A "specs" question, rv4 verses rv6

[flybynight55]

I don't know if I'm not thinking right or what, but Vans website gives the specs as follows:

RV4 wing span>> 23ft--------------------cockpit width>>> 24 inches
RV6 wing span>> 23ft--------------------cockpit width>>> 43inches
both have 110sq ft area.

I don't get it, is it the chord thats different??? Yet they say the rv4 wing worked so well that they didn't change it on the RV6. Does that mean that an RV6 wing will fit on an RV4??? Is the RV 6 and 4 empannages the same??

I'm just trying to learn as much as I can about these plane since I want to choose one of them to build. Sorry for these questions if they are obvious to others and not to myself. Thanks, Tom in Ga.

[gmcjetpilot]

Good catch, I know that the wings are very much a like from a structures standpoint. It was not till the RV-8 and RV-7 did van change the structural design of RV wing.

The true wing area on the RV-6 is smaller, wing area wise. That is why the RV-6 is a little more sporty (slight higher stall speed). Since the cord and span are the same and the fuselage is wider, it will take some span. You would thing the wing areas would be different.

However, I think Van's wing area is tip-to-tip length (23 ft) times the cord, so the fuselage width is included in the wing area.

Cord is 110 sq-ft/23'=4.78' (57.4")

So the true wing area is
RV-4: [23' - (24/12)] X 4.78 = 100.4 sq-ft

RV-6: [23' - (43/12)] X 4.78 = 92.8 sq-ft

The RV-4 has about 8% more wing effective area.


Why van includes the fuselage in wing area I don't know. I could be wrong but that is what it looks like. It looks like he carries this practice into his other models.

From Van's specs the RV-6 has stall speeds 1 mph higher than the RV-4 for both solo and gross weight. The listed gross for the RV-6 is 100 lbs more. Empty weight (and solo wt) is what ever it turns out to be, but Van estimates empty wt RV- 4 around 910 lbs and the RV-6 around 965lbs. Fact is most RV's are much fatter than this. For the RV-6 and especially Van assumed people would use O-320's and light props. His newer models have more realistic empty weights, but they are still is often exceeded but builders, some times by large margins. Either way RV's stall at 15% slower than a C-152. So stall speed plus or minus 1 mph is not an issue.

The tails are different. The RV-4 has elevator counter weights that go to the leading edge. The RV-6 has counter weights that do not extend as far fwd of the hinge and nests behind a tip fairing. As far as the Rudder and Vertical Stab I don't know. Call Van. From a structures and aerodynamic standpoint they are identical. However the RV-6 is known as a fast spinner. With the wider fuselage or other reasons. The RV-7 got a bigger Rudder after spin test. So the side-by-side configuration affects spin characteristics.

The RV-7 also got a longer wing span (25'), where the RV-8 is 24' span. The difference in the new wing design (RV-7/8), "plugs" into the fuselage and there is a fixed length of wing stub that interfaces with the fuselage. The spar does not carry thru to the other spar and splice at centerline (BL 0.0). The RV-4/6 design butt's at the center of the fuselage and the wing spar is spliced at the centerline, making a straight thru spar. G

[Alex]

It's standard practice in aircraft design terminology to include the center section area as part of the wing area. In fact, the wing area winds up being just a scale factor that is used to compare aircraft of different sizes, so the exact value is not so important. On tapered wings, for example, some people treat the fuselage area by adding an area equivalent to the root cord extended across the center section. Others extend the leading and trailing edges to the centerline, which would give slightly more area. On aircraft with fowler flaps, where the wing chord increases when the flaps are deployed, the clean config wing area is generally used even though the physical planform area of the wing has increased.