Transom Mount a Nasa Target Log Paddlewheel

[dolabriform]

Hi all

Does anybody know if it's possible to mount this off the transom rather than cutting a hole in the hull?

Thanks

David

 

[pvb]

It's certainly not recommended, the readings would be rather random.

 

[Norman_E]

If you have an inboard engine then putting the paddlewheel anywhere behind the propeller will give you some very interesting and totally inaccurate speed readings. Even without an engine turbulence from the transom is likely to render the readings pretty random as PVB says. The paddlewheel should be mounted ahead of the keel on a yacht, and on a powerboat it should also be mounted well forward, though there are different rules for planing boats where part of the hull lifts clear of the water. The only way to do a proper job is to drill the hull.

 

[jakeroyd]

I've given up using my paddlewheel log.
Whatever I do , including antifouling the paddlewheel etc. does not work.
The sea beasties disable it in about a month or so and I have to get bodily in my forward hull compartment to get it out and clean it.

Been thinking of putting an inline Bulgin type plug on it , so i can remove it and clean it without staying hunched up in the compartment.

 

[Seajet]

I've given up using my paddlewheel log.
Whatever I do , including antifouling the paddlewheel etc. does not work.
The sea beasties disable it in about a month or so and I have to get bodily in my forward hull compartment to get it out and clean it.

Been thinking of putting an inline Bulgin type plug on it , so i can remove it and clean it without staying hunched up in the compartment.

+1, paddlewheel logs are hopeless due to collecting weed, beasties taking up residence or simply being in the boundary turbulence layer between boat and water.

Stick it on the transom if you must, but it's certainly not worth cutting a hole in the bottom of your boat for it.

I had a sailing boat with a paddlewheel transducer, it was useless - on my long term boat I have a ' no holes in the hull ' policy which certainly helps me sleep easier - I just use the GPS for speed over ground, and on holiday cruises the Wasp trail log - I don't bother with the trail job around the Solent as I know the boat and GPS is quite enough, if I trailed a log some silly sod would do their best to get it entangled - I recommend trying to get a secondhand Walker or Wasp for offshore stuff BUT when I got mine I did trial runs to calibrate them against measured mile posts on shore, both ways - like all instruments, useless or even dangerous until calibrated.

There is also the point, there is a well deserved expression, ' Only trust NASA kit where no moving parts are involved '...

 

[dolabriform]

+1, paddlewheel logs are hopeless due to collecting weed, beasties taking up residence or simply being in the boundary turbulence layer between boat and water.

Stick it on the transom if you must, but it's certainly not worth cutting a hole in the bottom of your boat for it.

I had a sailing boat with a paddlewheel transducer, it was useless - on my long term boat I have a ' no holes in the hull ' policy which certainly helps me sleep easier - I just use the GPS for speed over ground, and on holiday cruises the Wasp trail log - I don't bother with the trail job around the Solent as I know the boat and GPS is quite enough, if I trailed a log some silly sod would do their best to get it entangled - I recommend trying to get a secondhand Walker or Wasp for offshore stuff BUT when I got mine I did trial runs to calibrate them against measured mile posts on shore, both ways - like all instruments, useless or even dangerous until calibrated.

There is also the point, there is a well deserved expression, ' Only trust NASA kit where no moving parts are involved '...

Thanks for this... I was originally thinking about a no holes policy.. then I bought a Nasa Log...

Guess I'm gonna sell it !

Anyone want a NASA Log ???

 

[TSB240]

Thanks for this... I was originally thinking about a no holes policy.. then I bought a Nasa Log...

Guess I'm gonna sell it
Anyone want a NASA Log ???

Dont be too hasty.

Trailing log may be more accurate than any thru hull impeller but then how many people continue to use a trailing log for primary navigation in the GPS age? Our measured mile is still marked on our chart and plotter but unfortunately the visible transits lines have not been maintained for over 15 years!

All the cruising boats I have sailed on have had thru hull logs. I would think that it is been a standard supply on most boats for quite some time....
Having a thru hull on a half tide mud berth based boat is probably not a worthwhile hobby given the hassle of withdrawing it and keeping it clean at the end of each and every outing.

I would guess that we have had ours blocked with semi floating debris or weed a couple of times a year maximum and this is usually sorted by either going in reverse or swivelling the thru hull through 180 degrees for a short while. No need to worry about cleaning. A quick calibration check in slack water against your GPS SOG is easily carried out to check for impeller malfunction.

Our log provides us with great information when coastal hopping around the North Wales. Using a combination of boat speed and SOG allows one to actually make a measure of the tidal flow and how it is affecting you. Quite surprising in our parts how moving inshore just few meters can gain you an extra knot against a tide. Mind you It also means I am usually first at the bar!

I suppose if your Tryphobia is so bad you could always us the well tried method of measuring your hull speed by timing how quickly your waterline length takes to pass a floating object?

According to this reference it may be valid fear?

"Boats are full of holes, from antennas on the hardtop to transducers on the bottom. So why do we fear them?
There’s merit to this fear. According to marine survey firms, leaks at through-hulls are estimated to be the cause in 18 percent of sinkings while under way. The numbers are worse at the dock, where failures of fittings below the waterline account for a full 50 percent of sinkings. BoatU.S. insurance claims back up the data. According to BoatU.S. numbers, fittings cause 44 percent of dockside sinkings and 16 percent while under way."


I think a good maintenance regime should alleviate these fears and ensure your thru hull gives you more pleasure than pain.

 

[Seajet]

The paddlewheel log I had ( a Smiths job but they all seem the same in this regard ) was on a fin keeler kept in deep water.

Even if not impeded by weed or wee beasties - the thing needed withdrawing and clearing before and sometimes during every sail - it was simply not accurate enough for reliable navigation for say cross- Channel Solent / Poole to Channel Islands distances.

Towed logs are by no means the infinite answer, one has to keep an eye on the spinner astern and ensure it hasn't collected weed - a sharp jerk on the line usually clears it - the thing thrums and vibrates through the boat, but I find that comforting as to our progress when I'm off watch in my bunk, if it all went quiet I'd know something was wrong and be out of my bunk like a Trident missile wondering where the crew had gone !

If the measured mile posts near you have gone, you could use GPS to calibrate it with a bit of an effort, but I can guarantee you'd regret cutting a big hole in your hull just for the sake of an immediate ' Oh look we're going a bit faster / slower ' when an adequate knowledge of what the tide is doing and a GPS will tell you...