Feb 23

Feb 23, 2005

Position, geometry and fairing ideas

After a 5 hour inside ride on the M5 yesterday, I am finding that my feet go numb after about 50 minutes. The problem is caused by my feet being at a higher elevation than my heart. Although the M5 seat and bottom bracket are higher compared to the rocket lean steer trike, the relative position of the BB compared to the seat bottom and seat top is much higher. The position is WAY more comfortable, but results in poor blood flow to my feet.

I found that if I single leg peddled for about 5 minutes each leg per hour, that the feet would be good for about another 45 minutes. I'm not sure if training will improve the situation or not. Looking through the internet for ideas, I found that someone solved his numbness issue by sleeping with his feet elevated a bit in bed.

I tried lifting my seat bottom up by sitting on various cushion sizes, and they seemed to make it a bit better, but not totally. The very best position was the seat bottom 6" higher and the seat top 1" higher - this still resulted in numbness, but the position felt very good - the best in fact. I think if I got still a bit higher it might solve the numbness issue.

The problem with a higher seat, or course is a larger fairing to cover everything, and that results in higher wattage output to maintain the same speed, which would result in additional discomfort. Everything is a give and take!

My 150 watt heart rate is down to 110 which is very good. When I started training on the Rocket in the summer, my 150 watt HR was 120. My 200 watt HR was 130.

Here are some ideas using the NACA 6014 fairing (non-proportionately scaled in every direction) that would cover a higher upper body position:

NACA 67014 LWB front view

The last SWB that is 124" long is probably the best so far. It leave a very small area of both the front and rear wheel to fair. Problems with it are that to fit my shoulders in, the width has to be 26" wide and it's 31" tall which is fairly large - lots of surface area - big 'A' in the CdA.

And this final fairing may be the best. It's the 67014 that has been set at a negative lift angle of attack. This could be the same as cambering the airfoil as Goro says in his book. The obvious problem here, is that this isn't really a true camber, it's just tilted. I'm not sure if it would actually produce weight adding negative lift or not - might be worth CdF testing some variations of this concept...

Compare it to this concept that shows a very balanced fairing that is only 20 inches wide and probably 20" tall

Rocket Racer to do list

1. Everything!

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