With the help of several members of this community, I could make the prototype in the torpedo design work and I did a lot of measuring and mapping with it.
It went very well, so I decided to build an improved version of the sonar boat which you can see in the picture above.
But first I will share some impressions of my first boat. In the following picture you can see me with my "torpedo design" boat.
In the video below you can see the performance of the boat.
The ArduPilot worked very well and the speed, size and the operation range were satisfying. But the propulsion nozzle turned out to be very sensitive to sea plants. And in windy conditions with waves and in curves, it was rolling quite a lot. I measured a big lake with it as you can see in the Google Earth picture on the bottom of this page, but I decided to build a more stable boat.
So now I tell you about the Making of the improved boat:
The new boat should be able to carry more batteries, be more stable in the water, be faster and not be too much bigger. So I decided to build a small trimaran. I started to plan it with DELFTship which is for free and easy to use.
I also used NX to plan the space I needed in the hull as you can see in the pictures below:
The next step was the making of the positive mold. I could use the laser cutter of the Fablab in Aachen (https://hci.rwth-aachen.de/fablab) to cut the sections that were exported from DELFTship out of 3mm MDF.
At home I glued everything together with hot glue and filled it with Styrodur that I cut before:
After a lot of grinding and filling, it looked like this:
After some more grinding and painting, I made a negative mold with plaster bandages to keep the costs low and painted it with 2K paint. After waxing the mold I could start with the glass fiber:
I used the following product and which worked very well:
http://shop1.r-g.de/art/100110
The resin has a curing time of 40 min which makes it very easy to use. The result looked like this:
After equipping the hull it was ready for the water:
In the following video you can see the making of the boat step by step:
Before letting the boat into the lakes I wanted to be able to find it after its work under any circumstance so I included an XBee 900 pro for a GPS-data link. Also I wanted to be able to manipulate the track of the boat by a joystick with the XBee, so I printed a case for a small remote control to include the XBee, a thumbstick, a small Arduino and other switches.
I am now able to switch between the XBee-controll and the ArduPilot with a multiplexer on board.
After that final step, I was ready for the next lakes.
After improving the ArduPilot parameters the trimaran performed very well. I could switch the boat on, put it into the water and have breakfast at home, before picking it up after several hours and it was always there. If the wind had blown it away, I could track it via the XBee and with the Earth Bridge, I could watch its position live on Google Earth.
In this Video you can see the performance of the boat in different conditions:
The following pictures will give you some impressions of the measuring:
In this last picture, you can see the work i have done so far with the boats and in the area, there will be many more lakes for measuring.
If you have questions or suggestions just comment and I try to answer quick.
Comments
@Justin:
I acutally thought about that as well but for huge lakes. It would be possible to supply the boat with solar power but i dont know anything about measuring depths of more than 50m. But you are right. Its a good idea!
@Emlid:
The sonar as a beam angle of several degrees. I guess you dont need a GPS resolution under 1m but it would be a good improvement! When I am done with the improvement of the remote control, I will inform myself about the RTK GPS.
@Antonie:
What do you mean by return of the pulse? It is a closed system and it only gives me a string out with the informations about the depth and the temperatur.
When my first boat was rolling a lot I thought about building a stationary mounting, that would hold itself horizontal with servo motors. But the new boat is really stable. The rolling that it still does is less than the beam angle of the sonar I would guess so I wil not need to calculate the angles.
How long did this entire project take you?
Are there more details on the recording of your depth and gps recording elsewhere?
What are your thoughts on http://reefmaster.com.au underwater mapping software using your method?
Thanks!
Wow, that's a pretty impressive sonar project. @Tony Stark's Lab: Don't we all :) I have the copters laying around in a mostly empty lab, what I wouldn't do to get tools in there :)
@Monroe: It shouldn't be too hard. If you can acquire fairly accurate sonar sensors and use multiple points on your boat, you could triangulate the position of the sub in relation, and use that for navigation. For communication, I think a radio link would work for a short distance. Of course, you could always just tether ;) My roommate built a small remote controlled sub with a tether out of PVC, an acrylic dome, and some pumps from a fish tank for direction and buoyancy control. Doesn't need to be fancy, just work :)
@Burkhard: Great work! Very nice molding, I wish I could get anything that nice out of my molds. Great work on the boat, I look forward to seeing where you go with it next!
@Harry and Emlid:
Thanks! Usually you do a negative mold out of glass fiber as well as you can see in the video below:
But i feared, that i will never be able to seperate the negativ mold and the finished hull once its done, so i decided to make the negative mold out of the plaster bandages. It cost me about 20€ instead of around 100€ and i could rip the negative mold apart as soon as the rasin was cured.
I really like the technique you used for making the plug and mold.
Thanks Harald!
And thank you for your ArduPilot support and all the other ideas!!! I hope your boat is doing fine!
Congrats!
Well done.
Harald
Hi Burkhard,
I looked at putting a little vessel together for one of our projects where we had to place rock around a water inlet under water for a hydro scheme, but the project did not happen, so I discarded the attempt.
The following issues stuck out for me:
1. The tolerances defined by the sonar manufacturers - where is the return of the pulse. Looking at various densities of the substrate, the return point is a bit of a vague description. On a harbour project I worked on, the guys measured the shape of rock breakwaters, this was solid, but on century old lake bed with fermenting vegetation....
2. With the roll and pitch of the vessel, do you consider the angles of these in the calculation of the vertical depth?
We used the point clouds to monitor the placing of rock at sea to form the breakwaters. We used a home brewed package called Model Maker and our German mates used Augusta(I think). Now I use Autodesk Civil 3D. very powerful software package if your into this discipline.
http://diydrones.com/profiles/blog/show?id=705844%3ABlogPost%3A1625...
These chaps are working towards an affordable RTK solution on the RPI. IMHO this will work great for your application to improve the accuracy. I'll be looking at this for my rover that needs <50cm placing.
Again, looks very good.
Burkhard, amazing work. Very well engineered, looks like you have some previous modeling experience, because mold stuff doesn't usually work out from the first time)
You should definitely think about upgrading to RTK GPS. This would make mapping possible, and make a great tool for surveyours.
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