Rich, The Hershey bar wing on the Cherokee 140 works just fine. Just as the article that Mark Langford came up with does state. However, one has to be careful how parts are cobbled together. The whole aircraft is a collection of trade-offs and compromises. Our KR-2 and KR-2S aircraft are no exception (and no two are identical). That said, I was guesstamating without a calculator how much wing area would increase using the straight wing versus the tapered wing. I used my KR-2 with the Diehl wing skins and larger span (23' 6" versus the stock 21' 3"). My wings have a 48" chord at the WAFs but taper even more than the stock design to still get the 80 sq ft called out in the stock specs. So, that comes out to be 94 sq ft for the Hershey bar wing. Higher math on the calculator yields 17.5 percent increase in area - not to bad for a guestamate. All other parameters remaining constant, change in slow speed lift is proportional to wing area change, as is induced and parasitic drag. The short coupled KR-2 could easily get the rudder blanked by bigger paddles stuck out on the new Hershey bar wing. Hence, poor spin recovery is indicated. Bottom line: The Hershey bar a.k.a. straight wing works fine on other aircraft designs, but I would not recommend it for the KR series without some serious professional design evaluation. That stuff is way above my pay grade.
Sid Wood Tri-gear KR-2 N6242 Mechanicsville, MD, USA smw...@md.metrocast.net >Sid, >What formulas or table did you use for calculating the change in flight >characteristics for a rectangular planform wing? The 20% figures you state >seem a little >extreme. Also, I think the change would add only about 7 Sq >ft to the wing area. >Rich Hartwig >Waunakee WI >about 20 percent to the wing area all out at the tips. >The initial rate of climb would go up about 20 percent; the top speed would >decrease about 20 percent; the roll rate would slow by about 20 percent. >The hersey bar KR-2 would tend to get into an unrecoverable flat spin >during >a departure stall due to blanking the rudder. In short you would have >created a two-place Cherokee 140 with a high time engine. >Sid Wood
