10:27 Quote " It doesn't meet really modern health and safety regulations" but the Aerodux resists 24 hrs of boiling water... The best wood glue ever. Second best is the certified L285/H285 resin system, can also be used as sealant on wood surfaces. It penetrates deeper in the wood compared to aerodux, but is less viscous, hence requires ore care in joint accuracy. A very usefull video. Well done G. Macdonald.
The picture at 0:27 shows the effect of Kaurit glue failure. This particular glue uses formic acid as hardener. In time the acid dissolves the wood and the gusset plates on the rib joints shear off. Otherwise said: the cellulose of the wood is decomposed by the acid. The adhesive on itself is 100% OK, it is the adjacent wood that shears off. Evidence: A 1957 Ka6br showed ample tack between the plywood gussets (rondelles) and the ribstringers; they just fall off like paint flakes. The Ka6 rib stringers are in principal 4 * 7 mm in section where the 4 mm value is in contact with the gusset plate (half rondelle), hence this is a minimal connection area. I studied the fractures in detail. Always the dyed acid-side (pink or purple) of the joint fails. Minute wood residues stay behind on the glue, which on itself is intact. This fracture picture strongly points to wood deterioration by acid. Well done G. Macdonald.
I've enjoyed my flights on K6s, Ka7, Ka8 an K13 and we also have a private Ka4, Baby and Prefect still flying. Your work helps us keep these gliders safe and flying! Very informative and clear presentation Gordon, thanks as well from the Dutch glliding community!
The large number of gliders that BGA programs have found to be not airworthy and not economically feasible to repair is astounding. I'm afraid that many wooden gliders in other countries will be given inadequate inspections and will continue to be flown until we have more accidents.
