How to size rope - Page 2 - SailNet Community

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > General Interest Forums > Gear & Maintenance
 Not a Member? 
  #11  
Old 12-06-2006
ModMMax's Avatar
Member
 
Join Date: Sep 2006
Posts: 36
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
ModMMax is on a distinguished road
Well, I asked the question and you answered it. 3/4 it is. I'll check the cleats for size. Did not know the 16 times the rope diameter cleat thing. Great info. I'll look close at the difference between the 3 strand and the double braid. In fact I should do some research on spicing both types since I intend to splice a loop into one end of each dock line. Thanks to all of you who took the time to teach me something. You guys are great. Thanks and thanks again.
Alvin
Reply With Quote Share with Facebook
  #12  
Old 12-06-2006
Owner, Green Bay Packers
 
Join Date: Sep 2006
Location: SW Michigan
Posts: 10,318
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 11
sailaway21 is just really nice sailaway21 is just really nice sailaway21 is just really nice sailaway21 is just really nice
I'd like to correct what I believe to be a misconception on stretch in dock lines. Stretch is really only desirable as far as tidal change is concerned. If it were not for change of tide I'd recommend wire rope. I know it's not practical. The point is that, when tieing up your boat you do not want it to move at all. It is the movement which is going to cause damage. In adequate number of lines as well as inadequate cleating are going to hurt you before stretch is a factor. Regarding cleating; doubling up on one cleat, while very common, is asking for trouble. If a cleat pulls out and you lose your breast line, the stern line may keep you adequately alongside. If your spring line was doubled up with the breast line on the same cleat you have now lost two lines, and allowed the boat to have a lot more movement.
I recommend dacron over nylon for dock lines as it stretches less and is more abrasion resistant.
I cannot emphasize the point of movement enough. If you look at a merchant ship or cargo secured on deck, or below, you will readily notice that there is no way the lines/wire rope are capable of lifting the vessel or the cargo. They are there to stop movement. Once movement starts, be it a diesel locomotive loaded on deck, or the ship alongside, you're done and it's just a question of how much damage will result.
The same point applies to dock side fixtures. If you have multiple lines running to a single cleat you are only as strong as the cleat and it's securing. Bollards and pilings make much better choices also as they are stronger than a cleat.
A common mistake made is to lead a breast line at too sharp a downward/upward angle to it's dockside fixture. As you walk along the dock you'll see breast lines leading from a vessel at a forty five degree angle down to the dock. With an off dock wind, these lines will part in a vain attempt to keep you alongside. Sometimes that lead is all you have, and may be suitable for benign conditions, but if weather is coming up lead them to the opposite side of the dock, acheiving a more horizontal lead and thereby using their full strength to hold you alongside.
One last item. The time to double up is well before the wind comes up. If your vessel has any significant "sail" area to hull and superstructure you are not going to winch her back alongside. Double up before she's laying two feet off the dock.
Reply With Quote Share with Facebook
  #13  
Old 12-06-2006
Senior Member
 
Join Date: Aug 2006
Location: Arlington, VA
Posts: 1,796
Thanks: 0
Thanked 4 Times in 4 Posts
Rep Power: 9
btrayfors will become famous soon enough btrayfors will become famous soon enough
Thought I'd seen some wild stuff, but this is the most cockamamie idea I've seen in a long time. The idea that you want to tie up a yacht as tight as possible and with as low stretch material as possible is just plain nuts.

While I'm sure someone will come forward to "prove" this theory mathematically, anyone who's been around boats in a marina for awhile knows it's just plain nonsense.

In fact, when you tie up a boat in a slip in such way as to leave the lines a bit loose, you put much less stress on the boat's cleats and on the dock's cleats. Any boat in a slip will move about, due to the wind, current, and wave action. Sometimes, there's quite a bit of movement, particularly up-and-down movement. Loose lines, and stretchy ones, allow the boat to move up-and-down with very little tension on the lines.

If the same boat were tied tight to the dock with non-stretch steel lines, there would be tremendous pull on the cleats, and a passing boat might just cause enough wave action to do some real damage.

Bill
Reply With Quote Share with Facebook
  #14  
Old 12-06-2006
sailingdog's Avatar
Telstar 28
 
Join Date: Mar 2006
Location: New England
Posts: 43,291
Thanks: 0
Thanked 8 Times in 8 Posts
Rep Power: 13
sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice
BTW, three-strand is often a better choice than braided line if you're dealing with rough pilings and such. Rough pilings will pull the outer braid apart, but will not affect three-strand to the same degree.

I'd also agree with btrayfors about some slack in the lines... swell, boat wakes, etc... will make the boat move, and if it is tied up too rigidly...something is going to give... usually something you don't want...and if enough gives...the boat is going to take a beating.
__________________
Sailingdog

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Telstar 28
New England

You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

If you're new to the Sailnet Forums... please read this
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
.

Still—DON'T READ THAT POST AGAIN.
Reply With Quote Share with Facebook
  #15  
Old 12-06-2006
Owner, Green Bay Packers
 
Join Date: Sep 2006
Location: SW Michigan
Posts: 10,318
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 11
sailaway21 is just really nice sailaway21 is just really nice sailaway21 is just really nice sailaway21 is just really nice
Btrayfors,
I think that you missed my point. Most lines stretch too much for good mooring lines. Manila is probably the best mooring line ignoring it's lack of strength. Dacron, preferably laid not 2in1, is a much better choice. All of the above stretch. It is when the vessel starts coming off the dock that it's inertia upon coming back to the dock is going to cause damage. I doubt that you leave any slack lines with impending weather. Deck hardware is going to be ripped out not from too tight a line, but from the weight of the boat coming hard up against it and shocking it. The fact that the line stretches only mitigates the shock somewhat, the solution is to not let the shock occur in the first place.
If it's coming on to blow and your vessel is tied up where the rise and fall of tide is a factor then you simply must tend the lines. There often is no intermediate position that will allow for the tidal change. Of course, long leads as I alluded to above will alleviate much of this.
Reply With Quote Share with Facebook
  #16  
Old 12-06-2006
camaraderie's Avatar
moderate?
 
Join Date: May 2002
Location: East Coast
Posts: 13,878
Thanks: 0
Thanked 2 Times in 2 Posts
Rep Power: 14
camaraderie is a jewel in the rough camaraderie is a jewel in the rough camaraderie is a jewel in the rough
Sailaway...I'm afraid I'm with Trayfors on this one. You need lots of give in your dock lines to reduce the shock loading. I would think that the dock line manufacturers would know about this and there is a reason New England ropes recommends nylon and ALL of the made up dock lines West carries are nylon etc. etc.
If you think you are right about this as I'm sure you do...how about some links to credible sources supporting this approach?
Here's one for my point of view!
http://www.boatus.com/boattech/casey/21.htm
Reply With Quote Share with Facebook
  #17  
Old 12-07-2006
Owner, Green Bay Packers
 
Join Date: Sep 2006
Location: SW Michigan
Posts: 10,318
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 11
sailaway21 is just really nice sailaway21 is just really nice sailaway21 is just really nice sailaway21 is just really nice
Cam,
I am not crusading against stretch per se. What I am referring to though is shock loading or dynamic loading. The American Merchant Seaman's Manual refers to this in chapter one in discussing line in general. The working load of line is not applicable when it is shock loaded. Think karate and cement blocks! When a stretchy line such as nylon is parted the energy imparted to it in the stretching is instantly released in the opposite direction. A mooring line parting on a ship will leave the lines imprint in a quarter inch steel bulkhead, or cut a man in two. Dacron is superior to nylon in this regard as it stretches 60% as much as nylon and is 90% as strong. Chevron USA switched all mooring lines from nylon to dacron for this reason. Most ships use a combination of mooring lines and mooring wires. The synthetic makes for good spring lines and the wires, which stretch only 1%, are better breast lines, head and stern lines.
The point to having your lines tight is that you do not start the vessel moving. Any stretch that is employed in this goal is useful. The problem comes in once the vessel is moving. Now you have the weight of the vessel in play. I was tied up in Bayonne, New Jersey in high wind against a dock with rubber fenders. The vessel came a foot off the dock and, as the gust subsided, returned alongside the dock. The rubber fenders compressed, and a shackle on one of them, previously not in contact with the hull, punched a hole in the hull. Eventually, tugs were called in to keep her alongside. Anotherwords, the working in and out on the mooring lines was going to slowly beat the hull to death. The problem was that we were light (not laden) and there was no good lead available (horizontal) for some good breast lines. On a sailboat in that situation, when you leave the side of the dock your fenders may shift or even fly up and when the boat surges back along side damage will occur. As the oscilation continues you are going to start shock loading the lines and that is where you will start to lose deck cleats and part lines. Most boats are woefully under equipped with cleats for mooring and often have multiple lines to one cleat exponentially increasing the demand on one fixture. I haven't come across too many docking plans for sailboats, something the naval archetect does for all merchant vessels. The safest way to moor any vessel is snugly alongside with, in the case of sailboats, the use of good fenders and the often overlooked fender boards. Fortunately, for most sailboats, it's possible to get good leads on bow, stern and spring lines but those alone will not keep her alongside, hence those pesky breast lines with all their attendant adjusting. The original poster could probably get by with the 5/8" lines as long as he kept the boat alongside and doubled up for weather. He would have more "stretch" with those lines, right up to the point where he beat his hull to death on the dock or the line parted. And it would be the weight of his boat and it's inertia moving about that would cause the problem. In short, stretch is fine until the vessel starts moving relative to the dock and then it CAN become an enemy.
Regarding Casey et al, I find not too much to quibble with except that I have found double-braid, or 2 in 1, to be more subject to chafing, when used in mooring, than laid line. Dacron is significantly more expensive than nylon. And laid line, regardless of material, will stretch more than 2 in 1.
Another inadequacy is the average fender. Most are just filled with air and do a fine job of protecting your hull from scuff marks from aluminum row boats coming alongside. A celled fender, such as a Yokohama float, is much less compressible if not lighter or easier to handle. That's what is used when 'lightering' between tankers offshore. You bring the two ships alongside with the floats between the two and tie up securely. The crew adjust the lines as the smaller tanker sinks to her marks. The fenders don't blow out because of their closed cell construction. Other than collapsability, the average yacht fender is, in my opinion, over-priced junk. You could do as good a job with those foam tubes the kids play with in the pool.
On a somewhat related note: I was tied up in Dutch Harbor to an oil platform loading crude. 70,000 ton tanker deadweight with 18 parts out. It was in January and when the tide turns in the Cook Inlet all the ice comes flowing back to the south from what seems like all the way to Ancorage. The angle of the platform is such that it catches you on the stern quarter. Finally had to stop loading and disconnect the cargo hoses. Good thing too as we parted all 18 and that was with the engine going dead slow astern. Sounded sort of like 18 syncronized shot-gun blasts! Once the ship started moving it was over. No one on deck, or injured, but we junked about a hundred thou. in mooring lines in about 30 seconds!
Reply With Quote Share with Facebook
  #18  
Old 12-07-2006
hellosailor's Avatar
Senior Member
 
Join Date: Apr 2006
Posts: 10,057
Thanks: 0
Thanked 50 Times in 49 Posts
Rep Power: 10
hellosailor has a spectacular aura about hellosailor has a spectacular aura about
Cam, did you notice the NE Ropes doesn't *sell* any manila products? They're low tech and hard to compete with. I suspect the comparison at Boatus for nylon lines is also "versus other synthetics" and again, omitting manila. Manila line does stretch--greatly. Which is why it was the traditional dock line. It's cheap to replace as it ages or chafes or gets tarred. There is, from what I've been told, a lot of variation in the quality depending on the source. And no profit in it for US rope makers and others in developed nations.

I wouldn't run halyards with it, but I'd gladly tie up with it. And maybe keep the more expensive synthetic lines for storm use only, so they stayed fresh.
Reply With Quote Share with Facebook
  #19  
Old 12-07-2006
Owner, Green Bay Packers
 
Join Date: Sep 2006
Location: SW Michigan
Posts: 10,318
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 11
sailaway21 is just really nice sailaway21 is just really nice sailaway21 is just really nice sailaway21 is just really nice
Good manila is very hard to find. Most of what you see is sisal are far weaker material. Manila, which comes primarily from the Phillipines(duh!), was difficult to get in WW II for obvious reasons. The US government experimented with growing it in Missouri I believe with rather mixed results. They did, on the other hand, end up with a close relative that did quite well in the fertile fields of Missouri; marijuanna.
Reply With Quote Share with Facebook
  #20  
Old 12-07-2006
Senior Member
 
Join Date: May 2002
Posts: 2,465
Thanks: 1
Thanked 14 Times in 12 Posts
Rep Power: 12
Sailormon6 will become famous soon enough
I think we're talking about apples and oranges here. We're comparing the lines and procedures for tying up a massive 800' steel commercial freighter with those for a 36' fiberglass private yacht. There is no comparison.

It would make sense to tie up the freighter on short lines, so that it doesn't start to move. When a freighter is in port, the professional captain can assign a paid crew member to monitor the docklines regularly and adjust them as the tide rises and falls. The owner of a private yacht has to go to work 5 days a week, and doesn't have paid crew to monitor the docklines and readjust them in his absence. Adjusting them so that they allow no movement is completely impracticable.

When I bought my first small cruising boat, I decided I'd save a few dollars and use polypropylene for docklines. The first night I slept on the boat, I listened to the sound when the non-stretching poly pro docklines drew taut. It was like trying to sleep inside a kettle drum.

While it's interesting to know how the big guys tie up their boats, we're talking about private yachts here.
Reply With Quote Share with Facebook
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On


Similar Threads
Thread Thread Starter Forum Replies Last Post
propeller size dick/happyours Gear & Maintenance 4 03-11-2005 08:41 AM
Hold That Line Tom Wood Gear and Maintenance Articles 0 10-03-2002 08:00 PM
Choosing and Installing an Electric Windlass Sue & Larry Gear and Maintenance Articles 0 09-06-2002 08:00 PM
Size Matters Don Casey Buying a Boat Articles 0 04-05-2002 07:00 PM


All times are GMT -4. The time now is 12:37 AM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012