Sunday, December 4, 2011


Welding the port wing of the TEMA
TEMA sitting on our equipment trailer at an angle so that it will be street legal.
Electromagnetic sensors inside the TEMA
TEMA on the R/V Ugle Duckling
We were very happy that we could raise the TEMA out of the water onto the A-frame of the boat.
A few years ago my colleague Rich and I had an idea for an improved underwater metal detection system.  We were literally having a beer and sketched it out on a napkin.  We called it the Towed Electromagnetic Array or TEMA.  Now almost three years later this idea is quickly becoming a reality.

Over the last year, between other survey jobs, we have been moving forward with our design.  I created a three dimensional drawing in Google Sketch Up, generated drawings for plastic components, researched and selected materials, and even built a 1/5 scale model.

Over the past few months I have been working intently on developing the TEMA.  This summer we purchased much of the materials, and had the larger plastic components cut to size.  The TEMA is constructed with high density polyethylene plastic and structural fiberglass.  Due to the uncertainty of the final design, we decided to complete the construction ourselves.  This meant a lot of hands-on work.  I purchased the necessary tools and taught myself to weld plastic.  It took two of us about four weeks to build.  It was certainly an evolving design and I really enjoyed the process.

The TEMA was constructed in three sections; each one 3.5 by 11ft.  Thus the final assembled product is too large to easily transport down the road.  An engineering solution was necessary.  Inspired by the hydroplane racing boats we built a mount to hold the TEMA at the 45% angle on the trailer.  In this configuration it sits 12 feet tall and 8.5 feet wide, in other words it is now street legal.

Designing and building the physical towfish is only part of the challenge.  Along the way we have been working to integrate and modifying the on-board sensors.  Being neither a mechanical nor electrical engineer I often feel like I am shooting from the hip.  There has been a lot of wiring and testing of electronics, this has resulted in me becoming proficient at soldering.

We still have a lot of challenges ahead but when we get the full system up and running it is really going to be amazing!

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