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Go Back   SailNet Community > General Interest > General Discussion (sailing related) > The Perils of Rafting On
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Thread: The Perils of Rafting On Reply to Thread
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Topic Review (Newest First)
09-01-2013 12:41 PM
flandria
Re: The Perils of Rafting On

I notice that a lot of the discussion has shifted to scope etc... The 2 boats "in trouble" did not drag... they were simple beating the sh@# out of each other in a squall with a nasty little chop... and not a skipper on board who knew what to do (such as, break the raft...)
08-31-2013 07:32 AM
JonEisberg
Re: The Perils of Rafting On

Quote:
Originally Posted by MedSailor View Post
I would agree with much of this, though you're really well outside of "anchoring 101" or even 201 here. I usually don't like to mention this kind of stuff unless a lot of qualifications and specifics are mentioned. It's too easy, in my opinion, for someone to mis-read this info and start using 3:1 with rope and a regular sized anchor, for example, which none of the experts you mentioned are recommending.

Even with a pure rope rode there is no benefit to >7:1? Do you have a link to their data? I love anchor geekery.

MedSailor
Rocna's 'Knowledge Base' offers a wealth of information, backed by extensive experience with anchoring in some of the most hostile conditions on the planet...

Catenary & Scope In Anchor Rode: Anchor Systems For Small Boats
08-30-2013 06:58 PM
lowtide
Re: The Perils of Rafting On

Quote:
Originally Posted by MedSailor View Post
I would agree with much of this, though you're really well outside of "anchoring 101" or even 201 here. I usually don't like to mention this kind of stuff unless a lot of qualifications and specifics are mentioned. It's too easy, in my opinion, for someone to mis-read this info and start using 3:1 with rope and a regular sized anchor, for example, which none of the experts you mentioned are recommending.

Even with a pure rope rode there is no benefit to >7:1? Do you have a link to their data? I love anchor geekery.

MedSailor
Try this one. Highlight the variable you wish to change and click and move up or down (took me a while to figure that out)


Fun to play with, but I still like to be able to raise the wind and leave some chain on the bottom.


'
08-30-2013 04:08 PM
MedSailor
Re: The Perils of Rafting On

Quote:
Originally Posted by JonEisberg View Post
No doubt many instances of dragging are due to insufficient scope, but I think the argument can also me made that many cruisers often use more scope than necessary, with no added benefit whatsoever... A lot of recent analysis and real-world experience is leaning towards the conclusion that the generally accepted safe minimum of 7:1 is largely a myth...

Peter Smith of Rocna, with help from the work of Alain Fraysee, has demonstrated there is never any point in going with more than 7 or 8:1... Unless it makes one 'feel better', of course :-)

Beth Leonard & Evans Starzinger consider 3:1 or 4:1 to be their "normal" amount of scope, but will go to 5:1 if expecting a blow...

I believe they have the right approach, using an oversized hook that holds well to short scope to begin with, instead of depending on additional scope alone for holding power... Like Steve Dashew, they believe a cruising boat's main anchor should be sized on the assumption that they might have to be used with 3:1 scope, and I think that recommendation is spot on. In crowded anchorages, I think more drama is due to undersized anchors to begin with, than to 'insufficient scope'...
I would agree with much of this, though you're really well outside of "anchoring 101" or even 201 here. I usually don't like to mention this kind of stuff unless a lot of qualifications and specifics are mentioned. It's too easy, in my opinion, for someone to mis-read this info and start using 3:1 with rope and a regular sized anchor, for example, which none of the experts you mentioned are recommending.

Even with a pure rope rode there is no benefit to >7:1? Do you have a link to their data? I love anchor geekery.

MedSailor
08-30-2013 02:30 PM
smurphny
Re: The Perils of Rafting On

There are certainly times when you can't let out enough scope because of limited room. That is where having an oversized anchor and heavy chain makes a big difference. The increased catenary effect of heavy chain really works in your favor.
08-30-2013 02:20 PM
Tallswede
Re: The Perils of Rafting On

I agree with the oversize anchor approach too. I have an oversized Danforth and it's the biggest that will fit in my anchor locker. I would like to get one of the new style anchors such as a Mantus but I'll need to build a good anchor roller to put it on as I do not want to have to disassemble/reassemble every time I anchor. Danforths hold very well in the right bottom but sometimes don't reset well. I've never had my boat break loose when anchored on my own, though haven't anchored out in anything over 25 knot winds yet.

Kevin
08-30-2013 10:39 AM
JonEisberg
Re: The Perils of Rafting On

Quote:
Originally Posted by MedSailor View Post
NOT dragging rule #1. Always have more than enough scope out BEFORE you need it.

I maintain that not putting out enough scope is the #1 reason most people drag. Sure, there are tight spots where short scope is necessary, but in most cases there is room. What's the real reason NOT to put out 7:1 or 10:1 (with rope) if you can??? Usually there isn't a good reason not to put out a lot of scope. People put out less out of habit I think...

If I put out less than 5:1 with my 3/8 chain, I have to have a mental conversation with myself justifying why I feel it is safe to make an exception.

MedSailor
No doubt many instances of dragging are due to insufficient scope, but I think the argument can also me made that many cruisers often use more scope than necessary, with no added benefit whatsoever... A lot of recent analysis and real-world experience is leaning towards the conclusion that the generally accepted safe minimum of 7:1 is largely a myth...

Peter Smith of Rocna, with help from the work of Alain Fraysee, has demonstrated there is never any point in going with more than 7 or 8:1... Unless it makes one 'feel better', of course :-)

Beth Leonard & Evans Starzinger consider 3:1 or 4:1 to be their "normal" amount of scope, but will go to 5:1 if expecting a blow...

I believe they have the right approach, using an oversized hook that holds well to short scope to begin with, instead of depending on additional scope alone for holding power... Like Steve Dashew, they believe a cruising boat's main anchor should be sized on the assumption that they might have to be used with 3:1 scope, and I think that recommendation is spot on. In crowded anchorages, I think more drama is due to undersized anchors to begin with, than to 'insufficient scope'...
08-30-2013 09:29 AM
jackdale
Re: The Perils of Rafting On

I do not like Danforths at the best times. But in shifting winds and currents they are especially worrisome. As you point out they need to shift and re-set. I have also seen the chain get caught between the stock and the flukes.

I use two anchors in soft bottoms when there is little chance of wind shift; fouled rodes are no fun.

I do not want to start and anchor war, I have used just about every style on the market. You might consider using a modern anchor, a plow or a Bruce. I have had success with most of them.
08-30-2013 08:36 AM
Tallswede
Re: The Perils of Rafting On

We had plenty of scope out, at least for one boat at 7:1 in shallow water. I believe we just had too much windage/weight on the Danforth type anchor and when the wind shift twisted the flukes loose it just skipped along and would not set. Thats why we tryed to use power to slow down the raft and give the anchor time to dig in again. It probably had a mud ball on it and did not want to reset before we got to the next line of boats. This weekend we'll most likely put out two anchors and keep a closer eye to the wind shifts.

Kevin
08-30-2013 01:06 AM
Faster
Re: The Perils of Rafting On

There are many, many anchorages in BC (and, I suspect, WA state) where the textbook scope or more is simply not do-able, either due to congestion, excess depth vs swing room, or nearby obstructions (reefs, rocks, docks, etc).

I'm sure that it's true that most dragging situations are due to inadequate scope, technique, or diligence. However around here we have to 'make do' with what's practical.

The good news is that, esp in summer, up here conditions generally mellow overnight, often to calm, and we have no shortage of good, sheltered options. These same conditions make rafting up a far less stressful situation.
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