tomwebster said:
I have Rich's handles and just checked his web site.
I suggest you do also. I don't think a clearance hole for a
#10-32 screw is 1/4". My point is please check your facts.
A signature would help also.
Tom
Tsk tsk, you're being over defensive and splitting hairs. If you think I'm that far off the mark mathematically then why don't
you come up with a set of numbers. What indeed are the "facts". Are you going to point out to me that the real loss of cross section is only 13% when I said it was 14%.
What I'm saying is that the Vans standard roll bar will be designed to withstand specific static and dynamic forces and that those forces will be quite modest in line with the aviation principle that structural redundancy and weight savings must always involve a trade-off.
When a builder drills holes in the roll-over bar he reduces the cross section and the end result is that it will buckle at a reduced level of force. The holes will effectively reduce the safety factor by some margin...that is the fact...whether I like it or not (and whether
you like it or not).
I would further suggest that the roll-over bar in particular is
not the place for RV builders to be practicing intuitive engineering given that the RV series are relatively short coupled aircraft with a definite tendency to tip over in accidents.
I highly recommend in this instance that builders who are contemplating drilling holes in the roll-over bar beyond those called for in the drawings contact Vans for their professional opinion.
It is relevant that Vans sent out a Service Bulletin not that long back mandating a mod to stiffen up the roll bar on the tip-up canopy...presumably due to failures in the field. This would indicate that there was not much redundancy in the original design.