Europa #435 G-RODO Build Journal - 2017 09

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1 Make TIFFs of aileron pictures and import to CADintosh files. Add lines and dimensions to confirm angles, and distances of weights from hinge lines, then print out.
2 Show dimensioned pictures of ailerons to Ivan Shaw & Andy Draper at LAA Rally. Both agree that sanding off a little paint will be the right thing to do. The ailerons are 1535mm long and the underside chord from the hinge line is between 170mm & 185mm. If I work on a strip about 50mm wide at the TE I will need to remove 43.2g of paint from the port aileron and 84g of paint from the starboard aileron to negate the present out-of-balance moments - half that weight on each face. If I work on the whole area aft of the hinge line, will need to remove about 37g from the port aileron and about 72g from the starboard aileron, which sounds a better proposition as a much thinner layer will need to be removed over that larger area. Will need to discuss the best procedure and abrasives with Ryan.
11 Unwrap and weigh port flap: 4720g - an increase of 1305g from the 3415g of the bare flap before filling & painting. Likewise starboard flap: 4975g - an increase of 1480g from 3495g. Phone Ryan and he says that gel-coat would certainly have added much more weight. For balancing the ailerons, he recommends wet-flatting with 800 grade wet-and-dry paper attached to a soft-faced support such as a cork block. If that isn't taking it off fast enough, could go to 400 grade. Once the weight is correct, re-finish with progressively finer grades until satisfied. 2901.7
16 Take out packs of 800, 600 & 400 grit wet-and-dry paper from store. Looking at those 3 grades, I think that 400 will be needed to remove any significant amount of paint. Find the full-sheet sanding blocks soft-faced with blue foam and remove the 180 grit sheet from one of them. Staple a sheet of 400 grit paper to it. As Dorothy's car is parked outside the carport while we wait for the opener mechanism to be repaired, decide to work in the carport area. Get a piece of carpet out of the trailer and cut off a piece large enough to cover the old garden trestle table. Take out the starboard aileron and clamp it upside-down to the table by the horns, with a flap of carpet folded over as softening. Lubricate paper and aileron with a mixture of water and washing-up liquid and rub all over undersurface, keeping clear of hinge areas. The block oversails the TE, but keep main pressure near the LE so as not to cut through TE paint too quickly. Rinse off regularly to stop the sanding block sticking to the aileron. After a few minutes small creamy-yellowish patches appear close to the TE at both ends and at just under half-span. That must be an undercoat layer or maybe even the filler, so stop rubbing. Rinse off aileron and dry as thoroughly as possible with an absorbent cloth. Weigh it again - 3160g - so only 5g paint removed. Look for a small cork sanding block so I can keep clear of the TE, but can't find it. Instead, wrap a sheet of 400 grit paper around a small block of white expanded-polystyrene foam. Set up aileron again for rubbing down. Rub for a longer time with the polystyrene block, keeping mostly away from the edges and rinsing regularly. A larger creamy-yellow patch appears near the inboard horn at about 2/3 chord, so stop rubbing again. This is beginning to resemble the saga of the rudder! Rinse off and dry as before. Weigh again - now 3150g so a total of 15g paint has been removed. That's less than half the 36g that I need to remove from each face to get it into balance, and painting to cover the exposed patches will add weight again. Thus I'll need to remove much more weight before repainting can be done. Somewhat dispirited, stop and put everything away. I need to talk to Ryan again as I think the ailerons will really need to be rubbed right back to the filler and re-painted. 2904.2
18 Phone Ryan and report how little weight has been removed before the layer below the white paint started to show. He believes that he did not add all of the 600g+ increase as paint and that some of the weight must be filler. He is happy that I've only worked on the underside and would like to have a look at it and rub it down more before re-painting. However, I don't want to take up any more of his expensive time than necessary, so I suggest that I take it back to the glass myself before handing back to him. He thinks he would not put on more than about 160g - 200g of paint on one side so I will aim to get both ailerons 200g below the target finished weight before I take them to him. (Rounding up for safety, my target will be 3165 - 80 - 200 = 2885g for the starboard one and 3105 - 45 - 200 = 2860g for the port one.) He recommends using the DA sander dry with 400 grit and a soft backing pad.

Do some online research for a stockist of car body finishing supplies. There are plenty of online suppliers but the nearest physical shop seems to be Middleton Panels & Paint in Gloucester. Phone to check what grades of DA sander discs they stock then drive over and buy some 150mm 400 & 240 grit discs with Velcro-style backing, and a soft interface pad. They also have a hand sanding block that will take the 150mm discs so get one of those too.

Wheel the compressor over to the carport. Bring out, set up and clamp the starboard aileron on the old garden table with carpet softening as before. Put the soft interface and a 240 grit disc on the DA sander and start sanding the aileron underside. After a few minutes of that, not much seems to have come off - the cream patches have not enlarged noticeably. Decide to try something more drastic and start rubbing with the fine side of the small Perma-Grit block. That is certainly producing more sanding dust than the DA sander, but does not seem to be getting through the paint layer very fast. Turn the Perma-Grit block over and try with the coarse side. That is much better, but is pretty hard work. A few more small cream patches have appeared but still the original ones are only enlarging quite slowly. Next get out the belt sander and fit a 120 grit belt. Running it at the lowest speed and just moving it around on the surface with no downward pressure seems to produce much more sanding dust than any other method so far. The cream patches enlarge only slowly and it seems quite controllable. One patch eventually goes through to the greenish-blue tinge of the bare glass-fibre, so take care to keep clear of that. Stop when 2 or 3 areas are getting through the filler layer. Vacuum off the dust as well as possible. To save having to run to and fro the garage for weighing, put a screw-hook in one of the carport cross-beams to support the digital scale and weigh the aileron - 3090g. At least I am now getting a significant amount of weight off, but it's only about a quarter-way towards my target.

Getting dark and starting to rain. Pull the table well under the carport and leave everything in place overnight.

Noting the thickness of filler that Ryan has left on the aileron underside, I feel I will need to check if the aileron LE will still clear the wing TE when fitted. That might need rubbing down to minimal filler thickness too. And the same check needs to be done on the flap LE too.
25 Have had neither much time nor inclination to return to the aileron work for the past week - feeling somewhat depressed by the prospect of all that sanding. Defunct carport door opener mechanism replaced today so Dorothy wants to get her car back under cover. Move the flaps from the temporary work-table in the garage to the trailer, poking them into the cockpit with some bubble-wrap to protect them. Move the aileron that I was working on back into the garage and leave on the temporary work-table. Bring the compressor and all the tools back into the garage and put Dorothy's car into the carport.

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