Trevor Sheppard <[email protected]> wrote: >Having just read an article about a home burning to the ground because >of the sun's rays being focussed through a glass paperweight (one of >those glass balls - which many of us probably have on our windowsills at >home..) I was surprised at how close to <my> home this actually came. > >I have one of those glass roof lights over the engine hole - I think >they are called something similar to 'bullseyes'? - and when I went to >open one of the small drawers in there today it was stuck tight. >Thinking it was the plastic carrying handle on the top (useless anyway >as it is screwed to the bulkhead) I gave it several 'tugs' and, >eventually, it came free - though no longer in a useable state .. lol! > >Closer inspection showed that the drawer had become welded to the rack >(both being plastic) in one corner. No chance it was down to anything >other than the, evening, sun - but it made me very aware of how much >these lights can focus sunlight, and how hot the focal point can get :-( > >I'd guess that most people will not experience this effect, unless - >like me - they have something quite close to the roof light .. but its >certainly worth checking out.
I've heard tell that this problem can occur only if the bullseye is incorrectly installed, which is a common mistake. AIUI, the bullseye should be installed with the curved (convex) side *down*. This lights the interior better, by dispersing the light. If the bullseye is installed the other way up, it concentrates the light (and heat) on a point in the interior. Again AIUI, people tend to install them upside-down because that way water can't accumulate on top of them and eventually leak into the interior. Adrian
