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-   -   Rode - adding length with extra lengths of line (http://www.sailnet.com/forums/gear-maintenance/15857-rode-adding-length-extra-lengths-line.html)

Mary51 05-01-2006 02:57 PM

Rode - adding length with extra lengths of line
 
A question from a long time day sailor now venturing into cruising:

I will be anchoring a 31', 10,500 pound displacement sloop.

The rode I have is 50' of 1/4" high test with spliced on 200' of 1/2" nylon. Got two 150' 1/2" gold-n-braid anchorlines with nylon thimble (on sale.)

Could I tie the 1/2" nylon and the two 150' lengths of Gold-N-Braid together make a rode long enough to anchor in deeper water? (In a protected anchorage, no gale force winds.)

Quoting from "The Morrow Guide to Knots":
"Never use two ropes of different materials together, as only the more rigid rope with work under the strain."
AND
"A knot uniting two ropes reduces the strength of the unit to about half that of the weaker rope."

Until I can invest in a completely new, longer rode, is this a workable solution?

Thanks in advance to all with info/advice to share.

sailingdog 05-01-2006 03:59 PM

A couple of questions for you:

1) What kind of anchor are you using?
2) What is the draft of your boat?

The reason I am asking, is I am trying to figure out whether the anchor or the rode is going to be the weak point of your ground tackle system. I'm also trying to see how shallow the water you anchor in can be...

With 250' of primary rode, the chain and 1/2" nylon, at a 10-to-1 scope, you can anchor in about 20' of water, with 5' of freeboard to the bow roller. At a 7-to-1 scope, you can anchor in 30' of water, with 5' of freeboard to the bow roller. Do you see yourself anchoring in anything deeper on a regular basis? What area do you sail in? In most of East Coast of the USA, with the possible exception of Maine, that would be plenty for most anchorages. The West Coast of the USA generally requires longer rodes, and deeper anchorages as I recall.

I am guessing that the 1/2" line on the anchor rode is three-strand nylon, but you don't say specifically. The Gold-n-Braid is braided nylon. Using a knot is a really bad idea, as it does really weaken the strength of the entire rode.

It also sounds as if your anchor rode is really a bit on the light side for cruising. Generally, if you're cruising, going a bit heavier on the ground tackle is a good idea. From Sail Magazine's 1997 Buyer's Guide:

Anchor Weight Guide

BOAT SIZE ANCHOR WEIGHT
Length(ft) Weight(lbs) Bruce(lbs) Danforth*(lbs) Fortress(lbs) Plow(lbs) Yachtsman(lbs)

20-25 2,500 4.4 8-S, 5-H** 4 10 15
26-30 5,000 11 13-S, 12-H 7 15 25
31-35 10,000 11/16.5 22-S, 12-H 7/10 20 35-40
36-40 15,000 16.5 22-S, 20-H 10 25 50
41-45 20,000 22 40-S, 20-H 15 35 65
46-50 30,000 22/44 65-S, 35-H 21 45 75
51-60 50,000 44 85-S, 60-H 32 60 100

Anchor Rode Guide

BOAT SIZE ANCHOR RODE
Length (ft) Weight (lbs) Chain (dia.-inch) Nylon (dia.-inch) Length (ft)

20-25 2,500 3/16 7/16 90
26-30 5,000 1/4 7/16 135
31-35 10,000 5/16 1/2 190
36-40 15,000 3/8 9/16 225
41-45 20,000 7/16 5/8 240
46-50 30,000 1/2 11/16 315
51-60 50,000 9/16 3/4 360

*Danforth is a registered trademark. Similar-style anchors may differ significantly in
performance. **S indicates standard anchor; B indicates high-tensile anchor

Mary51 05-01-2006 05:29 PM

West Coast, 35# Delta
 
Thanks for the response Sailingdog.

I'll be anchoring in much deeper water, and will need 500' of rode to go where I want to go. Draft is 4'.

Mary

sailingdog 05-01-2006 08:12 PM

You need a spool of rope
 
What you need is a spool of 1/2" line...600'. Once you get it, have it spliced to the chain and then you should be all set to go.

If you need it to be modular, you could put eyesplices into the end and then connect them via the splices, but I don't think that will feed well over a windlass, and it is definitely a weak point as well as a snagging risk.

I'm using 300' of 5/8" three-strand nylon spliced to 30' of 5/16" G4 high-test chain for my anchor rode, but it is a bit overkill for my boat. :D

KeelHaulin 05-01-2006 10:06 PM

The longer the scope of the line (the horizontal distance along the seafloor that the boat is from the anchor) the longer distance it would be lying on the bottom. In most anchoring situations you want the length of line to be about 4x the depth you anchor in (good weather conditions) so that the pull on the anchor will be mostly horizontal not vertical. In deepwater conditions like you describe you can reduce this to 2:1 but you should also use extra chain to help hold the anchor down. You need some chain for most situations to keep the rope from abrading on the bottom. I would suggest 150' of chain and 800' of rope (of suitable type/thicknesses for your boat). Remember that overkill is better than getting washed ashore in the night! I would not use the 1/4" for any anchoring situation where I would be concerned if the rope fails (and if it does you will be without an anchor) so best to just make it into a heaving line or similar.

If you join two lines togeter use a reef knot (square not) or a sheet bend with an extra turn of the bitter end around the "larger" line and back through the knot. If you don't understand this I might be able to post a picture. Most knots reduce the strength of the line by 50% or more of the rated tensile strength. Also understand that splices, chafing, age, sun exposure, amount of use, etc are factors that reduce the strength of the rope. For anchor line you should oversize the line significantly to account for the wear/tear and the importance of keeping the boat from loosing it's mooring.

Mary51 05-01-2006 10:21 PM

The 1/4" is high test chain
 
Thanks, KeelHaulin. Was planning on using a sheet bend and securing as you described.

sailingdog 05-01-2006 10:58 PM

The double sheet bend or double becket hitch is much better than the square knot. The square knot tends to weaken the line quite a bit more than a double sheet bend. The single sheet bend can come undone under certain conditions, which is why I recommend the double sheet bend instead, as it is much more secure.

Also, keep an eye on the line for chafe, no line is ever going to be thick enough if chafe isn't controlled. A good source for heavy duty chafe protection is your local fire department. Used fire hose is very good as a chafe protection material.

KeelHaulin 05-07-2006 04:36 AM

Good point on line chafing sailingdog. It seems that on sailboats the line is either getting chafed by the toerail or the line is chafing the deck (if there is not a toerail). If you dont have a toerail install some line chalks to minimize wear/rubbing against the deck.

Another thing to think about when anchoring in deep water Mary is the net weight of the line, chain, and anchor. Once freed from the bottom it might be too heavy to lift without a good windlass or a few people onboard who can work together to heave it aboard.

I still prefer a reef knot to a doubled sheet bend. The reason is that a reef knot will almost never slip free even when slakened (except with polypro line, it's too slippery). The sheet bend works well when the lines are in constant tension (like when towing another boat); but anchor lines can go slack as the boat drifts closer to the anchor. Double sheet bend helps reduce the fear of it untying but I'd feel more secure with a well tied reef knot.

sailingdog 05-07-2006 07:22 AM

The reason I recommend the double sheet bend is that the reef knot, when under a load that surges for an extended period of time can become impossible to untie. Also, the tight bend radius of a reef knot loses more of the rope strength than the double sheet bend generally. No point in having a long anchor rode, if it can't support the strain of your boat pulling on it. A single line is still preferable to two joined lines.

sailingdog 05-07-2006 07:22 AM

The reason I recommend the double sheet bend is that the reef knot, when under a load that surges for an extended period of time can become impossible to untie. Also, the tight bend radius of a reef knot loses more of the rope strength than the double sheet bend generally. No point in having a long anchor rode, if it can't support the strain of your boat pulling on it. A single line is still preferable to two joined lines.


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