| day |
notes |
hours |
| 10 |
11C, 93% RH in tailcone. turn on fan heater in rear fuselage to thermostat 3.5. Cut peel-ply tapes 4 off 125mm x 1200mm and 2 off 125mm x 200mm. In less than 15 minutes bulkhead area is up to 31C, 31% RH so back thermostat off to 3. Abrade bonding areas. Clean pump spouts, mix 5 strokes epoxy and wet out 2 plies of BID 1100mm x 100mm. While that soaking in, mix 3 strokes epoxy and add almost 3 doses of flox. Butter it into the corner all round sides of fuselage rear bulkhead. Rather a lot left over - 2 strokes would have been enough. Trim polyethylene sheet to edge of BID and lay onto front of bulkhead, starting at bottom centre. Leave one half of BID tape draped (epoxy side up!) forward along fuselage floor while working the other half into position all the way up around the bulkhead. The centre line along the length of the polyethylene sheet is very useful in ensuring the tape is well-placed, but of course the polyethylene sheet does not conform well to the complex shape. Surprised to find the tape is only just long enough. Peel off polyethylene sheet and then work 2nd side into position, Peel off polyethylene sheet completely and use both fingers and brush to work out ripples in BID then stipple BID fully onto bonding areas. Repeat whole process for rear of bulkhead. Lay torque-tube reinforcing tapes onto polyethylene sheet and wet out with about 2.2 strokes of epoxy. While soaking in, start to apply peel-ply to rear of bulkhead. One strip goes around fuselage without too much difficulty but need lots of small pieces to cover bulkhead edge shape. Would have been better to lay up rear side first as front side is starting to gel and won't be so amenable to peel-ply. Lay on torque-tube reinforcements, remove polyethylene sheet from them and stipple into place. Finish off peel-ply as well as possible, given the compound shapes and state of cure of the epoxy. Replace polyethylene sheet tent over tailcone and put temperature and humidity gauge behind bulkhead, facing aft for easy reading without removing tent. 24C, 50% RH. |
1365.0 |
| 11 |
32C, 22% RH. Layups well cured. Turn off fan heater. |
|
| 26 |
Check epoxy samples for full cure. Remove peel-ply. Trim edges of layups with hacksaw blade, Minitool jigsaw with diamond blade (which breaks just as I finish) and Perma-Grit files. Bore torque tube holes with 2"/51mm grit-edged holesaw, following the re-aligned centre holes. Get torque tube down from garage ceiling hooks and TP10 nylon bushes from Box 12 in spare bedroom. Post a query about retention methods for TP9/TP10 on Matronics e-mail list. Dismantle the torque tube, marking all parts P & S, and the torque tube for forward/aft (it is already marked P & S inside the ends). Note that the TP11 bushes tighten up too much to allow removal as they get to the holes in TP12, so deburr the holes very carefully and then TP11s slide off without much effort. Fuselage holes as bored are just too tight for TP11 so work on them lightly all round with Perma-Grit half-round file and they both slip in OK. Assemble torque-tube in-situ. Can't get the temporary bolts fully inserted because they foul the bulkhead; should really shorten them. Centre the torque tube by adjusting the space between the rear ends of TP12 and the fuselage moulding. Measure, using tape hooked into end of torque tube, to cowl joggle at firewall: 3560mm port, 3559 starboard. To the seat-back datum previously marked is 2400 port, 2395 starboard so something is awry. Check that datum again and it is NOT central between the fuselage sides (537 P, 543 S) - don't know how I managed to do that as I had checked and re-positioned it once already! Wipe off old mark and put on a new one 540mm from each side of fuselage. Measure to torque-tube tips again: 2390 P, 2385 S so no real change! Double-check the datum as I'm beginning to doubt my ability to read numbers - check to the cowl joggle again taking care to get the tape tension as equal as possible and using a straight-edge against the joggle to eliminate parallax errors. This time 3559 P, 3557 S. Scribe arcs on seat-back from each torque tube tip in turn at 2400mm radius. They intersect at about 15mm port of the datum. Check length of torque tube (941mm) and fuselage width at cowl joggle (1045mm). Draw up the geometry in CADintosh, assuming that the firewall is orthogonal to the fuselage centre line and that the torque tube is also centred on the fuselage centre line (not necessarily valid assumptions!). This gives the torque tube as out of true by 0.12 degrees to port (which sounds not too bad). Draw arcs from the tip of the torque tube to represent the measurements made to the seat-back datum. The 2400mm arcs intersect about 5mm port of centreline and the 2385 & 2390 arcs intersect about 7.7mm starboard of the centre-line. The distance between the intersections (12.7mm) is of the same order as the 15mm observed but the different absolute positions in this simulation show that the firewall is probably not perfectly square to the fuselage centre line, or that the fuselage centre line is slightly bent. It wouldn't take much over the distances involved, so I'm not going to get too excited about it. Ian Rickard replies to my posting with a list of known solutions to TP9/TP12 retention. |
1367.3 |
| 28 |
Put a piece of aluminium angle across fuselage at various fore-and-aft stations within cockpit area to check transverse level. Varies between 0.4 & 0.6 degrees port high. The tailplane torque tube measure 0.3 degrees port high, so not too far out! Disassemble the torque tube. Grip each TP10 lightly in vise across faces make 8 shallow diagonal saw cuts around circumference of each. Shorten 2 of the 3/16" UNC bolts to about 2" so they won't foul the bulkhead. Only 2 needed as don't need to assemble TP9 at this stage. File some notches around the edges of the fuselage holes to let adhesive penetrate a bit more around the torque tube bushes. |
1368.2 |
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