Electromagnetic log transducer.

[maxi77]

We used to have EM logs on submarines sticking out on metre long fins to get out of the boundary layer and once calibrated they gave good performance. Calibration involved many runs over the measured mile, dived and surfaced, not the most popular activity. I would prefer to see a small boat doppler log, NASA did have one right back when they started up but had problems so it was dropped. With modern software control I would have though it could work quite well, also having the benefit of bottom lock in shallower water giving true speed over the ground, and water lock in deeper water

 

[GHA]

So has anyone tried the new nasa log yet?

Very tempted

 

[TSB240]

It's a gimmick ...... A lead weighted wooden board and a bit of string on a bobbin were good enough in the past. I saw Dan Snow testing the latest version recently. I think they used their GPS to check they had the right speed

 

[Seajet]

You need to know your distance run *through the water* for a few things, so I venture to differ on the last bit.

So how is the distance run with a paddlewheel log accurate enough for navigation, when it can't get the speed accurate even when not clogged by weed or wee beasties ?

The Smiths unit on my Carter certainly wasn't, then it hardly ever worked at all due to aforementioned beasties or weed.

Long before electronic navigation ( apart from ' are you game for a laugh ' RDF ) I used a trail log - calibrated / checked over a measured mile years ago - and still do as backup when cruising any distance, nowadays of course with GPS as primary aid.

Trail logs can pick up weed too but it's immediately obvious, even at night; a quick flick of the line gets rid of the weed before it can affect the distance run reading - and they don't rely on ships' or any other batteries.

 

[maxi77]

So how is the distance run with a paddlewheel log accurate enough for navigation, when it can't get the speed accurate even when not clogged by weed or wee beasties ?

The Smiths unit on my Carter certainly wasn't, then it hardly ever worked at all due to aforementioned beasties or weed.

Long before electronic navigation ( apart from ' are you game for a laugh ' RDF ) I used a trail log - calibrated / checked over a measured mile years ago - and still do as backup when cruising any distance, nowadays of course with GPS as primary aid.

Trail logs can pick up weed too but it's immediately obvious, even at night; a quick flick of the line gets rid of the weed before it can affect the distance run reading - and they don't rely on ships' or any other batteries.

To be honest up till the advent of GPS most mariners found themselves some what uncertain to their position from time to time certainly enough to bow down to the great god RDF. I can remember spending a whole watch out in the North Western Approaches trying to get a workable fix out of either RDF and we had a good HF/DF set or Consol. My relief took over the task but to little avail until we came back into DECCA range and at least the QM10 didn't pack it in till we got back into Derry

 

[[163233]]

You need to know your distance run *through the water* for a few things, so I venture to differ on the last bit.

Go, on, lets have the list.

I've just forked out 50 quid to replace the paddle wheel that appears to have been destroyed by my own pre-purchase survey, so some justification for it would be good.

 

[Seajet]

To be pedantic the yottie version of Decca was the great miracle people like me had been praying for, then Satnav, then GPS.

To think we used to salivate over the latest RDF kit with a digital frequency selector; then a yotttie friend who worked closely with the RN for Ferranti took one apart and found the frequency knob just turned up the display, the actual selector was only vaguely linked - hence the continued requirement for furious twiddling to get the vague anyway signal - ' and if you tell that to young people today...'

 

[Seajet]

Go, on, lets have the list.

I've just forked out 50 quid to replace the paddle wheel that appears to have been destroyed by my own pre-purchase survey, so some justification for it would be good.

I'd love to hear that one myself, I'd have spent the £50 towards removing the useless thing and glassing over the hole.

If they put the slings over the paddlewheel when lifting her for the survey, I don't know if you have legal redress but you could at least moan at the previous owner for not marking position and /or removing the transducer and for not briefing you and the hoist team - I doubt you'll get more than a moan in but maybe worth it just for that, a decent owner tries to give every bit of info when selling on his pride and joy...

 

[[163233]]

I'd love to hear that one myself, I'd have spent the £50 towards removing the useless thing and glassing over the hole.

If they put the slings over the paddlewheel when lifting her for the survey, I don't know if you have legal redress but you could at least moan at the previous owner for not marking position and /or removing the transducer and for not briefing you and the hoist team - I doubt you'll get more than a moan in but maybe worth it just for that, a decent owner tries to give every bit of info when selling on his pride and joy...

No, no, no. Everyone acted in god faith, it's just one of those things. It could have been a different time and place as well of course, I'm just inferring.
Also, my survey so technically I broke it, if it did happen then.

The real shocker is 50 quid for a paddle wheel.

 

[Seajet]

I'm surprised you got away with £50 !

Anyway either mark the position for the next lift, or better to fit the blanking cap before glassing over, take away the paddlewheel thing in entirety and shoot it.

 

[tean]

So a little bump for this thread. Has anyone any experience with the actual NASA log? Surely I'm not going to be the first to buy one.

 

[lw395]

If you're going to have a speed log, the main interest in it is for small changes to boat speed through the water.
For that reason I would want one with better than 0.1knot resolution.

 

[maxi77]

According to the website no retail product available yet

 

[Seajet]

You need to know your distance run *through the water* for a few things, so I venture to differ on the last bit.

That's because I'm a qualified navigator and engineer so could see from experience hull mounted paddlewheel jobs are of no use for either profession

 

[GHA]

According to the website no retail product available yet

Says available ...
https://www.nasamarine.com/product/electromagnetic-log/
Been available to order on a few of the online sources for a while.

 

[Graham376]

Says available ...

Says "out of stock"

 

[tean]

Plenty of chandlers seem to have them in stock. In the absence of any negative reviews (or indeed any positive ones either) I'm going to take a punt on one as they're not hugely expensive. It doesn't have to be brilliant to be an improvement on a fouled up paddle-wheel.

 

[GHA]

Says "out of stock"

Might be old data on your web browser, maybe try putting a ? at the end in the address bar

https://www.nasamarine.com/product/electromagnetic-log/?

 

[GHA]

Plenty of chandlers seem to have them in stock. In the absence of any negative reviews (or indeed any positive ones either) I'm going to take a punt on one as they're not hugely expensive. It doesn't have to be brilliant to be an improvement on a fouled up paddle-wheel.

:encouragement:

Let us know how you get on

 

[tean]

Will do.