The SpeedDream Team had Mike Golding test drive their 27′ prototype, and here are his impressions on that, canting keels and flying.
Q: You skippered the SpeedDream27 prototype over the summer in a variety of conditions. What is your general impression of the overall concept of the boat.
A: After some initial teething issues SpeedDream27 has revealed a great deal of information in a relatively short amount of time. With so many innovations on one platform our job has been to establish which of them is benefiting the boat and when. The canting keel system, which enables the keel to be canted to around 80 degrees, is efficient and works surprisingly well even in fast maneuvers. This is aided by what perhaps is an oversized electric motor producing a cant to cant time of less than 10 seconds. Having the large cant means that a lot of righting moment/power can be developed from a light bulb weight, so overall the boat is very light for her sail area providing ample performance potential.
Keel flying to reduce drag is one of the innovative ideas on Speed Dream and whilst we have had extended periods of testing the boat in this mode – the jury is still out on its efficiency. This is due to the fact that as the keel blade leaves the water the platform loses the dynamic stability induced by the keel blade and the boat becomes loose and rolls quickly onto her hull chine. As this project is scaled up to a larger offshore version this issue will become less noticeable. Larger boats tend to move with less jerkiness and the keel angle will be automated much like an autopilot system so that the overall heeling motion is dampened.
Currently the 27 is fitted with a very conventional daggerboard arrangement which will need significant revision to a foil system that provides a lift/stability that can be pressed against as the keel blade leaves the water. This must be the key next step development for the boat as the project moves forward. I understand that the design team needed to limit the number of new ideas in a prototype and there had been some thought of including a DSS type system but it was left off. It seems clear that this kind of system coupled with better foils will greatly improve overall performance.
The wave piercing bow with a narrow hull seems extremely effective with the boat proving stable and smooth even in a very tough and short chop in the Solent. Of course the boat is wet but scaling the platform up will inevitably improve this dramatically. The narrow bow pierces waves with no significant loss of speed whilst at the same time providing buoyancy forward. It’s completely the opposite design solution (but the same effect) as the scow shapes we are seeing in Mini and Class 40 but in my view has even greater “all round” performance potential – with the added bonus that the boat can look like the Batmobile and not a bathtub!
Without another boat to test against it’s hard to know if there is a performance gain from the athwartship step, but it’s hard to believe it was hurting the boat. There was very little turbulence coming off it and the overall idea of a step is a good one, especially once higher speeds are achieved.
Q: Do you think that the boat in it’s present form can scaled up to a larger offshore version or will some of the ideas on the prototype have to be scaled back?
A: I believe we need to work with the design team to establish which of the innovations are delivering best value for the difficulty of their inclusion. However inevitably scaling up will make many of the innovations even more effective and even allow new innovations to be employed successfully. This project is well into brand new territory and a lot of what SpeedDream is trying to achieve has not been done before. It’s not as if there is a decade of empirical data to draw upon and compare against. There is a plan in place to do a lot of CFD testing using the powerful computing power of the project’s technology partner Yandex. A lot will be learned here and will be incorporated into the next phase of the project.
Q: You have sailed your IMOCA 60 with a canting keel and know its strengths. Other than reducing drag when the keel comes out of the water is there an advantage to having a keel that cants to 82 degrees?
A: Having the keel cant so far enables less bulb weight for the same righting moment. There is also the potential to eliminate keel drag from the speed equation. As the project scales up, the management of such systems becomes easier even if the technical challenge gets greater. From the safety perspective the light bulb and over canted keel give SpeedDream27 a relatively low angle of vanishing stability when compared with other contemporary offshore monohulls. However it will be possible to integrate mechanisms that, in the event of any crew mistake or technical failure could provide a failsafe security to keep the platform upright. As in IMOCA the canting system will need to be sufficiently robust to re-right the boat from any knockdown situation which will always be an advantage for monohulled yachts over their multihull equivalent.
Q: Do you think that you will be able to sail with the keel flying for a sustained period on a larger offshore version of Speeddream out on the open ocean?
A: If we are able to fly the keel smoothly offshore the reduction in drag is interesting – especially over longer distance. I think we need to compare this to sailing a catamaran offshore. In truth most multihulls are sailing with both hulls in the water in most conditions. They certainly are not flying a hull surfing downwind in the Southern Ocean. When the conditions are ideal it’s possible to sail for a long period of time with the hull flying. I imagine the same will apply to SpeedDream. There will be times to fly the keel and benefit from not having the drag. It will be about good helming, good trimming and a system that automates some aspects such as the keel angle.
Here’s a video of the 27′s summer tour…
November 6th, 2013