Matt's RV-7 Project

Another week has gone by without much of a chance to work on the plane, but the house painting is now finished. Mary is happy, and thus I continue to have a riveting partner. Tonight I dimpled and countersunk the lower parts of the VS spar and spar reinforcement, and deburred all the remaining edges. Ran out of time to clean and spray primer… but I've done quite enough painting lately, so it's somewhat okay.

Now that the HS is finished, it's back to the VS for yours truly. I match-drilled the new spar reinforcement bar to the new VS spar, and then set about cutting out a new set of lightening holes. I discovered that the non-removable pilot drill in my fly cutter had gotten bent somehow, so this time around I decided to try a set of hole cutters from Hougen by way of Cleaveland Tool:

They were outrageously expensive but they do a good job of cutting nice round holes, and give me the willies somewhat less than the fly cutter. The other aspect I failed to realize until after I'd bought them is that the set doesn't include a 1 ¹/₂" cutter, only 1 ³/₈" and 1 ³/₄" ones. Rather than spend yet more money special-ordering the correct cutter size, I decided to just cut the specified 1 ¹/₂" holes ¹/₈" undersize using the next smallest cutter I had. Since the lightening holes are optional anyway, it just means that I have a spar reinforcement bar that's slightly heavier than it needs to be.

Let's see… five 1 ¹/₂" holes that are each undersized by an eighth of an inch, in ¹/₈" thick aluminum… 0.224 in³ of extra material, at 2.643 ^g/_cc… the tail of my airplane will be a third of an ounce heavier than it might otherwise be. Yeah, I think I can live with that.

For the remaining two 2" holes I did have the right sized cutter, so I finished those too and all my lightening holes are now drilled. Deburring will have to wait till tomorrow when I can run the air tools without waking up the neighbors.