In order to be useful, a design must fulfill a purpose, or "market" niche. The purpose need not be monetary -- the market in question may be that of making folks happy, spreading Peace and Love, or winning a competition just for the sheer challenge of the thing. In my case, my purpose is this:
There is also another claim, less easily made:
With that in mind, the question is: should we just use plain rivets, or should we mess with bonding?
The aircraft industry has been using rivet bonded construction for many years. Thus it is instructive to follow their trajectory. The original F-18 A-D had a multi-part metal fin. The newer E-F models have a single piece, bladder molded, heat cured composite fin. Sound familiar? Bikes like the M5 Carbon High Racer and the Velokraft bikes all use this method, as do many upright carbon frames. Clearly, if you have the equipment, this is The Future. In addition, absent bladder molding, people like Garrie Hill, Jim Scozzafava, Tom Traylor and a whole host of others have shown that, if one is willing to do layups, carbon construction rules the roads. Hence, once again, the niche is to find something easier than carbon, but lighter than space frames.
There seem to be conflicting notions out there about how much one needs to prepare a metal surface for bonding. However, among people who rely on it for a living (or whose companies will fail dramatically if their structures come apart in service), the consensus seems to be that it's not easy. Check these out for starters:
- Hysol® Surface Preparation Guide, Loctite Aerospace [PDF]
- Adhesive Bonding Surface Prep Qualification Considerations, Jim Mazza, Materials and Testing Directorate, Air Force Research Laboratory [PDF]
- The Windcheetah manufacturing process
Thus my current direction is to just rivet. Every Schmoe can build one and it will very likely stay together. It's easy to see a crappy rivet and, conversely, if a rivet looks pretty, it's probably adequately driven.