Anyone have experience (or engineering advice) on fabricating helix / screw anchors? - 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 > On Board > Gear & Maintenance
 Not a Member? 
  #1  
Old 05-10-2011
Senior Member
 
Join Date: Jan 2007
Posts: 387
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 8
Northeaster is on a distinguished road
Anyone have experience (or engineering advice) on fabricating helix / screw anchors?

Hi folks,

I am considering using a couple / few Helix / Screw style anchors to hold my floating dock in place.

For a couple of reasons ( need to do this in next couple of weeks, no local availability of Pre-made, and cost) I am condiering welding up my own out of some heavy duty galvanized pipe, and flat stock cut / welded to form the conical screws.

I would have to grind off the galvanized coating where I weld, but, as this part would be buried several feet in the deep sand and mud, I would think it would be good for several years.

I think I would walk up to about my waist, at low tide, and have a friend help me turn them into the bottom, prehaps using a 10' piece of pipe / rod , horizontally, to turn it in. I could have this go through a slot or hoop at the top of the anchor, to drive it in.

Any thoughts would be appreciated.
Reply With Quote Share with Facebook
  #2  
Old 05-10-2011
svHyLyte's Avatar
Old as Dirt!
 
Join Date: Nov 2008
Location: Tampa Bay Area
Posts: 2,546
Thanks: 11
Thanked 84 Times in 80 Posts
Rep Power: 6
svHyLyte is on a distinguished road
Absent knowing anything about your bottom conditions, any advise you might recieve on this subject hereinabouts is pure speculation. You might be screwiong into nothing more than Jello or screwing into dense sandy clay or better. It does make a difference.

FWIW...
__________________
"It is not so much for its beauty that the sea makes a claim upon men's hearts, as for that subtle something, that quality of air, that emanation from the waves, that so wonderfully renews a weary spirit."
Reply With Quote Share with Facebook
  #3  
Old 05-10-2011
Senior Member
 
Join Date: Dec 2003
Posts: 1,343
Thanks: 1
Thanked 14 Times in 13 Posts
Rep Power: 11
capttb is on a distinguished road
Could you maybe use something like these dock augers?
Overton's® > Stationary Dock Hardware - Leg Pipe Sand Auger - Mooring & Dock > Docks & Hardware > Stationary Docks & Hardware :
__________________
"Just call me TB"
Reply With Quote Share with Facebook
  #4  
Old 05-10-2011
Senior Member
 
Join Date: Jan 2007
Posts: 387
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 8
Northeaster is on a distinguished road
tidal river, sand/rocky bottom, I believe. Will have to check further,

I think I need something more robust than the dock auger in the link.

Thanks.
Reply With Quote Share with Facebook
  #5  
Old 05-11-2011
mcavacas's Avatar
Junior Member
 
Join Date: Feb 2011
Location: Boston
Posts: 9
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
mcavacas is on a distinguished road
Based on how this member did it, sounds like you're in pretty good shape.

From an engineering standpoint, there are a few things to consider. The anchor will hold better with a larger diameter pipe, but it will be much harder to install. The distance between threads you use will also affect this-a smaller distance between threads will make it harder to install, but it will hold better. Also, the more threads you use the harder to install, but the more holding power.

It also might be advantageous to create a triangle at the beginning of your flat stock to make a gradual thread, as in your typical drywall screw.

Hope this helps, let us know how it goes!
Reply With Quote Share with Facebook
  #6  
Old 05-12-2011
Senior Member
 
Join Date: Jan 2007
Posts: 387
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 8
Northeaster is on a distinguished road
Thanks for the engineering advice. I did read that member's posts, and that was the catalyst for getting me thinking in this direction.

I would think that a tapered start would make the entry easier as well, without sacrifing much holding power.

I will try to drive a stake or rod a few feet into the ground at low tide this weekend, to see how much sand/rock there might be above what could be larger rock or bolders.
Reply With Quote Share with Facebook
  #7  
Old 05-12-2011
deniseO30's Avatar
Move over Joan Rivers!
 
Join Date: Nov 2006
Location: Bristol pa
Posts: 5,856
Thanks: 51
Thanked 72 Times in 64 Posts
Rep Power: 9
deniseO30 will become famous soon enough deniseO30 will become famous soon enough
sounds like the perfect application for old, unused, or discarded post hole drill bits.... Jus sayin..
__________________
Denise, Bristol PA, Oday 30. On Tidal Delaware River, Anchor Yacht Club. New Website!
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

my current "project"!
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Share with Facebook
  #8  
Old 05-12-2011
PCP's Avatar
PCP PCP is offline
Senior Member
 
Join Date: Dec 2004
Location: Portugal, West Coast
Posts: 16,160
Thanks: 21
Thanked 95 Times in 79 Posts
Rep Power: 10
PCP will become famous soon enough
The same guys that make the Spade (Sea tech) make a helicoidal anchor, the screw anchor. Probably they are available in the US through the Spade distributor.

Anyway you have here lot's of information. The best is in French but you have also lot's of images.

Catalogue - Ancre ŕ vis SKREW pour vos mouillages forains - Sea Tech and Fun - Spade - (Version JPG)

Sail-World.com : The Skrew Anchor

Boat anchor - SPADE - Sea Tech and Fun - Spade

New generation of permanent anchors Skrew at the METS, Sea Tech & Fun Europe sarl

Home page - Ancre Spade Sword Skrew - Ancres haute performance -
Reply With Quote Share with Facebook
  #9  
Old 05-14-2011
Senior Member
 
Join Date: Mar 2008
Posts: 885
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 7
GaryHLucas is on a distinguished road
A B Chance, every power company lineman knows them.

Gary H. Lucas
Reply With Quote Share with Facebook
  #10  
Old 05-25-2011
Senior Member
 
Join Date: Jan 2007
Posts: 387
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 8
Northeaster is on a distinguished road
Thanks Gary. The AB Chance website had lots of info, drawings, etc.
Looks like their ground / earth screw anchors, which come in a couple of different models / sizes, are re-branded as the Helix anchor (for Marine use), at least that is where the website link takes you, after clicking on mooring anchors.
Anyway, after looking at their design, I welded up a similar anchor to their round stock screw anchor, using a 15" disk.

It took a couple of attempts, standing in a couple of feet of very cold water, at low tide, but I did get it to go over halfway in, before running out of steam. I should be able to finish turning it in this weekend. The ground / bottom there varies between rocky to somewhat sandy, near shore.
The one I built was about 6 ft high, and I feel it will have lots of holding power, if I can get it to go all the way in. I used a 6ft bar to turn it in.

When I find out where the local power companies buy their similar anchors, I may buy one of two, if the price is reasonable, and add a couple more for security.
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
advice from people with experience towing 30' boat Northeaster Gear & Maintenance 31 04-06-2011 11:19 AM
ned help fabricating a new fiberglass sliding hatch for a hunter 25.5 charliebelting Gear & Maintenance 11 11-10-2010 09:20 PM
Helix Mooring Anchors... one or two? Joel73 Gear & Maintenance 21 05-19-2009 03:45 PM
fabricating a spinnaker pole.. groundhog Gear & Maintenance 21 03-12-2009 11:40 AM
Advice for gaining experience in Northern NJ piratemike Learning to Sail 6 09-13-2008 04:22 PM


All times are GMT -4. The time now is 03:58 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