Before you do any cutting, finish the model, fly it five or six times, be sure to seal the flap and elevators. Then if you find it is not to your liking, do as Brett suggests. I have done this on other models but never felt the need on the Profile Cardinal. You may like the way it flies or not. Only you can tell. Remove chord width by only 1/16th at a time. Over a 12 inch flap that is almost one sq inch of area gone. 12/16=3/4 sq inches. LITTLE twitches at a time. Remember, one twitch here or there may affect trim else where. 
I stick to the original recommendation. This isn't speculation, we already did it, resulting in the 2006 Senior National Championship for our flying buddy Paul Ferrell.
An issue with the "try it and see" approach, just like it was with our young friend Paul, if you don't have a lot of experience flying a very wide range of competitive stunt planes, you don't necessarily know what you need or what problems a particular airplane is causing you. Much to the contrary, if you ask the pilot about how the airplane flies, they almost always say something like "the airplane flies great, I just can't fly good enough to do it justice". After flying hundreds of them, I haven't found a single case where that was true. As far as I can recall, every single time I flew the same plane, it had pretty serious problems that the pilot was completely unaware of, and the airplane was difficult to fly.
Ted did this with Paul's kit Cardinal, and I have flown a few kit and ARC Cardinals, and they all had the same problem - essentially impossible to control the corner radius, and very high control loads around neutral. If Ted and I can't control it with enough finesse to be competitive, it's a good bet most other people can't either. Removing flap area (at the field, as I recall, but getting a bit hazy) fixed this immediately and about a week and a half later, Senior champ (and not uncontested, either).
I mention 3/8" because that is very conservative, and probably not enough. I think the original was *3/4"* with no intermediate experiments and the flap at the tip was around an inch wide when we finished. Of course, if you think you have gone too far, you can always glue/tape more back on to it (even at the field). How much you want or need is not really a matter of personal preference, I think it as more to do with how well your engine/prop works - more flap for 4-2 break engines (which is when the "giant flap" phenomenon began) and less flap for good engines. The reason is that the older engines cannot maintain the speed in the corner nearly as well. Unfortunately, the extreme drag of the stock system ALSO causes an issue in that case.
Brett
Topic: Profile Cardinal (Read 2809 times)
