Self-powered live well for kayak (hobie in particular)

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trolling dirty
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Self-powered live well for kayak (hobie in particular)

Post by trolling dirty »

Since we are in the quiet BTB season here, I was wondering if some of you guys could help me out with an idea I wanted to try putting together for my Hobie Outback. I'm prepared to prototype a live well for the back compartment of my Outback that would work sufficiently with a 2 knot forward motion.

The calculations seem to show that this should be possible. But of course I may not be accounting for everything.

The idea is basically to take a squarish plastic container, drill two holes in the bottom that would align with the existing scup holes behind the seat, insert a 3/4" pvc and check valve into one side, and a capped 3/4" pvc of desired height (several inches for desired water level, with small holes drilled on the top). I would seal the space between the plastic container and the pvc inserts with some kind of epoxy. I would give sufficient length on both inlet/outlet pvc's to reach down through the scup holes and barely extrude from the bottom. Then I would just fasten a forward facing elbow beneath the kayak on the check valve side and backward facing elbow beneath the kayak on the other side.

The elbows would fit nicely underneath the hobie: They would be well above the lowest part of the kayak and they should be unobstructed by the hull and thus receive laminer flow of similar speed to the kayak's velocity.

I imagine just putting the well into the kayak and the fastening the elbows underneath in preparation for launch. My only possible doubts are: Are my calculations correct and if so, will enough water be circulating through to maintain decent oxygen level in the tank at typical speeds? If so, why can't I find anyone doing this without a battery-power addition?

Keep in mind that the tank will be slightly above the water level. Ideally, Hobie would have a live tank built in the hull that was below the water level.

Anyway, I'd love to hear everyone's thoughts. I am prepared to order some materials but I would like some feedback before doing so.
mwatson71
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Re: Self-powered live well for kayak (hobie in particular)

Post by mwatson71 »

Sounds cool but I have no idea whether it would work. There are some pretty bright people on this board so hopefully you will get some good feedback.
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Fishtolive
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Re: Self-powered live well for kayak (hobie in particular)

Post by Fishtolive »

That is one good idea but also you can build a small hydraulic ram pump which it can continuously run to pump the water uphill without requiring the kayak movement.
The hydraulic ram pump is a very old technology that farmer has used to pump water uphill without requiring any external power or electricity
trolling dirty
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Re: Self-powered live well for kayak (hobie in particular)

Post by trolling dirty »

mwatson71: I agree. I still lurk on this board even though I no longer live in the area. Lots of bright minds here and that's why I made the effort to post here!

fishtolive: Thanks for the suggestion. I never heard of this until you mentioned it and I did some research. It's a very cool concept. If I'm not mistaken though, it seems as though a hydraulic ram pump would be good if the kayak was continuously moving. If the kayak stops, the pump needs to be "started up" again by holding the waste water valve open when kayak movement restarts. I am hoping that the extra head this pump provides will be unnecessary (fingers crossed). This seems ideal if one has access to a continuous flow source, like a stream on someone's farm.
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Kirk B.
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Re: Self-powered live well for kayak (hobie in particular)

Post by Kirk B. »

This is a fun project to think about!
It should be easy enough to test on any scupper, just to see how much head is generated at normal speeds. Set up a pipe and elbow, and see what flow is generated at paddling speed.
Keep in mind that some head will go towards keeping the check valve open.
My first thought was to have the inlet above your drilled waste discharge, without a check valve, providing you can generate enough head.
On the pro side to having an inline check, you could probably generate flow off of simple wave action.

Let us know what you discover.

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Jack Trades
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Re: Self-powered live well for kayak (hobie in particular)

Post by Jack Trades »

Great Idea! Check out the Stealth kayaks live well with the forward and reverse facing inlets/outlets that cycle fresh water while in motion. Love their boats but never owned one. Professor Salt on this forum or Rokkit Kit on youtube should be able to connect you, as both sport Stealth yaks at one time I believe.
trolling dirty
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Re: Self-powered live well for kayak (hobie in particular)

Post by trolling dirty »

Kirk B. - This was my original plan. But after seeing on youtube how to make a cheap and easy low-pressure DIY check valve, I'm just gonna go ahead and prototype the completed product. The check valve is just some PVC parts, a gasket, and an acrylic ball that is "trapped" in a little cage that is pushed out of the way when a little bit of pressure is produced. Any back pressure and the ball sits back down on the gasket and seals the hole (seal doesn't even have to be perfect but I think it easily could be). Your point is exactly right: with a check valve you don't have a velocity minimum that needs to be achieved for intake, and instead can get a trickle at very low speeds.

Jack Trades - The Stealth Kayak that I see in Prof. Salt's and Rokkit Kit's youtubes is exactly what inspired me to do this. Stealth had such a good idea. I have been so discouraged to use my sabiki rod for offshore trips just because of the pain of keeping live bait. Stealth's design is ideal because its built into the hull and sits below the water line. Therefore head doesn't need to be produced at all. I think this DIY design will work just as well except the fact that there will be less circulation, which just means that less bait could be stored at once.
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Re: Self-powered live well for kayak (hobie in particular)

Post by SWFinatic »

Late to the party but in case you're still contemplating the design here's a live well I made a while back. I made it for my wife's 2020 Outback since she prefers to fish with live shrimp/mullet. It easily holds a quart of live shrimp and keeps them alive in August with zero issues and doesn't require to be moving forward to work. Just have to be in the water.

I started with a Coleman 16 quart cooler as this best fit the tank well in the Outback. Used a Tsunami T-550 12 volt pump. The primer bulb is from a fuel line kit I bought at Academy. Ordered a plastic storage box from Amazon that houses the battery, fuse and push button on/off switch. Went with a small lithium battery. I installed a valve inside the tank but this was only to adjust the flow. Once I got the flow rate set there's no need to adjust this valve. Then plumbed in a drain line. The cork in the bottom of the drain line is so I can fill up the tank if I want to cast net some bait before I get to where I want to launch and fish. This way the water won't drain out.

I set the live well in the rear tank well of the kayak after the kayak is in the water. Turn on the pump and manually pump the primer bulb until water starts filling the live well. Once the pump is primed and water is pumping into the live well I can turn the switch on and off and don't have to use the primer bulb anymore as long as the bottom of the suction tube stays in the water. It will run the pump continuous for 4 hours. I was a little worried 4 hours wouldn't be enough so I ordered a second battery as back up but never used it. Ended up just manually turning off the pump about every half hour or so for about 5-10 minutes and that lasted through a solid half day trip which was plenty.

I probably have about $170 in materials in it at least this was when I built it over a year ago. I'm sure this build exact would cost a tad more now.

If you're interested let me know and I'll go into more details with parts.
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impulse
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Re: Self-powered live well for kayak (hobie in particular)

Post by impulse »

Not sure you can self power it at 2 mph. That's around 3' per second. G= 32' /sec2, so that 3' per second will peter out in 1/10 of a second, during which it starts out at 3' per second and ends up at zero ft/second, averaging maybe 1.5 ft/second. Meaning it will travel 1.5 ft/sec X 1/10 second, or about 0.15 feet= 1.8". That's not very high.

Another way to look at it is the velocity (V) of anything dropped from height (H) is sqrt(2GH) V=sqrt(2GH). With G =32'/sec2, that's V=sqrt(64H) or V=8xsqrt(H) Using 3ft/sec for V, 3=8 x sqrt(H). or 3/8 = sqrt(H) squaring both sides gives you a height of 9/64 of a foot, = 1.6875 inches.

That's how high you can lift water with 2MPH, coming at it from 2 different "formulas"

I stand to be corrected, but I'm not too optimistic that it can be self powered at that speed. I'd look for a cheapo bilge pump...

Just a note... If you can get 10 mph (15ft/sec), the 2nd equation becomes 15 = 8 x sqrt(H) and H = 225/64 = almost 4'. That's doable if your hoses are big enough to avoid restrictions. So if ya got a jon boat with a putt-putt on it...
trolling dirty
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Re: Self-powered live well for kayak (hobie in particular)

Post by trolling dirty »

Thanks for your post Impulse. I reran the calcs with Bernoulli's equation and got your 1.6875". No bueno. Good thing I posted here and got feedback. Must've messed up unit conversions the first time around. I got a reasonable order of magnitude then so I just figured we were all good lol.

I might still just finish it and add a little pump like SWFinatic (thanks for your post as well). I will give it a whirl before I add the pump just for the hell of it. My sister owns a laser cutter for her work so I have the privelege of making a perfectly-fitting container behind the seat.
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Fishtolive
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Re: Self-powered live well for kayak (hobie in particular)

Post by Fishtolive »

Hey, just found this device on internet … rather interesting and it can fit the purpose.
Website: foceyse.com
Solar powered hummingbird fountain.
The diameter is about 5”.

Still don’t know if the internal components will last in saltwater or not.
It needs to touch the seawater level before it can pump up……
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dwilliams35
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Re: Self-powered live well for kayak (hobie in particular)

Post by dwilliams35 »

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Last edited by dwilliams35 on Sun Mar 13, 2022 6:21 pm, edited 1 time in total.
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dwilliams35
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Re: Self-powered live well for kayak (hobie in particular)

Post by dwilliams35 »

Sounds like it’d be a lot easier to just get a small oxygen bottle rig?
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