I just started a new balsa board project. Thought there might be some interest in seeing the process of making a balsa blank (out of planks) from the very beginning.
These planks are direct from Frost Hardwood in San Diego. No additional milling, joining, planing, sanding, etc., has been done on them. Yet as will be seen in the pictures, it is possible to get a close fit even before the planks have undergone any such additional work.
Of course, not all planks are going to fit together this nicely. To get such a nice fit right off the bat it is necessary to have a good selection of planks and then mix and match them, working them like a giant jig saw puzzle. Some will fit together quite nicely. Some will not.
If you can get a reasonably good fit at this early stage then all that should be needed is some sanding to get the surfaces as flush as possible.
(Note: This process works well for shorter boards. For example, this will be a 5’6” kneeboard. Longer boards would entail more work.)
Next set of photos. The last photo shows that even a credit card cannot be slipped between the planks when they are held snug. At this point they have not undergone any additional sanding, planeing, etc.
Hey, retroman. I’m also in the process of gluing a balsa and ceder blank together. Three 3/4" western red ceder stringers and end grain balsa. The ceder is recycled outdoor furniture and the balsa is from the dumpster at work. End grain balsa would not be my first choice, but seeing I’m going to have a 10’ blank for nothing, and as this is my first attempt at shaping balsa, it seems a prudent way to go. Also I have not shaped a board since the late 70’s. This is going to be a long term project. Finding the time with all the restorations i’ve got to do, is going to be hard. I might just have to make the time. Good luck with your project. platty
The first photo is the blank placed together dry and staggered.
The second photo is the board I plan to use as the shape.
I’ve seen methods before where they cut the rocker (with a little extra to play with) into the planks with a bandsaw, and then glue up the planks. Saves a whole lot of scraping and shaving that way, not to mention the increased precision that method would seem to give. Although you got to be pretty precise with your glue up then… That’s how I’ll do it when I get around to it…
If you don’t mind me asking, what did those planks run you, cost-wise?
OK, here are the next couple steps in the process of making your own balsa blank.
The first attached photo (to this post) shows the laid out blank before it is rough cut.
Notice that the ends of the planks are not all even. Remember, you are after the best possible lateral (side to side) fit between planks. That is why it is necessary to have a number of planks to pick and choose from for this quality (the other important quality to look for being planks that are lightweight as well as strong).
Make adjustments as necessary. Use your template in this process to ensure that the ‘core’ of your blank is big enough to accommodate the board you are ultimately aiming for.
The other two photos show the template (in this case, a 5’ 6” Lis fish) being placed on top of the blank to draw the outline of the board.
After drawing the outline on the blank, all of the planks can be separated and rough cuts made. Be sure to save the larger pieces you cut off each plank for your next board! (Note: Before separating them, it is very helpful to number the planks and label the tail and nose. Reassembly will be greatly simplified by doing so.)
Do not try to make an exact cut along the outline. Leave at least a quarter inch or more excess all around the margins.
Although the original outline drawn on the board is there, it is hard to see in the pictures. The cuts do not follow it closely at this point, anyway, because it is hard to cut a precision curve through balsa (with a hand saw, anyway, which is what I use). Much easier to cut in straight lines. (Indeed, if you try to cut a precise curve following the desired outline with a hand saw you will not only be unsuccessful but also likely damage the blank as large pieces may break off taking huge chunks out of the plank!)
Have patience! After the blank has been all glued up, then the precise outline/curves of the board will be shaped into it using a block plane and/or surform.
The next steps will be: Shaping some (but not the final) rocker into the planks; preparing the surfaces to be joined (glued together); and finally, gluing up the blank (with clamps). Stay tuned…
There are several methods for getting rocker. It all depends upon how much you want or require.
For example, this board, a Lis fish, will only have the amount of rocker that can be shaped into the blank as is (3.25" max). That should be enough, however, as a Lis fish does not require a whole lot of rocker.
If you need more, then you can do something known as ‘scarfing’, where additional planks are glued on top (usually on the nose section). Scarfing involves more work and bit more technique, but it will allow for a much greater amount of rocker in the blank (and thus board). Scarfed joints, if done right, tend to be quite strong.
It is not advisable to try to ‘bend’ rocker into the blank, as like any wood balsa has a strong ‘memory’ and will want to return to its original shape.
Before Epac jumps on me about the ‘wide’ gaps apparent in these latest photos, I should mention that obviously I am not holding the planks together (unlike the credit card photo). If I would hold them together the spaces would not be there.
In addition, the surfaces to be joined of these planks have not been sanded yet. Once sanded they will be quite flush (balsa is extremely sandable), especially as they already fit quite closely together!
Of course, the ideal would be to precisely join them using the appropriate equipment (power jointer and planer), but not only do I not have access to such tools, my goal is to build wooden boards using only hand tools on my part (obviously the planks were cut and milled with power tools before I got them).
I have to applaud your reusing these woods. However, since the grain of the redwood stringers is running is perpendicular to that of the balsa, sanding/planing is going to be a big problem!
Retroman, your point about the balsa grain being perpendicular to the stringer has been causing me concern for a while now. It is not the most ideal way to do it from a strength and working the timber point of view. In theory, if I have enough balsa to make a blank the way I have it running in the photos, then I should have enough if I dock the balsa to fit between the stringers, and have the grain running in the same direction as the ceder stringers. Back to the drawing board.platty
This is where I step in, go ahead and glue it up with out jointing first, but you will have nice fat gluelines that are hard as shit to keep at the same level as the wood to each side. The thinner the glueline, the easier to shape and finish, look at those 50 year old balsa boards and see for yourself how bad the seams look. “No one has time to do it right, but time to do it over”
But what do I know, I only build about a hundred or better wood boards a year
