Alan Arial's Building Fabric Wheel Disk Covers for a recumbent bike

Fabric Wheel Disk Covers
By Alan Ariail 03/28/03
I've recently started using fabric disc covers. When I got the RazzFazz, Denis Ahrens had included plastic spoke disc clips with fabric disc covered wheels. Very lightweight stuff that incorporated fiberglass and aluminum rods. A couple minor problems I discovered with the plastic spoke clips used to secure the rod to the rim were that it was very difficult to get similar replacement clips in the US. and that the plastic clips had a tendency to leave a open space between the rim and disc cover. I decided to make clips that would allow the disc cover to fit snug on the rim and reduce the air gap space.
The first step to making disc clips is to cut strips of tin roof flashing to a width that will fit between the spokes of a wheel.
	After multiple strips are cut, each piece is bent over the rim to get a curve shaped the same as the rim. While holding the tin strip on the rim it is necessary to mark the area of the strip where the rim flattens for the brake surface. After all the tin is bent, you will need to build the wood form to create the fiberglass or carbon clips. You'll need:
1 strip of wood that is the same width of the wheel rim by 12" in length. 2 pieces of thin plywood the same length as the as the wood strip with 1" more depth. The pieces of plywood will be screwed to the wood strip and used as removable sides. 2 strips of double sided carpet tape to secure the bent tin in place. 2 pieces of thin ABS plastic, tin or cardboard the same size as the main strip of wood. These 2 pieces are spacers that make the clips slightly wider than the rim and provide a space for the fiberglass rods to fit into.
	Adhere the carpet tape to the main section of wood. Next, secure each strip of tin to the tape with the flat marked area of the tin lining up with the top of the wood. When all the tin is secured place, add the spacers on the sides and then screw the 2 pieces of plywood to keep everything in position. You will need to cover the tin and plywood form with a layer of thin removable packing tape. Once the form is taped you can then lay-up strips of wetted carbon (CF) or fiberglass (FG) and either vacuum bag the from or press some soft foam against the CF or FG and tape or clamp the form until the CF or FG cures.
This drawing illustrates a piece of soft foam placed on top of the wet carbon and then compressed into the foam with a piece of wood that is taped or clamped into the form. Removing the cured CF or FG from the form is easy as the side panels unscrew and the piece can be separated from the tin form with a screwdriver.

You will now have a long strip of wheel disc clips that are the shape of your rim. Just cut the strip into .25" wide sections that are .25" tall on the side. Use some fine sand paper to round off sharp edges and place a piece of double sided carpet tape on the bottom of each clip. The tape is what will keep the clips fastened to the rim. It is not a good idea to epoxy clips to the rim as the epoxy will eventually loosen. The tape and pressure of the fiberglass rods is enough to keep the clips positioned on the rim.
The next step is to make the fabric disc covers. I purchased supplies from: www.kitebuilder.com The cheapest rods are the .125" fiberglass rods (item RSF1272) in the 6 foot length as 559 rims require nearly 6 foot length. Steel ferrules (item FMT125) are needed to hold the ends of the rod together. I've been using .75 oz weight Ripstop Nylon fabric as the lightest weight had a tendency to wrinkle quite a bit and was not durable enough to sustain metal debris contact. Be sure to order plenty of extra rods as it may take a few rods to get the correct length for a snug fit onto the clips.
	When the clips are taped to the rim you can begin to push the rod into all the clips and mark the intersection point of the rod with a marker. ! Be sure to wear gloves while handling the fiberglass rods to prevent damage to your fingers from either fiberglass friction burns and splinters. When both ends of the rod have been clean taper cut, the ends will then slide into the ferrule. I have discovered that if I create a slight bend in the middle of the ferrule that less pressure will be placed on the ends of the rod and this limits the chance that the rods will split or fray as they have a continual gradual curve to follow.
With a very sharp razor cut the excess rod while rolling it back and forth under the pressure of the razor blade. Then cut a clean edge taper on the end of the rod so it will fit into the ferrule without splitting apart.
	Now that the the rod OD is set, you can lay the rod on top of the Rip-stop fabric and draw a line on the Rip-stop that is several inches lager in diameter than the rod. Cut the fabric on the line and when finished fold over about an inch of fabric to create a sleeve for the disc string to run through. A sewing machine will be needed to sew the folded Rip-stop fabric. After the edge sleeve is sewn a small hole will be cut on the edge and this is where the string will be threaded.
To thread the drawstring I taped a string to a semi-circular thick aluminum wire and fed the wire into the small hole while pushing the fabric sleeve over the wire. Eventually the string will go through the entire sleeve. Carefully push the wire out of the sleeve hole and be sure to leave excess string before you cut the string from the wire. Now you will center the fabric under the rod and gradually tighten the string until you get it very tight. Knot the string several times and cut the string leaving about an inch. Wrap the string ends with carpet tape to prevent the string from fraying and loosening.
	Before placing the fabric disc in the clips you will have to cut a center hole. Measure the OD of the wheel hub with a circle template. Draw the circle on the center of the disc and then use a razor to cut it. As a precaution to prevent the Rip-stop material from fraying at the hub you can tape a circular piece of Rip-stop to the inside center of the disc with carpet tape and then cut the center hole. The carpet tape in addition the other piece of Rip-stop on the interior will strengthen the center cut hole.
The disc covers should look similar to the pictures below when finished. The wrinkles in the fabric do not reduce the aero benefit. The purpose of the fabric disc covers is to provide an easy solution to reduce spoke drag. I have noticed that wheel sides with less dish have less wrinkles.