Fairings! Does anyone use Fairings!

[benphyr]

I used SolidWorks for the modeling. Using surfaces first, then converting them to solids is easiest and gives the most design flexibility. There is a CAD program called OnShape that may be similar but has a free version. Actually Powerpoint or similar presentation programs are useful for overlay and scaling purposes. Accuracy is about +/-.5" (13mm) for this application in Powerpoint. I did a test wet carbon/epoxy layup on a rounded block of foam and was very happy with the finish after all sanding, polishing, and two coats of car wax left it silky smooth. I followed this video suggested method:

from Easy Composites Ltd. I am using West System epoxy with 207 clear hardener available locally.

Once the fairing model surface was generated (revision 13...), a model solid was made and I carved out the middle of the model to reduce foam shipping weight. I sent a STEP conversion file format of the file to a company that does 3D EPS foam milling (as well as any other foam work you can imagine). The vendor milled the right side and the mirror left side. I could have shaped the foam by hand with templates but life is too short so I had it done quickly and exactly to the model.

I am purposefully avoiding a full streamliner design. The primary objective is to be very careful with the airflow in the front 1/3 to 1/2 of the bike to maintain near-laminar flow. The fairing drastically reduces/eliminates parasitic drag in the front of the bike. As airflow leaves the fairing then it is a normal bike and rider with the exception that the bike/rider is still in a nearly undisturbed flow state (drafting the fairing) and there are no further glaring new airflow obstructions except the great big head and helmet. With the exposed flow over the body I can get cooling in the hot Houston summers and should also have the flexibility to start and stop like common road bikes. I will chop away at the fairing until that is the case. A limited streamliner reduces weight and skin drag at the cost of higher turbulence in the aft sections of the bike, compared to a full streamliner. Also I am a 200 lb small boat sailor, so I do not mind getting blown around if that is what this design does in a breeze. The two articulating side panels at the hips will be interesting. I am using 3D PETG printing for special joints and hinges. We will see, one step at a time.

Hi Bill,

I don’t know anything more than a little reading and riding in the wind so take this question as from an untrained source.

How have you addressed cross winds? Does the design incorporate balancing side wind loading and steering in some way?

 

[Bill Wightman]

Hi Bill,

I don’t know anything more than a little reading and riding in the wind so take this question as from an untrained source.

How have you addressed cross winds? Does the design incorporate balancing side wind loading and steering in some way?

I won't do anything unless it is a real problem. If it is a problem then one way to reduce side loading in gusts is to place trip strips or vortex generators along the top and the bottom. As the gust flows over the top and bottom the air close to the skin is given spin which stabilizes the flow and prevents it from forming large oscillating patterns that generate large side loads. The sharp peaks you see on the hoods of some SUVs do the same thing so you don't get pushed all over the road on a windy day. Anyway, you would be surprised how much you can actually anticipate a gust and compensate just as it is hitting you. This comes from small boat sailing experience and feeling the pressure rise and fall on the face and arms.