|Departing San Francisco Bay|
Conditions for the most part were quite good, though it picked up for about 12 hrs on the day that was forecast to be questionable. But mostly we had 2-4 ft wind waves on the nose from 15 kt wind, and slow 6' or more swell from the west. The swell is quite tolerable given it's direction, and the chop is short enough duration that we mostly plowed right through it. But occasionally the two conspired to toss us around.
|Iconic Washington Coast|
We made it safely to Neah Bay at the end of Cape Flattery and found it completely empty. No boats, no crab traps, nothing. One other sail boat came in about a hour after we settled in. It sure is nice to have a boat that’s not moving. From there we rode the current down to Port Angeles, then on to Salmon Bay on Tuesday. Through Nordhavn we were able to get longer term space at Elliot Bay, so after we get the heating system work done we will move the boat over there. I think we will keep it there through the holidays and until we return, but we aren’t sure yet when that will be.
- one of the auto pilot pumps appears to be having a problem and causes rudder control alarms. We have switched to the other pump and are continuing on.
- the MARPA does not work well and nearly resulted in a collision off Cape Disappointment. MARPA stands for Mini Automated RADAR plotting aid, and is a way for radar to "lock onto" a target and after monitoring it for a while to show you its course and speed. It's incredibly helpful to be able to see the direction and speed of other boats to figure out if you are on a collision course or not. At night and in fog, it's nearly essential. As we were crossing the mouth of the Columbia River and threading between incoming and outgoing boats, we had a MARPA target pretty close by, but it showed us totally clear. I was looking for the boat but could only see bright sodium lights that I though were way off in the distance. Normally you would see a white steaming light and some combination of red and green lights that will tell you the relative direction of the other boat. Well it turned out to be a big fishing trawler with all his deck lights on running on a perfect collision course with us. The sodium lights drowned out his nav lights and I didn't realize it was the boat and not something 3 miles away on land until he was nearly on top of us. I scrambled to turn on all our deck lights to light us up like a christmas tree, and about two seconds later he called us by name on the radio to let us know he saw us. To know our name he must have seen us on AIS (AIS is a gadget that continually transmits our position, course, and speed along with the boat name, radio call sign, boat length, etc.) But he wasn't transmitting the equivalent info or I would have had him on our screen from 20 miles away. I have to say it really rattled me. Not just because it was a close call, but because I badly misread the situation.
Getting back to MARPA, we have a clear problem with ours not showing the correct course and speed of targets. It's very erratic, and even when stable it shows a course that's off by between 10-20 degrees. That's easily the difference between a safe pass and a collision. I did a test with a tug and tow to compare with AIS. The tug had AIS, and I locked the radar onto the barge. The two are obviously going in the same direction and at the same speed. The AIS was correct, and MARPA also leaves a cookie crumb trail showed the historic positions of the barge following the tug. The AIS course and the cookie crumb trail both showed the same course, but the MARPA course predictor arrow differed by 10-20 degrees. I get the same results with both radars, and the same using either of two different heading sensors. I think the black box chart plotter is miscalculating since it seems to be the common component. Its a real problem and makes operating in fog, like we were in for two says all the way up the sound, a bit unnerving.
The screen shot below shows the problem. You can see the target about 3.5 miles away with the cookie crumb trail and the AIS direction and speed line running in the same direction. But the line pointing off to the side is the MARPA course and speed line for the same target. As you can see the lines point in very different directions
|Messed up MARPA on Radar|
- we have a slow but measurable hydraulic leak that I have been unable to track down.
- my sat compass has now gone complete dead twice. Both times we had the wind up our tails and the compass is just above and forward of the exhaust. My current theory is that the exhaust is causing it to overheat when it is getting blown forward towards the device.
So there you have it. It's a boat.
Most interesting, and your final comment was very witty!ReplyDelete
Paul in France
You've done a great job of walking us through all the details of designing, building and commissioning and I am looking forward to following you as you journey around the Pacific Northwest and then I guess onto Alaska. I spent a lot of great time sailing in and around the San Juan and Gulf Islands, before I decided to travel the hyways and byways and finally the back trails of this great continent.ReplyDelete