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Europa #435 G-RODO Build Journal - 2018 08

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4 Go over upper surface of starboard aileron with the big soft sanding drum in the cordless drill until most of the scratches from the belt sander and the remaining whitish patches are removed. Rub down again with 120 grit 150mm circular sheet on hand pad. Repeat with hand-held 400 grit paper. Flat underside with 400 grit paper. Attempt to weigh it but the cells in the digital suspension scale are flat. One has leaked and corroded a terminal. Clean it up and reinstate contact profile with a blob of solder. Starboard aileron weighs 2665g which is 20g under the target so that is great.

Go back to port aileron again; sand off some whitish patches with the drum sander and the 120 grit pad, then smooth off with 400 grit. That now weighs 2685g which is 25g over the target.

Agree with Dorothy that if I can't get the aircraft ready to fly by the middle of next year (30 Jun 2019 to be exact) I must abandon the project. That is also her deadline for starting to move house to a quieter location, because she can't stand the road noise here. The financial and room letting work at the Quaker Meeting is starting to tail off a bit, so more time will be available soon for aeroplane work.		 2923.9
7 Work on port aileron upper surface again with 120 grit on soft pad, trying to remove all remaining areas of filler and paint. Smooth down with 400 grit. Vacuum up dust. Repeat on underside Weigh it - 2675g; now only 15g over the target, but I can't see how any more can be removed without damage to the glass. I have removed a total of 430g of paint & filler, leaving the aileron only 195g heavier than it was before filling and painting. Hard to believe that the remaining paint on the relatively small area of the LE & horns weighs so much.

Suspend it on fishing line by the hinges. Set it horizontal spanwise by projecting a laser line onto it with the Quigo level. Move level round to point at the root and photograph it for later measurement of angle if required. Place the cylindrical lead weight about mid-way between the horns and adjust its position until the line marked on the root is horizontal. Carefully place rules adjacent to the weight and photograph. Carefully draw around the weight while holding it in place. Remove the weight and measure to the centre of the marked circle from the LE flange - 72.5mm. Re-check weight of lead cylinder - still 366g.

So the moment of the lead about the hinge line to get the aileron horizontal is 0.026535 metre-kg. If 200g of paint is applied to each face (400g total), at a mean distance from the LE flange of 88.75mm, that will give a moment about the hinge of 0.0355 metre-kg - which is too much! The maximum weight of paint that can be applied to leave the port aileron in balance is 299g (~150g each face).

Repeat the process for the starboard aileron, producing a distance of the weight from the LE flange of 85.5mm, for a moment of 0.031293 metre-kg. Thus the maximum weight of paint that can be applied to leave the starboard aileron in balance is 352g (~176g each face). I have removed a total of 500g of paint & filler, leaving the starboard aileron only 170g heavier than it was before filling and painting. Like the port one, almost all that extra weight is on the LE & horns of the starboard aileron.		 2925.7
9 Put ailerons aside for now and start work on the port anti-servo trim tab. The underside is slightly glossy so the mix for that must have been a bit wet. Decide that it will be easier to sand off the Flettner strips and fit new ones afterwards than to attempt to maintain their (very soft) profile while taking down the filler. It should be possible to get a good finish on the balsa TE strips before bonding them on to replace ones I will grind off. Work on the port tab undersurface with the belt sander and a 40 grit belt until greyish patches start to show. Change to 120 grit on soft hand pad and smooth out most of the scratches. Carefully work on the area around the link-rod peg with Perma-Grit files. 2926.3
11 Continue work on port tab. Work around LE with TC files and triangular palm sander & 120 grit. Take off most of the filler from the upper surface with the belt sander. Smooth out scratches with palm sander. Work a bit more with the palm sander, removing further scratches. Smooth off with 400 grit on soft pad and freehand around LE.

Set port tab aside and start on starboard tab. As before, work on underside with belt sander, palm sander & soft pad until most of filler removed. Work around link-rod pin and LE with TC files, Perma-Grit block and palm sander. Repeat on upper surface. Rub down all over with 120 grit on soft pad and then 400 grit.		 2929.3
13 Look up and print out various bits of advice from Matronics forum about using Cabosil (colloidal silica) and filling generally.

Weigh starboard trim tab: 630g. Weigh port trim tab: 650g. Put them away.

Open up the trailer and from the pile of blue foam stored in the engine box take out all the tailplane support pieces I can find, which is only 6 halves - there should be 8. Shine a torch up towards the front of the trailer and can't see any more large pieces of blue foam up there. Shouldn't be a problem anyway as the tailplane are symmetrical. Take the 6 pieces in to the garage. There are 4 starboard pieces which match up at the mid-chord joints, but the 2 port pieces do not match each other.

Spend some time clearing up and tidying away the sanding equipment from the temporary work table. Remove and discard the polyethylene sheet covering as it is getting pretty distressed, and replace it with a double layer of some fresh sheet. Put a pair of starboard foam supports on the table and lay the starboard tailplane on them.		 2931.3
14 The filling advice from Martin Tuck suggested fishing line of 100lb breaking strain, about 0.020" diameter, as a guide for the depth of filler. Other had suggested strimmer line. Hadn't checked what size of fishing line I have in stock, but just in case, while out in town this morning get some strimmer line. The thinnest available is 1.4mm / 0.060" so that may be rather too thick. Find that I actually have in stock some 80lb line which is 0.98mm diameter and sounds perfect. Now I need to figure out how to attach some weights to it.
15 Weigh starboard tailplane - 4260g.

Set blue foam tailplane supports so the span is aligned with the length of the table. Try attaching one of the cylindrical lead weights to the 80lb 0.98mm nylon line with a noose and a loop. It stays in place OK when hanging but springs off quite readily when not in tension. That should be OK, and it may take a set once it has been hanging under load for a while. Wonder if I should trim back the foam clear of the TE so the line hangs vertically, but a trial shows that the line will not bend that sharply, to leaving the foam oversize is fine. Seems a good idea to re-glue the 2 halves of the blue foam together again. Mix a full syringe of the cheap 5-minute epoxy and apply it all along the joint face of the starboard lower foam blocks. Push them firmly into contact and leave flat on the table to cure.		 2932.1
20 Try to drill lengthwise through one of the cylindrical lead weights with a long series 3mm drill bit but, despite trying to be careful, it seizes up and breaks. Try again with 8mm bit and that is successful. Drill through 3 more cylindrical lead weights. Try threading a loop of the 0.98mm, 80lb nylon line through it and that is fine, including the knot. A smaller hole would have been too tight. 2932.7
21 Check max length needed for nylon line, including noose and loop. Cut to length, make noose, and loop through 2nd lead weight. Check how the line hangs over the root end of the starboard tailplane - all looks fine. Make a second length of nylon line into a similar length and attach the remaining 2 lead weights. Get out the plasterer's trowel and check how it bridges the lines - seems fine with no evidence of bending or dipping between the lines. Lay the blue foam support and the starboard tailplane aside. Put the other pair of blue foam starboard tailplane supports on the work table. Mix up a full syringe of the el-cheapo 5-minute epoxy and apply it to the joint face. Lay the 2 halves flat on the table and push them together into alignment. Leave to cure. 2933.4
23 Send an e-mail to Ryan asking about the possibilities for re-painting the ailerons.
25 No response yet from Ryan so send him a text asking if he got the e-mail message.

The halves of the second blue foam support are now well bonded. Check how the starboard tailplane sits on it; LE projects well beyond the edge of the foam - it has obviously been cut back previously. Set that foam support aside and try the tailplane on the first support. The foam is proud of the LE so get out the hot-wire cutter and cut about 25mm off the front edge of the support to allow the fishing lines to drop vertically from the tailplane LE.

Lay the starboard tailplane on the foam support and start to scuff-sand the upper surface with the tungsten carbide sanding plate on the oscillating tool. Don't get very far with it before it stops because of low battery, so put it on charge and switch to manual methods. With Perma-Grit short block and coarse flexible sheet, rub off a slight bib along the root where resin has apparently crept under the edge of the peel-ply while doing the closeout. Rub all over with the coarse side of the block, then go over the low spots, the tip radius and some glossy areas where the peel-ply seems not to have adhered well to the layup. Vacuum off the dust. Take the foam out of the way to avoid melting it and wipe tailplane over with an acetone-soaked rag to degrease it. Replace it on the foam support and blow clean with the air line. Place one nylon line close to the root edge and the second one parallel to the chord line, with the spacing at the TE still within the width of the plasterer's trowel.

Check and print out the logs of several of the previous filling operations for reference. Amend for Ampreg 21 3:1 weight ratio the 1-cup balance placard and tape it to the base of the balance in place of the original one. Remove one of the 5 M10 nuts and store it for possible future use

Find a couple of washing-up liquid squeezy bottles and clean them out with water, then rinse out again with a little acetone and blow dry with the air line. Mark them up for dispensing Ampreg 21: blue top, resin; green top, hardener. Open the Ampreg 21 supply containers and carefully decant from each into each dispenser bottle until nearly full. All of the hardener goes in, but there is plenty of resin left in the main canister. The new dispenser bottles are just too tall to fit in the heated resin cupboard so they have to lean against the resin canister.

It's now getting a bit late in the day to be sure of comfortably completing the filling operation today, so stop.		 2936.2
28 18.5C, 38% RH so turn on fan heater at thermostat setting 3. Unsure of how likely the Ampreg 21 is to exotherm, decide to mix the big batches needed for filling in a larger container with more bottom area, and find a 1-litre Mackies ice cream tub that looks suitable. I thought I had a container of Expancel to dispense from but can't find it, so get another plastic tub from stock, label it and fill with Expancel. Find that in addition to the buckets of it I recently bought, I have a small can of Cabosil that I now remember getting from Martin Carolan.

At 14:20, it is 20.4C, 37% RH. Mix a peg-10 (128g) batch of Ampreg 21 and paint the upper surface of the starboard tailplane with it. To the remainder add 6 doses (each a well-loaded mixing stick) of Expancel and stir in. Add 2 doses of Cabosil (it flows off the stick so easily, the mixing stick only holds about half as much Cabosil as Expancel) to give a 6:1 ratio by volume of Expancel to Cabosil. Not dry enough yet so add 3 more doses Expancel & 1 Cabosil. Mix then add 1 more dose Expancel.

Hang the weighted fishing lines chordwise across the tailplane, one at the root and the 2nd one about 75mm outboard from that. Spread the filler between the lines with a filling knife. Once the are between the lines is well covered, run the short edge of the plasterers' trowel along the lines and the result is immediately impressive - a smooth surface with no tendency to roll up. Tidy up some low areas and repeat trowel passes until satisfied with the overall result.

Lift the line from the root and re-position it about 75mm inboard of the second one. Smooth out the slot left by the line using the corner of the filling knife. Spread filler between the lines and smooth again with the edge of the trowel. Move the inboard line again, smooth the slot and fill a third area before the filler runs out. 15:30, 23.0C, 34% RH; pause for refreshment.

Restart at 16:05, 22.7C, 34% RH. Mix a peg-10 (128g) batch of Ampreg 21 and add 15 doses of Expancel and 5 doses of Cabosil. Move inboard line to just beyond tailplane outboard rib so as to cover the slight depression there in one go. This makes the space between the lines at the aft end requires the use of the long edge of the trowel. That works OK, so on next line move make the spacing just short of the trowel long edge length. That goes fine too, continue with that line spacing.

Lose count of how many batches of epoxy-filler used; either 2 or 3 more to get to the tip of the tailplane at 17:35, 23.4C, 34% RH. Mix a peg-1 (24g) batch of Ampreg 21 in one of the usual 500ml SP Systems cups and add 3 doses Expancel and 1 dose Cabosil. Spread it onto upper half of the tip freehand with the filling knife, finishing at 18:15 with 23.6C, 34% RH. Leave fan heater running.

At about 20:00 check on curing; most of the filler is getting to the leathery stage, but the section at the root is quite well cured. Briefly try Graham Singleton's suggestion of removing the top layer of filler there with a small wood plane and my Stanley block plane works quite nicely.

At about 23:10 the filler on the tip is still just slightly off full hard cure; 22C, 34% RH; turn off fan heater.		 2940.5
29 Use the Stanley 102 block plane on the starboard tailplane upper surface filling for a while, then switch to the Stanley RB10, considering that it is easier to replace its blades than to re-sharpen the one in the block plane. That works well and is easier to use with 2 hands, although the tailplane and its foam support tend to move around a bit more. 2940.8
30 Swap the blue foam support blocks so the underside of the starboard tailplane can be worked on. Clean as much filler as possible off the nylon lines; must remember to do that before it cures next time!

The pip-pin hole on the upper surface is is completely blocked by filler; should have plugged it in some way to prevent that. Drill through from the underside pip-pin hole with a 5mm long-series bit to find where the hole on the upper surface is. Open the hole in the filler a bit with a hand countersink, then carefully use bits in the hand brace from 10mm to 12.5mm in 0.5mm steps to open the hole to the full internal size of the SRBP tube. To plug the underside pip-pin hole (about 7mm ID), spend some time trying to find a suitable item. Eventually settle on a 6mm wooden jointing dowel, wrapped with several turns of insulating tape to be a firm fit. Push it in flush with the surface.

At 13:10 start to rub down the epoxy nibs etc on the underside of the starboard tailplane. At the LE the filler coming round from the upper surface is dragging a bit on the sanding block so try the block plane and it works much more easily, with good control and no danger of digging into the underlying layup. Pause for snacks then restart about 14:25. Scuff-sand the underside of the starboard tailplane, first with the Perma-Grit short block, and then with flexible coarse Perma-Grit sheet to get into lower areas. Need to work on quite a few small glossy depressions where there have obviously been air bubbles trapped between the peel-ply and the layup. Finish scuff-sanding at 15:45.

Clean up another 1-litre ice-cream tub for mixing filler. Just out of interest, to check the accuracy of the predicted weights for the 3:1 Ampreg 21 mixes, weigh the tub empty: 28.2g. 21.7C, 33% RH; turn on fan heater with thermostat set to 3. Wipe down the tailplane with acetone-soaked rags to degrease it.

At 16:05 mix a peg-10 (nominally 128g) batch of Ampreg 21. That weighs 151.5g, so the mix itself is 123.3g - not far out. Paint the tailplane with it. To the remaining epoxy add 9 doses of Expancel and 3 doses of Cabosil. Lay one nylon line along the root and the 2nd the length of the plasterer's trowel away from it at the TE, but angled to be parallel to the chord line so closer at the LE. Spread the filler and manage to fully cover that area by repeated passes of the trowel. Move the inboard line, this time cleaning it of filler before replacing it a trowel-length further outboard.

At 16:50 (27.8C, 31% RH) mix another peg-10 (180g) batch of Ampreg 21. Add 15 doses Expancel and 5 doses Cabosil. That covers 2 more strips each the width of the long edge of the trowel.

At 17:30 mix another peg-10 (180g) batch of Ampreg 21. Add 15 doses Expancel and 5 doses Cabosil. That does not quite cover the remaining 2 more strips to the tip.

At 18:10 mix a peg-2 (36g) batch of Ampreg 21. Add 4.5 doses Expancel and 1.5 doses Cabosil. That easily covers the remainder of the last strip and the tip itself.

Stop at 18:45 (23.3, 30% RH) and leave the fan heater running.

At 23:30, 21.4C, 30% RH, filler at tip well on the way to curing, so turn off fan heater.		 2946.9
31 Do a bit of shaving of the filler on the starboard tailplane with the RB10 plane, removing some high spots and ridges.

Carefully drill through the pip-pin hole from the upper side with a long 5mm drill bit to reveal the position of the hole on the underside. From the underside, drill slowly with 5.5mm, 6mm & 6.5mm bits until the wooden dowel is completely gone and the insulating tape pulls out. The bore is now clean and smooth and accepts the shank of a 7.5mm drill bit.

Take the mismatched halves of the port blue foam tailplane support out to the trailer again to make a bit more room in the garage.

Poke through the filler in the tab hinge mounting holes from the inside to clean them out, then finish with a temporary screw driven into each hole until it strips out the remaining filler.

Put away the starboard tailplane and set the port one on the foam support. Need to find something about 12mm diameter to plug the pip-pin hole in the upper surface.		 2947.7
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