I would like the Geo to rotate along the curve, i.e. always sit orthogonally on the curve.
My attempts have so far always failed.
Help would be nice 
Array_param.gh (10.5 KB)
Array_param.gh (10.5 KB)
Could you attach your Rhino file, or internalize your Brep and Curve.
I think you are looking for Perp Frame component.
i tryed it with the pframe component, but i didnt work.
There we go.
You could avoid calculating the local plane of the beam if you reposition it at the origin, along a world plane, in Rhino.
Also, are you sure you want beams to be unequally spaced ? If not, you are probably in the need of Divide Curve.
Array_param.gh (7.5 KB)
It Works Perfect, thank you. I would never have go this way, but it makes sense.
Yes i need them in unequally spaced.
As said above, you can save a lot of components if you reposition your reference element in Rhino (which is generally a good habit - you can use Orient3Pt command to do that).
In your first example you plugged the output of Evaluate Length, which is a Point, to the input of Orient, which requires a Plane. So Grasshopper converts your point to a plane, and this happens to be the XY plane moved to that new origin. There is no information about the curve there, hence the need for Perp Frame.