Trans RINA, Vol 155, Part C1, Intl J Marine Design, Jan - Jun 2013 DISCUSSION
EXPANDING THE ABILITIES: DESIGN DEVELOPMENT OF WHEELCHAIR- FRIENDLY CATAMARAN
A Nazarov, P Jabtanom, A Leeprasert, P Suebyiw and P Phormtan Albatross Marine Design, Thailand
COMMENT Dr J Kecsmar Ad Hoc Marine Designs Ltd, UK
First, I would like to congratulate the author on bring to light the difficulties faced with such a unique challenge. I am sure Colin Mudie would be pleased to see the gauntlet of designing for disabled sailors taken into the small power yacht arena. There was no reference to the ‘Lord Nelson’ nor the later ‘Tenacious’ by T. Castro which could be considered the pioneers of such designs for the disabled. Much use of referencing to ISO is to be commended, but experience from these previous designs would serve a more useful guide. Since as the author points out, these ISO standards are somewhat lacking to begin with. A comparison of lessons learnt from these designs alongside ISO would be very instructive.
The author raises very good points on the marina side of access. It does appear this side of the boating has been somewhat overlooked beyond the toilets and restaurant access. This deserves a review in its own right, to facilitate the disabled sailor between leaving home to boarding their yacht. It is easy for an able bodied person to walk up an angled linkspan when the tide is low, yet one would image next to impossible for one in a wheelchair.
Could the author detail the reasoning behind the permanent use of an able bodied sailor on board at all times. The logic and hence compromises behind this would be most
interesting, versus lack of independence.
Figure 7 is most interesting especially when noting the lower roll amplitudes reference in the text. Roll amplitudes of catamarans are lower than equivalent monohulls. Yet the accelerations for catamarans are higher owing to their natural periods being less than an equivalent monohull. The roll and pitch periods are much shorter for catamarans of this size and thus I would consider to be worse in that regard than a monohull when reviewing for Motion Induced Interruptions (MII) or even the Lateral Force Estimator (LFE; which should be the primary indicators rather than just vertical accelerations. The lateral, sideways, accelerations can be significant. I would image the use of bilge keels to facilitate a more benign motion would be beneficial.
Assuming the wheelchair depending coxswain is able to get off and on the toilet, it would be assumed that he could also get off and on a correctly designed helm seat. Mounting the helm seat on a swivel plate could facilitate ingress/egress.
The comfort aspect is more important for someone who not easily gets out of the helm seat. Also when you cannot use your legs to brace yourself under impact the shape of the spine while reclined is even more crucial. Wheel chairs given by default a very poor posture for the spine. This is because they are primarily designed as means of transportation and not for optimising comfort, posture or distribution of load. They should hence not be used as helm seats if it possible to avoid it.
It appears the author is sufficiently well versed in the current ISO standards to put forward recommendations for a ‘small disabled recreational craft rules/guidelines’ incorporating all the findings of the authors studies and solutions. Sill heights,
for example are clearly
impractical as noted. An equivalence of safety should be the raison d’être of such a new code for such craft, rather than continue with anachronisms which, in this case, render the craft not-fit- for- purpose.
One final point, there was no mention of evacuation and how this
important
concluded, especially in the situation where one hull is damaged or flooded.
Dr J Ullman, HSBO Pro, Sweden The “HandiCat”
concept (Design Development of
Wheelchair-Friendly Catamaran) presented by Albert Nazarov et al is brilliant concept developed with a thorough analysis user interfaces.
The catamaran is of course also the natural choice of platform for this kind of application, as they produce less slamming and healing than mono-hulls.
Prompted by the editors / Technical director of RINA to comment on the article, I hereby suggest a few aspects possibly worth considering.
In most large marinas mooring is done with the stern to the key.
Hence the gangway should probably run from the stern and be well designed to be able to compensate for differences in height.
considering the benefits
There should probably be a helm seat designed for optimal posture and comfort and fitted with armrest that can fold away for easy ingress/egress and sturdy enough to the take weight of a person.
safety aspect was addressed or
©2013: The Royal Institution of Naval Architects
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