Featured Stories | August 19, 2014

Flying on the Foils: a Q&A with Brooks Reed, MIT’s Moth Sailor

By Genevieve Wanucha

“Like any extreme sport, sailing the Moth definitely requires a balance between fearlessness, commitment, and caution.”

It’s an unmissable sight down at the MIT Sailing Pavilion on Memorial Drive. All summer, a hydrofoiling sailboat has been flying atop the Charles River, reminiscent of the catamarans raced in last year’s America’s Cup. The person skillfully handling this International Moth Class boat is none other than Brooks Reed, a MIT PhD student who works with Prof. Franz Hover‘s research group in the MIT Dept. of Mechanical Engineering. Reed learned to sail at the age of 8 and has been racing competitively ever since.

Here’s Oceans at MIT’s Q& A with Reed. First, check out this video. Reed attaches a GoPro video camera to the Moth to catch an amazing perspective on his experience of “silent acceleration,” as well as some of those inevitable high-speed crashes.

Why did you start sailing the Moth on the Charles River?

The MIT Sailing Pavilion bought the boat over the winter for several reasons. First, the Moth is a really fun boat to sail. Second, MIT has always promoted technology in sailing, especially college sailing, which traditionally resists change and uses sturdy but low-performance boats. Also, the possibility of getting to sail the Moth will probably help recruit prospective students to apply to MIT and join the Sailing Team. I want to thank MIT sailing master Fran Charles and the sailing team coach Matt Lindblad for giving us the opportunity to sail a boat like this. No other college program has anything close to this boat in terms of performance and technology, and also fragility.

I’ve wanted to sail one of these boats ever since I heard about hydrofoiling when I was in high school. When I was applying to MIT undergrad in 2005, one of the short admissions essays was to write about an inspiring concept or technical solution–I wrote mine about the Moth. I have always liked high performance boats, and the Moth is a dynamic, challenging boat to sail, which uses elegant technical principles in its design. I’ll probably get my own Moth someday and try to race more seriously, so being able to learn how to sail one here on the river–for free–is great. I can leave my office and be foiling around the river in 30 minutes.

How did you learn to handle a hydrofoil boat? Have you sailed something similar in sailing competitions before?

Courtesy Brooks Reed

The learning curve on this boat is really steep. Pretty much everyone spends their first couple sessions with equal amounts of time flipped over vs. sailing!

I had a bit of a head start because I’ve done a lot of high performance sailing in the past, but not foiling. The most helpful experience was sailing a small skiff called the 29er in San Francisco Bay and other locations around the world during high school. Although this boat is sailed with two people and doesn’t foil, it is fast and difficult to handle just like the Moth. Over the past 3 years I have also done a lot of high performance catamaran sailing—another MIT ocean engineer, Jeff Dusek, and I own and race an F18 catamaran together. Because of their width, catamarans are much more stable than the Moth, but the F18 is fast and powerful, so some of the concepts carry over.

Learning to sail the Moth mostly just comes with practice. One thing that helped was to watch a lot of YouTube videos of experienced Moth sailors. The technique involved in sailing the boat is very unique, so seeing it done correctly is a good starting point. But there’s no substitute to getting on the water and trying things out. I also have some friends who have been racing Moths for a while, so I bug them a lot with questions about boat setup or specific techniques.

What’s the most difficult part about sailing a hydrofoil?

I think the most difficult part is that the boat is so dynamic. The Moth weighs about 65 pounds, so the sailor is much heavier than the boat. Since the boat is up on the foils, no stability comes from the hull. It’s a balancing act, a bit like riding a bike. The boat accelerates and responds to changes in the wind so quickly that you can’t sit back and relax, or even try to react to what the boat is doing. You have to anticipate the behavior of the boat, actively steering and adjusting the sails and foil controls in order to keep the boat sailing smooth—sailing this boat is really athletic.

The speeds that this boat can reach, even in moderate winds, are very high, so if you do something wrong you can crash really hard—water doesn’t feel too soft when you are going 25 knots! But since the Moth is so dynamic, you can’t back off—the boat is happiest when it’s being pushed hard. Like any extreme sport, it definitely requires a balance between fearlessness, commitment, and caution.

And what’s your favorite thing about it?

 It’s hard to pick a favorite out of the many great things about this boat. Certainly, the challenges I’ve described are a major part of why the boat is so fun to sail. I would have to say that my favorite part is the instantaneous feedback the boat gives you when you sail it right. The boat just lights up when you get the settings and technique dialed in. Because the Moth is flying on the foils, it’s almost completely quiet when sailing, as opposed to the usual loud sounds of spray coming off the hull. That feeling of silent acceleration is really unique. Foiling kiteboards can probably offer similar excitement and slightly faster overall speeds. But for me, I like how the Moth is a very refined and high-tech machine.

On a more technical note, how does the foil control system work?

The Moth uses a mechanical feedback system to regulate the height and pitch of the boat when on foils. My research involves feedback control, one of my favorite subjects in engineering, so this aspect of the Moth really interests me as well.

A wand at the front of the boat skims the water’s surface, and rotates based on the height at which the boat is above the water. The rotation is connected via a series of linkages to the flap on the main hydrofoil. So, as the boat changes height, the angle of attack on the foil changes, which changes the amount of lift produced. This setup enables stable foiling using active control, which is different than the methods for foiling stability used on the America’s Cup catamarans.

Does the filming have anything to do with a scientific interest, perfecting your technique, or is it just super cool to watch?

Mostly, the videos are just fun to watch, although I have been able to make some improvements to my sailing technique by watching them.

Scientifically, it would be interesting to put a few different cameras at different angles on the boat, and also add some instrumentation. It is definitely possible to make an instrumentation package including accelerometers/gyros, a GPS, a compass, an ultrasonic sensor to measure the height above the water, and encoders on the wand system. With those data, you could study the performance of the boat from a more principled controls perspective. I think it would be cool to eventually use such a scientific approach to make improvements to the boat. People have done a bit of this already, but you never know what a group of MIT students might be able to add.