Would I be on the right path having a spread sheet with the formulas with all the range of distances loads etc say in small increments across the range then finding the largest figure by a search or by just displaying it all in a graph

Precisely.

It\s pretty much how you learned it in school. Calculate y for a reasonable amount of x values and plot those. Calculating y in excel is of course much faster.

/Møller

Still cant mark as solved must be me