Ch. 5 - Fuselage sides LH - Part 2

Lower longeron (6.7 hrs)

The good news is that the air bubble I was chasing last night is gone.

Bubble-less surface

Unfortunately the bad news is that another bubble appeared somewhere else, and I’ll have to "terminate her".

No, it's not a snake!

Since I did not use any flox to radius the 90˚ angle above, I was almost expecting air bubbles to appear at the intersection with the foam board. I’m actually surprised I did not get any more than that. In retrospect I should have eased the transition, and I definitely will when I make the right side-panel.

To correct this issue, I had to drill two holes at either side of the bubble, and inject some epoxy with a syringe I "borrowed" at my last dental appointment.

I was told this should work, but I had never actually done it before.

Wow, that was awesome! I will definitely use this technique again next time I screw up.


By the way, I ended up drilling another hole further to the left, and filling the remaining void with epoxy.


One additional item I had to take care of, was the removal of BID I had laid on the last 0.5” of the longeron. Apparently it wasn’t supposed to go that far, so I took a razor knife and cut it off. Simple enough.

BID extending all the way to the rear end of the top longeron

Removing the offender

Problem solved

The new item for the day was the lower longeron. I drilled holes through it, and the cured fiberglass, and inserted some nails to hold the wood in place. 

Working on the lower longeron

Because the longeron needed to curve upward in the aft section of the fuselage, I cut some slots on the top side of the longeron, to aid in achieving the proper curvature.

Slotted longeron temporarily in place.

"Nice curves!"

After dry fitting, I mixed some wet flox, applied it to the longeron’s back side, and put it back in position.

Applying wet flox while "enjoying" the hot and humid midday

A substantial amount of weight is useful to hold the longeron down while the flox cures, but its sharp edge makes it challenging to weight it down without damage. Since I am not that smart, I will admit to shamelessly plagiarize the following “load distribution scheme”.

I wish I could take credit for this idea

Basically it consists of a grove cut into some scrap lumber, matching the triangular profile of the longeron. This was easily accomplished with the table saw, and the results were as brilliant as the individual I stole this idea from (thanks again Walter).

I was then able to pile up as much weight as I could physically fit on top, without any fear.

Plenty of weight holding things down while the flox cures