Steel Sailing Cat - Is it Possible ?

[billknny]

Originally Posted by boatman61

Cheaper/easier to home build maybe... also maybe he figures the greater base weight will reduce capsize dangers...

Or you could put a lead keel on it and make it self righting... Oh... wait a minute...

[smj]

Originally Posted by Fore and Aft

Wilf O'Kell Custom 43ft Looking for offers For Sale | Fraser Marine

Darren at Fraser Marine has steel sailing cat for sale. I have never seen her sailing, but the owner does motor her around a lot.

Cheers

This steel cat seems to weigh about the same as the popular 44' charter catamarans.

[billknny]

Originally Posted by valhalla360

It really comes down to the relationship between material density, tensile strength and bending/puncture strength.

Density:
- Fiberglass: 100lb/cubic foot
- Aluminum: 167 lb/cubic foot
- Steel: 488lb/cubic foot

Of course that comes with a trade off in tensile stength (there is a lot more variability depending on specifics here both production of GRP and specific alloy of the metals):
- Fiberglass: 43,000psi (basic fiberglass not carbon fiber or other high end)
- Aluminum: 65,000psi
- Steel: 85,000psi

As you can see, the steel weighs 3-5 times as much bu is only 1.5-2 times as strong. But the real impact comes when considering bending strength. Relative bending strength can be compared by looking at thickness times tensile strength (this is a relative comparison not the actual bending strength). Assuming a 1sft panel has the same weight:
- Fiberglass 4.9" thick by 43,000psi = 206,000psi-in
- Aluminum 2.9" thick by 65,000psi = 190,000psi-in
- Steel 1" thick by 85,000psi = 85,000psi-in

As can be seen, Fiberglass & Aluminum are pretty close. Steel is far weaker for the same weight.

In smaller boats, the required bending strength is small enough that even though heavier, the steel plate is so thin that puncture strength becomes a concern (also working with very thin sheets is more difficult), so you need to up-size the thickness and make the hull even heavier. This can affect aluminum but to a lesser extent.

As boats become larger, the thickness required to handle bending strength becomes thick enough that aluminum thickness handles puncture issues and is thick enough to be easier to work with and you start to see lots of larger cats done in aluminum.

Steel never really gets to be effective. In very large monohulls, steel can have cost and simplicity advantages even though it is heavier but since monohulls pay far less of a performance cost by being overweight, owners can overlook the weight issues.

So far the analysis has assumed solid GRP. If you do a cored hull, the GRP easily has the best strength to weight ratio but it does come with requirements for quality construction methods. You can also get into carbon fiber and other high end composites that outperform just about everything.

PS: I believe the premise that there are lots of marine steel welders desperate for work is a false assumption. In most areas, steel pleasure boats are a rarity, so there are probably 10 times as many fiberglass guys as there are steel welding guys and the skilled welding guys are specialists in marine applications.

Unless you are building your boat, it's really simpler to work on fiberglass boats. Any chemical issues are largely offset when you realize, you need to sand, prime and paint regularly on a steel boat if you don't want it rusting away.

All good points on the material differences, but you left one important one out. With a steel hull you need to add extra material as a corrosion allowance. No matter HOW good care you take of it, rust happens. The hull thins over time. Unless they are going to have a very short design lifespan, you ned to account for loss of mass with time.

The smaller the boat the more of a significant weight penalty you pay.

[cha0s]

Steel catamaran - definitely in theory.

Bruce Roberts has plans for them.

I know a few people who have built Bruce Roberts monohulls in steel. All spent many years (6 years was the shortest and that was full time - 8 to 10 years seems the common figure). All spent about double what they would have buying a similar sized second hand heavily built fibreglass 'production' boat. (not an ex charter French mass production boat - which would be cheaper again).

All started out expecting to save money. All had fairly basic 'workboat finish' boats with comparatively low resale.

IMHO steel ( and especially ferro) cat construction is a folly.

I'm sure the OP knows that and is just having a laugh with this thread.

[cha0s]

Steel catamaran - definitely in theory.

Bruce Roberts has plans for them.

I know a few people who have built Bruce Roberts monohulls in steel. All spent many years (6 years was the shortest and that was full time - 8 to 10 years seems the common figure). All spent about double what they would have buying a similar sized second hand heavily built fibreglass 'production' boat. (not an ex charter French mass production boat - which would be cheaper again).

All started out expecting to save money. All had fairly basic 'workboat finish' boats with comparatively low resale.

IMHO steel ( and especially ferro) cat construction is a folly.

I'm sure the OP knows that and is just having a laugh with this thread.

[ImaginaryNumber]

Originally Posted by cha0s

....IMHO steel ( and especially ferro) cat construction is a folly.

I'm sure the OP knows that and is just having a laugh with this thread.

This thread is 7 years old. I suspect the OP has forgotten he even started this thread

[senormechanico]

Why not take it to the next level?
Instead of steel which rusts, why not LEAD ?

[Karafox8]

LEAD is very expencive

[simonhantler]

Originally Posted by DaveOnCudjoe

I never heard of a steel tri or a steel cat. Both have been built in aluminum but even in that metal prove to be too heavy. Wood or composite is the only practical way to get one light enough and strong enough. Dave

rubbish, checkout elcie 63' devilliers alloy cat, averaged 10knts over 50000 nmls. thats sailed conservativley. thats 240 nkmiles a day, no slouch.

[WilfOKellsKid]

YES! Wilf OKell (proud to say-my Dad) designed a steel catamaran that is for sale in Hervey Bay called Akuma currently going for $199,000. The owner owns the resort of the same name in Hervey Bay. Definitely not only possible but successfully happening. Although this post is very old so guaranteed you would have heard of some since your post.

[CaptRehab]

Originally Posted by Vasco

Check out Lammer Law and Cuan Law they're not cat but tris. I think they're they might be aluminum. Used to see them in the Caribbean. Live aboard dive boats. Both over 100 feet. I think they motor more than they sail. Built in Canada.

Cuan Law is for sale
https://www.yachtworld.com/boats/198...yacht-2974114/