Stevenson Screen roof

[Flying Eye]

Hi folks,

I can't seem to find an explanation of the intent of the roof patterns seen on various screens. By observation I have formed the general view that it's probably got a slope purely for water drainage, it's got gaps to encourage any heat to escape.

Often there is a double skin, the lower presumably being vented for heat and the upper not being vented for both shade and rain deflection. And I'm guessing this is simply in lieu of the gaps in the other style.

Is it as simple as that, or is there some other feature or point I have missed? I'm making general progress with my version of the design, but not got to the detailing of the roof yet. I'm collecting materials as I go along. Probably starting cautious test construction in a week or two if I am lucky. Really want to get it done before the more Wintery stuff gets too entrenched.

Should the taller end of the slope be to the north so as to minimise the chance of direct sunlight making any additional unwanted contribution?

[beteljuice]

Should the taller end of the slope be to the north so as to minimise the chance of direct sunlight making any additional unwanted contribution?

You would think so wouldn't you

... but

Some of the design is technical and some of the design commonsense.

Because people were opening the door(s) to read instruments, the door(s) face North (in the Northern hemisphere) to reduce any direct radiation whilst readings were taken.

The door(s) used to be hinged at the bottom to make a table for the reading taker, so the slope was away from the door(s) to prevent dripping rain on the paperwork (and to stop the door catching).

Naturally with modern remote reporting systems these considerations can be more flexible

[Flying Eye]

Thanks for that, makes the decision process rather less onerous!

I'm now mulling why I could not use a builders "site light" tripod to mount it on too, assuming I could work out how to get it stable enough to cope with wind etc. of course. It's the easy adjustment for height that really grabbed me! I guess a heavy axle stand for the base and an alloy pole could be used as well. Mounting might be trickier, but still just plausible I suspect.

Anyone got any views on those ideas? Or better suggestions for an easy build?

[Flying Eye]

OK, went a totally different route! (of course!)

So, this is how it came out. (had 5 minutes of nice weather this morning to take a moderate shot)



Pretty happy with it, the top is the 8 cheapo louvre vents from screwfix - just over a pound each, and then a £3.50 or so length of exterior grade uPVC angle at 32mm from Wickes in the corners. Looked a bit hopeless at first but was surprisingly pretty rigid once screwed together.

The base is from 25mm aluminium angle from screwfix (bit pricey but could not make up a decent size order for the other place. so it's a moot point really). Bracing is the 12mm version which is mercifully less pricey and worked very effectively.

Made a 4 armed wooden base out of 1.5 x 2.5 inch lumber which happened to be laying around, as were all the other parts like rigid PVC sheet for outer top, and 6mm ply for inner roof and base. Fitted out top and bottom with 4 soffit vents a piece, again from screwfix.

Probably spent a little bit more than is strictly happy making, but I have to say I had an absolute ball making it, it seems pretty solid and so it may well last for some time.

Nice thing is that it's sides are all exterior grade uPVC, so there should be no radio issues from verticals of steel or other metal like in most gill screen types. I'm using a TFA thermo sensor in there right now, until I get a new station. Seeing 0.5c to 0.9c discrepancy between this and local airfields' metars most of the time, So I'm pretty happy with it. Just got to find some PVC friendly matt black paint for inside sides now, top and bottom are already done, being wood.