A really good couple of days in the shop this week.
With the first slat underway, I was time to begin the task of wrapping the top skin over the ribs. To make this easier, Ron has built a "slat box" as show below. Made from plywood, it is essentially a reverse or negative pattern of the top surface of the slats. Green painters tape is added to any contact point to prevent scratching the skins:
Before getting the slat mounted in the box, I had to tuck the underside into the folded over trailing edge. It's tight, and I used a thin piece of wood as a slide to get it tucked under. The resulting pinch of the trailing edge fold is enough to keep everything together for mounting in the box.
Now it fits in the box and can be strapped down to complete the final wrap over.
I used a piece of HSS tubing to act as my spreader across the rear of the slat.
A look inside the each end confirms things are close enough and I can begin drilling the top side rivet holes.
To access the top side (which faces down in the box) I tilted the box on it's side:
Strategically cut access holes in bottom of the slat box line up with the 3 internal ribs so I can get at least 3 rivet holes drilled through the skin into the ribs:
The fourth hole is to far down inside the box to drill it accurately, but that can wait until everything is out of the box.
Put the box back upright and added some more blocks. This allows the force of the straps to transfer down more vertically, tightening everything up and I can begin to drill and cleco the trailing edge down on the underside:
Take the assembly back out of the box again and finish the top side rivet holes I couldn't access before. The finger clamp holds down the rear curve of the skin to the double bend flange underneath:
Layout the rivet line across the top rear. These will be A4 rivets with 50mm spacing:
To ensure I had everything locked down where it needs to be, I flipped everything over and drilled out everything to A4 on the underside:
Back ipright again, drilling the topside rear rivet line, A3, then up to A4 on 50mm spacing. I also completed the front rivet holes in each of the nose ribs. Everything is tight and square.
And it all comes apart again for final debur and priming:
One of the challenges I'm facing is how to make the inside of the slat structure accessible for the inspector to see my workmanship. The fold-over design of the skin makes leaving it open like the flaps, elevator etc impossible. I discussed this with Ron and confirmed with Roger at Zenith that adding a lightening hole on the flap ribs was acceptable here. I'm not looking to save weight, just want an easy way to see inside. This viewing can be done with a scope.
I carefully added some small holes in the centre of the slat ribs using a step drill. This will allow a camera scope inside.
I flanged the hole slightly to add strength:
I scratched off some of the primer doing the holes, but they cleaned up nicely and I re-primed them.
The new access hole creates a new small problem. The skin support L now protrudes over the hole:
the quick solve for this is to trim the L a bit before riveting. I also trimmed it back a bit on the top of the bend flanges to ensure clearance for the top two rivets.
Primed the skin and once dry started the re-assembly which goes back together fairly quickly
With everything drilled out to A4 and clecoed, the slat skin is tight to the ribs and looks good for riveting. The access hole turned out really nice - there should be lots of room to look inside using a scope.
Very pleased how this turned out using the steps I came up with worked well, I'll be following the same order when I build the other three. Again, I'm rather surprised by the size these are, it gives a good impression about the wing dimensions.
One to the next one, it all starts with alying out the bends. Thankfully I wrote down the measurements and bend order from the first one - that will make the next three the same.
Very happy how the first slat turned out considering how complex and tight the bending that is expected of the skin. It's not a complicated structure, but "fun" to do.
Back in the shop soon to get the rest of the slats done. I'll be continuing work on the 3D scanning/printing project too, exciting things coming up. Thanks for reading.
Husband, father and 911 dispatcher. Long time pilot with a licence that burns a hole in my pocket where my student loan money used to be. First time aircraft builder. Looking to fly my own airplane.