Post by Mary FisherI have no experience of GRP on 'vans or cars and doubt that I ever shall.
But this reply has raised some interesting points which I'd like to know
more about.
Post by David HalleyMost new aluminium vans have GRP or ABS front panels, and part or
full
Post by Mary Fisherrear
Post by David Halleypanels of similar make up.
I didn't know that any new vans were made of aluminium at all!
Post by David HalleyAll GRP vans have aluminium roofs and some have aluminium upper rear
panels.
I didn't know that either of course.
I'm not denying it, by the way, just admitting that I don't know everything!
Post by David HalleyGRP is slightly heavier between 10 and 20kg and slighly more
expensive due
Post by Mary FisherWhat's the point of decals?
Post by David HalleyGRP has been in the mainstream touring caravan arena since 1995 and those
vans are not showing any crazing, yet.
GRP has been in motorhome manufacturing for much longer and, yes, I have
seen some crazing, but only on very old poorly maintained vehicles.
How do you maintain GRP to stop it crazing?
Mary
Mary,
Post by Mary FisherI didn't know that any new vans were made of aluminium at all!
I've discovered that most new British-built caravans have sidewalls that
are constructed from panels that can best be described as a three layer
sandwich: the 'filling', if you will, is a structural or semi-structural
wooden space frame the spaces of which are packed with thermal
insulation, typically cut polystyrene sheet about 20mm thick. One side
of the sandwich filling is bonded to thin plywood; covered in decorative
fabric/veneer it becomes the inner wall of the caravan. The other side
of the sandwich filling is bonded to a thin weatherproof skin which
forms the outer surface of the caravan. It is the nature of this
weatherproof skin that was the original subject of this posting. Most
newly-built British caravans use very thin (1.2mm or so) enamelled
aluminium for this outer skin. Overall the sidewall panel thickness is
typically around 25mm.
I may be wrong, but as I understand it the more durable Continental
caravans like Hymer do not have a structural wooden space frame. Instead
they use substantial marine plywood for the inner wall. They still use
thin aluminium for the outer skin but not requiring a structural space
frame enables them to fill the entire inside of the sandwich with
polyurethane foam. Not only is the thermal insulation better but so is
the waterproofing: if the outer aluminium skin is damaged water still
can't get in because there are no gaps in the foam. The rot proof
polyurethane foam is non-porous and fully bonded to the marine ply on
one side and the aluminium on the other, so even if water seeps in
around a window it is trapped right there. I assume this can eventually
damage the marine ply in the immediate area but I would have thought a
damp check would pick this up long before anything serious occurred. The
beauty is the problem is localised and can't spread into the structure
as it does in British models. As you can probably tell, I consider this
to be a superior method of caravan construction but it does have a major
disadvantage: weight. The thick marine ply inner wall which gives the
caravan its strength and longevity also increases its weight; so much
that most cars can't tow it!
I've heard that one Continental company are now trying out a composite
alternative to aluminium and GRP for the caravan's outer skin but I
don't have any further details. Personally, I'd like them to find a
light weight alternative for Hymer's marine ply.
As you can tell, although I'm new to all this I have been doing some
research -- I thought I'd share.
Regards, Stewart