Lack of data about steel multihulls

Discussion in 'Multihulls' started by Muzammal, May 18, 2021.

  1. guzzis3
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    guzzis3 Senior Member

    There is suspicion about his past behavior that I can't prove so I've no interest in attracting a court case.

    And his designs are terrible.

    Given the time and money to build a big cat why wouldn't you choose someone with an impeccable record ?

    Multihulls are not like monos. Look at the beneteu blue 2 to see how badly that can go wrong.
     
  2. Bobuk25
    Joined: Jan 2019
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    Bobuk25 Junior Member

    Hi all,

    Just reading this thread and I have a 12.5 metre steel sailing trimaran. Now I would not suggest it is a logical thing to build a steel tri under 60 foot, however when I hit the subsurface rock last summer at 4 knots, I felt quite relieved that she was steel! Which reminds me, I must paint the scratch.

    Whilst she is not fast, she is pretty economical under engines even with 50 year old Merc diesels. As for weight, she is ten tons, which is very heavy, however less heavy than those Lagoon catamarans (12 tons+). Speaking of which, I have been shocked by those Parlay Revival YouTube episodes detailing the cracked bulkhead issues, the 450 is 15 tons and only has 18mm ply bulkheads? My table is 18mm...

    Anyway, I do agree that it is not a logical choice of material for a small tri, but it can be shaped quite nicely and will not get osmosis.
     
  3. bajansailor
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    bajansailor Marine Surveyor

    @Bobuk25 would you like to let us have some photos and further information about your steel trimaran please?

    I am sure that many on here would be very interested.
     
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  4. redreuben
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    redreuben redreuben

    Lol “Steel won’t get osmosis”
    Isn’t that a bit like saying grapes are gluten free ?
    A steel tri would be fun on a racecourse, port and starboard?
    Go ahead make my day
     
  5. Bobuk25
    Joined: Jan 2019
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    Bobuk25 Junior Member

    Hi
    Given some of the feedback I have received in marinas and such over many years, I am a bit reluctant to stick my head above the precipice, but here goes...

    https://m.youtube.com/c/SailingSVPipedream

    As said, I would not recommend building such a boat and she is not fast, but as a cruiser, she does bring peace of mind and is surprisingly easy to single hand - which is a good job given my lack of skills.
     
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  6. redreuben
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    redreuben redreuben

    Mate that’s epic !
    I’d never build one either but I’m glad you did, it’s useable art. Love it.
    Good job
     
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  7. Bobuk25
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    Bobuk25 Junior Member

    Thanks very much, for some reason I have no like button here - but here is a :)
     
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  8. Bobuk25
    Joined: Jan 2019
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    Bobuk25 Junior Member

    Hi all,

    Just thought I would add to this thread to say that I was tinkering around with my mast design today and calculating Sail area displacement ratios (well using the online calculators as I can not be bothered to figure out cube roots), when I came across this:
    https://www.boat-specs.com/sailing/sailboats/lagoon/lagoon-39
    So you don't need to click on the link I will summarise to say that the glass fibre Lagoon 39 has a 'light' displacement of 11.6T, and only 818 sq feet giving it a ratio of 15. A carefully built steel cat could get quite close to that displacement and would not have bulkhead cracking issue after a few years.
    Despite this and my own choices, I am still not advocating steel for multihulls, but with some of these heavy glass fibre cats, I do wonder if they are not just a bit too heavy. I presume by the time people have owned them a couple of years, that tonnage figure will grow in much the same way as my waistline over Christmas... So steel may not be an obvious or logical choice, but it is not as far from logical as one would think.
    Now what about titanium? - I heard of a chap who after the collapse of the USSR, had a hull made from titanium at a rather good price. Alright that may have been luck and right place at the right time, but aluminium is I think the way I would go if I were to build again.
     
  9. oldmulti
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    oldmulti Senior Member

    Attached Files:

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  10. Iridian
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    Iridian Junior Member

    Do you have any idea of the cost of this in comparison to a high end composite? say Carbon Fiber?
     
  11. guzzis3
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    guzzis3 Senior Member

    The other reason I'd not build in any metal is corrosion. Epoxy does not like UV but if you build a foam glass hull with polyester or vinylester it's pretty indestructible. If you go through a period where maintenance lapses it'll still be there and salvageable where your metal hull might have terminal rust. Same problem with timber.

    Being able to carve furrows in the ocean floor while maintaining hull integrity does give peace of mind. I know people with steel monos who love them.
     
  12. Iridian
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    Iridian Junior Member

    I feel the same way generally, but with the titanium boat linked by old multi that shouldn't be a problem. Welding characteristics should also be improved over alu.
     
  13. oldmulti
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    oldmulti Senior Member

    Iridian. Titanium is not cheap if brought new and requires specialist skills to build with. There was some "cheap" used titanium around with some imported from Russia. Some of it was radioactive as titanium is used in nuclear reactors. I will reference Guzzis3 comments on another thread. He has worked with titanium and considers it very hard work, a lot harder than steel or aluminum. He would not build with it. I understand the want of a "bullet proof" boat. Please understand a well built foam glass boat will be just as good as a steel boat in light hits. If you run onto rocks at speed even steel may not survive. Think Titanic, Costa Concordia etc.
     
  14. Bobuk25
    Joined: Jan 2019
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    Bobuk25 Junior Member

    I have to say that in terms of longevity and ability to restore, steel in my opinion is by far the better material. It is easy to repair in almost all countries, widely available and its strength can be tested with a very large hammer when in doubt. Glassfibre has an element of hope to it. You mix the resins, work around temperature, humidity, batch age, traceability, manufacturer's variances and such and then hope that it all worked and is at its full strength. Even then with osmosis and especially with a lot of lighter built boats with balsa cores and such, you always have that uncertainty. Whereas steel with good proper preparation for paint is dependable and is generally easy to get to full strength. Welding may require some skill but it is a lot easier to attain best results and only relies on good equipment and a good power supply. When it comes to repair, steel is (depending on design of boat) easy to cut out and replace and will return to a similar or same strength as when new.

    Epoxy may not like UV, but paints like Jotun Jotamastic (£75 incl VAT and shipping from UK stockists for 5Ltrs) are pretty robust and although they will chalk up, this is not as much of an issue as you would think. I have left some bits on my boat in grey jotamastic primer and it does need another coat every 4 years or so, but that is very simple to do. A polyurethane top coat will easily resolve even that and will last a very long time.

    The piece of mind is also great - I ran into a submerged rock last summer at 3-4 knots or so and just have a scratch which I keep forgetting to paint. When I go through Arzal lock single handed, I can drink tea and watch as glass fibre boats bounce off each other leaving scratches, cracks and such. When they hit my boat (which usually happens at least once a year), I do not even get a scratch as I have edged all my corners and sharp bits with 8mm stainless steel rod. I only use fenders to protect other people's boats or to protect the lock sides. Last summer on the same trip as the rock incident, a 30 footer with crew ran into me and ended up with a crack in the side, they looked at me accusingly which I was somewhat bemused at as I was all tied up in the lock and it was one of their crew that had accidently let go of the line too soon.
     
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  15. guzzis3
    Joined: Nov 2009
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    guzzis3 Senior Member

    I'm always reluctant to discourage people from experimenting and pursuing their ideas, this is afterall the boat design forum. On the other hand I feel compelled to warn people that some ideas are likely to fail and suggest they consider how they feel about losing that money and time.

    You could build a catamaran out of paper mache if you covered it in something waterproof. The longevity and reason for this is questionable but anything is possible.

    When an engineer (with a clue!) is asked to design something they consider resources available, money, labour, life of item etc. The criteria for those foiling catamarans is very different to a liveaboard cruiser.

    With this in mind here we are usually considering moderately large cruising multihulls. Damage is a valid concern but glass is easy enough to repair and provided it's solid or foam core rot is not a consideration. Vinylester and epoxy address the osmosis problem. On the other hand while metal hulls have some advantages insulation isn't one of them. Hull weight needs to be managed and of course most metals will rot in salt water given half a chance.

    This doesn't make metal hulls a terrible choice. Properly executed it can be a very good choice. If there were an option with no downside everyone would adopt it. I could knock out a steel hull bridgedeck cabin cat in my back yard half drunk and sleepy, but it would need to be at least 40' ish. Then I'd want it well protected from the salt and I'd accept that it was going to rot away some day, and need recoating from time to time. Building in glass epoxy foam I get better insulation, seawater is irrelevant but I need to be mindful of UV. Dearer than steel here also, but then you add the cost of insulation...

    There isn't a clear winner, only choices and compromises.
     
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