Fitting a NASA paddle-wheel transducer

[chris-s]

We are fitting a new NASA Clipper Duet and after fitting new old paddle wheel thru-hull fitting, when it comes to fitting the new sensor/insert I'm wondering if I should grease up the body a bit like a stuffing gland to help prevent water ingress. Obviously it has a cap with a rubber seal which is designed for the job, and the body of the sensor has a single O-ring whereas the one we removed (different model/brand) had three O-rings, all perished.

Since the boat is only in the water for six months of the year, it will become part of the annual maintenance check anyhow.

Chris

 

[VicS]

We are fitting a new NASA Clipper Duet and after fitting new old paddle wheel thru-hull fitting, when it comes to fitting the new sensor/insert I'm wondering if I should grease up the body a bit like a stuffing gland to help prevent water ingress. Obviously it has a cap with a rubber seal which is designed for the job, and the body of the sensor has a single O-ring whereas the one we removed (different model/brand) had three O-rings, all perished.

Since the boat is only in the water for six months of the year, it will become part of the annual maintenance check anyhow.

Chris

See the instruction manual. ITYWF that it says smear with silicone grease:-

The paddle wheel unit can now be slid into the housing so that it is exposed to the water flow, with the arrow pointing forward along the centre line of the vessel. It is recommended that a little silicon grease is smeared over the rubber O-ring to keep the unit free. Tighten the retaining nut onto the top of the housing, and plug the cable into the ‘paddlewheel’ socket on the display. For added protection it is again recommended that the plug is lightly covered with silicon grease.

 

[MikeCC]

There are 2 O-rings, one up near the screw cap. Light smear of silicone lubricant as suggested. No need to pack it though.

 

[essexsj]

It is quite a tight fit on mine and a light smear of silicone grease aided re-fitting.

I find I need to clear the paddle wheel of fouling a few times through the season - drying mud berth!

 

[Dipper]

It's a good idea to glass in the through hull tube if you haven't yet done so. The outside flange has been known to fail with time and the tube then falls into the boat taking the paddlewheel with it.

 

[pvb]

It's a good idea to glass in the through hull tube if you haven't yet done so. The outside flange has been known to fail with time and the tube then falls into the boat taking the paddlewheel with it.

The installation instructions specify glassing the tube in. I think the cause of flange failure is often that people have used Sikaflex, etc, to seal it, rather than ordinary silicone sealant. Nasa's special blend of plastic doesn't take kindly to Sikaflex!

 

[dolabriform]

The installation instructions specify glassing the tube in. I think the cause of flange failure is often that people have used Sikaflex, etc, to seal it, rather than ordinary silicone sealant. Nasa's special blend of plastic doesn't take kindly to Sikaflex!

Although they won't admit to it. ( don't ask me how I know. )

 

[Refueler]

The installation instructions specify glassing the tube in. I think the cause of flange failure is often that people have used Sikaflex, etc, to seal it, rather than ordinary silicone sealant. Nasa's special blend of plastic doesn't take kindly to Sikaflex!

Also I've seen examples of people overtightening ... they may have a flange still there visually - but its been strained and possibly cracked. The trick is to smear the sealant and then tighten till it squeezes out showing its sealed around - check that there is no gap hull to flange... not to force all so tight it cracks the flange !

Post #4 mentions mud berth ... if you plan it - you can do it afloat easily.

My way if I have to do it (I'm right handed) ... I loosen the assembly till its just a part thread holding .. put blanking cap in right hand ready to slap onto tube ... with my left hand I quickly unscrew last bit and lift out with left hand while slapping cap on and turning to screw on.
I used to do it with left hand - but always found I was skewed ...

 

[Refueler]

Tip for getting GRP ready to glass to ...

Oven cleaner. I have yet to see anything that cleans up GRP like that !!

Years ago - my Snapdragon had a leaking depth tube ... the previous owner just used to top it up and let the oil just cake on and it was UGH !! I tried all sorts of fluids and scraping but it was a real mess.
Wife saw it and said - squirt some of this on and see what happens.

WOW - it foamed up and you could see it lifting the crap ... it took a couple of applications but it came up pristine clean ... or Squeaky clean if you prefer.

I've used it on various boats when asked if I can help ... present boat - used it for same depth tube job actually and also when fitting speed log.

BUT make sure you have plenty of fresh clean water to wash it of with ... first wipe away with mop up cloth ... then thoroughly rinse all traces of it away. It can attack the resin over time if not rinsed away. Dry and you have best surface for bonding to.

 

[chris-s]

Thanks guys. Alas I’ve fitted it with PU40 for now but will add ‘glassing it in’ to my work list.
Chris

 

[C08]

It's a good idea to glass in the through hull tube if you haven't yet done so. The outside flange has been known to fail with time and the tube then falls into the boat taking the paddlewheel with it.

Yes mine failed with a crack but as I had glassed it in there was only a small leak into the boat-good job!

 

[chris-s]

As if I wasn’t concerned enough about getting a good fit/seal now it seems the fitting is likely to randomly break and sink the boat!

 

[Refueler]

As if I wasn’t concerned enough about getting a good fit/seal now it seems the fitting is likely to randomly break and sink the boat!

Funny that thousands of boats fit these and nothing ever happens ....

Just remember that its plastic you are working with ... and don't screw it up so hard as if its metal ! Let the sealant do its job.

 

[Dipper]

Funny that thousands of boats fit these and nothing ever happens ....

Just remember that its plastic you are working with ... and don't screw it up so hard as if its metal ! Let the sealant do its job.

One disintegrated in a boat at our club. Luckily, it happened at launch time so the owner saw water pouring in before the strops were removed and we could lift the boat straight back out again.