I agree with the 20 degree rule for motorcycle streamliners as I believe flat bottoms push the chances of serious injury beyond what’s acceptable. Just some thoughts, take them for what their worth, feedback is welcome.
Nothing against Jack’s cars/bikes as I still think they have a wicked fast look that stands alone and, as many have pointed out, their records speaks for themselves. As for taking a stab at why they’re fast I think their shape is good but their size is better. Blue commented (I’m paraphrasing what I think he said which might be dangerous!) that shape is far more important than size. Jack’s cars look pretty “slick” but I bet everything on the salt could be improved and that a very small body with an aero issue still has less drag than a large body with a similar issue? Until we get it near perfect, size still matters.
I don’t think the aero is a serious safety issue for flat bottom bikes. Blue mentions kiting, I might be wrong on this but... Assume one of Jack’s bikes ends up nose high at a high rate of speed. It would see the rise in pressure that would normally cause kiting but wouldn’t the rear, with its much greater surface area, see more lift, rise faster than the front and end up leveling its attitude?
The problem I have with flat bottom motorcycle streamliners are the corners that come with them (bottom edge, both sides, front to back). I don’t think they’re more likely to crash but I think they’re much more likely to be VERY dangerous when they do. The videos I’ve seen of round body motorcycle & bicycle streamliner crashes usually always shows them sliding around on large radius surfaces with a comparatively low amount of drama. If a flat bottom bike crashes I think there is far too great of a chance it will catch an edge and the crash will become very violent very quickly. If a round body looses air in the rear it will likely lose control, fall over and slide. If the rear of a flat bottom loses air it quickly turns into a very fast, very oddly shaped sled. Any bets if it would continue in a straight, stable direction? There seems to be far to much of a chance it’s going to catch an edge and, again, get very violent very quickly.
Jack mentions one rollover in 5050 and it seems to support my concern. When it quit rolling forward normally and came around, it rolled. Jack can tell us. Did it just roll on its side and slide or did it hook an edge and barrel roll? How fast were you going when it happened and what would it have been like if the 250 had seized when it made its 200+ pass?
Crashing is a possibility that everyone here must consider. Reducing the resultant personal damage is the goal behind nearly every safety rule in book. Flat bottom motorcycle streamliners were banned not as part of trying to stifle innovation but an effort to keep the innovators alive! Rollie Free (sp?) went fast too but how long do you think it took to ban his speed suit?
