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Permalink Reply by Lawrence Bird on May 18, 2017 at 11:25am

Your May 7^th 10:56 posting was enlightening -- if we ever needed evidence that there ain’t no free lunch, I think we have it. What I found particularly interesting was your findings on the belly-pod… I’ve long theorized that the fuselage (CH701/750//801)itself may be one of the larger drag-producers…   Notwithstanding, count me among those who think Chris got almost 100% of his early design goals – simply; a sturdy, simple plane that could be both  safely built, and flown, in the boondocks, by pilots with noticeably less that Walter Mitty’s skills.

 

The discussions over the past quarter century seem to reflect the fertile minds of numerous skilled hobbyists as they attempt to take the fundamental design and expand its flight envelop in one direct or another.  I started on a long-wing CH701 (701 with 750 wing) that is now rolled up (on the top of the shop) awaiting me to finish the current project.  I was content with an 80-90mph cruise, noting that many of the enhanced STOL Cubs do little better, and thought to optimize the lower end through wing area and weight control (notwithstanding the pilot’s abject corpulence…).   In the meantime I’ve looked at the Peg, the STOLKing, Cuby (again) and the KFox knock-off (Raven) among others – got the plans of all, just not the t-shirt.  The Peg is probably the closest of what you can do with “sorta” Zenith aerodynamics… the tail feathers and flapperons being the closest aspects, the fuselage and wing/airfoil/retracting-slats being the largest divergences.   One thing that came through to me was the time difference in a scratch built CH701/750 (seems to be between 1500-2500 hours) as versus a scratch built Peg where 3500-plus hours isn’t unheard of.   I think there is enough experience out there to handily optimize either the top or the bottom of the fight envelop, but attempts to have it all almost inevitably seem to increase complexity and build-time in one aspect or another. 

Seems to me, you may have several folks interested on what your mods produce... 

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Permalink Reply by Samuel McNair on May 21, 2017 at 9:54am

Keep in mind that the belly pod probably only decreases drag on the CH801. The CH 750/701 have the gear cross member tucked up in that slot in the belly, not out in the wind 5" below the belly like the CH801. It would  be interesting to see how smooth the belly surface is when the weight is off the gear in a 750/701. closing any gaps and ensuring a flush surface might be worth a few free knots.

I have to admit, I chickened out and bought both of my CH801s as finished by brand new airframes still in phase 1. I have been flying now for 40 years and most of that was in Cessna singles and Piper twins.  When I sold my last C182 and settled on the CH801, I had thought to build.  But then knowing my work schedule realized that my flying years would be virtually over before I got it built. I wanted to fly more than build and could not do both. But that does not stop me from experimenting and I like to figure out how to get the very best out of an existing design.  And like most people I have to do it on a tight budget.

I will tell you a story: 1st new car ever (a cheap econo-box) topped @98 mph and got 24 mpg at 55 when factory new. After I got done tinkering it topped at 110, I once cruised it the whole way across Nevada averaging 104 at 24 mpg and it got 37 mpg at 75, and could out-handle the BMW 1600. No single change cost me over $100. It was a matter of tapping its hidden potential.

My first 801 got 82-85 knots at ~9 gph and landed in about 250 to 275 feet. After mods with the extra weight of the pod, it cruised 101 Knots at 7.5-7.7 gph and landed in 275 to 300 feet (also at zero wind). And I wasn't done tinkering yet. There certainly are limits that you cant go beyond without fundamentally changing the design. But I don't like wasting that hidden potential that exists with any design.

Stop correcting "i"The most expensive single item was the $1800 PMag that allowed me to run MoGas and run LOP with  carbureted engine.  Picture below of the IFR panel I built and am installing in my CH801 at its first bench test.

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