Cub for the Linemen

In your Cub Comparison story (March 2011), the author mentioned that he had trouble shoehorning his 6-foot-3 frame into planes, and that brought up a complaint I have about listed specifications and review articles. Cabin width is frequently mentioned, but headroom and legroom? Never. Car manufacturers list sitting height (from the top of the seat to the bottom of the roof) and legroom (from the seat back to the firewall)-so why can’t aircraft reviewers and manufacturers do the same?

At 6-foot-4 and 275 pounds, I can’t drive any car that has a moon roof, and I sympathize with the problem of finding an airplane that fits comfortably. Thus I wish you had specified the Carbon Cub cabin size details, which with its 1865-pound gross weight and 180-horsepower engine could haul my weight. Planes seem to be designed to fit the FAA-standard 5-foot-9, 170-poundperson. Unfortunately, that standard was created from data obtained during WW-II, when the government was first able to measure population data from all of the military inductees. Americans are no longer that small. The 75th percentile man is now over 200 pounds, and in certain regions (Minnesota/Holland) the average man is 6-foot-1. I wish that manufacturers would take this new reality into consideration.

Barry S. Gloger

To Be a Man of Means

I greatly appreciated the recent articles in KITPLANES on the current line of aircraft from Zenair and on the Thatcher CX4, mainly because were I a man of means, I’d like to have one of each. I noted with interest that you avoided mentioning the spate of well-publicized hardware failures suffered by the CH 601, prompting me to ask a couple of questions. Has this issue been resolved to everyone’s satisfaction? I ask because there are a couple of very nice 601s on my field, but I’ve not seen either one fly in ages. While I’m impressed with the CH 750 because it fills all of my needs except reasonable cross-country speeds, I know very little about the CH 650. Is it simply a spiffed-up version of the 601, or is it a reengineered design intended to get the company past the earlier unpleasantness? I’m finally in a position to build something a little more exciting than the Piper I currently fly, but I’m looking for the good kind of excitement. I am much too old for the other kind.

Rob Coffman

While there’s no way to be 100% sure without some passage of time, we’re reasonably confident that the airframe troubles haunting the 601 series are behind it as long as the updates have been made-and made correctly. The 650 is based on the 601, but all new kits incorporate the structural modifications outlined by the company for the 601.-Ed.

Rotary Spin

As I was reading Paul Lamar’s dissertation on the Wankel rotary, I wasn’t thinking “Hmmm” so much as “Say what?” I am a 30 year Commercial A&P and bona fide gearhead. There is no doubting that he loves his rotaries, but I believe he has blinders on concerning [domestic auto] engine reliability. I will concede the advantages of the rotary’s design and its ability to generate large power from a small package. I will also concede that it doesn’t waste motion. My exception is that Lamar’s bias would have you believe that the Wankel design is virtually failure proof, and piston engines are blowing their rods and cranks everywhere. I think he needs to spend some more time at the racetrack, especially where the so-called “import tuners” are racing. He would see that this engine will blow just as easily as any other. More importantly, he needs to go to YouTube and watch Ford’s EcoBoost torture test.

To date, the Wankel design hasn’t duplicated this test. I don’t believe it ever will either due to reliability issues. Lamar as much as admitted this in his article by saying, “If the wear of the seals and sliding surfaces can be reduced to low levels…” Also toward the end of the article he speaks of using exotic materials for the rotors. That would have already happened if it was economically feasible. He is also incorrect in comparing rotary engine balance to turbine. Apparently he never sat toward the rear of an MD-80, hearing and feeling the harmonic vibration of the JT8D-217. All commercial jet aircraft are equipped with vibration monitors. I’ve worked in a jet overhaul shop where we balanced the compressor sections and turbines. There is no such thing as “complete and precise balance” in turbines, rotors or otherwise. While I admire Lamar’s loyalty and steadfastness when it comes to rotaries, it’s like Shania says in her song: “That Don’t Impress Me Much.” Kudos, though, to KITPLANES for allowing Lamar to express his opinion, right or wrong as it may be.

Mark Hull

Corrected Correction

We received a note from author Owen C. Baker regarding his magneto-timing story that appeared in the January 2011 issue. We admitted to a correction in the March Letters column that wasn’t quite, ah, correct. Turns out, the tester Baker used and referred to in the text does indeed act as described. However, the unit we used for photography performs exactly the opposite. To be clear, then: The Action Air Parts timing light (with LEDs) will extinguish its lights when the points are open. The Eastern-made timer used in the photos will turn ON the lights when the points are open. Lesson? Know your tools!


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