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More on aeroI just ordered a Mueller GX fairing for my P-38. The Mueller folks told me that I would get as much aero improvement form the lighter XT model -- but it wouldn't give me as much wind protection for my legs and upper body. Since it is already getting cold in NY; I went for the heavier GX model. I'll post a report after I install and test the GX. Mueller claims about a 5% speed improvement with either the XT or GX models. This seems pretty modest; but consistent with some other articles I've read, which assert that front fairings are more effective on LWB's, and less effective on SWB's like the Lightning. If I recall correctly, this article claimed that a rear fairing or tail sock was more effective on SWB's. Does anyone have an opinion or experience with rear fairings on a Lightning?
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tailbox on Lightning P38
Some more random impressions:
1} Keep us posted on your experience with the Mueller fairing.
2) I home-brewed a Coroplast tailbox for one of my Lightning bikes. It was useful for storage, and looked kind of neat. But the tailbox by itself did not seem to do anything for me speedwise. It did not slow me down though.
3) The tail fairing DID help when it was connected to a front nosecone and middle section fairing, forming a homebrew F40 style fairing. But the bike was also very fast with just the nosecone and middle section, minus the tailbox. Adding the tailbox only helped a little bit more than the nosecone and middle section alone.
4) I think that Paul W of Australia recently created a tailfairing for his P38 bike, using an aluminum framework covered by fabric. There are pictures of his work in the gallery section of this website. The finished results look great! Unfortunately Paul's work did not seem to produce good results in testing.
5) The stuff you read about front fairings on long bikes versus short ones might be true when we are talking about Mueller and Zzipper fairings, but does not hold true in general. The Mueller and Zzipper bubbles allow the rider to tuck in close to the fairing when used on long bikes. The mounting of the fairing is also easier / cheaper with above seat steered long bikes like the Easy Racers and RANS bikes.
With a P38, the rider is farther away from a Zzipper or Mueller front fairing. I think this is the main reason for decreased effectiveness. Use a front fairing that reaches back farther and the results should improve. But this means building something yourself, or possibly trying to adapt a Rotator Pursuit fairing to a P38. And Rotator Pursuit fairings are not so easy to come by, especially now that Steve Delaire has left the recumbent bike building business.
The F40 fiberglass nosecone by itself will certainly be an improvement over the Mueller and Zzipper fairings. But it only really does its stuff properly in concert with the middle and tail sections.
6) There are some books about building canoes out of Kevlar and carbon fiber cloth that might be useful for recumbent bike fairing builders: one is by James Moran (Building Your Kevlar Canoe, 1995) and a more recent one is by Sam Rizzetta (Canoe and Kayak Building the Light and Easy Way, 2009). I am reading these books myself, and might try to create something over the winter.
7) I do not think stand-alone tailboxes really have much to offer in speed improvement. One possible exception: if you build a tailbox that is really large, and tightly coupled to the rider's body, it could be worthwhile. I am thinking of the sort of tailfairing used on the Birk Comet recumbent, a very expensive Swiss bike. You can find some pictures of the Birk Comet tailfairing by poking around at www.speedbikes.ch
8) If you are on a tight budget, making a full fairing out of Coroplast is probably the best way to go. If your pockets are a bit deeper, buying a ready-made F40 fairing makes sense. The stand-alone tailbox does not appeal to me, at least in terms of cost/benefit ratio.
Safe riding,
Joel
more on aero
Joel - thanks for all of that useful feedback. Here is a picture and detailed description of the Mueller GX on a Lightning: http://www.mueller-hp.com/lightning.htm. They called it an F40; but I think they meant that it was P-38 frame with F40 installation tabs on the BB. As you can see from the photo, that unlike their smaller XT model which bolts to the front derailleur mast, the GX can be mounted quite close to the rider and give full coverage. The interesting thing is that Mueller claims that you can get the same aero benefit from the XT as the GX. Other forum members have posted positive views on the XT as well - especially it's light weight and low cost. I was tempted; but NY winter is just around the corner, and I opted for the GX despite doubling the cost and weight of the XT. My GX is shipping from CA on Mon. My guess is that I wont get my hands on it for at least a week after it ships. It may be awhile before I can post my review.
Bob
Mueller and Small Zzipper fairings
I think the approach the Mueller Windwrap and small Zzipper fairings may be flawed. It seems to me that what needs to be faired is not the face or hands, but the feet. I think this for three reasons.
(1) On the P-38 your feet are presented sole-first to the wind, they move all over the place creating turbulence, and that turbulence is advected downstream all over your body.
(2) Fairing the handlebar/hands and face leaves a lot of length exposed to the wind. Remember that longer sailboats are faster than shorter ones. I think the same principle works with a wind fairing. You want it farther forward to take advantage of the full length of the bike. A nose-cone-like fairing that covered the feet through the entire rotation of the cranks would create a wake that would cover the entire length of the bike.
(3) A foot-fairing would not need to be transparent. It could be made of carbon fiber and be extremely light. Plus you wouldn't have to worry so much about scratches.
Both the Mueller GX and XT
Both the Mueller GX and XT fairings cover the feet on the P-38. See my recent review of the GX. I'll post some pictures in a few days.
more aero musings
1)"Advected downstream all over your body". I am impressed. I have never run across the concept of advection before in discussion of bike aerodynamics. Yeah, the feet churning around while pedaling have got to dirty up the airstream, so covering them fully has to help. The smaller Zzipper does nothing about this, just covering the upper body.
2) I think both Mueller and Zzipper tell riders to adjust the fairings so that you see OVER THE TOP of the fairing, not through it. You do not want compromised vision caused by looking through a compound curved piece of Lexan plastic. Since you are looking over the things, whether it is opaque or transparent should not matter. I guess the transparency is more about looks / marketing than function. Some Zzipper and Mueller owners paint the insides of their fairings making them opaque.
3) From a purely commercial standpoint, blown Lexan is probably the smart way to go. The plastic sheets are cheap, and the oven used to blow the bubbles is also cheap/easy to construct. The real cost is in slowing learning to do everything right so that you end up with nice fairings instead of melted plastic junk. The mounting pieces also have to be expensive if made in small quantities. There is a good article about this on the WISIL site. A number of streamliner builders have built similar ovens to create head canopies out of Lexan. Making something out of fiberglass, Kevlar, or carbon fiber cloth is significantly more expensive and labor intensive.
If recumbent riders in general are in the cycling avant-garde, then recumbent people who put fairings on their bikes are even more outside the mainstream. We are in the vanguard of the vanguard.
If you are custom-building something just for your own use, none of this matters. But someone thinking about selling stuff has to worry about it.
4) I know almost nothing about aerodynamics. Even a simple-minded empiricist like me can see that the more fully you fair, the faster you go (at least on the flats). The little handlebar-mounted Zzipper is intended as a compromise. Even the F40 fairing keeps the rider's head uncovered for better vision on the road and better cooling in warm weather.
5) I once tried riding my homebrew F40 clone with a full head canopy made of plastic. I quickly learned what a strip of bacon feels like while being fried. Many people who race streamliners install NACA ducts for ventilation. These are the same sort of ducts that you see on race cars.
6) I have put an old article written by Tim Brummer titled "Lightning Progress" on the home page of this site. It is well worth reading for anybody interested in these issues.
Safe riding,
Joel