Deployable, shallow submersible observation pod for Catamaran

Discussion in 'Boat Design' started by abosely, Oct 7, 2019.

  1. abosely
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    abosely Senior Member

    Wondering if this might be feasible or not, must not be or it would have been done.
    Thinking about the feasibility of building an observation pod that could be deployed between the hulls of a Cat, in my case a Narai MK IV, it has four big beams to carry the pod.

    Would want it mounted as far forward as possible, so the nose of the pod was as close to or just past the bows.
    Pod would only go six to ten feet below the surface, would not be deployed for general sailing, just in mild conditions and at slow speed. Would be retracted or brought up on deck for normal sailing.

    Probably use water ballast to submerge ans bring to surface. Thinking of some sort of a tube for entry and exit. Of course safety would be paramount.

    Ideally would be large enough to hold two people at a time, don't know if that would make it to big or not though.

    Since it's not submerged deep, water pressure isn't an issue, like a deeper submersible would have to deal with. Build it out of composite and use flat or single curve viewing panels.

    Curious to see you guys thoughts, I mean this might be completely impractical idea. lol

    Cheers, Allen
  2. bajansailor
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    bajansailor Marine Surveyor

    It sounds like enormous potential for things to go wrong very quickly - make a mistake with the ballasting or the method of deployment and the pod could quickly become a coffin.
    Is your Narai a charter boat where you take passengers on coastal cruises? If so, I am guessing that you want to offer this submersible as an extra that is novel and different?
    Getting insurance for it could prove to be very difficult if not impossible....
    If people want to see what is 6' - 10' below the surface, it would be much easier to put a Go-Pro camera on a very long selfie stick and let it feed to a TV monitor on deck. This will have MUCH less frictional resistance than a pod large enough to accommodate one or even two people. And you would be able to deploy it even while sailing, if desired.
    Oh, and even 10' below the water surface there is still quite a noticeable increase in pressure - you notice it when you dive down and your ears hurt because you haven't equalized the pressure in them.
    fallguy likes this.
  3. TANSL
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    TANSL Senior Member

    Why not a glass bottom boat, similar to many others that are already sailing the seven seas?. Let's suppose bottom and side of glass, to include some innovation.
  4. abosely
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    abosely Senior Member

    It would just be for my benefit.
    As I said, probably not practical or would have been done before, or at least commonly.

    Was one of those thoughts that came up in my head and thought I’d get some perspective about it.

    As you point out, with GoPro type cameras not much reason to do something like this.
  5. Squidly-Diddly
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    Squidly-Diddly Senior Member

    its either going to be coffin tight (including access tube) or it going to take huge force to push it under water. Water ballast isn't "real ballast" in this case. You've got the air-space minus the "crew" and the rest of the boat is gonna need to push that under. No reason to add water ballast to boat, just let pod push boat higher.

    "deploy-able" (moving parts) sounds like death-trap. Its gonna be cramp, something jams, it floods and something blocks escape.

    I think you'd be better off with plexiglass underwater windows in hull, and build to survive that section of hull flooding. That would allow frequent casual use by you and guests, as opposed to high drama death defying infrequent stunts where you'd be too worried about a disaster to view the fish. IMO any super-yacht should have underwater viewing room just aft of the bow, and maybe also aft, since I hear lots of big fish like to follow boats.
    bajansailor likes this.
  6. Tiny Turnip
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    Tiny Turnip Senior Member

    6 year old very sub (ha! see what I did there?) Go Pro on a stick dangled off my pedal cat in murky waters. Im sure you can do much better still at a fraction of the cost, danger and difficulty of a pod:
    Rurudyne likes this.
  7. abosely
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    abosely Senior Member

    I realize this isn’t a good idea.
    Just a thought and wanted to see if it might be feasible, but as has been pointed out not a good idea.

    This wasn’t a thought out idea, just something that popped into my head.
    Wanted to get some thoughts on it.
    all very good points and definitely not something I’m going to think about doing.

    Thanks for the input guys.
  8. W9GFO
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    W9GFO Senior Member

    I think you are underestimating the forces at that depth. Water pressure at ten feet is approximately 5psi. A one foot square flat panel would have to withstand over 700 lbs of force.
  9. Squidly-Diddly
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    Squidly-Diddly Senior Member

    what might work is open top (for might flood but wouldn't trap you) "pod" that allows viewer to use prone position. Basically an attached Glass Bottom Boat. Only need to submerge about 12" to get 95% of the benefits for underwater viewing, then about a 2-3' tall coaming around it to keep out waves and spray, and cover with dark bedsheet to cut out light pollution above the viewing plates.

    I've noticed many prone position aircraft don't take full advantage of looking directly down. Xd2wr.jpg
  10. Squidly-Diddly
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    Squidly-Diddly Senior Member

    Now I'm thinking this could work as a big fat airfoil shaped daggerboard made out of plexiglass. It would be about 30" wide, and 8' deep, and 10' long, seating about 4, with about 16" of freeboard when deployed, so people's eyes would be about 4' off floor when seated and thus about 2'+ under water level. The upper 2' would be blacked out and a sunshade would cover to prevent "light pollution" for best underwater viewing.
  11. Mr Efficiency
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    Mr Efficiency Senior Member

    retractable sounds like an engineering nightmare, why not just use the catamaran hulls, either or both, I was on a whale watch catamaran one time, that had that, the bows were a little fuller to give the space.
  12. clmanges
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    clmanges Senior Member

    A real cheap and easy solution would be to take a length of plastic pipe, bond some handles on the sides of it, and install a clear plastic window in the bottom end. You'd have to stop to use it, I think, but you just stick the end in the water and look down through it. Want to get fancier? Put an elbow at the end of the pipe and install a mirror in the elbow to make a sort of inverted periscope.
  13. brendan gardam
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    brendan gardam Senior Member

    there was a boat constructed exactly like you describe. it used to appear on television occasionally. the plexiglass pod was mounted on arms which were attached to each hull with hinge points. as the boat accelerated the pod submerged . when the boat slowed down the pod raised up again. it was very safe being positively bouyant and using water pressure on diving planes to submerge.
  14. Squidly-Diddly
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    Squidly-Diddly Senior Member

    Got pics? "hinge points" might make me nervous. What if a floating log or other random man made objects or rope (found about 20ft worth of plastic picket fencing the other day) gets jammed in the hinge points or between pod and boat? But I guess people do a lot of less safe stuff, and you could always have a couple (in case you drop one and it sinks) fire-axes handy to aid emergency extraction.

    But I'm thinking the most practical way to get most of what the OP wants is an enhanced version of this principle.Science First Aquavue Underwater Viewer, 26 Inches Instead of a 2ft long tube with 5" window on the far end (narrow pipe required because less strength to hold underwater), make something that flares out from face-interface to "wide view" of at least 30 degrees, and have it mounted on a swivel axis so the user doesn't need to push against 100lbs of buoyancy but can also "look around" actively.....all while staying relativity safe and dry above the water line. This would be done on a special face-down cushion and the view-device would have handholds and maybe forearm rests to make extended viewing comfortable. Care should be taken to eliminate unwanted "light pollution" but still have enough light to view underwater.
    Last edited: Dec 16, 2020

  15. Rurudyne
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    Rurudyne Senior Member

    Another improvised version: the child wears scuba mask and you dangle him from the bridge deck by his ankles. A low on cost, high on Redneck Engineering solution.
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