What Anchor to use?

LanceB · 05 August 2009, 15:23

Hi All, I'm new to SIBs & the forum & wondered what type & size of anchor would be best for me to get for my boat.

I've got a Honwave T32 - 3.2m Airdeck.

I have bought a couple of 10m x 8mm ropes for mooring etc but also need an anchor I suppose.

I will be using it in the UK - Devon & Cornwall. Planning to take it away for it's first holiday in September to South Devon (Salcombe, Dartmouth etc)

Any advise??

chewy · 05 August 2009, 15:25

A grapnel anchor is ok for a SIB, you'll need 3-5 times the depth of water in rope too.

jyasaki · 05 August 2009, 16:12

Quote:

Originally Posted by chewy

A grapnel anchor is ok for a SIB, you'll need 3-5 times the depth of water in rope too.

Not for sand, it's not. I'd suggest a smallish Bruce knockoff or a small Danforth type.

I agree with the amount of rode, and you should also add 10 feet of fairly hefty chain. Keep the bitter end of the rode attached to the boat (having a float on it makes for a quick getaway.) And wire any shackles so they can't come undone.

jky

LanceB · 05 August 2009, 17:51

Quote:

Originally Posted by chewy

A grapnel anchor is ok for a SIB, you'll need 3-5 times the depth of water in rope too.

Many thanks for your advise

LanceB · 05 August 2009, 17:53

Quote:

Originally Posted by jyasaki

Not for sand, it's not. I'd suggest a smallish Bruce knockoff or a small Danforth type.

I agree with the amount of rode, and you should also add 10 feet of fairly hefty chain. Keep the bitter end of the rode attached to the boat (having a float on it makes for a quick getaway.) And wire any shackles so they can't come undone.

jky

Think its mainly shingle where I'm likley to be using it - will check first when I get there with the locals before buying the wrong sort - Probably the best bet eh!!

JSP · 05 August 2009, 17:56

Wouldn't a sand bag anchor be better for a SIB?
http://cgi.ebay.co.uk/Sand-Anchor-He...d=p3286.c0.m14

chewy · 05 August 2009, 18:32

Quote:

Originally Posted by jyasaki

Not for sand, it's not. I'd suggest a smallish Bruce knockoff or a small Danforth type.

If it was mine I'd be happy using a grapnel anchor, fold up nicely, buy two if your concerned?

I've done bigger dumps than the weight of his boat!

LanceB · 05 August 2009, 19:34

Quote:

Originally Posted by JSP

Wouldn't a sand bag anchor be better for a SIB?
http://cgi.ebay.co.uk/Sand-Anchor-He...d=p3286.c0.m14

Thanks - Never heard of one befor your post!

m chappelow · 05 August 2009, 21:04

only problem with using a sand bag anchor is that it wont dig in to the bottom and the other reason is that sand will lose a third of its weight when submerged ,something like any of thesein the photo will be ok .

LanceB · 05 August 2009, 21:10

Many thanks for all the suggestions posted so far

Lance

JSP · 05 August 2009, 21:13

Quote:

Originally Posted by m chappelow

only problem with using a sand bag anchor is that it wont dig in to the bottom and the other reason is that sand will lose a third of its weight when submerged ,something like any of thesein the photo will be ok .

Could use rocks if sands no good?

m chappelow · 05 August 2009, 22:14

Quote:

Originally Posted by JSP

Could use rocks if sands no good?

problem is rocks and concrete are just about the same ,

codprawn · 05 August 2009, 22:21

Quote:

Originally Posted by jyasaki

Not for sand, it's not. I'd suggest a smallish Bruce knockoff or a small Danforth type.

I agree with the amount of rode, and you should also add 10 feet of fairly hefty chain. Keep the bitter end of the rode attached to the boat (having a float on it makes for a quick getaway.) And wire any shackles so they can't come undone.

jky

I agree but not with the chain. A small bruce or similar holds my 9m RIB very well without the chain - on a sib it should be fine!!!

The grapnels are great in rock - useless anywhere else - even a 7.5kg grapnel caqn be pulled through sand with 1 hand!!!

JSP · 05 August 2009, 22:36

Quote:

Originally Posted by m chappelow

problem is rocks and concrete are just about the same ,

I don't get ya mate.

m chappelow · 05 August 2009, 23:05

Quote:

Originally Posted by JSP

I don't get ya mate.

things in sea water dont weigh as much as they do on land ,even solid objects such as a block of concrete ,,,next time you are wading in the sea try picking up a large boulder you will find its a easier to lift until you try get it out of the water ,,,i have a commercial diving book some where that tells the difference of weights of things like sand /concrete / stones/blocks of metal in sea water ,,,cant remember the exact ratio but for sand its something like a third weght lost in water ......thing is for all the exra weight of carrying a bag of sand or boulder of some sort ,compared to a small anchor its not worth the effort . regards mart

JSP · 05 August 2009, 23:40

Quote:

Originally Posted by m chappelow

things in sea water dont weigh as much as they do on land ,even solid objects such as a block of concrete ,,,next time you are wading in the sea try picking up a large boulder you will find its a easier to lift until you try get it out of the water ,,,i have a commercial diving book some where that tells the difference of weights of things like sand /concrete / stones/blocks of metal in sea water ,,,cant remember the exact ratio but for sand its something like a third weght lost in water ......thing is for all the exra weight of carrying a bag of sand or boulder of some sort ,compared to a small anchor its not worth the effort . regards mart

Now you mention it I had noticed that in the past.

MikeP · 05 August 2009, 23:42

Here's a noddy question then: why is the length of chain important ? I've read a couple of times about having an anchor at the end of chain and then rope, but no explanation as to why...

Poly · 05 August 2009, 23:50

Quote:

Originally Posted by MikeP

Here's a noddy question then: why is the length of chain important ? I've read a couple of times about having an anchor at the end of chain and then rope, but no explanation as to why...

chain helps in a couple of ways:

1. it means the pull on anchor is more horizontal (along sea bed) helping it dig in.
2. it wears much better than rope on a rough bottom so means you are more likely to stay connected to the anchor.

To get the same "direction"/angle of pull you need less scope (total rope/chain) if you use some or all chain. The downsides of all chain are - no stretchiness (thats a technical term!) and the weight penalty.

Poly · 05 August 2009, 23:55

Quote:

Originally Posted by m chappelow

thing is for all the exra weight of carrying a bag of sand or boulder of some sort ,compared to a small anchor its not worth the effort . regards mart

yes might be useful approach if e.g. you arrive at a beach and want to keep your boat afloat... or even if you want to beach the boat with a flooding tide and stop it drifting away. And I guess has advantages if you fold up and carry all your gear at some point - but would you want to rely on it to stop you getting washed out to sea in nasty conditions?

JSP · 06 August 2009, 00:08

Quote:

Originally Posted by MikeP

Here's a noddy question then: why is the length of chain important ? I've read a couple of times about having an anchor at the end of chain and then rope, but no explanation as to why...

What Polwart said plus you can cut the rope at the end of the line if you can't free the anchor off the seabed.