Streamlining - aka beating wind resistance

[mylittlepony]

I've been gathering performance data pretty carefully for my first bike despite the fact I don't have a wattmeter or CA. So far I'm amazed at the potential efficiency, doing some rough calcs I reckon I'm getting the 'E' equivalent of maybe 3000mpg! Don't quote me - I could be wrong

So anyway, the one thing that stands out is how power requirements soar as you increase your speed. It must be something like:

200W @ 15mph
500W @ 20mph
1600W @ 30mph
2100W @ 40mph

What is it power is the cube of speed? That's an awful lot of energy wasted pushing air out of the way, you can really feel it above 20mph. Above 30mph it starts getting chilly in a t shirt.

Ok so nothing earth shattering so far. Its all obvious. Lets face it a MTB & rider has the aerodynamic properties of a brick. Even a fully faired modern sportsbike is pretty draggy, 140mph on my Honda feels like the wind is going to tear the leather off your back. So then I'm reading about the high speeds people get from HPVs/velomobiles/streamlined recumbents. It seems a reasonably conservative semi faired recumbent can do 30mph with just the rider pedaling. So if the rider of one of these is putting in 200W then they're doing twice the speed of my bike for a similar power input. Cruising at 30mph on less than 500W would mean awesome range and efficiency!! 2100W would = insane speeds. The added benefit is nobody can see you're not pedalling

I've seen plenty of tadpole bents but nothing with a fairing, I think a taddy would be the easiest to build a fairing onto. I'd like to know what sort of power vs speed requirements the lads with taddies are getting. However I'm leaning towards a 2 wheeled bent because I would feel too low/vulnerable on the road in a trike.

So I want to know if anyone on ES has built anything like this?

 

[veloman]

Fairings are a tough deal on bikes, period. I am going to look into adding a small, scultped front fairing to my mtn bike, but it's questionable. The best bang for your buck and a ton of other non-hassles = aero bars and tight clothes. I will try out putting my aero bars on, will only use them on the flat long stretches. IMO, you need two positions on a bike. A city, low speed position that gives you comfort, visability and handling. Then you need an aero high speed position to reduce power consumption or increase speed when the road opens up and you don't have cars and people darting at you, stops, corners and bumps.

Look at my latest build. I'm able to go 28-30mph on about 650watts. It's near road bike efficiency when you factor in the 80% motor/controller efficiency.

 

[TylerDurden]

GeeBee built a full velo, but his build pix are "not found" when I traced the links through bentrideronline.

 

[LI-ghtcycle]

Not sure about any here with full fairings on two wheels, but I am definitely going to have one partial one on my recumbent, I had so much fun with a partial one on my Tidal Force E-MTB!

The main concern for me is practicality, I want efficiency, but not at the price of comfort or ease of use, and with a recumbent you really gain so much just from the more stream-lined seating position, that you gain a huge amount even with out a fairing, so at first, I was tempted to go with-out one, the problem there again for me, is I want all weather (with in reason of course, not expecting to ride through two feet of snow) capability with reasonable comfort.

That means for me I want to eventually figure out a good compromise between the protection of a velomobile, and the open air of a partial fairing (I don't want the greenhouse effect) mainly some kind of rain protection that is still reasonably aerodynamic.

The biggest thing I noticed is the lack of effect that head-winds had on me once I started using my Zzipper '88 MTB fairing. Take a look here, and under testimonials, there I am "Dayn's 88 MTB fairing" with a paragraph of my review I listed here on ES:

http://www.zzipper.com/

Karl is a very neat guy, and I've been very happy with his product, for me, a big plus of a fairing like his is you can take it off with 4 wing nuts, roll it up and stow it for a ride on the buss/train in 5 minutes and it's very easy to re-attach.

He's been in the business since the 70's and has a wealth of experience building and testing various designs.

 

[mylittlepony]

Lightcycle: I'd certainly like to see your bent with the fairing once you get done.

With a view to gathering some data on the subject of efficiency I've created a survey over here Power vs Speed Analysis

Using the same data I've also created a fun Top 10 Fastest, Most Powerful bikes Leaderboard.

Unfortunately its a little quiet over in the Surveys and Polls section of ES

 

[LI-ghtcycle]

Wow, I didn't even know we had a poll or survey section! I'll have to see if I can dig-up some info to post.

This is the first day in about a week I have been feeling up to much, so I will prioritize finishing pedicabs first, but I should have something to list tonight or tomorrow.