||Clamp rudder firmly against side of table with root uppermost. Take off a few obvious high spots with the Sandvik 402 small abrader, 285 grit. Try the flexible sander made back in July 2004. Reasonably easy to use, but is too flexible to remove the orange-peel effect from the overspray. It will only be useful for about 600 and finer grits when we have got beyond profiling and into smoothing. Switch to 88mm x 38mm aluminium block with 240 wet-and-dry, used wet, which gives a much better-looking effect and is easy to use. Result feels good to the touch but shining a spotlight across it after rinsing off shows up plenty of small depressions left. Continue rubbing carefully, using the spotlight to see where work is needed. It's a bit fiddly, so will have to go back to using 3M Dry Guide Coat. Rinse, dry and apply DGC carefully, trying to keep it off the polished side.
||Rub down rudder root with 240 grit wet on 88mm x 38mm block. Find that misting the working area frequently with the water spray gun helps very quickly to see when I've gone far enough on any particular area. While blending towards the polished starboard side it occurs to me that it would probably be best to rub down all surfaces of the part with each grade before moving on a finer one; that would avoid the current problem of having to go slightly into an already-polished area with the coarser grades to ensure full coverage. However, that would require a lot of extra re-configuration of the clamping arrangements, so possibly not worthwhile on the rudder. Worth remembering for other parts, though. Rinse and dry off. A check with the spotlight shows no significant problems left, so DGC is the thing to rely on every time. Apply DGC and rub down wet with 360 wet-and-dry on 88x38 block. Rinse, dry, apply DGC. Rub down wet with 600 grit. Rinse, dry, apply DGC. Rub down wet with 800 grit. A small thin spot appears near the sharp corner at the edge of the hinge vee. Initially it looked like a patch of DGC, but sadly got darker instead of lighter with rubbing. Rinse and dry off; decide to stop there while deciding what to do.
||Buy small digital scales from Maplin which resolve to 0.01g; should make it easier to mix small batches of gel-coat. On opening the gel-coat tin, the layer of pinkish clear stuff on top is very noticeable this time. Stir well, and start to dispense, but the large spoon I usually use drips over too large a radius and some spills on the weighing pan instead of into the film can as intended. Stop, clean up scale and try again, this time using large syringe with flexible tube on nozzle - much easier to control. Mix 5g + 0.5g and apply to area of thin spot with small paintbrush. Re-position rudder to minimise runs (should have thought of that first!). Apply more over and around the spot as the gel-coat starts to thicken.
||File down the re-coated patch with Sandvik abrader. Switch to 240 wet on small block and a thin spot appears quite soon! Smooth the rest of the re-coated area and find some thin spots appearing on edge at end of hinge vee as well. Rinse and dry it off, prop it at ann angle to keep the thin spot almost horizontal. Mix up a small bbatch of gel-coat; should have been 5g + 0.5g but brain didn't catch up with the action and it turned out as 5g + 1g. Decide to use it anyway as the extra hardener (actually accelerator) should just mean faster gelling. Paint on with fine brush and add extra layers as gel-coat starts to thicken. Final result is much higher than really needed but as it's so small it won't take long to file down.
||This time, remember to take off wristwatch before starting - had noticed some grey marks further along the root where the watch had been rubbing as I worked on the re-coated area. File down the gel-coat pimple with Sandvik abrader. Rub down wet with 240 grade wet-and-dry on 88mm x 38mm block, using spotlight to check the edges as they get down to near flush with the surrounding areas. Rinse, dry, apply 3m Dry Guide Coat and go over it again with 240 grade. Rinse, dry, apply DGC and rub down wet with 360 grade on small block. Repeat rinse, dry, DGC, rub down process again with 600 & 800 grade. Rinse again and rub with wet Abralon 1000 disc held freehand. Repeat with Abralon 2000. Apply Farecla G3 paste, rub down, rinse, dry. Looks pretty good. Seems to be a slight hint of a thin spot on curve near hinge vee. Decide I can live with that.
||Unclamp rudder and re-clamp with tip (top) up. Apply 3M Dry Guide Coat to tip area, keeping it off polished side as well as possible.
Rub down wet with 240 grade wet-and-dry on small block.
Rinse, dry, apply DGC and rub down again with 360 grade wet. Repeat rinse-dry-DGC-rub down cycle with 600 & 800 grade. Small patches on trailing edge corner looking suspiciously thin, and another line near port side. Pretty small and inconspicuous, though. Rub down wet with hand-held Abralon 1000 and then 2000. Rinse & dry. Apply Farecla G3 paste and rub down. Rinse & buff dry with paper towel. Looks good, except for the aforementioned small thin spots. I'm coming to the conclusion that if I can't easily do all surfaces of a part with the same grade of wet-and-dry before moving to a finer grade, it would be best to rub down the tips and other potentially-awkward parts before doing the main faces of any flying surface.
||Remove rudder from clamp. Set on table with hinge flange along outer support (where TE normally goes when doing faces). Cut 100mm length of 35mm x 35mm x 3mm aluminium angle. File outer edges round and smooth off with emery. Try rubbing hinge flange (between hinges) wet with 240 grade wrapped around it. OK, but need to do some coarser cutting-back first. Try Sandvik abrader on a few high spots, then fine side of Perma-Grit chamfered-end block. That's difficult to keep square to the surface so switch to a small piece of Perma-Grit sheet without backing. Care needed to prevent its sharp corners digging into opposite face of the vee, but otherwise OK. Smooth with 240 grit on angle. Don't feel the need for fine finish here, so it might well be left at that. Need to think about making a rounded-vee shape block to tackle the root of the hinge vee - maybe a piece of mahogany bandsawn.
||Find the piece of blue foam that was profiled to match the rudder hinge vee (in May 2004) & use it to look for a suitable piece of hardwood. Find a piece of mahogany 43mm x 68mm with the end already bandsawn at the correct angle (about 45 degrees). Cut off that end with about 7mm into the full section. Round the point roughly on the belt sander then tape a piece of P80 sandpaper (grit out) into the hinge vee and rub the block against it to get
the exact profile.
(The angle changes slightly over the full length, but the block is made to fit the shallower angle and thus can be used at the other end by rocking slightly to contact each face.) Chamfer the edges of the block slightly, tape a piece of 240 wet-and-dry to it and try it. Needs quite a bit of effort & care to avoid it tipping, because my grip on it is so far back from the working tip. Put rudder on the (carpeted) floor and straddle it on my knees to restrain it, and then can get 2 hands on the rubbing block. Gets a quite respectable finish reasonably quickly. Going slightly thin on one area towards the tip near root of vee, so decide not to pursue that much more. Should be able to work on the face opposite the hinge flange sufficiently well with it placed on the table, hinge edge outwards, once the battens are reconfigured for port-side-up. Unscrew battens and try to remember how they were arranged for working on the port side. Realise the LE one must have been different to the one just removed, so that it would clear the curve of the LE for access. Refer back to journal and relevant pictures. Those in film SL363 of May 2004 show that the LE batten was laid flat on the table with the hinges folded up against it; that might impede access to the LE. Can't see the melamine-faced batten shown in the pictures, so decide to use the one just removed, but lying flat. It's short enough to fit between the top & bottom hinges. Rout out a pocket to take centre hinge folded down, and chamfer the top corner nearest to LE to improve clearance. Position, make holes and screw down to table. Position & make holes for root end batten, keeping well towards LE so it stays below the plane of the port side at the TE end. Check that LE side of hinge vee is well positioned for access when rudder reversed.
||Screw blocks to table at root and tip of rudder to constrain it lengthwise. Rub down angled face of hinge vee wet with 240 grade on wooden wedge-shaped block. Switch to 180mm x 38mm aluminium block. Rinse, dry, apply 3M Dry Guide Coat outer part of angled face and slightly around LE. Rub down wet with 240 grade on 88mm x 38mm block. Goes pretty well until working on a low stripe between root and mid hinge positions -
a thin strip appears
alongside. Rub down the rest of the face to a satisfactory state. Rinse, dry. Prop up rudder to make problem area roughly level. Mask around the now 2 thin patches. Mix 3g + 0.3g gel-coat and brush onto masked areas, also onto a minor thin patch near the root of the vee towards the tip. Remove masking tape once it starts to gel. After a couple of hours, do another coat with 5g + 0.5g gel-coat, taking it beyond the masked areas. Repeat again after another couple of hours with 5g + 0.5g for a 3rd coat.
||Lay rudder flat on table again with LE out and rub down re-coated areas of hinge vee wet with fine side of Perma-Grit angled block. Switch to 240 grade on 180mm x 38mm block. Not easy to use in the space available, so switch to 88mm x 38mm block. As it goes down, find that where the edges of the masking tape had been, there are softish and sticky areas. The masking tape must not have been resin-resistant, and the adhesive on it had reacted to prevent proper cure of the gel-coat. I had noticed as I peeled it off that some gel-coat had crept under the edges of the masking tape, but just thought I hadn't pressed it down firmly enough. Rub deeply to remove all the contamination, laving several large patches down to the glass. Decide it would be best to give the entire face another few coats. It would be best sprayed, but in view of the above incident, I don't think I've got anything suitable to mask off the rest of the rudder, so decide to brush it on. Prop rudder up to bring face of vee approximately horizontal. Mix 50g + 5g gel-coat and brush on. Seems to be a lot more than needed; curious, as it took 60g + 6g to cover it when I sprayed it. After a couple of hours, mix 30g + 3g gel-coat and brush on second coat. After another couple of hours, mix 20g + 2g gel-coat and brush on third coat - that is just about right for quantity.
||Lay rudder down flat again and rub down LE side of hinge vee wet with fine side of Perma-Grit angled block. Fit another temporary wooden block to the table against the TE near the tip, as the short batten is allowing it to swivel when working near the tip. Switch to 240 grade on small ali block, but realise I haven't done nearly enough with the Perma-Grit. Rinse, dry, apply 3M Dry Guide Coat. Rub down wet with fine Perma-Grit. Much harder work on brushed finish than on sprayed as surface has many more and deeper undulations. Work as carefully as possible to avoid going too deep, remembering that the hinge vee was not filled and profiled to the same standard as the outer faces. Rinse, dry, apply DGC. Rub wet with 240 grade on small block. The scratches from the Perma-Grit need quite a bit of work to remove in places. What looks like a thin spot appears near the pushrod recess.
||Further rubbing confirms that it's definitely a thin patch. It feels like a high spot to the touch, but I'm surprised I didn't notice it before. It was not one of those that appeared at the first rubbing-down. Continue rubbing rest of hinge vee with 240 grade wet on small block. Place the rudder vertical, TE down, on the foam block vees to allow access around the LE where the edge of the brsuhed coat extends to. Rub down with 240 grade wet on small bock, using spotlight to see ripples. Rinse, dry, apply 3M Dry Guide Coat on port side of LE curve. Rub down wet with 240 grade wet on small block. Middle finger of right hand starting to bleed as the skin is being worn off with the swivelling action of the rubbing block. Lay rudder flat and rub inner face of LE curve with 240 grade wet on small block. Still quite a few scratches from the fine Perma-Grit visible on the LE face of the hinge vee. Rub them out with 240 grade using variously small block, wooden angle block, and freehand. Turn over and smooth inside of hinge flange. Needs Sandvik abrader to deal with a few lumps. It seems to leave things much more even than the Perma-Grit and not cause such deep scratches. A thin patch suddenly appears near top hinge. Rinse off and dry. Prop up with LE face of vee horizontal. Mix 3g + 0.3g gel-coat and brush onto the 2 areas already mentioned, plus a small chip on the edge of the hinge flange. Build up on main areas as it thickens so should not need further coats.
||File off the pimple of gel-coat with the Sandvik abrader and bledn edges with 240 grade wet on small block. Rinse, dry, apply 3M Dry Guide Coat around LE and part-way up hinge vee face. Rub down with 240 grade wet on small aluminium block. Repeat the rinse, dry, DGC and rub-down cycle with 360, 600 & 800 grade. Rinse & rub down freehand with Abralon 1000 and then 2000. Apply Farecla G3 and rub down. Polish off with paper towel. Looks satisfactory - a few pinholes and the merest suspicion of thin-ness along LE, but I think quite acceptable.
Re-arrange clamping battens to hold rudder port side up. Apply
3M Dry Guide Coat.
Put a fresh sheet of 240 grade wet-and-dry on the 300mm x 75mm aluminium channel and rub down wet. When only a few small low areas remain, switch to small aluminium block. Rinse, dry, apply DGC. Out of stock of 360 grade, so put a fresh sheet of 400 grade wet-and-dry on the ali channel and rub down wet. Finish with 360 grade on large ali block. Rinse, dry, apply DGC. Rub down wet with 600 grade on the ali channel and finish with small ali block. A strange contour appears along TE near middle, with a slight colour change. Looks as though I've rubbed through the gel-coat and into the underlying micro fill! Not too obvious so will leave it as is for now. Rinse, dry, apply DGC. Rub down wet with 800 grade on soft-faced ali channel and finish with small block. Rinse, rub down freehand with Abralon 1000 and then 2000. Rinse, apply Farecla G3, rub down with damp cloth and polish off with paper tissues. Clean up slurry runs on other side & into hinge vee (need Farecla to shift some with a lot of dried-on DGC) and dry it all off. It's not perfect, but I would not be ashamed to fly with it. (Perfection is the enemy of good enough.)
||Wrap rudder in bubble-wrap and put in trailer. Clear rubbing-down materials etc off table and unscrew clamping battens. Start to remove all other stuff that has accumulated on table to make room for wing. Find a couple of battens for wing to rest on (and keep flap bracket attachments clear of table).
||Clear remaining bits off table and get help from Robert next door to move starboard wing from trailer to table. Referring to pictures of others' installations, experiment with the line-up of conduit to see how it would intercept the various ribs. The cut end of the conduit is quite sharp-edged, but it can be nicely smoothed with 240 grade wet-and-dry. On ribs out to aileron, mark out hole centres 150mm aft of spar face, at rib vertical centre on root to BL75 and 30mm up from bottom skin on BL97 (to clear aileron pushrod). Had to use a piece of bent thick wire as calipers to get correct distance from spar on BL29 rib because the angled rib is in the way of a straightforward measurement. Find a piece of 6mm rod to use as a former for making some hold-down clips for the stall-warner tubing - will need 10 off, at 10-15mm wide each. The BID sleeves for the conduit will need about a 22mm hole in the ribs. Don't have a suitable bit in stock; there is a 22mm wood auger but that wouldn't last long on the glass and it seems a shame to ruin it. Ideal would be a tungsten-carbide grit holesaw. Also have a look at how to get close enough to the spar for the hole in BL127. Tight fit drill attachment would be ideal, but of course it needs threaded bits. It does have a 1/4" collet but that won't take the Sandvik holesaw arbour which is 6.5mm A/F. Order a 22mm grit-edged holesaw from
Buck & Hickman
also a tungsten-carbide tipped pilot drill and an arbour extension rod, which will be helpful in getting at the angled rib near the root.
||22mm holesaw & accessories arrive from Buck & Hickman. While the holesaw fits my small Sandvik arbour OK, the extension rod does not (too big at 11mm A/F for either the small [6.5mm A/F] or larger [8.5mm] arbours), neither does the pilot drill (too small at 0.232", 5.88mm compared to 1/4" on the Sandvik ones). Try using the pilot drill in an ordinary drill chuck to make the pilot holes and find it's not running true - shank seems to be distorted where the grub-screw flat is ground. Will try to true it up later, but for now just use an ordinary 6.5mm TC-tipped masonry bit to make the pilot holes. Need to use the air-powered angle drill to get in between some of the ribs. Use a long 1/4" spade bit to make the hole in the angled rib. I was able to mark the horizontal line on it, but not the vertical one, so go through the root rib using the other holes to line up fore-and-aft. Once all pilots drilled including BL127, fit the 22mm grit-edged holesaw to the angle drill and cut all the holes to full size. The angled rib at the root can just be reached by going through the BL29 rib from the outboard side. Try the 20mm PVC conduit for fit and it looks fine,
all holes line up well
and the full 2m length is just perfect for the inboard section. Shorten the outboard piece and check that it will bend easily inboard of rib BL127 to meet the end of the inboard section. Smooth the cut ends with 240 grade wet-and-dry. Confirm with offcut that the conduit can safely be permanently bent using the 19mm copper-pipe bending spring. Mark the inside of the tip moulding using the conduit as a guide, drill a pilot hole from inside and then to 22mm from outside. Using 1 stroke of regular resin, make a layup for stall warner tube hold-down clips with 2 layers of about 250mm x 75mm BID on polyethylene sheet. Add peel-ply and
drape over 6mm rod
with another sheet of polyethylene on top, and weigh down with a piece of wood each side to form the flanges. Wrap about 300mm length of conduit in polyethylene. Wet out about 250mm x 150mm BID on polyethylene sheet and
wrap around polyethylene-covered conduit
to make about 2 layers and add peel-ply. Tape ends to stop it unrolling.