CA soaking with Thin or Med CA makes rounding Heavy Cardstock fins sand just like Styrene Plastic. using 220 to 360 grit make sanding them very smooth.
BARBAR I thought your worked for NASA. It's been common knowledge that the act of simply rounding the leading and trailing edges of any fin set will increase the achived altitude of that particular model by up to 10% over Square edged fins. Wind tunnel tests and tracked altitude Test provided evidence that this practice is sound.
QUOTE]
LOL, I said I build rockets for NASA, not that I worked for NASA. That would imply they actually PAID me for the rockets.
No doubt rounding can increase performance, as you said UP TO 10%. (As other poster mentioned, with such thin card stock to begin with, YMMV.) Even more perhaps if you aggressively taper the trail edges. For a SPORT rocket, question is whether the effort and time is worth the performance increase, or perhaps better put, whether it give you more FUN when you actually launch your noncompetition sport rocket.
Beauty is in the eye of the beholder. I am not convinced personally that rounded fins necessarily look better than squared fins on ALL rockets. Example is the Flutter Bye, definitely not a competition bird that personally I think looks better with somewhat "blocky" squared fins.
Your are correct of course. Well rounded fins certainly are a mark of good craftsmanship, no question. For those more experienced to imply that beginning builders "must", or "should" do certain things...... that I am less certain about. The "musts" for the beginner should regard building a rocket that is safe and recoverable. The additional craftsmanship touches (rounded or tapered fins, filled nose cones and spirals, smooth fillets, Future finish coatings, etc.) are great suggestions but particularly with sport rockets (translated: for FUN rockets) should be left to the discretion of the beginning builder.
Perhaps I've seen to many posts of beginners spending hours tapering fins on sport rockets (yes, I know, this post is ROUNDING, not tapering), to me a waste of time and actually makes the rockets more prone to fin damage on landing. If the builder is however specifically LOOKING to increase performance, it is a whole different story, but in most rockets that aren't designed to be competition birds to begin with (Viking--- 3, 4, ? 5 fins)..... well, you get my drift.