Trem lead line - needs calibrating before use!

[wonkywinch]

I bought one of these Trem Lead Lines from a large chandler a few years back but never liked the piece of thin board it came wrapped on, very easy to drop it all in the water I feared. Yesterday I decided to cut up a piece of timber and make a better thing for it with a hand hold for easier deploying and retrieving. Once done, I thought I'd just check the calibration of it and was shocked by the inaccuracy. The markers are all about 1.2m apart and by the time I got to 5 of the 50 metre marks, it was already over 6 metres long.

Either my tape measure is wrong or these things are calibrated in 2/3rd fathoms. Fortunately the little plastic marks are easy to unclip and move so I'm just waiting for a rainy day to recalibrate it.

 

[James_Calvert]

Interesting!

Is it possible that in use it would tend to over-read whilst under-way?

So you've got a 20% safety margin built in....

 

[NormanS]

I would have thought that any practical boat owner would be perfectly able to make their own lead line.

 

[vyv_cox]

I made mine years ago, calibrated my new instruments by measuring depth and subtracting draught. Some time later touched bottom unexpectedly. Checked the lead line and found the string had shrunk!

 

[wonkywinch]

I would have thought that any practical boat owner would be perfectly able to make their own lead line.

I'm quite handy but sometimes the cost/benefit doesn't work by the time you've bought 50m of line, 50 bits of coloured plastic etc. Would have never thought of checking it so only discovered error by chance.

All recalibrated now and will adjust depth gauge on boat next visit. Previous owners had either done a factory reset or never bothered with the offset as it was set to zero. Half way between keel and water line!

 

[Hermit]

Does feel like a lot of unnecessary plastic when a knot will do.

 

[Elessar]

I bought one of these Trem Lead Lines from a large chandler a few years back but never liked the piece of thin board it came wrapped on, very easy to drop it all in the water I feared. Yesterday I decided to cut up a piece of timber and make a better thing for it with a hand hold for easier deploying and retrieving. Once done, I thought I'd just check the calibration of it and was shocked by the inaccuracy. The markers are all about 1.2m apart and by the time I got to 5 of the 50 metre marks, it was already over 6 metres long.

Either my tape measure is wrong or these things are calibrated in 2/3rd fathoms. Fortunately the little plastic marks are easy to unclip and move so I'm just waiting for a rainy day to recalibrate it.
View attachment 163024

I simply cant believe you paid for that! Did you buy it on April 1st??

 

[wonkywinch]

I simply cant believe you paid for that! Did you buy it on April 1st??

I bought it a few years back so was likely cheaper and it's had a lot of use as I've chartered dozens of times and never trust how charter companies (or their previous customers) have set the depth reading. It's also been the single cheapest thing I've bought for my boat apart from a shackle ;-)

 

[lustyd]

I have the same one and calibrated the whole thing in about 30 minutes. I started off by checking the lead was tied at exactly a metre and then got curious. Every single one was wrong but no big deal as it was cheap and good enough as well as easy to fix.

 

[wonkywinch]

All done as well. Accurate to 7 decimal places now.

 

[pcatterall]

View attachment 163045

All done as well. Accurate to 7 decimal places now.

And calibrated with load? ( in sea water) ??

 

[Refueler]

Question is :

Lead In
or
Lead Out ?

May sound daft - but its actually a valid question and lead lines are calibrated in either ... it means - is the depth markers with lead bob length incl or not. OK - I realise you are not using a 'deep sea or serious ships leadline where the lead bob can be serious weight and length.

 

[lustyd]

Mine was included and I pulled the line tight to measure. The lead is a good 8-10cm on its own.

 

[Stingo]

Does feel like a lot of unnecessary plastic when a knot will do.

Zackerly. One knot, then two, then three, four and five. Repeat.

 

[wonkywinch]

Question is :

Lead In
or
Lead Out ?

May sound daft - but its actually a valid question and lead lines are calibrated in either ... it means - is the depth markers with lead bob length incl or not. OK - I realise you are not using a 'deep sea or serious ships leadline where the lead bob can be serious weight and length.

Lead included as it usually sits flat on the bottom. Same with my anchor chain marks which indicate chain below water line when chain mark passes over plastic skid forward of the windlass rather than having to peer over the bowsprit to see when mark touches the water.

Calibration of lead line done with line tensioned ;-)

 

[Neeves]

Lead included as it usually sits flat on the bottom. Same with my anchor chain marks which indicate chain below water line when chain mark passes over plastic skid forward of the windlass rather than having to peer over the bowsprit to see when mark touches the water.

Calibration of lead line done with line tensioned ;-)

When deployed the line might be tensioned but if the vessel is moving or there is any current .... it will not be straight.

Calibration will result in overconfidence.

Its a bit like worrying about the accuracy of scope in 6m of water. It matters little, given the other variables, whether you deploy at 6;1, 6.5:1 or 7:1

A safety factor does no-one any harm.

Jonathan

 

[lustyd]

Calibration will result in overconfidence.

Depends what you use it for, surely? Mine is used to calibrate the boat depth guage so I need it accurate. I never use it to find the depth while out, if the electronic one breaks I'll fix it or be overcautious. I'm not out in unknown waters, it's all well charted here so I can just avoid shallow bits using GPS.

 

[wonkywinch]

As lustyd says, as an engineer, I'd rather have my test gear as accurate as can be and then make my own judgement about safety margins depending on conditions. Cadoha even suggests a 10:1 scope in their latest video

 

[lustyd]

He didn't suggest 10:1, he said nobody else was there so he may as well use it all. All good until someone turns up later on

 

[Refueler]

Lead included as it usually sits flat on the bottom. Same with my anchor chain marks which indicate chain below water line when chain mark passes over plastic skid forward of the windlass rather than having to peer over the bowsprit to see when mark touches the water.

Calibration of lead line done with line tensioned ;-)

If the lead is laying flat horizontal on bottom - then Lead is OUT (not incl) ... if Lead is standing on bottom - maybe collecting bottom sample with the tallow (now that's a thing to read up on ... ) then Lead is IN (incl).