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Alternative to Skybolt die cut brackets ?

Larry DeCamp

Well Known Member
I am ready to install the horizontal parting line brackets on my SJ cowl. My -3 had 3/32 rivets in piano hinge per plans. One or two rivets have shown motion on the cowl surface. If I use flush rivets on the Skybolt stampings, I will glue them to the glass cowl with 3m 2216 to distribute stress. However, I think a glass strip epoxied to the lower cowl half with Skybolt fasteners riveted in the top half of the strip would be the ultimate.
Comments appreciated.
 
I am ready to install the horizontal parting line brackets on my SJ cowl. My -3 had 3/32 rivets in piano hinge per plans. One or two rivets have shown motion on the cowl surface. If I use flush rivets on the Skybolt stampings, I will glue them to the glass cowl with 3m 2216 to distribute stress. However, I think a glass strip epoxied to the lower cowl half with Skybolt fasteners riveted in the top half of the strip would be the ultimate.
Comments appreciated.

I made a .050" aluminum strip for the split on my 7. No saw tooth shape. But - -it had to be shaped in 3 dimensions to fit. Hysol to the cowl. It ended up shaped like a section of banana peel.

DanH has another option. Make a 4 layer rail of fiberglass. It will fit perfectly. I think he as the example in the fiberglass section on VAF. [recommended]
 
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Can you point me to the Dan Horton post?

I can't find a Dan Horton post regarding the rail you discussed. It sounds interesting.

Thanks!
 
I can't find a Dan Horton post regarding the rail you discussed. It sounds interesting.

Thanks!

Basically, he fit and taped (?) the cowl halves together, masked the inside of the upper half, and laid up a flange on the lower half along the split on both sides. Popped it apart when the layups were cured, then installed skybolts.
 
Skybolt fasteners on the firewall

I have used Skybolts on three firewalls and have never used their interlocking flange because there is an easier method. The assembly of a series of flanges isn't so simple.

What is simpler, in my opinion, is to cut a strip of .063 aluminum 2 inches wide and as long is required to go around the firewall. You can do it in two strips, joined in the center. You take one Skybolt interlocking flange and determine your fastener spacing (typically 3 inches) and layout however many fasteners you will need. In minutes you can cut out the fastener tabs on the band saw and with a little filing, or use a 1"belt sander. You attach this continuous strip to the firewall. You measure back a certain distance from the center of where the 5/8" hole will eventually be (where the 1/4 turn stud goes), but don't drill anything. Once the cowl is fitted and laying on the protrusion, you drill a #30 holes through the fiberglass and through the .063 strip. Once the cowl is fitted and held in place with clecos, you remove the cowl and mark the location where the fasteners will be attached, making your own template with three holes in a row 1/2 inch apart. You may consider using a #30 hole only in the center and #40 for the two outer holes. In the end, use an actual fastener (as a drill guide) to finish drilling the two outer holes to #30. When your satisfied all the fasteners are in the correct position, drill the center hole out to 5/8 hole, using a step drill. There can be some assembly and check that all holes are where they are suppose to be. The last step is to drill out the #30 hole in the cowl to 15/32" using a 1/2 inch unibit.

It takes longer to explain than actual do it.

Jake Thiessen
Independence,Or
 
Sky Bolt spacing

I recommend starting the sky bolt spacing around the firewall by starting at the area around the upper motor mount. In my installation (RV-8) I spaced about 3 inches apart, working from the upper centerline. I ended up with a sky bolt directly over the upper engine mount. I was working this with the engine mount off and did not notice the position of the engine mounting hole in the firewall until everything was installed. Sky Bolt managed to scrounge up some VERY short cam locks, but I may have gotten the last of them. (it has been a while, so they may have more in stock.)

I did use the Sky Bolt stamped mounting gizmos. Were I to do it again I would use material that I cut in the shop.
 
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