Rutland 913 Wind Generator Failure

Initial Experiences

During the 2009/10 refit we had our Rutland 913 wind charger mounted on a bracket on Speedwell’s mizzen mast. We’d had this unit on a pushpit pole mounting on our previous boat where it had replaced an old Air-X charger. Although it had a lower output than the Air-X, the Rutland was a lot quieter in operation so we found that we could leave it running without annoying other boats in an anchorage and this more than made up for the lower output current.

In the 2010 season our Rutland worked well most of the time. Under sail it generated power in most circumstances, although on a run with the boat rolling from a following sea the whole unit tended to rotate around its vertical axis as the boat rolled, with the blades never getting a chance to start spinning. That may have been due to the higher mounting position part way up the mizzen which resulted in larger side to side movement as the boat rolled.

Despite the generally quiet operation, we found that some noise was transmitted down the mast and into our cabin so we normally turned the generator off overnight at anchor. Even so we were getting a useful contribution to our electrical needs.

Wind Turbine Failure

In May of 2011, just after we had launched Speedwell for the start of the season, the west coast of Scotland was hit by storm force winds. Several boats broke their moorings and were lost. Speedwell was blown hard against a pontoon, bending most of the stanchions on her port side and causing some cosmetic damage to paintwork, so we got off fairly lightly. However, during the storm our wind generator over speeded and exploded. We were at home in Cambridge when this happened so we just have the reports from the yard staff and berth holders at the marina to go on.

The marina recorded gusts of over 70 knots. The staff were busy trying to protect boats from getting damaged against the pontoons and they noticed that our wind generator was running very quickly. Eventually it flew apart, losing all of its blades, part of the hub and much of the permanent magnet from the hub assembly. Fortunately no one was hit by any debris. Parts of the magnet ended up on the deck and we were told that these were hot to touch when they landed. We never found the blades.

When we got back to the boat to start our summer cruise she was looking sorry for herself, but the yard quickly repaired the stanchions and I climbed the mizzen to untangle the remains of the wind generator’s windings and remove the unit. Checking the boats wiring I was surprised to find that the fuse in the wind generator circuit hadn’t blown, I don’t know if there was any internal damage to the Rutland HRSi charge controller, but the rest of the electrical system was unharmed.

I disconnected the wind generator circuit and, as there wasn’t time to get a replacement, we spent the 2011 season without a wind generator.

Contacting the Manufacturer

The wind generator was out of warranty but I thought I’d contact Marlec, the manufacturer, to see what they had to say about the failure. Here’s their response:

Speedwell was on the most windward pontoon when the storm struck and our wind generator was mounted on our mizzen mast, several meters above deck level, so it is difficult to imagine where any flying debris could have come from. The yard staff reported that the generator simply over speeded and flew apart, they didn’t mention it being hit by anything. So I’m not convinced by Marlec’s suggestion that the failure was due to damage from flying debris.

In 2010 when we were beating into a force 8 in the Sound of Mull our wind generator would occasionally run up to very high speeds, making a worrying screaming noise. Turning the regulator to the off position didn’t stop this so I don’t think that the regulator setting could have saved it.

For our installation, with the generator mounted part way up the mizzen mast, tying it off is impractical; especially should we get hit by extreme conditions out at sea. I’d also be concerned that a blade could get damaged by the cord used to tie off the turbine, especially in strong wind conditions, which could then lead to a failure at a later date. Leaving the turbine tied off or shut down while we’re away from the boat defeats the object of having some renewable generating capacity to maintain the batteries while the boat is unattended.

I’m not sure what to make of the statement that a 914i may be more appropriate due to its different high wind protection mode. Does this imply that Marlect believe that the 913 could potentially fail in high winds?

Having suffered one turbine failure I didn’t feel comfortable about re-fitting the same generator so I decided not to take up the offer of having it repaired.

Other Rutland 913 Failures

I think, in general, Rutland wind turbines have a good reliability record, but some other people have reported failures similar to ours:

A remote monitoring station in Sweden

A data logging buoy test (the wind generator failure is Data and Results section under “Performance in High Winds”).

Wind generator comparison . This one is from a rival manufacturer (Ampair) so should be taken with a pinch of salt, but the last page shows a less dramatic Rutland 913 failure than we suffered.

Life Without a Wind Turbine

We spent 3 months of 2011 living on board Speedwell cruising around Orkney and Shetland. The summer weather was quite poor and we were storm bound for around a week at a time on a couple of occasions, during which we found that we needed to run the engine once or twice to charge the batteries. I think that a working wind generator would have saved this additional engine running so we did miss it then, but for the rest of the cruise we didn’t have any problems with electrical charge.

Speedwell has a relatively large domestic battery bank (600AH) and twin alternators on the engine, one of which is rated at 150A and is dedicated to domestic bank charging. Because of this we can manage for several days between charges and when we do run the engine the batteries charge quickly. For exploring a cruising ground, when there’s generally some engine running every few days to get in and out of anchorages, we can manage with no alternative charging (and we do have a small contribution from our solar panels). When we start to do longer ocean passages I think a wind turbine, or possibly a towed generator, would be a sensible addition, and for those inevitable occasions when we’re storm bound some extra generating capacity would be nice to have.

Replacements

Because of the mizzen mast mounting it was not practical to get to the wind generator to tie it off, especially if we’re at sea and bad weather is on the way, so we need a unit that can survive extreme conditions on its own. So for a replacement we would have wanted either need a turbine for which the manufacturer is happy to publish maximum safe wind speed data or one with some built in mechanism to automatically shut down in extreme conditions.

We also needed to think about mounting arrangements. Our mizzen mounting was custom made for the Rutland 913. We would probably have been able to modify the mounting tube if necessary but the maximum blade diameter wss fixed by the distance between the mounting tube and the mast so without major re-work we were restricted to a maximum blade diameter that is similar to the Rutland.

We didn't manage to find a suitable replacement so we decided to remove the mounting from the mizzen mast. In place of a wind generator we  upgraded our solar panel installation, which has turned out to be a success. We don't miss the wind generator.