Thanks for your insight Kiwi :) Sent from my iPhone
> On Jul 20, 2022, at 8:20 PM, kiwi faulkner via KRnet <krnet@list.krnet.org> > wrote: > > > Colin writes: > > "Build them right and light and build in the correct empty C of G position > and there are no issues with the plane at all. Only issues you want to dream > up." > > Larry responds: > > "Builders and fliers on the net would be better served if you would use your > knowledge and expertise to educate builders and fliers on how to avoid the > problem rather then belittle them for their mistakes." > > "Where is your CG located, in respect to MAC, with you and a passenger and > how much does it change from full to empty fuel." > > > > Good points. > > > > I have no experience flying the KR2. I do have experience in airworthiness > certification test flying and have test flown a number of amateur built > aeroplanes also. > > > > Therefore I ask how the "correct empty C of G position" is readily > established in a modified aeroplane? > > > > Generally speaking, the aft CG limit is driven by static stability > requirements - such as stall/spin recovery - and the forward limit by pitch > authority considerations, such as the landing flare. > > > The Rand Robinson plans I presume specified a CG range for the MAUW KR2 > (900lb). Convention would dictate that this was likely established by an > initial analysis then refined by flight test measurements. But exactly what > iteration in the aeroplane's evolution did this occur at? What engine was > Rand using at the time - it would have been a VW derivative and not an > 0200/Corvair/Jabiru? > > > > Modification of the forward fuselage for an alternative powerplant > (propeller, spinner, cowling and so forth) are all destabilizing and without > analysis and testing you cannot know their effect on the static margin. And > of course, all KR-2 aircraft are flown within the specified 900lb MAUW! > > > > It is clear that the KR2 is resilient to builder modification in many > respects. In absence of current and relevant quantitative data, the only > guidance regarding CG range would be from that specified in the original > plans, and that is the best guess starting point. In absence of a further > analysis, it would be necessary for the builder to establish an empirical CG > range by flight test - which seems to be what is happening - sort of. > > > > It would be a good investment in time researching the matter of safely and > sensibly investigating the operating CG limits of any given version of the > aeroplane and then religiously adhering to them. > > > > Nga mihi > > > > Kiwi > > > > > > > > > > > > > > -- > KRnet mailing list > KRnet@list.krnet.org > https://list.krnet.org/mailman/listinfo/krnet
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