Bag full of rocks as a dinghy anchor? What weight will be enough?

[Greenheart]

I saw one of these at a chandlery in the last 12 months, and laughed in disbelief at the price, something approaching £30. They didn't even supply the sand/rocks...

...but today it finally occurred to me that something which could hold the boat off the beach in 4ft of water while I take the trolley ashore, would really be a great help when singlehanded. I have a little Danforth anchor, but that's no good for launching in an onshore breeze because I'd already need to be a fair distance out, to set it.

I'm just wondering how large, heavy and robust the bag will need to be, to keep a 6ft beam, 150kg hull stationary in lumpy breakers during a moderate breeze...

...and, is there a really tough, cheap type of bag already available, which will substitute for the one pictured? I still don't want to spend £30 on it. Thanks!

 

[prv]

A sack of rocks on the bottom is really a pretty poor anchor, and thinking back to when I used to sail dinghies the shoreward jerk when a breaking wave hit was not insignificant. I think you'd need too big a bag to be practical.

However, pretty much any old sack or bag ought to do. I'm thinking of the tight mesh / coarse fabric synthetic sacks that my local greengrocer gets their onions in. That would drain and dry out quickly. But even an old pillowcase would work...

Pete

 

[Poignard]

You'd be better off using a lead window sash weight. It would take up far less room and would cost less than the bag.

https://www.mightonproducts.com/products/sash-window-hardware/sash-weights/lead-weights

 

[Greenheart]

I think the overpriced original item was intended for PWCs - which aren't big, but pretty heavy, and must tug on their tethers pretty hard...so I'd like to think ten kilos of gravel (or twenty, or more...there's no shortage on the beach) would be enough, as long as the bag doesn't just fall apart.

I'd be happy to use a biggish sash weight, except that I'd rather not have to carry it round as I sail...and I was imagining a sort of release-cord on the bottom of the gravel-bag, so when I want to haul it up, I can leave the contents on the seabed.

The onion bag sounds good...or perhaps those nylon-fibre mail sacks. Time for an ebay-search.

 

[Poignard]

...and I was imagining a sort of release-cord on the bottom of the gravel-bag, so when I want to haul it up, I can leave the contents on the seabed.
.

A remote operated cod-end knot is what you need

 

[prv]

Onion sacks at £2.39 for five, including postage

Pete

 

[Biggles Wader]

Onion sacks at £2.39 for five, including postage

Pete

Do you want onions with that?

 

[SailorBill]

I saw one of these at a chandlery in the last 12 months, and laughed in disbelief at the price, something approaching £30. They didn't even supply the sand/rocks...

...but today it finally occurred to me that something which could hold the boat off the beach in 4ft of water while I take the trolley ashore, would really be a great help when singlehanded. I have a little Danforth anchor, but that's no good for launching in an onshore breeze because I'd already need to be a fair distance out, to set it.

I'm just wondering how large, heavy and robust the bag will need to be, to keep a 6ft beam, 150kg hull stationary in lumpy breakers during a moderate breeze...

...and, is there a really tough, cheap type of bag already available, which will substitute for the one pictured? I still don't want to spend £30 on it. Thanks!

I can sell you a rock for 50 quid to go in the bag if that's any help

 

[richardabeattie]

You would find it much easier to use a big string bag and fill it with the stuff they use to fill the ballast tanks on trailer sailers.

 

[Dill et Bound]

I have encountered a few PWC owners who regularly use those for mooring up on a sandy beach for a couple of hours.
They work really well..
The only trouble is that after a number of visits what was a nice sandy beach becomes a rock strewn beach that becomes dangerous for drying out and paddling.
They need banning as far as I am concerned..

 

[FWB]

I have encountered a few PWC owners who regularly use those for mooring up on a sandy beach for a couple of hours.
They work really well..
The only trouble is that after a number of visits what was a nice sandy beach becomes a rock strewn beach that becomes dangerous for drying out and paddling.
They need banning as far as I am concerned..

I think a lot of us on here would agree that PWC owners need banning.

 

[NormanS]

I know someone who lost a very expensive RIB which was moored with a net bag of boulders. Let's not get involve in an acrimonious anchor thread, but a bag of stones, must be the worst.

 

[Greenheart]

I'm sad for your mate who lost his boat, Norman...but I was thinking of this only as the answer in a very temporary situation where a real anchor on a long warp, wouldn't work.

It relates to where I launch...deep water close to the edge, invariable onshore breeze, breakers, no buoys or jetties to tie up to, and I want to be able to manage without help.

A remote operated cod-end knot is what you need

Such is the tone of most of the replies here, I'm slightly wary about asking, but...what's that?

I can sell you a rock for 50 quid to go in the bag if that's any help

I'm tempted...if you'll kindly wrap it up in a nice thick stab-proof Kevlar bag. I wouldn't want a £50 rock to get damaged in the post.

You would find it much easier to use a big string bag and fill it with the stuff they use to fill the ballast tanks on trailer sailers.

I got all the way to the end of that line, still believing, my brow knit with concentration.

I retain belief in a stone-bag's usefulness. I'd already have tried anchoring when landing, if my Danforth was usable at such times...but I think a 'sack-weight' would be better.

 

[NormanS]

You do realize that rocks lose about half their weight when immersed?

 

[prv]

You do realize that rocks lose about half their weight when immersed?

Still better than my attempt to anchor a beach inflatable as a small boy, using a "heavy" bottle of water

Pete

 

[prv]

It relates to where I launch...deep water close to the edge, invariable onshore breeze, breakers, no buoys or jetties to tie up to, and I want to be able to manage without help.

Could you not float the boat off the trailer, then beach it while you take the trailer back to the dinghy park, then come back and push it off the beach?

Pete

 

[FWB]

You do realize that rocks lose about half their weight when immersed?

The Phoenicians had that one covered

And so did Noah, apparently from the Ark

 

[Seajet]

I don't think a bag of rocks will hold an Osprey off.

If you do find something which works - and I've a nasty feeling it's going to be very anchor-like, how about a large simple block on it and a long line, so you can pull the boat off the beach and let it back in to get into ?

 

[NormanS]

That looks like a Rock. Nah.

 

[Kelpie]

Hmm. If you are usually using the same slipway, you could rig up something that stays put. A fairly tight length of rope running along the ground, from an anchor point below the LW mark to one above HW. Gives you somewhere to quickly tie the painter to. Make sure it's fairly tight and to one side of the slipway, and then it isn't in anybody's way. Might be good to check with other users so that nobody 'tidies it up'.
I used to launch on a shore that had running moorings on it, and used the running lines in this way.