Attaching the first strip is a very easy step. It only takes about 20-30 minutes. Although you have attached the fishbone to the frame it isn’t strong enough to really support itself at this point. Try hard not to stress your glue joints by keeping some weight onto of your fishbone. Wood that has been flexed or curved has a tendency to want to spring back. Without the weight keeping the board firmly pressed into the rocker table you could potentially build a board with less rocker than desired.
Fishbone Frame Glued to Bottom Skin
Two – (1/4 x 3/8”) strips without bead & cove edges.
2″ Spring Clamps, Homemade drainage clamps, or something similar to clamp the strips
Wooden Wedges & blocks
Iron & damp cloth
Saw & chisel (maybe)
Steps: Setting the Outline
- Add weights as you remove the strong-backs to keep the fishbone firmly pressed into the frame. If the glue has set there is little chance of the fishbone separating from the bottom skin but the board will try to straighten (lose rocker) without the added weight. The weights also keep the board firmly locked into the correct position on the rocker table.
You can see from the 3 straight lines made during the layout step how far you have to try and flex the bottom skin to the nose of the fishbone frame. With enough steam it would have been possible to continue to wrap this 4.5mm panel further around the nose. It is much easier and looks nicer to shape solid nose blocking to the desired curve. Note: The clamp that holds the nose was only removed for this picture and will remain in place for the same reasons as the weights.
2. Use a piece of the outline strip material to check the clearance and for obstructions. Use a Razor Saw or something similar to make adjustments if needed.
It is easily to fix this now and a pain to fix if you are already gluing. Problems like this are easier to cut flat with a saw before chiseling flat. If you chisel first you could potentially rip the surface of the plank, as the glue is stronger than the cedar.
3. With all the rib notches checked it is time to attach the first strip to set the outline. The technique I have found best is to work from the middle to the nose and tail. Hold a small piece (3-4″) of this material in one hand to set it at the perfect spot and then clamp with the other hand. It goes very quickly once you get the hang of it.
The hand pictured is holding both the first strip and a piece of the same material in the vertical orientation. This method ensured the next strip with only a bead edge would fit perfectly against the contour of the ribs. The notch in our fishbones are purposely cut twice the required depth creating a continuous path for water to drain in case you ever get water in your board. Hopefully this small precaution will never be tested!!
One clamp near each rib to start allows for a nice fair curve. Pick a really nice VG piece of your strip material for this first strip and this step will go smoothly.
4. Do not try and follow your layout mark without steaming the nose and tail part the last rib. If you flex the strip too hard to fast it will snap. In this example the strip is about 1/2″ inside the layout marks and needs to continue to at least the first of our nose blocking lines in this same position.
A damp cloth and some steam for a couple of minutes will allow you to easily follow the outline. Some builders try to follow the outline all the way around but it can be difficult and the nose requires blocking anyway.
After the steam has softened the wood just enough to perform your bend go for it. Clamp the curve as you bend from the secured end to the unsecured end. You can see how the butt end of a wedge is being used to hold the end of the strip in perfect alignment.
The tail is usually much easier than the nose. The single clamp holding the fishbone to the frame is left on as long as it doesn’t get in the way. The nail that locks the skin from shifting comes in handy to hold this tail strip before it is steamed.
Here is the wedge trick being used again after steaming. The outlines are used to trim the skin to approximately the right size and not as guides for this first strip. This template had a 3″ spacer added to the middle so the nose and tail overhang the CNC rocker table. This trick gives you a bit of scrap material to clamp to as shown.
The outline is complete!