Difference in Gross Weight B/W RV-6 and RV-6A?

[campi]

I noticed for the first time today that Vans lists a difference gross weight between the RV6 and the RV6A in its performance section. Difference is 1600 or 1650.

http://vansaircraft.com/public/rv6perf.htm

Can anyone tell me why? It would seem to be the same structure.

Is there a real difference in the gross weight between the two, or is this just the weights at which performance was measured for the two models?

Thanks,

Fernando

 

[pierre smith]

Fernando, I'd have to guess that the -6A might weigh 50 lbs. more because of more structure to the engine mount to hold the nosegear, wheel and tire combination.

The final gross weight number is, after all, posted by you.

Best,

 

[Snowflake]

It means that Van designed the nose wheel version second, and needed the extra gross weight to carry the gross wheel (ah, I mean, nose wheel) and associated structure. He was comfortable cutting into the safety margin to allow that extra 50lb on the nose wheel model.

Other options? It *could* mean that the extra structure on the engine mount makes the engine mount strong enough to carry the extra 50 lb. It could also mean that our gross weight is limited not by aerodynamic loads, but by design landing loads... And the tricycle gear being made from larger tubing would be stronger in that regard.

 

[rvbuilder2002]

It could also mean that our gross weight is limited not by aerodynamic loads, but by design landing loads... And the tricycle gear being made from larger tubing would be stronger in that regard.

The most correct answer......
The difference in landing gear attachment and load paths is the primary reason.

All to often, people only equate gross weight to flight and aerodynamic loads. Loads induced by landing (rather high on some occasions in fact) have to be considered also.

 

[Bevan]

Landing loads on a A model are transmitted directly to the spar and center structure very close to the CG. The tail dragger has it's landing load applied to the engine mount (with the exception of the RV8). This may or may not have anything to do with the difference in published gross weights. It's interesting to note than Van's recommended gross weights are the same for all the other trigear-tail gear pairs.

Bevan

 

[campi]

Interesting

Thanks for the explanation rvbuilder. As Bevan mentioned, however, it is interesting that the RV-7 and 7A have the same gross weight. Maybe there is a wider "margin" on the 7. But, good to know that there is a real difference between the RV6 and the RV6A in terms of gross weight.

Thanks everyone.

Fernando

 

[dbris]

I noticed for the first time today that Vans lists a difference gross weight between the RV6 and the RV6A in its performance section. Difference is 1600 or 1650.

http://vansaircraft.com/public/rv6perf.htm

Can anyone tell me why? It would seem to be the same structure.

Is there a real difference in the gross weight between the two, or is this just the weights at which performance was measured for the two models?

Thanks,

Fernando

I think the difference is CG related. If you do the CG calculation on the 6 as designed (O-320 and wood prop) you'll find that the empty CG is pretty far aft. I believe that they limited the baggage to 60# instead of the 100 that the floor was rated for because 100# would put the CG too far aft with full fuel and passengers. So by putting the 20 pound nosewheel up front, the empty CG is moved far enough forward to allow more weight in the cabin.
I have a CS prop and O-360 which moves the empty CG far enough forward that it cannot be loaded out of the envelope if the baggage is limited to 100#.