"Duncan of Devonport" wrote: > I know this question has been asked already, but I'm still uncertain about > this... Basically, I have three questions:
You're right, this has been answered several times, but I can see how searching the archives for it might be tedious. And since nobody else has bitten, I'll give it a shot. > I have a set of KR2-S plans, which as we know has an extra bay added to the > KR2 plans (ie lengthened by 14" aft of the cabin). Based on best practice > as evolved here on KRNet, by how much (in addition to this) should I > lengthen each bay aft of the cabin? And do I lengthen the bays forward of > the firewall? The politically correct reply would be to "consult an engineer", but since there's no documented problem with KR tails separating in flight (hurricanes don't count), I'd think you could get away with adding an inch and a half to each bay and not substantially change the geometry of the structure. One consideration that somebody pointed out is that the scarf joint for the plywood skin needs to fall on a wooden member, so keep that in mind, or simply add one more bay instead. Either way, you'll probably need more plywood, but in my eperience, you'll need more plywood than the plans call for anyway, so go ahead and buy another sheet while you're getting the rest. I wouldn't lengthen the fuselage in front of the spar more than two inches, unless you're going to put a light engine in it. > If I widen the cabin to 40", this will effectively reduce the area of the > wings, since the cockpit is now encroaching on the wing root by a few > inches on each side. Do I lengthen the spars/wings by the same amount to > compensate for this encroachment? I wouldn't bother, considering the slight width change that you're talking about. "Wing area" typically includes the area of the fuselage between the wings anyway. > Finally, question 3 > If I widen the cockpit to (say) 40" at the top, by how much should I widen > the bottom of the cockpit? By an equal amount? And a supplementary > question... Is there any fundamental or aesthetic reason why the cockpit > should be wider at the top than at the bottom? Could the sides not be > perpendicular? You can either widen the bottom the same amount as you widened the top, or you can make the sides perpendicular to the bottom. Your choice. You wouldn't be the first to make the sides vertical. Any detrimental aero tradeoffs would be minor, and it would be somewhat easier to build. There's more of this kind of stuff located at http://home.hiwaay.net/~langford/kopinion.html . Mark Langford, Huntsville, AL N56ML at hiwaay.net see KR2S project N56ML at http://home.hiwaay.net/~langford
