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Thread: Displacement designs for solar electric river cruiser, 20 - 25 feet

  1. #1
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    Default Displacement designs for solar electric river cruiser, 20 - 25 feet

    For my upcoming retirement in a year or two I'm hoping to have the space and time to build another boat. The plan is a cruising boat for two, spending up to a week at a time. Power to be electric outboard with battery and enough solar to run 30 to 40 miles in a summer day. Use would be protected waters, mainly my local Sacramento Delta but trailerable up to the Salish Sea. I'm basing the boat on two working examples, one too big and one too small.

    The too big example is Wayward Sun, the Sam Devlin designed boat that just made a solar trip up the inside passage. Specs are:

    - LOA 29 feet
    - Beam 8 feet
    - Displacement 3600 lb
    - Powered by 4 kW Torqeedo pod with 10 kWh LiPO battery and 1440 W solar roof
    - Claimed cruising speed 4.5 to 5 kts




    The too small example is my own Welsford Walkabout, with solar electric added last year. Specs:

    - LOA 18 feet
    - Beam 5 feet
    - Cruising displacement 600 to 700 lb
    - Powered by 250 W EP carry outboard with 0.6 kWh LiPO battery and 170 W solar panel
    - Cruising speed 3.5 to 4 kts, range on solar only 30+ miles on a sunny summer day




    The new boat preliminary specs are something like this:

    - LOA 22 feet (20 to 25)
    - Beam 6 to 7 feet
    - Hull weight ~1000 lb, cruising displacement ~2000 lb
    - Electric outboard 1 to 3 kW, battery 3 to 5 kWh, solar panels 1 kW
    - Cruising speed 4 kts

    The hull shape should be designed for the low power displacement speed. The electric components will be a significant cost, so optimizing the hull saves on the propulsion. My Walkabout works well since it is really a big rowing boat, now I need an even bigger rowing hull.

    I'd like an enclosed cabin with generous V-berth for sleeping, sitting headroom, and a place to stow and use a porta-potti. The solar panels would be on a roof above the cockpit, around 12 feet by 6 feet of surface needed. Side seats in the cockpit. Roll down fabric sides would be available to enclose it. The helm station should be at the front of the cockpit, with steering by a wheel with rope line and minimal instruments. Cooking, eating and cleaning could be on a simple stowable table in the cockpit.

    I have discussed this with several designers and in the next few posts plan to summarize what I've learned, but please jump in if you have any ideas.

    Rick Thompson

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    Glad to see this thread! I have thoughts of course. My first one being around the displacement and power numbers for the boat you are envisioning. As a comparison, take Tad's Timbercoast 22 (designed for and plans available from Bartender Boats):

    https://bartenderboats.com/timbercoast-22/

    Inboard instead of outboard, but otherwise she is pretty close to your specs. 22' LOA and 7'6" beam. Designed for low power and hull-speed cruising. But she has a displacement of 3600lbs. There is one being built in France for electric power and the builder is using two 4.5Kw motors.

    I expect that your displacement goals could be met with a very narrow, shallow hull but I wonder if a boat like that would make a comfortable cruiser? Also, it seems like you are likely to end up with something like Gib Etheridge's strip planked double ender:

    http://forum.woodenboat.com/showthre...y-build/page14

    I wonder if his design could be scaled down to the displacement you are looking for? And finally, on the subject of scaled up row boats, the Energy 48 design might be worth a look as an example:

    https://forbesyachts.com/blog/the-energy-48

    (tons of info on the design online). It's basically a scaled up Alden Ocean Shell. I've always thought that hull form would make an ideal electric cruiser.
    - Chris

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    Also… if I was designing a solar cruiser from scratch I would make it a motorsailer because why not use the wind when you can? And regen too.

    ETA: Something like a stretched version of Heather might be suitable:




    Designed by Tim Nolan (http://timnolanmarinedesign.com/port...ther-1/heather), she's 16' as-built. No idea of the displacement but I'd bet a 22' version would be in the ballpark. I think she was being converted to electric power a while back but then she was sold so I don't know where that project ended up. Marty Loken, who was doing the conversion, is well known in the PNW though. He would be a good source of info.
    Last edited by cstevens; 09-16-2021 at 03:29 PM.
    - Chris

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    Thanks for diving in Chris!

    So let's take your lead and start with Tad Roberts. I contacted him regarding the design from his catalog which first caught my attention: the Power Pogy 19' 6" (and Alex's thread on the sailing version CoPogy 18). Specs for the Power Pogy are LOA 19' 6", beam 7' 6", cruising displacement 2100 lb. Intended power is much higher than I will have available, 8-25 hp outboard. I do not think any have been built yet, but the design has the salty looks I would like:



    Tad responded, first through Facebook and then by email and sketch, with a concept for a lighter boat based on Wylie Blanchet's cruiser Caprice (from The Curve of Time). The Caprice was 25' by 6.5' and powered by a small inboard. Tad proposed a 22' boat with plumb bow and transom to maximize waterline, and a canoe form hull. He has a lot of work on his books and we have not gone farther with the concept, but a new version Caprice would be fantastic. Might name it Capri-Sun . This is the Caprice:


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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    Gib's big dory is amazing, but I am not Gib and would not be able to pull off such a build. A dory does not make the best use of the waterline hull speed, I think I need to follow Tad's advice and go with long and light.

    The Energy 48 I had not seen before, it is the right idea. Scaling such a design down to 22 feet would be the work of a skilled designer.

    Heather looks like a number of designs I keep running across, a heavy inboard displacement boat. I just do not know how to convert it to a lighter hull without the engine inboard. While adding a sail is always tempting, I would never use it on the winding sloughs of the Delta.

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    Quote Originally Posted by rgthom View Post
    Gib's big dory is amazing, but I am not Gib and would not be able to pull off such a build. A dory does not make the best use of the waterline hull speed, I think I need to follow Tad's advice and go with long and light.

    The Energy 48 I had not seen before, it is the right idea. Scaling such a design down to 22 feet would be the work of a skilled designer.

    Heather looks like a number of designs I keep running across, a heavy inboard displacement boat. I just do not know how to convert it to a lighter hull without the engine inboard. While adding a sail is always tempting, I would never use it on the winding sloughs of the Delta.
    That all makes sense. I'd just note that I'm pretty sure Heather is quite light. She's basically a strip planked canoe body hull. I'd bet that you could do something similar with a double ended hull and an outboard in a well. But a solar Caprice seems like a great idea too. And while I love double enders I have to acknowledge that they don't use space very efficiently, and that gets even worse when you add a motor well.
    - Chris

    Any single boat project will always expand to encompass the set of all possible boat projects.

    Life is short. Go boating now!

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    Also just to throw another idea into the mix, for river cruising what about something like a shortened narrowboat? Here's a mention of an electric powered shortened narrowboat:

    http://jhalfie.blogspot.com/2017/08/...arrowboat.html

    I expect that the CA Delta weather and currents are a bit more challenging than the Thames and its tributaries and canals, but even so the basic format would work well for a solar cruiser as it maximizes roof area and interior space in a narrow width.
    - Chris

    Any single boat project will always expand to encompass the set of all possible boat projects.

    Life is short. Go boating now!

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    A narrowboat on the Delta. That would fun, but I am concerned about windage. The Delta mostly has little fetch for any waves, but it is windy in the summer. One of the risks of a low power boat is getting hit by a gust and not having enough power to turn out of it before hitting the rocky lee shore 100 yards away.

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    Catamarans are showing up as new solar electric designs, they have two advantages: The long narrow hulls are easily driven while the bridge area provides a lot of surface for solar panels. Plans for this EC24 are available at boatbuildercentral, it is 24 feet LOA and 2000 lbs displacement: https://www.boatbuildercentral.com/S...EC24_STUDY.pdf




    Richard Woods has a series of power cats, his Skoota designs. The Skoota 18 could be trailered at 8 foot beam, the bigger models have a more complicated folding system or need special transport. The hulls of all the power models are semi-displacement, efficient for small gas outboards but not optimal for low power electric. Richard advised it might be possible to use sailing boat hull shapes on a powerboat, but he is not very excited about electric propulsion as of yet. Skoota 18:




    Bernd Kohler has catamaran designs that could work, his ECO 55 has been modified for solar electric by at least one builder.




    My problem with all the catamarans is - I just don't like the appearance of any of them. If I'm going to put the effort into building I'd like a salty boat that is a pleasure to look back at on the dock. Unless someone comes up with a great looking catamaran design I am crossing them off the list.

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    Dude.

    I need to electrify the Sneakeasy...

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    Unless someone comes up with a great looking catamaran design I am crossing them off the list.
    Hickman Sea Sled.

    - Chris

    Any single boat project will always expand to encompass the set of all possible boat projects.

    Life is short. Go boating now!

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    Quote Originally Posted by amish rob View Post
    Dude.

    I need to electrify the Sneakeasy...
    That would work! Can I put a cabin on it ?

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    Quote Originally Posted by cstevens View Post
    Hickman Sea Sled.

    OK that looks pretty good. Not exactly a 4 kt displacement hull, but I stand corrected!

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    Classic-looking solar catamaran concept, preliminary study:



    22' x 8' 6". Glued plywood lap. Deck and interior plans still under development. I'm envisioning two "EP Carry 1500" motors (to be developed) in wells for 3kW total. A slide-out extension to the hard top for additional solar panel capacity. V-berth in the cuddy with sitting headroom under the trunk.
    - Chris

    Any single boat project will always expand to encompass the set of all possible boat projects.

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    Default

    That looks like Joe Grez' new boat. I am definitely interested in his new motors, but he says it may be a few years development.
    Last edited by rgthom; 09-17-2021 at 03:46 PM.

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    Quote Originally Posted by rgthom View Post
    That would work! Can I put a cabin on it ?
    Crawling into the snoot is scary, but a person could sleep in there.

    We have just had so many other priorities and otherwise happen to even get her running, but she safely stored and waiting a new life.
    May as well electrify her as anything, eh? Maybe with a foam core, ply wood hardtop covers in solar panels wo could make it work?

    Your experience and reports have given me great hope.

    I am very excited to see where this goes, and what you end up with!

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    Hi,

    Paul Gartside has some Steam/Electric Launches:

    His 19 ft Steam Pinnace, Design #132 might be a match ...

    https://store.gartsideboats.com/collections/steam-launches

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    Nigel Irens Romilly 23 would be a good base and meets your length/ beam/ displacement preference.




    There was a strip plank version with Ed Burnett.

    This one is cold molded...





    She's quite slender. 1.1ton. 23ft.

    The people making the grp version also sell as a river launch and they've organised an electric drive system which would give you the bones to do similar. Prop is in front of the rudder too which I prefer.


    Ed's no longer with us, but his father might be able to sought you out the strip plans or Nigel.





    integrated-battery-assist.html
    Last edited by Edward Pearson; 09-17-2021 at 06:35 AM.

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    Quote Originally Posted by Edward Pearson View Post
    Nigel Irens Romilly 23 would be a good base and meets your length/ beam/ displacement preference.




    There was a strip plank version with Ed Burnett.

    This one is cold molded...





    She's quite slender. 1.1ton. 23ft.
    Where is this boat? Owner?

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    She was built in Greece by Thomas Huber and is called Anna Sophia. Don't know if he's got a blog anywhere. I think I saw the launch on here some time ago. Triple layer mahogany.


    http://www.roxane-romilly.co.uk/romi...molded-romilly

    http://www.roxane-romilly.co.uk/romi...milly-launched
    Last edited by Edward Pearson; 09-17-2021 at 07:37 AM.

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    I think Thomas is 'Zauberberg' on the WBF.

    Here she is in action in Greece...




    http://forum.woodenboat.com/showthre...on-our-Romilly

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    Quote Originally Posted by rgthom View Post
    My problem with all the catamarans is - I just don't like the appearance of any of them. If I'm going to put the effort into building I'd like a salty boat that is a pleasure to look back at on the dock. Unless someone comes up with a great looking catamaran design I am crossing them off the list.
    I have to agree, I don't think there is single multihull aesthetic that I am fully on board with apart from maybe some Newick wing ama trimarans and a few Woody Brown and Joe Quigg cats.

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    nelson zimmer 21' utility
    originally intended to be power by 6hp hot bulb semi diesel engine





    Simpler is better, except when complicated looks really cool.

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    harry bryan's handy billy

    Simpler is better, except when complicated looks really cool.

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    All the launch hull designs look great. I especially like the idea of a solar Handy Billy. The challenge is designing a good looking hard top that will hold a large enough solar array and not add too much windage. That’s one advantage of a catamaran design - more surface area for the length.
    - Chris

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    Ted Moores at Bear Mountain boats built Sparks (30ft/ strip plank) 10 years ago for himself with an electric/ diesel/ generator/ solar. Designed by Steve Killing he might have a smaller one if you like the look.

    Last edited by Edward Pearson; 09-17-2021 at 09:31 AM.

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    Another catamaran design (sorry Rick, I know it's not the direction you are thinking, but they just make a ton of sense for solar cruising, for all the reasons you noted above).



    I think it's a "Crab Claw" from Shell Boats. Designed as a sailboat but this one appears to be power only. 18', but I expect that it's possible to stretch it to 22'. Not traditional looking, true, but it I like it even so.
    - Chris

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    I've nothing to add apart from being very intrigued by the possibilities. Next year I will be trading my gas car for a VW ID.4 EV, and will not have any more gas engines in my life. Electric boating is very appealing.
    There's the plan, then there's what actually happens.

    Ben Sebens, RN

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    16' W. Simmons Mattinicus double ender ​Matty

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    Or... a shanty boat like Escargot, plans available from WB?



    (Photo from Small Boats Monthly https://smallboatsmonthly.com/articl...canal-cruiser/)

    Maybe not suitable for the winds in the Delta, but I wonder if that's going to be an issue with any design given the need for an extended hard top on a narrow, light boat? Cats and shanty boats don't have quite the same "salty" characteristics of all the launch and sailboat hull designs, but they do provide the maximum amount of living space and solar panel area for a given length and displacement. I love the narrow monohuil designs to look at. But waking up after a night at anchor at the edge of a salt marsh and having room to stand up, walk around, make a cup of coffee without disturbing your significant other, and sit inside with the stove going while watching the wildlife, is a nice thing as well.
    - Chris

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    Last edited by Paul Pless; 09-17-2021 at 11:59 AM.
    Simpler is better, except when complicated looks really cool.

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    Quote Originally Posted by Paul Pless View Post
    harry bryan's handy billy

    Between the cabin top and engine cover aft there's a fair amount of surface area for a solar array. Good looking boat too.

    How firm is the desire to be outboard powered? I've been poking around the Thunderstruck website (https://www.thunderstruck-ev.com/) for possibly powering project I have in mind. Might a 10kw motor running an appropriately sized prop be more efficient than an outboard? An honest question, I'm just starting to scratch the surface in my research on electric powered of boats.
    Steve

    If you would have a good boat, be a good guy when you build her - honest, careful, patient, strong.
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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    Solar panel area is perhaps the most significant design challenge in a small solar-powered cruising boat. A practical 1Kw array requires around 80sqft, or around 8’ x 10’. Commercially available, light weight panel sizes are also a factor. A typical 100W panel is around 4' x 2', which works well with the 8' x 10' area, but narrow boats can't easily carry an 8' wide array, meaning that you end up with more like 4' x 20' or 6' x 14' depending on how they are arranged. Renogy has a 175W flexible panel (https://www.renogy.com/175-watt-12-v...e-solar-panel/) that is ~5' x ~2' which would allow for an approximately 5' x 13' array.

    All the narrow monohulls look great in the photos. The challenge is to design a good looking hard top of sufficient size to support the solar array, while also balancing enough cabin area for a v-berth with sitting headroom and some standing headroom somewhere as well.
    - Chris

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    How important is running a max size solar array rather than having a deployable array that can be used as needed with whatever size permanent array lends itself to the design? I suppose you'd need to work it out based on whatever motor/battery/hull/etc, but depending on how the numbers shake out it might be a worthwhile compromise. Under power you'd be draining the battery more slowly. If you start the day with a full charge and put out the deployables when/if you're stopped, it might be plenty in fair weather.

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    Thank you everyone! I was holding off posting here for fear of being overwhelmed by good advice, which I am. Let me try to narrow this down and address some of the issues:

    1) Inboard or outboard.
    I am planning to use an outboard. The electric outboards around a kW are light weight and easy to manage. They do not take up interior space, no shaft hole to leak, easy to remove for repairs, no rudder needed. One of the problems in the Delta is weeds clogging the prop, they are easy to remove from a tilting outboard. I am happy with the high efficiency 250 W EP Carry on the Walkabout. There is an option to boost that to 500 W, maybe use two to get 1000 W, and the company has a new 1500 W version in the works that might be ready when I am. Planning for an outboard keeps the options flexible.

    2) Solar panel area.
    The Sunpower 170 W flex panel I am using is 45" by 32" including connector dead space, and provides enough power to run the 250 W rated motor at 150 to 200 W for most of the day (smoothed by the battery). If I scale up the motor to 1000 W (4X) and plan for 1000 W of solar (6X) I think it should provide similar speed and range. Six of the same panels would fit on a roof 6 feet wide by 12 feet long.

    3) Catamarans
    Chris - I appreciate your outside the box thinking, but the big reason to go for a cat is to get enough solar panel area. Per the estimate above, for my planned relatively low power, I should have enough roof area on a 22 foot monohull to support the needed panels. Escargot is cool too, but my wife did not like the little box shape.

    4) Construction method
    The only boat I have built so far is the Walkabout, an epoxy glued plywood lap construction that needed no lofting. I am willing to learn some new techniques, but should probably stick to a similar method. I have to say that strip planking has the least appeal to me, it looks like a lot of gluing to wind up with a hull that has to be fiberglassed inside and out as well. Cold molding looks the way to build very light and strong, but it would be all new to me. I like the looks of lapstrake, but not necessary.

    5) Steam launches
    Steam launch designs are an existing class with hulls optimized for the low speeds of electric, so I am looking at them. Gartside, and Selway Fisher, have a number of designs. They are generally set up as inboards, and usually heavier than I am thinking. I do not see many built examples either, making it hard to picture the finished boat.

    6) Sailboat designs as solar electric
    This may make sense, especially non-planing sailboats, but are the hulls optimized for this application or does the need to mount masts and resist heeling change things? The Romilly looks slippery, but I would have to change the transom area to take an outboard instead of the rudder.

    I like the designs posted so far, many very attractive boats, but the Handy Billy seems the best match to my goals and abilities. I see there is a 21 ' by 5' 10" version at 1300 lb. Construction is batten seam cedar over oak, not plywood. I would guess cedar may be hard to source and fairly expensive, but it is appealing to work with real wood.

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    Default Re: Displacement designs for solar electric river cruiser, 20 - 25 feet

    Quote Originally Posted by offbelayknife View Post
    How important is running a max size solar array rather than having a deployable array that can be used as needed with whatever size permanent array lends itself to the design? I suppose you'd need to work it out based on whatever motor/battery/hull/etc, but depending on how the numbers shake out it might be a worthwhile compromise. Under power you'd be draining the battery more slowly. If you start the day with a full charge and put out the deployables when/if you're stopped, it might be plenty in fair weather.
    A stowable array might work but there are challenges there as well. The constraints here are size of the array, power used underway and sunlight hours. And part of the problem is that a 1kW array is only nominally 1kW, and that's only under ideal conditions. To make the math easy let's assume 1kWh power usage underway. That's a 1:1 ratio of run time to recharge time under ideal conditions, but in reality I'll bet it's more like 1:1.5 or 1:2 or more. So for five hours of run time you might need 7-12 hours of sunlight to recharge.

    This article has some really useful data:

    https://www.electricpaddle.com/solar...g-epcarry.html

    And in particular this graph:



    The boat used in that cruise had a 200W array. But actual power generated topped out at 180W and that was only at mid day in full sun. Even just a little haze cuts the efficiency of the array way down. So the trade off is either reduced power underway to balance out power used with power coming from the solar array, or more time sitting while the batteries recharge. And any reduction in the size of the array affects those numbers.
    - Chris

    Any single boat project will always expand to encompass the set of all possible boat projects.

    Life is short. Go boating now!

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