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25 Jul 2011

Coroplast 'shorty' TF

My Pioneer is a great 'bent. It does just about everything. That's the reason I choose it to ride to Spezi with. For longer distances and headwinds there is a problem though, it's not that fast. Compared to what I'm used to, what my 'standard' is, it's slow into a 4Bft. headwind.

Coroplast is a nice material, but almost completely unknown in the Dutch recumbent world. In the English speaking world, it's used quite often. On the CV2011 campsite, my tent was pitched near Fards' tent. And, one we the things we talked about, was the 'magic' material. I'd already found a Dutch website selling it, but during CV the decision was made that I'd do something with Coroplast. You could say that Fards ignited this project.

First I thought making something for the Q451. However, that already is a quick little bike. The Pioneer is the bike that could use less drag. I ordered several sheets, and tried to think not too long about the high shipping costs of the large sheets. I know had them in black, which looks cool.

First I made a cardboard template for the back panel and the floor. The floor would rest on the luggage rack. The back panel would have a widest point of 46cm, matching my shoulder width. I cut the panels and bent flaps under a 90 degrees angle, using a hot air gun. Pop rivets with little washers kept it together. Than I could add the sides and cut those to size. I lowered the stress on the joints by heating the curved surfaces. The edges where sealed with Tesa Power Tape. You can also use hot glue to join it.

It looks alright, not a pretty one, but stalwart. It held in place with only 2 bolts, near the bottom of the seat. I kept it relatively short in order to make it easy to store in the shed. Normal sized TF's are sort of bulky.

The first thing I noticed during ride number one was how silent it is.The first ride was to the hairdresser, so I didn't do any tests regarding the aerodynamic qualities. It did give a hint of an advantage.

That evening, I went out for a ride. Curious about how good it would be and just to ride. After 15 minutes or so the idea came to do a simple roll out test. Here's what I did on my test location.

  • accelerate to 40kph
  • coast down to 30kph
  • measure how long that takes in seconds
  • 2 times, return run, that's 4 runs
  • repeat without TF.

The method is not very precise, not at all. But, the results, which I had to memorize, where clear and consistent enough to conclude that the TF really works. Without the box, it takes about 11.5 seconds to get from 40 to 30. With box, it takes about 13 seconds. If I than hustle the results a bit, trying to be as negative towards my own design as possible, the TF gives at least a 7-8% advantage. And for such a short TF, I find that's very good.

When I rode to work last Friday, the advantage was very welcome. A strong head/side wind, and still I could keep going at 29kph or so. For less than €30,- and a short day of work, I'd made my big practical Nazca significantly faster.

1 comment:

  1. The proof is in the pudding.
    Ivonne had made something similar on the trailer for her dog on CV.
    Regards, Mick

    ReplyDelete