Is two better than one?


“We do have instances of yachts being fitted with both types of stabilisers, more for remote clients who require redundancy. However, you wouldn’t want to have them operating at the same time as that would be counter-intuitive and they would work against each other. If both systems are installed it is better to use them separately. For instance, the gyro at anchor and under 10 knots, and the fins for passage making. But the cost and extra weight of having both installations onboard strengthens the argument to choose one system over the other.”


Performance


“In terms of performance detraction on a yacht they are about equal. The fins cause a very small amount of drag while the mass of the gyro also slows down the yacht slightly.


“If you look back 10 years ago, we were fitting an occasional gyro and now more than 50 per cent of the yachts have them. But in the past two years the trend has gone towards fins which have been well accepted. And a lot of that is to do with the fact they are Humphree fins, which are electric and they integrate to the Humphree trim tab (Interceptor system).


“So, you get excellent active ride control, coordinated turning, auto list and auto trim, making a good complete system. This brings me to talking about using the two systems together, and we recommend you don’t use them at the same time, just independent of each other.”


Automatic trim control always delivers perfect running trim by controlling the pitch the vessel has while underway.


Summary


Ultimately it is up to the individual yacht owner to make the decision. However, the two systems are different, and the points below should be considered when making the choice between the two. You should also consider how and where you like to use your motor yacht.


The greater the speed the more water flow there is, and the more force is created to counter motion. Because their potential force increases with speed, fins are well suited to faster ocean-going motor yachts.


Take into account: - The fuel economy and upfront expense of both items are comparable;


- The draft of the fins versus no extra appendages on the outside of the hull to risk entanglement, makes the gyro better for shallow cruising;


- Performance over 10 knots is better with the fins;


- Performance under 10 knots and while at anchor is better with the gyro;


The carbon fibre fins are easily installed on the bottom of the servos and precisely torqued up to the manufacturer’s specifications.


Dan Henderson, Riviera’s Design and Engineering Director, lends his experience to this topic.


“We have had some very good reports from people using fins on long trips in New Zealand. You do have to consider that the gyro adds a fair bit of extra weight to the boat, and they are usually positioned right at the back of the yacht so they can change the trim slightly. While the fins don’t add anywhere near as much mass to the boat, you do have the additional draught caused by the fins.”


116 | ISSUE 110 | DEC 2024 | THE REPORT


- Natural integration between the trim tabs and the fins gains better ride control for the fins through the Interceptor system and an integration doesn’t exist for the gyro;


- For power you need to use your generator to run a gyro where the fins use the ship’s power, so noise becomes a consideration.


For more details: www.rivieraaustralia.com


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100  |  Page 101  |  Page 102  |  Page 103  |  Page 104  |  Page 105  |  Page 106  |  Page 107  |  Page 108  |  Page 109  |  Page 110  |  Page 111  |  Page 112  |  Page 113  |  Page 114  |  Page 115  |  Page 116  |  Page 117  |  Page 118  |  Page 119  |  Page 120  |  Page 121  |  Page 122  |  Page 123  |  Page 124  |  Page 125  |  Page 126  |  Page 127  |  Page 128  |  Page 129  |  Page 130  |  Page 131  |  Page 132  |  Page 133  |  Page 134  |  Page 135  |  Page 136  |  Page 137  |  Page 138  |  Page 139  |  Page 140  |  Page 141  |  Page 142  |  Page 143  |  Page 144  |  Page 145  |  Page 146  |  Page 147  |  Page 148