Airship Goes to Alaska
Yep, we're still here. But hey! Check out this gorgeous weather we've had!
We're working to 100% figure out and fix the shaft seal/Cutless bearing issue we have while we have access to a lift (to haul the boat out again if we need to) and people who know people with tools and stuff here in Aurora Harbor. Steve from Nordic Tug Charters continues to be very helpful and is letting us camp out on his dock (right next to the boat yard and lift) while we tweak and test and tweak and test.
We're pretty sure we now know what actually happened the other day, so we don't have to wonder anymore about that (not a giant squid after all). (Skip this next part if you want to just see the pretty pictures.)
Here's the current diagnosis:
After our initial haul out, we fixed the alignment issue in the drive shaft and we thought that might have solved the problem, so we decided to head out on the next leg of our trip, monitor everything, and see if anything was hinky.
A few hours into that trip we discovered the issue with the shaft seal bellows inflating, which caused us to turn around and head back to Juneau, because we certainly didn't want the bellows to rupture, allowing seawater to come rushing in. (Turns out the bearing is likely clogged, and seawater would only have come dripping in, not rushing. But I'm getting ahead of things.
The dripless shaft seal surrounds the drive shaft as it exits the hull. Its job is to keep the seawater from leaking into the boat around the spinning propeller shaft. The shaft goes from the transmission through the shaft seal and then passes through the hull to the propeller through what's called a Cutless bearing.
The shaft seal has a bellows that is compressed a certain amount, and there is a stainless collar that sits tight and spins against a carbon collar. Water is plumbed to this seal from the pressure side of the raw water pump on the engine, and then exits out the back of the boat through the grooves in the Cutless bearing. The water keeps the moving parts of the seal cool, and lubricates the Cutless bearing as the shaft spins inside it.
We apparently have two problems:
First, something is partially clogging the Cutless bearing so not enough water flows through it.
Second, the raw water pump supplying water to the shaft seal operates at too high a pressure. The seal is supposed to get 1-2 psi of pressure, and no more than 10 psi. The raw water pump can generate pressures of as high as 25 PSI, however. Normally, this is no problem because the water just flows right through and out through the Cutless.
But, with the Cutless partially clogged (problem 1 above) the raw water is hitting pressures maybe up in the 20 psi range. Water is being pumped in the front, and can’t escape out the back fast enough. That causes the bellows to inflate (and potentially rupture! That would be BAD). In our case, running at high RPM for several hours to escape the bad seas, the bellows inflated so much that it mashed the two surfaces of the seal together causing overheating and vibration/sticking in the shaft. It also pushed the back of the bellows backward along the tunnel, which made the seal start leaking when the water pressure inside went down.
Here's the shaft seal, readjusted to where it should be (the sleeve had been pushed all the way back to where it shoved up against those set screws, on the right):
And here it is inflating while under way. (Totally not supposed to do this. At all.):
So, we have installed a valve that allows us to reduce the water pressure coming into the seal. That way, we can prevent the seal from inflating and possibly bursting. We tested that for several hours yesterday and it works great.
Now, we just need to find out why the water flow through the Cutless is restricted. Unfortunately, that means hauling the boat out of the water again, disassembling the seal, possibly removing the prop and even the bearing, and maybe replacing the bearing. Ugh.
It seems to work fine for now, but we’re worried that the restricted water flow through the Cutless could leave it under-lubricated and cause the bearing to fail. We definitely do NOT want that.
The upside was that it was a great weekend to be sea testing…can't beat a couple of sunny 68 degree days in SE AK!
Passing a cruise ship on our way out of Gastineau Channel (one with a top deck water park!):
Here we are at the Nordic Tug Charters dock:
Nice light last night as we headed out for dinner:
We took Steve and his girlfriend Julie out to dinner last night (as an additional gesture of thanks). We went to Salt, and it was good, but nothing to write home (or blog) about (and yet, here I am blogging about it). We ordered salmon ceviche and truffle fries as appetizers. The ceviche came and it was not salmon, but some white fish…maybe halibut…our waiter never said. It was good, but pretty much your basic ceviche. The fries were truffle fries with a bernaise sauce and parmigiano reggiano, topped with a fried egg and they were excellent. (We agreed that the fries were the best thing we had last night.) The caesar salad was good, and the entrees (filet mignon, prime rib, halibut, and crab cakes) were all solid but there was nothing too creative or special about any of the dishes. We'd go to The Rookery any day over Salt.
Today it's cloudy and a little rainy and we're heading over for another haul out to see if we can figure out what might be restricting the flow of water in and out of the Cutless bearing. Wish us luck!