Velomobil tender, micro cruiser camper

Discussion in 'Boat Design' started by Dejay, May 2, 2020.

  1. Dejay
    Joined: Mar 2018
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    Location: Europe

    Dejay Senior Newbie

    Thanks! Could you explain that or do you have a link for the concept? I have a hard time picturing this.

    I'd definitely would want to make the boat unsinkable with foam core construction and additional flotation.

    Interesting idea with the skin of frame "top boat" haha. I guess you could make that work. A consideration would also be the insulation foam core provides for camping. Maybe that is silly and you'd also need foam covers for all the windows where heat can escape. Or just take a small heater.


    Good idea. But theoretically with two 340 watt solar panels on top you could get about 3.2kWh a day in higher latitudes (Hamburg, London) in summer or in Mediterranean latitudes even in spring / fall. So on sunny days you might never run out of energy while driving on a road.
     
    Last edited: May 3, 2020
  2. clmanges
    Joined: Jul 2008
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    clmanges Senior Member

    Amphibious vehicles are problematic. A thing that works well on water is lousy on land, and a thing that works well on land is lousy in the water, so most of them are lousy at both. This is probably why most amphibious vehicles are built for military use; they don't care about efficiency.

    The 2" wide tires won't be adequate either; you'll need the truly fatty 4" jobs for when you try to beach on mud, sand, or soft soil. I've seen at least one boat ramp with deep, soft, sucking mud where even those would probably not get traction; it was like bearing grease. Then you need ridiculously low gearing to power them. You'd also need a lot more ground clearance than seems apparent in your drawings.

    I have an idea, but it won't satisfy your sleep-aboard objective. Make a small platform boat, maybe a cat barge, and set up a bicycle training stand on it and power it from the trainer's rollers. IIRC, this has already been done.

    That's all I'm good for; hope it helps.
     
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  3. Rumars
    Joined: Mar 2013
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    Rumars Senior Member

    I think you need to better define what you want. A tender to a bigger boat is a service vessel, it is intended to carry people and gear a short way to the shore. It must have integral bumpers as to not dent the motherboat, motor and row, and be stable loaded to the max. If longer trips are planned it should plane, and be light enough to be dragged on the beach. Such boats end up looking like RIB's do for a reason.
    A human propulsion vessel that you can cycle and sleep in is different. Beam and lenght are limited by handling it on land, so carry capacity is also limited. Stability is not a priority, shape is dictated by proplsion. Such a boat tends to look like a kayak or canoe.

     
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  4. Dejay
    Joined: Mar 2018
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    Location: Europe

    Dejay Senior Newbie

    • I "want it to be slow" because I want it to be relatively low power with a battery and electric motor. From what I understand even a RIB dinghy needs a bit of power to plane. Battery is either charged from the mothership only, or recharging from solar panels over a day or two.
    • I don't want it purely driven by human power but with something like 250W - 1000W electric motor. I figure a canoe is paddled with maybe 50-100W of human power. That should give a little wiggle room with non optimal shape and weight.
    • I want it be more stable than a canoe so wider and more U shaped.
    • I'd also like to be able to get it on land and use it as a micro camper. So I'd like to have a 60-80cm wide and 2m long flat surface for a mattress to sleep on, and an enclosed top. Instead of double ended like a canoe a transom would be better otherwise it would have to be longer.
    • I was thinking a rubrail with maybe a rubber seal is doing what bumpers do but I want it to "slot in" into the deck like the Ex40 tender.
    So far I figure a hard dinghy hull form, 3.5m long, a bit more rectangular and 1m wide. Would this fit that bill without much compromise? Also how much of a rocker should a dinghy like this have?

    I would redesign the hull with the above in mind.

    I believe the biggest problem with the boat design so far is that it would be too top heavy and unstable. The top would need to be very light weight. Something like 5mm foam and very little fiberglass. And you'd need to use lightweight flexible solar panels. A 340W glass solar panel would be more efficient, last longer and be cheaper but weigh about 15kg.

    ----------------

    I figure I could and maybe should stop here. So if this takes way too long I could stop and start with my cruising boat instead. But if you add the velomobile requirements to all this:
    • I'd like to be able to drive from the boat to a supermarket and having to loading/unloading the groceries only two times instead of three.
    • I'd like to avoid buying an expensive folding e-bike and need storage for it
    • I'd like to anchor somewhere and explore inland from anchor and go camping.
    Yeah I realize now I really don't "need" a velomobile. But I really like the idea.

    If the wheels stay in the water they would add some drag. How much though? I believe that drag could be compensated with a bit more motor power and larger battery and wouldn't really affect the hull speed.

    Thanks for linking the video, it's a beautiful build. After looking at it again, removable wheels would be a solution that shouldn't compromise the usefulness as a tender.
    A 100W pedaled generator would eliminate the chain drivetrain. And the through hulls for the rear wheels aren't needed. This makes the mechanical part of this a bit easier.
    Just an electrical connection to a front wheel hub motor. The pedals really only have to act as a "switch" to turn on the hub motor to fulfill the legal requirements as a pedelec. A single front wheel could also have a mechanism to tilt it upwards or into the boat.
    Steering handles could also work for turning the trolling motor as well as the front wheel. Maybe with a wire rope going all around the boat.

    -------

    Now if you'd want to go a bit further:

    You could design a suspension mechanism to pull the wheels up out of the water without having to get out of the boat. Almost all velomobiles use smaller 20" or 406mm tires and have less ground clearance so you'd need about 200mm lift. Maybe this could be designed to be part of a suspension mechanism. Something like a hinged suspension arm with a spring cylinder that can be unfastened and pulled up.

    After looking a bit more the best solution would be quad bike with dual front wheels and hub motors. Many "tadpole" velomobiles have double front wheel steering with something like double wishbone suspension. I think you could design it so you could also unfasten the shock absorbers and pull the wheels up. Since there is interest right now in DIY electric velomobiles I might find some help for designing this.

    This is again more complex and isn't really easier than removing the wheels but you could do it from inside the boat and you'd get suspension for a smoother ride. This would also allow using really fat tires without a drag penalty.

    Or if you'd want to go really crazy you could use air cylinders for smooth air suspension haha. You'd need an air compressor on board to pressurize the cylinders or decompress them to lift them out of the water. Hmm maybe a small two way air mattress compressor or electric bicycle pump would work for this. Ahh I'm tempted to design it that way. I can see me now, car hopping lowrider style down the boat ramp ;)
     
  5. Rumars
    Joined: Mar 2013
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    Rumars Senior Member

    First thing is to stop thinking of this boat as a tender.
    You want to design an amphibious electric camping boat that can pass as a pedelec, fine do that. Take any hullform you like, add wheels, make it big enough to sleep in and carry your gear. Install the propulsion you like. Stability will not be a problem, look at ocean rowing boats. You want solar panels on top, fine, make a solar canopy out of flexible panels on carbon fibre tubes. Will it be a good velomobile or good boat? It will do both jobs but it will excell at none.
     

  6. clmanges
    Joined: Jul 2008
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    Location: Ohio

    clmanges Senior Member

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