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trevork
3949 Posts |
 Posted - 04 Jul 2020 : 14:23:36
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Got this from Brian. Can anyone help? I'm not clued up on these.
I am writing to see if anyone can give me some advice.
I have a Norman 20 that I have fully restored and I am fitting a chart plotter with a in Hull transducer.
I was looking to fit it in one of the lockers in the forward cabin as I already have a transom transducer on the rear of the boat.
My concern is.
Have the cabin lockers a double skin of fiberglass and not the direct Hull itself?
In hull tranducers can't have any air between it and the hull.
Hopefully someone can help me?
Kindest regards
Brian
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cliveshep
Thailand
1324 Posts |
Posted - 04 Jul 2020 : 16:31:24
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Bunk lockers both cabin and cockpit of the Norman 20's have the hull moulding as the bottom so if you were to get hold of say 100mm of 38mm (1.5 inches) ABS waste pipe, Osma or Hunter solvent-weld pipe, cut one end to an angle so that touching the hull inside the locker it was upright. Clean a patch of hull against the inboard side of the locker with thinner or a sander.
Then get and mix some car body filler, P.38 or Cataloy or similar, and put a fillet all round the cleaned area of hull with the waste pipe standing vertical on it and leave to set. The fillet should be a right-angled triangle cross section of at least 15mm.
When hard, pour in about 75-100 ml of cooking oil or baby oil and push your transducer down into it. It will now work perfectly through the hull. Transducers in transom brackets can get fouled, those internally in oil filled tubes do not.
As an alternative you can bond a transducer with clear silicone mastic BUT this leaves the delicate shaft of the transducer exposed to accidental damage from anything else chucked into the locker. In a tube of oil it is protected and can be removed if you sell the boat.
Finally living the dream!
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df
United Kingdom
5991 Posts |
Posted - 05 Jul 2020 : 14:13:45
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Why??
That sounds like a depth sounder not a chart plotter with a in hull transducer, there's no point having two depth sounders as you can't stop a norman 20 in 20 feet anyway.
The hull is single sken so if the the bottom of the locker looks like hull it will be fine, the oil filled tubes work very well.
NBAS--The communal colostomy bag of the boating community.
 Visit leomagill.co.uk |
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Mad Harold
United Kingdom
228 Posts |
Posted - 09 Jul 2020 : 21:05:13
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Hate showing my ignorance but,what's a chart plotter? and what's it used for?
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trevork
3949 Posts |
Posted - 10 Jul 2020 : 00:21:54
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| I think its all about creating bar charts and pie graphs to decide who is next on the list for ..... maybe not! I'll let one of the techies explain! |
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df
United Kingdom
5991 Posts |
Posted - 10 Jul 2020 : 08:22:35
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In a car you'd call it a sat nav, some do a form of auto-routing but obviously very vague in their route choices as just avoid charted hazards but in general used to display charts(maps) and show your own plotted route and other nav info, they are for sea navigation so not a great deal of use on rivers and canals although I have a topo chart card in my garmin so does fairly well inland as well, on my old boat I had a lowrance which also had a topo card choice but it missed half of the waterways and had to change card over when coming inland.
Posh ones will also overlay radar on the display, mine will show depth if connected to a sounder (my depth sounder is seperate) and other vessels with ais fitted, that bit is very handy when around busy shipping areas, also any incoming DSC distress calls on the vhf has position shown on the chart plotter.
As an add on to my previous post about depth sounders, you can't have two the same on one vessel as they need to work on a different frequency or the returning echos will clash and read gibberish, for info nasa uses 150 khz and echopilot uses 200 khz (from memory-not checked).
NBAS--The communal colostomy bag of the boating community.
Visit leomagill.co.uk |
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Mad Harold
United Kingdom
228 Posts |
Posted - 10 Jul 2020 : 15:29:51
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This post has answered a question that Has been nagging me for some time.
On the bilge under the battery box on my boat(Norman 20) there is what looks like 4inches or so of scaffold tube glassed to the floor.
Been wondering what it was for,and now it seems it was for a chart plotter.
Wouldn't a Satnav from Halfords be simpler? |
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cliveshep
Thailand
1324 Posts |
Posted - 10 Jul 2020 : 15:55:19
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I have to say I found an echo sounder indispensable along with a compass, in shoal waters in thick fog it's all DR and if you can't see your own pulpit then following a compass course allowing for tidal currents and wind is ok but the sounder showing the depth is good especially if you know you need to stay on the, say, 10 fathom line until you hear the fog buoy - as in the approaches to Chichester Harbour.
How do I know this - by swanning up and down in a real pea-souper trying to avoid getting run down by big stuff coming in and out of Southampton!
Finally living the dream!
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cliveshep
Thailand
1324 Posts |
Posted - 10 Jul 2020 : 15:58:19
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quote:
Originally posted by Mad Harold
This post has answered a question that Has been nagging me for some time.
On the bilge under the battery box on my boat(Norman 20) there is what looks like 4inches or so of scaffold tube glassed to the floor.
Been wondering what it was for,and now it seems it was for a chart plotter.
Wouldn't a Satnav from Halfords be simpler?
Almost certainly for an echo sounder, NOT a Chart plotter which on a Norman 20 would be pretty near useless as you'd be unlikely to do much serious passage making off-shore and inland you follow the banks!
Finally living the dream!
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df
United Kingdom
5991 Posts |
Posted - 10 Jul 2020 : 19:14:08
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unlikely to do much serious passage making off-shore and inland you follow the banks!
Nooooo! Not on the east coast Clive, a good passage plan and plotter are essential unless you are very good at navigating by compass, you can be a long way offshore and find the bottom is very close and the better water is closer inshore in a lot of places, the north sea is a big soggy sandpit upto 5 mile out in so many places, I've crossed the ray sand at 16 knots and it's charted as 3m above chart datum.
Don't get the thames estuary wrong at low water, the charts look very different from a map, same goes for the wash, it aint all blue and it all moves in any wind(I've touched the bottom 9 miles out in the wash).
And yes it sounds like you've found a depth sounder transducer not a chartplotter device with your tube in the bilge.
NBAS--The communal colostomy bag of the boating community.
Visit leomagill.co.uk |
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cliveshep
Thailand
1324 Posts |
Posted - 11 Jul 2020 : 07:06:05
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Done the Thames Estuary and the Medway Dave, yes, the estuary has some interesting banks as the tide drops. I admit I was doing it in a twin screw boat with radio, sounder, radar you name it but still seat of pants stuff really.
Oh, and the Blackwater, and coastal up Frinton way, the Broads (boating about in muck on the Broads) and the Fenland waterways - Ouse and Nene. Had a tidal mooring on the Gt Ouse for a couple of years - more bloody mud!
Not fond of the East coast, too much mud at LW to go ashore to let the dog out. South and South West coasts got sand or sand and shingle so one and one's boats don't get so filthy.
Finally living the dream!
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IanM
United Kingdom
2238 Posts |
Posted - 11 Jul 2020 : 07:35:04
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quote:
Originally posted by df
quote:
unlikely to do much serious passage making off-shore and inland you follow the banks!
Nooooo! Not on the east coast Clive, a good passage plan and plotter are essential unless you are very good at navigating by compass, you can be a long way offshore and find the bottom is very close and the better water is closer inshore in a lot of places, the north sea is a big soggy sandpit upto 5 mile out in so many places, I've crossed the ray sand at 16 knots and it's charted as 3m above chart datum.
Don't get the thames estuary wrong at low water, the charts look very different from a map, same goes for the wash, it aint all blue and it all moves in any wind(I've touched the bottom 9 miles out in the wash).
And yes it sounds like you've found a depth sounder transducer not a chartplotter device with your tube in the bilge.
NBAS--The communal colostomy bag of the boating community.
Visit leomagill.co.uk
Almost sounds as if Dave has some sort of first-hand experience of the bottom of the water being too close to the top...
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df
United Kingdom
5991 Posts |
Posted - 11 Jul 2020 : 12:59:09
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I may have had my moments...... 
The bulldog channel in the wash is no longer used as the nav channel and is very silted now, it had been creeping into the buoyed channel for a while, they now buoy the channel to the west of it but I've never used that route as havn't been back to gt.ouse since.
It's the third change of channel in the last 15 years, my first pilot book had the chart overlayed with a sheet of paper and text corrections as it had just changed from cork hole to bulldog channel, now it's daisleys sled that's used.
NBAS--The communal colostomy bag of the boating community.
Visit leomagill.co.uk |
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Fitting a chart plotter
