Thumbs up.👍 On Mon, Jul 25, 2022 at 3:56 PM Dr. Feng Hsu via KRnet <krnet@list.krnet.org> wrote:
> Yes Mr. Colin, thank you for sharing your experience from your KR2 > adventure around the world, and your stores are nothing short of fantastic, > amazing and miraculous! > > I truly enjoyed my reading of your interesting and exciting long stories, > as you are a hack of an excellent writer as well! While enjoying your > stories, especially about your unexpected and risky encounters in Russia, I > kept saying to myself, it's a miracle this guy are still with us today and > I can't believe he had managed to survive all that dangerous encounters and > allowed us to read what really had happened during your incredible journey > around the planet! > > You surely took lots of risk in your global adventure, and I am amazed to > see you are still alive today because you have violated nearly every > principle about safety and risk management in your exploration of the world > on a tiny little homebuilt KR2 flying boat which is basically made of > nothing expensive but a bunch of wood sticks & foam panels...! > > I can see you are such a lucky guy who could have dead of spark induced > fuel explosion when you tried to messing with the wire connectors that > surrounded by a bunch of your moving fuel bladders, and you could have dead > of an engine detonation in middle air if the ave gas you bought from a > Russian pilot was fake or counterfeited. And most likely, you could have > dead of being shooting down from the air by both of the Russian & Chinese > border defense near the Russia-China border for violation of their security > protocols.....!! > > I for one, solute you for what you have done and achieved single handedly > for the glorious reputation of the KR2 community around the globe! > Honestly, I remember one of the key reasons behind my decision to get into > the KR2 arena a couple of years ago, instead of buying a Pulsar was due to > my watching of a news on YouTube about your adventure with your homebuilt > KR2.... > > Thanks again for sharing! > > Dr. Hsu > > On Sat, Jul 23, 2022, 12:24 AM colin hales via KRnet <krnet@list.krnet.org> > wrote: > >> In the spirit of safety indeed… >> >> >> I apologise for not responding sooner, been away on business. And sorry >> for the length of this message, but I did try to cover all questions asked >> in-depth and thoroughly. >> >> >> >> The two KR2 aircraft I built were a standard KR2 design. Originally they >> had VW1834 engines as per the original design, but then Jabiru engines were >> acquired due to their increased power and 60 pound weight saving. Since >> this engine was so much lighter than the VW 1834, this would require >> extensive calculations to see how far we needed to extend the engine frame. >> We needed to calculate the centre of mass of the VW engine and compare it >> with the Jabiru engine. Eventually, the conclusion was that the centre of >> mass of the jabiru needed to be 10 inches further forward than the VW to >> establish the most forward C of G position desirable. My empty C of G >> position is 19.3 inches aft of the firewall datum or 7.3 inches aft of the >> leading edge. Approximately 15% of the cord and 1 inch in front of the fwd >> C of G limit... Each aircraft in the UK has to have its own individual >> weight and balance calculation, so that covers any variations in build >> design. >> >> >> >> >> >> While changing to the Jabiru engine, there was another young builder Phil >> Geohegan working on his Jabiru powered KR2. For his university studies in >> Aerodynamics, his thesis involved the study of modification of the KR2 >> design by placing an additional 12 inch bay forward of the wings for his >> Jabiru powered aircraft. His aircraft weighed 485 lb if I remember right? >> Wind tunnel testing was carried out with the longer nose modification and >> the findings were that it made little to no effect on stability between the >> standard aircraft. I only wish I could find the pictures of his 1/5th >> scale model he built in black carbon, in the wind tunnel. >> >> >> >> We built our wings from Blue Styrofoam, for lightness, possibly reducing >> the empty weight by 50lb overall due to the closed cell nature of this >> foam. But unfortunately, fuel obviously melts this type of foam, so we >> could not build wing tanks, as any leaks would see the wings turn into a >> molten blob. So we have aluminium tanks above our feet in the cockpit. This >> also greatly reduces the complexity and weight as there is no need for fuel >> pumps or electrics or transfer pipes. My main tank contains 24 US gallons >> 90 litres. The engine burns about 18 litres an hour or 4.75 US gallons an >> hour. >> >> >> >> To get across the Atlantic, I needed a reserve tank and built one to sit >> on the passenger seat. It held 45 litres 12 US gallons. For the flights >> through Russia, the longest flight would be 1,100NM. So I acquired four 20 >> litre rubber fuel bladders, another 80 litres 21 US gallons, so I departed >> Nome with 215 litres or 51 US Gallons on board which weighed about 350 >> pounds >> >> >> >> Now there are several problems with using flexible fuel bladders and >> placing them in different positions in the aircraft. I placed three in the >> passenger footwell and the fourth on top of the additional passenger seat >> fuel tank. Ie, as far forward as possible. But since the bladder changes >> shape when you shove it into various places, it is impossible to calculate >> the centre of its mass to enable accurate C of G calculations. >> >> >> >> >> >> We know the pilot and passenger seat loading distance from the datum and >> the fuel tank and the parcel shelf distances. These can easily be >> physically measured. But measuring the C of G position of four additional >> fuel bladders, placed in wherever I could fit them, to complete an accurate >> C of G calculation would be impossible. Hence, knowing how heavy my >> tailplane felt with a known passenger sitting in the passenger seat and the >> aircraft fuelled normally with just light items on the parcel shelf was >> very helpful. Knowing this fuel-laden configuration was within C of G >> limits from previous experience and calculations meant I could do a >> comparison now, with the fuel replacing the weight of a passenger. I could >> tell that the weight on my tailwheel felt similar, but a little more. But >> then the aircraft was heavier in general anyway. So I concluded the C of G >> was beyond the 6 inch range where I would normally fly the aircraft, but >> still with the build manuals 8 inch C of G range. >> >> >> >> We carried out extensive flight testing on many KR2’s in the UK and they >> all seemed comparable. The aircraft have built-in stability up to 6 inches >> of the standard 8 inch range. For my aircraft, the test pilot completed the >> flight envelope by adding and moving around known weights and we took the C >> of G to the 8 inch aft limit. The test pilot’s findings were that, Yes it >> was controllable at 8 inches, but there was no longer any stability built >> in. For the sake of clarity of stability. A simple test, is carried out. >> >> >> >> >> Pull back on the stick to raise the nose and then let go. If the nose >> drops as the speed decreases, but then raises itself again when the speed >> increases again, until the oscillation fades away and stable level flight >> is returned, without need of any other input, then the aircraft has >> stability built in. If you pull back on the stick and let go and the >> aircraft keeps climbing until it stalls, then at that point the aircraft >> can be said to be neutrally stable. At the 8 inch aft limit, the test pilot >> reported that however well you trimmed the aircraft, when you let go of the >> stick the aircraft would divert off in any direction almost immediately and >> would not recover back to level flight and now this is my experience >> also... For these reasons, in the UK we limit the C of G range to just 6 >> inches, removing the rear two inches of the original design parameters. >> >> >> >> So, when departing Nome, the aircraft weighed approximately 1080 lb and >> the C of G - I would estimate, because with the rubber fuel bladders and no >> scales available I could only estimate by lifting the tail, I would say >> that it was beyond the normal 6 in range limit and in the divergent range, >> but still within the 8 inch range that the original design parameters >> permit. The aircraft was not particularly twitchy, but I could not trim the >> aircraft and let go, As soon as I let go, any turbulence would have the >> aircraft heading off on its own. >> >> >> >> Unlike passengers, at the end of these long flights, with all the fuel >> pumped into the main tank and then burnt off, the aircraft was configured >> as if being flown no longer with a passenger, with nothing but empty fuel >> bladders and extra range tanks taking up room on the passenger's seat, but >> adding no weight. The C of G change of the main tank being full to empty >> was 1 inch further forward when full. So this had little to no effect on >> stability. >> >> >> >> So >> >> Empty C of G 15 % MAC >> >> No fuel and one pilot. 27% MAC >> >> Full fuel and one pilot 21% MAC >> >> No Fuel Two 180 lb passengers 35% MAC >> >> >> >> As mentioned, each aircraft has its own individual weight and balance >> sheet. Phil Geohegan carried out wind tunnel tests on the addition of 12 >> inches of airframe forward of the standard design to achieve a usable empty >> C of G positions with the exceptionally light Jabiru engine. There was some >> de-stabilising effect but it was found to be marginal. >> >> And of course, all UK KR-2 aircraft are flown within the specified 900lb >> MAUW within the UK. What you do outside the UK is open to interpretation >> and at the discretion of the country you are flying in. But then no one >> ever asks... >> >> >> >> So any modification to the original design was taken into consideration >> and indeed many of Mike Whittakers stress calculations for the KR2S, where >> he suggested giving the aircraft higher safety factors, they are applied to >> my KR2 aircraft as well. >> >> >> >> The other issue I noted was that carrying that much fuel was very >> inefficient. To climb to FL120 as the Russians requested, the engine was at >> max continuous for most of the flight and burnt a lot of the extra fuel I >> was carrying anyway… Most annoying. >> >> >> I hope you haven't aged too much while reading all this. >> >> >> If anyone wants to read about the flights across America and on through >> Russia, they can be found here. >> >> >> >> https://pilotweb.aero/news/flying-adventure-around-the-world-in-a-homebuilt-kr2-6263956/ >> >> >> https://pilotweb.aero/news/flying-adventure-russia-6274990/ >> >> >> >> https://pilotweb.aero/news/flying-adventure-from-russia-with-permission-6274228-2/ >> >> >> CH >> >> >> >> -- >> KRnet mailing list >> KRnet@list.krnet.org >> https://list.krnet.org/mailman/listinfo/krnet >> > -- > KRnet mailing list > KRnet@list.krnet.org > https://list.krnet.org/mailman/listinfo/krnet >
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