Problem with poly tunnel cover

[-pat m]

I honestly have checked the search facility for this problem but have not found an answer –
· I have a large’ish poly tunnel 90ft x 30 ft 10ft tall
· It is second hand but the cover is still very supple
· It has clamps at the bottom which you attach a base rail to which holds the cover in place
· I erected the tunnel last September and it has sustained no damage or ill effects through the winter storms /snow

I have notices that the polythene is lifting some 10 cm from the top rail during the strong winds this week (a neighbour who records wind speed says we had gusts of over 45mph) – the structure is scaffolding size poles sunk into concrete so I am getting no frame movement. - Also the 10 cm lifting isn’t flapping or violent it is constant as if lifted by pressure. I am concerned that I may wake up to find a ripped cover although there is absolutely no sign of stress or distress in the cover.
I am unsure what to do- The base rail is only constructed from roofing batons and twisted around the plastic, they are securely in place and I really don’t want to go around the whole structure un screwing them re tensioning and re screwing as they are only roofing batons and I know will only have a limited life.
Have I any options apart from re- tensioning the batons? I can’t lift the poles as the clamps that hold the cover/base rail determine their height.
This year was always going to be an experiment and I will get a better base rail system on the next iteration of the project but any advice to keep the tunnel together for the next 6 –12 months would be appreciated

Regards
Pat

[kentvegplot]

Hi Pat, what an odd problem. I'm guessing the 'lifting' is caused by the wind coming through one end of the tunnel and not going all the way through, hence putting the cover under some tension. Maybe this is a silly suggestion, but can you leave the tunnel open? If it is already open, is there a fence immediately behind it which is causing the wind to slow down rapidly? Can you put anything in front of the door which faces the prevailing wind to act as a windbreak?

If the cover doesn't seem under stress, you might just be worried about nothing :-)

[sewer rat]

I honestly have checked the search facility for this problem but have not found an answer –
· I have a large’ish poly tunnel 90ft x 30 ft 10ft tall
· It is second hand but the cover is still very supple
· It has clamps at the bottom which you attach a base rail to which holds the cover in place
· I erected the tunnel last September and it has sustained no damage or ill effects through the winter storms /snow

I have notices that the polythene is lifting some 10 cm from the top rail during the strong winds this week (a neighbour who records wind speed says we had gusts of over 45mph) – the structure is scaffolding size poles sunk into concrete so I am getting no frame movement. - Also the 10 cm lifting isn’t flapping or violent it is constant as if lifted by pressure. I am concerned that I may wake up to find a ripped cover although there is absolutely no sign of stress or distress in the cover.
I am unsure what to do- The base rail is only constructed from roofing batons and twisted around the plastic, they are securely in place and I really don’t want to go around the whole structure un screwing them re tensioning and re screwing as they are only roofing batons and I know will only have a limited life.
Have I any options apart from re- tensioning the batons? I can’t lift the poles as the clamps that hold the cover/base rail determine their height.
This year was always going to be an experiment and I will get a better base rail system on the next iteration of the project but any advice to keep the tunnel together for the next 6 –12 months would be appreciated

Regards
Pat

Only 10cm of lift !! My cover regularly gets about about a foot above the rail, but I do get gusts of up to 80mph now and again. Don't worry about it. I agree with the base rail system being a pain - the only way to retension is to dig a ditch under the base rail and drop the tensioners further down each hoop - I've done it once - will not be doing it again. My next tunnel will be tensioned by raising the hoops from the inside.

[JennieAtkinson]

Same for me as SR - we had 85 mph winds on Sunday and the whole structure was heaving around, never mind the plastic lifting. But today, was a glorious day of sunhsine and everything was back to normal.

[-pat m]

Thanks you for your comments. I am confident the tunnel is secure and the only issue is the raising of the cover. I will keep a watching brief over the next few storms. I was probably being unrealistic to think there would be no movement of the cover considering the size of the tunnel. Once again many thanks.

Pat