Brian Kirby Posted July 16, 2012 Share Posted July 16, 2012 This is the large circular, double glazed, rooflight, that surmounts the "beam me up Scotty" shower enclosure, as fitted to a number of Hobby motorhome models. Our Van is 2007. I recently noticed when away in the van, that water had entered the cavity between the two skins of the rooflight, resulting in heavy condensation in the cavity, and also in beads of water rolling around within the cavity. We have never used the shower. The circumstances were of a hot sunny day (remember them? :-)) followed by a sharp shower. This seemed to be a one-off, as the water and condensation subsequently gradually evaporated, and has now gone. However, there is no logical, visible, means of water ingress to this void, so I was puzzled as to how it had entered, and had a look on the outside when we returned. I was expecting to find damage, no doubt caused by one of those invisible flying objects that cause occasional sharp bangs as we drive along. To my surprise, the exterior of the rooflight was completely intact and undamaged. But on closer examination I noticed numerous hairline cracks along the line of the joint between the inner and outer skins of the rooflight. These cracks are radial and range in size from 2-3 mm long up to 12-15mm long. Among them were a few circumferential cracks up to 20mm long. The area affected is approximately one quadrant of the rooflight, the remainder presently being unaffected. I clean the roof of the van 1 - 2 times per year, in the process cleaning the rooflights and, although the cracks are not immediately apparent on a casual look, I do not think I would have missed them as they are now. However, I suspect they must have been "germinating" for some time. The cause, I imagine, will lie in the way adhesive was applied to bond the two skins together. The rooflight presently remains clear of condensation despite the almost continual rain, and my theory as to how/why the water got in is that the outer skin had expanded during the hot sunny day (it is both tinted and fritted, so it gets quite hot) causing the cracks to open, allowing the expanding warm air inside to escape, but was than rapidly cooled by the shower, causing the air in the cavity to shrink rapidly, so sucking in rain until the outer skin shrank back to its original size and the cracks closed again leaving it watertight. Something similar can occur at the end laps of sheet lead roofing. Of slightly greater concern was the thought that, since the cracks were not present originally and had developed, they would go on developing, potentially to the point at which the outer skin of the rooflight could detach from the inner. The inner skin is restrained by catches, but were the outer to detach there would be nothing to prevent it flying off. As it is a good 600mm in diameter, that thought, on a crowded motorway at 60+ MPH was a bit worrying. I took photographs of the condensation and the cracks and, although the van is now only two months from the end of its 5 year water ingress warranty, Hobby have agreed that this failure amounts to water ingress, and have agreed to replace the rooflight. Not, I suspect, a cheap item if I had had to pay for it. Well done Hobby! The point? I suggest anyone with a Hobby motorhome, of whatever age, that has this large circular washroom rooflight, closely examines its exterior for cracking along that joint as soon as they reasonably can. It may be that mine is a complete one-off (let's hope so), but there must also be the possibility of a batch fault, or even that this is the result of incorrect specification that will affect all such units over time. Even if yours is now out of warranty, if it is cracking unseen, there remains the risk of it flying off on the road - so IMO worth checking. Link to comment Share on other sites More sharing options...
euroserv Posted July 16, 2012 Share Posted July 16, 2012 Brian, That is amazingly coincidental! I was driving up the A1 near Doncaster on Friday evening and was about to pass a Hobby motorhome that was 2006 registered when i noticed some debris removing itself from the roof. It did look very much like parts of the roof-light and was about two thirds of the way down the off side of the roof. It had completely gone by the time I passed the vehicle and considered myself lucky not to have been hit by or run over any of the parts. Perhaps they had left it open and the wind had gotten under it, or maybe it had a fault as mentioned in your observations, but If i was the owner of one of these vehicles I would be having a look..... Nick Link to comment Share on other sites More sharing options...
Brian Kirby Posted July 16, 2012 Author Share Posted July 16, 2012 Hi Nick. Coincidence indeed! I suppose he might have experienced "a bridge too low", or even had something drop onto the roof that you saw un-dropping! :-) Still worth checking, methinks, just in case. Very nasty if it hit a motorcyclist! Link to comment Share on other sites More sharing options...
Robinhood Posted July 16, 2012 Share Posted July 16, 2012 Thanks for the 'heads up' Brian. I'll check when I get back home. Currently well North of the jet stream, but looks like I'll have to head South again when it's repositioning to normal brings 'business as usual' weather back to Scotland. Edit: BTW my only consolation would be if it hit a motorcyclist ;-) Link to comment Share on other sites More sharing options...
Brian Kirby Posted July 17, 2012 Author Share Posted July 17, 2012 Robinhood - 2012-07-16 10:42 PM...................BTW my only consolation would be if it hit a motorcyclist ;-) :-D :-D Link to comment Share on other sites More sharing options...
Gwendolyn Posted July 18, 2012 Share Posted July 18, 2012 Thanks for the warning Brian. Had a really good look at ours and all seems well at the moment. But something to be watched in future. Would be interested to know if anyone else has experienced the same problem. Hobby have been good to you though. Nice to know that. Link to comment Share on other sites More sharing options...
graham boyd Posted April 29, 2014 Share Posted April 29, 2014 same problem Brian, after removing my outdoor cover, I was on the roof, I noticed the whole outer shell was lying loose on the under skin. As you have mentioned it is the bonding, I have rebonded it myself with 3m windscreen glue. this seems to have done the job. luckily spotted this before driving off. see my thread blown out front window. greetings from Holland Graham Link to comment Share on other sites More sharing options...
Peter Pan Posted May 23, 2018 Share Posted May 23, 2018 Hi Brian. I wish I had read this post 2 weeks ago. The outer skin flew off our 11 year old Hobby Van on Monday. Fortunately it did not cause any damage to following traffic. Looking at the construction off this roof light I would say the outer skin is certain to come loose at some time in its life. Hobby say they can obtain a new assembly costing £780. Link to comment Share on other sites More sharing options...
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