Cirrus Custom XL
6.3M AND 7.3M RIBS ON TEST

In addition to established innovators such as Mark Pascoe and Scorpion, designers and professionals from other commercial walks of life outside the marine industry are now beginning to take an interest in the RIB concept’s marketing potential. One such example is that of Cirrus RIBs.

On the day of our recent visit to the company’s yard in Portland I asked Sebastian Gowar-Cliffe, Cirrus RIB’s principal, to describe the background to this new project – seen for the very first time in the UK at Southampton International Boat Show last September.

History/background
The most striking thing about Cirrus RIBs is how radically different they look compared to conventional RIBs or even sportsboats. I know that you are an industrial designer, but you have never designed a complete boat before. How did you arrive at this design and why?

I started out with very specific requirements for Cirrus boats. Firstly, They must be safe, practical, secure family day boats. Secondly they must be truly modern in appearance. Thirdly they must have a high quality of fit out and finish. A further consideration was that they must, if possible, appeal to buyers who are already aware of the superiority of the RIB hull as well as buyers of conventional hard sportsboats, particularly walkrounds such as Boston Whalers. The most important technical requirement was that the design should be modular, allowing us to build several lengths and engine configurations.

I remember seeing your early design sketches and a prototype when you started this project in 1997. You have advanced the styling a long way since then. Are you wholly responsible for this design?

No. I brought in John Moxham to design us a hull, and a team of automotive design consultants to work with me on the superstructure design and engineering. I wanted to start with a clean sheet of paper. The brief was to create a modular design that would include lengths from 6m to 8m and a full range of inboard and outboard engines. I gave the team a very detailed brief which defined payload, engine configurations, seating, deck space and console requirements. I controlled the engineering of the modules that allow us to build different versions of the RIB but I took a back seat in the styling of the range. Initially we had six designers competing against each other but gradually whittled them down to one. Some proposals were impractical but both I and my business partner, Adam Cars, decided to go for the most radical of the feasible designs as inevitably the more extreme details become softened as the design approaches production.

You are one of the first manufacturers in Europe to wholly design and tool a small boat using CAD/CAM. It’s an expensive process. Did you find that the investment was worthwhile?

Without a doubt, from a clean sheet of paper to a finished boat took ten months. The process is relatively new to laminators in the UK and we had some teething troubles, but without these we could have done it in seven months and you must remember that this is not a simple boat to build. Using 5-axis milling to machine the plugs allowed us complete freedom in designing every detail of the RIB and we were able to include shapes that would be too expensive and difficult to make by hand: the console back, for example.

I’m sure that other UK boatbuilders will be looking closely at your use of CAD/CAM. Apart from speed of model development, what other major advantages are there.
I think that the two main advantages are the high degree of accuracy of the plugs and freedom to design any shape or surface. The symmetry and accuracy of mouldings takes from CAD/CAM allows us to CNC machine a lot of our smaller components such as console facings and locker lids. We can guarantee accuracy of fit. I would certainly use the process again but I would involve our glass fibre mould makers at an earlier stage to guarantee correct flange design on the mouldings.

Why did you choose John Moxham for your hull design?
I have a high regard for John’s work and I felt that his subtle curved spray rails, although tricky to produce by hand on a small hull would be relatively simple to carve on a 5-axis milling rig. I asked him to produce a good load-carrying hull rated at around 50 knots. John works on paper so we had to digitise his drawings into our computer modelling programme but that was a minor problem and the final accuracy of the hull plug was excellent.

The design is modular and you are already building different lengths with different engine installations but how does this work in practice.

The hull has a conventional insert to create 6m, 7m and 8m lengths but the deck is made out of fore and aft sections that slide over each other and are bonded together to create the superstructure. The seating modules are then bonded into place to complete the ‘bodyshell’. The rear deck moulding can be formed with or without the outboard well. When the well is not moulded the deck is designed to receive an engine cover for the inboard versions. This concept allows us to build many different length and engine configurations from the same set of mouldings and it could only have been achieved in the time available using CAD. The reason that we have gone to the expense of building the first three demo boats is to ‘showcase’ this technique and demonstrate a good cross-section of the possible configurations.

FirstImpressions
I first clapped eyes on these boats on the day of RIB International and Motorboat and Yachting’s invitation to trial the three prototypes out of Weymouth harbour in deepest Dorset. ‘Original’, was the first word that came to mind followed in quick succession by further thoughts of ‘quality’ and ‘retro’. The latter because the styling in the aft section of the inboard version in particular is classic 50’s American automobile - sumptuous, curvy, sexy.

Straight lines are popular in the mass boat market for no other reason than they are easy to produce and inexpensive to manufacture. To construct a craft with as many styling curvatures as the Cirrus is extraordinarily expensive and time consuming. It also, very often necessitates specialist manufacturing, or at the very least, a huge amount of man-hours. Whichever the case, the Cirrus appears to have managed it very convincingly indeed. Furthermore, these additional labours mean that the product would sit comfortably along-side the best of luxury hard sports boats like that of Shakespeare and others.

A common failing with some leisure RIBs, particularly the ‘blue-water’ variety, is that all the R&D is spent above the water line with little left over, it seems, to invest on the vessel’s ‘under carriage’ ie. the hull. Let’s face it, without this latter component being of quality everything else becomes pretty much a waste of time - like a costly house being built on a poor foundation. However, in the case of the Cirrus, it’s possible to tell by just by looking at the craft at rest that it possesses a proper sea going hull. Stood by the marina side I could feel my anticipation and interest growing.

FitOut
These RIBs have more than obvious leanings toward the high end, super-yacht tender market. In fact, the dimensions in particular of the 6 metre model, have been borne with this consideration in mind. All three versions feature generous locker space and most importantly, ample seating.

One of the most notable features of the Cirrus’s internal fitout is the reverse angle of the seating bulkheads. With virtually all other RIBs I have seen, the GRP structure, which forms the seat face, possesses a vertical face. But with this design a huge amount of extra foot room has been created and hence moving about on deck becomes very much more comfortable and easy. On board security is good with the height from the deck to top of the hypalon tube being well suited to accommodating children safely. Furthermore, the boats have a non-slip boarding section atop their gunnel/sponson which affords yet further safety. The outer perimeter seating configuration works well although the rear seating position is obviously the place to be if at high speed the going gets lively. That said, there are plenty of handholds for the passengers to utilise. It was my opinion that the comfort and appearance of the seat cushions would be enhanced further still if they were more ‘deep pan’ and less ‘thin crust’. (A fool-proof system of securing them also needs to be found as on the day of test we lost several cushions over the side due to the temporary fastening method employed.)

The integration of teak decking, whilst being practical, really sets the whole look of these boats off. Indeed, it’s clear that the aesthetic appeal of each detail throughout the boat has been subjected to the close scrutiny of the designers. A good example of this is the ‘Oval 316’ mirror polished stainless steel work. It really is sturdy and seamanlike but also very original in its overall styling.

The helm point on all three prototypes is occupied by a simple bolster support which is well suited to yacht tender use as it assists the ‘cox’ in having good all round visibility. Additionally of course, this option takes up the least amount of deck space - an important consideration if the craft is to be used as a people carrier. The instrument console is yet another example of the ‘non marine’ approach to the styling of this new range. Finished in a ‘Corian’ type material, it’s fashioned as a flat panel and in this respect carries contemporary influences hailing from the latest in flat digital monitor computer screens. It’s certainly functional, benefiting from having lots of panel space plus the unit is totally waterproof. The console offers a small degree of protection from the elements but it is probably set a little high for some at present. (I was assured however, that the height of the unit could be customised according to the customer’s specific requirements, as could other items such as the client’s preferred choice of helm seat.)

Other aspects worthy of mention. A reasonable sized anchor locker in the forepeak - though the lack of a bow runner may prove troublesome here. Access to the boat’s various cleats, pop-up and otherwise, can be made comfortably and without too much stretching. The RIB’s scuppering ability is fairly typical of a boat of this type and is adequate for everything but very rough water offshore use. The engine housing to the inboard version is well thought through, offers good access and ensures a high degree of protection for the diesel installation.

Hull
The boat has a very level profile in the sense it possesses little sheer in the bow, plus if anything, the particular shape of its GRP topsides accentuate a turned-down appearance in the RIB’s forward section. The deep-vee hull nevertheless has a very high degree of lift in it and hence at no time did I feel that any one of the three boats tested would stuff its nose in a moderate sea state. The pronounced spray rails do a good job at throwing the water well clear of the hull and therefore help reduce its wetted area very efficiently.  Designed by the well known naval architect, John Moxham, and developed from his original Osprey ‘Lynx’ design, which in itself was a highly successful RIB for many years on the RIB race circuit, the hull boasts a full 23 degrees deadrise coupled to 15 degrees of angle at the transom.

Performance
These boats currently have a 50 knot rating and all models tested cruise comfortably in the mid 30 knot speed band. Though each of the prototype test boats featured a very different type of engine, (4 stroke, 2 stroke and inboard diesel,) at the same time, all felt well balanced, stable both at rest and at speed, responded well to trim and stuck to the water like a leach. This latter point was very noticeable and ensured the boats were a joy to helm from a sports/performance perspective. What a difference a really good hull makes not just in terms of efficiency but in terms of comfort too. Thus the Cirrus range could rightly be viewed as genuine sporting craft as opposed to purely tender/people transporters. In the rough, their natural planing attitude was good and even when the trim was adversely applied, each boat remained safe and surefooted. I found also that these RIBs inspired confidence and for that reason would, I’m sure, prove popular with many who were not so familiar with going to sea in a powerboat.

I’m not sure that when driven at speed the straight bolster back support to the helm point offers enough security for the ‘cox’. Plus the throttle control requires one to maintain an outstretched arm. Reposition the latter to bring it more to hand and modify the bolster to a wrap around/horseshoe shape to include lumber supports and immediately a substantial improvement is made to the benefit of the ‘cox’ and his crew. If such was attended to one could more readily drive the boat hard and to its full potential in a strengthening sea state -  something which is fundamental to the joys of ribbing.

I didn’t necessarily find the Cirrus to be the most exciting RIB I have ever driven, but bearing in mind the markets for which these boats are intended, I feel the matters of sea keeping, stability, surefootedness and overall balance are met to a very high degree. This is clearly a breed of vessel capable of a great deal more than just looking pretty afloat in a marina berth. Furthermore, the range has the potential of being a very excellent ambassador for the RIB market in general hence it’s my hope this bold and innovative venture succeeds.