timber-4oz. I measured from board centreline to each channel to avoid cumulative error.
Roll/brush on epoxy to the underside (4oz side) of the veneer bottom, carefully tape to blank and place in vac-bag. Put the whole lot on top of the rocker jig.
Using a router/trimmer with follower sleeve remove about 4mm of the veneer edge. Remove only to the depth of the veneer (approx. 1mm). don’t cut to far forward.
Using a square edged block with small radius (approx. 3mm) you can now sand in the final channel shape, I used #120grit. I’m mainly applying pressure transversely in order to sand into the balsa stringer and not downwards into the veneer. Where the channel transitions into the flat mid portion of the board is also sanded in using this block.
Great post, somehow I missed it before. The bottom looks awesome.
For your rocker table, is the bend in the table permanent? If not how do you adjust it? I saw a previous post you made a bit ago, with setting up a rocker table, but my computer is having issues with the pictures.
The rocker jig has laminated ribs down each side. However the tail end of the jig, the laminate is not glue, i have cabinet screws through here. so you can flex the jig, tighten the screws and it holds the new rocker shape.
