Wind is gusting worse than I've ever known before. Just went outside to check the observatory was not leaking but found it had no roof. Completely lifted off and stuck in a nearby tree.
Son and daughter here for Xmas so all helped to remove the soaked scopes and equipment.
Lashed the roof down and hope it won't blow further.
Pictures to follow.
Thats a sod, but it is a bit windy.
That's bad news Mark sorry to hear that. I was down Bromley earlier doing some last minute shopping and its the closest I have ever come to getting blown over.. Wind really strong..
Quote from: MarkS on Dec 23, 2013, 19:52:00
Wind is gusting worse than I've ever known before. Just went outside to check the observatory was not leaking but found it had no roof.
I take it it is leaking then. :-?
Sorry to hear that Mark.
This wind in for the night, so just lash it and leave it as something that big could do some serious damage.....and injuries.
Good luck
Quote from: JohnP on Dec 23, 2013, 20:18:25
its the closest I have ever come to getting blown over.
Drunk again. :roll:
Tony G
Here is is:
(http://www.markshelley.co.uk/webdisk/obsy_roof1.jpg)
I have since lashed it so hopefully it won't go any further. It might self destruct overnight though.
What happened to the clamps holding it down?
Can it be laid down ?
It will act like a sail or kite standing upright
Mick, I like it that way.
Quote from: Rocket Pooch
What happened to the clamps holding it down?
The roof has ripped away from the part of the structure that is clamped. Still trying to work out exactly what happened :(
I'm guessing the air travelling over the roof created lift by reducing the pressure and it pulled the roof off from the camps?
Yeah Wind, like Chris said.
Tony G
Mark, really sorry to hear that has happened, I've just looked at the radar and there is a lot worse to come tonight :( can't help feeling you should have used ply rather than sterling board as it's much heavier and more water repelant. Hope you get it sorted.
Quote from: Tony G on Dec 23, 2013, 20:23:00
Quote from: MarkS on Dec 23, 2013, 19:52:00
Wind is gusting worse than I've ever known before. Just went outside to check the observatory was not leaking but found it had no roof.
I take it it is leaking then. :-?
Sorry to hear that Mark.
This wind in for the night, so just lash it and leave it as something that big could do some serious damage.....and injuries.
Good luck
Yep I'm drunk again but I remember being blown off of my feet near to the summit of skafell pike and I'm over 20 stone :o
Quote from: JohnP on Dec 23, 2013, 20:18:25
its the closest I have ever come to getting blown over.
Drunk again. :roll:
Tony G
Quote from: MarkH
can't help feeling you should have used ply rather than sterling board as it's much heavier and more water repelant.
Heavier!?!? I could just about roll it on its wheels with its current weight! Wouldn't want it heavier.
Surely the heavier the le likely to be blown away.
I think heavier would mean less likely hood for it to fly away. I feel however there's another reason why it has taken off.
Maybe the Crayford society sabotaged it?
Quote from: MarkH on Dec 23, 2013, 21:09:38
Surely the heavier the le likely to be blown away.
It didn't help the Captain of this vessel in his accident report........I thought it was too heavy for the wind to do anything.....
(http://farm6.staticflickr.com/5520/11520738583_3452be1c26_b.jpg)
Sorry about the size.
Tony G
Just up the road
(http://www.bbc.co.uk/suffolk/content/images/2007/10/16/plane_blue_460x300.jpg)
Good job it did not go thru the conservatory!
Just found out about your observatory - really sorry to hear of it. If you need a hand sorting it out over the weekend let me know.
Julian
OMG Mark, that roof weighs a ton, just goes to show how strong the wind must be.
I have just been toying with whether to remove the POD cover as it's getting a real buffeting and don't want it flying off and losing it. Not that it would do any-one any harm but I just don't want the job of having to make another one. I've double knotted the cords, it's very good at keeping the rain out. So far it has survived, but now I have read what's happened to you, I might change my mind. Gonna stay up for a bit and keep an eye on it.
That's going to be a marathon job getting your roof back on afterwards. Hope your kit hasn't been damaged.
Carole
2am - power cut. Can't sleep. Ropes still holding roof in place but its beginning to fall apart. I was nearly blown over.
Just saw your post on the BBC web site! I hope you are all OK if you need a hand Friday or Sunday let me know.
Mark
Would your insurance cover any damage and repairs?
Tony G
Sorry to hear what has happen I hope nothing is too damaged and the insurance covers what is.
Well it was windy the local Metoffice weather station recorded 70mph winds for a 1 hour period last night which does not sound to bad, but it can't record more than 70mph. So we had at least constant 70mph winds for a while around 3am.
The rain was flat against my largest was and was all yesterday, this has pushed the water through the wall, basically air bricks etc.
Bum
Sorry to hear about your observatory roof Mark. i hope the inside isn't damaged and that your telescopes and equipment are OK.
Delphine
Oh dear Mark. good job you were around. dont know what to say other than try & blaze on. hope the rest of the shed is ok
That's incredibly bad luck. A bit of glue might have helped bond the structure together. Was it nailed or screwed? Either way it's screwed now!
Have had a suggestion that marine ply would have been better to use for the build
What's the status report this morning Mark?
Hope the water hasn't damaged any of your kit.
Clocked 79.1 mph at 1:47 :o
My over engineered observatory survived 80mph winds! The trampoline did not though, well lets just say it needs a repair.
I guess Mark is out there now with a happer to pull it apart before Friday's even worse storm.
Oh and Tony, this explains why a shallow roof like that one flies.
(http://www.science-projects.com/HurricaneHouse/HurriAngle2.GIF)
http://www.science-projects.com/HurricaneHouse/HurriHouse.htm
i did not think the forecast looked as bad for friday.
Power came back on at 3pm this afternoon, so here's an update.
Lat night I lashed the roof to the main observatory framwork as best I could with rope. I was awake all night until the winds died at 4am, checking it every so often. The structure broke apart quite significantly. This morning I dismantled it and put a tarpaulin over the roofless shed. Mopped up all the water inside.
Equipment is all drying out and I'm hoping no permanent damage. Scopes were OK - just a little water inside the C11. Haven't switched the mounts or laptops on until completely dry.
Here's a couple of pics from this morning:
(http://www.markshelley.co.uk/webdisk/obsy_roof2.jpg)
(http://www.markshelley.co.uk/webdisk/obsy_roof3.jpg)
I'm still amazed that the wind managed to lift it and break it free of the runners. Next time I have a roof, I will securely clamp the roof trusses themselves to the shed structure.
The overhang of the roof had embedded itself 6 inches into the ground. I bet the wind catching the overhang was part of the reason for "lift off".
Mark
What a disaster Mark, water in the C11, and who knows what else might be affected - fingers crossed it will all be OK.
But what a mess it has made of your roof, and all that wonderful work. Plus all the effort involved last night in that dreadful weather having to bring the kit inside and then lash down the roof.
Can you imagine if you had not been there to check it?
Carole
Bloody hell :o
Nature certainly did a serious job on that roof
wonder if it's worth putting some anchor points in the ground and get some long ratchet straps to throw right over the top should the weather threaten again? Obviously when you've got another roof...
Fingers crossed you can get it patched up... :o
Ouch! Sorry to see that disaster! Hope you managed to salvage the equipment before it suffered damage!
Anchored ratchet straps. Great idea Ian!!
Good grief... That's terrible Mark.
And here s me feeling sorry for myself having found the flat roof to the front of the house leaking with water coming down the walls of my computer room and through the light fittings in the ceiling and in the kitchen too. 6 Fence panels down and my 1.1m motorised satellite dish which is mounted on a pole raised above my house facing over the pitched roof but now out of alignment!
Wrong time of the year for this to happen!
Hopefully it's only the roof that's out of commission.
Just Mae sure you get something sorted for the winds coming back on Friday. I've put tarps on my flat roof held down with lots of heavy weights. Got no idea how water as got in... Nothing obvious and water has just found its own low point. Not down the electrics any favour either!
nearly lost my satellite dish, the wind ripped two of the four anchor bolts out of the wall. Luckily the other two held because I'd been too lazy to take the old bracket off. No idea where that would have ended up if it'd come free. Also lost about four square metres of pebbledash off the kitches too, although that's actually helpful. That wall's going to become internal when my extension's done. Right now, it's a replica of the Somme.
I had something similar with my flat roof too Les. Water flows quite happily up a vertical surface if it's windy enough, and I've got the watermarks in the plaster to prove it.
We lost our Satellite dish It landed right next to our neibours sports car! Big relief when we could check in daylight that it didnt hit it on the way down! The engineer is coming on sunday to attach the dish again. In the meantime we are watching telly via the laptop!!
Delphine
So sorry to hear ... and see the photo`s of ... the disaster of your observatory roof, Mark. And the damage to your kit. We hope that the astro equipment will dry out without too much damage and the roof can be repaired successfully.
After all your hard work ..... bloody nora!!! No doubt you will be up and running in the near future and for that Rose and I wish you all the best with the work you will have to do. Ian suggested straps over the roof; and I was going to suggest storm straps, like we use on a large tent, but
it`s a bit late for that now.
Anyway, have a Happy Christmas and a good New Year to you, Dee and your family.
Cheers for now, Rose and Doug.
Quote from: Delphine on Dec 25, 2013, 07:33:47
We lost our Satellite dish It landed right next to our neibours sports car! Big relief when we could check in daylight that it didnt hit it on the way down! The engineer is coming on sunday to attach the dish again. In the meantime we are watching telly via the laptop!!
Delphine
Quote from: Ian on Dec 25, 2013, 00:18:40
nearly lost my satellite dish, the wind ripped two of the four anchor bolts out of the wall. Luckily the other two held because I'd been too lazy to take the old bracket off. No idea where that would have ended up if it'd come free. Also lost about four square metres of pebbledash off the kitches too, although that's actually helpful. That wall's going to become internal when my extension's done. Right now, it's a replica of the Somme.
I had something similar with my flat roof too Les. Water flows quite happily up a vertical surface if it's windy enough, and I've got the watermarks in the plaster to prove it.
The anchor bolts Ive used on mine are huge. I think the wall would give way before the anchor did.... which really was a huge concern! Dishes are designed to collect.... and with no escape, they are good at catching wind!
Delphine... sky are not charging for the dish to be refixed are they? Obviously their "engineer" didnt do a good job in fitting in the first place! (I do laugh when I hear their installers called engineers!..... 1/2 day training is all their "engineers" get"! lol)
Well my flat roof (with tarp above) survived the extra rain yesterday, so hopefully I can just get it sorted and no further ingress.
Mark.... if you need a hand with anything to get you water tight... please shout... only to happy to help out.
I put a temporary roof on it Boxing Day morning by salvaging what I could:
(http://www.markshelley.co.uk/webdisk/obsy_roof4.jpg)
It survived last night's storm but the tarpaulin leaked so the floor was a bit damp (it hasn't had a chance to dry out yet). Bought a heavy duty tarp at 7:30 this morning from Jewson. Once the gusts have dies down a bit, I'll put it in place then I should be weatherproof again. Looks like the inside of the shed will recover. Electrics are fine so I've got a fan heater running in there now and already dry patches are appearing on the floor!
Not withstanding the roof, it's good that the fabric of the building is still sound and that there appears to be no other lasting damage.
What about the equipment - mounts, telescopes and the beer fridge ?
Robert
Did someone say Beer ? :o
It's good that you managed to get it covered in quickly with last nights episode - the forecast for Monday/Tuesday is looking dire as well
Well done Mark, I was wondering how you were managing during subsequent bad weather.
Quotethe forecast for Monday/Tuesday is looking dire as well
It seems unending.
Carole
I'm pretty sure all the equipment will be fine - I'm giving it all time to dry out thoroughly. Scopes are all definitely OK - the C11 has dried out. The good quality tarpaulin is in situ now so it's weatherproof again. Fan heater is drying out the inside. Haven't tested the beer fridge yet.
It's pretty clear to me now that the roof lifted up because it acted in the same way as an aircraft wing, generating lift as the air passed over it. So why on earth would anybody do this:
http://en.wikipedia.org/wiki/747_Wing_House
:o
Someone on SGL pointed out that a vertical obstruction along the ridge of the roof disrupts the airflow thus preventing the lifting and that maybe that is why older houses have ridged roof tiles like this:
http://www.bricksandbrass.co.uk/design_by_element/roof/victorian_and_edwardian_ridge_tiles.php
So why on earth would anybody do this:
Bloody architects Mark ... ever tried shifting furniture up staircases? And what about the architect that designed that idiotic building in London shaped as a parbola, that set shops opposite alight , you'd have thought architectes would have a grasp of basic physics, obviously not :roll:
Wickes do something that might do the trick - probably other suppliers also.
http://www.wickes.co.uk/invt/240040 (http://www.wickes.co.uk/invt/240040)
It should also be flexible enough to "tweak" with a hot air gun
Another pic that puts the roof and shed in context:
(http://www.markshelley.co.uk/webdisk/obsy_roof5.jpg)
Looking at the roofs final resting place, are you sure it wasn't just pushed back on the rollers by the force of the wind ?
Yes it does look like its just been pushed off the end of the runners . It it had been lifted in the closed position, I would have expected it to comletely flip over altogether.
The pattern of damage can only be explained by the roof lifting up sufficiently to rip itself free of the cross-members holding it down (which are still padlocked in place on both sides) and then sliding back along the runners until it crashed into (and destroyed) the back stop and then crashed into the ground with some considerable momentum.
Here is a picture of one of the 3"x2" members which was snapped in half by the force of the roof lifting up:
(http://www.markshelley.co.uk/webdisk/obsy_roof6.jpg)
The tarpaulin seems to have held during the storms whilst I was away in Spain from the day after Boxing Day until the New Year. I haven't looked inside the obsy yet because the weather is too horrible and we've only just had power restored after another 2 hour power cut :(
Wow, that was some force to do that. I agree with your previous statements that some kind of ridge or set of ridges along the roof to prevent a low pressure airflow would probably have prevented this as it has clearly acted like an aircraft wing. Alternatively when you rebuild why not put a flat roof on it ?
Mark your last photo put into context a bit more of what happened. I think the negative pressure caused by the wing effect has lifted the roof enough to allow the wind to get up underneath the gable and do the rest. I recon your original design would have survived if you'd had a deflector comming out from the wall immediately below the edge of the rooof and extending up covering the verticle face of the gable. Testament to your wood butchery that the roof pretty much stayed in one piece.
On the plus side I don't think you could have ever foresaw what had happened, and at least you hadn't shelled out on the nice William Morris wallpaper and at least the hand towell dispenser survived :lol:
Just been inside the observatory to check for damage during my time away. Most of the floor is completely dry but in a few places drips have been getting in through the temporary roof because of a (at least one) hole in the tarpaulin caused by chaffing. I've put some buckets inside to catch drips.
It's quite scary being inside because of the racket the tarpaulin makes in the gusting wind.
Quote from: MarkH
at least the hand towell dispenser survived :lol:
That's the fuse box!
As for a new roof. I'm still thinking about the design - probably a pent roof instead of a ridge roof. That shouldn't divert the air flow in a manner that causes lift. But I need to do some further research.
I knew that, was trying to cheer you up with a bit of humour. Seriously though, I think if you deflect the prevailing wind you should be ok. Diffusers may also help.
Did anyone read the link I put up there about roof design and wind?
Yes, it was very interesting. It indicated that a 15 degree pitched roof is "optimal" for generating huge amounts of lift - easily enough to lift a 650kg roof wholesale.
My son did aeronautical engineering so I plan to solve the Bernouilli equation for that design.
Mark,
With regards to your Avatar.......you don't wanna do it like that! :roll:
Seriously, it the costs covered on your insurance or are you sorting it out yourself?
Tony G
Quote from: Tony
With regards to your Avatar.......you don't wanna do it like that! :roll:
I shouldn't do what like that?
I'll be sorting it out myself once the weather improves i.e. probably wait until the Spring - it'll cost a few hundred quid I think
have fun with computational fluid dynamics :)
btw, IIRC the Bernoulli equation may not be applicable in this case as it applies to a single flow, the walls of the obs separate the flow outside with the stationary air within. However, CFD is full of assumptions and approximations when looking at real situations, this link might be worth a read too http://www.clayroof.co.uk/wind-uplift-calculations.htm (http://www.clayroof.co.uk/wind-uplift-calculations.htm)
Chris, it's a shame that paper hasn't got some maths to back it up. I don't think it's necessarily as simple as that, particularly as increasing the roof pitch also increases shear loading but it's in interesting read.
I guess another thing to think about is the direction of the prevailing wind on the site and align the ridge as close as you can with it. Or how about a ring of leylandii right around as a wind break ;)
Quote from: Ian
have fun with computational fluid dynamics :)
btw, IIRC the Bernoulli equation may not be applicable in this case as it applies to a single flow, the walls of the obs separate the flow outside with the stationary air within.
You might be right. I'll read through his lecture notes in any case, for a bit of fun.
of course, if you want to go the other way, you can use Navier-Stokes. The wikipedia (http://en.wikipedia.org/wiki/Navier%E2%80%93Stokes_equations) page is pretty much maths porn... :)
Quote from: Ian on Jan 02, 2014, 10:15:00
Chris, it's a shame that paper hasn't got some maths to back it up. I don't think it's necessarily as simple as that, particularly as increasing the roof pitch also increases shear loading but it's in interesting read.
Agreed would be better, I think Mark has nailed the next roof anyway the lower one with the tarp stayed on.
I've done quite a bit of internet research on this and the results are quite counterintuitive. In terms of negative pressure (i.e. lift) generated by wind passing over a roof, wind tunnel experiments show that wind approaching a gable roof from a direction of 45deg i.e. SW in my case is the worst possible case - it will tend to "peel away" upwards from the leeward front edge. This probably explains why the snapped 3"x2" timber was on the leeward side of the observatory.
So will a monoslope (pent roof) fare any better? The consensus from wind tunnel experiments and from the ASCE building code (American Society of Civil Engineers) is that a monoslope roof generates more lift than a gable roof. A flat roof is better than a gable but it is not a huge difference (as indicated by the graphs in the link that Chris posted).
Best roof of all is a steep (30deg or more) gable roof or even better, a steep hip roof.
In general, the biggest negative pressures are at the corners and edges (including the top ridge), so the roof panels need to be firmly screwed to the trusses in those areas and the trusses need to be firmly anchored to the walls.
I found a useful online calculator at:
http://engexp.com/calculators/asce_comparison.cfm
It calculates the negative pressures that various zones of a given roof with a given slope have to withstand for a given wind speed to meet the required ASCE standard. In pounds/sq ft!
Just got up & think i may have a little read of your suggestions, Ian, with a cup of tea.
Quote from: MarkS on Jan 03, 2014, 00:12:44
I've done quite a bit of internet research on this and the results are quite counterintuitive. In terms of negative pressure (i.e. lift) generated by wind passing over a roof, wind tunnel experiments show that wind approaching a gable roof from a direction of 45deg i.e. SW in my case is the worst possible case - it will tend to "peel away" upwards from the leeward front edge. This probably explains why the snapped 3"x2" timber was on the leeward side of the observatory.
So will a monoslope (pent roof) fare any better? The consensus from wind tunnel experiments and from the ASCE building code (American Society of Civil Engineers) is that a monoslope roof generates more lift than a gable roof. A flat roof is better than a gable but it is not a huge difference (as indicated by the graphs in the link that Chris posted).
Best roof of all is a steep (30deg or more) gable roof or even better, a steep hip roof.
In general, the biggest negative pressures are at the corners and edges (including the top ridge), so the roof panels need to be firmly screwed to the trusses in those areas and the trusses need to be firmly anchored to the walls.
I found a useful online calculator at:
http://engexp.com/calculators/asce_comparison.cfm
It calculates the negative pressures that various zones of a given roof with a given slope have to withstand for a given wind speed to meet the required ASCE standard. In pounds/sq ft!
So from all this research, can I assume that it just needs to be fastened down better in the Mk 2 version ?
Might also be worth reducing any overhang for the wind to get under.
Robert
Did any of the research discuss other methods for breaking the airflow other than the ridge tile? Having a 30 degree+ pitch plus additional strategy may help avoid future problems.
Quote from: RobertM
So from all this research, can I assume that it just needs to be fastened down better in the Mk 2 version ?
Might also be worth reducing any overhang for the wind to get under.
Yes - that seems to be the conclusion. You are also right that overhangs are subject to the greatest wind pressure of any roof part so I'll reduce them as far as possible.
Quote from: Ivor
Did any of the research discuss other methods for breaking the airflow other than the ridge tile? Having a 30 degree+ pitch plus additional strategy may help avoid future problems.
There are weird things that can be added to the corners to prevent damaging wind vortices (vortices which can increase lift) but I don't think I'll go to those extremes. A 30 degree pitch would increase height and therefore require planning permission. I think it would look unsightly in any case.
All these calculations and research is worth nothing when one of these hit, and they do.
I would be worried about the whole observatory, not just the roof.
http://www.bbc.co.uk/news/uk-england-24601190 (http://www.bbc.co.uk/news/uk-england-24601190)
http://www.bbc.co.uk/news/uk-england-leeds-19150029 (http://www.bbc.co.uk/news/uk-england-leeds-19150029)
http://www.bbc.co.uk/news/uk-17987640 (http://www.bbc.co.uk/news/uk-17987640)
Just make sure that Toto is safe. ;)
Tony G
How about a dome ;)
Mine never moved an inch, and its not bolted down either,
I was expecting to find it in someone else's garden.
Mac.
I think a Hip Roof would do the trick, it would have similar properties to a dome but easier (a lot) to make than a dome - but also harder to make than a gable type roof.
http://www.selfhelpandmore.com/building/roofing/designs/index.php (http://www.selfhelpandmore.com/building/roofing/designs/index.php)
I might still go for a monoslope (pent) roof.
Although it can generate more lift than a gable, the maximum negative pressure (i.e. lift) only occurs when the wind obliquely hits the high side first. So if I put the high side to the North, then it will be relatively immune to the prevailing S or SW winds and the worst wind directions will be NE and NW. For me NE and NW winds are relatively broken by the house and trees and if the roof did fly away again, it would be down the garden and not towards the house.
There is a very interesting study here which addresses monoslope and sawtooth roofs but unfortunately not gables:
http://www.davidoprevatt.com/wp-content/uploads/2010/09/bo-cui-2007-wind-effects-on-monsloped-and-sawtooth-roofs.pdf
Mark, given the extremities of the weather that fateful night I wonder if what happened was updraft. I have read a few bits and bobs on the net and from what I can make out it could have been a violent updraft which explains the extreme destruction. I recon it was just bad luck, hope all is up and running soon. Here's to some good observing weather.
Could well be updraft - anything that adds more extreme gusts to an already gusty weather experience. 4 or 5 trees went down in the field next to us.