Building an electric propulsion hydroplane?

Discussion in 'Projects & Proposals' started by Piggy, Jul 1, 2019.

  1. Piggy
    Joined: Jul 2019
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    Location: Texas

    Piggy Junior Member

    As the title says, I'm looking into building an electric hydroplane. I've found it kinda hard to find answers to my questions by straight up googling them, so I thought I might try posting on a forum. I'm really new to boats (I decided I wanted to try and make a hydroplane a couple of weeks ago). I'm heading into my freshman year of college, and I want to actually be able to start building this sophomore year. I want this first year to get used to college and plan/find faculty support. Because I'll be building this as a team within the college, funding shouldn't be too much of an issue. I know a little about electric propulsion systems from the time I've spent making quadcopters/RC things (meaning I know I need a motor, ESC, batteries, controls at a basic level).

    My questions:
    1. How in the world do I even start to plan this?
    2. How much power do I need to make this thing go moderately fast? (thinking something like a class A or B stock outboard hydroplane)
    3. Is it possible to get this to go a good speed and have a good range/runtime? (enough for a few laps of a race)
    4. Is it better to run this outboard or inboard (or if that's too subjective, what's the pro/con of each)

    I know there's gonna be things I haven't thought of, so if y'all see gaps in my thinking, please let me know!
     
  2. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    Piggy, welcome to the Forum.

    So, how many people would you like this vessel to carry, one?
    What would you like to do with the vessel and in what conditions?
    Budget?
    Time-frame of build?
    What speed would you like to see out of the boat?
    Max vs cruise?
    And what will come of the boat once finished: sell, rebuild, play, modify, etc?

    Google: design spiral.
     
  3. Piggy
    Joined: Jul 2019
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    Piggy Junior Member

    Thank you for the reply.
    To answer your questions:
    • Made for one person
    • Probably testing in Ann Arbor, MI local ponds, with more usage in the Detroit River/great lakes. This would be taking place late in the traditional school year, so the warmer months of April and May.
    • Budget is pretty loose as of now, but I think $20k is possible, with more available if we can get sponsors.
    • We would have from now to about a year from now to just plan. Starting the build in July or August of 2020 and having it complete by January or February of 2021 would be good so we can test/modify it by the end of the school year.
    • We'd like to see sustainable 45-55 mph speeds. Something similar to this, but electric (A Stock Hydro | American Power Boat Association https://www.apba.org/class-a-stock-hydro.html) would be great.
    • Once the boat is finished it would be used for fun hopefully, and as it's planned to be a university engineering project, the next year would hopefully lead to the construction of a newer, better version. Maybe, with enough time or networking, we can race it against similar boats.

    Do you think this is achievable with an electric system?
    Thanks for all the help!
     
  4. BlueBell
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    BlueBell Ahhhhh...

    Yes.
    You're welcome.
     
  5. Yellowjacket
    Joined: May 2009
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    Yellowjacket Senior Member

    He wants to build a hydro, google APBA hydroplanes and you'll have an idea of what he wants. It's a one place boat that is designed for racing... Let's look at some numbers... A "B" motor is right at 20 hp. The problem is that a "B" class hull weighs around 80 pounds, and the motor weighs around 70 pounds. So you're at about 150 pounds + driver. The whole rig with driver is just over 300 pounds, maybe 350 on the outside. A good B class rig is running well over 50 mph on the straights because it can pack air under it and it's "flying" on the air cushion. If you have a lot more weight you'll neve get the boat to "air out" and ride on that air cushion. Your problem is that you aren't going to get a 20 hp electric motor that doesn't weigh 2oo pounds and that doesn't count the lower unit and tower... If you went with two 12000 rpm starter generators (11.2 kw each) you're going to have more than 100 pounds of motor weight. Then there's the weight of batteries. If you only want to run 3 laps you will eat up the batteries (short life). Batteries want to be discharged at about a 1 hour rate. That is if it's a 20 amp hour battery you want to draw no more than 20 amps out if it if you want reasonable life. You can suck it down in a few minutes, but you'll generate a ton of heat in the battery and you won't get that many cycles out of it. If you size the batteries for a one hour rate the weight goes through the roof. Think about it for a bit, a Tesla car rolling down the highway at 65 mph is drawing about between 15 and 20 kW, and they suck down the battery at a 3 hr rate. That's a bit more power than a B motor but not a lot more. A Tesla battery weighs 1000 pounds. The battery for a one hour rate at 15-20 kW would be 333 pounds. Your propulsion system weight is 450 pounds higher than the B class outboard. You more than doubled the weight of a B class boat and now you have a rig that weighs more than 250 pounds more than a D class rig weight and only 20kW to push it. And with a 650 to 680 pounds you're going to need a bigger hull or you'll never get it on a plane. You can go smaller on battery and give up life, maybe use 150 pounds of battery but you'll never get to 40 mph with it because you really need a "D" class size hull to handle the weight and putting 20 kW ono "D" hull would be lucky to get to 40 mph. If you go down to a 15 minute battery discharge you'll need 75 pounds of battery and that's starting to get into the right size where if you're light you can get it to plane and run, but it won't be that fast with that much weight. You'd be right at 175 pounds for motor and batteries, but you've got 20 kW pushing a D class boat weight, and that's not going to be very fast. High speed boats and aircraft are a bad application for electric power because the steady state power demand is so much higher than an automobile that a big part of the payload gets eaten up by battery weight.. This is one of those "just because you can doesn't mean you should" sort of thing...
     
  6. Piggy
    Joined: Jul 2019
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    Piggy Junior Member

    thank you for the very well reasoned explanation @Yellowjacket. Is it possible to make some kind of electric watercraft that would go a reasonable speed (~45 mph) without going to extreme lengths?
     
  7. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    Piggy,

    I see where YJ is coming from and completely respect his opinion but,
    I am way more optimistic.
    I'm also waiting for more input from other members.

    There are a lot of variables that need to be accounted for,
    and designed for.

    You're going to need a pod in the water with wings, flaperons, elevators, flaps, motor, prop, cooled Lifepo4's, and a canard on the strut.
    There are sensing servos in the Big-Boy R/C world that can control pitch and roll.

    Do you have access to an 80 pound pilot or are you okay with virtual driving, remotely?
    Weight is everything.
     
  8. Piggy
    Joined: Jul 2019
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    Piggy Junior Member

    idk about 80 lbs, but theres every kind of person at university. I'm sure we can find someone close

    Driving remotely could be cool. I'm open to that
     
  9. alan craig
    Joined: Jul 2012
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    alan craig Senior Member

    98mph is what can be done:

    This used a brushed ex-fork lift motor and lithium batteries. You can easily match the power to weight of a petrol/gasoline engine with brushless electric, but you can't achieve the energy to weight of fossil fuel with any battery type. So you can go fast, but not for long.
    electricmotorsport.com have a 15kW motor that weighs 35lbs, and leaves you change from your budget to buy some batteries! I don't know about hydroplanes but am familiar with the electrics used in r/c 'planes; I've built an outboard using r/c model stuff and the leg from a petrol outboard to make a neat 750W electric outboard. I think I would start with a ready made hydro then all your energy and mistakes can be spent on the electrics.
     
  10. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    Thanks Alan, that's inspiring!

    Water cooling on the motor, battery, and controller could be a huge benefit/necessity.

    Oops, I take back all that talk of struts, pods, wings, servos, etc.
    I got it in my mind it was a hydrofoil instead of hydroplane.
    Silly me. Call it the doug lord effect (inside joke).

    The great lakes can be very rough water and could adversely affect your design.
    Obviously, this is a fair weather sailor!

    I knew you'd be into driving remotely.
    That's going to be costly budget wise.
     
  11. Piggy
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    Piggy Junior Member

  12. Yellowjacket
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    Yellowjacket Senior Member

    You could put that motor on "D" class lower unit or a Yamoto racing lower unit and the RPM is about right.

    Then the issue is how much battery you put in, but the motor has about 50 hp and that's about where a "D" Stock motor so that's getting closer.

    If you put in about 150 pounds of battery you can run for about 10 minutes at full power, which is almost one heats worth of running at an APBA race.

    If you look for a "D" class hull you could probably get it over 50 mph with a motor like that and 150 pounds of battery so long as you have a light driver.

    Remember that APBA hydroplanes are not toys and you'd NEVER take one out on the Detroit river or the Great Lakes where there are good size waves and wakes from large pleasure boats. If you dig a sponson at speed you will tear the boat apart. literally. They are serious boats designed to run on smooth water and turn only in one direction. They are run on relatively small sheltered inland lakes and if it gets windy the day is shot and there is no racing. You would be far better to use a racing runabout hull since, while not as fast as a hydro you have a lot more capability to go over wakes and in somewhat rougher water, like a good size inland lake. Even an APBA runabout hull is not suited for places like even the Detroit river, let alone a Great Lake. A class "D" runabout is a serious boat I have one and it's not a toy either. A "D" runabout has a weight limit with driver of 520 pounds and are near 80 mph at the end of a 1/4 mile straight. When I use my boat I have a full Kevlar cut suit, a Snell rated helmet, and Kevlar gloves and socks and a rescue boat. If you're going to go faster than 60 mph in a boat this light you need full safety gear and a rescue boat in the water nearby. And oh yea, a deadman throttle is required as well as a kill switch so that if you get thrown out it shuts everything down. Here is pic of my rig...
    rear 3-4 (2).jpg
     
  13. DCockey
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    DCockey Senior Member

    Piggy, what will be your major at the University of Michigan?
     
  14. Piggy
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    Piggy Junior Member

    I'll be in the College of Engineering, and I'm pretty sure about aerospace engineering, but I'm definitely still open to other options.
     

  15. Piggy
    Joined: Jul 2019
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    Location: Texas

    Piggy Junior Member

    Thank you for the important safety information. I'll definitely keep the boat on smooth water. A runabout might be a better option for what we're looking for, but to be honest, from our *very* inexperienced perspective, the hydroplanes just looked cooler. A class D craft is a little too much for us, and I think a lower power option would be better to start out with. What kind of electric power system should we be looking at for a Class A or B?
     
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