Additional Floor Support
As many of you will know, Lunar caravans, in particular, suffer from floor joints moving. The suggestion is to fix an additional support under the area where the floor panels meet. The ‘recommendation’ is to use a piece of marine ply to do the job. This may be a many times recycled answer but why is marine ply considered the best? Contrary to what many may think, marine ply is not waterproof, it is merely the glue sandwiching the layers of wood which is waterproof. So with this in mind, is it actually better to use a piece of solid timber rather than ply? The underside of a caravan doesn’t get particularly wet, even when towing in the rain so there shouldn’t be a problem, providing the timber is suitably treated beforehand. Softwood is the cheaper option but would hardwood be significantly better? I ask the question because it is a job I have to do and just happen to have a piece of very old mahogany of a suitable size. I don’t really want to use it but will do if there is a substantial benefit.
Comments from those that have done the job and/or any timber experts out there will be very welcome.
Comments
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I suppose Marine Ply is always mentioned because of the glue used but surely exterior plywood could work as well, especially if it was coated with a waterproof paint? Perhaps ply is suggested because for a given width you don't require as much depth?
David
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I would have thought that any wood reinforcement would have to be of a fairly large cross-section in order to be of much benefit. The extra weight of such a reinforcement could reduce the available payload quite considerably. Perhaps extruded aluminium sections would be lighter and do just as good a job. Besides, they wouldn't have to be treated in any way to prevent possible rot.
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Whilst I fully accept that plywood is generally stronger than solid timber, the question has to be "what strength is actually needed to effectively support the caravan floor?" The movement between the floor panels is very small, an estimated 2mm with 80kg standing on the edge of one of the panels. This suggests that excessive strength is not actually needed. I suppose I worded my original query a little wrongly. I should have really asked why is MARINE ply considered the material to use as opposed to standard plywood or solid timber.
As stated in my original post, I have a piece of mahogany, left over from a previous project. It is 12mm thick and of a suitable length and width to do the job. Looking at technical details for mahogany I am even more convinced that it would be suitable for the job. If left untreated mahogany has a life expectancy of 30+ years. It is stronger and more durable than oak, has unusual resistance to moisture and atmospheric changes and is unlikely to twist or warp. The weight, as queried by Lutz, is quite negligible in the scheme of things. It will be less than 1.5kg and probably less than the suggested aluminium section. It will also be positioned over the axle line.
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