At some point I’'m going to have to put my nervousness aside and do it. I have a 9/2 balsa blank already rockered and templated when I got it. I want to rip in length-wise in thirds, chamber it and glue it back with two dark wood stringers. I think I need to build a square frame around it and rip it on my table saw. The thickness is just short of my saw depth so I can rip it provided my frame is rockered too.
It’s a nice blank. Bought it for a song. Just kinda boring as plain balsa. Should I leave well enough alone, finish shaping and glass it? If I rip it, what kind of warp problems will I have? I’ve been reading the files and everything else I can find.
I would take a piece off 1/4 " plywood that is a little over half the size of you blank and rectangular and screw it down to the top of the blank. Line one side down the center and let the otherside runs out past the edge of the blank. Now you have a straight edge to put against the fence of your table saw. The 1/4" ply will bend to the rocker and if you line the srews up where one of your sringers will be the holes will go when you make that cut.
If your board is to be a wallhanger you may not want to go to the trouble of chambering and just rip it for the two stringers you indicated. If however you want to chamber it you’ll likely want to make more than two rips yielding three wide pieces which will be difficult to chamber effectively. For example, supposing your thirds are of equal width (nearly 8" each), whether you’re chambering with jigsaw, drill press, or router it’s going to be difficult to efficiently take out a nearly 4" depth of wood from each side of the center piece and even a greater depth into the outside pieces.
If it were mine, I would rip it into several more manageable widths and chamber from both sides except for the outside rail pieces. When planning the chambering, you’ll remember the deck will be shaped with a crown so you want enough thickness above your chambers so as not to shape yourself into a hole. If it’s an old school shape the bottom may have a rounded belly or hull shape also. You don’t necessarily need to put a stringer between each rip. The pieces can pretty easily be run through a jointer and glued back together nicely. If your table saw will cut the thickness any kind of cutting sled jig such as the 1/4" ply bed mentioned will work, however, your nails or screws can not be put on the saw line and you will need fasteners from the jig to the blank to hold each piece as you rip off the previous piece with each consecutive pass through the saw.
Again, if it were mine, I would probably use the bandsaw with a portable infeed and outfeed table, running the blank against a good fence. With the bandsaw you won’t have to worry about the depth as on the table saw. I would likely jig the blank to a more stable 3/4" plywoood base using 2x2s / 2x4s fastened to the plywood base across the base’s width and situated so the rockered blank has say a 2x2 running across the tail end supporting the underside of the tail rocker area and a 2x4 (+/-) running across the width of the plywood base just under the front third of the nose area. The cross pieces will provide stability to your blank from nose to tail, as the center of your blank will rest on the base and the tail and nose ends will rest securely atop the cross pieces. This method will keep the blank from see-sawing up and down. Perhaps use finish nails protruding up from the base and cross pieces onto which you just press the blank down to hold it firmly to make your rips. Any small nail holes can easily be filled with sanded balsa dust mixed with white glue). Have a friend ready to lend a hand.
If you really want to chamber to the max with least amount of drama and risk of shaping yourself into a chamber, rip the blank to widths, spot glue it back together with just enough glue to hold it together (doesn’t take much), rough shape the board, pop it all back apart, chamber the pieces, then glue it all back together again using rubber strapping, cut pieces of rubber from pond liner (avail. at home center), or Jim Phillips method of bicycle inner tubes. Put stringers where you like and you’ve got it. With a little planning and some invested time it should go pretty smoothly.
Perhaps others like Phillips with more experience can jump in and give their wisdom, but something along this line is the way I would do it. Go for it!
Have you considered using a band saw. The depth would not be a problem. You could incorporate Marke’s suggestion to create an edge to run against the fence. It would reduce the possibility of the blade tracking.
If the blank looks good now, perhaps you should just finish it off. You can always strip and rip it later if you are really unhappy with the results.
If you do rip it along the existing glue joints the warp should not be bad. The planks were probably milled to begin with and it sounds like the blank has been glued up for some time. If it does warp it will probably be nothing you can’t take care of with some bar clamps.
As opposed to adding stringers you might consider doing some inlay work. Saw a board somewhere on the web with a stylized wave in a contrasting wood running down the center - it looked nice.
Good luck.
Patrick
Edited Comment: Didn’t see Richard’s excellent post before I posted - must remember to use the Refresh button in the future. Sorry.
I think RichardMc’s method of rough shaping first, then chambering and glueing back the pieces together is the good one. But you don’t need to glue your lumbers together for rough shaping. I use fluted wooden pegs that are forced into slighltly smaller diameter holes in the balsa to hold them together. They are easier to disassemble for chambering, and they are equally useful when glueing since they prevent the pieces from sliding one against the others. I’m not sure this is perfectly clear… Sorry, I have no shots to provide that might have explained better…
before chambering I would consider, how much does your blank weigh now? Also are you 100% sure it’s solid balsa? I remember reading here from one guy who had what he thought was a solid balsa blank, but when he shaped it he discovered it had foam-filled chambers already.
By the way, where did you get a nice 9’2" balsa blank for a song? Inquiring minds want to know…
I’ve only done a few Agave boards, but I’ve paid my dues in the cabinet shop. What I’ve done is a lot like mention above. First I take a long straight peice of masonite, glued up to reach max blank length if necessary. Then I snap chalk line my stringer layout on the blank. I use the masonite straight edge as a skill saw straight edge and saw the blank into pcs.(most johnny homeowner bandsaws don’t have a wide enough throat to push a board through, but if you cut it into enough pcs I guess it would work) I run the pcs through a planer jointer. then I glue the pcs back together with brown paper and brown glue in between the joints. Using paper between the joints with a little glue will alow you to break to joints apart with little pressure, but will allow you to shape the board without having it fall apart. So we have a sawed, jointed and glued/papered back together blank. Now you shape the board as usual, once its done you break the glue lines, chamber out what you feel is necessary, run the pcs through the jointer to skim off the little bit of glue from the break, put the stringer pcs in, and glue up full strength. Finish off blank & glass.
Wonderful. I knew this would get me pumped up to do it. All good. Thanks to all. The plywood masonite thing is great. I’ll also do the brown paper glue up. Off the garage.