Twister 730

Tested by Erwin Bursik (January/February 2009)

THE Twister 730, surrounded by bunting and highlighted by an array of spotlights, was the focus of the Suzuki stand during the recent 2008 National Boat Show in Johannesburg. This was her first exposure to the public, and she did it in a style that complemented both her stunning looks and revolutionary hull design.

Like many others involved in the boating fraternity, I was irresistibly drawn to view this new craft, particularly as I had not heard anything about her design and construction on the boating industry grapevine.

I stood in front of her for ages, studying the configuration of her hull design — awed and intrigued by its apparent complexity and radical design. At the same time I was trying to visualise how the hull would work the ocean once at sea.

After meeting André van der Merwe and his brother Francois, and being told that the hull was designed by one of South Africa’s foremost marine architects, Bob van van Niekerk, the myriad queries that had arisen in my mind began to be answered.

Over my many years of playing with boats, I have had the privilege of having had numerous discussions with Bob and have been intrigued by his theories on catamaran hull design — and one theory in particular. He maintains that the tunnel “roof” should ride free of the water.

“You should see daylight through the tunnel when the craft is on the plane,” he once told me. Now the lifting strakes in the Twister 730’s high tunnel began to make sense.

Another of Bob’s views is that the hull design should ensure that the craft’s longitudinal seesaw point should be matched with the designed power source. This would then have the craft planing at its designed optimal angle of attack on the water. By increasing or decreasing the designated horsepower, it would have minimal effect on the hull’s performance.

For example, a hull designed for a 90hp motor would experience minimal improvement in performance if 140hp motors were substituted, other than, of course, speed at the very top-end. Over and over again I have found both of these theories to be 100% correct.

Having taken three years to get from the design stage to the completed craft, André and Francois, with the help of Global Components (Pty) Ltd in Pietermaritzburg, had completed the Twister 730 to the point where all concerned in her manufacture were proud enough to present her to the South African boating fraternity.

There and then, with no hesitation, I agreed to André’s request to review this craft. Unfortunately, the first opportunity I got to play with her on the ocean was mid-October. By that time I knew I would be reviewing both the original Twister 730 as well as George Gibb’s Inkwazi — the second hull out of the mould. George is an old friend of mine and I tested his original Inkwazi 15 years ago, almost to the day, for a review in SKI-BOAT. Again he was risking a new craft with me, and I sincerely hope he has as much joy and success with his new craft as he had on the original Inkwazi.

The Twister 730, with her 7.3m overall length and 2.95m width, falls into the 24ft craft category. As such, she is at the very upper-end of the practical towing size for trailerable boats, “practical” being the operative word. This aspect was tested and proven during her portage from Pietermaritzburg to Gauteng, then to Cape Town and back to Durban, all behind André’s Land Cruiser station wagon. During his tow from Cape Town to Durban for the review — a trip he did in two days —André said that at speeds between 90 and 110km/h it was an easy tow both for the vehicle and the drivers.

At the public slipway next to Durban’s Point Yacht Club I boarded the new Twister 730, Inkwazi, and easily slipped into the water. André started up the motors and backed her off the trailer for this craft’s maiden voyage. SKI-BOAT’s Heinrich Kleyn and Francois van der Merwe then boarded the original Twister 730 that was at moorings and joined us for the run out to sea.

The original Twister 730 is powered by twin 140hp Suzukis, while Inkwazi is fitted with twin 150hp motors of the same brand. The 150hp Suzukis were swinging 21-pitch props and the 140hp motors 22-pitch props which gave me a good indication of the difference in performance between the two. I was impressed by the power generated by these motors, especially at the lower end of the torque curve, as well as by their smooth and quiet running.

One feature of this craft is the unusual mounting of the motors on the transom. Each counter-rotating motor has its underwater unit marginally canted outwards from the centre line of the craft. It’s certainly different, and during the entire review I endeavoured to establish the need for and desirability of mounting them this way. However, it is virtually impossible to come to any firm conclusion, having not had the same motors mounted in the traditional way for comparison. All I can honestly say, as will be borne out by the rest of the review, is that the craft rode extremely well.

As Inkwazi exited the confines of Durban Harbour, I took her helm for the run out towards the horizon in a sea that had the remnants of the effects of southwesterly swells and the beginning of a southeasterly that was threatening to blow harder and harder as the day progressed.

So, with the swell on her starboard transom, I eased the throttles forward until she slipped onto the plane. I use the word “slipped” on purpose, for this is what the hull seemed to do after gradually picking up speed in the normal manner and getting to the point of coming onto the plane. I experienced this virtually every time I tried it, and it was the same on both craft.

All credit to Bob’s lifting strakes. Once she was on the plane, the craft seemed to detach herself from the power source and the suck of her wetted area. She then proceeded to glide beautifully over the calm water surface. This was not just my interpretation of her ride, but was also visible on the rev-counters and the SOG on the GPS unit.

The Twister’s stance when planing — both at moderate speed as well as high speed — is reasonably prone and especially at high speed is not greatly influenced by motor trim adjustments. I would go so far as to say that for general running up to 20 knots, trimming the motors out so they were registering about a third up on the trim gauges found her sweet spot for me. I would have her trimmed this way for 90% of the craft’s work, with the exception of full-down trim for surf work.

Indeed, during these initial runs, while I was experimenting with motor trims, I established that the hull required only very marginal lateral trimming. Was it the hull design or the canting of the motors that held her transom so tight into the water? I still can’t make up my mind. All I can tell you is that having set the motor trim, I could play at speeds ranging from 14 to 35 knots, both into and with the sea, without constantly adjusting lateral trim to correct boat-to-sea conditions.

It reminded me a little of the old, old days when the only trim was the pin setting on the transom bracket. Once set it was there permanently. Even adjusting bow-up or down at various speeds did not induce the hull to override the lateral trim stability.

During all this time, having duplicated the trials on both craft, I kept being reminded of Bob van Niekerk’s explanation, while at the same time trying to get the hull to react negatively. No go — she seemed to know exactly what she wanted to do and did it with the grace that produced a soft, even ride.

I did not really have enough rough sea to play in, but I have spoken to two skippers I know, both old sea dogs with a lot of experience, and both say she is amazingly soft when running into a big head sea at substantial speed. Whilst I accept their findings, I reiterate that I was unable to test that for myself.

In simulated surf work in the swells that were peaking over the Kinmount Bank off Durban, as well as Limestone Reef, I put her through her paces for a considerable period of time. Being a 24ft craft, one couldn’t expect her to turn on a tickey. However, I had to be sure that within serious surf conditions I would not only be able to turn her to port or starboard quickly enough, but could also pull her out of the turn and get out of the hole in time to get over the shoulder of the oncoming wave.

Through a full spectrum of trolling trials I established that right up to 9.5 knots, with her motors trimmed right in, she produced an extremely tight wake that would please even the most fastidious marlin- and sailfishing captain.

One last aspect of her performance that really surprised me was her backing-up ability. After trimming up her motors to avoid them dragging the transom deeper into the water, I found that by using only the throttles I could get her to reverse at good speed and change direction remarkably easily.

Merwe Marine and all associated with the development of the Twister 730 had obviously put a great deal of thought into the internal and deck design of this craft. In the interests of versatility, the Twister has a basic design that can be fine-tuned for the serious tuna fisherman fishing off Cape Point, and with minimal layout changes can be made to suit the marlin manne of Sodwana.

This craft’s fish deck is extremely spacious for her size and is surrounded by nice high gunnels and transom. Even with a good-sized, substantial fighting chair on Inkwazi’s fish deck, there was ample room to move around while “working the deck” or catching gamefish.

The Twister has a substantial marlin door incorporated into her design which provides accesses to the dive platform and dropdown stainless-steel boarding ladder. For the Sodwana skipper who hates sand on the deck, a “foot bath” is centrally situated on this dive platform. Again for the marlin anglers, large Luna tubes are a standard feature — one in each corner of the transom — as well as a fair-sized livebait well with a see-through front that can be used as a handwash or bait preparation station if it’s not used for livebait.

Under-gunnel storage is spacious and practical, and below these facilities a gap has been left to channel deck wash into the side channels to exit through the scuppers. It also allows anglers or deckies to push their feet in right up to the instep while leaning forward over the gunnels. This is great for both safety and support during heavy work on the fishdeck.

As André says, their primary layout for the saloon and cabin area is for serious fishermen, but it has been finished in a manner that will enable an owner to be equally proud to use the boat for leisure or entertainment purposes.

To this end they have designed a fixed, centrally-situated seating console that incorporates three separate hatches for bait and other items that need to be kept cold. The centre hatch holds a 5kg box of sards perfectly for the tuna fishermen of the Cape.

The helm station is centrally mounted, with the top of the above-mentioned seating console providing the “bum-seat” for the skipper. I spent a lot of time skippering these two craft, and I can vouch for the practicality of this station, the layout of the controls and the siting of the instrumentation. With the incorporation of clears as we had on Twister 730 (Inkwazi’s still had to be fitted), the saloon area is well protected from the elements.

A surprisingly large forward cabin with good headroom is accessible from both sides of the saloon area. A proper marine toilet can be fitted in the port forward sponson, while on the opposite side there’s space for a microwave on a galley locker with a plumbed freshwater wash station. A comfortable bunk is positioned between the two facilities.

As one would expect from a craft of this size and class, her finishes were of the highest order. As an example, the full and substantial windscreen is purpose-made in the USA by Taylor-made Windscreens and incorporates armourplated glass that will withstand all the ocean can throw at it.

The high-quality finishes and hardware, including all the stainless-steel work, are not only well made, but are also designed specifically for the Twister 730.

As I witnessed during the Jo’burg and Cape Town boat shows where she was on display, she was very closely inspected by many interested offshore boaters. This is the only way to really appreciate the niceties of this craft and the huge work André and all involved in her development have put into the Twister 730.

I was very impressed with this craft, both with regard to performance and detail of finishes. Indeed, I will be very surprised if the Twister 730 doesn’t become a firm favorite in the upper-end of the market for this size craft.

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