It's a bird? It's a man ? NO! It's a flying scaffold board!

[ToughButterCup]

Sufferin' scaffold boards Batman! Them boards is  a flyin' !

Where to Robin?

Off the scaffold and onto the roof Batman

 

And there indeed they sat sneering at us.  This one is quite artfully placed...

 

This one was angrier and smashed a few more tiles than the first one

 

And now for the good news. The tiles are Nulok tiles. Theres already quite a bit written about them - here if you want to follow it up

 

The good thing about them is that they are very easy to replace : I mean even a doddery old codger like me can do it

 

First, throw the broken tiles off the roof (yes I checked to see if Debbie was out of range)

 

and 

 

and then  replace the tiles. I haven't done that yet...... because

 

For once I obeyed SWMBO, and came down off the scaffold because it was quite lively up there.

 

But not before I had attached the scaffold boards to the scaffold with 3 tonne straps  and not before I had thrown one scaffold board per bay down  off the scaffold. I wanted to allow the pressure from  tonight's gusts to  dissipate rather than lift.

 

So now, from the ground the scaffold looks like this;

 

Replacing the tiles?

Easy. Slide a new one under the clips. Job done.  Had our roof been a normally slated roof, couldn'a done that now could I?

 

Well - I'll do it when the wind dies down; have to do what SWMBO  says (occasionally). 

 

[Carrerahill]

Glad this all went well. Could have been nasty.

 

I was out fighting sheets of OSB yesterday. The Celotex stayed put miraculously!

 

 

[joe90]

Glad it didn’t do anymore damage and as you say, great that with Nulock it’s that easy to replace a couple (mine would not be that easy, regular slates but with clips so not as bad as nailed). 

[Cpd]

Living where I do I was yet again in the firing line last night.... most of the time everything is fine as we are used to big winds, however my poor old landrover suffered a devastating blow..... and now I need to think about replacing the cover or preferably putting on a tin top. Boohoo said piggy. 

[epsilonGreedy]

  Quote

and not before I had thrown one scaffold board per bay down  off the scaffold. I wanted to allow the pressure from  tonight's gusts to  dissipate rather than lift.

Expand  

 

A British catamaran designer called James Wharram use to specific slatted decking based on similar thinking, he believed a catamaran with a slatted deck bridging the two hulls was less likely to flip. Decades later he conceded that a high-end aerodynamic expert had explained the fallacy of this belief. Anyhow those straps look serious.

 

[ToughButterCup]

  On 13/03/2019 at 11:01, epsilonGreedy said:

[...]

Decades later he conceded that a high-end aerodynamic expert had explained the fallacy of this belief. 

Expand  

 

I'd be extremely interested in reading that advice - or reading round that advice.

The lifting force local to that corner of the house is directly proportional to the wind direction.  In this case anything North of North West really 'gets it'.

My little bit of aerodynamics understanding makes me wonder if I have - in creating the slots -  merely created three or four turbulators that would be likely to puncture any drag bubble (downward pressure) there might be above the boards - thus increasing the lift acting on the boards.

 

'Nother sleepless night in store, it seems. 

[ToughButterCup]

  On 13/03/2019 at 10:57, Cpd said:

[...]and now I need to think about replacing the cover or preferably putting on a tin top. Boohoo said piggy. 

Expand  

 

Rag-tops, always the weakest link in any Landy. Never quite had the courage to fit one on mine.

[epsilonGreedy]

  On 13/03/2019 at 11:11, recoveringacademic said:

I'd be extremely interested in reading that advice - or reading round that advice.

 

Expand  

 

I used to subscribe to the Wharram community newsletter 30 years ago which was the source of the discussion. Those magazines went in a house move many years ago. I think you have got re. turbulence.

 

  On 13/03/2019 at 11:11, recoveringacademic said:

My little bit of aerodynamics understanding makes me wonder if I have - in creating the slots -  merely created three or four turbulators that would be likely to puncture any drag bubble (downward pressure) there might be above the boards - thus increasing the lift acting on the boards.

 

Expand  

 

Not sure but I do hear that racing sailors like slots and the associated lift.

 

  On 13/03/2019 at 11:11, recoveringacademic said:

''Nother sleepless night in store, it seems. 

 

Expand  

 

Instead dream positive, your NuLok roof has survived its first major wind stress test.

[ProDave]

Very windy and very wet here, but no damage and no UFO's.  Ground mounted solar / shed has passed it's first storm test.

 

Re Landy's,  When I finally get my garage clear of building stuff so I can get it in, I want to take the top off completely and run it al fresco for a summer.

 

Re slots, a big part of sail performance is the slot created where the genoa overlaps the main sail.

[ToughButterCup]

  On 13/03/2019 at 11:37, ProDave said:

[...]

I want to take my top off completely and run  al fresco for a summer.

Expand  

 

????

[Bitpipe]

Pretty sure our scaff boards had a semi circular clip to hold the inner board to the inner horizontal pole and a kicker clipped to the outer board.

 

I remember well the first night we spent in the caravan, Easter 2015. Was quite windy and the van was rocking back and forth - I woke up with a paranoid fear that it could somehow flip over and did not get back to sleep that night....

[Jeremy Harris]

  On 13/03/2019 at 11:11, recoveringacademic said:

 

I'd be extremely interested in reading that advice - or reading round that advice.

The lifting force local to that corner of the house is directly proportional to the wind direction.  In this case anything North of North West really 'gets it'.

My little bit of aerodynamics understanding makes me wonder if I have - in creating the slots -  merely created three or four turbulators that would be likely to puncture any drag bubble (downward pressure) there might be above the boards - thus increasing the lift acting on the boards.

 

'Nother sleepless night in store, it seems. 

Expand  

 

Slot effect.  Airflow accelerates through a slot, and can increases the lift on the surface behind as it does so (just because lift is proportional to the square of air speed).

 

Commonly seen on Bermuda rigged sailing vessels, when the slot between the foresail and the mainsail increases the lift from the mainsail, by increasing the airspeed over the low pressure (leeward) side (Bernoulli and all that).  Also seen on leading edge slats and slotted flaps on aircraft wings, both techniques to increase lift at reduced airspeed, so allowing safe and controllable flight at lower speeds, by lowering the effective stall speed.

[ToughButterCup]

  On 13/03/2019 at 11:50, JSHarris said:

Slot effect. [...]

Expand  

 

Yes. But....

In this case there's no lifting surface behind the slot: so, to pursue the aviation analogy, I am hoping I have created several lift dumps. And just in case I haven't, i've harnessed the boards to half a tonne or so of metal, and that in turn is secured to a section of up-wind scaffolding.

 

OK, in view of tonight's little set of gust fronts, you're going to tell me I should have taken the boards off the scaffold aren't you?

Bugger.

[jamiehamy]

  On 13/03/2019 at 11:50, JSHarris said:

 

Slot effect.  Airflow accelerates through a slot, and can increases the lift on the surface behind as it does so (just because lift is proportional to the square of air speed).

 

Commonly seen on Bermuda rigged sailing vessels, when the slot between the foresail and the mainsail increases the lift from the mainsail, by increasing the airspeed over the low pressure (leeward) side (Bernoulli and all that).  Also seen on leading edge slats and slotted flaps on aircraft wings, both techniques to increase lift at reduced airspeed, so allowing safe and controllable flight at lower speeds, by lowering the effective stall speed.

Expand  

Ah! So that might answer a question I've had for a while. I remember reading somewhere that a certain type of sailing vessel was said to almost 'create her own wind'. That will be this? 

[Jeremy Harris]

  On 13/03/2019 at 12:05, recoveringacademic said:

 

Yes. But....

In this case there's no lifting surface behind the slot: so, to pursue the aviation analogy, I am hoping I have created several lift dumps. And just in case I haven't, i've harnessed the boards to half a tonne or so of metal, and that in turn is secured to a section of up-wind scaffolding.

 

OK, in view of tonight's little set of gust fronts, you're going to tell me I should have taken the boards off the scaffold aren't you?

Bugger.

Expand  

 

There is, the plank behind.  It was possibly lift that caused the planks to lift up and hit the roof in the first place.  A plank can produce lift, not as efficiently as an aerofoil, but still significant, and possibly greater than the drag force from just the wind acting on the projected area of the plank, perpendicular to the air flow direction.  Try standing outside, holding a plank edge-on into a stiff breeze and you will feel the lift the moment there is any angle of incidence on the plank.

 

When sitting on a scaffold, with a probable stagnation area where the underside of the planked section abuts the wall, there's a fair chance that air will try to flow from the higher pressure side (underneath the planks) to the lower pressure side (above the planks) through any slots, so possibly increasing the lift forces on them.

 

TBH. I think this is possibly more of a theoretical debate than a practical one, as whether the added lift from the slots is significant enough to increase the risk of them lifting is pretty hard to assess.

 

As a final point about slots, if you're ever down near Abbeville take a look at the blades on the old windmill there.  It uses a leading edge slots to increase the lift on the blades, right at the stock.  The people that came up with this design probably hadn't got a clue why it worked, they just knew it did.

 

 

[Ed Davies]

Went up to the site on Monday to get some 25mm sheets of Celotex out of the container into the house and cut them up into strips to go in the I-beams forming the window reveals. Got two out of the container, couldn't hold them into wind as planned so held them flat across the wind as I walked to the house door. Just as I was stepping across the ring beam for the porch/greenhouse towards the front door a gust arrived and I lost my balance finishing up stumbling downwind just about hanging on to the sheets. Managed to guide them back into the container where they're sitting now with a slight curve in the middle. Straight home again and didn't even think of going up there yesterday or today.

[Barney12]

  On 13/03/2019 at 11:43, Bitpipe said:

Pretty sure our scaff boards had a semi circular clip to hold the inner board to the inner horizontal pole and a kicker clipped to the outer board.

Expand  

 

Exactly how ours were done.

 

[Ferdinand]

  On 13/03/2019 at 12:05, recoveringacademic said:

 

Yes. But....

In this case there's no lifting surface behind the slot: so, to pursue the aviation analogy, I am hoping I have created several lift dumps. And just in case I haven't, i've harnessed the boards to half a tonne or so of metal, and that in turn is secured to a section of up-wind scaffolding.

 

OK, in view of tonight's little set of gust fronts, you're going to tell me I should have taken the boards off the scaffold aren't you?

Bugger.

Expand  

 

No, and hoping it survives alright.

 

F

[Jeremy Harris]

  On 13/03/2019 at 12:31, jamiehamy said:

Ah! So that might answer a question I've had for a while. I remember reading somewhere that a certain type of sailing vessel was said to almost 'create her own wind'. That will be this? 

Expand  

 

Pretty much, yes.  Sailors noticed long ago that trimming the sails to get an optimum slot tended to stop the sail behind luffing, and caused it to fill and produce a fair bit more drive; it looks and feels like the slot is "pulling" the sail behind. 

 

I learned to sail on a Falmouth Working Boat in the early 1970s, and the oyster fisherman owner hadn't got a clue about aerodynamics, but still won most of the Working Boat races during the Summer.  My first crew role was as mainsheet hand, the least critical sail to trim; all I had to do was watch the luff of the sail all the time when racing close-hauled (or as close hauled as a gaff rig ever gets) and trim it to "just" stop it being backwinded at the luff.  The staysail hand's job was to keep the staysail slot as tight as possible whilst still getting the maximum slot effect over the luff of the mainsail.  Likewise the jib hands job was to do the same with the jib, keeping the slot between that and the staysail as tight as possible.  All this was done without speaking, and if any of us took our eyes off the luff of our sails we'd get a clip around the ear from the skipper's boathook...

[Thedreamer]

Good to hear that those slates will be easily replaced.

 

Might be more of issue for me, with the rain we get here, but what do you guys do with your temporary downpipes when it's windy? So far only the most exposed and awkward pipe has fallen over once since they went up in November time.

 

 

 

 

[ToughButterCup]

  On 13/03/2019 at 13:00, Thedreamer said:

[...]

what do you guys do with your temporary downpipes 

[...]

Expand  

 

?

Are you posh or wot?

The wind is due to drop later today, I'll pop up and fit the replacement tiles and take some photos for those who are interested in Nulok

[Thedreamer]

  On 13/03/2019 at 13:09, recoveringacademic said:

 

?

Are you posh or wot?

Expand  

 

I think they cost around £40, the proper stuff is cast iron effect Brett Martin, prehaps I am a gutter snob?

[ToughButterCup]

And this is how quickly the tiles can be replaced....

Clear the broken tiles,

 

shove under the tile above and ....  10 minutes later all six tiles have been pushed into place

 

There's a gap in the tiling to allow for the fact that some idiot or other put the Kwikstage too close to the house.?

Rookie scaffold error that....

[Declan52]

  On 13/03/2019 at 15:55, recoveringacademic said:

And this is how quickly the tiles can be replaced....

Clear the broken tiles,

 

shove under the tile above and ....  10 minutes later all six tiles have been pushed into place

 

There's a gap in the tiling to allow for the fact that some idiot or other put the Kwikstage too close to the house.?

Rookie scaffold error that....

Expand  

Loosen the tie bar and use a plank/ledger as a lever and wedge it against the wall and push the standard out enough to get your tiles in.  If you have the jack leg on a bit of timber, like your meant to,  then it will slide out very easy. A few goes will do it and then redo the clamp. 

[ToughButterCup]

  On 13/03/2019 at 16:14, Declan52 said:

[...]

  If you have the jack leg on a bit of timber, like your meant to,  then it will slide out very easy. A few goes will do it and then redo the clamp. 

Expand  

 

Jack leg?