I've said it before - I like to keep the hydration picture simple. I typically run a standard bottle cage between my arms, and I'm happy to tinker with custom bottle/straw setups to get what I consider to be a good solution for my purposes. So that's often what I recommend, because it's what I like. But my logic fails to take into consideration one key fact: not everyone likes to tinker as much as I do. Many athletes want a good, turn-key solution that doesn't require any fiddling, customization, or much effort at all. These athletes have often turned to the standard aero bottle as their hydration solution of choice. And looking around at some of the fastest riders in Kona, you can see that this solution is a popular one. But traditionally, these bottles haven't been designed with a rigorous look at the aerodynamics involved. That is, until TorHans stepped up to bat.
I asked TorHans about the aerodynamics of their bottle, and they responded with a very interesting, thorough wind tunnel test that they used when validating their product. I've made that available for download right here. Their testing protocol is well-described, and actually does seem very fair. A single test bike was rigged up, and a set of static dummy arms was placed on the bike to simulate the real-world conditions of riding. TorHans tested a large battery of products at yaw sweeps from 0 to 15 degrees (one side only), which is a complete enough picture for me. The only downside is that they chose to present their data as single points (an average of all yaw angles), instead of a two-dimensional plot which would give a more complete picture of the situation. Nevertheless, if you believe their results, then their Aero 20 and Aero 30 are very good solutions, and faster than their competitors.
Of course, any look at a wind tunnel test is best tempered by a healthy dose of criticism. And although I do find the test generally good, I have two potential quibbles. The first is that the test bike TorHans used had a significant amount of spacers above the head tube. Potentially, the Aero 20's good aero shape helped fair that stack of spacers, and I wonder if the results would change on a bike using no spacers. That's the old argument that modern bikes have such carefully-sculpted head tubes that anything in front of them will mess things up. However, that's impossible to know without another battery of tests, and at some point, you just have to draw the line of practicality. TorHans has said they would actually expect even better results on a bike without spacers. In fairness, I can see where that claim might be true - looking at the bottle head-on, it flows very well with the overall shape of the bike, and presents only a tiny frontal profile. The bulk of the bottle sits between the arms anyway, and so is shielded by the hands.
My other concern is in regards to the hand position of the dummy arms. They're in a significantly "scooped" orientation, rather than wrapping around the front of the shifters. Most testers have reported that a between-the-arms bottle actually reduces drag, that is, it should show up as negative on the TorHans plot. But TorHans still found it had 16 grams of drag, and I speculate that may be on account of the dummy's hand position.
Regardless of my qualms, which are most relevant to comparing the TorHans to a BTA bottle, their product appears to be significantly better than its direct competition, notably the Profile Design Aerodrink. My nitpicks regarding the testing probably wouldn't change the TorHans' superior results against those products. But I'm not an aerodynamicist, so take my speculation with a grain of salt as well.
With all the science out of the way, it's a good idea to talk about how the product actually works. Hit the jump for my testing experience with the TorHans Aero 20.