The perfect Passagemaker? II (building material)

the perfect material would be free , easy to use, indestructible and last forever everything else is less than perfect

 

****,

have forgotten to make a tick box for "wardds composite", would have been the winner.

 

Through life costs, for maintenance etc, lower than steel. If you did a cost over say 10~15years the ally is the clear winner despite the higher capital costs.

The overall weight of structure shall be approximately 50% less than a steel version. This equates to smaller engine size, which means cheaper engine and smaller and again, lower maintenance costs, al means carrying less fuel lower fuel consumption. Or keep the same ‘size’ engine (as on a steel) and run at a lower rating to improve longevity of the overhauls, or TBOs.

So long as the design pays attention to dissimilar metals and hence potential corrosion issues, the ally is maintenance free. It is very forgiving when deck hands don’t always wash down the decks properly etc.

It has very good notch toughness, hence running in cold or icy waters is not a problem.

Being lighter than steel…the equipment/machinery required to build is for light work…not heavy cranes etc. Frames can be lifted by several people, or small overhead light weight swl cranes.

Simple tools for working/fabrication….tools that one can buy in any decent DIY shop for example.

Outfitting the hulls/deckhouses, again simple tools can be used for attaching fastenings for outfitting panels etc…..even gluing is very simple and straight fwd.

These are just some of the benefits of using ally.

BUT, everyone has their own personal choice/preference too, for their own reasons not just technical. In some cases steel is the preferred choice, in others ally and again, in others, composite. But given the choice, mine is ally.

 

Thank you John for elaborating on that.

 

Additional for aluminum. Higher resale value, much faster welding, Painting the interior is not needed and costs are very nearly the same if the exterior is also unpainted. Unpainted aluminum is far more corrosion resistant than painted aluminum.

Notch resistance is a good point. Aluminum is a face center cubic crystal vs a body centered cubic crystal.

 

Would this still apply to a ship with steel hull and aluminium deck structures?

 

Yes, to some extend.

 

I noticed that the poll which I made open (the members votes are visible), is now in the hidden status.

Jeff, may I ask why?

Richard

 

You can see who voted on this public poll at http://www.boatdesign.net/forums/boat-design/poll-a-154.html - once you have voted yourself in the poll, click the vote numbers to see the details on a public poll (e.g. 15 9 3 2 3 as I type this and those are linked to who voted for public polls.) Sorry the link is not very intuitive - there haven't been too many public polls to date so this didn't come up until now.

 

It will apply to both. Pure aluminum boat has very low cg.

 

Thanks for that Jeff!

 

"More fire resistant than fiberglass" - I didn't get a picture before it sunk but I saw an aluminum one go up this summer. It was exactly like throwing a pop can into the fire. Large holes suddenly appeared in hottest spots then (aware that it doesn't support combustion), it dissappeared pretty much to the waterline in the engine space and lazarette, then sunk. I thus contend that aluminum is as susceptable to fire as GRP.
Here is an example of an older GRP specimen. Older means heavier laminate than new builds and there is a matrix of glass still supporting the whisp of wrinkled gel-coat you see.



I'm not saying you could recover from this but at least there is something there for rescuers to spot. (A gentle reminder to make certain your fire systems and training are up to snuff no matter what the material of choice)

 

Some people insulate the aluminum with foam, thats is a bad fire no no.
The Aluminum wont burn unless it is very hot, like from gasoline or polyfoam. It is safer that fiberglass and should last longer in fire. I test almost anything I put in my boat with a blow torch, if it continues to burn after I take fire away it does not go on boat. That includes paints, insulation headliners, cushions, carpeting etc...

Actually had two fires on my aluminum boat. One was due to spark, when I was welding, falling on a stray piece of foam and the other an alcohol fire in galley. Both were extinguished easily since there wasn't much to burn. On a fiberglass boat both would have been a disaster.

 

Well,

wood and wood epoxy does not easily burn either. And steel is very hard to ignite, isn´t it?

But it is rare that Alu burns. You need a real heatload to ignite it.

 

The real problems in shipboard fires with alloy is that it collapses at much lower temperatures. Apparently to get alloy to burn you need an oxygen rich environment. The tales of alloy burning on falkland warships after missile strike are apparently wrong, it just melted and collapsed.

That makes watertight bulkheads of alloy a choice on a steel ship and superstructure too, particularly for a 'lightship' voyaging trawler style. But steel fire bulkheads are more robust.

If you can afford to have the inside and decks of a steel hull flame sprayed with alloy or zinc it will last forever with a little care. Even zinc rich primers are now very good systems. A passagemaker/liveaboard will have a better maintenance and lower abuse than a workboat and steel will do just fine with a little care, no more.