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jbarros 12-18-2003 07:37 AM

aluminum boats?
 
ok kids, pro''s and cons?
Do they last?
Other than needing a grip of insilation what are the major things needed to do it right?
and how do they compare to others for one off construction?

Thanks :)

-- James

Stede 12-18-2003 09:35 AM

aluminum boats?
 
Jbarros,

The below information is from the website -Mahina.com concerning aluminum hulls.

"Aluminum boats are generally lighter and faster than steel boats, have less impact resistance and may be more difficult to have repaired in remote shipyards. Painted aluminum boats often tend to develop paint blisters after four to five years of serious cruising, requiring an expensive repainting job if you want a perfectly fair and shiny hull. There are dozens of unpainted French aluminum boats cruising the world, and although you may not find their concrete-colored oxidized aluminum hulls attractive, they are strong and practical. Aluminum suffers from electrolysis more severely than steel; if you''re cruising on an aluminum boat you''ll need to be very careful when moored in electrically "hot" marinas. Quality aluminum builders include Kanter in Ontario and Topper Hermanson in Florida."

*** BTW, I wanted to apologize to you for a previously undeserved remark I made to you here on this board.I think it was on the "pirate" topic. I acted childishly and am sorry for my behavior.Fair winds!

dpboatnut 12-18-2003 02:12 PM

aluminum boats?
 
The last two issues of Sail Magazine have featured articles by the incomparable Dave Gerr on metal boat construction. There''s probably just enough information in the articles for you to decide if you really want to delve deeper into the subject- there''s a lot to be learned about metal types, fabrication methods, material-specific design requirements, metals isolation, corrosion prevention, hardware attachment, and maintenance. All are deep and nuanced subjects, and likely alien to most folks'' workaday knowledge.

And as an aside, I''d recommend all of Gerr''s books (except perhaps the propeller book, unless it''s a particular passion of yours)- he has an easy writing style about complex and technical subjects, and draws on a varied background for examples to illustrate his points.

If a performance boat is still something you''re thinking about, I don''t think you''ll find aluminum a useful hull material below around 40 feet, and perhaps not even that small.

Best,
Chad

paulk 12-18-2003 02:24 PM

aluminum boats?
 
A 1976 aluminum boat in our harbor frequently wins its division in the Newport-Bermuda, Vineyard, and Block Island races. (Continuing the tradition this past season as well.) The owner obviously sails well, but the Aage Nielsen design is not at fault either. There has been no apparent problem with paint adherance. Electrolysis is generally something to stay aware of - and ahead of - on an aluminum boat. Any scratches or paint damage left exposed , especially below the waterline, can lead to catastrophic leaks. One-off costs can be higher than for some other materials because the welding is trickier than steel, for example, and the more skilled workers command higher wages. Material costs can also be higher for aluminum. You don''t want the same stuff they use for screen doors! Unless you''re stamping out mass volumes of rowboats or skifffs or are doing your own welding, aluminum boats seem to start getting cost-effecttive in the over 35'' range. (The one at the head of this post is 43'' long.) The trade-off benefit is lighter weight, which makes, as noted above, for a faster boat.

jbarros 12-18-2003 08:00 PM

aluminum boats?
 
Stede, thanks for the info. I dont remember anything especialy untowards in the conversation, but both it and the guns discussion got a little heated on every side. So likewise, I know I said things I shouldnt have, and if you were offended by them, I appologize.

boatnut: I was reading the Sail articles, thats what got me thinking. So I wanted to come on here and ask people who''ve actualy been on the water with them. Thanks for the book recomendations. I''ll get on those.

Paul. I''m going to start a set of welding classes including gass shielded, which, combined with the Sail article made me think about building one, so the labor cost would be only time I lost for most of the welding, in theory. We''ll see how the classes and my self confidence with the gear goes though.

Thanks :)

- James


DelmarRey 12-19-2003 09:38 AM

aluminum boats?
 
I''ve been working in the metals trade for more then 30 years and I thought I would rely a few problems of welded aluminum.
I have also been consider an alum. vessel for my next venture so I''ve been looking at all the alum. boats that come my way.

First you''ll need to know is that 5083 is marine grade alum. with a 4.5% magn. content. Sometimes 5056 is substatuted but the weldablity is less desired. When welding alum. the properties in the metal change creating a weak area around the weld, a softening of the metal. There are three ways to weld alum. Mig - a wire feed gas sheid electric weld. Tig -an AC electric arc gas sheild with alum rod added as needed. And electrtode welding rod flux coated. Tig is the strongest but very time consuming. Mig is acceptable and the most common. Electrode not even considered for boat construction.

Any high stress areas should be formed rather than welded. On the vessels I''ve inspected with cracks, the cracks were around stantions, in the corners of transoms, cabin to deck mountings and deck to bulwark mountings. All the cracks were just outside of the welds in high stress areas. Theses were all powerboats, I haven''t had the opportunity to check out a sail vessel yet. So I''m sure around deck fittings and rigging mounts would need a good inspection.

Alum boats are built like steel or wooden boats with frames and a keel beam which in the thinner hulls you''ll see a weld seam at each frame, a bulge in the surface.

As for painting, the surface will need an acid etching for the paint to stick. And below the waterline I would use an epoxy bottom kote.

The nice thing is if you want to fill a hole or do some patch work, it can just be welded up. On larger vessels one could carry their own welding machine.

Enough for now...................._/)

GordMay 12-19-2003 11:33 PM

aluminum boats?
 
Delmarrey:
You said “Any high stress areas should be formed rather than welded.”
Would this apply to ALL CORNERS (as far as practical)?
That is - bend or roll the corners, and weld the flats, as with fuel tanks?
Thanx and regards,
Gord

GordMay 12-21-2003 01:28 AM

aluminum boats?
 
Follow the url to some excellent information on Aluminum boatbuilding from ''ABS''.
http://www.eagle.org/rules/downloads/109HSNC-2003/Part%202%20-%20Al&FRP_e.pdf

Fishboat 12-21-2003 03:45 AM

aluminum boats?
 
The issues surrounding galvanic corrosion & hot marinas can be eliminated if you setup the shorepower wiring with an insolation transformer. Nigel Calder''s "Boatowner''s Mechanical & Electrical Manual" covers the topic well.

WHOOSH 12-22-2003 01:28 AM

aluminum boats?
 
Altho'' we now use an isolation transformer because of the need to use 220V-250V AC aboard our 120V boat, a cheaper alternative is a Galvanic Isolator. These are far less expensive as a method for protecting a boat from a ''hot dock'' (altho'' nothing will protect a boat from its own issues as e.g. when a compass wire chafes thru, generates a current on own ship''s wiring and the prop blades start to fall off). Newmar makes a good Galvanic Isolator; there are others but this one worked very well for us when we had a ''hot dock'' problem.

Jack


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