Gero,
The design I'm building can use a butt strap joint instead of a scarf joint. The butt strap is used in the kayaks and 14ft Paper Tiger quite well. I used a scarf joint because I've done heaps of them but someone who is not confident with that type of joint would not have to use it.
The machine being built here is 2500mm long so it could probably make a kit quite easily and that would have a butt strap joint. Just to keep it simple.

Patrick,
I will keep taking pics as the project progresses and I will do a write up on the objectives of the design. Got a lot of family stuff on right now so can only grab an hour here and there but I will try to keep it moving forward.

I know that the voices in my head aint real,
but they have some pretty good ideas.
There is no such thing as a quick fix and I've never had free lunch!