Turning a Mazda MX5 (Miata) into a boat

Discussion in 'Boat Design' started by Mike N, Sep 29, 2021.

  1. Mike N
    Joined: Sep 2021
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    Mike N Junior Member

    Ok, so I'm preparing for a lot of people to call me names for this one but, please, humour my daydream. Sorry for the long story. I live a short walk from the river and work a few miles downstream. On the few days of summer we have in England, my absolute favourite thing to do is put my dinghy in the water and take a lazy commute. The other day I got to wondering if it would be possible to do this year-round. Now, I love being on the water with the wind in my hair on a sunny day but I'm not much of a fan of being cold and wet, so I was curious to see if any boat existed with the same kind of year-round usability and comfort of a car and I was surprised to find nothing really available. They were either open to the elements or solid roof. Maybe a sliding fibreglass top and windy canvas with a million poppers but it's not the same.

    Anyway, so I have an old 2006 MX5 (Miata) which is mechanically perfect but worthless due to rust on suspension blocks and I got to wondering. Would it not be possible to take all the wheels and suspension off, weld the doors shut, and add a hull? It's already rear-wheel drive so the propellor could run off the drive shaft. I'd probably need to do something with the gearbox and of course the exhaust, air vents etc. but could this not work?

    It would give me my perfect riverboat. Roof down in the summer. Warm weatherproof cab in the winter.
    What are your thoughts? Thank you.
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    Weld the doors shut ? How do you get in and out ?
  3. Mike N
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    Mike N Junior Member

    I was wondering that too. My only idea at the moment is inelegantly. I'm sure there would be a way activate the windows by remote control and climb in through there. Or work out a way to open the roof from the outside. But that's details.
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    haha, "inelegantly" ! :)
  5. Squidly-Diddly
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    Squidly-Diddly Senior Member

    I had an old 1961 Ford Van and on the first drive home the rusted frame broke at rear leaf springs but a local welding shop fixed it all up for IIRC $160 total. So if you can see your way clear to adding 5-10lbs of steel you should look into it.

    But I think the convertible top from older American ragtop might be nifty on a boat.

    I want a boat version of my Prius Prime so I can cruise silently (or at full power for short distances) or run a nice engine or both. Due to unibody and carbon rear hatch, and lack of market for savaged parts, nearly new very lightly damaged Primes can be had for under $4000.
  6. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    Welcome to the Forum Mike.
    Which river will you be commuting on?

    Are you aware of the Boat safety scheme on your inland waterways?
    Somewhat incongruously, it would probably be a lot easier (re the regulations) to operate your craft on your coastal waters rather than inland.
    Home | Boat Safety Scheme | Go Boating - Stay Safe https://www.boatsafetyscheme.org/

    Here they mention :
    "Just like a car, on most of the UK's inland waterways, a boat needs to be licensed, insured and have the boat-equivalent of a MOT - valid BSS certification - before it can cruise."

    I am thinking that a BSS Examiner might not be too impressed by your conversion - if he / she approves it, and something happens, the Examiner would probably be the first person to apportion blame on to.

    If you weld the doors shut, is this with the aim of trying to make the car body water tight?
    Or if not, then what sort of 'hull' are you proposing to build underneath the car?
    I am thinking the simplest (and probably the safest, relatively) would be to have your welded up car mounted on the bridgedeck of a catamaran built from two simple pontoons.
    But then you will have an interesting challenge getting the drive shaft to drive a propeller in the water.
    And you need to have a rudder as well......

    Where would you moor your boat - or would you keep it on a trailer at home, and just launch it each time you want to use it?
    But if you want to commute to work then that is a faff to launch and recover it every day - and will you be able to moor it at your work place?
    If you keep it in the water, then you have to pay mooring fees.
    And if you do this, then you might as well just build a 'proper' boat from scratch. :)

    Based on your Statement of Requirements, I am thinking that the 17' Rufus design by Selway Fisher might be suitable -
    Motor Boats 16' to 20' https://www.selway-fisher.com/Mc1620.htm#RUFUS

    Or a 16' Godzilli from Sam Devlin -
    Godzilli 16 https://devlinboat.com/godzilli-16/

    Or a bigger 22' river boat that meets most of your requirements - you wouldn't necessarily need to have the small cabin with the bunks up forward though.
    River Crawler 22 https://devlinboat.com/river-crawler-22/
  7. pironiero
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    pironiero Senior Member

    i feel strong TopGear vibes right here
    DogCavalry likes this.
  8. Rumars
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    Rumars Senior Member

    It is a terrible ideea. All you need for that kind of comfort is a good boat and one of following things (in order of complexity):
    Removable hardtop. This is simply a fiberglass top with gull wing doors. Remove sometimes in spring, put it back in the autumn.
    Good softtop. There is no reason for a boat bimini to not be as sturdy, waterproof and convenient as an automotive one, save for the purse of the owner.
    Folding hardtop. Look around you, some car on the road has one, it's not magic.

    If you don't have an inboard engine you need a auxiliary diesel heater (Webasto, chinese clone).

    Now before you run of to the wreckers looking for a Peugeot 206CC and start liberating it's folding hardtop, be advised that you have to transplant half the car in order to maintain the geometry and sealing surfaces, plus a good electrician to make it work. By the time you do that you can just as well build your own from scratch.
  9. alan craig
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    alan craig Senior Member

    It's a daft idea.
    But you could:
    a) buy an Amphicar.
    b) keep looking for a boat that will do the job; Rivas are nice!
    c) put your MX5 on a catamaran and drive the propeller via rollers under the rear wheels. Front wheels on rotating traps to control steering.
  10. The Q
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    The Q Senior Member

    these are still being made...
    the Dutton Surf.
  11. bajansailor
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    bajansailor Marine Surveyor

    Excellent, this could be just what the OP is looking for :)

    4wd SURF https://www.timdutton.com/4wd.html

    Here is a photo from their website with the caption
    'What are the chances? An amphibious caravan passing an amphibious car...'

    Dutton amphibious car.jpg
  12. The Q
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    The Q Senior Member

    I must admit that I've thought of having an amphibious car, drive to the sailing club, down the slipway, cross the river, get the sailing boat out, put the car in the pen, opposite on return..
    A lot easier than getting a rowing boat and paddling across..
    I've seen an Amphicar going down the river past the moorings...
  13. jakeeeef
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    jakeeeef Senior Member

    I've seen this done a few times.
    He's not talking about an amphibious car by the way, just a boat that looks like a car on top.
    One good one I saw was done in Japan using an old grp speedboat hull with the top half of a Lotus Europa (early 1970s version) glassed on top.
    Best way of doing it, grp car attached to grp boat!
    However, that was done when an old Lotus Europa from the late 60s/ early 70s was a grand for a tatty one. Not so now!

    Always when I've seen this done it uses an existing boat hull for the hull.

    I guess you could do it with the top half of an MX 5 and an old speedboat hull of roughly equivalent size and shape. But you're bonding metal to grp which will not go well, it will be top heavy, a lot of work to create something utterly worthless etc. Unlicencable on UK inland waterways.

    It's not as imaginative, but you will save and even make money by breaking it for parts, selling the bits on eBay, and using the balance to buy a nice little boat! Early MX5 bits are getting hard to get.

    But, a subsidiary point that I suspect is what has also prompted the OP, is while cars have really cosy, waterproof roofs and wind up windows, why not small boats.
    That is a valid point, and I guess it relates to boats being often
    a summer only toy, having to be built down to a price, having to be easily got in and out of, moored etc. and light as possible to launch.

    It amazes me though how it's only the last few years and it's only certain small boats that we have started getting completely waterproof wheelhouses, electric folding roofs etc. .that you got on cars years ago.

    I once thought of making an ice cream boat out of an old ice-cream van top, glassed onto a boat. The old ice cream van tops in the 1970s were grp and looked awesome. It would be doable and gain a lot of interest/ summer trade. It was the stability calculations that scuppered it. You'd have to make the ice cream van top half so squat it wouldn't have looked much like an ice cream van any more. Might have worked with a keelboat hull for the bottom half, but then it wouldn't have been easy to trailer and the hull became too different a plan view shape to the rectangular ice-cream van.

    In the end, it looked like it could work with a Wilson Flyer type hull, with a heavy lifting keel box put into it for stability without ruining trailer ability.

    Anyway, didn't happen. Nor will this MX 5. It's amazing how much work these things actually are once you look into it!
  14. Mike N
    Joined: Sep 2021
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    Mike N Junior Member

    Thank you! It's nice to be here.
    I'm on the River Stour in kent. It's not connected to the inland waterways network and so there is no requirement to have the boat licenced. Or at least if there is, there's no enforcement. I've been messing about on the river in inflatable dinghies and homemade boats since I was kid.

    I used to work as a deckhand for a river tour company many years ago, I'm still pretty friendly with the owner and they let me use a small mooring spot on the corner of their pontoon.

    A catamaran could work... I think my friend might still have a couple of hulls in his barn from when we built "Floaty Smokey" a few years back. A couple of hulls lashed together with scaffolding poles and patio decking on top with a sofa, BBQ and outboard. It's not quite the dream vehicle though... At the moment is pie in the sky but you know what it's like when a silly idea takes hold.

  15. Mike N
    Joined: Sep 2021
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    Mike N Junior Member

    Exactly! I want to be able to wind down the electric windows, have 360 views around me without a sliding hardtop in the way. Watertight, windproof comfortable interior with heated seats and heating coming directly from the engine. An engine that sounds good and not the loud "CHUKA CHUKA CHUKA" that normally comes from diesel inboards.

    All things I could get in a car very affordably. Bimini tops are fine to protect against the sun but unless the rain is coming straight down it generally still gets into the boat and does nothing to help with the wind or cold.
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