Balsa core "filler"

What would be an appropriate filler (strong, sandable) for a balsa core?
As I lay up the balsa blocks, there will be some gappage between them as they wrap around the curve of the hull. I will try to minimize this by going to a smaller block, but I do anticipate gaps. I would like to use something that mimmics the sanding properties of balsa.
Would it be approprate to leave the gaps, sand hulls fair, and then do an epoxy fillercoat?
Thanks for your input.
Rob

 

Microballounes mix in epoxy

 

Rob,

I doubt you will have any luck fairing end grain balsa. Some of the blocks are usually much harder than other ones to sand. Gaps can be filled with putty, preferably something as strong as the balsa itself. Laminate the outer skin onto the balsa, then fair it. If you have the stations either CNC cut or trace them carefully from a full size mylar, (we use a spur wheel for that) and take your time to set them up accurately, you should not need that much goop to fair it.

Yoke.

 

Thanks- I've got some "contest grade" balsa coming my way- should be pretty consistant in density. Just a gentle shaping is all I'm after so that I don't have to do as much work after the outer lamination is on.

Rob
ps
Jean-Francois- Votre Englais c'est cava. Mon Francaise c'est terrible!