NASA Clipper transducer

Installation of instruments and electrics in the Cape Cutter 19

NASA Clipper transducer

Postby Michiel » Thu Oct 07, 2010 8:21 pm

Hello,

I have acquired the NASA Clipper Depth unit.

Where is the best place to fit the transducer, and does it have to go through the hull, which I do not really want.

Can it be fitted on the inside of the hull, and, if so, how?
I am not sure where the lead is fitted, and surely signal will bounce of that!!
Regards,
Michiel

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Postby Dennis » Thu Oct 07, 2010 11:21 pm

Hello Michiel

No, the Clipper tranducer does not have to penetrate the hull. Mine is mounted on a plastic tube which is glued to the inside of the hull. I posted pictures of the arrangement on the old Yahoo forum. I will e-mail you them. Mine is positioned at the very aft end of the skeg and works well. The plastic tube is filled with vegetable oil and the transducer is immersed in the oil.

Regards

Dennis

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Postby Michiel » Fri Oct 08, 2010 8:16 am

Morning Dennis,

Maybe a silly question, but why immersed in veggi oil?
Will the signal not travel through air?
Regards,
Michiel

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Postby Dennis » Fri Oct 08, 2010 9:34 am

Hello Michiel

Sound travels through air at a different speed than it does through water. This would give a false reading.

More important, there should not be any air gap between the transducer and the GRP hull as this could cause reflections and again false readings. You can glue the transducer directly to the GRP with epoxy, but if you find that it does not work satisfactorily in that position, you will be "stuck" literally.

Why veggie oil?:
It would work with water, but water evaporates. Vegetable oil, is a "fit and forget" solution.

Do you have the NASA instruction manual? If not, it can be downloaded.

Cheers

Dennis
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Transducer fitting

Postby popeye » Fri Oct 08, 2010 10:41 am

Hi Michiel,

I have also bought a NASA Clipper and additional a mounting kit for fitting the transducer as Dennis has explained.

The fitting explenation for this kit suggested to fixe the TD provisional by using chewing gum to find out the right position.

I have fixed the TD in this manner in the lower starboard locker and it works fine since 2 month. Fixing the tube is scheduled for winter.

I will have a look to the fitting explenation and send you a copy of it.
Always fair winds and following seas

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Postby Michiel » Fri Oct 08, 2010 5:07 pm

Dennis, Frank,

Thanks for the explanations.
All clear now.
Dennis, I assume then that your TD just sits in the 'pipe', not fixed.
Regards,
Michiel

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Postby Dennis » Fri Oct 08, 2010 5:47 pm

Hello Michiel

The pipe I used was a piece of domestic waste pipe. I cannot remember the diameter, although it may have been 32mm. The transducer is an easy sliding fit in the pipe.

I made a disc from some 6mm thick acrylic sheet (Perspex) the same diameter as outside diameter of the pipe, with a hole in the centre to take the transducer. The transducer is attached to this disc using the nut provided. This disc forms the "lid" for the top of the pipe.

Here is the url for the Clipper Duet instruction manual . The Depth sounder part is identical to the Clipper Depth: http://www.nasamarine.com/pdfs/Clipper%20Duet.pdf

I hope this helps

Dennis

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Postby Michiel » Fri Oct 08, 2010 6:17 pm

Thanks again, Dennis
Regards,
Michiel

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Postby David Peck » Sat Oct 09, 2010 11:32 am

Hi Michiel,

All Dennis has said is correct. However, I fitted my transducer in the bows just in front of the water tank. The reasons for this location were as follows;

1. The bows of the boat reach the shallows first (but not always!) and enable you to slowly nudge into/over sandbanks. Where I sail (Thames Estuary) the water is very shallow and muddy – you cannot see the bottom in depths as low as 100mm!

2. This location is well away from any electrical interference from the engine.

3. The location is above the level of the bottom of the skeg where excessive water collection could rise above the tube and float the oil out to the surface. This amount of water collection is, however, unlikely unless you leave your boat afloat unattended for long periods of time. The echo sounder would still work as any liquid (including water) will act as an acoustic coupling between the transducer and the hull but oil will not evaporate away.

The installation is, of course, more difficult as you have to feed the wire through more bulkheads. Incidentally, if you do not want to become addicted to “chewing gum” you can use Plasticine to find a suitable location on the hull surface.

It should be noted that echo sounders do not work much below 1 metre! This is really annoying in very shallow water! Nassa Marine is supposed to be working on an improved version but so far, have not introduced anything.

Regards
David Peck
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Postby Dennis » Sat Oct 09, 2010 7:05 pm

Hello Michiel and David

David makes some interesting points, I would like to add some further information to ponder over.

David said
"2. This location is well away from any electrical interference from the engine."

This is true, but for me it has never been an issue. My previous boat also was fitted with Clipper Duet and had two different engines. So with two different boats with three different engines I have not experienced any electrical interference with the transducer sited at the aft end of the boat.

Also
"3. The location is above the level of the bottom of the skeg where excessive water collection could rise above the tube and float the oil out to the surface."

This also is true. However, I had my hand down my skeg last Thursday (a perfectly legal activity I might add;)) looking for a lost battery, I noticed that it was bone dry down there. Mary Ann has been on the water continuously since mid March with no problems from accumulated condensation or leakage etc.

One advantage of siting the transducer in an oil filled tube, is that it does not have to be permanent. If it does not work, you simply site another tube in a different location.

David, how is your diesel installation progressing? I hope you are going to keep us regularly updated with the progress.

Cheers

Dennis

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