How To Build a Streamliner Part Two
How to Build a Streamliner
Warren Beauchamp 12/26/03
Overview Fairing Construction Step by Step  
Construction Techniques and Materials
Fairings can be constructed of anything from cardboard to carbon fiber. What you build yours out of depends on your budget, time constraints, and how fast you want to go. As in the previous page, I'll break down the methods into three groups, practical vehicle, club racer, and speedbike. The cheaper and less aero materials and techniques will be used on the practical bikes ('cause they don't need to go as fast!) and the more expensive materials will be used on the two zootier vehicle types.

Practical Vehicle
Suggested materials for building a practical vehicle start with your basic Coroplast fairing. Even though Coroplast (Coroflute in England) is a flat material, it can be bent in a direction perpendicular to the flutes. The 2mm thick variety bends much easier than the 4mm thick stuff. The 4mm Coro is much stronger. Also Coroplast can be bent at an angle to the flutes by evenly heating the area to be bent with a heat gun and then bending it. You cannot bend Coroplast parallel to the grain without causing serious wrinkling, but you can cut thin strips and cut them to approximate curved areas. Another technique to create a 1 dimensional curved surface is to slit just the inside of the flutes every inch or so. It has been noted that a fairing made from Coroplast is faster with the flutes parallel to the direction of travel. A practical vehicle will have a much higher incidence of surprise stops, so the chances of crashing, usually at very low speeds, are much higher than for a racing fairing. Coroplast is a great material for a practical vehicle because it is very crash resistant. Coroplast sections are usually fastened together with plastic wire ties but can be stitched with fishing line or glued with silicone glue. A supporting structure is normally made out a combination of 3/4" x 1/8" aluminum strap and aluminum or plastic tubing. ABS plastic water tubing and elbows work nicely but be aware that they become brittle in cold weather. Extra bracing is recommended. Aluminum 1/8" pop rivets do a good job of fastening the Coroplast to the support structure. Use steel pop rivets to attach the support structure to the mounting brackets, as aluminum pop rivets fatigue easily in these areas.

Other Materials
Other materials are Lycra, Zote Foam, or plastic sheeting. The Lycra used in practical fairings "body socks" is generally much thicker than obtainable at the local fabric store, and is sometimes rubberized on the inside to provide better weather protection. Lycra works well to provide a decent boost in aerodynamics, and is very practical in the fact that it can be removed and packed away into a small area. It is most effectively used in combination with a hard fairing to fill in the foot well and head/shoulder area. It can easily be attached with Velcro and adjusted with zipper to allow variations in ventilation. Lycra does not survive a crash well. As anyone who has ever crashed in bike shorts can attest, Lycra melts down pretty quickly when sliding on pavement. Zote foam has been used by quite successfully to build fairings. It is quite crash resistant, and much quieter than other materials. It is reasonable easy to work with, and can be blown or heat formed into aerodynamic shapes. Once it is shaped it is much stiffer and self-supporting than in its sheet form. It is fastened together quite well with rubber cement. Thin plastic sheeting such as Lexan or Vivak (PETG) can be used for the flat areas of the fairings, or the areas with 1 dimensional curves. Materials such as Cintra and Plexiglass are not recommended as they crack easily and may be dangerous in a crash. It's a good idea to paint or otherwise cover any clear plastic that you don't have to look through, as sunlight will cause the plastic to degrade. Also clear fairings make great solar cookers. A good way to test plastic is to hit a sheet held under stress with a hammer a couple times. If it cracks then it will probably not last through a crash.

Nosecones
The smoother you can get the fairing, and especially the nose area, the faster it will go. It's very hard to make a fast nose cone from Coroplast because it will be a conglomeration of flat surfaces. One way to get that smooth nose cone is to make or buy a blown bubble nose cone. Mueller Human Power makes a nice one that is based on the WISIL blown nosecone. They can easily be attached to a wide variety of recumbents. Properly executed, this in conjunction with a Coroplast body and tail section will result in a vehicle capable of being ridden at 25MPH for extended periods, and in most weather conditions. Another option is to build or purchase a fiberglass nose cone. Lightning makes one for their F-40.


Club Racer and Speedbike
Fairings for Club Racers and Speedbikes are constructed using mostly the same techniques. Generally these bikes are constructed of composite materials. Epoxy, polyester or vinyl ester resins are the most common "glue" to hold the composite layers together. Polyester and vinyl ester are cheaper but are stinkier. Most people agree that they are also more toxic. Epoxy, while less fragrant, is also toxic to some degree. Polyester and vinyl ester will eat most common types of foam. If you want to use these materials with a foam based mold, you will need to use special foams designed to resist these resins. Epoxy works fine with all types of foam. All these materials require the use of rubber gloves, protective clothing, and either lots of ventilation, or a respirator made to protect you from the specific material with which you are working.

Epoxy
I recommend West Systems epoxy. It is readily available, and is easy to mix with the available measured pumps. Epoxy generally requires a warm place to cure. The epoxy will cure at temperatures above about 70 degrees, but hardens better at higher temperatures. It cures quite nicely at around 90 degrees. You can get "fast" or "slow" hardener. The slow hardener is recommended to give you time to wet the material out properly and ad additional layers before the epoxy starts to "turn" or "kick over". It is important to mix the epoxy in small batches. Between 8 and 12 ounces works best. More than that and the thermal mass of the epoxy tends to allow it to "go exothermic" on you. You know you mixed too much when take a quick bathroom break on a warm day and return to see your plastic cup of epoxy spitting, smoking and melting down. It's also important to keep the curing epoxy out of the sun. Even dappled sunlight can cause bubbling or delamination of curing areas on the fairing. Keep plenty of popsicle sticks around for stirring the epoxy. Apply the epoxy with 2" natural fiber disposable brushes. Spread it around and remove all the air bubbles. Small air bubbles can be removed by poking them with a nail and then stippling with the brush. Rubber squeegees can also be used to help spread the epoxy out and remove the excess. You can either remove as much epoxy as possible without making dry spots, or vacuum bag the parts to make the even lighter and stronger.

Material Choices
Use layers of fiberglass, Kevlar or Carbon fiber depending on the fairing's strength needs and your budget. Carbon fiber is the most stiff but can break into shards when highly stressed. Kevlar resists breakage and abrasion to an amazing degree, which means it's an ideal material to build a fairing from, but it's very hard to work with. You will need to get special scissors to cut it, and because of its tendency to fuzz when sanded, it should not be used as an outer layer (unless you are not planning on any sanding). Use thin layers of foam or Nomex honeycomb core material at least " thick to strengthen the high stress areas of the fairing. If you are building a monocoque fairing you'll need several layers of cloth fiber surrounding the core to provide a rigid tub. If a thin outer skin will be all you need, then periodic foam or honeycomb ribs can be used to stiffen the fairing in the critical areas. 

Use of Existing Fairings
Designing the actual shape of the fairing is probably the most important single task in the construction of a club racer or speedbike. Many projects have gotten bogged down in this step. My recommendation is to either borrow the mold of an already existing and speed proven streamliner, or to copy the design of a proven streamliner. Note that many streamliners, such as the Varnas are constructed for individuals under 6 feet tall. If you are taller that that you will need to use a fairing specifically designed for a taller person. Currently molds are available for use from the Varna, Moby, Barracuda, Lightning X-5, WISIL Missile, and probably some others.

Nicholas Cafarelli proposes that a good fairing can consist of a lathe produced body of revolution spliced to a wedge. The top and bottom of the fairing are hot wired as one piece in a hotwire lathe, covered in one piece and sanded by modifying the lathe with a sanding attachment. Once a high level of finish is produced, a router is used to produce a joggle and to section the body of revolution. Now imagine a wedge interposed between the two parts. The wedge grows in height from nose to tail. This wedge is quickly produced with a standard hotwire using the two lathe cut parts as templates.

Fairing Design Tips
If you really must make your own or think you have a "better idea", be sure to follow some guidelines: No sharp transitions, no "planes", and no flat spots. Make all curves flow into each other. Don't make a knife edge nose. Keep the shape as monolithic as possible. Use "lofting" techniques to help make the curves. Build a scale template of the rider and a mock up of the pedal configuration to determine the foot clearances, knee clearances and shoulder clearances. You can model the fairing however you want, on paper, in CAD, or out of clay. Just remember that you will be converting it to full sized templates eventually to create a male mold. If you are a CAD guru and want to have the shape CNC milled, that's great, just remember CNC milling for such a large object is extremely expensive and hard to come by. Note that if your fairing is left-right symmetrical, you only have to make half a plug!

Plug Construction
I recommend building your male mold from foam. Pink or blue 4x8 sheets of 2" polystyrene insulation foam are readily available from building supply retailers. This foam should be used with epoxy only. Foam for use with ester-based resins is available from aircraft supply retailers. Fairing shaped sections can be cut from these sheets and glued together to make a rough form. This form can be further shaped using hot wire techniques. Further smoothing can be done with a large rasp file and then sandpaper. Once the shape has been approximated, templates can be made to check the critical areas of the plug against the desired shape. Areas can be built up using drywall compound or an epoxy/micro-balloon slurry. Once the desired shape has been attained, the plug can be covered with a couple layers of 8oz fiberglass. After curing, sand and then cover in epoxy based aircraft filler or bondo to fill in the low areas and pinholes. A long steel straightedge can be used to help find and fill the low areas. Mount at least a 2 foot long strip of sandpaper (belt sander paper works well) onto a 2x4 or other flat surface to sand down to the high spots. Alternatively the whole plug can be sprayed with a thick layer of high bulk primer and then the fairing can be sanded down to the high spots. At this point the process of smoothing, checking and refilling continues until you are satisfied. Cover your mold with final layers of primer and finely sand it. Cover the mold with 3 or 4 layers of Carnuba wax. Apply a thick layer of mold release agent. Now it's time to lay down some fiberglass! Note that you will want one or more friends to help with laying up and wetting down the fairing. Drape and wet down each layer one by one as the epoxy won't soak through multiple layers of fabric at once. Don't allow the previous layer to cure before adding a new one. The fabric layers after the first one will be harder to drape and smooth out, as it can't slide around on the wetted out layer below it. Be sure to have some scissors around that you don't care about to cut slits in the unsmoothable areas. As much as you will be tempted, don't use patchwork of materials. Unless you really like to fill in crevices and holes, each layer should be a single sheet of cloth. If you are going to use a female mold you can only have to make the outer layers out of a single sheet.

Molds - Good, Better, Best
Now it's time for the decision of what to do with the plug. There are 3 methods.

1) Lost mold technique. - In this scenario you decide you've had enough. To just make the fairing, just cut the canopy section off and then remove the foam from the plug. This is easy, but makes it harder to replicate your fairing. Also the fairing is likely to be heavy because of the filler materials.

2) Male plug molding - Cover the male plug with mold release agent, then drape the fabric directly over the mold. It's best to do half the mold at a time to make it easier to remove the part from the mold. Care should be taken to remove the bubbles between layers and to squeegee out excess resin. This works well but requires filling and finishing the outside of the fairing after curing to provide a smooth finish. It's not recommended to vacuum bag on male molds, as the peel ply layers will mar the surface of the fairing.

3) Female mold - Cover the male plug with mold release agent. You can use a layer of fiberglass then thick layers of chopped fiberglass together with wooden ribs to make a sturdy female mold. Note that removed objects for molds may require a lot of force, so build it a bit on the heavy duty side.  For asymmetric fairings you'll need to build separate left and right half molds. For left-right symmetric fairings only one mold is needed. Even with the best wax job and mold release agents, it may be hard to remove the male plug from the female mold. Copious use of wooden wedges, Coroplast strips, hot water, and elbow grease may be needed to remove it. Once the female mold has been freed, it may need some minor touch up. Then it's time to wax it up and apply more mold release agent. Female molds work nicely because when the final fairing part is pulled from the mold, the outside surface is already finished. Also it makes vacuum bagging easier.

Vacuum Bagging
Vacuum bagging involves laying up your fairing, covering it with a layer of "peel ply" and then another layer of "bleeder ply". The uncured composite conglomeration is then sealed with plastic, and a vacuum pup is attached. As the air is evacuated it evenly squishes the composites together. The excess resin is forced through the peel ply into the absorbent bleeder ply. The vacuum remains on until the epoxy is partially cured, keeping the layers of composite material compressed together. The entire mold can be heated to speed this process. You can lay up multiple layers and then vacuum bag them all to create a well-integrated, strong and lightweight fairing. Once the resin has cured, the easily removable peel ply allows the peel and bleeder plies to be removed from the inside of the fairing.

Fairing Integration
Once your fairing shells have been completed, Often the right and left halves need to be attached together to form the whole fairing. Once the shells have been cut to align properly, the shells can be fastened together temporarily with tape, or with strips of fiberglass screwed across the seam. Once that is done the fairing can be cut to separate the actual canopy or upper and lower sections. This allows access to the inside, which is where you will do most of the work to fasten the shells together. You can use fiberglass or carbon fiber tape, along with a slurry of cotton flox and epoxy to fasten the shells together on the inside, and to fill any gaps in the seam. Be sure to leave enough room to get the bike or sub-frames in and out, and plan how you attach it so you can easily install and remove it. If it takes a long time to remove it will be a real pain to change a tire or perform maintenance. If you are concerned that the fairing may not be aligned properly, you can make a frame out of particle board for the fairing to sit in that has the same profile as the fairing at the canopy cut lines. Particle board is the best choice for this as it very flat and doesn't warp easily. The frame will support the fairing while you are working on it.

Canopy Considerations
Another important aspect of the fairing is the canopy. In your design be sure to think about how it will attach and if you will use a head bubble or make sections of the main fairing clear to see out of. Many streamliners use a piece of flat plastic cut to fit the curved front and sides of a fiberglass canopy. This makes it much easier to replace when it gets scratched.

Attaching the Chassis
After the fairing shell has been completed, you'll need to attach it to the bike frame. It should be a solid attachment, as wind blowing the side of the fairing will push the sides of the wheel openings into the tires if it's not attached well. Usually a three-point attachment works well. One attachment in the nose, one under the seat, and one at the rear wheel usually suffices. The attachment at the nose is usually the most difficult. Typically it involves a bracket on the boom tube or bottom bracket, supporting a T shaped bracket, with the ends of the Ts firmly attached to the inner sides of the fairing. Placing the bracket behind the pedal box is best because the top of the T can be below and behind the pedal box without interfering with the pedal stroke. Placing the T in front of the BB can make the bracket subject to high stresses and premature failure. Remember when making these brackets that they will be subject to a lot of vibration. An aluminum bracket will need to be pretty beefy or after a couple hours of racing/riding on a bumpy track/road it will fail due to fatigue. The bracket under the seat will need to be pretty beefy too. You may need to stand in the bottom of your fairing to get in and out of it. The rear mount is the easiest, as it normally just needs to prevent the tail of the 'liner from wiggling around.

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