TJI is working up some prices for me. They were not sure they wanted to use it as it does cost more and they don't have a lot of profit margin in their planes. I told them I would make it easy for them, they can charge me more. I will admit that we have not had many issues with the TJI line of planes, but when you look at something like the Mini Q, I think the spar problem will vanish with the use of the correct bonding adhesive.
What I have been told by the NZ guys is when they crash a normal glider, the joints all pop, plus some skin damage. Same thing we all see. But a plane that has been seamed with the Techniglue 421 when crashed literally turns the skins into a puzzle as all of the joints hold fast.
Some may prefer to wreck a plane with the junky glue joints as they help preserve the skins, where the structural adhesives will transmit all of the forces into the skins doing a lot more damage. But please keep in mind we are talking about model ending crashes here. DS planes hitting the ground at speeds over 100 mph. The big advantage will be the slightly rough landing that opens up a joint and ends your flying day. Or maybe a mid air event where the plane is still bale to land under control as the wing didn't turn into paper.
Here is the prototype F40 that was crashed at speed into a mountain, as I recall it clipped a wingtip at a high rate of speed and that turned it fully into the mountainside for an instant stop. This is one massive delimitation of all bonding joints. Note in some cases the spar is missing from both the top and the bottom skins, the top skins for the flap is missing, etc.
This is a well built plane, the manufacturer does not have a history of bonding failures. I don't expect any plane to survive the energy loads this plane witnessed, it was just an example I had sitting around that shows how these joints do fail in the real world.
I was watching the sail boat race around the world, Vendee Cup. It was interesting to see how the composite boats were failing under the HEAVY loads they see. They did not have bonding failures, they had skin failures. This is not what we would have seen 10 or 20 years ago, it was always bonding failures back then, but these new adhesives are so strong now they move the failure point to the actual laminations. (Much like our gliders, these sailboats are trying to reduce weight and maximize strength. I was amazed to see how much they try to reduce weight on these boats.) You can see some of the cracks in this photo of the Hugo Boss boat this year:
