During downtime on riveting the fuse side skins, I made a start on step installation.
The first step involves drilling bolt holes into the Delrin support blocks. To aid in the drilling, I 3D printed a drill template.
At the same time, I also designed and 3D printed a drill template for a doubler on the opposite side of the baggage floor rib that I plan to install for added strength (as a few other builders have done).
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| Bolt hole drilling template clamped to Delrin block |
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| Drilling template used to mark out doublers on Alclad sheet for cutting |
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| Hole saw used to drill out 1.5" hole in center of doublers. This diameter matches the center hole size in the Delrin blocks |
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| Using the drill press to match drill and cleco the Delrin block bolt holes through the drilling template. Holes were drilled to #12 and then reamed to #10 |
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| Match drilling rivet holes into the doublers using the doubler drilling template as a guide |
After deburring the open ends of each step, I test fitted both through the previously riveted step brackets below the baggage area. I found that I had to also debur the holes in the skin to allow the steps to fit through without binding, but this was easily achieved with a few passes of the 1" deburring wheel in the die grinder.
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| Skin hole and step bracket line up perfectly to allow the left step to slide in with zero interference or play |
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| Delrin block placed over the end of the step and rotated to align with the baggage floor rib for match drilling |
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| Same outcome with the right step. Everything aligned perfectly! |
With the steps fitting well, I removed them and primed the insides using boiled linseed oil. The steps were then left for several days for the remaining oil to drip out and coating to fully cure.
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| Step inner surfaces protected with a coating of boiled linseed oil |
Next, I clecoed in the baggage compartment floors as directed in the plans. However, I found that this severely limited space to match drill the Delrin blocks to the baggage ribs, and also wasn't really needed for hole alignment as holes aligned well between the floors and ribs without any additional persuasion. I therefore decided to remove the baggage floors prior to proceeding.
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| Baggage floors clecoed to forward section of baggage area and to the seat back brace |
With ample access after removing the baggage floors, I was able to easily match drill the Delrin support blocks to the baggage ribs using the right angle drill.
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| Right angle drill fit easily into the space between ribs to allow match drilling of Delrin supports with a #12 bit |
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| Bolts were temporarily inserted to maintain alignment while match drilling. Note that Delrin blocks had previously been labeled to indicate correct orientation |
After match drilling the Delrin support bolt holes to the ribs, I next removed the supports and match drilled the resulting bolt holes in the ribs into the doublers I had previously fabricated.
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| Doubler match drilled to rib via the bolt holes |
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| With bolts passing through the Delrin support blocks, ribs and doublers, I was happy with how the step tube aligned parallel to the bulkhead and fuselage floor |
I then match drilled #30 the doubler rivet holes into the rib, clecoing as I went. This was easily done with the right angle drill. The process of match drilling doubler bolt and rivet holes was then repeated for the right step.
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| Match drilling rivet attach holes for the step doublers |
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| Doubler rivet holes were countersunk for a flush rivet head, and doublers were primed |
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| Doubler rivet holes in the ribs were dimpled using a #30 close quarters dimple set and blind rivet squeezer |
With the doubler and Delrin block fabrication complete, it was time to rivet and bolt these in place. Riveting the doublers to the ribs was a little challenging due to the limited space, but I was able to squeeze several rivets along the top and sides of the doublers, and carefully bucked the remaining rivets using a 3/4" Boeing flush set.
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| Left doubler riveted to rib |
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| All shop heads came out great, and bolt holes aligned well |
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| Right step doubler shop heads also came out great considering that I did not have additional access through the baggage door opening on this side |
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| Right side doubler and rib bolt holes also aligned well |
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| Delrin block bolted to left side rib and doubler |
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| All bolts torqued to spec |
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| Same for the right side Delrin block bolts |
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| Right side Delrin block ready for step to be inserted |
I then fabricated a jig to hold the hold the steps at the correct angle and distance of 45-1/4" from the aft center section bulkhead. The jig was securely attached to the fuselage cradle, and had additional plywood blocks at the step end to allow clamping of the step at the required distance. With the clamps in place, the step had no forward or aft movement, and I only had to ensure that it was pushed in to the step bracket so that the weld was up against the skin.
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| Left step clamped to jig and held securely at the required distance |
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| I double checked measurements after clamping to ensure distances were correct |
For the bolt that holds the step in place within the step bracket, I decided to upsize it from AN3 to AN4. I believe this will hold the step even more securely. I had also previously ordered the
TCW step bushings for additional strength, and the holes through these are already sized for an AN4 bolt.
In order to drill the bolt hole through the step bracket and step, I 3D printed a
drill guide (originally designed by Allen Glen) that I modified slightly, and inserted a bushing for a 15/64" drill bit. This made it very easy to accurately position and drill a bolt hole for an AN4 bolt while ensuring that it was drilled through the center point of the step and bracket.
I will later install an
Airward step access panel on each side of the baggage area, so deviated from the plans a little here and drilled the bolt hole at a 45 degree angle from vertical (ignoring the pilot hole in the step bracket).
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| Clamp used to prevent step from sliding out while drilling |
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| I was able to use a small electric drill placed right next to the skin to drill the initial 15/64" holes |
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| After drilling the bolt holes to 15/64", I reamed them to 1/4" |
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| After deburring, all holes looked good in both the step brackets... |
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| ...and in both steps |
Steps were then primed with Kirker EnduroPrime (a 2-part epoxy primer) prior to final installation
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| Steps sanded and cleaned prior to priming |
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| Primer applied and left to cure for the left step... |
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| ...and for the right step |
After a couple of days, with the primer fully cured, I inserted the step bushings. These had to be very lightly sanded to fit well with some friction to hold them in place, but otherwise there was no issue getting them lined up with the drilled holes. I used a 3/4" wooden dowel to push them in, and 5/8" webbing in case they needed to be pulled out prior to final placement. I had also made sure to prime the bushings with EkoPrime.
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| Bushings in place within the steps and bolts passing through easily. Webbing was left in place until after steps were installed |
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| Bushing in place within the step tube. Thanks to the drill guide used earlier all holes aligned well. |
Finally the steps were inserted into the brackets, and the AN4 bolts were attached and torqued down.
One note here when upsizing from an AN3 bolt to an AN4 bolt, the plans call for an AN3-20A bolt and I had initially purchased an AN4-20A bolt to replace it. However, I had not taken into account the thicker nut used for AN4 bolts, and an AN4-20A bolt would have resulted in threads barely visible beyond the end of the nut. I instead purchased AN4-21A bolts and these allowed for at least 3 threads visible after torquing down the nuts.
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| Left step bolted in place |
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| Right step bolted in place |
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| I also inserted the bolt from below rather than above as the plans depict. This makes it easy to torque from the nut side |
Build Hints:
- If upsizing a bolt from AN3 to AN4 and using AN365 stop nuts, make sure the AN4 bolt is one size longer than the replaced AN3 bolt to account for the longer nut being used
Primer used: ~5g EkoPrime (step doublers), ~50g Kirker EnduroPrime (steps)
Priming Time Taken: 1.0 hours
Time Taken: 10.8 hours
Dates: October 19 2025 - October 20, November 2, November 17 - December 4 2025
Step Installation Total Time: 10.8 hours
RV-10 Build Total Time: 1227.6 hours
Priming Total Time: 143.6 hours (not included in build time totals)
