Solar powered boat

[Paul Scott]

Bow down too- are the propellers pushing that?

 

[kerosene]

nevermind, didn't realize this was for a miniboat



Solar Trimaran concept - please review. https://www.boatdesign.net/threads/solar-trimaran-concept-please-review.64626/

this is my old idea that I never moved forward with.

I think the PVC is really bad idea though. Wood despite it's ancient-ness is probably far better.

 

[kerosene]

I recommend you explain your goal, other project parameters and limitations etc. then we can help better.

Thin film is light but W/$$ is typically very bad. If you need panels high up then the weight might justify using them.

 

[kerosene]

a very skinny small boat can beat the hull speed easily - which is no hard limit. It is point at which waves made by boat start to create an uphill and power demand goes up. Skinny boats frequently don't care much about this as the waves are small enough to begin with.

Few basic principles for going fast on a boat
-weight is enemy
-width is enemy (which is why catamaran is good - you get the needed stability)
-long hull is "always" desireable
-if there is enough power to weight you can plane which changes things somewhat. 0.75 sqm might do this.
-propeller was covered well - it needs to match the speed and power need. It's likely very hard to get RPM low enough so it will be a compromise.

looks like 100W semi-flexible panel is the right surface area range
100W ETE semi flexible solar panel SZ-100-36MFE - Akromex https://www.akromex.com/eshop/product.php?id_product=341

I think getting 80% of the nameplate power is fairly realistic in a cloudless day and bit less if installed flat (not aligned to sun).

50W+ on a few kg boat is plenty. but the 100W panel alone weighs 2kg...

 

[High72]

Hello everyone,

Sorry for the very late response, I sort of forgot about this forum for a while.

The initial design was scrapped and replaced with a much simpler one, 0.8m x 1.2m trimaran, I guess a very similar design to the video of the cat posted a while ago on the thread, around 25kg since 6-inch PVC will be used, will be using a 140w monocrystalline solar panel that charges a lead acid battery and then the boat's propulsion will be via a drill motor which produces around 150w. Propeller maybe 6-inch diameter plastic 2 or 3-blade. The current concern is that the solar power harvested by the panel won't be enough to push the boat, therefore requesting to see some propulsion calculation as soon as possible, and I'll be very grateful if you can provide some guidance for the propulsion calculation.

High72

 

[BlueBell]

High72, welcome back.

Many have responded to your previous posts.
Have you read them?
Please go back and answer all the questions asked of you.
They are more important than you may realize.

There are a number of ways forward but the questions need answering first.

BB

 

[BlueBell]

I recommend you explain your goal, other project parameters and limitations etc. then we can help better.

Not a question but a very important recommendation that needs addressing please.

Thank you.

BB

 

[High72]

I have read those comments and recommendations. This is my mechanical engineering final year project, I thought of doing something very simple after 5 years of hard work. The purpose is creating a boat that is environmentally friendly and scale-able. There is no goal of power, speed, weight, etc. But the parameters (that are stated in my recent message) that we have now seem realistic and more accurate than before. I have about 1 month left till the deadline that is why I'm trying to finalize everything now and check these parameters work so I can get to putting the boat together. That is why I need help with calculating propulsion if anyone has an tips for that so I can show everything to my supervisor.

Thanks in advance.

 

[BlueBell]

The purpose is creating a boat that is environmentally friendly and scale-able.

There is no goal of power, speed, weight, etc.

Perhaps a sailboat, they are solar powered as the sun makes the wind blow.
And if you make it out of logs you can call it environmentally friendly too!

 

[High72]

Sorry if I didn't make it clear but I unfortunately can't change the concept now as I submitted my project proposal and started writing my thesis report, stating that the boat would be made from PVC and will run using a motor and a propeller, and that it would be solar powered, I just need a stamp of approval from you fellas, if the numbers stated above are viable then I'll be good to go.

 

[BlueBell]

I'll be very grateful if you can provide some guidance for the propulsion calculation.

Thrust = Drag
So just pull the boat through the water at various speeds using a scale to measure the resistance.
That will also be your thrust required to achieve those various speeds.

150W should be lots of power to move forward at 3 or 4 knots.

 

[bajansailor]

So just pull the boat through the water at various speeds using a scale to measure the resistance.

It does not have to be anything complicated - we got very good results when model testing using a simple spring balance (eg the typical type for fishermen, with a hook on it for weighing fish).

This BDF thread from 2011 might be useful -
Prop Thrust Calculation https://www.boatdesign.net/threads/prop-thrust-calculation.38283/

 

[SolGato]

You should consider using a large 2-blade RC plane prop since you’ll be using a drill which will have gear reduction for torque multiplication and a limited RPM.

Your wattage consumption target of 150W is pretty low, so turning a big prop slowly to push your light displacement vessel should give you the best range and performance.

Keep in mind 150W consumed will be somewhat less at the prop depending on the efficiency of your drill and prop.

I would suggest a Brushless 2-Speed drill at the highest voltage.

And I would size the prop so Speed 1 is the 150W cruising speed, and Speed 2 a Boost/Burst mode.

 

[High72]

Very informative stuff fellas. much obliged. Will take by that advice Sol Gato thanks!

 

[kach22i]

RCtestflight on youtube has been playing with different props and solar power, but he is maybe not the best source for aquadymanics, his hulls seem inefficient, and it seems like he can do a bit better in the propellers, but he has drawn a number of propellers and other bits that you might be able to gank.

I just watched one of his many videos, interesting stuff.

Testing 12 Ultra Efficient Electric Boat Propellers

The solar powered hydrofoil prop from the Netherlands mentioned near the end of the video scored lower than the standard test model unfortunately. Then again as you mentioned it may have something to do with his real world testing rig.