So, we've had great success anchoring in general. However in the recent gusty winds (25knts +) and the bigger tidal range of the Whitsundays, we've slipped a couple of times.
What would you do to improve our setup?
Our primary anchor is a 8kg Lewmar high hold delta. We have two plough back up anchors.
Primary rode is 27m 6mm chain plus 13m 12mm rope.
The obvious options are :
More anchor chain
An anchor kellet to improve the caternary
A different anchor
or don't worry about it and accept the odd reset.
What do you think would be your first improvements?
Oh, and the boat is a little compass northerner 28.
Cheers
Bristle
8kg. Too light. Got a 16kg off sir g for our tophat. Hasnt budged in 30+ with just 9m chain
This is my guide for anchoring
Well, after replacing the 27lb cqr - which is keeping SectorSteve and KiaKaha happy at the moment somewhere around Mollolabah - with a Rocna 10, my gear is:
35lb Manson cqr,
25lb Rocna,
17lb Fort sand anchor,
33 meters of close link 3/8 chain,
12 meters of 3/8 chain, ordinary,
1.5 meter of 25 mm very heavy chain,
330ft of 14mm nylon rode,
100ft of 14mm nylon rode,
2 lengths of 8mm nylon ropes for trip lines 20m each,
a 10' foam float,
a big orange inflatable float,
an 'easy lift' anchor lift device.
If that's not enough, l deserve to be blown away.
The boat is an 8.7 meter Adams and it is 3.8 tons dry.
I keep the long chain at home less l am going to Qld. with coral and rocks.
Agree that 8kg anything is too small for your boat.
For my Compass 28 I use a #3 Sarca Excel with 10m chain then nylon. The only time I had a problem was in the notoriously difficult thick weed around Flinders Island. Otherwise no problems in sand, gravel or mud with steady 30 gusting 40 knots.
Cheers, Graeme
Okay....so the answer is never as simple as a bigger anchor, and is usually cable rather than anchor. If you are dragging, veer more cable - always. If you don't have more cable to veer - you don't have enough cable to anchor in that depth of water.
So having said that I owe at least some sort of an explanation.
In the commercial maritime world the formula used to calculate how many shackles (1 shackle = 27.5m) to veer when anchoring is given as:
Shackles = 1.5 x SQRT(depth of water in meters)
This is based on an all chain anchor, so to anchor in 5 MOW (meters of water) I would need 3.3 shackles (about 92m of chain).
Okay, so 1; obviously not possible on a small yacht and 2; probably overkill for a small yacht - even though our cable is smaller.
We also have a compromise that the major ships don't have - we can use rope as part of our anchoring system. This rope doesn't add to the weight of the anchor system and help with holding but it does absorb the shocks (from gusts etc) that a large cable scope is required for in large ships. Okay so positives and minuses.
Right so what do we do about it in a small yacht. From here I have to give a good part of the credit to Dave1258 on yachting and boating world forums - he has written a very comprehensive post of the maths behind anchors. (It can be found here: www.ybw.com/forums/showthread.php?33805-Anchor-Chain-length). I'm not going to repeat his work here but I'm going to use some of his formulas.
I'm going to ignore the rope you have for the moment for most anchoring calculations are done assuming an all chain catinery.
Using Dave1258's formulas, to determine how much chain you need in a given wind speed based on your yacht:
Chain required: 1/16 * yacht length in m * wind speed * SQRT(depth/specific chain weight)
Yacht length = 8.53
You have given us wind speed of 25+ let's call it 30 for safety.
Chain weight = 0.8kg
Therefore for a 5 MOW anchorage you would need:
Chain = 15.9375 * SQRT(6.25)
Chain = 39.84m
This is for a constant 30 kts and doesn't include any gusts.
Working back the other way, using the amount of cable you already have the wind limit for you would be about 20kts in 5MOW.
Now your rope give you a little bit of flexibility, but more in wind speed gusts rather than anything else.
So in answer to your original question, I would add an additional 13m of chain, or change to a heavier chain.
Hope this helps.
In the Whitsundays you need to have an anchor that can handle large gusts and a system that can handle shock loads.
I would recommend a larger anchor - something like a 25lb Manson Supreme. We bought one on our last Whitsunday trip and have loved it ever since. 8 kilos - 17 lbs is too small for sleeping well. Going small with an anchor is not worth it. A couple of nights at a marina and you have covered the cost difference. Get one as large as you can lift. Then you won't want to stay in marinas as you will trust your gear.
After reading the link I would not worry about chain equations. Every boat has a different way of hanging at anchor, with different windage and different displacement and different pitch moments and none of the this is in the equations. Watch your chain. If it goes close to straight put a longer and thinner nylon snubber on it. Snubbers are essential anyway so just make one that is shorter than the water depth. They also make it so you can sleep better in the forepeak.
As always listen to the boat, watch the chain and feel her react after bullets. Your current anchor is no good but the rest of your gear may be fine - listen and feel to work out if it is. If she behaves smoothly then you are set. If she jerks you need heavier chain or a longer snubber. Better yet, get your snorkel out and jump overboard off Whitehaven in a blow and watch how the anchor works. Observation beats theory any day.
When buying anchors price should not even be considered. Buy the best possible high power holding anchor and buy one size up from the recommended size for your boat. I run a 100lb Ultra. Yes, very very very expensive but I have never had it drag or have had to reset it. I was always a plough man (cqr) but these new high power holding anchors run rings round them.
Select to expand quoteBristolfashion said..
So, we've had great success anchoring in general. However in the recent gusty winds (25knts +) and the bigger tidal range of the Whitsundays, we've slipped a couple of times.
What would you do to improve our setup?
Our primary anchor is a 8kg Lewmar high hold delta. We have two plough back up anchors.
Primary rode is 27m 6mm chain plus 13m 12mm rope.
The obvious options are :
More anchor chain
An anchor kellet to improve the caternary
A different anchor
or don't worry about it and accept the odd reset.
What do you think would be your first improvements?
Oh, and the boat is a little compass northerner 28.
Cheers
Bristle
Had a Delta, dragged a few times (once is too many). Brought a Rocna (about the same weight) and put it on the same chain/rode. Never dragged again.
And I have always put out plenty, unto 6 or 7 times the depth and all chain. Even this didn't get the Delta to work where as the Rocna has been used in tidal situations where the reversal of the current requires the Rocna to reset itself twice a day. And it did it by itself without a hitch. Slept like a baby.
Select to expand quoteCrusoe said..Bristolfashion said..
So, we've had great success anchoring in general. However in the recent gusty winds (25knts +) and the bigger tidal range of the Whitsundays, we've slipped a couple of times.
What would you do to improve our setup?
Our primary anchor is a 8kg Lewmar high hold delta. We have two plough back up anchors.
Primary rode is 27m 6mm chain plus 13m 12mm rope.
The obvious options are :
More anchor chain
An anchor kellet to improve the caternary
A different anchor
or don't worry about it and accept the odd reset.
What do you think would be your first improvements?
Oh, and the boat is a little compass northerner 28.
Cheers
Bristle
Had a Delta, dragged a few times (once is too many). Brought a Rocna (about the same weight) and put it on the same chain/rode. Never dragged again.
And I have always put out plenty, unto 6 or 7 times the depth and all chain. Even this didn't get the Delta to work where as the Rocna has been used in tidal situations where the reversal of the current requires the Rocna to reset itself twice a day. And it did it by itself without a hitch. Slept like a baby.
It makes sense to listen to the anchor manufacturer regarding scope, they have done the testing (I hope). Rocna advise to deploy their Vulcan at 5 to 1, then come up to 3 to 1. That's a bit scary for me, I never go under 4 to 1, and 6 to 1 in the three days of 50 knot winds in the Kepples. I use 10 m of 8 mm chain and the rest nylon. One nice thing with the Vulcan is that even after the extreme weather of that blow it came out of the ground without any effort at all.
I have a 15 pound Manson Supreme on my 2000kg Spacesailor 24 and have about 35 feet of chain, then warp. I've never dragged once. It's set and forget.
Select to expand quotesirgallivant said..
Well, after replacing the 27lb cqr - which is keeping SectorSteve and KiaKaha happy at the moment somewhere around Mollolabah - with a Rocna 10, my gear is:
35lb Manson cqr,
25lb Rocna,
17lb Fort sand anchor,
33 meters of close link 3/8 chain,
12 meters of 3/8 chain, ordinary,
1.5 meter of 25 mm very heavy chain,
330ft of 14mm nylon rode,
100ft of 14mm nylon rode,
2 lengths of 8mm nylon ropes for trip lines 20m each,
a 10' foam float,
a big orange inflatable float,
an 'easy lift' anchor lift device.
If that's not enough, l deserve to be blown away.
The boat is an 8.7 meter Adams and it is 3.8 tons dry.
I keep the long chain at home less l am going to Qld. with coral and rocks.
Just love that anchor john. I reckon i owe you more beers than you got for it. When i get back!
Just got to fraser island. Love getting to new places. New world's and i love the fact i can trust this anchor. Hasnt budged. I was recording over 30knot gusts in mooloolaba and we didnt move at all.
Select to expand quoteAshleyM said..
I have a 15 pound Manson Supreme on my 2000kg Spacesailor 24 and have about 35 feet of chain, then warp. I've never dragged once. It's set and forget.
Anchored once with a 35 lb Manson Supreme on a Bristol 40. Tossed the anchor and then backed off to straighten the chain and dig the anchor in. Nearly got whiplash injury when it dug and straightened the chain.
Value for money I think the Manson Supreme is the best of the modern anchors.
Like the respondents above we traded our not to be trusted anymore and dragging 45lb CQR for a 45 lb Manson Supreme and never dragged again. Only changed the anchor and nothing else. It has even made me stagger about on deck when it digs in. Get the Manson. Deltas do not seem to be as good.
While it may be sour grapes, it's worth reading this if you have a few minutes to spare...
www.petersmith.net.nz/boat-anchors/manson-supreme-anchor.php
Appreciate your experience with the sacra.
However, Rocna had not failed me, sofar, so...........
Whilst awaiting new anchor and rode, I'm carrying out a little experiment.
Tonight I have 27m chain and 13m rope out as my rode. I've shackled my 2nd rode to the point where the splice meets the chain. The second rode has 12m chain and then rope. The idea is that it firstly adds weight and improves the caternary and secondly means that I've effectively got chain all the way in case of stray coral.
What do you reckon? I've never heard of it as a technique.
If you see me drifting past in the night, it hasn't worked!
Cheers
Bristol.
