Europa #435 G-RODO Build Journal - 2001 05
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|15||Start the building hours clock. Unpack rudder foam. Trim jigs to allow rudder overhang. Smooth LE contour. Radius tip and root. LE crushed slightly when holding against bench to sand root radius - will have to fill that with micro. Radius LE corners at root and tip. Decant some Q-Cell filler into plastic box for easier use. Try to dispense some resin to make a small batch of micro, and find the hardener side is not flowing.
Remove the outlet tube and its associated ball-valve. No blockage in that area. I will have to ladle out the hardener and dismantle the container/pump connection to get at the other ball-valve. (Obviously can't just pour it out as both containers are physically connected and I don't think I can rig suitable receptacles to let me pour successfully from both simultaneously.)
Inside the hardener container, above the liquid level, and particularly the underside of the lid, were covered with droplets of a very thick yellowish-brownish condensate. Acetone cleaned the underside of the lid. Also some yellowish liquid had appeared _inside_ the clear polyethylene sheet used to seal the float. Couldn't see how it got in there, as the integrity of the poly sheet and tape appeared good. The hardener itself appeared much as before.
Has vapour from the hardener (I'm sure there was no direct liquid contact) reacted with the polystyrene to create some potential contaminant? Remove and discard the float after draining as much hardener as possible off it
The float in the resin side appears OK.
I can deal with dismantling and cleaning out the pump (although it will be messy and annoying, not to mention wasteful, to have to do it again and re-check the calibration), but will the remaining hardener still be suitable for use?
Also reminded that acetone attacks blue foam when a drop of it got onto the LE tip corner. Another micro repair needed!
|16||E-mail David Cripps at SP Systems to see if he can offer advice on hardener problems.
Buy a glass-tube turkey baster at the Cheltenham Kitchener to empty the hardener reservoir.
Use turkey baster to suck out hardener and transfer it to original tin. Mark it "non-structural".
Clean out everything on the hardener side of the pump. I forgot that the only other valve is the one in the base of the reservoir, which can actually be actuated by poking from above. It must have got loosened at some stage in the dismantling as it is opening once removed. It does feel a bit scratchy, so spin it with some fine valve grinding paste to improve seat then clean up with petrol, acetone & airline. Re-assemble.
|19||Taking some time out from rebuilding hard disc on Mac 7100, make a collar (46mm hole in peice of MDF) to hold the hardener tin upside down on the pump reservoir. Tip fresh tin in and leave to drain. After a couple of priming strokes, it sems to be flowing OK now on the hardener side.
David Cripps sends a reply from a colleague which confirms my decision to regard the other hardener with suspicion. He also add 2 new bits of info; reservoir floats are best coated with mixed Ampreg 20; and the unmixed components are both water-soluble.
|21||Do a resin pump calibration run, mix the resin & make some micro to fill the 2 damaged areas on the rudder leading edge. Even with lots of q-cell in the resin, it still seems quite inclined to slump. Maybe it should have been even drier; but it wasn't that keen to stick to the foam at first, so I don't think it would have been any better in that respect if made drier. Of course 8 strokes of the pump is far too much resin for what I need; should have made a new float and used the rest to coat that.||7.8|
|24||Order some Perma-Grit files.
File down the 2 areas of micro fill on the rudder LE. Take a slightly bigger chunk off the root LE corner and re-radius it. Move the jig block further in, as a photo session with the curing tent showed that the rudder would be too near the tent. The double-sided tape is reasonably successful, but needs either meths or petrol to remove it from the table. Hints & Tips mentioned De-Solve-It - but not sure where I can get that. Petrol seems to attack the varnish on the table less, but a final wipe-over with acetone seems to be needed to get rid of the last stickiness. Cut a strip of peel-ply to to apply to the LE & TE; quite difficult to get a good edge. Maybe I should have ordered some narrow peel-ply tape as well as the wide roll.
Mark lines at 30 deg to LE.
Cut the first piece of UNI 1600mm long. It's easiest to measure it folded in half as both cutting flap and ruler work better with 800mm! Try to follow a single cross-thread when cutting, without total success. Maybe I'll mark it with the felt-tip first next time. Mark a central main fibre with felt-tip for alignment.
|25||Trim corners off 1st piece of UNI, after sticking masking tape along cut lines. Mark a cross-thread on the UNI, and use it to measure from. Make similar mark across width at next cutoff point for 1400mm piece. Cut it, mark a central main fibre & trim off corners.||11.7|
Straighten and smooth edges of one offcut from test layup to use as a broad squeegee. Mix 3 strokes of resin with 3 doses of q-cell (using a mixing stick as a spoon). Paint it on the rudder. Does about half the area, and seems a bit too thick. Mix another 3 strokes with 2 doses of q-cell. This seems a bit thinner & easier to spread. Weigh the 2 pieces of UNI - each about 154g. Mix 8 strokes of resin (nominal 144g) and spread over slurry. Wind 1st piece of UNI onto spare broom shaft and roll on; not too difficult to get a decent alignment, needing only gentle pulls on cross-threads to get main fibres aligned with the marks on the core. Seems quite wet on initial squeegeeing, so for next layer mix just 6 strokes of resin. Forgot to scissor-trim before mixing resin for 2nd layer! The scissors seem to work OK on the resin-soaked cloth, and the blades can be cleaned off with acetone easily. Not as much resin as expected left over once 2nd coat painted on; maybe it has thickened up slightly while waiting. In future must remember to mix a slight excess of resin. Roll on 2nd layer of glass. It's harder to get aligned well, and moving it around tends to shift the bottom layer too. I think it had acquired a diagonal twist when rolling up. Have to cut masking tape on edge in several places to avoid puckers. Put a date on the very small amount of resin left in the mixing cup. Should have cut peel-ply to size before starting layup; manage to cut it just slightly shorter than needed, so a patch is needed at LE root corner. Wil comes in to remind me it's lunchtime, and is pressed into helping with getting the tent on, thus avoiding danger of dragging the polyethylene in the wet resin. Tent heating starts about 13:30. Need to have proper place to deposit loose brush hairs picked up from layup, such as a yoghurt pot; and somewhere to leave the squeegees. A lot of resin globs have landed on the table; cleanup will probably be difficult, and will indicate whether it's worth putting down polyethylene sheet around every layup.
About 18:30, check cure and things seem to have gone off fairly completely. Turn off heat and check appearance. Still a few whitish patches on the peel-ply, and it hasn't gone around the root and tip ends enough, so there are hard lumpy ridges of resin on the undersides beyond it. Otherwise seems OK. Resin blobs on table are not too hard to remove with a chisel, but it's easy to dig in and lift bits of wood.
|29||Take first layup to Martin Carolan and he seems happy with the quality. He peels a small area of the peel-ply & is happy that the whitish areas are only bubbles between the peel-ply and glass, not within the glass layers. To avoid getting the weave unsquare, he suggests cutting UNI to size on the surface to be covered, both layers together, folding one half back and buttering that side of the surface before unfolding and laying the cloth down, and then folding the other half back to do the other side. Might be OK (although I foresee potential problems when the dry cloth is folded back over the wetted layer), but I think if I put it straight onto the broomshaft instead of rolling and re-rolling it, that might be as good. Probably wise to cut and lay-up without a pause between requiring storage of the cut cloth.
Perma-Grit order arrives.
|30||Peel back peel-ply at tip & root of rudder; not easy as did not leave enough well beyond the wetted area. Will have to remember never to stop a peel-ply edge on a wetted area, but always leave some spare to get hold of. Grind down blobs of resin with Dremel & cut-off wheel. This leaves quite a few hollows. Smooth off with unmounted Perma-Grit sheet. Cut off LE & TE glass close to foam, and sand flush. The long Perma-Grit block is good for getting a final straight edge here.||17.5|
|31||Cut off the support block at the TE of the rudder. Use a thin piece of metal to protect the rudder area beyond the block from the hacksaw blade. Sand down the foam fairly flush with the coarse tile file. Still seems to be a fair thickness of resin on the peel-ply, and without either end free it's hard to get started on peeling it. Manage to prise it up at one end with a knife. Peeling it back is quite hard work, and because it hasn't got a hemmed edge it tends to leave strands behind at the inner edge. Filing the inner edge down seems to clear the leftover strands of peel-ply OK. Use the long sanding block to blend in the TE to the main surface profile. The rudder is taking a noticeable curve along its length now, hollow on the raw foam side and convex on the glassed side. Stick down the jig block for the other side, and stick the rudder to it, using 5-min epoxy this time. The peel-ply will reduce cleanup required on the rudder itself from the epxoy dabs, and experience with the resin shows that the bench can be cleaned up without too much difficulty. Still might be good to lay some polyethylene around the working area, though. Weigh the rudder down with lumps of lead on sheets of ply to distribute the weight.||19.5|
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