NASA log transducer

[bellamia]

Hi, not long now before i launch my boat for the first time, the boat sits on a flush fitting glass fibre cradle which is attached to the trailer. What i am concerned about is the paddle wheel for the NASA log that protrudes below the bottom of the hull, i don't want this to get damaged by the cradle that the boat sits on. Is it possible to release the retainig nut & pull up the paddle wheel so it don't get damaged before the boat goes back onto its trailer, or will this result in a flooded boat when it is launched? Any advice wil be welcome thanks

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[AndCur]

It should be possible to remove the impellor from the skin fitting and blank it off
with the blanking cap then refit the transducer with boat in the water. But a word of warning carefully check the condition of the skin fitting before trying this as they
have been known to fail also if the fitting has not been glassed on the inside i would do this before putting the boat back into the water.


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[bellamia]

Thanks for advice i did wonder if that was possible without taking on to much water. Skin fittings etc are all new and glassed to hull.thanks again

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[milltech]

If you didn't buy them new make sure you still have the blanking cap aboard. I would make the change a few times on dry land so you are comfortable with the proceedure so you'll cope better when the inrushing water appears to be trying to sink you.



<hr width=100% size=1>John
http://www.on-line-marine.com

 

[bellamia]

Thanks for advice again, i have the blanking cap & will try this first on dry land as you say

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[WayneS]

I'm sure that you can draw it up in the fitting without unscrewing the retaining ring. You should be able to get it up so that the paddle is totally within the skin fitting.

Or am I thinking of a different type. Give it a try.

W


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[bellamia]

Thanks for reply i did think of doing that but wondered if the presure of water on the fitting would push it out & i would go down below to a fountain of water?

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[rex_seadog]

NO. Don't do this. I'm not sure what WayneS is thinking of but with the NASA if you want to withdraw the paddle wheel you must put in the blanking cap. Relying on the friction of the 'O' rings to hold the paddle wheel unit in place would certainly risk your first launch being your last!
Once it's in the water you can replace the blanking plug with the paddle wheel but this requires a little dexterity but mainly confidence. You will get quite a gush of water but I can usually manage it with only about a pint of water coming into the bilges.

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[Avocet]

If I get what you're saying, you only want to pull the transducer up when you're going on the cradle?

We had a trailer sailer that usd to sit in a mould of its own bottom on the trailer and had exactly the same problem when launching / recovering. We used to unscrew the retaining ring holding the NASA transducer in its tube and pull it half way up. Like the previous poster, I assumed it wouldn't stay put but it always did. Nevertheless I made a little check strap (bit of shoe lace) with a loop that went round one of the arms sticking out of the transducer. That said, we never needed it. Note that if you DO pull the transducer out while afloat, you get a surprisingly large jet of water and it's very un-nerving the first time you do it and start fumbling with the blanking cap in a blind panic!

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[alahol2]

I have heard someone say that you could tape a (floppy) polythene tube over the transducer skin fitting. Presumably you can then put your arm inside and, as long as the end remains above the waterline, you wouldn't be liable to sink the boat when removing caps and inserting the transducer. Anybody actually tried this, and does it work?

<hr width=100% size=1>I really would rather be sailing...

 

[pete]

Hi
On my log fitting (Plastimo Navman) it is possible to pull the impellor into the skin fitting without unscrewing the retaining cap and push it down again when needed although occasionaly a bit of silicone grease on the O ring would be a good idea.

Pete

<hr width=100% size=1>Artificial intelligence is no match for natural stupidity

 

[bellamia]

Thanks for all your help, should be ok know

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