A while back, Peter Borentstadt pointed out to me that the DFXL has a pair of structural ribs that are missing from the DF. The ribs are approximately eight inch tall internal supports that live on the inside wall of the body at the top of the strut towers. I’ve owned a DFXL and now own a DF and never noticed the “missing” ribs. I’m guessing that they were added to the DFXL during its development to reduce any new flexing introduced by the extra height added to the body in those areas.

We’re always looking for ways to improve the DF’s performance for Peter’s Battle Mountain runs. Most of the improvements that we add make no difference to my performance at the speeds that I ride. However, little tweaks can add up for elite riders like Peter, who can power a velomobile into the high 50mph range at Battle Mountain.

I made a pair of ribs for my DF to be sure that they fit and could be permanently bonded in place. Fortunately, my buddy, David, was kind enough to let me make molds of the ribs installed in his DFXL. I didn’t want to make a mess of his cockpit while making resin-based molds so I used a technique that promised to be quick, easy and non-messy. I applied a 2 part silicone putty blob on each rib.The putty cured into permanent but flexible, rubbery impressions of the ribs in about 20 minutes. They were easily pulled off of the DFXL without leaving any mess behind. These impressions couldn’t be used as the final molds due to their flexibility. So I used them to make prototypes which I could tweak and body work into the final shapes. I then made the final molds from these prototypes.

I used a 2-part structural epoxy adhesive to bond the ribs into my DF.

I took a quick test ride after the ribs were installed and the adhesive had cured. Of course I couldn’t detect any difference in the handling or power delivery, but at least they didn’t cause any new problems. So I shipped a pair to Peter to install in his DF. Peter had this to say:

Not sure if this mod can be felt, but at the least, if someone sits in that spot it won’t cave in.  Structurally, the more the “U” of the bridge is closed the better.  I think the cornering should  be better at the extreme.  Maybe it will feel more solid overall on rough surfaces.

Just having a quick look, I think they would be helpful in case of a rollover.  Some extra protection.