aluminium tender or RIB?

Discussion in 'Boat Design' started by expedition, Sep 23, 2009.

  1. expedition
    Joined: Jun 2007
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    expedition Thorwald Westmaas

    We need a tenders for a yacht that can carry up to 12 divers or up to 15 guests.

    We're looking for a cost effective and durable solution and looking at RIBs and aluminium tenders.

    When compared I see the advantages of RIBs:

    - less weight (smaller crane needed)
    - lots of seating area (although not so safe in rough seas)

    and advantages of alum. tenders:

    - typically seem to require smaller engines with same capacity
    - pretty much eternal life
    - easy to customize even for small quantities
    - more internal space at same width
    - smaller engine, less fuel use
    - fueltanks and storage space can be integrated in hull

    What other advantages do RIB's have besides the weight?
     
  2. Ad Hoc
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    Ad Hoc Naval Architect

    A RIB to satisfy the duty you have listed wont be cheap, nor small too.

    When you say Aluminium tender, what do you mean by this, do you have a "type of boat" in mind or, the actual definition of "Tender", a small boat doing the task described? Since the RIB is ostensibly performing the same function, it just happens to be a RIB, and thus is alkso a Tender
     
  3. expedition
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    expedition Thorwald Westmaas

    RIB render or alum. tender

    I was suggested I'd need a wide (2.8m) 7-7.5 long RIB as a minimum and require a 250-300 hp engine.

    If I'd use alum. it seem 7 m. is about enough and the wide can be 2.4 m. and a 200 HP engine would do the job (20-25 kn. speed is enough)

    Sorry for not being clearer. I mean the actual definition of a tender and the question is: what are the advantages of a RIB tender vs. an alum. tender.

    Thorwald


    >RIB to satisfy the duty you have listed wont be cheap, nor small too.

    >When you say Aluminium tender, what do you mean by this, do you have a "type of boat" in mind or, the actual definition of "Tender", a small boat doing the task described? Since the RIB is ostensibly performing the same function, it just happens to be a RIB, and thus is alkso a Tender
     
  4. mark775

    mark775 Guest

    The reason the aluminum boat requires less HP is that it is lighter. The RIB is designed so that the tubes are not much in the water so shouldn't be a factor. One can build an aluminum boat much cheaper but the advantage of the RIB never needing a fender is a big plus. They make RIBs with aluminum hulls, BTW.
     
  5. Knut Sand
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    Knut Sand Senior Member

    A rib is pretty easy to enter as seen from a divers view (one man aboard though), an alu boat will probably also need a dedicated divers ladder, which is no problem either.

    Another thing to consider; what kind of divers? Photographers or hunters...? A group of clumsy divers with sharp objects, may cause some problems with a rib (rip?) well been there, done that; my speargun, not cocked, not me, but repositioned by one fellow, and kicked into by another, the pointy end went into the tube, well, the hissing sound caught our attention you may say... No real problem though, as said above; the tubes are seldom in the water, also; there are several isolated chambers. So; the dive wasn't aborted.

    It'll end up in; money(boat/ crane/ engine(s) preferances)/ what you'd prefer/ dry or wet operation/ other uses for the boat?
     
  6. expedition
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    expedition Thorwald Westmaas

    Dear Knut,

    Thanks for the comment. Enjoyable too... imagining how tubes and sharp object interact at times.

    We'll have all kind of divers but rarely hunters (we'll be diving national parks mostly). We will be beaching a lot and not always Bahama like beaches but beaches will small stones and/or lots of shells. I'd say alum. has an advantage there.

    I was also told about the problem with RIBs and V-hulls in general that they kind of 'wiggle' when beaches, making getting in- and out- especially for a little older people, problematic at times.

    So I started looking for catamaran tenders and came accross this very interesting design from Feadship:

    http://www.superyachttimes.com/editorial/11/article/id/578

    I'm sure it could be made a little less fancy and from aluminium too.

    Compared with RIBs that have bow ramps it looks a lot more elegant. But then again, it's a Feadship :).

    As far as crane goes, if we go alum, we'd put them on our deck before the bridge which gives us access to a 10-ton crane. When we're at location anchored in some bay, we'll have the tenders in the water all day and night.

    Thorwald
     
  7. apex1

    apex1 Guest

    The RIB is heavier! At least when you compare the same size of safe seating.
    But I recommend the RIB anyway, it serves common explorer yacht needs better than a Al or Grp boat. I replaced my Boston whalers (good boats) with RIB´s after one year of intensive cruising.
    And longevity cannot be of any concern on a true explorer of that size!? What is the replacement of one or two tenders every 8 years or so?
    The "little older" people you can leave ashore (with sufficient food and water), when they have a problem to enter a RIB they have a problem to survive even a nice trip in sea state 5!

    Regards
    Richard
     
  8. Squidly-Diddly
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    Squidly-Diddly Senior Member

    which exact models are you looking at?

    I'd vote for metal...worry free and probably higher re-sale value. Better for hauling cargo.
     
  9. expedition
    Joined: Jun 2007
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    expedition Thorwald Westmaas

    whaler

    Hi Richard,

    Which Whaler model did you have? I don't see any on their website that would meet our requirements as bording after beaching the bigger models would present a major hassle.

    Thorwald
     
  10. apex1

    apex1 Guest

    A 17 and a (not sure) 19 as far as I remember. Not big enough for your demand. But I mentioned them as a example. (and did´nt have others to replace)
    Another thought: I had the tanks built in! One was a Castoldi jet, the other a Novurania with OB. I was restricted to a length below 6m but I guess your deck can house some 7m with ease!? Any RIB that size should do the trick. If it´s a jet driven they are pretty easy to board too (but not cheap). And it doubles as a rescue boat without additions or changes!
    But what is cheap on a boat that size? The annual fixed cost will be about 1,5 to 2 million$ I guess. Do´nt make the mistake to calculate 10% of the conversion cost as your annual cost (many amateurs do so). The cost is the same whether the boat is 1 or 100 years old! And thats about 8% of the newbuild. At least that was true for ALL my boats during more than 35 years.

    Richard
     
  11. Ad Hoc
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    Ad Hoc Naval Architect

    A catamaran tender has many benefits, such as extra deck area, greater stability (all very useful since divers have lots of gear), flexibility with seating/layout and at the higher Fn's lower power requirements too.
     
  12. expedition
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    expedition Thorwald Westmaas

    Thank you both for your comments.

    I just found a post about this British design for tenders/workboats called the Flugga boat.

    See: http://www.fluggaboats.co.uk

    It's a RIB type design that features a sturdy aluminium hull with a buoyant UV-resistant plastic pipe replacing the inflatable RIB collar component, making it a very durable and low maintenance design.
    The collar is non-pressurised and basically indestructable. The sun doesn't really harm it either and you get more internal space.

    Looks like a great idea. So I wondered, why haven't I heard about it before? There's practially no info about this design online.

    For our particular case I like the idea of a collar that cannot be punctured and they use alum. All I need is have them design a smaller collar to put it on a an alum. cat (so I can my ramp) and get a nice fender and extra boyancy into one.
     
  13. Ad Hoc
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    Ad Hoc Naval Architect

    Thorwald

    This type of RIB design with the non-destructible buoyant tube is nothing new. We designed a very successful one for the UK Army many years ago...and a variant for the US.
     
  14. apex1

    apex1 Guest

    >>>All I need is have them design a smaller collar to put it on a an alum. cat (so I can my ramp) and get a nice fender and extra boyancy into one.<<<

    And why not ask them?
     

  15. expedition
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    expedition Thorwald Westmaas

    >And why not ask them?

    I already did and we're looking into it :)

    I just tried to get some feedback from the experienced folks on this forum.
     
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