Trivia I love it
glenn654 said:
If I remember correctly, the curved roll-bar was used on early -4s but because of poor strength Van changed to the triangular design. This may or may not be a issue for you but worth considering. P.S. I think the curved bar looks much better too. Glenn Wilkinson, N654RV @ OKZ
Glenn I love dusty old RV trivia and can't refute your comments, but I found some circumstantial evidence the curved roll bar modification we are talking about is probably just as good (may be better) than the stock shape.
click and watch me grow
Doing a quick check, the first prototype RV-4, N14RV, shown on the cover of the EAA sport mag, May 1980, had NO ROLL BAR! Actually it looks like it had a big curved bow that followed the contour of the canopy. The tube diameter looks fairly small, more just a support for the canopy than roll over protection. The prototype had an unusual canopy. The back half slid back; the front half flipped over on a hinge as today's canopy does, minus the back half.
The original roll bar would have been too weak for roll over.
I think the changes to the roll bar was just from Van's simplifying the whole canopy design, to the one piece flip over.
I don't think Van ever made a curved roll bar as we are talking about. I also think the roll bar design was done for ease of production not strength. You can see where two tubes with a plate gusset is easier to make and control tolerances. What I do know about Van's aircraft circa 1980's, it was a small time deal. I suspect tube benders where not handy or cost effective. Van and Art Chard where like a two man show, unlike the small industry "Van's Aircraft" has become (for the better).
The final word on the topic may only be in Van's brain.
My guess is the curved roll bar Mod has the same function and strength as the original.
Using common my eye for structure I can't see a big difference. I guess there my be higher side load stability with the "teepee" roll bar. Hard to say. I think the support structure might fail laterally before the bar fails. The steel bar is probably stronger than the attachment in general. As some one said, if you load it that much, you're in deep trouble.
That the RV-4 has done well in passenger/pilot flip accidents? I had a RV-4 but now with a RV-7 slider I think about flip over. I know of one case where a
RV-6A flipped, which contributed to a fatality. On the other hand I know of a case where a pilot in a high wing Cessna flipped over during a low speed landing ground loop accident. The pilot apparently did not have his seat belt on tight enough (or on at all) and was killed. So keep those belts tight.
Good Luck...
