Originally Posted by ChiefPilot
Did Van's provide this to you directly or did it come from VAF / Internet? I'm curious because I was under the impression that the difference was due to the main gear weldments adding additional strength to the wing spar. Maybe it's both?
When I was building the RV"X", (the combination of a 6 Fuselage and RV4 Wing/Tail) the GW subject arose several times. The X's fuselage was originally a 6A that I simply omitted the weldments and matched the RV4 wing to the 6 center section. The RV4 tail simply bolted right on, albeit 15% smaller surface area. The wings(RV4,6) BTW are identical. Their only difference is one rib bay of metal next to the fuselage. The spar box, minus the gear weldments is pure RV6 with an RV4 wing installed minus the one rib bay. This allows the RV4 to have longer ailerons, shortened flaps to match wingspan. Thus the X has a bit better roll rate with smaller flaps.
So, 6A gross weight, 6, 4? Van's eluded that the additional structure merits higher GW. However, "The X" is a one of a kind and Van's of course approaches the subject of modifying a design much akin to Area 51."Don't ask, don't tell". Being a former Rocket guy, I understood completely the term persona non grata!
I asked my AE friend "KK" what he thought about RV GW calculations once. His insightful words of wisdom concluded in my mind that GW calculations on EXP designs are well padded (by design). He added, "don't forget what is printed in 2" letters in plain view".
I used 1600# for a nice round number for the paperwork and it will carry every bit of it, and more.