How Are Aluminum Hulls ?

[Factor]

Originally Posted by Lodesman

Sorry - didn't mean for you to get yer knickers in a twist. It was merely an assumption on my part - Kerr's site disappeared about the same time Silkline came into being, and I'm fairly confident his boat "Lizard of Oz" is in charter with the Silkline prototypes: Faraway Expeditions - Phuket sailing and diving charters, Thailand Honest mistake - really. Anyway, if you do talk to hime, I'd really like to know if he's still selling plans?

Kevin

No offence taken - and sorry if my response came over all iffy. Peter is definately selling plans etc he can be contacted on 0428 857 336 or +61 428 857 336. pete@lizardyachts.com.au and the web site is in creation, his old host system fell over.

[Lodesman]

Thanks for the info. Cheers.

[bonobo]

My small input,

Meta and pro-Meta in France ( the builders of Montoissier "Josua" and many mythical ships from the 70's) makes aluminum boats and cats for over 30 years and they ALL still sail !
French singer "Antoine" is sailing around the globe for the past 30 years on his 40 feet "Banana split" Strongall cat with no complains.
Sister-ship 43 feet " Mogli" has been sailing for the past 3 years in the amazon, Pacific and is preparing for the Antarctic next season and Alaska afterwards...
Number 3, my own 43,5 feet " bonobo" will be launched next month and is equipped for extreme climate (Alaskan and Patagonian winter, tropical heat, Amazon) with central heating, extra isolation, double glass widows, dive compressor, water-maker, generator, 8 solar-pannels, two 55 HP diesel-engines, full satellite communication....

Thens of other versions of such cats have been produced, up to 65 feet for diving, aquaculture, fish farms, etc.... They are "working boats"

One do not buy a Aluminum cat for no reason, if the plan is to sail the warm calm waters of the Caribbean and the bahamas, it would be stupid to spend the money on such an expensive project; These vessels are slow and heavy, the are sea land-rovers, or Humvee's....
These are "off-road" cats that can beach on rocks, bump into something with no or moderated damage. The are the one in a lifetime investment for very special sailing destinations.
"plastic or tupperware" boats are not made for the North-west passage, Patagonia or the cap horn... Steel and aluminium ones are.
And the few disadvantages are minimal to the advantages, "if", again one need such a type of boat for the chosen program...

There are special anti fooling paints for them, they are equipped with "electrical leak" detectors.

Marc

[David M]

Not really mentioned is that aluminum is excellent for custom designs. Obviously aluminum construction does not require a mold and molds are very expensive to build. You have to build a number of boats from a mold to break even on a mold. This I believe is why many custom boats are aluminum hulls.

I have been operating an aluminum work boat for many years. The electrolysis is not a problem is you do the proper things to stop electrolysis. The last time I had any electrolysis was well over ten years ago. Its not a concern because I know how to prevent electrolysis. There is a whole list of do's and don'ts for preventing electrolysis. Its not hard to learn nor expensive to follow.

Painting an aluminum hull does have its problems. Ultimately the aluminum will cause the paint to blister. This means touching up the paint once a year in the areas that are blistering.

As far as making modifications, no material is easier to make modifications to. You probably though want to leave the aluminum welding to someone who does it professionally and frequently.

As far as noise goes, an aluminum boat is just as quiet as any other boat provided you spray the inside with foam and you add interior panels just like you would have on a fiberglass boat. The added benefit to spraying with foam is it prevents condensation.

Non-copper based anti-fouling paint is still pretty much crap. You will need to have the hull painted once per year to keep its anti-fouling properties. I have two coats applied from the waterline down to the end of the light zone....it helps some.

Aluminum boats are livelier. The hull has a higher resonance frequency than comparable fiberglass boats. This could be a good or bad thing or something you don't notice. Most people don't notice.

Most smaller commercial boats are being built with aluminum now. Much of the guess work of a few decades ago is gone. Its a real science now. That should be a pretty good indication of aluminums suitability for smaller boats, pleasure boats included.

I would never purchase a real old aluminum boat nor one built by an amateur because of the knowledge we have now of aluminum boat construction and the fact that it really takes a professional builder who has built many aluminum boats to get it right.

[Steve Strand]

Tim Mumby (another Aussie) has build a number of 46-48 foot cats which are light displacement, fast and appear seaworthy (He just circumnavigated on one of his). After sailing one of his, we are having one built in The Philippines by Harwoods of Australia. They are just finishing up two others. We like the idea of aluminum as is should be less susceptible to damage if we find a reef by mistake.

[beau]

I used to manufacture fiberglass boats (trimarans) but my latest boat
S/V Beaujest is aluminium and I love the material.

However a couple of points should be noted.

The panels have to be 4mm thick or more or they will warp badly when welding. The bottom of my boat is 6 mm
Therefore any boat under 12 meter 40 ft is not really viable.
A professional welder must be used, they know the material and you will get better resale value.
Insulation is a must.
Cost wise, they are much cheaper.
After the design was completed (custom) the plans were given to the aluminium supplier.
All the panels arrived pre cut (cmc) and numbered ready to assemble.
I agreed on an hourly rate with an Aluminium boat builder and the aluminium shell was completed in 5 weeks by two guys.(Pro's)
Painting is not difficult if you follow the manufacturers instructions.
I have had no problems with my 2 pack finish now 2 years old.

Electrolysis is easily controlled and repairs are very easy.
All the advantages of a steel boat with less weight and better resale value.
Highly suitable for multihulls.
I hope this helps.
I agree with all Cat Man Do's comments

[motion30]

In reguards to the loss of strength after welding I depends on the alloy Heat treated alloy looses 50% of its strength Strain hardened alloy loses only 10% of its strength due to welding but ofcourse it more costly