SECTION 10: Internal Ribs

Before You Start

Modified applicator syringe with tulip tip (shaped using heat gun and pencil) for back-sealing rivets
- It can be filled using ziplock baggies, 24g in the bag, snip a corner, and pipe the sealant into the applicator.

Section 10-19 only applies if you did not purchase the Quick Build (QB) fuel tank option. QB tanks are built and sealed at the factory.
These tanks are significantly more difficult than leading-edge-style tanks on other RV models. Budget three or more weeks of full-time work.
Each frame uses approximately 7–10 oz of sealant; each skin requires 6–8 oz or more and must be worked start-to-finish in one session — do not stop mid-skin.
Mixing ratio: 10:1 by weight. You may run out of hardener first. Store unused mixed sealant in a freezer to extend working time by up to a day.

Each skin install requires the initial sealing of all ribs, stringers and perimeter parts. And then some more to layout smooth fillets were possible after everything is riveted. Then back sealing all the interior and exterior rivets. And finally cleaning all the squeeze out up off the rivets heads. Each rivet needs to be sealed with enough sealant to squeeze out a bit. Twirling it as it goes in helps to even out the sealant round the rivet head.

The plan is to build the frames, then the bottom skins. Then do a bunch of filleting and back sealing to make sure the bathtub is well sealed to include back sealing every rivet from the inside. When installing the top skins this latter part of back sealing rivets is difficult and the factory doesn't do this on the top skins, at least according to the plans.

Sealant dollops that squeeze through rivet holes: push them back against the flange with a palette knife. Use them to back-seal rivets promptly, or let them harden and pull off before back-sealing.
Back-sealing top skin rivets is possible using the modified syringe and a borescope (e.g., Fox Valley units). Allow approximately two hours per bay.
Assembly sequence variation: install stringer end tabs onto ribs first, then install ribs to the rear spar. Stringers then drop in easily — avoids inserting a sealant-covered pre-assembled frame between the end ribs.
Pre-scuff the skin surface under rivet lines before priming so sealant adheres better.
The outboard end of each interior stringer has one rivet that is NOT installed — this hole ties into the wingspan mid-chord stringers.
Acetone cleanup: scrub 5–8 rivets at a time and wipe before the acetone flashes off.