Originally Posted by Bob Kuykendall
And anyhow, my wing is much better than the Czech tapered wing. It is being developed by Steve Smith, who designed the RV-10 wing profile for Van.
I think all of us will agree that a tapered wing looks better. Those better looks come at a cost - there ain't no free lunch. There are benefits and drawbacks to a tapered design that replaces a non-tapered wing.
The Evo wing is designed to FAR 23 specs for a specific Vne, CG range, and weight. If I recall what the Czech engineer told me, it is good for close to 400MPH, and the gust penetration speed is 175KT at 2600LBS. That is a very robust envelope for a small aircraft. The wing was not designed specificlally for the F1 - it was designed for a very different design with side-by-side seating.
At the weights the F1 Evo flies, the design allows us to load it up like an A-10 - if the gear were stronger, and the empennage/aft fuselage/tailwheel assy were up to the job. Alas, they are not.
So, the robust design of the Evo wing adds a 'bit more' weight than required, compared to a wing set up for the design parameters of the F1. How much more weight? About 115lbs. Yes - that is one hundred fifteen pounds. Generally, the empty weight of the Evos run 1300lbs or so.
A composite wing - that meets the same design requirements - would be much lighter - likely close to the weight of a std RV wing assembly. Attaching the thing to the RV/F1 fuselage is the difficult part; a stub spar seems to be a good plan for the main spar.
Tapered wing Disclaimer: the CG range of a wing is described as two points on the airfoil, referencing the mean chord. If the wing is tapered, the mean chord is smaller, thus the CG range is smaller. This can change the gross weight load distribution slightly, or dramatically. What this means to us in the smaller plane we fly: the luggage capacity might have to be reduced (assuming it is in the aft fuselage), and maybe we can't take Bubba for a ride.
You might say (as Tom suggested): I'll move the engine forward! That would allow for more luggage, and Bubba, but if the design puts the pilot in the front seat, solo flight characteristics will suffer - think heavy elevator forces. The HR2 is known for better control harmony with someone in the back - the F1 has the same setup, but just a bit better due to the different horizontal tail.
We tweaked the elev system in the Evo (less deflection required), and retrofitted the same system to the Sport wing to reduce the heavy elev forces. The Evo has very light elev forces, but that goes hand in hand with the narrower CG range, and smaller aft load capacity.
Note the Extra has the pilot in the back for solo flight, putting the cargo/baggage/passenger on the CG. The load effect on the CG is much more favorable in this design.
So, a tapered wing design will probably be more suited for a side-by-side design as opposed to a tandem (front seat solo), as the CG range required is much smaller in the side by side design. The fwd luggage compartment in the RV8 might also help, but my guess is the airfoil will need to be shifted a bit on the spar to tweak the wing CG range to reflect what is normal to the standard wing. I can almost guarantee that the CG range will be smaller - but I could be wrong!
In any case, it will certainly look better, and it just might fly better. Likely it will also be faster. I can't wait to see it fly!