Balsa grades and cuts

Looking to source my balsa for the next project, and contacted a supplier about different grades. I remember reading here that bert uses “c” grade, so I asked about that.

What I was told was there was either A or B grade, with B being the one with mineral discolorations, grain, etc… There are also different cuts of balsa, too. They are labled A, B, and C cuts, confusingly enough.

So, I could probably save some money with the B grade, since it’s not a aesthetically perfect… But what cut to use? What is the difference in the cuts, anyway?

Must have something to do with the cut against the grain. It’s amazing how variable your planks end up to be regarding flex. We always pull out the softest or flexiest(?) ones for the nose. tail and rail bend overs…

It would be nice to determine the cut A-B-C to control the flex kind of like how you slice a piece of meat up to get something tough or tender… Limpies for the big bends and stiffies for the middle and tail…

I found some 1/16"x15"x96" maple veneer on Joewoodworker It was supposed to be for making skateboard decks…

gonna try that as a center board stiffener with diagonal balsa going out to the rails like Bert did.

Charlie uses Obechi startegically placed down the middle to get the same effect… He said they make police batons out of the stuff… I was trying to find Hickory or guava as those have alot of snap to them to act as a center running board spring like bouncing of a diving board.

Still got to figure out the rails… Would be neat to have some way of pre fabbing them out of some type of long wood and frame them up like a house… Maybe that wigglewood ply I saw here http://www.northamply.com/spectrum.html

Back up to some long balsa wood pieces will be my 4’x8’1/2" corecell sheet like Benny1 did with his snowboard design… Yeah I know you can pre-glue you strips to make a sheet but that alot of work just to have something cut out your rail bands from.

DanB

can you elaborate how you saw Bert do his rails?

I believe you said they were real short pieces versus long 42"48" pieces of balsa…

more epoxied joints = stiffer or

more joint’s create stregic flex points?

from SIG Manufacturing, info aimed at airplane modelers, but if you’re doing balsa…

"BALSA GRAIN – LEARN HOW TO IDENTIFY ALL THREE GRAIN TYPES

In selecting balsa sheets for use in your model, it is important to consider the way the grain runs through the sheet as well as the weight of the sheet. The grain direction actually controls the rigidity or flexibility of a balsa sheet more than the density does. For example, if the sheet is cut from the log so that the tree’s annular rings run across the thickness of the sheet (A-grain, tangent cut), then the sheet will be fairly flexible edge to edge. In fact, after soaking in water some tangent cut sheets can be completely rolled into a tube shape without splitting. If on the other hand the sheet is cut with the annular rings running through the thickness of the sheet (C-grain, quarter grain), the sheet will be very rigid edge to edge and cannot be bent without splitting. When the grain direction is less clearly defined (B-grain, random cut), the sheet will have most intermediate properties between A and C grain. Naturally, B-grain is the most common and is suitable for most jobs. The point to bear in mind is that whenever you come across pure A-grain or C-grain sheets, learn where to use them to take best advantage of their special characteristics.

A-GRAIN sheet balsa has long fibers that show up as long grain lines. It is very flexible across the sheet and bends around curves easily. Also warps easily. Sometimes called “tangent cut.” DO use for sheet covering rounded fuselages and wing leading edges, planking fuselages, forming tubes, strong flexible spars, HL glider fuselages. DON’T use for sheet balsa wings or tail surfaces, flat fuselage sides, ribs, or formers.

B-GRAIN sheet balsa has some of the qualities of both type A and type C. Grain lines are shorter than type A, and it feels stiffer across the sheet. It is a general puropse sheet and can be used for many jobs. Sometimes called “random cut.” DO use for flat fuselage sides, trailing edges, wing ribs, formers, planking gradual curves, wing leading edge sheeting. DON’T use where type A or type C will do a significantly better job.

C-GRAIN sheet balsa has a beautiful mottled appearance. It is very stiff across the sheet and spits easily. But when used properly, it helps to build the lightest, strongest models. Most warp resistant type. Sometimes called “quarter grain.” DO use for sheet balsa wings and tails, flat fuselage sides, wing ribs, formers, trailing edges. Best type for HL glider wings and tails. DON’T use for curved planking, rounded fuselages, round tubes, HL glider fuselages, or wing spars."