Hull material? Pros and Cons please.

impact resistance

If impact resistance with floating objects were the only criterium, I would choose for steel. It will be thicker than aluminium and of all the materials mentioned it's the most ductile. This means it's more possible to deform before it breaks. Composite will more easily crack when hit at the same speed.
On the other hand, there are so many other (in my view more important) considerations like weight, maintenance, corrosion, cost, etc. that favour aluminium or composite.

Your impact resistance should be in a decent watertight subdivision (bulkheads and double bottom). I would not count on just the ductility of steel if you hit a container at 20 knots. It will be a shipyard job anyway, and if you don´t have the watertight subdivision, it´ll most likely be a liferaft ride.


PS I am not familiar with the new SPS, but it sure looks promissing.

hitting a floating container is a theoretical risk

we are all discussing abt hitting a floating container. well, in average only 2500 cntrs fell overboard each year. when you consider that at least 15 million is transported this is next to nothing. furthermore, it is highly unlikely that a container falling overboard will remain intact. most probably with the loads on its structure, it will immy break open and sink. i have seen several times containers hit by waves and remained onboard. they were literally smashed. so, the ones falling overboard will not survive the impact. i believe floating logs is a more dangerous object. i have also seen fridges, bath tubs floating. these may be dangerous in a fast contact.

Codger,
I think you are refering to a system comprising of two steel plates bonded with elastomer composite forming a sandwich panel. This system is marketed by a company called Inteligent Engineering and as we speak Lloyds Register of Shipping has just approved the rules for building vessels using this system. I have seen this system used in Roll On- Roll off car decks with good success. The main advantages using this system is light construction as the need for stiffeners is reduced. noise reduction. and resilience to deformation. I can foresee a substantial use in yachts, particularly for bulkheads, tanktops and decks.

Nilo,
You may find useful to refer to the latest booklet which publishes a study made by DetNorske Veritas (Bondships) on bonded connections aluminium/aluminium, steel/aluminium, aluminium /composite

Monel
I presume you are refering to the alloy. It is corrosion resistant, strong, tough and used for making heat resistant valves, pump parts and propeller shafts. Approx. composition: Nickel :67, copper: 30, iron: 1.4, silicon 0.1, manganese:1, carbon 0.15, sulphur: 0.01. Phusical properties varry depending on whether the Monel is wrought or hard tempered cold rolled, from 35K to 110K pounds/ sq.inch yield strength. There are also alloys denominated as "R" Monel, "K" Monel and "KR" Monel. Yield strengths up to 155K pounds/sq.in. and Brinell hardness up to 290. also "S" Monel, and "H" Monel which are used for hard castings. Is this of some help?