Electric Surfboard (extreme sports in slow motion)

After my last post, the surfboard got a brief water test in the Charles and there was evidence of a very slow leak in the tail. To remedy this, the board got two more hot coats to (hopefully) seal things off. (Spoiler: it worked)

Fins and fin mounts (compatible with commercially available fins) were hastily 3D printed from ABS. Fins were reinforced with aluminum rods but the fins were actually very strong without them. The weakest point of the fin is by far the point where it is held by the mount. The fin mounts were attached to the board with epoxy/microballoon slurry, where balloons were added until the mixture had the consistency of yogurt.

Fin mount

The aluminum bits are where the screws contact the fin and push inward/up to hold it in place.

The lab's resident Hawaiian and surfing expert noted that these fins are WAY too thick.  Next came the 'waterproof' battery. I built a 22Ah 13.2V pack and submerged it in epoxy. When you do this, you prevent the cells from being able to vent, which is bad. I tried to remedy this by attaching pieces of foam to the pack to allow for some displacement but the foam just soaked up the epoxy and by then it was too late. The pack is completely sealed and will not be happy if it ever needs to vent.

Attempt at foam with kitchen sponges. This did not work.

After the epoxy had set fully, I put on a plastic cover and cut a section out of a smoothie bottle to allow for sealing off the battery while still allowing access to power and balance leads. This was done in a rush. Adrian, don't do this again. Bad. It still worked fine in the water, but we must remember that the Charles is freshwater. No sea legs for this setup.

Sealed up

Another precaution I took was a 'deadman' switch. This is so if I fall off the board, it doesn't keep going. There are controls on the motor itself, but they don't require the user to give continuous input and it will stay on if it isn't turned off. The monstrosity below is a springy 3D printed frame with aluminum contact pads that come together when pressed to complete the circuit. When released, the circuit is opened and the motor will turn off. Umm. The glove makes it waterproof. Yeah.

Next was the motor mount, which involved very very drippy microballoon epoxy and an aluminum plate with holes for 80/20 to be attached. It looks like crap and I know it.

It's a surfboard?

The motor was attached next and damn was it heavy. Not pictured: the battery on the nose of the board for counterweight.

Sometime in October, a few friends and I headed out to test. It wasn't a sunny day but the weather wasn't bad. I had a wetsuit so I stayed pretty warm throughout the trip. Huge thanks to Tommy, Calvin, Dan, Rodrigo, and Andrew for helping out!

Everything was tied down with twine, especially the motor and GoPro.

By the way, the battery is in my backpack along with a whole bunch of foam for buoyancy in case it falls off.

It floats!

It floats... but lower

Here goes...

I went about 1/3 of the way across before turning back.

There is footage of the trip but it's 30 minutes long and I haven't edited it yet. Overall, the trip was a success. The motor didn't push me nearly fast enough to stand up. This was partially due to the motor's power being fairly lacking (it is the smallest of its class) and also because when I was just sitting or laying on the board, I was mostly underwater, providing more resistance and making it more difficult to gain speed. I topped out at about 5 mph, which was still quite a lot of fun. Also I haven't grown any extra limbs since being in the river, so I've got that going for me, which is nice.

The Fiberglass/Watercraft Post

For the first few weeks of the summer, David and I were holed up in the IDC with dreams of... the Charles. Not terribly appetizing to some, but it's the closest body of water to both of our dorms. It's totally been cleared as swimmable, anyway. We'll be fine.

We began by constructing a pair of surfboards from lasercut cardboard and shopbotted a 12.5' paddleboard. When our materials from US composites arrived, we got to work. David's paddleboard was to be glassed with polyester resin, and my surfboard with epoxy resin. Note: Polyester resin smells pretty damn awful, so wear a mask and clothes and shoes you don't care about at all.

Cue photodump!

surfboard pieces organized

stringers

The board is amazingly rigid. A friend of mine is working on an algorithm to create the hexagonal pattern for lasercutting based on a solid 3D model.

x2

I forgot to take pictures of the paddleboard without fiberglass over it, but it pretty much looks like foam. It is foam. Yes.

First layer! (actually two layers of glass)

First layer on the surfboard (also two layers)

I think this is a picture of the hot coat.

It's translucent! Also fuck yeah hexagons.

I am currently shopping for electric trolling motors to make some waves. I think I might become the first person to surf on the Charles.

Final layer on the paddle board

Rubber mat and seafaring dog added

The paddle board barely fit in the freight elevator

---awaiting pictures from Tom of us using the board---

Bonus picture of the sunset from the bridge that day

Phone Case Update: V4

Back by popular demand: update on the iPhone case! Although not much has happened since the last iteration, the fourth (and current) version does exist and is kind of cool, I think. V4 is made for the iPhone 5/5s, and features a thicker border, tighter screw holes, and glows in the dark!

Out-of-focus selfie

!!!!!

As for the other version, there's still a few remaining V3s in the wild, which will likely be replaced soon just for the sake of giving my friends cool stuff.

Update: Update: Bravo Oscar Romeo Echo Delta Oscar Mike

Welcome to 2014! I've been awfully busy not sleeping and doing things that aren't engineering. But back to the old grind... in slightly different form than usual! In the past month I picked up knitting again:

Rainbow Garter Stitch Scarf

0.5*(Hat)

Hat

Scarf that I screwed up.

Ribbed Scarf (in progress)

...learned Blender and started designing a ...thing... commissioned by a friend:

 ...and took more steps towards asserting engineering-flavored dominance over alcohol consumption:

It's a 3D printed end mill lol

jk it's a shot glass.

Soon to come: Adrian tells himself to finish his damn go-kart and tries to build a machine that knits scarves for him... and does other cool stuff too.

The MEMS post

This summer I was fortunate enough to be selected to participate in the Lutchen Distinguished Fellowship Program. Essentially a more rigorous UROP, it allowed me to continue my MEMS resonator research with Professor McDaniel through the summer.

Rewinding a bit, I started working with MEMS in late 2012, applying for UROP for spring and fall 2013. The Lutchen Fellowship is offered to 10 students each year who have partnered with a university professor to work on a research project. The program ends with a presentation by the students to the other Fellows, their faculty mentors, and Dean Lutchen.

My first semester of research involved learning MEMS CAD software, called L-Edit, which is a delightful program that only runs in 256 color. To further show how much I love this program, I will also mention that the student version lacks the ability to include text on the design. Unfortunately, this is the software that MEMSCAP, the company that manufactures the dies, wants us to use. After slaving for hours, the final designs from L-Edit are submitted four times a year to MEMSCAP and the products are shipped back to you with just enough (not nearly enough) time for you to release, test, and redesign devices for the next production run.

All ~20 of my devices fit on one of those little squares, which are 2.5mm x 2.5mm

A few SEM images for your enjoyment:

Wide angle shot of whole die

A pair of double camped beams

coupled double-clamped beams

Close up of capacitive gap

I began my summer research by a frequency divider for lab use. Although I didn't end up using this extensively, I gained valuable experience in circuit and PCB design. I used CircuitLab to simulate and Eagle to design the board, which was cut by my friend Steve. Thanks, Steve!

Thanks, CircuitLab!

Green in, Yellow out.

Next came learning how to use the Network Analyzer. The HP 3577a Network Analyzer is a charming machine that looks, feels, and smells like the 1980s. Gradually learning the quirks of this particular machine, I wrote a delightful instructional manual which can be downloaded here. About twice as old as I was at the time, the NA had seen its fair share of wear and tear (talk about rhyming). Several of the buttons were sticky, the GPIB/LabView interface was essentially unusable, and the knob that moves the cursor on screen was... wait for it... totally broken. The silver lining of this situation is that I learned to perform the measurements I needed the hard way, which led me to find menus I didn't know existed, giving me a better understanding of what the machine could do.

After a few weeks of trial and error with the measurement methods and vacuum chamber, I eventually found a circuit that worked and found several resonances. The Qs of these resonators were not as high as we had expected, but we realized we were limited by design parameters. The main issue, we speculate, is that the minimum gap between the resonating beam and the driving pad is .75 microns, which forces us to have a large DC bias and drive voltage. This means that we are driving the beam really hard, which causes changes in the center frequency and reduction in quality.

My vacuum chamber

Wire Bonding (cell phone microscope picture)

The first resonance I could find in my pictures

What we established:

Resonant frequency is proportional to AC drive and inversely proportional to DC bias

Quality is inversely proportional to both AC drive and DC bias

Take a look at the hastily-constructed charts below for more details.

This research will continue through (at least) the fall semester and hopefully after that as well. Stay tuned for more updates and beautiful charts.