Mud-weights for smaller boats

[JennyMorgan]

http://www.lidl.co.uk/en/our-offers-2491.htm?action=showDetail&id=30919&ar=12

[Baitrunner]

Now they look useful. Get me 2 please!!

[Baitrunner]

Now do I need the 5kg or 10kg ones? For a 12ft dinghy?

[brandenjg]

I bought a similar thing a few years ago which turned out to be full of cement so didn't work verywell when put in the water  

[ChrisB]

Good for sliding down the warp to add weight in a blow.

[Guest]

10 hours ago, brandenjg said:

I bought a similar thing a few years ago which turned out to be full of cement so didn't work verywell when put in the water  

Branden raises a crucial point there.

Using any handy looking heavy weight as a mudweight may work really well, or may not, depending on the material inside and any covering skin.

If those kettlebells are made with a metal core and a thin plastic covering, then they'd be ideal for mudweight use, since they would be almost as heavy as a genuine "naked" metal mudweight when immersed in water.

If however, they were filled with concrete or some sort of heavy resin, then their effective weight in water could be less than half of that in air.

It's back to the old problem of trying to cast a mudweight out of concrete in a bucket or stainless steel tub. Cement/concrete is much lighter than an equivalent volume of metal when immersed in water.

I would imagine that those kettlebells probably do have a metal core though, like plastic covered barbell weights, which also make excellent dinghy mudweights, nice and clean to use, very heavy in water, no sharp edges, and a nice big hole through the middle for the rope.

 

[Baitrunner]

Good point guys. I do remember this discussion a few months back.

Which made me realise why my concrete home made job didn't work too well!! Would you believe I was quite good at physics as well!!! 

I might still have a look at them.

[JennyMorgan]

Since the kettle contents are encapsulated in a waterproof membrane then surely their composition is irrelevant? Witness the schoolboy question, which is heavier, a ton of coal or a ton of feathers?

[Guest]

14 minutes ago, JennyMorgan said:

Since the kettle contents are encapsulated in a waterproof membrane then surely their composition is irrelevant? Witness the schoolboy question, which is heavier, a ton of coal or a ton of feathers?

Eureka !!      as Archimedes said when he fell out of his bath.....

Another schoolboy question, displacement.

When immersed in water, objects with the same weight in air will weigh very differently if they have a different specific gravity. (eg weight per cubic inch of volume)

A heavy plank of wood floats, but a piece of metal weighing exactly the same (in air) sinks instantly in water.

Lucky for us, very few boats would float otherwise........

[JennyMorgan]

Mustn't forget all those steel boats, or even those concrete ones.

The contents of the kettle are not immersed in water, they are immersed in plastic!

[Guest]

Luckily the steel and concrete boats "encapsulate" so much air.....

[ExUserGone]

So whos going to buy one to see how much water it displaces, the only real to find out.

[Baitrunner]

Me if I can get there before they sell out.

[webntweb]

Often fancied stopping against the bushes opposite where Chumley & Hawke used to be in Horning (or thereabouts) to do some fishing.

If I dropped my mud weight facing into the current, would a 10kg one on each side of the stern stop the boat from swinging out into the river. Boat is 43ft.

Roy

[MauriceMynah]

Sorry Roy, but I very much doubt it.

[Viking23]

If you have a spring balance, like a fish scale, weigh it in air, then weigh it fully submersed in water.

A lead weight will have a greater density, so will weigh more in water than an equivalent weight of say aluminium or even cast iron. Basic Physics.

 

 

[Baitrunner]

So are most mud weights made of cast iron?

I know you can get the fancy Stainless Steel ones which I assume are all SS and not filled with lead or iron?

[Guest]

1 hour ago, webntweb said:

Often fancied stopping against the bushes opposite where Chumley & Hawke used to be in Horning (or thereabouts) to do some fishing.

If I dropped my mud weight facing into the current, would a 10kg one on each side of the stern stop the boat from swinging out into the river. Boat is 43ft.

Roy

I agree with MM, two 10kg mudweights would only hold a 43ft hull in very favorable conditions, (minimal wind, minimal current.)

A single mudweight has the best holding power because it allows the boat to swing head to wind, or head to current, whichever is greater.

When you try to anchor sideways on to a strong wind or current, the force is much greater to resist, with the full length and side windage of the hull and superstructure.

[Baitrunner]

Just been searching for 10Kg mud weights and only found one place on the broads advertising them for £40. So these weights are a bargain if they work. 

[Guest]

19 minutes ago, Baitrunner said:

So are most mud weights made of cast iron?

I know you can get the fancy Stainless Steel ones which I assume are all SS and not filled with lead or iron?

Yes, it's the cheapest/heaviest compromise.

Lead would be more effective, but would be much more prone to being nicked.

Stainless steel is a surface treatment, rather than a solid metal, so would be "filled" with ordinary steel if solid, which has the same specific gravity as iron, (approx).

[Viking23]

What would be the practabilities of casting your own mud weight, in an upturned stainless steel bucket, say two litre capacity?

Some scrap nuts and bolts, top up with molten lead.

Nice stainless steel eyebolt, with the thread going into the weight, to attach the scrap steel.

This would give a weight close to 23 kg, if pure lead. much less if more scrap iron.

You would have to fix the nuts and bolts or they would float to the surface of the molten lead.

Years ago I used to cast my own lead fishing weights lol...

 

[Guest]

25 minutes ago, Viking23 said:

What would be the practabilities of casting your own mud weight, in an upturned stainless steel bucket, say two litre capacity?

Some scrap nuts and bolts, top up with molten lead.

Nice stainless steel eyebolt, with the thread going into the weight, to attach the scrap steel.

This would give a weight close to 23 kg, if pure lead. much less if more scrap iron.

You would have to fix the nuts and bolts or they would float to the surface of the molten lead.

Years ago I used to cast my own lead fishing weights lol...

It's come up before on here, (with the usual disagreements ! )

It's a perfectly feasible idea, and I'm sure many people have done it.

I've never managed it myself though, because it needs a tremendous amount of heat to keep that much lead molten, and none of my blowtorches or gas rings had enough oomph.

Boatyards would probably use oxy/acetylene, no problem then.

Fishing weights, lead badges and small castings, no problem with average DIY torches.

[Baitrunner]

I'm just off to the church for supplies!!

[webntweb]

1 hour ago, Strowager said:

I agree with MM, two 10kg mudweights would only hold a 43ft hull in very favorable conditions, (minimal wind, minimal current.)

A single mudweight has the best holding power because it allows the boat to swing head to wind, or head to current, whichever is greater.

When you try to anchor sideways on to a strong wind or current, the force is much greater to resist, with the full length and side windage of the hull and superstructure.

Thanks MM and Strowager.

I was thinking of mooring up against the bushes at the side of the river at high water with the bow into the outflowing current using the boats mudweight over the bow and the two 10 kgs off the stern.

My thinking was if there was little wind, the bushes would shelter me from a cross wind, the boat would hold into the current on the mudweight and hoping that the two stern weights would stop any significant drift away from the bank.

Roy

[MauriceMynah]

To be honest Strow, it's surprising how little heat is needed to melt a significant amoumt of lead in a steel wok. I used to do it with a parafin stove, but later went over to a calor gas ring which was rather quicker. I was melting 20lbs at a time, ladeling it out into the frog of a brick. The ingots I made weighed in at 10lbs each and were very easily stacked..

However that wouldn't make that good a mudweight as it is the combination of size and weight that matters. Heavy enough to sink into the mud yet large enough to be difficult to drag through that mud.

We have to remember that it isn't the weight that holds the boat, it is the suction through the mud. Cast iron is the optimum (or stainless steel which has a similar size to weight ratio) material for this.

Those aldi weights might not be dense enough to sink into anything but the softest of silt.