Team Peruagus (University of Southampton)

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gdp...@gmail.com

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Oct 20, 2017, 9:15:32 AM10/20/17
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Hello everyone,

we are Team Peruagus from the University of Southampton. We are a group of 6 students and, as part of our masters program, are attempting a transatlantic crossing under the regulations of the Microtransat Challenge.
We started this project less than three weeks ago and we would already like to thank everyone, who is sharing information in this forum, for doing so (special thanks to Team Joker for answering our emails!). It is very valuable to new teams like ours and allows us to not repeat every mistakes that has already been made.
One thing probably making us stand apart from the majority of teams of the Microtransat Challenge is our decision to enter the non-sailing class, as we have decided to not rely on wind power 100%, but are considering solar as our main source of energy.
We are very happy to share information with all other teams and we are in the process of setting up a facebook page documenting our project. We will share a link to the page here.
Any questions, please comment on here or send us an email.

Team Peruagus

PS: Peruagus (lat. World Traveller)

andy

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Oct 21, 2017, 8:08:01 AM10/21/17
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Google some motorboat projects outside Microtransat: Solar Voyager, Scout Transatlantic, SolarSurfer and SeaCharger. The first two had some problem with the rudder. SolarSurfer reported problems with thruster entanglement - don't use a ducted propeller. SeaCharger did amazing job, their design is inspirational. I have no doubts that a properly designed motorboat would cross the ocean, but I have doubts that it would navigate to the target point within a 50km radius. You can't fit more than 200W solar power on the 2-metre boat, so it won't be faster than specific ocean currents in the Atlantic that don't always flow in your direction. When I started building a motorboat and I realized that it would act more like a "floating log", I have given up and I started building a sailboat. Just my thoughts. You may have better ideas how to build a reliable and fast enough motorboat.

Colin Sauze

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Oct 23, 2017, 10:46:16 AM10/23/17
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On 21/10/17 13:08, andy wrote:
Google some motorboat projects outside Microtransat: Solar Voyager, Scout Transatlantic, SolarSurfer and SeaCharger. The first two had some problem with the rudder. SolarSurfer reported problems with thruster entanglement - don't use a ducted propeller. SeaCharger did amazing job, their design is inspirational. I have no doubts that a properly designed motorboat would cross the ocean, but I have doubts that it would navigate to the target point within a 50km radius. You can't fit more than 200W solar power on the 2-metre boat, so it won't be faster than specific ocean currents in the Atlantic that don't always flow in your direction. When I started building a motorboat and I realized that it would act more like a "floating log", I have given up and I started building a sailboat. Just my thoughts. You may have better ideas how to build a reliable and fast enough motorboat.

A couple of teams registered solar boats (well one is a hybrid solar/diesel) this year for the Microtransat but so far neither have started the race. Have a look at http://www.microtransat.org/2017_epsom_boat.php and http://www.microtransat.org/2017_uci_boat.php.

I do share Andy's concerns that you might struggle to get enough energy from your solar panels to navigate accurately. Have you considered some kind of hybrid system like the C-Enduro (https://www.asvglobal.com/product/c-enduro/) uses?

Colin.

Peter van den Brand

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Oct 23, 2017, 2:16:35 PM10/23/17
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I have been toying with the idea to build a solar boat as well. I did some calculations to figure out how many watts I'd need to keep a motor boat going at a reasonable speed for 24h a day. The calculation roughly went as follows:

  • I want my boat to go approx 5 km/h, which is 2.7 knots (this is the theoretical hull speed for a 1.2m boat, so a sail boat wouldn't be going any faster)
  • Compute drag for the hull at that speed:
  • Multiply the dray by the speed (in m/s) to get the required watts:
    • 2.5 N * (5 / 3.6) = 3.5 watts
    • Multiply the watts by 2 because power is lost in the "drive train" (this is a big fudge factor, but could be reasonable according to some posts I read on the internet)
    • Multiply by a factor of 4 to 6 because you only get 4 to 6 hours of full sunshine per day on average
    • So 3.5 * 2 * 6 = 42 watt peak required

If you're happy with a slightly slower speed, then the drag goes down very quickly. An IOM only has a drag of 1 newton at 4.2 km/h. That means just 17 watt peak of solar panels required to keep the motor going 24 hours a day. In sunny parts (using a factor of 4 instead of 6) it would even be just 11.2 watt peak. Fitting around 25W on a 1.2 meter boat should be quite possible, and I'd expect that boat to go somewhere between 4 and 5 km/h, which is more than the approx 1-1.5 knots that ocean currents can be.

Note that selecting the right motor would be crucial. The motor would need to be relatively small, because it needs to produce less than 10W and the right RPM at its peak efficiency. Maxon has several motors that would fit the criteria, but they are quite expensive. Any motor that you buy for an RC boat is massively overpowered I think, and would be very inefficient to drive slowly.

I haven't built any motor boats though, so I don't actually know whether the calculation is correct. Given the comments below, I must have missed something. Any idea whether I'm on the right track?

Thanks,

Peter

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Chris Diacov

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Oct 23, 2017, 5:30:07 PM10/23/17
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Hello Peter,

 

I don’t think you’ve missed anything. Your math is correct (or at least in the ball park) and is backed by real-life tests. I can confirm that with a fairly draggy configuration (cylindrical floats, 0.07m draft, 0.95m LWL) you can achieve sustained speed of 2.0+ knots at 9W (measured at the power source). Our Mk. III project daily power budget was 260Wh which was tested and confirmed on a single 50W panel (in the tropics, May – September).

 

Two (major) caveats:

 

-          Speed measured in calm water. If you’ve ever sailed off-shore, you’ll know that this doesn’t translate well to ocean passage conditions;

-          You can go significantly faster than that but power requirements go up with the square of speed;

 

For all intents and purposes, you can consider your solar harvest rate to be no more than 100W/sq.m. of solar panels (assuming highly efficient panels and optimal insolation). Fitting 0.25 sq.m. of solar panels on a 1m monohull is a tough job (but maybe not impossible).

 

And one final note on the navigation challenges with low speed vessels: whether sailing or motoring, very rarely the best route to your next waypoint is a straight line. If you build your course calculation logic based (solely) on that assumption, you are setting yourself for a serious disappointment :)

 

 

Cheers!

--

Chris, Project Pilotfish

http://www.projectpilotfish.com

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JOSE ANTONIO COZAR RIOS

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Oct 24, 2017, 6:37:11 AM10/24/17
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Team Peruagus your are wellcome. I al so working in a similar solar project with single hull. I can share with you my ideas if you want. You can look in the forum data about my proyect and some photos.
About the catamaran solution I response my reflexión to Andy in the Last post. I think that is a bad idea.

Kim

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Oct 24, 2017, 10:39:13 AM10/24/17
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Hi Peter,


I think your calculations seems sane and I don't think I can give you anything better, but... I think you should take a look at the following videos, if not already seen them.


Here's a good'ol salty bear that explains a good deal about monohull vs. catamaran as discussed further down in this conversation, but also some details about why a boat behaves the way it does. Definitely interesting and very good explanation.


https://www.youtube.com/watch?v=G5JOuSuT-lI  <--Monohull vs Catamaran


https://www.youtube.com/watch?v=H8hvKZ73S0Q  <-- Hull speed


Just a little contribution to the discussion.


   /Kim

Colin Sauze

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Oct 24, 2017, 11:11:29 AM10/24/17
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On 2017-10-23 20:16, Peter van den Brand wrote:

I have been toying with the idea to build a solar boat as well. I did some calculations to figure out how many watts I'd need to keep a motor boat going at a reasonable speed for 24h a day. The calculation roughly went as follows:

  • I want my boat to go approx 5 km/h, which is 2.7 knots (this is the theoretical hull speed for a 1.2m boat, so a sail boat wouldn't be going any faster)
  • Compute drag for the hull at that speed:
  • Multiply the dray by the speed (in m/s) to get the required watts:
    • 2.5 N * (5 / 3.6) = 3.5 watts
    • Multiply the watts by 2 because power is lost in the "drive train" (this is a big fudge factor, but could be reasonable according to some posts I read on the internet)
    • Multiply by a factor of 4 to 6 because you only get 4 to 6 hours of full sunshine per day on average
A factor of 4 to 6 is a bit optimistic for the solar panel. I'd usually work on a factor of 10. Although it depends on the weather, time of year and latitude/route.

Also remember that in open ocean you can expect waves of 2-3m on average, so this is going to have significant effects on your speed. During a storm it might not even be worth trying to drive the motors.

    • So 3.5 * 2 * 6 = 42 watt peak required

If you're happy with a slightly slower speed, then the drag goes down very quickly. An IOM only has a drag of 1 newton at 4.2 km/h. That means just 17 watt peak of solar panels required to keep the motor going 24 hours a day. In sunny parts (using a factor of 4 instead of 6) it would even be just 11.2 watt peak. Fitting around 25W on a 1.2 meter boat should be quite possible, and I'd expect that boat to go somewhere between 4 and 5 km/h, which is more than the approx 1-1.5 knots that ocean currents can be.

Note that selecting the right motor would be crucial. The motor would need to be relatively small, because it needs to produce less than 10W and the right RPM at its peak efficiency. Maxon has several motors that would fit the criteria, but they are quite expensive. Any motor that you buy for an RC boat is massively overpowered I think, and would be very inefficient to drive slowly.
I doubt any motor you buy for an RC boat is designed to run non-stop for a few months.

My own experience in building a motorised boat is that it was quite inefficient in terms of converting electricity into forward motion, although this was building a much larger boat designed for going through ice so speed wasn't the key criteria for the hull design. There's a lot more detail about it in this paper, http://www.thejot.net/?page_id=837&show_article_preview=712&jot_download_article=712

Colin.

gdp...@gmail.com

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Oct 24, 2017, 4:36:45 PM10/24/17
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Hey Andy, thank you for your comment. We've come across most, if not all, of the projects you mentioned and have taken them into consideration. We've also come to that conclusion about ducted propellers and so will be avoiding them. We are definitely taking your comment on currents in the Atlantic into account. Whilst we have not ruled out also utilizing the wind, we actually have an interesting concept that we will be experimenting with and hopefully unveiling soon, we will not rely only on wind power only. We are also going through a great deal of weather data and we will be selecting a very carefully thought out route. We also have a Facebook page where we will be sharing a lot of our progress - https://www.facebook.com/TeamPeruagus

adam.alc...@gmail.com

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Oct 24, 2017, 5:15:15 PM10/24/17
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Hello all,

Just thought I would write some more about resistance and powering as I see there is much debate on it. We've just completed our first hull design on the 3D CAD package, Maxsurf, based on a very rough/preliminary required displacement estimate. To calculate its resistance we will be using the ITTC 57' equation to calculate its viscous resistance coefficient. Our wave resistance coefficient will come from slender body analysis, a computational method that divides the hull into separate panels and then calculates the wave pattern each panel generates. It then sums all of the wave patterns to produce the total wave system produced by the hull. The energy in this wave system is equal to the energy lost/resistance due to waves.

Once we have our resistance value we will then use estimated efficiency's to calculate our required power from the motor, taking into account additional power required in waves. We will then use this to calculate a required solar panel area to power, check if this is achievable and then iterate until we have a hull that can provide both a low enough resistance and enough deck area to house the required solar panels

If anyone has any questions please feel free to message us and we will reply as soon as possible.

Kind Regards,
Adam Alcantara
Team Peruagus 

gdp...@gmail.com

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Nov 4, 2017, 8:41:08 AM11/4/17
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Hello everyone,

We are approaching our detailed design phase now and were wondering if the microtransat waterline length includes a rudder attached at the end of the hull. According to the official definition of LWL, the rudder would not be included. However, we wanted to double check how microtransat is dealing with this. Does anyone know the regulations on this?

Thank you,

Julian
Team Peruagus

Paul Miller

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Nov 4, 2017, 11:16:05 AM11/4/17
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Hi,

There is a bit of an ambiguity in the rules as the top of the rules page it says,

"There are two classes of boat allowed:

  • The sailing class permits only wind power for propulsion. The hull overall length (LOA) is restricted to two point four (2.4) metres.
  • The non-sailing class permits any source of propulsion. The hull overall length (LOA)) is restricted to two point four (2.4) metres."

But later on it indicates it is LWL. The LWL is the old rule, the LOA is the current rule. (Colin, could you fix the confusion?)

LOA includes the rudder.



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Colin Sauze

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Nov 6, 2017, 6:14:42 AM11/6/17
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On 04/11/17 15:16, Paul Miller wrote:
Hi,

There is a bit of an ambiguity in the rules as the top of the rules page it says,

"There are two classes of boat allowed:

  • The sailing class permits only wind power for propulsion. The hull overall length (LOA) is restricted to two point four (2.4) metres.
  • The non-sailing class permits any source of propulsion. The hull overall length (LOA)) is restricted to two point four (2.4) metres."

But later on it indicates it is LWL. The LWL is the old rule, the LOA is the current rule. (Colin, could you fix the confusion?)

LOA includes the rudder.


Paul is correct, the rules are now based on LOA. Although rule C.4 still says LWL as it was covering the transition. There will be a rules review next month and i'll fix this up then.

Colin.

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