Old grape vine

I'm now looking after an old grape vine that's been neglected for a few years. The problem is it's in an old polytunnel that's falling apart so I don't think it's getting enough sun. Furthermore, some pine trees have grown very tall casting the who area into shade. The vine puts out a lot of grapes but they're very sour. My plan is to cut the thing way back, clean the polytunnel to let more sunlight in and get the pine trees topped to also increase light. I'm also looking into fertilizing and what not. Does anyone else have some ideas?

But this fellow has done a great job keeping himself alive with almost no care for years!

 

Looks like it could do with a cut back after the leaves have fallen.
But be selective, dont just cut it all back, its well established so you need to find the old framework of stems and keep them.

Give the grapes a bit longer, they might not be ripe yet, and ventilate the tunnel well to stop botrytis rotting the grapes, you could remove about half the leaves to improve airflow.

 

Great suggestion. I'll do some selective cutting back and thinning later on and perhaps train/tie some of the branches to the ribs of the polytunnel as someone else has done previously. Seems to be a good trellis. Not sure how I can improve airflow in the polytunnel but something to think about. Thanks!

 

@Frazzled you may also need to drastically thin out the bunches of grapes too. I can remember the first year we had fruit on our vines..smothered with bunches of promising juicy grapes... So very sour!!

They now get a good thinning out!

To be honest though I think we will eventually get rid of them.

 

Having seen another picture of the tunnel, I think the cover is ripped so maybe improvement in ventilation isn't needed.