Strong, Modern, Aerodynamic, Resilient and Tested are the words behind the acronym 'SMART'. They refer to a construction system that denotes a significant investment by Swift in its next generation of touring caravans, on sale from 1st September 2013.

Four years ago Bailey introduced its Alu-tech system and then, last year, Elddis brought out SoLiD construction. Each was revolutionary in its own way and both were aimed at preventing water ingress to the bodyshell. Bailey went a step further and decided that, if water did ever get in, it should not be able to cause any damage. To this end Alu-tech roof and side panels are constructed without the use of wood.

Elddis opted for a system where water 'just cannot get in' and retained wood as the most suitable material for its bonded construction. Both Bailey and Elddis dispensed with more than 90% of the screws previously used to hold the bodyshell together.

With SMART Swift has adopted a somewhat different approach to its competitors. For the first time all the structural timbers in the bodyshell have been replaced with a specially developed polyurethane product, which Swift has christened 'PURe'.

The use of polyurethane in place of wood is new to Swift but not to the caravan industry in Europe; being employed in part by Tabbert, Fendt & Hobby. However Swift believes it is the first to use the product so extensively. During construction it's easy to spot, having a dark grey appearance.

Whilst polyurethane has been around a long time, only in more recent years has it become viable as a structural replacement for wood. One major benefit is the closed cell structure that makes polyurethane totally impervious to water. It can also be made light with a density similar too or less than wood.

Behind the protective screen lies part of Swift's huge new routing machine

One of the problems with wood is that its strength varies from piece to piece and is affected by things like knots and grain variation. A wooden bodyshell therefore has to be somewhat over engineered to cope with these variations.
Being an engineered product, the properties of PURe can be very accurately predicted. It can also be manufactured to different densities according to the requirements of each component. The net result is that the bodyshell can be designed to fine tolerances, saving 10-14kg in weight without any loss in strength.

router
Inside Swift's amazing new machine

Other material possibilities such as blown polystyrene and blown PVC were considered but were deemed to be inferior to polyurethane in their mechanical properties and in the fact that they contain veins that can hold or transmit water.

A significant technical challenge facing Swift was to achieve the optimum density for each PURe component used in the bodyshell. Too dense and it becomes heavy, too light and it might fail in use. Following exhaustive laboratory testing and many days at the Millbrook proving ground, Swift settled on just two densities for all the components.

To facilitate the move to SMART Swift has invested some £1.25M in a state of the art routing machine that can process side, floor and roof panels to a very high degree of accuracy. It was custom made for Swift by German company Reichenbacher, a leader in CNC technology. The sheer size of the machine has to be seen to be believed - I reckon it occupies an area about one quarter the size of a football pitch.
Interestingly, Swift has chosen to retain screws rather than to rely solely on bonding. Technical Director Andy Spacey explained that most people like the reassurance of a mechanical fixing and the continuing use of screws aids repairability whilst eliminating the need for special training.

A partly constructed floor clearly shows the dark polystyrene components that have replaced wood

To avoid any water ingress issues the depth of the screws is carefully prescribed so as not to go right through the polyurethane. If any water does get in it can't go anywhere because of the closed cell nature of the product.

Plywood has been retained for the inner walls and ceiling but the traditional poplar board is being replaced with a hardwood variety, sourced from sustainable forests. Hardwood board incurs a slight weight penalty but is much more resistant to water than softwood. The board is also significantly stiffer, thereby aiding structural rigidity when bonded into wall and ceiling panels.
There is another important change too. For the first time the wallboard covering will be micro-porous, thereby allowing any moisture within these composite panels to escape.

Plywood is also retained in the floor construction, both top and bottom, but the edge and other battens are now made from PURe. When made of wood, any water ingress in these components could take a very long time to dry out, with rot becoming a possibility. The change to PURe eliminates this. Should the plywood itself get damp for any reason, it will dry out, with little or no intervention necessary.
Another important aspect of SMART is aerodynamics. To this end Swift has been working closely with Dr Rob Lewis from Total Sim. They are experts in computational fluid dynamics (CFD), a technology that has largely replaced wind tunnel testing. Swift now believes its touring vans lead the field in this respect.

Swift approved workshops will be advised about PURe through the normal technical bulletin procedure. Apart from the switch to a new material, the only real changes relate to the external screws (the new ones having a better bite) and the adhesive used to bond to PURe.

Curved components such as these are injection moulded by the supplier

Swift describes SMART as a marriage between established construction techniques and new, modern technology. It likens the process to a journey; a journey that already has taken several years and still has some way to go. It remains to be seen how consumers will react to SMART construction but my guess is that most will see it as a welcome move in the right direction.

Note
Development times and supply capacity restrictions are such that, for the time being, the full benefits of SMART construction will only be applied to Swift's touring caravans.