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Hello
I am based in Northern Georgian Bay and mostly cruise solo.
Has anyone attempted to replace exterior traditional instruments (speedlog, etc) on the cockpit bulkhead by glassing-in a GPS display unit?
Which unit would you recommend?
Thanks
Bill James
SESIYA
Bill
Bill
Sesiya, #643 1975
Parry Sound & Bayfield Inlet, Georgian Bay
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Hi Bill:
Well, we know of chartplotters mounted on binnacles, so it certainly should be possible to mount one on a cabin bulkhead. One would need to very sure the unit is readable in direct sunlight however. I would think you'd need quite a large display screen as you may be several feet away. Think unit on starboard bulkhead and vessel on port tack with skipper up on the rail!
If I were doing this, I'd mount the unit on a swing arm so it could be positioned in the companionway and read from the cockpit, or swung into the cabin for weather protection, secure storage and inside use.
I used to work for a marine firm that installed lots of electronics, we recommended Raytheon to our customers.
Good Luck,
Tony Jeske
Mk V #581
FLYING CIRCUS
San Diego
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Thanks Tony. Good advice.
Bill
Bill
Bill
Sesiya, #643 1975
Parry Sound & Bayfield Inlet, Georgian Bay
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Ralph may chime in here. He has a Standard Hoizon 175 mounted on the port. I plan to do the same with mine which is now located on a board that fits in the companionway. The location works fine for me. I have made a teak pad to mount mine on the bulkhead as well. Someday I'll install it... someday.
Mike M
SV Wind Horse
#375
Galveston, Tx
Mike M
SV Wind Horse
#375
Galveston, Tx
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Did one of you send me the photos of a swing-away GPS in the companionway? I lost the contact info for those photos.
- Admin
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Hello Bill,
I'm going to weigh in with an unsolicited opinion which is probably worth exactly what you are paying for it. Your question implies that you are thinking of dispensing with traditional instruments, such as the knotmeter and depthsounder, in order to rely entirely on a GPS for your navigation. I would strongly urge you to reconsider this. The world of GPS is not entirely under your control, whereas your traditional instruments are. The Americans can at any time degrade the accuracy of the GPS system, or even turn it off entirely. Mother Nature may find ways to interfere with GPS signals. I realize that this is as unlikely as, for instance, the Americans simultaneously shutting down every airport in the country. Then again, that did happen on 9/11 and is happening now across Europe, because of volcanic activity.
Very recently, there was also a well-publicized incident of an Australian maxi-boat racer, PriceWaterhouseCoopers, which drove itself ashore on a rocky island while depending entirely on GPS for navigation. Two crew members died. The Cruising Yacht Club of Australia determined that the proximate cause of the wreck was that the skipper was relying completely on a GPS unit which, due to time of day and reduced coverage, was inaccurate by at least 100 metres. Full story at http://www.news.com.au/breaking-news/drowned-sailors-gps-at-least-100m-out/story-e6frfku0-1225834344457.
That said, I have a Garmin GPS unit mounted on my binnacle and it is interfaced to my autohelm. On one test run, the unit brought Carriden right into the harbour mouth without my needing to touch the helm. I also navigate the entire length of Lake Ontario relying purely on the positioning and charting capabilities of my GPS. However, I would never give up my ability to fall back on my old-fashioned instruments, paper charts and dead reckoning skills, because Murphy and his law are always waiting. I once had a GPS unit rendered unusable because a crew member lost his balance and smashed the antenna. Most modern GPS units are MilSpec waterproof and have no problem being mounted outside in the cockpit while they are being used. So, I heartily endorse the mounting and use of a GPS unit. Just, please, don't succumb to the modern notion that you can safely venture into the wilderness while being entirely dependent on advanced technology.
Marcus from Carriden
Mk III, Hull #847
Oakville, Ontario
Marcus Opitz,
Formerly from Carriden, Mk III, Hull #847,
now skippering "Everdina," a 1975 Ontario 32
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Admin, I sent them to you.
Dean M Baldwin
Morgan "D"
Mark III - Hull 516
North Sydney, N.S.
Dean M Baldwin
Morgan "D"
Mark III - Hull 516
North Sydney, N.S.
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This is going to be a bit of a me-too post following on Marcus' admonition about unwarranted trust in a GPS (but with a slightly different slant, so don't give up). First, Doug Hunter earlier pointed out a full report from the Cruising Yacht Club of Australia (which is their racing organization) at http://www.cyca.com.au/sysfile/downloads/CYCA_Flinders_Islet_Internal_Inquiry_Report.pdf which rewards reading, with its description of the speed with which PricewaterhouseCoopers (PwC) went from a crack racing yacht to a terrifying "deathtrap", and how all the safety equipment and precautions mandated for racers were effectively nullified by thoughtless stowing (a subject on which safety seminars don't always achieve a good balance).
The heart of the report, however, is the discussion of how PwC's skipper's habitual over-reliance on GPS collided with a brief point in time when the GPS constellation was particularly badly placed in the sky, resulting in a lethally poor position fix. The skipper of PwC could, in an ideal world, have saved his life had he either taken a look round from the other side of the boat, or looked at the alarming DoP value on his receiver (DoP is a measure of GPS' theoretical accuracy at a given receiver, based largely on satellite geometry relative to that receiver); in practice, it's unlikely that he would have, as the information is buried within the setup values.
Having read the Flinders report, I was interested in assessing the difficulty of ascertaining GPS accuracy while sailing and so spent some time fooling around with a Raymarine system while sailing in the Caribbean in March. On the chartplotter on our boat, getting DoP information wasn't hard, but you had to know _why_ to look, then you had to know _where_ to look and delve through a series of screens to get to it; it wasn't something you'd do casually or while otherwise busy rounding a mark or rocky islet.
While fiddling with the plotter, I started noticing inconsistent anomalies; sometimes the plotter seemed to be spot on and other times it was off by a considerable amount. On two successive days, while heading south, the boat was displaced considerably from its plotted position, despite excellent DoP numbers. Accordingly, I recorded a number of GPS positions with a handheld GPS and also with the boat's plotter. Back home, I transferred the values to a chart, confirming what I had informally estimated based on the position of the boat relative to marks and bits of land -- the plotter was (in)consistently about 150 meters out.
This seems outrageous. GPS is supposed to be accurate to single digits of feet and sometimes this unit appeared spot-on. There is a possible explanation. The charter boat's GPS antenna was mounted on the lower rail of a two-rail pushpit, probably to give it a measure of protection from careless charterers. When I took readings with my handheld unit in a similar position, it also yielded wonky values (though not precisely the same ones).
Since the days of Loran-C (now coming to an end, apparently), techs have lectured us not to just stick an antenna any old where. We have no information on where PwC's antenna was, but it seems to have had a known record of inaccuracy. Presumably the boat's fabulous winning record rendered everyone indifferent to the issue.
What can we do as sailors? If you're fitting a GPS, test the location before making in permanent, not once, but for a while. The best locations for GPS antennas, apparently, are outside the lifelines and rigging, with a clear view of the sky -- in other words, not on the lower rung of a pushpit or on top of the coachroof. If you're chartering, check the boat's chartplotter against known landmarks or sea-marks.
And, as Marcus advises, never forget your traditional means of navigation. Eyes, ears, compass and binoculars are the best line of defence against navigational surprises.
David Weatherston
Towser, Toronto
C&C 27 Mk IV
David Weatherston
Towser, Toronto
C&C 27 Mk IV
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Dean:
how or where can I see the photos?
Bill
Bill
Sesiya, #643 1975
Parry Sound & Bayfield Inlet, Georgian Bay
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Last two pics in Black Arts / Various Projects on Deck http://www.cc27association.com/fixes/various/various_deck.html
Dean M Baldwin
Morgan "D"
Mark III - Hull 516
North Sydney, N.S.
[Now properly attributed. - Admin]
Last edited by (2010-04-23 23:59:00)
Dean M Baldwin
Morgan "D"
Mark III - Hull 516
North Sydney, N.S.
Offline
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