Echo Sounder transducer mounting etc

[Sabre27Admin]

Iain C
United Kingdom
181 Posts

Posted - 30/11/2009 : 21:44:21
Please excuse me if this question is as daft as "what make of engine does a Sabre have" or "what is the correct colour for a Sabre spinnaker" but here goes.

Basically, my echo sounder is useless...it just displays a series of random numbers showing there's anywhere between 2 and 800 metres of water under the keel at any given moment! I don't have any photos to hand, but it's an old round Nasa Marine digital instrument, black, with some blue lines/highlights, and red illumination at night.

Power is getting to it fine, and the transducer wire seems OK, so there's nothing obviously wrong with it. The tranducer is mounted under the cabin sole between the V berth in the forepeak, and centrally along the spine of the boat. Viewed from outside the boat, there's a flat recess visible just in front of the (fin) keel, which leads me on to my "daft" question, is this the normal place to mount it, and is this recess part of the original hull moulding, or is it unique to my boat?

Stupid question number two...I was told that the transducer will work through the layers of GRP, and all hull coatings. There's several layers of International VC Tar, plus 4 coats of Micron extra in that spot. Is this likely to be the cause of my problem, or irrelevant?

Again, I should have taken a photo, but from inside, the transducer is very short and stubby, with a wire going into the middle of it and a plastic locknut around the outside. I was going to have a fiddle with it and remove it, but decided against it in case I broke something and the water came in! Any tips on how it should come apart (apart from the obvious "undo the nut, stupid!") gratefully recieved! Someone had told me that a long tube full of oil probably had bubbles in it, but I don't think this is of that design.

I'm in two minds what to do...if a quick dry out and paint scrape sorts it temporarily, then fine. However I am very tempted just to buy a Nasa Clipper Duet, as both speed and depth are currently mounted on the front face of the cockpit below the traveller, making them almost impossible to see, and the reset button on the speed has siezed solid and broken off.

What I'm hoping for is that all transducer mountings on Sabres are identical, and there's some standard thread or similar meaning fitting the Clipper transducer is a doddle.

Wishful thinking I know!

Thanks in advance!
sabre27
178 Posts

Posted - 30/11/2009 : 23:30:27

Hi Iain,

Your questions aren’t daft or stupid!

A lot of Sabres around this age 1972 have a transducer mounted ‘in’ the centreline in front of the keel/s. Mine is one of them. This is a good place from the signal point of view and recessing or otherwise protecting it from being sliced off by a passing baulk of timber is vital!!! There is no ‘normal’ place for one but this would be the ideal. Transducers with their wires intact are very reliable and breakdown is not common. Most problems come from the other end! Ideally don’t coat the face of a transducer with anything, but a bit of paint really won’t make any difference.

A new unit as you describe may well solve your problem. The new transducer will most probably be the same frequency as the old one, 150hz and you may well not need to change it! Talk to Nassa, they are very helpful people. Your transducer will have been inserted (no thread in the hull, just a clearance hole) from the outside into the recess, which sounds like it was moulded into the hull, with a load of sealer and secured with the nut you have seen. Find out what a transducer looks like and all will be clear.

Tubes and bubbles come when you mount transducers on the inside of the hull, not so efficient. Do some homework on the net. Holes in hulls between tides make me nervous. Look after all transducer cables!

If you want more info you know where to find me. Typing takes too long for this!


Paul Howard. S27OA Technical Officer.

dave
United Kingdom
67 Posts

Posted - 01/12/2009 : 19:29:02 Show Profile Email Poster Edit Reply Send dave an AOL message Reply with Quote View user's IP address Delete Reply
I've got the clipper duo installed in gentle nimbus and the paddlewheel log is a pain. It keeps fouling up. The sounder works fine as long as you allow for the offset. When i replaced the transducer i undid the screwed down nut and had to hammer the transducer out after cleaning the hole. The new one fitted snugly and was no problem. Now i dont bother with the log and use the gps for speed and distance.

Bobster
United Kingdom
16 Posts

Posted - 01/12/2009 : 22:32:35
Dave,

If you ever discover how to keep those little paddle wheels turning the whole World will say "Thank You" !!!

Wingsofdawn
10 Posts

Posted - 02/12/2009 : 08:57:55
I changed Wings Of Dawns transducer and log for the Nasa Clipper series last winter. I was surprised at how easy the new equipment fitted. I had to ream a larger hole in the hull for the paddle wheel but the old transducer tapped out of its recess and new one fitted in a treat with no changes. Shame the log has barely worked due to barnacles constantly fouling the wheal. If anyone knows a solution please share it!!

sabre27
178 Posts

Posted - 02/12/2009 : 19:40:04
The solution for jamming paddle wheels.

Buy a car instead!

Or moor up a river in fresh water like Corsair! Ha Ha!

Paul Howard. S27OA Technical Officer.

dave
United Kingdom
67 Posts

Posted - 02/12/2009 : 19:46:37 Show Profile Email Poster Edit Reply Send dave an AOL message Reply with Quote View user's IP address Delete Reply
ive found the answer to jamming paddlewheels nasa marine have bought out a log that interfaces with a gps or a chart plotter so no paddlewheel

dave
United Kingdom
67 Posts

Posted - 02/12/2009 : 19:48:18 Show Profile Email Poster Edit Reply Send dave an AOL message Reply with Quote View user's IP address Delete Reply
its called the clipper easylog

sabre27
178 Posts

Posted - 02/12/2009 : 21:37:11
Arn't we getting a little off course here? A log measures your boat speed through the water. GPS gives your speed over the ground. Chalk and cheese.

I'm out of here.

Paul


Iain C
United Kingdom
181 Posts

Posted - 03/12/2009 : 22:40:22
Thanks for the advice guys. I think I'm going to dry out, give the transducer a scrape and THIN recoat, and see if that sorts it.

Just so I'm clear, do all transducers have a oil tube? Mine does look quite compact...

If it helps at all, you can just see the mounting here...




sabre27
178 Posts

Posted - 03/12/2009 : 23:36:50
Your transducer looks like this:
http://www.nasamarine.com/proddetail.ph ... 0Khz_Depth

No transducer has any tube. When fitting inside the hull (no hole) an open tube must be sealed vertically against the hull, the transducer, as picture above, (they all look about the same) is dropped inside and the tube filled with oil to a level above the 'transducer head' so as to allow the sonic pulse generated by it to pass through the oil, then hull, down to the bed and back again. It will not travel through air, hence the oil. Even bubbles in the water will degrade the echo as you will see when passing over a planing boats wake or in a very disturbed sea.

It is highly unlikely that scraping a few coats of paint off the head will make any difference. That pulse will pass through a GRP hull and yours is in direct contact with the water so ....

Don't paint the transducer head.

Check the cable for damage, right back to the brain box.

Paul Howard. S27OA Technical Officer.

robbyc0
United Kingdom
25 Posts

Posted - 06/12/2009 : 07:48:15
I've got both a transducer on the centreline and an oil bath one. But given the depth reading stays the same if I take the one out of the oil bath and wave it about I suspect that one is redundant!

Peter OD
United Kingdom
50 Posts

Posted - 06/12/2009 : 09:16:21
Hi
I replaced the transducer in Sanda Isle last year whilst putting in a new Clipper echo sounder, in an excess of vigour I tightened the plastic nut too much (hoping to draw the 'ducer right up into the sealant) and the plastic screw bit broke off - when the boat was in the water I realised that it wasn't working - duh! Dangling a new transducer over the side confirmed that it was the transducer - I must have damaged the wire somehow. I bought a new one and the oil-bath kit to mount it in the hull - everything I needed came in the kit and it took me about an hour to fix the tube in the hull with the Plastic Padding provided. I left it until the next day to put the oil in and push the tranducer down through the oil (that took about 3/4 hour and a sore thumb as the clearance is very small) - works perfectly now - no problems at all. And here I am - older, poorer and wiser (some hope! no fool like an old fool!)

Peter O'D Sanda Isle Falmouth

dave
United Kingdom
67 Posts

Posted - 06/12/2009 : 13:23:10 Show Profile Email Poster Edit Reply Send dave an AOL message Reply with Quote View user's IP address Delete Reply
i had a good look at my paddlewheel and it s in a sorry state had a word with my local chandlers and he pulled a bag of nasa clipper log wheels out from under his bench for £4.50 i puchased one and ten minutes later had it fitted
looking at the old paddlewheel which is-was coverd in barnacles the pin is well worn and one of the paddles is slightly damaged no wonder it did not read the speed well
when the boat goes back in the water i shall find out if the log works

Shamal
United Kingdom
41 Posts

Posted - 06/12/2009 : 16:13:46
quote:
Originally posted by sabre27

It will not travel through air, hence the oil. Even bubbles in the water will degrade the echo as you will see when passing over a planing boats wake or in a very disturbed sea.




Yes, we've noticed this, first time was rounding hurst castle, when the depth suddenly dropped to 2 metres in very disturbed (but deep) water. We've also found that it goes haywire in very shallow water and jumps from 1.3 metres to 2 or more, which gives a totally false sense of security (thats another story), - no doubt due to the turbulence caused between the hull and seabed.

Neil & Alison
'Shamal' - Titchmarsh Marina

Iain C
United Kingdom
181 Posts

Posted - 25/01/2010 : 22:03:40
Me again...

Right, on the basis that the reset button is broken off the log, the echo sounder still does not work after lots of fiddling, and even if they did both work, they are mounted at toe height just below the traveller, I've bought a new Clipper Duet setup.

So just to be clear, am I likely to be able to free the existing tranducer out of it's hull recess (it was Mars, not Nasa, I was getting all confused by the space related names!) and more or less swap it for the new Nasa one without significant hull modification (a bit of epoxying or drilling is fine). I shouldn't need a Nasa through hull mounting kit, should I?

Thanks again all!

Iain C
United Kingdom
181 Posts

Posted - 26/01/2010 : 09:50:04
All sorted, spoke to marine super store in Port Solent and they have plenty of both mounting kits available, so either way I will be able to get it fitted at some point over the weekend. I was just worried about the costs of getting the boat slipped on Friday and getting to the end of the weekend and not being able to finish the job. Wish I was about on Monday for the relaunch to check for leaks though!

Iain C
United Kingdom
181 Posts

Posted - 01/02/2010 : 18:17:00
(Post restored after "technical" difficulties meant it got deleted)

Well that was a fun weekend...not!

Saturday-Both the old transducers were wider than the new ones...especially the echo sounder. So with the boat on the launching cradle, I removed the old kit, wedged a suitable flat surface against the outside of the hull, and filled the holes with a mixture of epoxy and colloidal silica. The old holes were tapered, so the new epxy "plug" should be very strong, but I added about 5 layers of glass cloth inside and with a fan heater going full chat it all finally went off in the freezing temperatures!

Yesterday I drilled the new holes, sikaflexed the echo transducer and the paddlewheel tube in place, and then buried the paddlewheel tube nut in epoxy as per the Nasa instructions. Wired in the display and everything seems OK, just keep fingers crossed that nothing leaks, and that the echo sounder works! (I know the log does as a helpful passer by gave it a spin!)

Amazing how a "I'll just fit a new echo sounder" becomes an entire weekend's work!

(Edited to add boat was relaunched this morning and she is still afloat)

Iain C
United Kingdom
181 Posts

Posted - 22/02/2010 : 20:41:53
Well I can't say how nice it was to get sailing for the first time this year and have legible instruments that actually worked! I have to say that Clipper unit is incredibly accurate...as we nosed our way into our mudberth on what we'd worked out was going to be very "on the limit" depth wise, the display went to "0.0" just as Summer Girl's keel hit the "mud moat" that she makes as she settles in on the falling tide. The fact that we's had between 0.2 and 0.4 for the preceeding 150 yards of the approach was always going to be cause for...erm...amusement too!

Cracking sail this weekend, and finally got the kite up for the first time. We left Cowes with a Bavaria 38 and had pulled out 400 yards on them by the time we turned for Portsmouth. OK they did not have a kite, but we were very pleased with our top speed of 6.9 knots through the water!

(Sorry, but these things happen when 4 dinghy racers go off for the weekend!)