Velomobil tender, micro cruiser camper

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

  1. Dejay
    Joined: Mar 2018
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    Dejay Senior Newbie

    My long term goal is to build a solar powered cruiser boat and as my first boatbuilding project I'd like to build a dingie or tender that could be used as the actual tender for that future boat. So obviously I complicated that simple idea and thought of this :) I'm looking for feedback, ideas, suggestions and criticism. What designs are there with similar hull shapes? This is just a sketch, I haven't done any stability calculations and I need to design this properly with developable surfaces and then either build using plywood stitch and glue or vacuum infusion using a melamine mold.

    Concept: Tender for a cruising boat that can drive from boat to shore, onto land for shopping or exploration of island and back. Also serves as a comfortable micro-camper.

    Length of body: 6m / 20ft (plus front steering wheel)
    Width: 1m / 3.25 ft
    Height of body: 1.2m / 4ft (plus ~0.25m ground clearance)

    Veloboat v38.jpg Veloboat v39.jpg Veloboat v41.jpg Veloboat v41_sketch.jpg

    Main function is a serviceable tender with electric motor and lithium battery to get from an anchored boat to shore and back. Secondary function is a street legal shopping EV. Tertiary function as a fun weekend river canoe and as a micro camper for glamping in the wild.

    A pedelec velomobil that assists the cyclist with a 250W motor up to 25km/h can be build and used in basically any country without permits, license and insurance. With a large enough battery it serves as a useful short range car. The pedal assist can basically be negligent and a single gear for >25kmh would suffice. A motor with enough torque allows the vehicle to be heavier, since top speed is dependent on aerodynamics and roll resistance, not weight. It still needs to conform with regulations for bicycles (turn signals, two independent brake systems, bell, less than 1m wide).

    Single wheel in front and two wheels at the side (delta layout) allows the full width for a bed unlike most tricycle configurations. 28" size wheels with 2" thickness add a little bit of suspension. Spoke-less hub out of composite foam core to provide additional buoyancy. Limited turning radius, little suspension (air filled wheels + seats) but this is meant to go on streets and bike paths and doesn't need to be an off road vehicle for mountain bike trails or a fast racing velomobile.

    An electric trolley motor could either be permanently fixed between the wheels, or as an outboarder that needs to be lowered. Or possibly a keel protecting the propeller. Steering could be done via the spoke-less solid front wheel. How well would a "front tiller" work for for motor boating? Spray?

    Two 340W glass solar panels could be mounted on the roof that supply some power and recharge the vehicle over time. But this would make the boat more top heavy. The roof can be retracted or removed for a more open air feeling.

    Two small folding amas could be fitted to the sides to increase stability and safety offshore. Maybe this is needed with two solar panels on the roof since the better ones are glass and heavy (2 x 18kg).

    Idea: Pedaled through a generator like the Podbike? Fulfills legal requirements as a pedelec bicycle. No chain or transmission needed, no through hull. Mechanics easier but electronics more complex. Overall this would simplify the design and also make it possible to pedal power it as a boat. Maybe you could also extend the rear wheels and make them oversized and buoyant as "amas" or stabilizers?

    Question: How stable would this be without amas? Does it make sense to make it this long? Is a windshield good for visibility? Windshield wipers needed?


    Podbike - Velomobile redefined
    The Sea-Quad: the first amphibious catamaran Youtube
    Plymobil - plywood quad velomobile and boat
    Micro liveabord cruiser - boatdesign.net
     
  2. sharpii2
    Joined: May 2004
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    sharpii2 Senior Member

    If you keep seating low, which appears to be what you have done, stability should not be an issue. Even standing on the bottom should not be a problem in calm conditions.

    Propelling and controlling it on the water may prove interesting.

    I suppose the front wheel can be used as a crude rudder.

    Is this going to be towed or carried by the mother ship?
     
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  3. Dejay
    Joined: Mar 2018
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    Dejay Senior Newbie

    This would be carried in between the ama beams of a multihull similar to the harry proa tender. So it gets pulled up to the level of the deck and sits there. Easy to unload the groceries :)

    If a U shaped 1m wide hull with a mostly flat bottom gives enough stability then I wouldn't need that folding ama concept. I think I'll model this in delftship since it has developable surfaces and stability calculations.

    I guess I should study other dingie or tender plans. How much rocker and freeboard should something like this have to be stable enough to motor to and from the anchorage in a bit of chop. And is it useful for a tender to make it 6m long?
     
  4. sharpii2
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    sharpii2 Senior Member

    One problem I failed to notice is the fore and aft trim. With just one person aboard, much of the total weight will be far forward. This would cause the boat to trim down at the bow. And depending how much the boat itself weighs, this could be by a lot.
     
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  5. trip the light fandango
    Joined: Apr 2018
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    Location: Rhyll Phillip Island Victoria Australia

    trip the light fandango Senior Member

    Some ideas, a way of propelling a grappling iron /anchor[harpoon. ..ha ..sorry] ,then retrieving it could come in handy, I find the transition/emerging from water to land the most {and visually entertaining] compelling issue, delrin skids amidship etc. simple folding small beams and perhaps little inflatable tube amas that inflate via lines /valves from the cabin. A retrievable rudder system could be stored easily with that length. The weight versus complexity and practicality give this project a huge list of problem solving issues. The micro cruisers will have lots of good ideas, a perfect Covid conundrum.
     
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  6. Dejay
    Joined: Mar 2018
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    Dejay Senior Newbie

    Thanks Sharpii, you're right, balancing the trim could be a problem. Normally you would have too much way aft if someone sits all the way back at the tiller and motor, but I figure this would be better than having the trim to the front? Even with 1kWh battery you'd only have 5kg to counter-balance. I think delftship can tell me what trim I'd end up with.

    The podbike paper also mentioned in regards to tricycles how the center of gravity shouldn't be too close to the single wheel or the tilt line. So this is also a factor for the velomobil driving, sitting in the middle would be better but that affects visibility.
     
    Last edited: May 3, 2020
  7. Dejay
    Joined: Mar 2018
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    Dejay Senior Newbie

    Haha yeah maybe an anchor that you can throw up a slippery beach to pull yourself up might be a good idea. I'm hoping for most beaches thicker 2" wheels would be enough to just drive on. Big wheels are not optimal for drag in air or water but they'd provide a little bit of suspension, since I don't want to complicate this by having a real suspension.

    In the first picture I imagined some small folding amas that would "slot into" the body and would fold out using carbon rods. Two lines that form a cross between the arms would enable you to unfold them from inside and then fix them by tensioning both lines. But the amas would only be about 5cm thick, 45cm tall and 2m long. So maybe 22 liters buoyancy? Still it could provide some stability.
    I've also considered if you could extend the rear wheels outwards at sea. If the wheels are thick enough and the hub is foam core construction it would provide some stability. Please don't laugh haha.

    About the rudder I'm not sure. Maybe you should make the electric trolling motor steerable. But I was hoping the front wheel would work as a rudder even though that's quite atypical. Maybe this would lead to a lot of spray. And it could also be less stable if the front of the boat steers instead of the back and introduce a rolling motion outwards.

    I hope making some compromises won't make this design too complex but maybe I'm kidding myself. Essentially it's just a canoe with a normal bicycle front fork for steering with a wheel with hub motor and two freely spinning wheels in the middle. And brakes. And blinkers.

    The pedal generator could theoretically be just "pro forma" to fulfill the legal requirements of only moving when pedaled. Or you'd connect it to a battery charger and use some arduino electronics to control the load on the generator and trigger the wheel motor.
     
  8. trip the light fandango
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    Location: Rhyll Phillip Island Victoria Australia

    trip the light fandango Senior Member

    An "electric trolling motor that's steerable" could solve that problem.. Trailing a line from the main boat [that doesn't get caught in the prop] to shore could help. I can't help thinking a foldable electric bike or trike with a demountable motor [for the winch etc]is easiest, even if you folded up the dinghy and took it with you...
    Still your approach is far more innovative.
     
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  9. gonzo
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    gonzo Senior Member

    Top speed is dependent on weight. On level roads, increased weight increases friction resistance at the wheels. On uphill roads, it increases friction resistance and the energy input necessary to compensate for increased potential energy stored. On downhill roads, it increases friction resistance and the potential energy gets released causing acceleration.
     
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  10. antonkov
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    antonkov Junior Member

    In my experience, something that originally comes as a simple idea once being implemented becomes an increasingly complex project with a ton of details and micro problems to solve.
    If it looks complex on the idea stage, then the likelihood of it been completed is really slim.

    You can always throw ever-increasing resources (mainly time) at it and drive it to the end, but your time is limited by the upcoming bigger project.

    If the final goal is a solar multihull made from developed panels, then I would say a good candidate for the proof of concept would be something very simple focusing on fabrication and on solar power system. Something like a simple dinghy with electric motor and folding ebike than can take the dinghy's battery. That alone will get you enough exposure to what you are going to face on the mothership project.
    In your amphibious tender concept you will need to solve a number of problems that aren't very relevant to the final goal.

    I went the very same route and started on a dinghy before moving on to the cat. It was a great learning curve, the main takeaway was the estimated/real effort coefficient.
     

    Attached Files:

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  11. Squidly-Diddly
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    Squidly-Diddly Senior Member

    I'm a fan of the general concept....an civilian amphib that is 80/20 boat/car, mostly because getting pushed out of comfort zone on water is not as easy to avoid as simply pulling off or slowing down and maybe blocking a little traffic and even a ticket or tow on land or road.

    First thing I'd do is add streamlining fenders. The fenders could be hollow and flood to create water ballast when stopped or slow. If you plan on electric and battery, include a nice built in place to carry a portable generator of indeterminate size.

    Haven't seen any boats of your size with full car-type enclosure, no doubt due to drowning danger when things go wrong. If you want a cover for rain, consider a skin-on-frame boat turned upside down that would also serve as additional boat.
     
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  12. Rumars
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    Rumars Senior Member

    I hate to rain on your parade but what you draw there is unusable. Basically it's too long.
    1. No dinghy dock will accept you at 6m+.
    2. On land you are the size of a standard van. Using bikepaths is impossible, you are limited to normal roads.
    3. To get out onto a beach you need soft wide tires. Cycling with such wheels is very difficult even with electric assist. Normal wheels would limit you to paved launching ramps.
    4. Bikes are only usefull for shopping and cargo in developed regions of the world. On an island with less improved roads the mountain bike can be used for exploration if you have the guts to share the road with the normal traffic there. But reality is that bikes normally stay on board unless you are in europe or the americas.

    If you want to shop by bike other then with the normal system of folding bike with sadddle bags, take a cargo bike (Bullitt, 2,45m long) and put it on a catamaran dinghy with an open bow (Takacat and similar) 3-3,5m long. Then you simply drive to the beach, lower the forward ramp and drive the bike of. If you sail tidal areas you fit dinghy wheels to the dinghy.
     
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  13. Dejay
    Joined: Mar 2018
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    Dejay Senior Newbie

    Thanks everybody for the comments. I tend to get swept up with cool idea and I really like this one, but I should be more realistic. I love the idea of taking off from my house in this thing (without needing a trailer) and driving to and down a nearby river or to the Schlei. And being able to camp in it. But it's possible I'd enjoy the reality of it less.

    I guess my main requirements are really to gain:
    1) experience building using vacuum infusion
    2) a serviceable dinghy
    3) experience designing a boat
    4) experience with battery, electric and solar power systems.
    5) some experience on the water with a motorboat

    I need to think a bit and decide to either: Scrub this idea altogether and build something like a smaller T40 harry proa catamaran tender. Or to design this to be a shorter and more usable velomoboat but build and finish the boat part first and then being able to stop and "upgrade to a velomobile later".
     
    Last edited: May 3, 2020
  14. Dejay
    Joined: Mar 2018
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    Dejay Senior Newbie

    Thanks, you comment prompted me to do actually some simple weight calculations haha. And things add up fast with such a long a fully enclosed boat. If I'd make it 4.5m long instead and use 1cm foam core and 600gsmit should be something like 22m² hull surface and about 82kg for the hull.

    I guess I should get into calculation for rolling resistance and the like, but 250W is probably 5 times what I as a lazy cyclist would produce. So I believe it should at least be good enough up to 25 km/h.
     

  15. Dejay
    Joined: Mar 2018
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    Dejay Senior Newbie

    Thanks point 1) is crucial I guess. Unfortunately I lack experience. After looking at some more dinghies they typically seem to be 3m long and between 1.2 and 1.5m wide. Do you think 4.5m would still be too long for most dinghy docks? The body itself doesn't really have to be longer than 3m to allow sleeping space but you need about 0.8m for the front wheel and some extra space for your gear would be good.

    2) Using only normal roads and bike paths would be ok. Long term I do want to cruise mostly along the coasts and rivers of Europe, UK and the Mediterranean.

    3) For a beach you could always get out and push if you can't get out. I was thinking 2" or 5cm wide tires which should help. But yeah something like a 3.5m catamaran dinghy with an e-bike on the bow is of course the more sensible option.

    For traction on a beach a quadricycle with two front driven wheels would be better. More complexity but also shorter, maybe less spray and more stability as a velomobile. Suspension could also increase traction. But using a standard bicycle fork is much simpler.

    4) Probably the bigger question than driving up a beach might be getting up in a harbor without a launching ramp. How common is that? It would be silly if at a lot of the places I anchor I can't get on land with this.
     
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