Anchor Sizing . . . Newbie Grateful for Help !

[ti325v]

Originally Posted by cat man do

The guys in Vietnam
I seriously doubt he will be able to get or afford one of the brand name anchors into the country, especially as I believe they may attract a 100% luxury tax.
My guess it will be a large chunk of chinese iron China Boat Anchor, China Boat Anchor Manufacturers, China Boat Anchor Suppliers and Companies on Alibaba.com

Hi Cat Man...
I have "heard" that danforths are available in Saigon, likely it will be a chinese knockoff.
I do have a little tiny one that weighs about 8 pounds, found it while diving. I will go out to the boat and have a look...certainly was not left behind by somebody from the real world.
I have had some mention of the knock offs having serious quality issues. Any thoughts ?
You are correct about taxes !
And absolute insanity at customs.
If I have a small package sent from overseas, ( Little bag of special screws or some thing), I have to fly to Saigon to get it from customs !
Lunacy !
Thanks for your input

[Jimbo485]

Larry, the 12 mm rope is fine in terms of your strength requirements, but the 20 mm size is much more comfortable on your hands when hauling and handling. 18 mm would be fine and maybe even 16 mm on those little Asian hands? The heavy chain also exceeds your strength requirements but is necessary with a short scope to maintain a close to horizontal approach to the shank.

[cat man do]

Originally Posted by ti325v

Hi Cat Man...
I have "heard" that danforths are available in Saigon, likely it will be a chinese knockoff.
I do have a little tiny one that weighs about 8 pounds, found it while diving.

Nice for the dinghy

I have had some mention of the knock offs having serious quality issues. Any thoughts ?

I would think going well oversize would take care of any quality issues that may appear in a marginally sized anchor.

Like most things in any country, the builders will build for a price, and the price dictates the quality.
China can and has made high quality product, whether you can access that better quality chinese stuff in Saigon, I do not know.

What about some of the smaller shipbuilders in Vung Tau?
Where do they get their gear from?

[Adelie]

Originally Posted by ti325v

Hi Adelie:
Thanks for your answer, I saw that post, looked at anchor sizing charts and had a spinning head ! ( Allow this much for storm condition, this much for muddy bottoms, this much for short rode..... (BTW no problems with the windlass, no dragging....problems with current rig outlined below.

I can see this is a topic of heated debate. Of course I know absolutely nothing on this subject, other then the fact that that my current anchor is made of rebar, welded mild steel plate, rusts like heck and looks butt ugly. It was made by the guy two doors up the street from me by hand for about $60. (I try to keep the boat as pretty as possible).

I saw much of the debate was concerned about storm conditions bottom composition and all the unknown factors. Which in my case are all clearly defined, 100% of the time. And we do have scuba divers on board all the time to deal with any fouls.

I tend to like things small and well designed, ( I understand that small is not a selling point in the anchor department) and I do absolutely love to use the latest and greatest technology from the west, defined as anything that was produced in the last 30 years and proven in the west. The environment I work in is simply make it cheaper, not better.
I have quite possibly the only boat in the entire country with bilge pump float switches, an on demand pressurized water system, those things are just not necessary, labor is cheap people here believe in "work harder, not smarter"... I had some left over bilge pump float switches, my captain was enthralled, and was actually thrilled when I gave him one of my spares.
The electric winch ? leaves people with their heads shaking and muttering about how that is not possible. I was told I had to use an old car rear end with differential and hydraulic pump and motor as a winch, as that is what they use to pull up nets. It certainly works, but has no place on my boat !
It is not an issue of show off, but an issue of how to work efficiently.

70 pounds of welded up mild steel that bends a bit then fractures,when possibly 30 pounds of good design and quality construction will do the job properly means a lot to me. ( My shop faces onto a port, and every day I see anchors being carried to the guy up the road to have more scraps welded onto them to repair them) I recover about 5 broken anchors a year in the mooring areas where the boats are sheltered. Big ones ! (25 meter boats, 250 pound anchors), with the 2 inch rebar shafts snapped clean.
This is the only technology they know.
I like good engineering and quality construction, I think the design of the current anchor is inefficient and not durable.
Also I want to keep the weight down, so I can reduce the chain size, and be sure all the rode fits on the winch.

In short I believe in the right tool for the job, and since my parameters are very clearly defined, I do not need an adjustable wrench with a cheater bar, but a fine quality six point socket. The nut is not rounded off and I know if it is SAE or Metric.

I have access to BIG spring scales, and could wait for a rough day and see how much this rig is actually subjected to.
As you see already I have two reasonable suggestions, with one major difference, rode thickness 12 mm or 20 mm rope...now I have not looked at the numbers but I would image a huge strength difference in strength.

Sorry to be so long winded, for you guys who know about this stuff I think the more details you have, the more easily you can put me onto the "best"answer.
Again thanks all for your input, differing viewpoints and other options are gratefully solicited !
I am under the impression the Danforth may not be ideal as far as durability is concerned, as well as ease of setting it, any thoughts out there ?
Thanks very much for everybody's time.
Larry

OK, I over estimated your current situation, I thought you had a danforth and wanted lighter. Really you want to move up from 3rd world homebrew to 1st world industrial design.

So for a sand bottom, boat always tended, reversing current not an issue, wind against current not an issue, max wind about 20kt, then get a danforth (25 or 43lb, $100-201) or a fortress (15 or 21lb, $325-450).

The danforth would be my pick, you could have it repaired there if damaged. No way for the fortress, welding aluminum is a much higher order of work.

It doesn't sound like you have a windlass, but instead have a reel winch. A windlass pulls the rode in and dumps it in a pile under the windlass, the bigger the space under the windlass, the more rode you can have. A reel winch winds the rode onto a drum, when the drum is full, that's all you can pull in.

Anchoring on chain you can get away with 4 to 1 scope, 3 to 1 if the wind and waves are light to moderate.

Anchoring on line with a bit of chain (5-10m), you want 5 to 1 bare minimum.

With a reel winch you need to figure out how much of each you can fit on the reel. Given your location, and the likelyhood of abuse I would oversize any nylon rode I got.

Given your size of boat 1/4" high test at .84lb/ft or 5/16" standard chain at .13lb/ft would be strong enough. They should be comparable in strength and price.

For nylon 3/4" should be oversize enough.

Keep in mind the chain size is the wire size, there are 2 wires per link with space in between and alternate links are perpendicular to each other so chain takes up a lot more space than you would think.

I would guess that high test chain would give you the best scope on a given sized reel, and that standard chain and rope will be a wash.

Given the difficulty of replacement and the durability issues, I would be inclined to all chain.

If you go with nylon from a local source, check to make sure it is really nylon, and not polypro, polyester or worst some mix. Here's the test, get some fabric dye, mix in water and heat. Dip a test piece in the mixture for a minute or so. Check to see if the fibers have absorbed the dye. If so nylon, if not something else, some yes some no then a mixture. There are other tests with acids or bases, I forget, but this is the easiest. It won't work if the mix is a natural fiber like hemp which will also absorb the color, but if the rope is white it would be hard to mix them without obvious color disparities that would show up to close inspection and perhaps tactile disparities.

If you get chain, get cans of spray on galvanizing. If you are going to fight with customs, might as well do it all at once. Spray galvanizing lets you touch up where the galvanizing wears thru in small areas. Once large areas start to rust out you are just biding your time till the end unless you can find a galvanizer there that can do chain which requires a tumbler so the links don't stick together as the process procedes.

The spray galvanizing will help maintain the anchor too if you get a Danforth. Also you will need it if welding repairs have to be done.

If you have the danforth welded, here are the things that you need to make sure happen.
-If a weld breaks the old weld needs to be ground out. Otherwise the new weld will just be a surface coating over the fracture and the old fracture will the initiation point for the new fracture. Also you wind up with a more compact weld that actually holds better.
-The existing galvanizing needs to be ground back 1/2" or more all around where the new weld will go.
-Pieces need to be pre-heated to 200-400F prior to welding and don't quench them, let them air cool. In the 1st world with quality weld metal preheat's not such a big thing for small pieces, but where the filler metal is unknown this may have a big effect. Once the piece is preheated the heat of welding will maintain the temp unless it is allowed to cool for a significant time, say while taking lunch or a long potty break.

As far as welding rebar, if your neighbor does more work for you, insist on the preheating. There are grades of rebar that don't need preheating, you won't have them there. Doing so may significantly improve your mean time between repairs.

Luck
A

[downunder]

Query regarding your dive site situations? Not familiar with your conditions. Viz/currents/etc.

As a diver supervisor/instructor from my experience I would think the less scope you had the better in many situations for your divers. Allows easy ascent and descent via anchor chain particually if any current. Still good if little or none. In bad current we would often run a line from entry/exit point to anchor chain to assist if could not enter at bow beside chain.

If that were the case a dive vessel is a good argument for fairly heavy anchor and all chain rode to fit the windlass. As you sound as if you are in fairly sheltered waters and always man the vessel (& not overnight) should be able to get away with what is locally available and cheap.

Whilst my personal preference for cruising is a Manson Supreme or SARCA possibly best to go with something heavy and available along lines as Cat-man-do suggests unless cheap Chinese made ROCNA's are available . (if you have followed the anchor threads you will get that last comment otherwise ignore).


I note from your other thread you are going for the 2000W windlass rather than 1000W. Good.

[ti325v]

Originally Posted by cat man do

Nice for the dinghy
I would think going well oversize would take care of any quality issues that may appear in a marginally sized anchor.

Like most things in any country, the builders will build for a price, and the price dictates the quality.
China can and has made high quality product, whether you can access that better quality chinese stuff in Saigon, I do not know.

What about some of the smaller shipbuilders in Vung Tau?
Where do they get their gear from?

Hey Cat Man...
Vung Tau is my source, but a bit difficult to get to, probably will sort it out in Saigon...Thanks for the advice !

[ti325v]

Originally Posted by Adelie

OK, I over estimated your current situation, I thought you had a danforth and wanted lighter. Really you want to move up from 3rd world homebrew to 1st world industrial design.

So for a sand bottom, boat always tended, reversing current not an issue, wind against current not an issue, max wind about 20kt, then get a danforth (25 or 43lb, $100-201) or a fortress (15 or 21lb, $325-450).

The danforth would be my pick, you could have it repaired there if damaged. No way for the fortress, welding aluminum is a much higher order of work.

It doesn't sound like you have a windlass, but instead have a reel winch. A windlass pulls the rode in and dumps it in a pile under the windlass, the bigger the space under the windlass, the more rode you can have. A reel winch winds the rode onto a drum, when the drum is full, that's all you can pull in.

Anchoring on chain you can get away with 4 to 1 scope, 3 to 1 if the wind and waves are light to moderate.

Anchoring on line with a bit of chain (5-10m), you want 5 to 1 bare minimum.

With a reel winch you need to figure out how much of each you can fit on the reel. Given your location, and the likelyhood of abuse I would oversize any nylon rode I got.

Given your size of boat 1/4" high test at .84lb/ft or 5/16" standard chain at .13lb/ft would be strong enough. They should be comparable in strength and price.

For nylon 3/4" should be oversize enough.

Keep in mind the chain size is the wire size, there are 2 wires per link with space in between and alternate links are perpendicular to each other so chain takes up a lot more space than you would think.

I would guess that high test chain would give you the best scope on a given sized reel, and that standard chain and rope will be a wash.

Given the difficulty of replacement and the durability issues, I would be inclined to all chain.

If you go with nylon from a local source, check to make sure it is really nylon, and not polypro, polyester or worst some mix. Here's the test, get some fabric dye, mix in water and heat. Dip a test piece in the mixture for a minute or so. Check to see if the fibers have absorbed the dye. If so nylon, if not something else, some yes some no then a mixture. There are other tests with acids or bases, I forget, but this is the easiest. It won't work if the mix is a natural fiber like hemp which will also absorb the color, but if the rope is white it would be hard to mix them without obvious color disparities that would show up to close inspection and perhaps tactile disparities.

If you get chain, get cans of spray on galvanizing. If you are going to fight with customs, might as well do it all at once. Spray galvanizing lets you touch up where the galvanizing wears thru in small areas. Once large areas start to rust out you are just biding your time till the end unless you can find a galvanizer there that can do chain which requires a tumbler so the links don't stick together as the process procedes.

The spray galvanizing will help maintain the anchor too if you get a Danforth. Also you will need it if welding repairs have to be done.

If you have the danforth welded, here are the things that you need to make sure happen.
-If a weld breaks the old weld needs to be ground out. Otherwise the new weld will just be a surface coating over the fracture and the old fracture will the initiation point for the new fracture. Also you wind up with a more compact weld that actually holds better.
-The existing galvanizing needs to be ground back 1/2" or more all around where the new weld will go.
-Pieces need to be pre-heated to 200-400F prior to welding and don't quench them, let them air cool. In the 1st world with quality weld metal preheat's not such a big thing for small pieces, but where the filler metal is unknown this may have a big effect. Once the piece is preheated the heat of welding will maintain the temp unless it is allowed to cool for a significant time, say while taking lunch or a long potty break.

As far as welding rebar, if your neighbor does more work for you, insist on the preheating. There are grades of rebar that don't need preheating, you won't have them there. Doing so may significantly improve your mean time between repairs.

Luck
A

Hi Adelie, spot on about the reel winch,
Terrific advice here.

[ti325v]

Thanks Cat Man, Bash, Jimbo, GordMay and Astrid, it seems like we are arriving at a consensus !
See it did not take much with so many of the parameters known ! Now I have to go shopping and see what is available, if not..import time !

I can now comfortably say to my captain that we will put on a danforth, about 35-40 pounds, a bunch of HT chain, 12mm rope....Which I will test as described, Big thanks to Adelie for the testing details...Nothing here is as it appears !

Additional clarifications are welcome, but I think I have all the info I need !
Now to go shopping and see what I can find, I dread the though...nobody markets here via internet, so it is going to be a shopping expidition. It took my 17 hours over three days to find rechargeable "C" cell batteries, visited dozens of shops all over the Saigon, only to find them four blocks from my house ! At least I know what I am looking for !
Big thanks again !
Larry

[cat man do]

Originally Posted by ti325v

I can now comfortably say to my captain that we will put on a danforth, about 35-40 pounds

Gee mate, that sounds so very light on 25 ton boat.

I dragged anchor on occasion on my last 2500kg (2.5 ton) boat and that had a 35lb Manson plough.

I currently have a 125 lb Manson Supreme for a 8500kg (9 ton) boat

Your 2000 watt windlass should have no issue picking up a considerably heavier anchor and chain and there's nothing like the security of more gear down when leaving the boat or sleeping aboard if you know there is a bit of weather approaching.

[ti325v]

Hi Cat Man, Your posts are much valued, so I want to ask to clarify...
Please do remember the conditions, Coarse sand bottom 100% of the time, the boat is always attended by three men, there will be a 70 pound skeg aboard in the event we overnight or encounter rough weather.
The boat only goes out in calm conditions, Most of the time I see the skeg just sitting on the bottom holding the boat by its weight alone.
The captain never sets it, just throws the hook and shuts down the boat.
Of course I can go heavier, but import taxes and shipping fees increase a lot with weight.
With that in mind do you still think doubling or tripling the weight is necessary ?
Thanks very much
Larry

[Adelie]

EVERYBODY: he has a reel winch, that means he has limited volume on the drum so size of rode is important to how much length he can put on the drum, and as the drum fills up the motor will struggle more to bring the rode in so weight is an issue too.

Here's the link to the nylon test which is on page 4, photo of test piece on pg 9. My description was a little abreaviated, read the Cordage Institute before proceding.
http://rtm.marine-technology.org/pre...urnal_Pape.pdf

Here's link to a site with different tests: Fibres Guide | How to Identify synthetic fibres in Ropes | TTI Tools & Guides

I checked the codes on welding A36 and 225F preheat should be adaquate for most mild steels. Basically heat it enough to sizzle when water drops land on the piece.

For rebar, per code, preheat to 300F for 3/4" and smaller, 500F for larger. That's for american 60gr rebar. Probably what you have is mild steel rolled into rebar shapes with no heat treating or special alloying so the 225F is probably fine.

[rtbates]

A danforth will work IF YOU DON'T PLAN TO GO TO SLEEP OR LEAVE THE VESSEL UNTENDED. The reason: A 180 degree wind shift will unseat a danforth and they don't reset worth a darn. Also be very wary of bottoms with any debri whatsoever, like clam shells, small rocks, etc. They can and will foul the flukes and the result is they won't hold. Great LUNCH hook, or in the case of my danforh to plug a hole in my fence to keep my dog in.

My old danforth put me on the beach twice in two years because of a 180 degree wind shift with a frontal passage.. I hate danforths and Love Bruce. In my case a 22.5 on a 6k lb boat.

[Adelie]

Originally Posted by rtbates

A danforth will work IF YOU DON'T PLAN TO GO TO SLEEP OR LEAVE THE VESSEL UNTENDED. The reason: A 180 degree wind shift will unseat a danforth and they don't reset worth a darn. Also be very wary of bottoms with any debri whatsoever, like clam shells, small rocks, etc. They can and will foul the flukes and the result is they won't hold. Great LUNCH hook, or in the case of my danforh to plug a hole in my fence to keep my dog in.

My old danforth put me on the beach twice in two years because of a 180 degree wind shift with a frontal passage.. I hate danforths and Love Bruce. In my case a 22.5 on a 6k lb boat.

The OP has made it clear earlier in the thread that the anchor and rode were to be used only in sand, in moderate weather, with one or more paid crew in the boat while paying customers are diving. Otherwise the boat willbe berthed. Also he has made it clear that importing items will be very expensive, and local repairs will be of suspect quality. Consquently the cheapest anchor will incur the least customs fees and the construction needs to be such that repairs will never need to happen or they are simple enough as to be possible in a 3rd world setting.

If you had PAID ATTENTION TO WHAT HE WROTE you would have known that he has a pretty unique situation for which a danforth is arguably the most appropriate choice.

[ti325v]

Hello Rtbates and Adelie:
All input is appreciated, the issue of wind shift certainly is of consequence. I can say with 99.9 percent certainty that the winds here are stable, I am always aware of the location of the boat as I have to return to it while diving. We are located about 6* N, in a very unusual location, where two mid ocean currents meet.
We have a very unusual weather pattern here...Winds from the east 8 months of the year, Winds from the west four months of the year. with a transition period of about a week when the swing slowly through North, I have never once seen them shift 180* while at anchor, and during the transition time no more then 90*, The boat has never yet swung 180 at anchor ( To my knowledge it has never swung more then about 30*) . The boat is not allowed out of the harbor when winds are in excess of about 18 knots, ( Local boats are such garbage they break up and sink with shocking regularity so the army closes the harbor and forces the fishing boats in) and we always anchor on the lee side of any island, as we do not just carry divers but snorkelers as well. Sea conditions are flat on anchor, maximum wave height at anchor is 1 possibly 2 feet, or the snorkelers freak out.
The bottom conditions are 100% sand. ( I have been stupid enough to jump off the boat with out a compass on occasion and been absolutely lost when I had no reference from the sun, as the bottoms are featureless, flat sand, sand, sand, as in Sahara desert without the dunes....sand. Kind of embarrassing when you have customers behind you who are paying to see reef !
Really I cannot image any boat having to confront such consistent anchorages and mild conditions, and it we do get caught out, we, by law must have three crew on the boat and there is the 70 pound skeg that can be deployed with in 3-5 minutes. I do clearly understand that I am setting a perfect anchorage scenario, and I believe it is 100% accurate, having been diving here for a year.
Of course a margin of safety is always appropriate, and I do not want to cut things too close, that is simply stupid. If I ever encountered mud, rubble, an unmanned boat, high winds, strong currents, I would be the first to put 150 pounds over the side and rig up one of the local car rear ends and axles along with the required hydraulics to make it work. It is proven "technology" here...but then they still turn their bilge pumps on manually, they do not have bilge water alarms and carry their fresh water on the roof of the pilot house.....thousands of pounds 15 feet above the water. (In cheap plastic tanks with no baffles !)
If I lose that boat I lose my business, sure it is insured, but they never pay here and the lost income while I build a new new would ruin me both mentally and financially...see the post
http://www.cruisersforum.com/forums/...ase-49854.html
for some funnies of what I went through building her...including some great pix of the build.


I do not want to be the idiot going against good solid advice and if anybody out there is reading this and feels that 35-40 pounds on 12 mm, is simply stupid having read all the details I have posted, please feel free to add a line that says "you are an idiot" and I will reconsider, as I know I do not know and I have come here for advice from experts. People with good solid experience. As I am an expert on the diving subject and do give back in diving forums all the time.

Thanks again everybody !

[Cheechako]

Danforths have immense holding power in sand. Your boat is essentially day anchoring with someone on board. I wouldnt be surprised if a Danforth half the recommended weight would be fine for what you are doing. On the other hand, if you think there is any possxibility that you could be stuck in strong winds for hours. Go with the normal recommended size.