toughened balsa

[mark roberts]

Hi, Im a newbie here so be kind please...
I want to make balsa tough, but still retain its lightness.
I have been advised that balsa is a superiour in many ways to comparable foams such as Divinycell, when used as a core material. Rather than use it as an end grain laminate spacer, I would like to use strips of it to a retain the natural spring of the wood.
Epoxy is the natural resin choice here, but is there a balsa treatment I can use to help both epoxy and balsa to work better together, the reason I ask is that I heard there is one, but getting info seams difficult

[cyclops]

A good fully cured epoxied soaked strip of balsa is NOT going to be flexiable at all. All the strength is in the stiff, brittle, outer coat of balsa. When the stress overcomes the breaking point, it will snap suddenly as the untreated core will have no strength. But this is probably true of all the foams also.------------Edit. Balsa and epoxy work perfectly together. No help needed.

[gonzo]

The reason to use end grain balsa was to remedie the problems of water intrusion. About 45 years ago they started using balsa as you intend. If there is any damage or failed caulk, the core saturates with water along the grain and eventually rots. With end grain there are two advantages: more compression strength and water can only travel a very limited distance.

[Deering]

Agree with Gonzo. If you want to strip pank, then consider using cedar or another rot-resistant wood. It'll weight more, but be stronger and have better properties when (not if) your epoxy membrane is broached.

[PAR]

Balsa is used as a core in it's end grain orientation because it takes advantage of several properties inherent in the wood. Using balsa (good luck finding long planking stock) as a strip, dramatically reduces the effective gains had in the end grain position, you're better off with another material, with better longitudinal strength.

As a core, it is ideally suited, as a piece of dimensional lumber it sucks big time. Reinforcing a weak material makes little sense. Regular epoxy will stiffen it considerably, but will also make it prone to easy breakage and increase it's weight substantially. Flexible formulations of epoxy can help the brittleness aspect, but you still have an unnecessarily heavy and weak material.

Cored or composite structures are highly engineered, not easily "winged" by the amateur. This is particularly true when trying to make light weight, strong elements.

You'll find most hold on dearly to engineering tricks or formulations that make things better. Others will protect themselves with copyright and patent law. I've just applied for two patents (unrelated) and wouldn't like to divulge the secrets for free either.

[yokebutt]

Mark,

A sandwich panel consists of skins, core, and- the adhesive holding them together.

You can do a lot by messing around with the bond-line thickness in an epoxy-based panel. A thicker layer of stretchy paste adhesive, or a few layers of resin-rich veil comes to mind.

Yoke.

[mark roberts]

Thanks for the replys guys, maybe Ive been barking up te wrong tree so to speek! ceader might just be a much beter choice, even though it will be heavier I imagin the compression will be better anyway.
It needs to be strip planked because retaining the natural spingyness and a good deal of sheer resistance is esential for this application.