Europa #435 G-RODO Build Journal - 2007 11

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1 Start to sort through wood for pieces suitable as a start for the wing support jig. Replacement OR5 arrives, but it too is somewhat scratched with tramlines going across it, although not so deep as the one I sent back. Phone John at factory to report it and say I will try to polish them out but if not successful will return the part. Rub it down with 240 wet-&-dry on the small aluminium block, lubricated with 3-in-1 oil. Scratches disappear after a reasonably short time. Give the other side a rub too, then switch to 400 grade followed by 600 grade. Try out some pieces of mahogany under the wing adjacent to the flap brackets. After much fiddling about decide it's not worth the hassle of getting the wing high enough to get the flap hinges clear of the table. A single piece of mahogany about 48mm thick at the edge of the table just in front of the flap brackets, with a wedge under the root rib LE, provides a stable working situation. There will not be a serious download on the moving surfaces, so the lightweight clamping arrangements already set up should be OK. I can set up an extra support at the wing tip to prevent droop while curing. 823.2
2 Clear up working space around table and at wing tip. Bandsaw up pieces of 9mm MDF to fit around centre flap hinge & clamp it in the retracted position. Try LE profile to see if that could provide a bungee anchor - no, it just pulls around the LE curve. Instead, how about trapping a sheet of something under LE with holes or uprights for the bungees to hook onto? Simplest turns out to be best - find that bungees will hook onto edge of a piece of 4mm ply slipped under the LE. Clear out all the stuff that's been left in the wing during flap-aileron fitting. Put skin into position and check for fit. Remove a small fillet of my BID doubler at TE tip to get proper seating. Trim the skin at the flap-aileron junction so that the wider part clears the flap. Put the square steel tubes in position on spar and find some pieces of ply and chipboard to span between the tubes and carry the weights. Estimate weight of lead in picture in manual (fig 31, page 9M-21). Scale dimensions to get approximate size of lead weights (about 90mm x 90mm x 50mm); density of lead (11.3gm/cc) gives weight of each as about 4.5kg. Not all of the wing is visible in the picture, but extrapolation from what is shown suggests that there are about 23 weights in total, giving a total weight of about 100kg. This is a very happy match to the 5 bags of sand I bought way back in July 2003, which are about 20kg each. 826.1
3 Shovel out sand from the 20kg bags it came in to zip-lock bags. Each small bag holds about 4.4kg and the sand fills 23 of them. Move them into the garage.
12 Check position of wing skin and drill 1/8" holes for clecos, one into root rib flange and one into tip moulding. Chamfer lower leading edge of skin all along for good fit. Position skin, hold with clecos and apply masking tape along LE joint line to spar to act as a hinge. Unclamp flap; tape vinyl strips to flap & aileron to keep them aligned with wing TE. Fold back wing skin and mark for rib positions. Attach polyethylene sheet to each side of internal ribs to catch any Redux drips. Remove aileron temporarily to allow taping a piece of vinyl inside top of inboard horn box where there is a slight gap between it and TE. Tape polyethylene sheet to underside of skin at all internal rib and horn box locations to act as release film. Leave skin folded down into proper position to avoid strain on tape hinge while considering if there's anything else needed to do before the pre-bonding exercise. 829.5
13 Switch on fan heaters to thermostat setting 4. Check Redux use instructions again, noting particularly advised degrease-abrade-degrease process. Put adjustable stand under wing tip. Find suitable piece of wood and bandsaw to approximately-correct wedge shape to support tip. Mark tip underside profile onto wood using M10 washer on felt-tip pen as profile follower. Bandsaw to marked line. Position on stand and adjust height to take the weight of the tip. Add polyethylene drip protection around horn boxes and between double rib - forgot that yesterday. Wipe down all bonding surfaces with acetone-soaked paper towel. Abrade them all thoroughly with 80-grit sandpaper and again wipe off with acetone-soaked paper towel, making sure not to transfer dust lifted onto next surface. Open one of the new packs of Redux (Araldite 420) and mix up 120g + 48g in a 1-pint plastic bowl. Very noticeably smoother and thinner than the test mix I did on the expired stuff. Add 3 and a half doses of flox (1 dose = amount that can be lifted on a mixing stick) to get it thick enough to be non-runny. Spread onto tops of internal ribs and horn boxes. Quantity turns out to be almost perfect - certainly none left over. Lower skin into position and press on by hand. Raise again and check if touching everywhere. Move some obvious excess to a few thin places. Close, fit clecos, place square steel tubes and tape down, lay wood across and load up with sandbags plus a few bits of lead near root. Work completed around 16:00, temperature up to 20C, humidity down to 49%. Leave heaters running. 832.4
14 Remove weights, wooden spreaders & untape square tubes. Open skin and find good contact all over outer horn box and outboard rib, but intermittent elsewhere. Start to peel off release sheets from skin then realise they should stay for another try to build up all the low spots before final closure. While sawing at a protruding flange of Redux with a knife, the vibration disturbs the pile of sandbags and several fall off the table, splitting open. Move the rest to the floor, tidy up and re-bag most of split sand, vacuum up remainder. Re-apply release sheets to skin underside. Wipe all Redux surfaces with acetone-soaked paper towel and abrade them all. Hard work as most are pretty uneven and need work with curved and vee-shaped Perma-Grit files. Will know next time to put much more Redux on at pre-bond to ensure complete filling of space between ribs and skin. Turn heater thermostats down to 2.5 overnight. 836.5
15 Turn heaters back up to 4.5 again. Brush sanding debris off skin and bonding areas. Wipe down bonding areas with acetone-soaked paper towel. Start to mix 120g + 48g Redux but realise too late that the larger (& heavier) bowl used today brings the total mass above the 200g limit of the scales. Reluctantly chuck out that mix, clean bowl with acetone and start again with 100g + 40g. Add 3.5 doses of flox and spread on ribs - does about half of them. Mix another 100g + 40g + 3.5 doses flox and do the rest. Lower skin to check contact and add a few dollops in the couple of small areas not making contact. Lower the skin, fit clecos, tape on tubes, add wood and sandbag/lead weights. At 23:30, up to 24C, 27% RH. Send e-mail to Tim Ward re aluminium fuel filler fitting. 839.0
16 Take weights, wood & tubes off wing and remove clecos. Try to lift skin but it's stuck quite firmly at root. With a bit more careful leverage it eventually opens. One piece of the polyethylene sheet at the root end had folded back on itself when I closed up after the first opening to check contact areas. (I had spotted 2 other pieces which were tending to flop because of the weight of Redux stuck to them, but hadn't seen what happened at the root.) This caused the polyethylene sheet to be trapped in the Redux at the fold, and small areas of the skin to be exposed to the Redux on the ribs. Fortunately these areas didn't bond really well as they were still in the glossy as-cured state and hadn't been de-greased. The ripples where the polyethylene sheet was doubled up are small and will be easy to deal with at final bond. Remove release film from skin and masking sheet from around horn boxes and ribs. File and break off all surplus Redux that was squeezed sideways - scoring along the line of the edge of the rib flange with a knife and bending with water-pump pliers is the quickest way to remove big lumps. Notice that the layer of Redux is much thicker on inner ribs than on the outer one. Clearly if the top skin bonding was done all in one operation without checking how much space needed to be filled, there would either be a lot of Redux wasted or a strong possibility of some ribs not being bonded at all. Degrease all bonding areas on both skin and ribs etc with acetone-soaked paper towel. Abrade all mating surfaces on skin, spar, TE, ribs & horn-boxes. Start with 80-grit sandpaper but change to fine Perma-Grit sheet as the sandpaper is wearing out too fast. Remove everything from inside wing and vacuum throughout. Check again that nothing is left inside the wing. Degrease all mating surfaces again. Mix 117g + 47g Redux (should have been 100g + 40g but over-poured hardener & had to add some resin) and add 3 doses flox. Spread onto mating surfaces, starting at root end. That is enough to take it about half-way along. Mix 100g + 40g + 3 doses flox and spread that on. That pretty much covers all the rest. Review coverage at root and retrieve some drips and thick spots to make coverage more even near tip. Lower skin temporarily and press by hand to check contact areas. Lift and check - almost perfect, just a couple of small areas need some moved to them from areas that appear over-thick. Close again, fit clecos, clamps at root rib flange, square tubes, wood and weights. Decide to shorten outboard rear tube so as not to oversail the tip moulding and thus get more even pressure along the outboard end of the TE. Also add extra support using another stand and wooden batten under aileron LE to improve the clamping action all along the aileron. 847.7
17 Send cheque to Tim Ward for aluminium fuel filler pipe. 25C, 31% RH in working area. All visible Redux has cured hard so remove weights, wood, tubes, clecos. A ridge of Redux has been squeezed out along the spar under the masking-tape hinge. Try wrapping vinyl around ends of short Perma-Grit block to allow filing it down without scratching adjacent skin. Seems to work in principle. 848.3
19 Order 100ml & 50ml dispenser bottle along with Wilma's stuff from Fibrecrafts, to help dispense hardener, etc more precisely.
20 Bottles delivered.
22 Clean resin pump spouts and do a few short strokes to ensure correct flow. Do a calibration run, measuring weight of resin & hardener separately at each stroke over an accumulated total of 8 strokes. Mix the resultant batch, transferring between cups several times to get as good mixing as possible. Cut off a strip of BID and cut it into 11 squares. Lay them up, alternately at 45 degrees, onto the side of a rectangular polyethylene bucket (the nearest handy flattish surface that will release from the resin), using up most of the resin mix. Try, not very successfully because of the flexibility of the bucket, to scrape off the excess with a card squeegee, and apply peel-ply. Check calibration results on the spreadsheet. Weights of individual strokes tend to be slightly resin-heavy (original setup was for slight excess of hardener) but all except one are within the box that assures 99% of properties are achieved, so that's quite reassuring.
23 The Redux has had its recommended 7 days at 25C, so turn off the fan heaters. Remove the test layup from the side of the bucket. Saw some strips off it and try breaking them. That seems to be slightly easier than I'd hoped. For comparison, break a couple of pieces off the old 6-ply BID test piece. At 45 degrees to the fibres (which were all aligned in that piece) it seems harder to break, and the break is cleaner. The breaks in the current sample show significant whitening away from the break line, where resin & fibres are separating. Maybe it's because of the different ply orientation, maybe it's because I didn't squeegee enough of the excess resin away from the layup, or maybe the resin is too old. Not entirely happy with continuing to use this older resin, so order 2 off 3.75kg packs of Ampreg 20, and 250mm x 100m peel-ply from Marineware.
24 Start to think about storing this wing properly in the trailer. Look up the pictures I took of Peter Davis' trailer at Kidlington. Doesn't seem to be really enough detail of the wing fittings. Maybe I need to visit Peter again and see the wing actually clamped in the fittings?
26 Try to pull out vinyl spacers between wing TE and control surfaces - they won't budge. Remove aileron and find vinyl can be pulled off with some effort, because the Redux has adhered to it surprisingly well. Remove flap and peel off vinyl there. As it's not really re-usable, with much Redux stuck to it, check thickness of vinyl for next time (1.36mm) before chucking out. Find that a small chisel used with the bevel face down is quite good for removing much of the excess resin along the spar line. The chisel can get under where it has flowed onto the smooth skin surface each side of the joint line and break the weak bond there. However, the chisel overshoots at one point and lifts an approximately 10mm triangular flap of the rear skin, just one glass layer. Turn heaters on again, put parcel tape around the damaged area, mix 1 stroke of resin and work it underneath the flap of skin. Apply peel ply. Weigh down with several lead weights, supported on a small piece of wood with vinyl underneath to help conform the curve. Remove wedges under wing and re-insert original support blocks. Remove aileron bellcrank access panel. Find some 10-32 x 3/8" pan head screws to use instead of the 1/2" screws AN525-10R8, to prevent wearing out stiffnuts on next assembly (should have done that in the first place!). Insert transverse pushrod into wing and check that the access hole allows the outboard end to be lined up with the rod end on the bellcrank. Wilma is drafted in to turn the inboard end while I guide the outboard threaded end into the rod-end - success first try! Fit aileron pushrod and re-fit aileron. Check travel - severely restricted in up direction by the top skin. Sketch it out in CADintosh and that shows about 12mm needs to be taken off the skin, which will bring it pretty much back into line with the original TE. Mark and cut off a 10mm strip using a fine hacksaw blade in a pad handle. Rub down with long Perma-Grit block and chamfer under edge. Re-fit aileron and note where it is rubbing. Also notice that the aileron pushrod adjustment (about 4 threads away from fully home at each end) is such that the bellcrank is hitting the stop about the same time as the aileron is rubbing on the TE. Remove aileron and re-adjust pushrod ends to fully home. Re-fit and confirm that the required 25 degrees up from neutral can be reached OK. Remove aileron and again rub down TE and chamfer it on underside. Re-fit; now much less rubbing - only needs a few high spots cleaned up. 852.8
27 Check resin samples from sticking down skin patch - all seem OK. Some thinnest pieces tend to bend rather than break, but all scratch quite well. Turn off heaters. Check aileron fit at full up and mark tight spots on TE. Remove aileron and rub down TE with coarse Perma-Grit blocks, using long one to straighten it up after working on local areas with short one. Chamfer horn box areas at a fairly shallow angle and the rest of it at about 45 degrees. Re-fit aileron and check up travel. Now only slightest brushes against TE as aileron nose hits inside bottom of TE closeout. 853.4
28 Do some internet searching for screws and order a packet of 100-off 10-32 x 3/8" button head socket screws from Tool Fast Direct.
29 Mark the rubbing spots on TE. Remove aileron. File off marked areas with coarse Perma-Grit file, then use long Perma-Grit block to straighten it up again. What I'm thinking is that the aileron should get profiled fairly straight all along, bringing the rest of it up to the height of the horn box reinforcements where it's now tending to rub. Thus the TE should be straight for this reason as well as for appearance, rather than closely following the profile of the unfilled aileron. There is an argument for leaving this TE trimming until the aileron is filled and painted (and there may well be a need for further work then) but the bulk of the removal and re-fitting is probably better done now before the aileron is polished up to avoid blemishes. Chamfer all along TE underside. Re-fit aileron and check clearances. Just about perfect at full up, but slight contact on inboard horn reinforcement at full down. 854.0

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