aluminium tender or RIB?

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

  1. kmorin
    Joined: Apr 2005
    Posts: 185
    Likes: 18, Points: 0, Legacy Rep: 231
    Location: Alaska

    kmorin Senior Member

    RIB vs Less Rub Rail


    Thanks for the interesting question that sparked the discussion I've just read it and learned quite a bit about RIB's.

    I am left with a thought from reading this through. All you're really asking is how much of the sides, of the welded aluminum skiff that will service your larger boat should be bumper/rubrail/fender/softer than the rest of the hull?

    If we looked at a completely hard sided welded aluminum net skiff that has nothing but aluminum pipe or extrusion at the gunwale - we're at one end of the spectrum: solid metal.

    Then if we look at the RIB as they've been shown here we're discussing a welded aluminum boat that has 'soft' sides almost from chine to sheer: completely softsided.

    They aren't very different boats, welded, V bottomed, outboard powered, stronger than needed but still light and will take rocky beaches better than most other materials. All that seems like is really in question is how much rub rail you want on your 'tender'?

    None, landing to a buoy like the commercial boats do; Some, maybe a rubber extrusion on the hard sided skiff with additional cushions; or All, where you build the RIB version of the welded boat?

    If you built a soft sided 'buoy net' or landing bumper to receive a 'hard sided' boat you would have the same docking result if you used the soft sided boat since you're likely to use one boarding port on the larger boat?

    I've talked with divers who wanted ladders and a hard sided boat with a door, and others who prefer to roll out onto RIB air chambers, it will be interesting to see if there is any consensus on how much rub rail is the 'best' choice?

  2. mark775

    mark775 Guest

    the pvc tubes have no purpose but force your hull shape and take up space.
    "We use HDPE for the collar and the collar is formed to fit the shape of the hull, not the other way around" - Sorry, they looked tubular to me. I refer to the hull shape INCLUDING the pontoons.

    I watched the video of these boats and they do quite nicely in the protected waters that were chosen in which to show them. It is stated "our hulls are designed to take 14 g impacts". I had remembered seeing somewhere that a fighter pilot will likely black out at sustained nine Gs, so I went looking for that and to my dismay, I found that roller coasters routinely momentarily produce that with no ill effects to the occupants. Looking further, I found that "flopping down on a couch" to watch fighter pilots might produce more momentary Gs, or acceleration (deceleration), than the pilot!
    So, curious, I thought about why I don't think all that much about these type of boats. Tho I have spent some serious skiff time on seventeen foot Achilles inflatables shuttling people and equipment to most of the Aleutian Islands while working for USFW aboard the M/V Tiglax (TEKH-lah - Aleut for eagle), most of the time was in water just like the promotional video. BUT, I have also seen the same skiffs broach and capsize with four passengers and a very competent skiffman. I, myself, have flipped these inflatables completely over backwards, lucky to have no casualties - Tho these type of loads are not the ones that bother me. It is when an operator comes in too hot and makes a point load on the corner of a ship, or when one has to beach in rough water on rocks - I dare say that the G forces of some of the stuff I have seen would destroy these PVC things in short order (what about in cold?). I actually thought, for a second, that the promo video would show a point load to demonstrate durability at the the 4:30 point, but no. I actually saw no point in the video where the boat would not have performed better with no pontoons installed - just a bare aluminum hull. Which brings us full circle back to the inflatable. It does the same thing but has a big fender installed all the time.
    Why do divers use inflatables so much? Simply because they are the smallest thing with excess stability to handle the side loads of rolling out/climbing in and are low to the water. A pro diver usually detanks in the water, handing it to crew, then climbs aboard, sometimes with a helping hand. It doesn't always go smoothly with tourists, especially the fat Americans talked about. It is my contention that a stable boat with a side gate or, better yet, an aft platform, will be the optimal dive boat for this.
    Pangas are heavy - just a point of reference but do realize that the form is well-used in that part of the world because it is a damn fine boat that doesn't broach easily, takes a tremendous beating, has huge reserve buoyancy...and looks the part.
    To each their own. I feel that a custom aluminum cat with bow ramp will fit your needs as long as the weather doesn't get too rough. You have the money - get one of each!
    Also, something about the American boats being "overbuilt" or words to that effect - That's the one thing I do like about the boats in question. Enough of this "Herreshoff" style cleat, and so forth, that couldn't hold a moth. I want my hardware to not be the weak link.
    Jones act. Well, protectionism may have been partially to blame for this but the Jones act serves a real purpose and of this, I approve. It is to keep American shipbuilding viable so that we have an industry in the event of war. Granted, it pisses me off that some union slouch is napping his hitches for months on end because he is the only one with clearance to a certain part of a nuclear sub under construction. In fact, even worse, that the companies have to pay such high wages and benefits to these people that the shipbuilders would simply leave if it were not for the Jones Act. But, given the circumstances, the Jones Act is necessary, as I see it. Are European countries able to buy a ship, for example, made in Somalia and ply trade in the English Channel? I see that you are in Japan, Ad Hoc - probably the most protectionist major country in the world. It is frustrating at times, no?
    Tariffs, and other forms of protection always make things more expensive and not necessarily better. Witness the Chinese Tire Tariffs Barack just slapped on the Chinese to pay back his union sponsors. The poor people needing new tires will pay more for tires and have fewer choices because of this. Everyone is poorer, from here to China, for having fewer choices. On this I agree.
  3. apex1

    apex1 Guest

    That, Mark is the point:
    >>>Why do divers use inflatables so much? Simply because they are the smallest thing with excess stability to handle the side loads of rolling out/climbing in and are low to the water.<<<

    On expedition yachts you have that situation quite often, that you have to load or discharge substantial weight sideways. And I (and my crew) was happier with the RIBĀ“s than we have been with the Whalers.

  4. mark775

    mark775 Guest

    They certainly have their good points but everything is a compromise.
  5. Jack B
    Joined: Sep 2009
    Posts: 4
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Shetland

    Jack B New Member

    more of the same.

    Hi Mark 775,
    If you look in the performance clip at about 5m30sec you will see how they take a bit of sea. The reason for the high G rating is that they are built so that the limiting factor is the crew and not the boat, ie the crew will slow down before the boat gives up. We did have one that went ashore in about 1.5m seas when they driver pulled the kill cord accidentally. All it did was scrape the bottom and flatten one planing batten, and she was sliding from keel to chine. Even we were impressed.

    Apex 1, I'll look into why you can't get any info. but if you reply via the web page I'll email directly some drawings etc.

    What a lot of folk misunderstand is the reason for using a rib. The collar is reserve buoyancy which , because of it's location, acually makes the boat more stable when swamped. It is not intended to be a fender, that is a side benefit.

    Cheers guys, good discussion this.
    Jack B
  6. mark775

    mark775 Guest

    Very well and good. Thanks - Mark
  7. apex1

    apex1 Guest

    Nice and prompt response thank you!!!

  8. expedition
    Joined: Jun 2007
    Posts: 81
    Likes: 3, Points: 0, Legacy Rep: 81
    Location: Panama

    expedition Thorwald Westmaas

    Hi Richard,

    Thanks for your reply. Indeed, estimating the market value of any yacht right now is difficult and being an expedition yacht doesn't make it easier.

    For now, we're estimating it at $ 10-11 m. but it's partly an academic question as we have no intention of selling it any time soon.

    And I agree keeping it in class is a worthwhile investment.

  9. expedition
    Joined: Jun 2007
    Posts: 81
    Likes: 3, Points: 0, Legacy Rep: 81
    Location: Panama

    expedition Thorwald Westmaas

    Hi kmorin,

    You're most welcome. I've learned a lot too !

    And the soft-sided 'buoy net' is another good suggestion.

    Mark, thank you too for sharing your thoughts so generously.

    As to the divers convenience, my idea is to have it both ways (or 'all ways'):

    - doors in the side

    - a HDPE collar designed in such a way you can actually sit on the
    bulwark and let your self fall overboard

    - use a cat design for increased stability

    - possibly a fold-down aft platform as well, possibly removable when
    the tender is not used for diving.

    The main reason for the cat design would be the forward ramp and not have a 'wiggling' tender when bording it on the beach; this based on feedback from naturalist guides taking guests ashore on RIBs with V-hulls.


  10. Feto
    Joined: May 2010
    Posts: 2
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Coventry, United Kingdom

    Feto budding designer

    if you are looking for a RIB that is light and uses less fuel you should look at these guys: . plus black is cool.
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.