Hi Colin and netters. A Very good argument. I think you are right that it all boils down to weight and drag. The faster airplane will be the one with the lower weight and drag penality. The faster of two identical KRs (except one with fixed gear and one with retracts) will depend on gear system weight and upon gear system drag. Now compare the simple and light KR retract system weight, to the KR fixed gear system weights. They are nearly the same weight, so then it boils down to drag. Now you have to argue that a properly faired fixed gear system has less drag than a properly faired KR retract. There is one other factor I just thought of. The drag on the fixed gear tends to tip the nose down more because of its lower center. If the angle of attack of the wing is already at optimum; the pilot will counter by trim, which will increase drag again. So now it's gear weight & drag penality plus angle of attack efficiency. Im sure we could analyize this to death, but without accurate numbers we are just wasting band width and hell; it's a lot more fun to just fly, or race. By the way; I'll bet mine is faster. He. He. ----- Original Message ----- From: "Colin Rainey" <brokerpi...@bellsouth.net> To: "KRnet" <kr...@mylist.net> Sent: Thursday, December 14, 2006 9:17 PM Subject: KR> Retracts
> I feel a contest coming on.. But how to do it... These things must be done > > delicately.. I mean scientifically. > > Rich and netters, > > I have already illustrated a factual circumstance of a certified plane > (which some believe is the benchmark we are all measured by), that were > identical except for the systems and equipment necessary for retractable > gear: The Piper Archer PA28, constant speed prop with 201 hp Lycoming > engine, and The Piper Arrow constant speed prop with 201 Lycoming engine, > and retracts. More fuel, more empty weight, and better speed due to lower > weight for same load, and longer range. No one can argue that lighter climbs > better, goes farther, and cruises faster, given the same fuse, engine, > etc... The same thing applies to the guys that have an RV7 or 8 and install > a Lycoming IO-540. They cannot go faster due to design limits, but they > climb better, and cruise at a lower rpm. They have more hp, but carry the > same or more weight, so cruise is not higher, but the engine turns less > rpms. A KR2 or S model given retracts and then fixed gear with proper > attention, and the same engine will cruise faster at the same power output > rpm, and climb faster, due to lower overall weight. > > Why do you think that your plane performed soooo much better with the > instructor out during solo? Harder to land yes, because he was not there so > you were lighter and floated more! IF the same size and weight wheels are > used, and brakes, installing fixed gear will ALWAYS result in better climb, > and if FAIRED in properly for drag reduction (same idea of the retracts), > will yield a higher cruise. This is due to the lower weight with the same > drag component to the available thrust. > > Look at the typical lower class air racer, running under say 150 hp, and 1 > or 2 seat airplane; ALWAYS fixed gear are the fastest. They know what makes > speed. Clean lines and light weight. NO RETRACT system is as light as a > fixed gear. Same thing applies to the tail wheel vs. the tri-gear; ALL the > tailwheel designs are 5 to 20 mph faster depending on how clean they are > over similar trig-ear models. > > Now if you retract guys took the time to design a FULLY retracted model with > DOORS, similar to the Lancair IV or Cirrus, then you might be able to come > close to convincing me with under 200 mph aircraft like ours. Where > retracts really come into their own is over 250 knots. Then you are talking > BIG benefits, but that is a whole 'nother story... > > Colin Rainey > brokerpi...@bellsouth.net > > >
