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Mantis position: what makes it fast?
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Hi folks,

For those that spend time in the tunnel, what makes the mantis position fast?

Why is it faster on some riders but not others? Is there a rhyme or reason to it? I know it can help to drop the shoulders/front of body.
Is it more helpful for flat back types, or just those that have a harder time getting low?
Is it only helpful if you can get you face close to your hands?
Is the benefit speed dependant?

I figure the hands up front can make a nice aerospike (it that a thing at sub supersonic speeds?), that might help channel airflow over/around the head/body. Kind of like a nosecone on a bluff body.

When looking at the rider from the front, is our goal to fill that “anatomical parachute” that occurs as air goes between out arms, below the chest, and smashes into our pelvis? Does a mantis position and narrow armrests, plus or minus a bta bottle help shift air to the sides of our body, not through the centre?

Thoughts appreciated, although I presume there will not be easy answers outside “go fly you and your bike to the nearest wind tunnel for testing.”
But the data/experience must be out there. Somebody had to have run smoke trails in the wind tunnel to see what effect it has on airflow. Or someone must have cfd modelled it.
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Re: Mantis position: what makes it fast? [Rocket_racing] [ In reply to ]
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Mantis doesn't change the A part of CdA, so *when* it's faster it has to work on the Cd part of CdA. In addition, not all angles seem to work for all riders; if it were as simple as filling the anatomical parachute, you'd think that steeper arm angles would be better than shallower angles. Perhaps over time we'll develop better intuition about what makes a particular change faster but I think for most of us we're still in the realm of measuring and measuring if you really positively absolutely want to know.
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Re: Mantis position: what makes it fast? [Rocket_racing] [ In reply to ]
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Re: Mantis position: what makes it fast? [Rocket_racing] [ In reply to ]
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Hmm, some good thoughts above.

Personally, I've come to think it has a lot more to do with interactions with the helmet/clothing than anything else. With advancements in skinsuit stitching/trips/panels on the arms/upper back, (along with the fact that only recently have triathletes had sleeves at all) and now with helmets being made "more forgiving" to having a slightly higher head, it sort of makes sense that it seems to work for "more" people than it used to. (albeit fashion also effects the number of people riding that way)

My Blog - http://leegoocrap.blogspot.com
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Re: Mantis position: what makes it fast? [RChung] [ In reply to ]
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By getting the hands in front of the head aren't you getting rid of some frontal area?
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Re: Mantis position: what makes it fast? [DBF] [ In reply to ]
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DBF wrote:
By getting the hands in front of the head aren't you getting rid of some frontal area?

No.

You're directing air around an equal area in a better way.
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Re: Mantis position: what makes it fast? [burnthesheep] [ In reply to ]
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I suppose you could say that your hips and lower torso are drafting behind low hands... but I wouldn't. If you can make the hands, forearms, head, and upper arms into one compact unit though... There should also be some advantage to minimizing gaps.
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Re: Mantis position: what makes it fast? [bloodyshogun] [ In reply to ]
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Great links. Thanks.

I really need to get to a wind tunnel. Maybe my next trip to england.
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