Wings 20-5 Lap Joint

Working on some wing skin prep and step 8 of 20-5 tells me to modify the lap joint between two skins and references this earlier section....



Since I went the QB route I missed out on this earlier fun but I looked at the piece. To me it looks like they just put a 45 degree bevel on the over lapping skin, can't see what, if anything they did to the bottom.\

Before I get grinding, filing, sanding ect the edge I'm looking for some suggestions, especially how far back into the skin to make this bevel. The top skin looks like it goes back maybe 1/16th to an 1/8th of an inch, but the above picture looks like you should do it a half inch or so...

Thanks

Or - as you have QB wings you are only talking about the bottom skin, you can just rivet it on as is an skip this.

Carl

Scarf joint

That's the scarf joint. Usually both skins are done so the stack is the thickness of one sheet after. File the top corner of one and the bottom corner of the other. File just a little wider than the overlap.
I clamped mine to the bench. Wrap the end and handle of a vixen file the finished thickness you want. It's an old bakers trick. They use a band on the ends of the rolling pin so the dough ends up uniform. Same idea with the file.
Slide the file across an eqal number of passes. Mine was 20 passes. Check the thickness. Better to err on the thick side. Finish it off with scotchbrite to get to the final thickness and to remove the file marks.

I'll try to find a picture of it and post it, but I didn't do this.

I tried to figure out how to do a nice tapered "scarf" joint on a spare piece of aluminium but it always came out ugly. Over done, underdone.. not even..etc.

I'm sure there is a clean and easy way to do it but I wasn't able to so I just didn't do it.

Honestly, it looks fine without it.

I made mine the size of the overlap (I forget what that is right now). To make the scarf joint, I marked the 45 degree line and then taped a piece of stainless about a 1/4" behind it. I supported the corner on some wood and then used a draw file. Rest the file on the stainless and draw with pressure toward the corner. The idea is to not file the stainless but use it as a guide. As the corner point begins to get sharp, you'll see where the scarf is approaching the marked line and you can adjust the stainless appropriately. It's fiddly work but if you don't use too much pressure it should come out nicely and the aluminum is soft enough that a single scarf should take about 10 minutes or so. Clean the filed scarf to remove any particles from the file and prime before assembly because the cladding is gone. Before riveting, give each scarfed corner a slight bend toward the overlapping sheet (like breaking an edge for a lap joint), to keep the joint tight.

So the overlap is about 2 inches or so... therefore since it's not ultra crucial I decided to just do a transition on the top piece and bevel it a bit so it doesn't snag on your hand as you run it across. Thanks!