Moving on board-Sun Awning-Exhaust System – Stern Gland
In Greece the month of June is quite hot and sunny. A protection from the sun was now essential. We ordered a large sun awning which also had to be waterproof. The material is quite tough but light enough to be foldable and easy to store in the cockpit locker.
An aluminium tube holds the back end of the tent which is attached to the backstay. A zip from the aluminium tube to the end of the boom allows the textile to have a small opening for the topping lift.
In the exhaust line there is a part called the “waterlock”. This plastic box has to collect cooling water when the engine stops. It also prevents sea water from coming back into the engine.
We firstly installed a classic Vetus LP 40 waterlock but after talking with our mechanical engineer, he suggested that the water lock should be installed in a lower position. The Vetus exhaust manual is also explaining that the waterlock has to be installed in such a position that minimises the risk of sea water coming back into the engine.
Unfortunately, our installation was not safe enough. We decided to use another type of waterlock (NLP 40), with a larger water capacity (4.5Lts). But still the exhaust line wasn’t correct. The exhaust elbow will be modified later.
The new waterlock was now installed on the starboard side, but it was still too high. In case of healing, the water contained in the waterlock could eventually come back and flood the engine. A new exhaust riser will have to be designed, welded and installed in the future.
A classic bronze stuffing box is the oldest stern gland system and is supposed to be the safest solution. The advantages is that in case of water ingress, you can always pump extra grease or tighten up the packing rings. But the main disadvantage is the water dripping into the engine bilge. In theory this dripping should be a few drops per minute.
When we launched Samourai, on the way to the port we monitored the stern gland and noticed that the bronze part was overheating. We did unscrew the main nut to let more water in, but still this didn’t affect the rising of the temperature.
This problem had to be solved as soon as possible. The overheating could damage the stern gear and especially the new shaft. We spent a few afternoons trying to solve the issue and did various measurements with an infrared thermometer. But still, no matter what we tried, we couldn’t adjust properly the stern gland. At the end, we gave up, canceled our sailing holidays and decided to lift the boat out. This old fashion technology was like “dark science” to us !
Early morning breeze: sailing back to the boat yard to lift the boat out. Just under Genoa, with a slight force 4, a nice short leg.
The log transducer after a month in the water was full of seaweed. If you can dive and clean it, then it’s fine. If you can’t dive and the transducer does not work, then you have only the speed over the ground with the help of the GPS. The question is: what is the point of having a log that rarely works properly ? There are two solutions to this problem: either you dip the transducer once in a while in a glass of vinegar for the night, either you cancel the log transducer ! However with this solution, you loose the ability of estimating the currents.
Once the boat was on land, we took apart the stern gland and discovered that a lot of grease had literally “stuffed” the stern tube ! This accumulation of grease wasn’t letting enough water in to the packing flax. Another possible explanation for the overheating.
After cleaning the old grease, we discovered light marks around the shaft. Thankfully, these were only superficial and the shaft was still in good condition.