Cruisers Forum

  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
Thread Tools Search this Thread Rate Thread Display Modes
Old 15-11-2008, 18:01   #1
Writing Full-Time Since 2014
thinwater's Avatar

Join Date: Nov 2008
Location: Deale, MD
Boat: PDQ Altair, 32/34
Posts: 9,764
Prussic hitch to secure achor bridle

Why not keep a short loop clipped to a ~20' line to provide for bridle adjustment?

This is generally a rock climber knot, but it grips well, is often used in life-or-death situations, and is very well proven. You can tie it with one hand while hanging from a cliff - or a forestay - and can't get it wrong. This seems simpler than a knot (either icicle or rolling hitch) that takes some forming to be reliable.

The negative - or positive - is that it will not release under load. It is required that the prussic line be smaller than the line it is gripping, but it is doubled.
thinwater is offline   Reply With Quote
Old 15-11-2008, 18:40   #2
Moderator Emeritus
David M's Avatar

Cruisers Forum Supporter

Join Date: Sep 2007
Location: Eastern Tennessee
Boat: Research vessel for a university, retired now.
Posts: 10,406
Very interesting and potentially useful knot. Thanks for that.

Life begins where land ends.
David M is offline   Reply With Quote
Old 16-11-2008, 01:46   #3
Senior Cruiser
GordMay's Avatar

Cruisers Forum Supporter

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 49,837
Images: 241
Yes, that’s the ‘basic’ Prusik, or what construction riggers used to call a “Double Sliding Hitch”.
I’ve always used - and highly recommend - the “Triple Sliding Hitch”, which requires adding a third turn.

See also the Prusik Knot described under Basic Roped Rescue Knots:
Transferring a Load from Belayer to Anchor via a Prusik Sling

and my favorite 'knot' site:
“Animated Knots by Grog”
Knot-Tying for Boating, Climbing, Fishing, Scouting, and Arborists

Animated Knots by Grog
Attached Images
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"

GordMay is offline   Reply With Quote
Old 16-11-2008, 03:01   #4
Registered User

Join Date: Nov 2006
Posts: 976
Images: 6
It is possible to get it wrong when in a hurry. I use it to climb trees for tree surgery. Whilst not critical it can lessen the drag, and increase the difficulty to "ease it" A wonderful knot BUT.....if it is slid through in a hurry it will heat up BIG TIME after all it is only friction. In climbing ropes it is important to move the location where the standing part is. It will melt the surface of the rope if you descend quickly. . In a boating sense I think that the same applies. Use it to work on the mast all the time (with a halyard) . If you are fit the double prussic makes for an easy ascender.
The easiest method is one to the foot and one to the waist(bum). Stand and slide, stand and slide.

cooper is offline   Reply With Quote
Old 16-11-2008, 07:52   #5
Writing Full-Time Since 2014
thinwater's Avatar

Join Date: Nov 2008
Location: Deale, MD
Boat: PDQ Altair, 32/34
Posts: 9,764
To Cooper: Sliding one rope over another under load is very dangerous

You are correct; regardless of the knot type, if the load is there and there is enough motion, one will melt. A few days ago I saw an illustration in a book suggestion that a good way to descend from the masthead is to wrap the lazy end of the rope around the webbing on the bosons chair in such a way as to cause friction, and lower away. I have seen a climber scraped up (he lived) because he lowered off a cliff with his rope sliding through a webbing sling.

Sliding under load is best rope-on-metal. A munter hitch around a separate biner would be very safe. There is rope-to-rope friction with a munter hitch, but the contact point keeps moving so heat does not build.

My real question was how will a prussic hold at a 60 degree angle, cycling and wet? I guess I will do some trials with undersize lines, to see.
thinwater is offline   Reply With Quote
Old 16-11-2008, 12:37   #6
Registered User
Dudeman's Avatar

Join Date: Jun 2007
Location: Gunnison, CO
Boat: Wharram Pahi 31, Oh Be Joyful,
Posts: 42
Red face

There are some interesting devices made to replace prusiks. For about $25 you could get a wild country ascender. It cams down on the rope but fits 10-11mm sized ropes. You could use the ascender and then back it up with a hard not for peace of mind. $25 would buy you a life times worth of prusik material.
Dudeman is offline   Reply With Quote
Old 16-11-2008, 14:00   #7
Writing Full-Time Since 2014
thinwater's Avatar

Join Date: Nov 2008
Location: Deale, MD
Boat: PDQ Altair, 32/34
Posts: 9,764
Hey, climber dude from Colorado; I have climbed in Eldorado and Boulder Canyon - very nice. I am from Virginia, but have been climbing rock and ice all over for 25+ years.

I know for a fact that most camming devices of that sort can slip if loaded other than 180 degrees, and jumars have been known to lever clean off a rope on a diagonal. There are also rope wear issues.

I use Jumars climbing the mast and would use the pictured device as a safety, no question, but I would not use them for this application, I don't think. Which is why I started the thread.
thinwater is offline   Reply With Quote
Old 16-11-2008, 15:04   #8
Registered User

Join Date: Jan 2005
Location: Seattle area (Bremerton)
Boat: C&C Landfall 39 center cockpit "Anahita"
Posts: 1,077
Images: 6
Back to the original question

I've used a prussic hitch to attach an anchoring snubber line to both nylon and chain rodes for decades now. It is possible to attach back-up sacrificial snubbers using a boat hook to run them out on an already stretched out rode.

My experience is that the hitch in this application does not slide once you "set" it on rode (snubber dia equal to or less than the rode dia) or chain. It can be attached one-handed in a swell when you need the other hand to hold on to the boat for safety. Practice doing it.

I've ridden out some very heavy swells and wind with the hitch attaching snubber lines and broken some sacrificial snubbers due to chafe on the boat but always had a back-up ready. Since that time I use Dacron at the boat end overboard past fairleads thence attached to nylon the rest of the way to the rode with no failures in heavy swells.
"I don't think there'll be a return journey Mr. Frodo". Samwise Gamgee
Rick is offline   Reply With Quote
Old 16-11-2008, 16:25   #9
Writing Full-Time Since 2014
thinwater's Avatar

Join Date: Nov 2008
Location: Deale, MD
Boat: PDQ Altair, 32/34
Posts: 9,764
No-stretch = less chafe

Thanks Rick, for the practical answer. I still wonder about the angle of a bridle.

Though stretchy material is best for anchor rode, non-stretch is best for bridles and the like. The reason is that stretch encourages chafe. Rock climbers learned years ago - I hope - that ONLY the rope should be stretchy, and that all anchors should be static, lest they cut through on a sharp edge. I always use old mainsheets and halyards for the sacrificial bits. Very low stretch, and I cover wear spots with tubular webbing.
thinwater is offline   Reply With Quote
Old 17-11-2008, 19:33   #10
Registered User
schoonerdog's Avatar

Join Date: May 2004
Location: annapolis
Boat: st francis 44 mk II catamaran
Posts: 1,216
Images: 4
we always use a variation with several more turns going away from the standing portion down the anchor line and a couple coming behind. Like the triple except with 5 turns forward and 2 turns aft. Stayed for a total of probably 10 months at anchor in different places and lots of wind and swell. Never a problem.
schoonerdog is offline   Reply With Quote


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Anchor Bridle S/V Mother Ocean Monohull Sailboats 3 31-10-2008 12:11
Looking to hitch a ride to north America rlt414 Crew Archives 0 21-05-2008 11:14
LA to Hawaii - Need a ride to hitch panjandrum Crew Archives 0 20-05-2008 00:05
Author looking to hitch a ride. Mikethe author Crew Archives 10 08-05-2008 13:24
hitch hikeing to freeport captjohn360 The Sailor's Confessional 0 29-01-2006 12:15

Advertise Here

All times are GMT -7. The time now is 11:47.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.