Motorhome Construction materials?

[Mickydripin]

JudgeMental - 2010-07-13 10:38 PM

 

Mickydripin - 2010-07-13 9:34 PM

 

I have stated a fact from a dealer you know the people that sell the vehicles that dont admit to anything normaly

 

 

A fact is it. Was this the same dealer that sold you the van that you could not use for 2 years I wonder.......It seems like you never learn, what do most dealers know about motorhome construction, most are just salesman, could be selling you anything.

 

Your contributions on this subject would be laughable if not so downright stupid

 

So my contribution on this subject is laughable and downright stupid plus that I never learn and to think that I would go back to to the same dealer

thanks for your acid remarks if you can not put something more usful in your posts then why not through in a few insults.

Yes I have been in litigation over my motorhome for near on three years and yes it has caused my wife to have a breakdown and made myself ill but it was not down to stupidness and that I never learn and non of it has been laughable.

I purchased my first motorhome and stripped it all out and refurbished it from top to bottom then put it in exchange for my new van I do not call myself an expert but since my problem started with my new van I have had to cope with importers,large motorhome builders,Fiat UK and dealers to try and get a conclusion to my problems with some great help from Brian so I do not include everyone in my Moron Quote sorry to other members that have come up with some good advice and care for me.

My Quote was for you Judgmental as you took my problem that I have talked to members about on other posts and have made me out to be stupid I think that I should back off from this site because if people like you only want to hold what people have said in the past when they are down and then use it to insult them then get your kicks somewhere else.

 

Thanks to all the other people that have endevoured to help me and given me encouragement to carry on in the past but I feel that I must sign off. BYE. Mike

[Guest JudgeMental]

Stick around Mickey and stop being such a drama queen for pitys sake...... :-D

[kevina]

Coefficient of thermal expansion of grp is about 0.000016/degree C.

So, say roof temp rises from 10degreesC to 50degreesC we have an expansion of 0.6mm per linear metre, or in other words 1.5mm across the whole width of the roof. NOT MUCH considering the radius at the edges.

 

I have a rapido with a floating roof and I'm very happy with it

 

Stress Free Kev

[olley]

Hi mines a single sheet of fiberglass bonded to 3" of polystyrene foam, which in turn is bonded to 2mm ply, 28'x8' all winnebago's are built this way, and have been for years without any problems

 

Olley

[roger20]

Having been round the factory a couple of times I can confirm that Autotrail also build with a floating roof.

[silverback]

Ken, sorry cant comment on the frame of your MH, i would hazzard a guess at ply with polysterene and ply again (but just aguess)

Kevin, i think you might be atad OTT with your calcs its 0.0006 mm (micron) so lets say an 18 square mtr roof you have expansion of 0.01152 (micron), thats why the sealant does not give, because it is negligable, if it was to expand 1.5mm the seals will split (i will stand corrected and open to comments if need be)

my van is rollerteam 2001 (CI) it is alum all over apart from the overcab section which is GRP, the roof is "floating" and at the back where it bends down this part can be pressed in, now the side walls are overlaping each other halfway down thus allowing for this "expansion" all around the van, so i suggest the panels are "nailed" down to give rigidity around the edges, because the expansion is negligable, but the roof is left floating cos the temps on the roof can get hotter than anywhere else (i will stand corrected if proved otherwise :-D )

Mike, time to come back :D

jonathan

[kevina]

Hi Siverback, I'm confident my calculations are correct as I've had to calculate expansion of aluminium and steel mould tools. Incidentally aluminiums expansion is about 50% greater than grp. It is the coefficient of LINEAR expansion we are looking at, not area.

 

My rapido floating roof raises a little in hot sun on one side, but that would be taking up a maximum of 0.7mm expansion with a 40degree rise (which is unlikely to be exceeded, or even equalled).

 

The 1.5mm will be lessened by subtracting the effect of any expansion of the underlying structural roof - not even going there!

 

Kev

[crinklystarfish]

Given the seemingly fairly common non-laminate construction technique of separate frame / inner skin / insulation / outer skin, does anyone have any definitive manufacturers’ recommendations regarding such a roof’s capability to be walked on? I imagine it’s a matter of luck whether footfall would be on the frame members, and for the occasions it isn’t, 70-100Kg through a contact area of a few square cm intuitively seems pretty harsh treatment for non-laminated skins. Also, sorry for referring to them as ‘flappers’ not floaters, just had a senior-ish moment – didn’t even realise I’d written it. No offence intended, completely accept there’s no flapping going on.

[kevina]

Just to clarify, the Rapido's (and others) floating roof is an addition to the conventional 30mm+ laminated roof, the idea being that all those potentially leaking roof seams are under a waterproof "umbrella" as it wraps 6" down around the edges.

 

I can see where the heki intersects with an apparent internal joining strip that there is a steel reinforcing piece bonded across the inside of the join. This infers that the (laminate) roof is effectively a one piece moulding and the seam lines seen inside are just because the inside material is only available in 120cm (or whatever) wide sheets.

 

I'm 11st and can walk on the roof quite happily though I've noticed that if I stand inside my Rapido (away from cupboards etc) and push up hard on the roof I CANNOT see any flex but that some other brands DO flex, so beware!

 

Kev

 

[silverback]

hi Kev, you are indeed correct, so i take my statement back, i went to work today and calculated it correctly *-) (i should be ashamed !! me being an engineer an all 8-) mind you its been 35years since i used them calcs at college!!) :D :D

jonathan

[silverback]

Crinkly, i dont have definitive answers from the manufacturers, but i can tell you im 102kg and mrs silverback is 50kg and weve both been on the roof cleaning etc no probs at all, you can feel it squash but when we got off all was back in place :D

jonathan

[Brian Kirby]

So, some manufacturers use a full bonding technique for the roof, and others don't.  Why bother?  The only reason I have heard for not fully bonding glass fibre sheet is that it is not smooth on the back, so does not bond reliably.  That too may vary, depending on the manufacturer of the fibreglass sheet.

Roofs that are designated for traffic (no, walking on, not HGVs, please pay attention, this is technical stuff. :-)), which not all motorhome roofs are, seem generally to have ply top and bottom to act as a stressed skin, with a (usually) timber frame with some expanded plastics thermal insulation infilling the frame.  It is a bit of a waste of time trying to bond material to the insulant in the interests of gaining strength, as the insulants are inherently weak in all aspects, i.e shear, tensile and compressive strength, so if the panel is stressed and the bond is good, it is the insulant that fails. 

As ply is mainly smooth and the reverse of fibreglass sheet is stated not to be so, it seems the best that would be achieved is a partial bond that would presumably, given thermal stress, expansion (therefore shear) stress and vibration, be inclined to de-bond over time.  This may be why the European manufacturers using fibreglass sheet roofs have adopted edge fixings only with a loose-lay sheet.  The sheet will be mechanically fixed around its periphery, which should ensure it absorbs the expansion stresses at these points internally, without moving, while remaining free to move laterally and longitudinally between the fixings.

Adding sealant where there is no actual failure may not be a good idea, unless you know what sealant was used in assembly, and use more of the same.  These are complex chemical compounds, and are not all mutually compatible.  Adding sealant where there is a failure is similarly problemmatic, since the only reliable way to cure such failures is to completely remove the failed sealant, and re-make the joint as from scratch using the same sealant (generically) as originally used to ensure there is no adverse reaction at the interfaces.

I suspect the Challenger/Chausson structure is timber with ply/MDF skins, possibly without a backing skin on the walls, but likely to have a ply backing to the roof.  If the recommendation for fitting a roof access ladder, or roof bars, is to plate the roof for reinforcement the roof is probably not ply faced under the fibreglass, and so should probably not be walked on.  However, the only people who can tell you definitively are the importer/manufacturer, or any repairer who has mended a large foot-sized hole in the roof of a similar van.  :-)  If unsure, therefore, check with the manufacturer/importer, don't ask us, these things can change from van to van, and from year to year, as well as from manufacturer to manufacturer.

[Keithl]

Hi All,

 

Auto-Trail also use a floating fibre glass roof and they say it is safe to walk on as it is laid over a bonded roof structure.

I have found a photo of a vehicle prior to having it's roof fitted on the ATOC website for anyone who may be interested.

 

Keith.

[silverback]

hi Keith,

yeh thats interesting(to me anyway! not the missus!)

gonna have to go on an open day at a factory sometime!

im into that sort of stuff 8-)

jonathan

[roger20]

Good post Keith. I was just about to do the same with a photo from my visit.

 

Having recently walked on my roof I was suddenly worried because if you look at how Autotrail build, there is a central section of plywood sandwich construction which will be safe to walk on until you reach the overcab moulding.

 

HOWEVER, either side, up to the side walls, it is only polystyrene blocks, which on the ATOC photo have yet to be inserted, and walking in this area, which I must admit I have done regularly (until now!!) is not to be recommended. I don't think that Autotrail put any plywood over the polysyrene blocks but stand to be corrected.

 

The ATOC photo looks to be a Chieftan or other similarly long type but my Tracker is built in just the same way.

 

The moral must be that unless you are quite sure just how the roof has been built, walking all over it might not be recommended.

[silverback]

comprehensive as i would expect Brian :-D good un

my van has a ladder, and roof bars all the way round but not on the overcab

Sooo im only assuming that the roof is strong enough 8-)

maybe as Brian says ...check with manufacturer

been to BSB (british superbikes) and there are folks on there van roofs watching the racing not just 1 but 4..5...6 peeps so they are either unaware or not bothered (!)

jonathan

[Minstrel]

JudgeMental - 2010-07-14 12:27 PM

 

Now I know this will probably not help some of you, but this is te reply I have just had from Euramobil on the topic:

 

"Yes it is absolutely right that the roof is only fixed on the borders and the center roof is floating, we built our vehicles like that for many years and there is nothing to worry about.

 

Also other manufacturer built there roofs like that which gives important advantages concerning the extension of the glass fibre material. The glass fibre works with the different temperatures (you might have seen that your roof might have lifted up on some occasions) and in case it would be fixed with the sandwich roof those extensions would also affect the other material which it doesn’t do whilst it is loose.

 

Yours faithfully

 

Customer Service-Guarantees"

 

Thank you Judge for words of wisdom from Euramobil. We got home from a weekend away and looking from the landing window I saw odd bumps on the top of our Euramobil. I worried, took a photo, then came to the forum and found this thread. I am much relieved to find there's nothing wrong with the roof.

 

This is the sort of thing that makes the forum invaluable

 

Thanks

[eunicewalter]

Somehow, that mostly happening, just monitor if it will crack, otherwise you need to make another one with appropriate materials needed. DO not put any excessive bonds on it as sometimes it will cause to bubble so some areas that bump up.

 

[PJay]

THREE year old post. !!! revived

 

Looks like a commercial post at that!!