Skinning the HS

Sat. 3rd November 6hr 45min

Match drilled the HS-904 ribs and HS-905 nose ribs to the spars. Disassembled. Prepared the spar edges. Fabricated the wooden jig and assembled the skin and skeleton of the left HS.

This was my first full Saturday working on the project. As it turned out, I was also able to find time go into the city centre with my wife to have some lunch and shop for some household items.

In preparation for the project, I would regularly drop into my local Lidl and aldi stores to see what they might have. As a marketing man, I would have told you ten years ago that the idea of a shop that did not have regular stock but instead offered whatever was cheapest from time to time was plain crazy and would never work. Shows you how much I know. In fact, not knowing what they may have increases the 'mystery' and brings me back regularly just to see what they have in. What they have in stock very often includes tools that I would never have thought of owning. Much of it is amazingly cheap stuff probably made in China. However, for very occassional use, it is perfectly fine. I got a router and an electric staple gun that were of great help in building the workshop. All of the plastic storage bins you see in the photos came from this source. I also got a digital level, digital calipers and two engineering-type vices with brackets to attach them to the the side of a bench. These last items really came into play this evening, holding the spars steady while I preped the edges. They will also be used to hold sheet material clamped between two lengths of timber for edge preparation; the rudder skins for example. I will have to see if I can fit them to the table of my bench drill because the vice-grips type clamp I got earlier won't hold thin or small pieces.

Again, the edge preparation technique I am using involves using the file to get a consistent shiny edge with no shear marks, then deburring and finally polishing. I use the bench-mounted Scotchbrite wheel where possible but, if not, I use the 1in wheel in a die grinder. That die grinder sure uses a lot of air.

Main Rib Edge Preparation

Thurs. 1st November 2007 3hr 35min

Filed, deburred and polished the edges of the 10 HS-904 main ribs. Checked and adjusted the flanges for square. Fluted the ribs until straight.

Another evening of relative calm. Harry Hopkins had laid great emphasis on edge preparation in the metalworking course I took with him back in July and I was determined to get it right. I used the magnifying lamp pictured here to ensure that I was getting a good surface.

In the main, it went well but there are two very narrow notches, top and bottom, separating the main part of the flange from a tab that goes under the flange of the forward spar. These lead back to a relief hole on the actual web and they are so narrow that they are very hard to polish. I got a small file in okay but it was nearly impossible to get at them with the scotchbrite wheel. a small sanding wheel on my Dremel might have done it but I was reluctant to try. I felt I was more likely to increase rather than decrease the chances of creating a weak point where a stress tear might begin so I eased off on the filing in this area. I think the best solution would be to use a sheet of fine abrasive paper folded to give me a profile to match the notch.

I found the 1 inch Scotchbrite wheel on the die grinder invaluable for polishing the edges of the lightening holes but I used the big wheel on the bench grinder for all the rest.

Were it not for the novelty of the project as a whole, this process would have become quite boring. My shoulders ached at the end of quite a long session.