Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 02-04-2016, 03:19   #16
Registered User
 
Snowpetrel's Avatar

Join Date: Jul 2012
Location: Hobart
Boat: Alloy Peterson 40
Posts: 3,071
Re: So, what can go wrong with aluminum?

^^@stumble.
Ha, you got me there Greg, but Its interesting that titanium also has a fatigue limit like steel, I hadnt seen that before. An amazing material!

But I do think fatgue might become a bit more of a problem as the modern boats get older particularly when combined with more lightly built high performance hulls. I guess most of them will give plenty of warning just start to go soft, but cheeky rafiki, Polina star and the rudder failures show what could go wrong.

It used to be a big problem on the ships. Not so much with the hull plates (though we did split one once) but all the internal tanks and deck structure often started to crack up as they aged. The old Breman built ships survived into the 20 year old mark before it was a big issue, but the newer lighter built ships where cracking tanks at 10 years.

Ive even seen a steel yacht with fatigue cracks around the keel, and heard of a few skegs in steel boats being lost like that. And I've actually go a few small deck cracks on my boat that need to be welded up and reinforced due to using 3mm plate and not enough frames to support a heavy crew bouncing up halyards and jumping into the cockpit.
__________________

__________________
My Ramblings
Snowpetrel is offline   Reply With Quote
Old 02-04-2016, 06:50   #17
Moderator
 
a64pilot's Avatar

Cruisers Forum Supporter

Join Date: Oct 2013
Location: Albany Ga.
Boat: Island Packet 38
Posts: 17,034
Re: So, what can go wrong with aluminum?

I believe the first Soviet Alpha was retired almost immediately due to fatigue cracking, at the welds.
Rumor mill had it that an Alpha was dove to beyond 1300 meters I think and many of the interior fittings were broken, but hull was OK.
I think Ti is normally welded with submerged arc? But the Soviets licked the Ti welding issue in the 60's cause I think that sub was made from welded sheets.

I know there was a special CIA program for years to buy Titanium whenever and wherever they could get it for uses like the SR-71.
I thought that was because the only source was the Soviet Union. I know after the collapse of the Soviet Union the price for Ti collapsed, I don't know if it is still low.


Sent from my iPad Pro using Cruisers Sailing Forum
__________________

__________________
a64pilot is offline   Reply With Quote
Old 02-04-2016, 07:44   #18
Marine Service Provider
 
bdbcat's Avatar

Join Date: Mar 2008
Posts: 4,879
Re: So, what can go wrong with aluminum?

Folks...
I've owned and cruised a large aluminum power-cat for 16 years.

FAQs About the Boat

Two points to make:

1. The number one corrosion issue is caused by small particles of of stainless/steel/copper accidentally dropped into a wet bilge. Especially copper, as from shards of stripped wire which inevitably result from electrical projects.
The corrosion is known as "exfolitiate corrosion", and occurs mainly in rolled Al plates. It is as though the foreign metal is "melting" into the Al plate, creating a coin-sized patch that eventually flakes off. The result is locally reduced plating thickness.
So, one must be scrupulous about clean, and preferably dry, bilges.

2. Antifouling: This problem is essentially licked by using an epoxy barrier coat to electrically isolate the hull. Normal high-copper antifouling may then be used over the top. I have seen much more internal corrosion than anything attributable to galvanic action with copper paint.

Cheers
Dave
__________________
bdbcat is online now   Reply With Quote
Old 02-04-2016, 10:38   #19
Marine Service Provider
 
pbmaise's Avatar

Join Date: Jan 2007
Location: Pahoa Hawaii
Boat: Jay Kantola - Trimaran 65 ft by 40 ft beam
Posts: 579
Re: So, what can go wrong with aluminum?

Epoxy is the best way.

Easy to repair.

Minor repairs underwater.

Core thickness adds insulation and strength.

It is far better than GRP using cheaper resin.

No bottom paint required if you clean bottom regularly.

I have a huge trimaran and the epoxy hulls were last bottom painted 6 years ago.

I clean the bottom once a week in seawater. Twice a week if brackish water. It takes me just 2.5 hours.
__________________
pbmaise is offline   Reply With Quote
Old 02-04-2016, 11:00   #20
Senior Cruiser
 
Cheechako's Avatar

Cruisers Forum Supporter

Join Date: Aug 2006
Location: Skagit City, WA
Posts: 19,342
Re: So, what can go wrong with aluminum?

a) aluminum can corrode very rapidly in certain situations. or not!
b) Welds can crack, and often do. So can just the parent metal in higher stress spots.
c) paint can be a real problem, doesn't last long. My friends 48 ft cutter was painted 3 times in about 10 years.




Titanium is actually one of the most prevalent ores there is. The problem is it's not easy to make into metal, and few suppliers do it.
Ti welding requires the weld area to be shielded with inert gas on BOTH sides of the weld.... otherwise the metal goes bad. Timet used to be the big US supplier of Ti products. Not sure anymore. I have toured their plant.
__________________
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard











Cheechako is offline   Reply With Quote
Old 02-04-2016, 11:13   #21
Wayfaring Mariner
 
captain58sailin's Avatar

Cruisers Forum Supporter

Join Date: Mar 2009
Location: Homer, AK is my home port
Boat: Skookum 53'
Posts: 4,045
Images: 5
Re: So, what can go wrong with aluminum?

With aluminum, you have to be very careful about the galvanic corrosion and it has a limit to the number of times it can be bent back and forth, as stated previously. Having said that, I had an aluminum commercial fishing boat that was built in 1962, and there were some spots that corroded through that had to be welded, no big deal, I also developed some stress cracks under the stringers where the engine was mounted, again take a skill saw and cut it out and weld back stronger pieces. If you can do your own welding it isn't too much trouble to keep up. I would have to vote with epoxy encapsulated wood for long term, ease of maintenance and longevity. I also like old FRP boats.
__________________
" Wisdom; is your reward for surviving your mistakes"
captain58sailin is offline   Reply With Quote
Old 02-04-2016, 11:17   #22
Marine Service Provider

Join Date: May 2012
Location: New Orleans
Boat: We have a problem... A serious addiction issue.
Posts: 3,940
Re: So, what can go wrong with aluminum?

Snow,

The marine industry needs to design boats to fail after some period of time. Boats really are lasting too long. Think about it, the first fiberglass boats built are still out floating around now 50 and 60 years after being built. It cripples the ability of the industry to innovate, restricts new income, and prevents new designs from coming to the fore.

Think of it this way, how healthy would the car industry be if 90% of the cars ever built were still on the road in reasonable condition. Ya sure there would be a lot more really beautiful classics but there would also be hundreds of thousands of yugo's clunking along, with poor safety records and spitting oil everywhere.

It really is a vicious circle... Thin margins in the marine industry means no advertising to the general public, which means a smaller boating population, which means even thinner margins. Small boat manufacturers used to advertise in mainstream publications, now I can't remember when I saw a boat add anywhere but on a sailing website.
__________________
Greg

- If animals weren't meant to be eaten then they wouldn't be made of food.
Stumble is offline   Reply With Quote
Old 02-04-2016, 11:32   #23
Registered User

Join Date: Sep 2015
Location: Essex, England
Boat: Hartley Tahitian 48
Posts: 284
Re: So, what can go wrong with aluminum?

Ferro cement is the way to go. Mine get stronger every day.

__________________
paulajayne is offline   Reply With Quote
Old 02-04-2016, 11:40   #24
Marine Service Provider

Join Date: May 2012
Location: New Orleans
Boat: We have a problem... A serious addiction issue.
Posts: 3,940
Re: So, what can go wrong with aluminum?

Quote:
Originally Posted by a64pilot View Post
I believe the first Soviet Alpha was retired almost immediately due to fatigue cracking, at the welds.
Rumor mill had it that an Alpha was dove to beyond 1300 meters I think and many of the interior fittings were broken, but hull was OK.
I think Ti is normally welded with submerged arc? But the Soviets licked the Ti welding issue in the 60's cause I think that sub was made from welded sheets.

I know there was a special CIA program for years to buy Titanium whenever and wherever they could get it for uses like the SR-71.
I thought that was because the only source was the Soviet Union. I know after the collapse of the Soviet Union the price for Ti collapsed, I don't know if it is still low.


Sent from my iPad Pro using Cruisers Sailing Forum
Not wrong... Just a little missing.

The Alpha subs failed initial testing because of oxygen embrittlement in the welds. Which is a major problem for large constructions like hulls. It is still the primary reason titanium hulls aren't common. But there is hope, a new process called friction stir welding is at the commercial testing phase, and shows serious promise at reliable deep penetration welding of titanium plate.

Currently ti is generally welded in full argon environment, with gas shielding front and back for large welds. For smaller parts the prefered method is to drop the part into an argon box and weld it there. Think of it like a sand blasting box but a 100% argon environment.

So far no one has really licked the problem. Ti is just to suceptable to oxygen at high temperatures to be a 'solved' problem. Better to say it is a managed one. Almost all the ti parts rejected from ti production fail because of poor weld quality.


Because of its value in the defense industry for decades Ti was on the list of strategically important materials in the US. So the Feds and their subcontractors could only use Ti from US sources. Which led to a small number of US companies holding an effective monopoly on TI supplies in the US. because if you can't sell to the aero space and defense world you couldn't make a profit. Luckily this changed about 10-15 years ago which is why Ti prices have fallen off a cliff since then. With volumetric prices of Ti now running about 1.6 times the price of stainless, where before it was closer to 15 times.

It's this 90% reduction in feed stock that is making it reasonable to introduce to the marine market. Add in some decent engineering and the cost of the materials in a titanium part may actually be less than the cost of stainless in the part.
__________________
Greg

- If animals weren't meant to be eaten then they wouldn't be made of food.
Stumble is offline   Reply With Quote
Old 02-04-2016, 12:52   #25
Moderator
 
sailorchic34's Avatar

Cruisers Forum Supporter

Join Date: Feb 2011
Location: SF Bay Area
Boat: Islander 34
Posts: 4,812
Re: So, what can go wrong with aluminum?

The answer to what can go wrong with aluminum?

Here's a link for ya. Builder Blames Navy as Brand-New Warship Disintegrates | WIRED

Gee galvanic corrosion, who knew......

__________________
sailorchic34 is offline   Reply With Quote
Old 02-04-2016, 13:47   #26
Registered User
 
Panope's Avatar

Join Date: Sep 2012
Location: Washington State
Boat: Colvin, Saugeen Witch (Aluminum), 34'
Posts: 1,593
Re: So, what can go wrong with aluminum?

Panope's integrated water tanks (hull skin forms part of tank) have had water in them continuously for about 40 years. A few tiny corrosion pits about 1/16" deep have formed. Someday, I will coat the inside of the tanks with a food grade epoxy paint.

The 'tailgate' welder dude that my father hired to build the original engine beds did not use the hull framing for support. Instead, he welded the small engine mount pads directly to the (3/16") hull skin. This lasted about 10 years and several thousand engine hours before a fatigue crack formed in the skin that did produce a small leak (I have since re-built with beds that span 3 hull frames).

A small area of the bilge located directly under the (dripping) stuffing box has had water (sometimes fresh water) in it continuously for 40 years. Some shallow pitting has occurred here but the metal in this area (bottom of keel) is very thick. At the current rate, this will need repair in about 100 years. Every week or two, I use a wet/dry vacuum and suck out any foreign material (copper wire, pennies, etc.) that might have found its way to this area. The other 25 feet of keel/bilge is filled with cement (and lead) so no worries there.

That's what I got so far. Ask me again in another 40 years.

Steve
Panope is online now   Reply With Quote
Old 02-04-2016, 13:58   #27
Moderator
 
a64pilot's Avatar

Cruisers Forum Supporter

Join Date: Oct 2013
Location: Albany Ga.
Boat: Island Packet 38
Posts: 17,034
Re: So, what can go wrong with aluminum?

https://www.cia.gov/library/center-f...r-mystery.html
http://www.smithsonianmag.com/smiths...aft-180953402/

Ought to be reliable sources?


Sent from my iPad Pro using Cruisers Sailing Forum
__________________
a64pilot is offline   Reply With Quote
Old 02-04-2016, 14:56   #28
Marine Service Provider
 
boatpoker's Avatar

Join Date: Nov 2008
Location: Toronto, Ontario or Bahamas
Boat: Benford 38 Fantail Cruiser
Posts: 2,593
Re: So, what can go wrong with aluminum?

The biggest threat to an aluminum vessel is an electrician who uses the term "electrolysis".
__________________
That hysterical laughter you hear as you sail a way in your "new" boat ..... is the seller.
boatpoker is offline   Reply With Quote
Old 02-04-2016, 15:15   #29
Senior Cruiser
 
Jim Cate's Avatar

Cruisers Forum Supporter

Join Date: May 2008
Location: cruising SW Pacific
Boat: Jon Sayer 1-off 46 ft fract rig sloop strip plank in W Red Cedar
Posts: 11,447
Re: So, what can go wrong with aluminum?

Quote:
The other 25 feet of keel/bilge is filled with cement (and lead) so no worries there.
Steve, how is the lead isolated from the hull? Friends with French alloy boats have had serious issues with such interfaces and corrosion... their internal lead ballast was "potted" in coal tar epoxy mastic and it failed.

Jim
__________________
Jim and Ann s/v Insatiable II , lying Port Cygnet, Tasmania once again
Jim Cate is offline   Reply With Quote
Old 02-04-2016, 15:24   #30
Registered User
 
thomm225's Avatar

Join Date: Aug 2011
Location: Hampton Roads
Boat: 1974 Bristol 27
Posts: 3,451
Re: So, what can go wrong with aluminum?

This guy seems to have gotten quite a bit out of an aluminum homebuilt sailboat.

He builds the thing then sails it through some of the roughest waters on the planet. Nice to see he has tiller steering:

__________________

__________________
thomm225 is offline   Reply With Quote
Reply

Tags
aluminum

Thread Tools
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
wrong time wrong place? uldinch Marinas 15 04-12-2015 18:11
I Can't Sail, What Am I Doing Wrong? scoobert General Sailing Forum 38 03-06-2013 23:09
LINK 2000 - CAN "LOWBAT" MESSAGE BE WRONG? Savanna Electrical: Batteries, Generators & Solar 34 01-02-2013 13:37
Can I Coat a Leaking Aluminum Water Tank with Epoxy ? nknowland Plumbing Systems and Fixtures 8 22-05-2012 16:04



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 09:16.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.