I am in New Zealand (South Pacific) and getting the materials around here is a bit of a challenge.
Thanks to Cameron Garner I located a suitable local epoxy resin replacement. ADR246TG from Adhesive technologies NZ Ltd.
NOTE: THIS IS NOT A PLAN'S APPROVED EPOXY
ADR246TG requires cures of 24h @ 20°C followed by a post cure of 12h @ 60°C to achieve a Heat Distortion Temperature (HDT) of 90°C. It's density is 1.14 g/ml
Using ADR246TG and ADH28 (Adhesive Technologies NZ Ltd) I made the first layup of 6 BID to weight and examine the quality of my work/resin.
The ratio of resin hardener is 4 to 1 (weight)
The workshop temperature was 20° C (68° F)
The 6 BID 12.5x18" plies weighted 299 ± 2 gr. I made two batches of composite of 150 ± 2 g each and ended with a bit of excess at the end. In principle the fiberglass/resin ratio used looked a bit too much (too wet?) Ideally the ratio in a finished layup should be 2:1 (fiberglass to resin weight ratio).
The trimmed 10x16" composite rectangle ended in 338 g (11.92 oz) which is 8.3 % heavier than the ideal weight of 312 g (11 oz) but still in the expected range of [298, 354] g ([10.5, 12.5] oz)
The finished width of the 6 BID plies test rectangle is 2.12±0.02 mm or 0.0835±0.0007 in . This corresponds to 0.353 mm per ply or 0.0139±0.001 in. The expected width of a single BID ply is 0.013 in per ply or 0.078 in for 6 plies. This seems to be another indication that the layup was a bit too wet
I did a second 6 BID layup trying to get it a bit lighter this time (Building up the squeegee muscles). The difference with my first layup is that I spent a bit more time squeegeeing this time and a bit less stabbing it with the brush. ADR wets the cloth really well . the pressure on the squeegee was still very low but I did quite a bit more passes.
This trimmed 10x16" composite rectangle for the second test weighted 317±1 g (11.18 oz) which is 1.02 % heavier than the ideal weight of 312 g (11 oz) but still in the expected range of [298, 354] g ([10.5, 12.5] oz)
The finished width of the second 6 BID test rectangle is 1.86±0.02 mm or 0.0732±0.0007 in . This is 0.31 mm per ply or 0.0122±0.001 in. The expected width of a BID ply is 0.013 in per ply or 0.078 in for 6 plies.
And a third!
The trimmed 10x16" rectangle weights 300±1 g (10.58 oz) which is in the lower margin of the interval or 3.84% lighter than the ideal average.
In the third practice layout I did more squeegeeing that before Not a lot of pressure, but many more passes to remove the excess resin. Again, ADR246TG wets the cloth with no effort. Just a little bit of stabbing with the brush and most of the time squeegeeing and squeegeeing.
The three test for the 10x16" 6 BID layup:
NOTE: mean below is the average from Chapter 3 range
| Test | weight (gr) | weight (oz) | width (mm) | width (in) | width ply (mm) | width ply (in) |
|---|---|---|---|---|---|---|
| 1 | 338 | 11.92 | 2.12±0.02 | 0.0835±0.0007 | 0.353 | 0.0139±0.001 |
| 2 | 318 | 11.18 | 1.86±0.02 | 0.0732±0.0007 | 0.31 | 0.0122±0.001 |
| 3 | 300 | 10.58 | 1.86±0.02 | 0.0732±0.0007 | 0.31 | 0.0122±0.001 |
| mean | 312 | 11.0 | 1.98 | 0.078 | 0.33 | 0.013 |
Not that any pilot would be scared with mixing units :-) Here in New Zealand aircraft goes with speed in Knots, altitudes in feet, Atmospheric pressure in hPa (Hecto Pascals), distance in nm and the length of the runways in meters.
| magnitude | metric | imperial |
|---|---|---|
| length | 0.3048 m | 1 foot |
| length | 0.0254 m | 1 inch |
| mass | 28.3495 gr | 1 oz |
| mass | 453.592 gr | 1 lb |
| Volume | 3.78541 l | 1 US gal |
| Volume | 4.54609 l | 1 Imp gal |