Concrete keels - any facts? - 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 > Boat Review and Purchase Forum > Sailboat Design and Construction
 Not a Member? 


Reply
 
LinkBack Thread Tools
  #1  
Old 03-19-2010
Low Salt Diet Sufferer
 
Join Date: Feb 2010
Location: San Francisco Bay Area
Posts: 64
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 5
kulokoo is on a distinguished road
Concrete keels - any facts?

Granted concrete is not the material I would use for ballast if I had the choice, but looking at old boats I see a Rawson 30 that would otherwise seem to fit my purposes (seaworthiness, cruising, liveaboard), taste and budget.

So what problems might one expect out of a concrete ballast keel that is 40 years old?

Things I've heard...

They cause corrosion
They soak up water
They disintegrate

Are these real problems or myths?

Also, are there fixes if problems come up, and if so how hard are the fixe$?

I am imagining if something goes wrong with a concrete keel it is harder to remedy than an external lead keel...


Thanks in advance for setting me on course!
Reply With Quote Share with Facebook
  #2  
Old 03-19-2010
sailingdog's Avatar
Telstar 28
 
Join Date: Mar 2006
Location: New England
Posts: 43,291
Thanks: 0
Thanked 10 Times in 10 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
If there are any leaks, there will be freeze/thaw cycle damage if the boat is someplace it gets below freezing for any period of time.

Concrete is a horrible ballast material for a couple of reasons, aside from the ones you've mentioned.

Concrete is not a very dense material. This means that it requires more space to provide the same amount of righting moment as lead or even iron. This means the boat has less interior volume and a lower righting moment, as the CG of the ballast is effectively higher. The boat will probably also have much more wetted surface area than it would if the boat had been made using lead as a ballast material. This means that a concrete ballasted boat will be slower and more tender than a similar design using lead or iron as a ballast material.

Second, it is difficult to properly repair once damage does occur. Lead is far easier to repair should you have problems.

Before committing yourself to this Rawson, I'd would recommend you read the Boat Inspection Trip Tips thread I started, as it will help you determine whether this boat is even worth going forward on.
__________________
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
  #3  
Old 03-19-2010
Jeff_H's Avatar
Moderator
 
Join Date: Feb 2000
Location: Annapolis, Md
Posts: 6,579
Thanks: 5
Thanked 95 Times in 71 Posts
Rep Power: 10
Jeff_H has a spectacular aura about Jeff_H has a spectacular aura about Jeff_H has a spectacular aura about
Sailingdog hit many of the functional issues with concrete ballast. I personally helped a fellow who owned a Buccaneer with concrete ballast that had gotten wet and frozen many times over the years. The concrete had been reduced to loose rocks that you could easily remove with your fingers surrounded by water saturated dust.

Of course the technique for constructing concrete ballast varies widely from simply dumping cement into the keel encapsulation envelope as was done on the Buccaneer, to casting a mix of boiler punchings and concrete in a separate mold and setting it like you would a cast lead keel as Bristold did on the Bristol 24 (AKA Corsair)

The other issue with this technique is never knowing what density the keel will end up being. The production manager at Bristol mentioned Corsairs where they accidentally left out the boiler punchings, and my family looked at a Cheoy Lee Frisco Flyer that turned out to have the a similar problem.

Jeff
__________________

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Curmudgeon at Large- and rhinestone in the rough, sailing my Farr 11.6 on the Chesapeake Bay and part-time purveyor of marine supplies
Reply With Quote Share with Facebook
  #4  
Old 03-22-2010
Low Salt Diet Sufferer
 
Join Date: Feb 2010
Location: San Francisco Bay Area
Posts: 64
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 5
kulokoo is on a distinguished road
Thanks, this makes me just about rule out a Rawson as I am more interested in sailing a boat than trying to re-engineer one with a problem.

Curious about the Buccaneer with the concrete ballast gone bad: were you and the owner able to fix it? Dig out the concrete and fill it with lead or something? Seems there is an interesting story there
Reply With Quote Share with Facebook
  #5  
Old 03-22-2010
sailingdog's Avatar
Telstar 28
 
Join Date: Mar 2006
Location: New England
Posts: 43,291
Thanks: 0
Thanked 10 Times in 10 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
On one boat I helped repair, we took the concrete out and filled the space with a mixture of epoxy and lead weights gotten from a tire shop. We then glassed over the top of the whole mess. It took up less space than the equivalent weight of concrete/iron and made for a deeper bilge.
__________________
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
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
Fixed or swing keel, which is better? TimG2 General Discussion (sailing related) 17 07-30-2014 09:23 AM
Fin Keel or Shoal Keel acmecoyote General Discussion (sailing related) 11 05-06-2011 04:39 PM
My First Boat...Boat Term Question... Kacper General Discussion (sailing related) 38 09-23-2008 06:52 PM
Wing, fin, or bulb...what are the trade offs? langousta Gear & Maintenance 17 09-17-2008 04:54 PM
Cruising Catamarans—Fixed Keels or Daggerboards? Kevin Jeffrey Buying a Boat Articles 0 01-06-2004 07:00 PM


All times are GMT -4. The time now is 12:11 PM.

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

The SailNet.com store is owned and operated by a company independent of the SailNet.com forum. You are now leaving the SailNet forum. Click OK to continue or Cancel to return to the SailNet forum.