u/Arbalete_rebuilt

At the moment, I’m spending most of my time doing calculations, building test specimens and test rigs, and running tests — you know, the fun stuff.

The pilot harness attachment has now passed its ultimate load test (finally). It’s bonded to the fuselage structure and, just in case that wasn’t enough, also bolted on. The calculations already showed that either the bonding or the bolts alone would be perfectly capable of taking the expected loads. But obviously, that wasn’t quite convincing enough, so a physical pull test was required as well.

So, naturally, this meant building an identical attachment like the one in the aircraft, designing and manufacturing a suitable test rig complete with instrumentation — and then actually running the test. No big deal.

The required tensile force of 1659 kg was reached without any drama and then comfortably exceeded. Even when pushing the load cell all the way to its 1000 kg limit, the attachment still refused to fail. How inconvenient.

So yes, it’s now been proven — quite thoroughly — that the attachment will keep the pilot firmly in the seat, even under extreme loads. Just in case there were any doubts left.

No new blog posts don’t mean nothing’s happening behind the scenes – quite the opposite. At the moment, though, we’re facing a few challenges that are noticeably slowing down progress on the build. One of the main issues is proving a suitable epoxy adhesive for constructing the wing. But let’s take it step by step:

After assembling the upper and lower spar caps, the next step is the side sheeting of the spars with plywood. The bonding area is very large and also geometrically complex. The adhesive we’ve been using up to now, Aerodux, is no longer suitable here, as the required working times fall well outside its specifications. A modern epoxy-based adhesive seemed like the ideal alternative. At the same time, we’ve been working on the structural strength calculations for the wing, as required by the BAZL. For that, however, reliable strength values for the bonded joints are essential.

And that’s exactly where the problem lies: for epoxy resins used as adhesives in timber construction, there are no sufficiently well-supported strength values available. While there are various products that are regulator-approved, no manufacturer worldwide provides solid, verifiable data for this specific application. In the end, that means every aircraft builder has to prove the suitability of their chosen adhesive through extensive testing – and that’s exactly what we’re doing.