Tue Jun 23 2020

Center amr rest lid

Okay, the test layup cured overnight, so today I stripped it out of the vacuum bag.

Peeled off the felt and one, then two layers of peel ply.

Here is the part. Six layers thick and you can kind of still see throug it. Neat.

Initial measurement is .044 thick.

I ran a sanding block over the peel ply surface to knock off the high bits, and measured .042 thick. Since there are six layers, each layer should be .007 thick.

Now that I know the thickness of a layer, I wanted to make sure I knew which type of fabric this appies to. This fabric came in a fiberglass starter kit from Aircraft Spruce at Oshkosh a few years ago. I wasn't sure what fabric they included in the kit, so I went to their website to see if I could identify it. It seems like these fabrics are described by the number of fibers in each bundle. I thought I would use my cheap-o USB microscope to count the fibers in a bundle.

Here we're zoomed in a little more, but it was still not really possible to count the fibers.

It turns out I didn't need to after all. Apparently that starter kit is a normal item for Aircraft Spruce, not an Oshkosh special as I had thought. The list of items in the kit describes this particular BID fabric. Excellent. If I run out, I can just order more of the same and I won't have to worry about redoing the layup test again with a new fabric.

Prior to making the new mold (a male mold this time), I need to know what dimensions it needs to be. So, I need to work out the support arrangement near the aft end of the cover. Here's a sketch of how the cover will be constructed and supported at the aft end. I'll construct these parts and put them in the assembly to measure the length of the mold.

One of the parts I need to fabricate is a piece of angle. I used an old, scrap Z bracket.

Hrm...it seems that when I measured for the length of this Z bracket, I only measured the width of the flap actuator tunnel and forgot to include the thickness of the sheetmetal on either side.

Instead of 2.390 wide, I need to make this piece 2.422 wide.

Fortunately that wasn't my only scrap Z bracket. I fabricated a new angle.

The angle formed by the two (remaining) legs of this Z bracket are quite a close match to the angle of the flap actuator tunnel. Just need to add a chamfer to the longer leg.


Last thing for today was to fabricate a piece of .040 material that also has the matching angle.