watching some footage last night, what is the helm doing pumping all the time? Looks like a hydraulic pump, but whats it for? (asking on a mtb forum clearly not the best place to ask!)

I thought it was to do with the sail trim.
I want to know what the guy behind the rear beam is for.

I want to know what the guy behind the rear beam is for.

keeping the bows from dissapearing under water when they bear away…

keeping the bows from dissapearing under water when they bear away…

They need him on the extreme 40’s then.

ZX81s

I want to know what the guy behind the rear beam is for.

Corporate guest on each boat.

Looks like a hydraulic pump

Well on a ‘normal’ boat it would be [hydraulic] backstay, although the mainsheet trimmer would be usually expected to do this.
On the AC45’s (which have non-hydraulic running backstays) it’s probably a similar depowering tool on the wing.