Hull material? Pros and Cons please.

Are icebreakers made out of anything other than steel?

A double hull wall sounds good. But does any yacht builder practice this? For serious impact events I would think that number of frames and bilge pumping capacity would be more practical considerations than hull material?

Can't wait to hear from Lars

rambling Kelly

So what are the yards that do the double hulls? That can't be a cheap option!

Wouldn't a steel hull be easier to repair than a composite or aluminium? If so it should be taken into consideration if you are going to sail to some remote location where qualified shipyards may be few and far between.

I might expect this on an expedition yacht. But how common are collision bulkheads and watertight doors on "regular" motoryachts? Of course you can design this into any custom yacht. I'm just wondering how often it's actually done?

Thanks Lars ,
Kelly

Thanks for the info Lars, very interesting topic

i am building a boat at 94 feet with a dutch yard. she is built in aluminium. the reason is, i wanted speed alongside good sea keeping ability. she will have 25+ knots top speed and 19 knots fast cruising speed with a semidisplacement hull. she has a round bilge hull, so should be quite capable in high seas as well. her range in slow cruising will be around 2500 miles. as lars indicated, she has her tanks integrated to the bilge and will be double bottom. although i do not intend to charter, she is being built to MCA standards and according to safety calculations she will have a collision bulk head with a sliding watertight door between the VIP and other cabins and there will be 2 more watertight bulk heads at the fore and aft of engine room. initially another bulk head was planned between the guest cabins and the master, but calculations at a later stage did not require this. i have made some investigations in terms of material strength for aluminium and steel. i understand that aluminium has better elasticity, meaning will keep its form better when you hit something; especially when you consider the weight factor. however, it is more expensive than steel. on the other hand aluminium is easier to work with during production, but need more technical expertise for welding. steel has better tensile strength, meaning it will withstand more loads before it is torn. so there is always a compromise, but if you want to go fast, even with a semidisplacement boat, you need to save on the weight, thus steel is not a good alternative.

well, i should state that corrosion was not a crucial point in my decision base. however, i have tried to study best possible pros and cons of aluminium in respect to steel. aluminium bonds very easily with other metals, so both during the production and during the life span of the boat one should be careful abt properly taking necessary measures to avoid bonding. i also found out that there are systems which detact electrolisys activity of the hull, so one can take precautions at an earlier stage if your anodes are not functioning properly or there is a contact with other metals. in terms of corrosion it is much more difficult to maintain steel, because oxidation is very effective with steel and painting and maintanance of steel is much more important. you do not need to paint the upper sides of an aluminium boat for reasons other than esthetics.

I know this is purely a cosmetic consideration. But I wonder which usually requires more filler material to achieve a "yacht finish", aluminum or steel?

Kelly

Yachts do not have to be built to MCA, or any other classification society reguardless of size if they are going to be private only.
If a yacht is going to charter or be commercial use then she should be classed.
Delta is most likely the best US yard right now, yet many of their boats are not built to class, Westport does not build to class (although the new 164 will be classed).
Building to class will insure a high standard of engineer and safety including watertight bulkheads and automatic doors on larger yachts. Current class status also helps resale value when you decide to move to another yacht.
Good luck with your build
Dave

I've been doing a little bit of reading about different hull materials lately, and have come across some interesting info.

The first is from a company called Trekker Yachts, they build small explorer style yachts out of aluminium and don't paint them at all.....

http://www.trekkeryachts.com/frtrekconst.html

The next two links are to the site of a marine designer who appears to have put a lot of thought into hull material.

http://www.kastenmarine.com/alumVSsteel.htm

http://www.kastenmarine.com/metalboats.htm

Has anyone heard of "Monel"?


Thanks for the SPS link Codger, very interesting.

The more I read about the Sandwitch Plate System (SPS) system, the more impressed I become.

This report from the Lloyd's website has some interesting aditional info.
The report starts about halfway down (pg 5), and is a pdf, about 380kb.

http://www.lr.org/news/downloads/marine_bulletin_00-3.pdf