I considered adding a high-end radar as the primary, and keeping the rest of the Simrad gear. But there are just too many other issues, and no sign that Simrad will get them fixed in any reasonable time frame. We are heading to Alaska in the spring, and I want to have a solidly working system by them. Besides, if I kept one of the Simrad radars, it would have to be the 4G. I don't have room for two open arrays without major reconfiguration of my stack. And I have been woefully unimpressed with the 4G radar. I'd say the Emperor has no Clothes.
It's a bit of an apples to oranges comparison, but I haven't found any situation of any kind where the 10KW open array didn't outperform the 4G. And that includes close in situations where the 4G is supposed to be all super duper. And although I've never run them side by side, I think my Furuno 4kw dome outperformed the 4G as well. And there are a number of situations where the 4G simply did not pick up targets at all, and we are not talking about sticks floating in the water. We are talking about boats that I can see with my naked eye. If I can see better than the radar, something's wrong. The other issue with the 4G is interference from other radars. When you are in close with another boat that has a beefy radar, you get all sorts of interference on the 4G. The streaks in the picture below show a a very moderate example, and it tends to happen when you are in close with other boats. I've had other situations where it pretty much obscures the whole screen. So you go blind just when you need radar the most. Now that's helpful, isn't it?
|Interference on 4G radar from another boat|
So the problem became what to do about a secondary radar. I'm not willing to go venturing far and wide without a backup radar. It's one of the most important navigation tools on a boat, and a backup is mandatory for any long distance or remote cruising. I considered the Furuno TZ black box which could control a second radar, and can also control a fish finder thereby restoring that functionality too. Then someone pointed out that I could run two radars off the TZ and not have to buy the giant and expensive commercial radar. I'm not a fan of the Furuno NavNet3D or the TZ, but I figured that I could suck it up if all I was using it for was radar control. So for a few days I was pretty excited about this approach. With the TZ as a single point of failure I would have to carry a spare, but I was planning to carry a spare NSO as well for the same reason. Then the excitement came to a screeching halt.
I discovered that the TZ is missing two key radar features - features I consider to be mandatory - and features that even Simrad has. They are 1) Relative motion vectors for AIS and ARPA targets, and 2) target history tracks.
Tracking relative motion is the foundation for collision avoidance. One of the first things you learn in any boating safety class is how to tell if you are on a collision course with another boat. You sight the bearing to the other boat, and monitor it over time. If the bearing remains the same and the boat keeps getting closer, you are going to crash. Said another way, that boat's relative motion is directly towards you. If the boat's bearing moves towards your bow, the other boat will pass ahead of you. If it's moving towards your stern, it will pass behind you.
Radar can be used to figure out the same thing, either manually by marking positions with a grease pencil, or using more modern tools like ARPA (Automated Radar Plotting Aid). ARPA tracks the targets position and calculates both it's true course and speed, and it's relative course and speed. From these it can also calculate the closest point of approach (CPA) which is how close you will come to one another, and the time to closest point of approach (TCPA) which is when that closest encounter will occur. All this can also be done manually, but it's way easier to let a computer do it.
The relative motion vectors that I was talking about earlier are just arrows emanating from the target showing its direction and speed. On any commercial radar you can select whether you want those vectors to show true motion or relative motion. True motion is much more intuitive to look at, but it leaves you guessing about collision risk, doesn't tell you whether you will pass ahead of or behind the other vessel, and doesn't let you see how you should alter course to achieve a safe passing distance. Let's say, for example, that your radar is reporting a CPA of 1/4 mile, and you want 1/2 mile. Which way do you turn to increase the passing distance? If you turn the correct way, your CPA will increase, but if you turn the wrong way, it will decrease even more. You need to know whether the boat is going to pass in front of or behind you to know which direction to turn to increase your distance.
Enter relative motion vectors. Switch modes, and now you just look to see where the target's relative motion vector is pointing compared to your position. If it's pointing at you then you are on a collision course. If it points ahead of you then the target will pass ahead of you, and if it points behind you he will pass behind you. It's a very important tool, and I have to say I'm really surprised that it is missing in the TZ. To me, that makes the TZ radar unsuitable as a primary radar, and a compromised as a secondary radar.
The second missing features is target history track. This are nothing more than a dot dot dot trail showing where the target has been. Target trails are not to be confused with echo trails. Echo trails are a modern synthesized version of the long afterglow on old radar CRT screens. They are like comet trails behind anything that's moving. They show the same thing as a target history track, but history tracks only apply to AIS and ARPA targets where echo trails apply to everything that moves. So land, for example, all has a big comet trail behind it as you move past. This quickly becomes distracting and you need to clear the trails and let them reform. History tracks only apply to the things you care about and don't otherwise clutter up the screen.
So all this brought me back to the Furuno commercial radar as the only option for a primary radar. This radar, by the way, finds itself in some pretty impressive places. This is the Nimitz-class aircraft carrier Carl Vinson
|Furuno FAR radar on USS Carl Vinson|
And what about the fish finder? With no TZ, how do I display that? I'm not a big fisherman, but I still find it very helpful to get a good view of the bottom and don't want to give it up.
Next stop was the Seattle Boat Show, and there I found answers. First, I saw the smallest dedicated radar, the 1835, and it's a really cute little thing about 12" square with nice dedicated knobs and dials for quick radar control. No hunting around in menus. I figured worst case I could keep it in a drawer and break it out and plug it in when needed.
Next was the small dedicated fish finders. Again, the smallest one is only about 7" square and again has knobs and dials dedicated to it's function. And that little screen is plenty for what I need. And cost is no more than the fish finder box that I would have needed with the TZ.
So that's the plan.
- Two dedicated furuno radars, one little and one big.
- A dedicated fish finder.
- Dual Furuno NavPilot 700 auto pilots. Unlike the Simrad pilot, you can actually build up two independent pilots using the Furuno gear so you really have a hot standby. When I was first evaluating the Simrad gear, I sketched out a dual pilot system and Simrad told be in no uncertain terms, confirmed in writing, that it would work as I expected. Well, after hours and hours and lots of swapped out equipment, I can tell you with certainty that it DOES NOT work. Simrad now confirms that it doesn't work, and has never been designed or tested with dual pilots in mind. Anyway, the Furuno pilots let me finally build the dual system that I wanted from the start.
One of the hallmarks of this new approach is that I have no integrated multi-function display (MFD) or black box. These multi-function systems, though great in concept, seem to be a big source of bugs. And I'm finding that their functionality also tends to be a compromise. But really the only thing I lose by getting rid of the galactic integrated black box is radar overlay on a chart. Oh, well, it's worth it to have a properly functioning and featured radar, and an auto pilot that works predictably.