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PNW_Wesley
Joined: 28 Nov 2019
Posts: 97
City/Region: Vancouver
State or Province: WA
C-Dory Year: 2003
C-Dory Model: 19 Angler
Vessel Name: Zenith
Photos: Zenith
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 Posted: Wed Dec 02, 2020 1:08 pm Post subject: |
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[quote="thataway"][quote="PNW_Wesley"] | thataway wrote: |
I do run my radar at times when there is not limited visibility......
If you are going to be running your boat in limited visibility, where your best angle is 6*, then you made the correct choice. It is laudable that you looked at photos of various C Dorys..but what is important is what your boat does when at the speed you will most likely need radar.
As an aside, the use of AIS both receivers and transceivers has become the standard for marine safety in limited visibility conditions also. I only have a receiver, but if I was boating in an area with high traffic, and significant limited visibility, I would have an AIS transceiver. |
Hello Bob.
To quote Walter Brennan – “No brag, just fact.”
My 39 years as an avionics design engineer includes flight test, certification, and in-service support for X-band and C-band Doppler radar. In the early 80’s, when airline pilots were transitioning from analog radar to the Rockwell Collins digital radar on the Boeing 757/767, I flew in the jump seat for more than two hundred flights. My function on those flights was to coach the pilots on how to get the best performance from the radar. This involves varying controls such as range, gain, ground clutter suppression, and tilt. Small adjustments can go a long way toward increasing the pilot’s confidence in what the radar is displaying.
Prior to retiring, I was the Lead Engineer on a project to design a new digital autopilot for NASA’s WB-57 fleet in Houston. I was also the System Safety Engineer, and was responsible for analyzing the potential failure modes of the hardware and software, determining the effects and criticality of the failures, and determining methods to mitigate the severity of the failures.
When I stood before NASA’s review board, and proclaimed that the probability of certain catastrophic failure modes was in the 10 to the minus 9th range, I knew that very small numbers made a difference.
When it came to installing the dome on my boat, the engineer in me just couldn’t help following a detailed design process to ensure the best possible performance of the system.
My radar is on at all times while underway, regardless of the visibility. This allows me to continually assess what is on the display relative to what my eyes see outside. When I change a setting, I see the effect of that change within seconds. The net result is a very high confidence that when the fog rolls in, I have done the best I can to assure our safety.
To me, the greatest danger in dense fog is not the ships, which give a strong radar reflection. Most small fishing boats on the Columbia don’t have radar, but they do have a basic chart plotter. They zip along in low visibility, following their past tracks. Picking out a 14 foot fiberglass boat, low in the water, and doing 25 mph is a feat for any radar.
That boat can be coming from any direction. The vertical beam width implies that a signal return is likely to occur when the antenna is not level to the horizon. For optimum target discrimination, the beam should sweep as close to level as one can make it.
I enjoy knowing that my radar installation was done using empirical data. The purpose of studying other Dory’s was to validate my own testing data.
Stay safe out there! |
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thataway
Joined: 02 Nov 2003
Posts: 20808
City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
Photos: Thataway
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| Posted: Wed Dec 02, 2020 2:31 pm Post subject: |
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PNW-Wesley,
I should have figured out that you are an aeronautical engineer! My father was an engineer, and I have a number of friends who worked for Douglas in Long Beach CA.
Good on keeping the radar on all of the time. Reading about the rescue on the Globe Vendee AWR, it was the human mark one eyeball which saw the strobe light, despite a radar reflector on the life raft and the AIS transmitter which was not doing its job!
Yes, the small craft are always an issue.--perhaps more worrying to me are the kayakers and SUP users , even in poor visibility. I would think that the aluminum boats would show up well, but with small fiberglass boats you will get the engine. bloc. One early morning off the coast of Mexico, I sent Marie forward with a spot light, because I was getting a constant blip but not on every sweep. Yep it was a panga, and we were picking up the engine block. This was with a 1982 Raytheon 4 KW state of the art at that time.
Absolutely, even today's best radars need to be specifically tuned--and not put on "auto" as so many boaters do--including experienced ones. Unfortunately when you are in heavy seas any minimal variation of the mounting angle looses any advantage.
What radar did you choose and why that specific radar? Tell us your experience with it.
Take care.
_________________
Bob Austin
Thataway
Thataway (Ex Seaweed) 2007 25 C Dory May 2018 to Oct. 2021
Thisaway 2006 22' CDory November 2011 to May 2018
Caracal 18 140 Suzuki 2007 to present
Thataway TomCat 255 150 Suzukis June 2006 thru August 2011
C Pelican; 1992, 22 Cruiser, 2002 thru 2006
Frequent Sea; 2003 C D 25, 2007 thru 2009
KA6PKB
Home port: Pensacola FL |
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hardee
Joined: 30 Oct 2006
Posts: 12632
City/Region: Sequim
State or Province: WA
C-Dory Year: 2005
C-Dory Model: 22 Cruiser
Vessel Name: Sleepy-C
Photos: SleepyC
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| Posted: Wed Dec 02, 2020 4:02 pm Post subject: |
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Wesley, Also +1 on using the radar all the time. Likewise here.
I have had occasion to find kayaks, at about 100 to 150 feet out, in 20 - 30 ft visability. Scary in that thjey were getting ready to cross Blackfish sound, in front of a tug with a barge tow and another tug with a log boom tow, both of which I had on AIS and radar.
Good on you to do that research.
Harvey
SleepyC 
_________________
Though in our sleep we are not conscious of our activity or surroundings, we should not, in our wakefulness, be unconscious of our sleep. |
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PNW_Wesley
Joined: 28 Nov 2019
Posts: 97
City/Region: Vancouver
State or Province: WA
C-Dory Year: 2003
C-Dory Model: 19 Angler
Vessel Name: Zenith
Photos: Zenith
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| Posted: Fri Dec 04, 2020 9:09 pm Post subject: |
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| thataway wrote: | PNW-Wesley,
I should have figured out that you are an aeronautical engineer! My father was an engineer, and I have a number of friends who worked for Douglas in Long Beach CA.
What radar did you choose and why that specific radar? Tell us your experience with it.
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I worked at Douglas LB from '79 to '82.
I chose the Garmin Fantom 18 for several reasons.
The Fantom’s 40-watt pulse means far less energy for the occupants to be exposed to, and the dome’s power consumption is considerably lower.
The component most likely to fail in older high-power radars is the magnetron, which generates the output pulses. The Fantom does not use a magnetron.
It has Doppler capability, which it uses to determine if a target is moving relative to other returns.
My first outing with this system was in February, on a 2-night cruise from Kalama to Astoria and Cathlamet.
Within the first 2 hours of using it, and still testing the various settings, it captured a target that really impressed me.
About 10 miles south of Cathlamet, there is a highway along the shore with cliffs on the north side of the highway. A cement tanker truck was heading west, about 0.3 miles off my starboard bow.
In a Doppler radar, the software looks at the amplitude of the instantaneous returns as they are received to determine if that return should be black, blue, yellow, or red on the display. It also measures the frequency of the received signal, which it uses to determine the motion of a target relative to other targets.
The software calculates the current closure point of your boat and a moving target. A moving target will be displayed as green or magenta, based on the potential for collision.
The signal returns from the rock cliffs were very strong, as shown by the solid red bar to the right of my heading line. The subtended angle of the truck was very small compared to the length of the cliffs.
When my radar picked up the truck, it was displayed in green. At that instant in time, the signal returns included those from the truck and from the cliffs behind it. The software was able to differentiate the frequency of each return, and found the moving truck. That is like picking out a candle in a forest fire.
I am happy with my system.
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thataway
Joined: 02 Nov 2003
Posts: 20808
City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
Photos: Thataway
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| Posted: Fri Dec 04, 2020 9:51 pm Post subject: |
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Thank you Wesley. Impressive photos!
Why did you choose the Garmin Fantom over the offerings by Furuno, Simrad (4G, Halo 20/24) or Lowrance (3G) or RayMarine Axiom Quantum 2 radars?
Also can you comment upon the choice of an 18" with a 5.2* horizontal beam vs the 24" with the 3.7* horizontal beam? Does the solid state negate the need for best discrimination? (One of the C Dory 25's had a 6' magnetron scanner, but it looked like a. helicopter)...
Another important feature of the solid state/digital radar vs the magnetron is that the solid state come on instantly, vs a usual 90 second warm up period for the magnetron.
Also the solid state/digital/broad band radars can "see" objets up to about 20' away (depending on location of scanner). The Magnetron units were blind to close up objects.
Comments about Long Beach in PM. |
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colbysmith
Joined: 02 Oct 2011
Posts: 4547
City/Region: Madison
State or Province: WI
C-Dory Year: 2009
C-Dory Model: 25 Cruiser
Vessel Name: C-Traveler
Photos: C-Traveler and Midnight-Flyer
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| Posted: Fri Dec 04, 2020 10:44 pm Post subject: |
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| Quote: | | when airline pilots were transitioning from analog radar to the Rockwell Collins digital radar on the Boeing 757/767, I flew in the jump seat for more than two hundred flights. My function on those flights was to coach the pilots on how to get the best performance from the radar. This involves varying controls such as range, gain, ground clutter suppression, and tilt. Small adjustments can go a long way toward increasing the pilot’s confidence in what the radar is displaying. |
I retired from AA flying the 757 and 767. I started my career with them flying the 727. Most of my prior experience was on the USCG C130 spending my last year on that in Kodiak Ak. That’s where I got my best radar training as we not only used aviation radar for weather but many times more for finding ships/boats and ground mapping. I took that knowledge with me to the airline especially while flying in and out of ski cities and even many of our regular airports out west with big hills around them. Something I learned is that dials are made to play with!  Sadly too many of my fellow pilots would turn on their radar, put it basically in an automatic setting and never tweak the dials to get a better picture. Two things I believe are important. First use your radar on a perfectly clear day when you can see/learn to read what it’s showing you. That will also help build your confidence for when you really need it! Two, don’t be afraid to play with/adjust the settings. Varying the view will give you a better picture of what’s out there! Colby |
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hardee
Joined: 30 Oct 2006
Posts: 12632
City/Region: Sequim
State or Province: WA
C-Dory Year: 2005
C-Dory Model: 22 Cruiser
Vessel Name: Sleepy-C
Photos: SleepyC
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| Posted: Sat Dec 05, 2020 12:05 am Post subject: |
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Wesley and Colby. Thank you. Really good advice.
Harvey
SleepyC
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PNW_Wesley
Joined: 28 Nov 2019
Posts: 97
City/Region: Vancouver
State or Province: WA
C-Dory Year: 2003
C-Dory Model: 19 Angler
Vessel Name: Zenith
Photos: Zenith
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| Posted: Sat Dec 05, 2020 11:55 am Post subject: |
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| thataway wrote: | | Why did you choose the Garmin Fantom over the offerings by Furuno, Simrad (4G, Halo 20/24) or Lowrance (3G) or RayMarine Axiom Quantum 2 radars? |
Bob - I don't have first-hand experience with the other brands, so I can not comment on how well they perform. A detailed comparison of brands and their features would be beyond the scope of this thread. |
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