Arvel Gentry was a research specialist in transonic, supersonic and hypersonic vehicle aerodynamics at the McDonnell-Douglas company. According to his nominator and the many articles provided as evidence, he changed the way we look at sail shape and the aerodynamics of sailing.

I went sailing one day with a friend on a Saturday afternoon on a little lake in California, and I was hooked. This was wind, and this was water, and this was a game I could play.

Genty’s greatest contributions included theorizing, testing, and ultimately developing a greater understanding of the aerodynamics of sails – he assisted with America’s Cup Campaigns – and writing and collaborating on numerous articles and professional papers in language that could be understood by the sailing public.

• Gentry gained an understanding of the aerodynamic science of sails and airflow, and applied and tested that science on the water
  • Developed some of the first methods to instrument full-sized sailing vessels and capture precise data
  • His interpretation of this data changed theoretical basis explaining the forces generated by sails
  • Was able to distill this knowledge into user-friendly language for public consumption
• Publications included: Sail Magazine, Sailing World, Yachting, Sea & Pacific Motorboat, Los Angeles Times Magazine, New York Times, North Sails website, and numerous technical papers presented at symposiums (see below for a partial list with links)

 

From Boat Sense, by Doug Logan, ca. 2020:

Remembering Arvel Gentry and John Letcher, Pioneers of Sailing Science
It was a quarter-century ago that Sailing World published “Fluid Dynamics: How Modern Science and Sailing Discovered Each Other.” The main players covered in it, Arvel Gentry and John Letcher, have gone to Fiddler’s Green, Gentry in 2015 and Letcher in 2018. Both were geniuses and gentlemen of the sport.

Almost a quarter-century before that article appeared, Gentry had written a series of lessons in Sail magazine that debunked some of the popular concepts of how sails worked. “Gentry and company were weighing in with talk of stagnation streamlines, separation bubbles, starting vortices, Kutta Conditions. They were saying outright that much of what modern sailors had been taught about lift and drag on an airfoil was just rot. And they weren’t appreciated.”

They weren’t appreciated because, as sailors and human beings, we tend to simplify concepts until our brains are comfortable with them. Well, as Einstein said, “Everything should be made as simple as possible, but not simpler.” To this day, despite the prodigious advances in both the hardware and software that have made computational fluid dynamics (CFD) commonplace in the design of vessels, sails, and underwater appendages, there’s still plenty of mystery in how these structures operate in the real world, and it’s not for want of either brain power or computer power.

What aero-hydrodynamicists and computer engineers have been able to do with CFD is create an animation of dynamic events, and they can make pretty accurate predictions of how things will work given a particular set of imagined conditions. But of course fifteen degrees of heel angle are not always fifteen degrees. And real waves don’t observe a constant height or frequency. Windspeed varies. Wind direction varies. The same goes for the set and drift of water current. Then add in the human factor: People steer differently, and trim sails differently, and move around the boat, changing everything all the time.

As the Fluid Dynamics article says, “The essential challenge… is in trying to make a vessel move nicely through two fluids simultaneously, part of it stuck down into thick, slow-moving water, and the other part stuck up into thin, fast-moving air. Add peripheral challenges like waves, local wind dynamics, geographical effects on both fluids, and the limitations of boat design, and you’ve got an excellent puzzle to solve.” Which is why people like Gentry and Letcher have always been drawn to the sport, and why sailmakers and Formula One engineers and aeronautical engineers enjoy talking to each other.

There’s still mystery in sailing because the elements we sail in are always chaotic, slightly or greatly. It seems likely that there are some people who, by nature or practice or both, are better attuned to the what’s coming through the chaos pipeline than the most powerful and sensitive computer program. Will that always be the case?

– DL

The following links are a fascinating dive into many of Gentry’s articles and papers from the 1970’s through the 1990’s that challenged common beliefs about aerodynamics and sailing. When his scholarly papers are compared to his magazine articles, it is clear that Gentry was a master at taking complex, discipline-specific language and making it understandable for those who are not in the field of physics. 

1-How-Sails-Really-Work

12-What-Goes-Around-Comes-Around

13-FluidDynamics-How-Science-Sailing-Discovered-Each-Other

15-Rigging-and-Handling-the-Spinnaker

2-Boundary-Layer-Flow-and-the-Headsail

4-Another-Look-at-Slot-Effect

6-Why-the-Save-Leeward-Works

7-The-Double-Head-Rig

8-Checking-Trim-on-the-Wind A-Review-of-Modern-Sail-Theory

Aerodynamics-Of-Sail-Interaction

Application-of-CFD-to-Sails (1)

Are-You-at-Optimum-Trim

Boundary-Layer-Flow-and-the-Headsail

Checking-Trim-on-the-Wind

Design-of-the-Courageous-Mast

Downwind-Tacking f

fluid-dynamics

How-a-Sail-Gives-Lift

InnovSail2008-paper

Low-Drag-Star-Mast

More-on-the-Slot-Effect

Origins-of-Lift Sailboat-Performance-Testing-Techniques

Studies-of-Mast-Section-Aerodynamics