While figuring out the details of the conduit and cable routing that I would need to run under the baggage area and rear seats, I decided it would be a good time to rivet in the rear seat floor pans. There won't be anything running under these, and it is much easier to rivet these now without the rear seat floors in place than to follow the plans and have to lift up the floors to reach some of the rivets.
The first step after priming the floor pans involved riveting nutplates to the bottom of the pans that will later be used to secure the flap torque tube covers.
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| Nutplates backriveted to both floor pans |
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| I was able to squeeze a few of the nutplate attach rivets near the edges of the floor pans |
Prior to inserting the floor pans in place, I vacuumed out any debris in that area and made sure there was nothing unwanted left there, as it would not be possible to get access under the floor pans once they were riveted in place.
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| Left floor pan area clean |
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| Right floor pan area clean |
I was expecting insertion of the floor pans to be a challenge based on the experiences documented in other builder logs. However, in my case it really wasn't that bad.
Inserting the floor pan at an angle to get the front under the seat belt attachment points, and then sliding it forward while simultaneously angling it down at the rear, allowed me to then give it a push at the aft side to get it past the rear spar attach bar. It then settled nicely onto the floor stiffeners.
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| Left floor pan clecoed to the bulkheads, ribs and stiffeners |
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| Right floor pan clecoed. The additional filing that had been done at the front of the floor pans to clear the seat rail supports really paid off in easing the installation |
As I had skipped some of the initial floor pan prep steps to avoid inserting and removing them multiple times, I still had to match drill holes in the forward flanges of the floor pans into the aft center section spar web. After taping off any areas where debris could enter and be difficult to remove, the #30 holes were easily match drilled using a 1/8" bit followed by a #30 reamer.
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| Holes match drilled into the aft center section spar web |
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| Both floor pans ready for riveting |
I began by riveting the floor pan flanges to the bulkhead and ribs using AN470 solid rivets. Most of these were easy to buck using a single offset rivet set. The more difficult ones to set were in the areas
Also for the forward most rivet along both the outboard seat rib and tunnel, I decided to use an MSP-42 blind rivet rather than a solid rivet as it was difficult to place an offset rivet set correctly due to interference from the seat rail supports.
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| Outboard seat rib rivets set carefully |
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| Finished off setting flange rivets through the aft center section spar web and the right floor pan flange |
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| One other location where I used a single MSP-42 rivet was along the rear spar bulkhead where the rivet lies right next to one of the rear seat ribs. I did not feel that a solid rivet would set well here |
To complete the rear seat floor pan installation, I just had to set CS4-4 blind rivets into the floor stiffeners. This was a quick and easy process.
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| Right rear seat floor pan installation complete |
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| Left rear seat floor pan installation complete |
Finally, I cut some cardboard to size, and lay it down to protect the floor pans going forward.
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| Floor pans protected from any potential damage |
Dates: March 10 - March 18 2026
