Getting Aero - Speed Gains

Guess I will weigh in here. There are fairings then there are aerodynamic fairings. Anything that reduces drag is a benefit of course, but unless one has access to advanced programs, a wind tunnel or both a design can be a crap shoot. Looks slick doesn't necessarily=slick. The holy grail of aerodynamic shape is one that separates the air, keeps it attached to the shape and puts the flow back together with no turbulence, a tall if not impossible order. A Cd of zero.
All that said I think a faired bike is an interesting idea. A recumbent would be the best choice to reduce the size of an upright bikes cross wind flat plate, though I think maybe a more efficient fairing could be built for the upright. The flowing air has to be accounted for over the bottom as well as sides and top. The bottom is where most fairings lack. A trike off the get go is going to be harder to achieve a low Cd with just by the shape.
In the real world a practical vehicle probably isn't gonna get real close on the low Cd arena, but surely the benefits of a decently designed shell will increase efficiency of either pedal or motor drive as well as add weather protection.
Being a avid aircraft restorer I would favor a fabric design. Very easy to fabricate in almost any shape, weather proof and properly built just about the lightest and most economical method out there. And with decent finishing skills, very slick.

cannonball2 said:

...Being a avid aircraft restorer I would favor a fabric design. Very easy to fabricate in almost any shape, weather proof and properly built just about the lightest and most economical method out there. And with decent finishing skills, very slick.

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I've played a bit with Dacron covered ultralights (owned a Quicksilver MX) & while it's good stuff, you're perhaps familiar with industrial shrink wrap products such as these: https://dr-shrink.com/

I've used it rather a lot in the marine industry, not that particular retailer (example) but it's the same group of products, including tape, zippers & even louvered vents. Light, durable, strong, easily repairable & best of all cheap, it does require at least a light framework & isn't puncture resistant, ofc.

I've also had some experience with geodesic airolite boats similar to these: http://gaboats.com/boats/ while those do use Dacron: http://www.aircraftspruce.com/categories/building_materials/bm/menus/cs/dacron.html the shrink wrap is far easier & cheaper to play with, the ultralight boat's internal hull structure plausible as a basis for a velo, with a nice slippery shape;



Being that an areoshell isn't load bearing, it could be constructed out of little more then 1/8" ply stringers, gussets & epoxy - the entire structure likely requiring no more then a 1/2 sheet of ply & a 12'x8' bit of wrap & a chunk of clear plexi ofc... if one had access to cut offs, it'd be a $20 to $40 project or thereabouts, time not included lol

The shell on the bike in the pic LR posted could be built fairly easily with the wood bulkhead/stringer method.

You are right Barely, shrinkable plastic is another good alternative. If you remember the Lazair ultralight it was covered with Tedlar, also a clear shrinkable plastic. It was tougher than most. Don't know if its still made. The advantage to even light weight Dacron is its pretty tear resistant and easy to shrink to compound curves, plus finishes nicely.

Have to agree LR has a point about breakage of a super light stringered structure. Hard points could be added at suspected contact points.

I made my daughter a fabric kayak from left over scraps from a resto project. It weighed 12lbs with a hard ply bottom. She still has it though its too small for her now. Is a really pretty wall hanger. Cool thing about this building method is if one works efficiently a shell can be roughed out in a good day once the shape is laid out.

I don't think I would build with less than 1/4" stringers if using Dacron or another highly shrinkable material because of deformation. 1/2" could be used even with out much weight penalty.