Time: 8 Hours
I need to explain to those who are unfamiliar with how the RV-8 has its fiberglass cowl attached to the aluminum fuselage. The stock way of doing this is with piano hinge mated to the aluminum and fiberglass using the center pin to hold both halves tight together. This has worked well on thousands of RV’s out flying. There are challenges to this method, including difficulty getting the pin in and out when removing or replacing the cowl. Especially along the top and bottom of the cowl due to the curve. Another option out there is to use the Skybolt fastening system like many production aircraft. Even the Lear 45 I fly has similar fasteners holding the avionics doors in place. The Skybolt system uses receptacles mated on the fuselage and spring loaded pins mated on the fiberglass. When the two parts are brought together the pins get pushed in and turned to lock into the receptacle. These make installing and removing the cowling incredibly easy and reduce the risk of chipping/scratching the paint that’s usually associated with the hinges. I decided early into my build that I like the look of these fasteners and would use them on my RV-8. So like many projects in the build in order to do one task there are always other tasks that need to be finished first. I started out wanting to seal the firewall inside the baggage area and realized that I needed to have the Skybolt tabs riveted in place first. So that’s what led me to this task. Show my goal was to get The tabs riveted along the top curved edge of the firewall leaving the sides for later. The cowls have two main sections when it comes to the Skybolts, the perimeter of the firewall and to sides of the cowl the run from the nose aft to the firewall. The goal will be for the aft Skybolt of the sides, running from the nose aft to the firewall, will be in sync with the perimeter Skybolts. That way everything looks symmetrical, this will be much easier to show later on in the billed as I get to that stage. But for now I have to do a lot of planning so that that winds up. I will have some lead way in moving the tabs to get that all to work if I leave one or two tabs above the center line open. Those will be able to be moved or spaced so that all line up just right. For now I just need to be close so that a 1/8″ here or there won’t be noticed to get the spacing right. So for now I started working on the tabs which included cleaning up the edges and countersinking the holes that will attach the receptacles.
To start I’m going to center one tab, dead center of the top of the firewall. From there I will work my way outboard until I get to the sides and see how the spacing looks.
As I worked my way outboard I need to find out a rough area for the centerline of the cowl. I got a pretty close location mark with the help of my buddy Glenn. With that mark I was able to figure out the line that would represent the centerline of the Skybolts that will be above the cowl centerline.
With that one tab set I adjusted my spacing on the remaining tabs between this one and the top one to get even spacing. Once I was happy with this I removed the two lower tabs on both sides as I will drill those later. Then I match drilled the tabs with the firewall and forward skin.
I marked each tab with a piece of tape and a number so that I could replace them exactly where they go. After drilling I remove them all and deburred the holes. I also countersunk all the holes on the forward skin for flash rivets. After all the tabs were returned to their correct spots I used my pneumatic squeezer to rivet them all in place. Keep in mind I left the lower couple of rivets on the lowest tabs out so that I could get the next tab in place once I need to. My goal is that I will have some wiggle room up or down with the remaining tabs to get them aligned with the ones that will be on the cowl sides. That way they all look symmetrical. I made quick work of riveting the tabs in place after getting all the holes cleaned up.
After those were finished I moved to the bottom of the firewall. Here there are two small areas that would normally have small hinge sections but will now have two Skybolts.
I added a small piece of .032″ aluminum to the corners to close up the gap that will be between the cowl and firewall. It should also help align everything when installing the cowl. I cleaned up all these holes and got them riveted as well. Slow progress only because I have so little to do and 55 days until I go build my engine.