One of my first composites projects was trying to make wheel pants for the WAW. The WAW has exposed front wheels for smaller turning radius and easier wheel/suspension maintenance. Wheel pants covering the wheels and wheel well will improve the aerodynamics, but also creates a larger turning radius.
On my first attempt I was designing the wheel pants effectively as a large bump over the wheel well, and to not be 4 feet long. I also was far more nervous about actually molding directly on the body of the WAW. I was afraid of the resin not releasing completely, maybe damaging the gel coat of the WAW.
I attached yarn pieces on the side of the WAW and did some roll down tests and a video. I wasn’t happy with how they came out, didn’t make an appreciable improvement to average speeds.
For some reason I also decided to make these wheel pants extend lower than the body; ostensibly to make the wheels themselves more aerodynamic. This made things worse; instead of a narrow 1.25″ wide wheel going through the air, I was pushing a 4″ wide piece of carbon fiber instead:
This design also made accessing the inflation valve very difficult, so I added those little cutouts on the outer side. And this design required a two part mold…… I moved on to other projects and tossed out these molds 😦
And then my “inventory” of velomobiles changed. My friend Dan also rides a WAW, and unfortunately while out on a ride in his WAW a car driver decided to turn across the road, right in front of him. Dan was traveling too fast to avoid a collision with the car.
He was unhurt, but his WAW was now in serious need of renovation and repair. This was actually the third time WAW #256 has been hit by a vehicle (as a testament to the safety of velomobiles, no injuries to the Velo rider in any of those accidents).
The first accident (the first owner of WAW #256) crunched the nose cone in; it was a slow speed accident, but it’s a good indicator of the benefits of carbon fiber/Kevlar mix. It now features on the News page at Katanga.eu, the manufacturer of the WAW. https://www.katanga.eu/wp-content/uploads/2016/05/batmobile1.png
So, long story short, I sold WAW #239 to Dan! One of the sale conditions was that I would have access to WAW #256 before it went to it’s new owner (who will be restoring WAW#256). It was still in the back of my mind to make more suitable wheel pants for the WAW. I put the Zephyr projects on hold since I was just finishing creating a wheel pant mold for the Zephyr.
Dan brought the WAW to my house and I set to work creating a better wheel pant design!
This time I went for the really wide, gently curved design, and made them flush with the underside of the body. And now that I’m more confident I’m molding directly on the WAW body, so the curvatures will match better.
I started with the right side first. I placed the WAW up on a work table, and got things ready by removing the front wheel, applied flash tape to cover over decals and graphics (resin doesn’t stick to flash tape) , and masked off all the other parts of the velomobile so that overspray wouldn’t make a mess. I cut some coroplast in a rough outline and taped it over the wheel well.
The black arc indicates approximate outline, and it was drawn with dry-erase marker, which comes off easily with acetone.
The coroplast/corrugated plastic was taped onto the body rather than inset into the wheel well. I just need to compensate for this thickness later.
Once everything was ready (six coats of release wax followed by a mist of FibRelease) I laid up two layers of carbon fiber and left that to cure overnight.
Part of my process is to separate this piece from the body, break the bond with the WAW. Then I place the piece back on the WAW and start building the shape.
I cut some card stock shapes into templates. These wheel pants will be designed to allow for about 1.5″/40mm of clearance for the wheels. This should give me a turning radius similar to a Quest or other enclosed wheel velomobile.
Many times while out riding the WAW I would be taking turns at 20 mph, hanging my head over the side to see how much deflection or movement the front wheels required. It’s surprising how little wheel turn is needed to make most turns. And the WAW has independent left and right brakes on the front wheels, so a rider can use “brake steer” to assist in fast turns.
I transferred the template shape onto 1/4″ thick 6# isocyanurate foam. These were simply glued onto the carbon fiber shapes I just made. I then made a dam of flash tape to contain the expanding foam. The expanding foam is a runny resin initially and wants to find it’s way downhill. And I used some polyethylene sign as well. Here is the first application of foam, it’s just starting to expand fully.
It took three applications of expanding foam, the foam takes about 45 minutes to cure enough to work on it. When sanding into shape, the foam strips that I glued down are easily distinguished from the expanding foam filling around it.
Once satisfied with the sanded shape, I begin applying auto body filler (ABF). Lots and lots of batches mixed up. Initially it’s one large batch right after the other, but as things progress with lots of sanding between applications eventually the batches of ABF are very small to fill those final little areas.
Finalized with ABF and shaping, the buck is ready for gray molding gel coat. Two coats, then a full sanding to eliminate warbles and wavy-ness, then a third application of gel coat.
On this third coat I sand again, using the air orbital sander. First with 180 grit discs, then 320 grit discs. I finish with a wet sand by hand with 400 grit sandpaper.
At this point I mark the outline of the wheel pant onto the buck, remove it from the WAW and cut it into shape. Then it’s back onto the WAW again, nearly ready to make a mold!
I need a smooth transition from the buck to the WAW body, so a fillet of molding clay is applied.
Here’s a video I put together on these steps; the video is while building the left side so don’t let that confuse you!
The final preparation step is six coats of release wax over the buck and the exposed parts of the WAW, and a misting of FibRelease. Then it’s ready! Two coats of orange tooling gel coat sprayed on (the Milan was not there when I sprayed the orange gel coat 😉 )
To complete the mold, next was a layer of 4 ounce fiberglass cloth, and then 2 layers of 6K carbon fiber, with a finish layer of carbon fiber veil. In this photo I’ve just started to remove the mold.
Once separated from the WAW, the buck was still in the mold but was easily removed; I had used some two sided tape to hold the buck in place.
I could have made a mold off the buck earlier, back before cutting it into shape. But I do those extra steps of cutting and using the molding clay because I finish with a mold that has the wheel pant outline built in; makes it easier to cut into shape, and also easier during layup because I know precisely where to lay in the carbon fiber. Here you can see the outline of the wheel pant. The wavy looking band is the molding clay, and the upper outer area was against the WAW body.
I’ve designed these to be attached by a couple screws, plus possibly some tape. Since the WAW has the removable nose cone I’ll use some of those same attachment screws for securing the wheel pant. The lower two screws on the side will remain in place, under the wheel pant. The upper screw and another screw that is on the underside, just forward of the wheel well will be used.
As it stands now, both molds are finished (left side mold still needs final cutting and sanding/polishing). Next for me is to make a composite curing oven/box, so I can actually make the final product! That will have to wait for another post!