On Tue, 07 Jan 2020 23:18:22 -0000, Rod Speed wrote:



"Commander Kinsey" wrote in message
newsp.0d1n2gjawdg98l@glass...
On Tue, 07 Jan 2020 21:57:36 -0000, Rod Speed
wrote:



"Commander Kinsey" wrote in message
newsp.0d1jwqxqwdg98l@glass...
On Tue, 07 Jan 2020 20:35:23 -0000, Rod Speed
wrote:



"Commander Kinsey" wrote in message
newsp.0d1gkmz9wdg98l@glass...

Why secure a loft trapdoor in a storm?

And what's the roof pitch to do with anything?

In theory you can get a suction effect similar to
what you get with an aircraft aerofoil section.

In practice it isnt seen often enough to matter.

The conservatory I've half built is staying firmly put. I guess I
bolted
it together well :-)

You can get flatish roofs lifted right off by strong
winds. basically due to the aerofoil effects.

Not done the roof yet. Hmmm, perhaps I should secure it very tightly..
Mind you polycarbonate can snap easily in a wind.

How powerful is aerofoil in a wind?

Flat roofs regularly get ripped right off and land on the
neighbour's etc. Corse that's in cyclones and hurricanes.

I wanted a more quantitative answer.

The limit would be 14psi, which would be horrendous, but I assume that
needs a lot of wind.

Yeah, normally only in cyclones and hurricanes etc.

We don't get those.

"Close and secure loft trapdoors with bolts, particularly if roof
pitch is less than 30°"

https://www.metoffice.gov.uk/weather...afe-in-a-storm