How long should my anchor rope be on a 4.3m tinnie

Page  <12
Post Options Post Options   Likes (0) Likes(0)   Quote petethemeat Quote  Post ReplyReply Direct Link To This Post Posted: 27 Nov 2015 at 4:03pm
petethemeat View Drop Down
Platinum
Platinum
Avatar

Joined: 12 Dec 2006
Status: Offline
Points: 1508
Yes - chain is good. And it does act like a spring to some degree in light/moderate or gusty conditions and reduces the turning circle but it doesn't really make much difference to the holding power.
Lets assume we have a really good anchor. Now lets's assume it's really windy (which happens to be when you need to system to work). The windage from the vessel is going to be very high, meaning the tension between the bow fitting and the anchor is also going to be high. This high tension means will straighten out that rope and chain so it's (in practical terms) a straight line. At this point the chain and rope run in a straight line from anchor connection to bow fitting. (It doesn't have to be as windy as you'd think for this to happen -even running full chain- which a number of cruising boats do). At this point the chain ceases to be of any advantage to the holding power of the anchor, the angle from the anchor simply being function of the scope. Chain is not helping at this point to keep the anchor in the seabed, and these conditions are when we really need to stay put.

I would argue that if your anchor only works with lots of heavy chain, then either it is too small or a poor design. Heavier and/more chain will keep a poor/too small anchor in place but only in light/moderate conditions.

Jeez- I really need to find that article don't I? I remember it being quite good and probably explains it better than I have.

One example of the holding power of these newer anchor designs I saw first hand on my fathers yacht. 
Used to be able to retrieve by driving slowly forward and lifting with the anchor winch. Change to new design and now the anchor winch will stall unless you take up the slack - hold it- an drive forward over the anchor to break it out. Having dived on it the bloody thing is often under the sand with no anchor visible - just the chain coming out. Now that didn't happen with the old one.

Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 27 Nov 2015 at 4:41pm
Steps View Drop Down
Titanium
Titanium


Joined: 14 Oct 2013
Location: Franklin
Status: Offline
Points: 12849
Have to agree on what u have to say...
Except....
Anchors are designed to brake away from the seabed when the tension u talk about... chain lifting right to the anchor shaft..... and regardless of how big the anchor maybe, once the chain has lifted all the way.. u no longer have any grip on the 'bed
At no point should should the chain be all the way off the bed.
And this where in a previous post I mention, ships and even off shore type vessels have weights they slide down the warp...in sevier weather conditions.

Take an anchor out into the veggie garden....no chain just a rope...
now try to drag it at ground level.. it just digs in more... now start to lift at steeper and steeper angles... the anchor shaft is designed to lever against the blades and twist them out of the ground.... regardless of how big it is.

now apply this in real terms...
u have anchored up in a heavy current/ wind.... let out enough to increase the angle to have it hold... the chain will be laying on the bed... maybe not all of it.. but the shaft will be flat on the ground.
Now u start to winch in.. tension increases, anchor still grips, chain lifts, then shaft lifts, and as soon as that happens the boat drifts back.
Nothing to do with the weight of the anchor... all to do with the shaft lifting.
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote petethemeat Quote  Post ReplyReply Direct Link To This Post Posted: 27 Nov 2015 at 5:48pm
petethemeat View Drop Down
Platinum
Platinum
Avatar

Joined: 12 Dec 2006
Status: Offline
Points: 1508
Agree if the anchor shank lifts then you have lost holding but that is quite different to the rode leaving contact with the bottom. It is quite possible for the anchor to remain fast despite the rode lifting as long as that angle is remains relatively acute. (Hence having plenty of scope helps). Part of that is because the anchor shank is an angle to the blades of course, so it is possible to pull (somewhat) above the horizontal while maintaining holding. The rode doesn't need to lie along the bottom to remain anchored, however once that angle become to vertical -then yes-it will break loose. It is perfectly possible to anchor using rope alone as long as scope is reasonable but of course wouldn't be smart as the rope would wear out pretty fast.
So what I am saying is that is perfectly possible for the chain to lift (within limits) without the shank lifting and breaking hold. 

The reason large ships have lots of chain and slide weights down the line is because the have relatively small anchors compared (yes- I know it's not linear) to their size. That is exactly my point- they have to compensate for the small anchor as it would be impossible to carry the size anchor that would do the job without the extra help. In smaller vessels we can can carry anchors that are relatively large to the vessel size so al that extra over-size chain is over-kill if the anchor if up to the job.

edit: this is becoming a big geek-fest isn't it!Embarrassed
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 28 Nov 2015 at 8:19am
Steps View Drop Down
Titanium
Titanium


Joined: 14 Oct 2013
Location: Franklin
Status: Offline
Points: 12849
Basically what several of us have been saying all along..

so it is possible to pull (somewhat) above the horizontal while maintaining holding.

 again I go back to actually put the anchor in the veggie garden...the moment the shaft/ shank, lifts off the ground, the angle of force on the blades changes, and the amount of force required to break it free reduces dramatically.....from the moment it lifts....basic high school maths and  physics also.
This MUST be understood when using/ choosing an anchor system.
Actually go out and try it in the real world.. for get possible theory....the real physics is the same as the real world...
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote Olfart Quote  Post ReplyReply Direct Link To This Post Posted: 28 Nov 2015 at 8:41am
Olfart View Drop Down
Titanium
Titanium
Avatar

Joined: 07 Feb 2008
Location: Wattle Downs
Status: Offline
Points: 5012
Originally posted by phily phily wrote:

How long should a anchor rope be on a 4.3m tinnie? Its just for general fishing around the place . Im going to buy one and don't want to sell myself short short on the metres at the shop?

To get this one back on track.....the basic rule of thumb that I was taught was the anchor warp should equal two and a half times the depth where you intend to anchor as this gives you an allowance for safety. 
So if you are likely to anchor in 30 meters (for example) you would do best with around 75 meters of anchor warp.  If you have room to store a greater length than that, do so - as the extra length is always handy, particularly if you ever need a tow home.

Semper in excreta sumus, solum profundum variat....



Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote petethemeat Quote  Post ReplyReply Direct Link To This Post Posted: 28 Nov 2015 at 1:09pm
petethemeat View Drop Down
Platinum
Platinum
Avatar

Joined: 12 Dec 2006
Status: Offline
Points: 1508
Originally posted by Steps Steps wrote:

Basically what several of us have been saying all along..

so it is possible to pull (somewhat) above the horizontal while maintaining holding.

 again I go back to actually put the anchor in the veggie garden...the moment the shaft/ shank, lifts off the ground, the angle of force on the blades changes, and the amount of force required to break it free reduces dramatically.....from the moment it lifts....basic high school maths and  physics also.
This MUST be understood when using/ choosing an anchor system.
Actually go out and try it in the real world.. for get possible theory....the real physics is the same as the real world...
I think you misunderstand what I was saying. Sure if the shank of the anchor lifts the the anchor loses hold. And yep- pulling along the sea bed is ideal but the angle of pull does not need to be perfectly horizontal (on the sea bed) for the anchor to remain in place. if you are saying that any angle above horizontal will lift the anchor then that's rubbish. I almost always check out the anchor on any vessel I am diving from (it's nice if it's still there when I return) and if it's breezy it's not uncommon to have the chain completely off the bottom with the anchor still buried. Because there is angle between the shank and blade-  a mild angle above horizontal can still induce a downwards force into the seabed. 
Okay I've found the article I was thinking about :

Olfart-  Apologies - yes we are off track- but having fun Wink

Philly-  I reckon grab 100m and cut it 60/40. Use 60 for your day to day stuff connect the extra 40 if it's a bit deep. 100m is a big amount of have sit around and get tangled up and you might not need the extra that often.

Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote pjc Quote  Post ReplyReply Direct Link To This Post Posted: 28 Nov 2015 at 2:39pm
pjc View Drop Down
Titanium
Titanium
Avatar

Joined: 04 Apr 2010
Location: papakura
Status: Offline
Points: 12468
the biggest thing i have found with chain is the weight of the chain,26ft yacht had all chain no rope and yes it would drag even on calm days,my solution was to dump the chain as it was chinese 8mm f@#kall weight to it,went to nz chain at 10mm and 2 boat lenghts and never drag,also depends on botton,broken shell/sand hard to dig in ,overnighting i usually find a bay with mud,drop anchor in to reverse pay out chain then 4 x depth of warp and no problems.
I have a plough and check the lead is still there and point is sharp,ploughs are prone to get shell/cans whatever stuck on tip and will not dig.
anchored coromandel harbour with nw blow and sat for 3 days no problem,but the problem was retrieving,had to go forward fast drive over anchor to break,capstain was trying to stall,nice thick black mud.
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote petethemeat Quote  Post ReplyReply Direct Link To This Post Posted: 28 Nov 2015 at 3:33pm
petethemeat View Drop Down
Platinum
Platinum
Avatar

Joined: 12 Dec 2006
Status: Offline
Points: 1508
biggest problems with ploughs it that in bottoms that are not really soft mud they can drop on their sides and drag and take a few goes to set. Old man changed from plough to new design and bang! Good, solid and quick sets and has to break it out as you describe even from sand let alone mud. 
Ploughs do work (we used them for year) but they are pretty inferior in their setting and holding properties vs what you can get today.
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote pjc Quote  Post ReplyReply Direct Link To This Post Posted: 28 Nov 2015 at 4:49pm
pjc View Drop Down
Titanium
Titanium
Avatar

Joined: 04 Apr 2010
Location: papakura
Status: Offline
Points: 12468
recieved via facebook a week or 2 back 

http://www.sailmagazine.com/cruising/cruising-tips/short-scope-anchoring-in-deep-water
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote phily Quote  Post ReplyReply Direct Link To This Post Posted: 28 Nov 2015 at 8:25pm
phily View Drop Down
Bronze
Bronze


Joined: 24 Nov 2015
Status: Offline
Points: 41
Thanks for all the help guys. 

I think I'm going to get 10 or 15m of chain joined with 100m of 8 plaid rope from anchors ropes and chains. Im thinking of adding a capstan at some stage so that would work with that as well. Thanks for the idea of having the rope split pete the meat. That would work well as i can join it easily when planning on deeper stuff. 

 Now i just have to choose a anchor!
 Few people seem to love the kewene type and then the rocnas seem to get good ratings as well.?? I guess they all do the job as long as you keep a eye on them.
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote mouthu Quote  Post ReplyReply Direct Link To This Post Posted: 28 Nov 2015 at 9:19pm
mouthu View Drop Down
Titanium
Titanium
Avatar

Joined: 20 May 2007
Location: Westie
Status: Offline
Points: 6359
I currently have a 4 metre aluminium pontoon boat and I have as my standard anchor pack a 4kg danforth anchor, 8 metres of 10mm chain and 100 metres of 8mm rope.
 
For my bigger anchor pack for when I'm going away to areas I don't know or I'm going to be on the west coast or I know I might be back anchoring, I have . . .
the standard anchor pack as above and a large grapnel anchor for rocky bottoms, another 8 metres of chain and 120 metres of 12mm floating rope, between my rope and my chain I have a swivel.
 
This hasn't failed me yet, but the lighter one did a couple of years ago.
Yes it was me, I screwed it up for everyone.
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote petethemeat Quote  Post ReplyReply Direct Link To This Post Posted: 28 Nov 2015 at 11:51pm
petethemeat View Drop Down
Platinum
Platinum
Avatar

Joined: 12 Dec 2006
Status: Offline
Points: 1508
Originally posted by phily phily wrote:

Thanks for all the help guys. 

I think I'm going to get 10 or 15m of chain joined with 100m of 8 plaid rope from anchors ropes and chains. Im thinking of adding a capstan at some stage so that would work with that as well. Thanks for the idea of having the rope split pete the meat. That would work well as i can join it easily when planning on deeper stuff. 

 Now i just have to choose a anchor!
 Few people seem to love the kewene type and then the rocnas seem to get good ratings as well.?? I guess they all do the job as long as you keep a eye on them.

Get the Rocna.
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote MikeAqua Quote  Post ReplyReply Direct Link To This Post Posted: 29 Nov 2015 at 12:32pm
MikeAqua View Drop Down
Platinum
Platinum
Avatar

Joined: 29 Jul 2008
Location: Nelson
Status: Offline
Points: 2278
Are you puling the anchor in by hand Phily? 
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote phily Quote  Post ReplyReply Direct Link To This Post Posted: 29 Nov 2015 at 12:39pm
phily View Drop Down
Bronze
Bronze


Joined: 24 Nov 2015
Status: Offline
Points: 41
Yeah I was thinking of pulling in by hand until I had the winch put in.
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote MikeAqua Quote  Post ReplyReply Direct Link To This Post Posted: 29 Nov 2015 at 3:54pm
MikeAqua View Drop Down
Platinum
Platinum
Avatar

Joined: 29 Jul 2008
Location: Nelson
Status: Offline
Points: 2278
Might want to think about how much weight you want to pull by hand ...


Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote phily Quote  Post ReplyReply Direct Link To This Post Posted: 29 Nov 2015 at 4:42pm
phily View Drop Down
Bronze
Bronze


Joined: 24 Nov 2015
Status: Offline
Points: 41
Good call.
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote mouthu Quote  Post ReplyReply Direct Link To This Post Posted: 29 Nov 2015 at 4:56pm
mouthu View Drop Down
Titanium
Titanium
Avatar

Joined: 20 May 2007
Location: Westie
Status: Offline
Points: 6359
There's two ways of getting the anchor back in the boat without pulling it up 'yourself'...
 
1. get the 2nd mate to pull it up, my trick otherwise I generally drift fish.
 
2. 20ltr carboy (chemical container) with an anchor catcher on it and motor away once you've broken the anchor off the bottom, that way you're only pulling the rope back to the boat as the anchor is floating.
Yes it was me, I screwed it up for everyone.
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote MikeAqua Quote  Post ReplyReply Direct Link To This Post Posted: 29 Nov 2015 at 4:59pm
MikeAqua View Drop Down
Platinum
Platinum
Avatar

Joined: 29 Jul 2008
Location: Nelson
Status: Offline
Points: 2278
Even with the bouy trick you still need to be able to pull in the chain and anchor on board by hand.
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 29 Nov 2015 at 6:18pm
Steps View Drop Down
Titanium
Titanium


Joined: 14 Oct 2013
Location: Franklin
Status: Offline
Points: 12849
Would not be without my capstan...
With a capstan one fires up the engine... use the alternator power rather than the battery power....
Even so...guy at on the capstan put arm in direction of the warp, guy on the helm drops in gear in that direction , load comes off the warp, and as the warp angle increases the anchor breaks loose...comes in well with little strain.
The guy on the helm , once the anchor is free keeps the bow into the chop.

Without a capstan or winch  do the same thing..... no need to pull against a current or wind....just the weight of the anchor and chain to pull up... and they are far lighter in the water than on land.

Oh and chain around the capstan... never had one till this boat...some year fine most said  nope... and the reasons just did not hold water to me.
So a few yrs ago asked the expert guys at the boat show...
"Basically fine.. just..."
1/ just watch the screw end of the shackle catching, and your hands.. keep clear
   I filed the end round so would not catch... still keep hands clear... like one is with a bench saw
2/ Hard on the chrome finish...mine was already 2nd hand.. and after a lot more use all yr round, couple small wear dents, chrome still good.
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote MikeAqua Quote  Post ReplyReply Direct Link To This Post Posted: 30 Nov 2015 at 10:48am
MikeAqua View Drop Down
Platinum
Platinum
Avatar

Joined: 29 Jul 2008
Location: Nelson
Status: Offline
Points: 2278
Interesting, my capstan simply will not grip chain.  I've tried 1, 2 and 3 wraps of chain but it simply doesn't grip.

It was installed in 1987 so no chrome left on it ...

Back to Top
Page  <12
Forum Jump
Forum Permissions View Drop Down


This page was generated in 0.289 seconds.

Fishing Reports Visit Reports

Saltwater Fishing Reports
Top of the South Fishing Report - 22/03/24

Tasman and Golden Bay snapper still running hot We are not far away from daylight... Read More >

22 Mar 2024
Saltwater Fishing Reports
Bay of Islands Fishing Report - 22/03/24

Variety is the spice of life On one recent trip, the plan was to spend a... Read More >

22 Mar 2024
Saltwater Fishing Reports
Hauraki Gulf Fishing Report - 22/03/24

Fish where the fish are! Catching fish or just going fishing? I tackle this issue... Read More >

22 Mar 2024
Saltwater Fishing Reports
Inner Hauraki Gulf Fishing Report - 22/03/24

Thoughtful tactics required for better fish Over the course of each year the fishing varies,... Read More >

22 Mar 2024
Fishing bite times Fishing bite times

Major Bites

Minor Bites

Major Bites

Minor Bites