hello Hal

You are looking at the hub in the top right of the hub images arent you ?

The hinge lines are angled and this does give delta as the coning angle increases. I havent measured exactly how much incidence changes with a given angle but I do know it is more than adequate for very rapid spin up and when up to speed the lift is excellent as the coning decreases.

I used delta angle of 15 degree on a two blade hub as an experiment and it was a failure. Blade balance is upset by using delta due to the up flapping also causing the blade to effectively advance forward, this does not seem to be a problem on 3 blade hubs but on 2 blade offset hinged hubs it caused a lot of vibration. I know the whistler model uses delta 3 but this is on a teeter hinge so balance is maintained. Has anyone else used delta on a two blade offset hinged hub ?

Note, Non delta 2 blade hub worked fine.

Cheerio

Sean