Ch. 5 - Longerons

Smooth transition (0.5 hrs)

In “Epoxy 101” I discussed the fact that fiberglass does not like making 90˚ transitions. 

When rounding an inside corner we must lay down a fillet to ease the transition, usually made of dry-micro, but sometimes flox as well, depending on the situation.

Covering an outside corner with fiberglass, we have to round the corner for the same reason, but we use a different radius depending on whether the glass fibers run perpendicularly, or diagonally across the edge.

Plans directions

In the case of the longerons, the plan calls for BID laid at a 45˚ angle, so a 1/8th radius of rounding should be sufficient to allow the fiberglass to lay smoothly around the corner.

Naturally, one could easily eyeball this, and take a sanding block to the inner/lower edge of the longeron, and “go to town” with it. But why go through all that trouble, when one could just as well acquire a rounding bit, pop it in a router, and perform the same action at 10 times the cost?

That’s what I thought! Something about power tools...

So, here’s the more expensive, though easier way of getting the job done.

The result is at the very least consistent throughout the 103” length of the longeron.

Longerons ready to go