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lelievre12

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lelievre12 last won the day on November 17 2020

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About lelievre12

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    Peter Le Lievre
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    Sausalito

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  1. Thanks Marc. As ever, super informative. I missed the Columbia talk but I think the answer to my question is here: "Can measure MAIN WING AOA to prevent deep stall, but would need to calibrate AOA indicator BY STALLING MAIN WING (that’s not going to happen in any reasonable world and deep stalls can easily be prevented just by keeping CG in the approved range)" However I don't think you need to stall the main wing to calibrate the AOA. The calibration if the AOA could be done in the Phase 1 testing like Chris Esselstyn where he started with FWD CG then slowly worked his way back until the aircraft until started to lose stability and stall recovery was less and less prompt. That setpoint would be what is needed. ie. set the AOA to the comfortable flight limit, no need for the actual full stall. Why would you do this? Well I don't entirely agree with your statement "stalls can easily be prevented just by keeping CG in the approved range". My SQ2000 has a questionable "approved range" which cannot be relied upon. Further, Chris's testing suggested that power on stalls were more likely to provoke a deep stall at an aft CG. Or put another way, accelerated stalls are harder and more dangerous to explore in Phase 1 testing than simple power off stalls. Therefore the AOA indicator can help provide additional input in these more difficult tests pilot so the power off 'comfort' baseline is not crossed. I fly with an AOA in my spam can and have learned much in my circuit work on how close or far I am from the stall in accelerated turns and various weights. The real merit of AOA is knowing what is happening in accelerated dynamic flight, not static straight and level. For example, on a gusty day, its quite alarming what your wing is doing unless you add some speed on short final. And of course the critical base--->final turn is very interesting to watch on AOA if you are cranking her over tight because you turned too late. In a canard at very flight condition you will expect to get a nose drop every time, however knowing the main wing AOA in each of these conditions won't hurt in such a beast as an SQ.
  2. The end result is that the Austra 300 is 410# but the CD170 is around 115# lighter at 295# https://www.austroengine.at/uploads/pdf/mod_products1/AE300FactSheet.pdf http://www.continentaldiesel.com/typo3/fileadmin/_centurion/pdf/Datenblaetter/DS_CMG_2_CD-155.pdf
  3. Years later we can see that the Diamond approach was to use stock Mercedes engines which included the heavier cast iron engine block. Thielerts approach was to replace a lot of the stock engine parts with lighter custom aluminium parts. Even the flywheel was custom and much lighter than the stock engine.
  4. I guess there may be a variable between fuselage attitude (relative to horizon) and AOA unless the plane is carefully flown straight and level? eg. if at stall the plane starts losing altitude then the descent glide angle will need to be added to the fuselage attitude to arrive at the AOA. Perhaps the second Cozy 540 tests were actually not straight and level. If that is the case then I guess the Garmin AOA detection will still work for stall alerting as it detects actual air AOA and ignores attitude. BTW, Chris reports 50KIAS stall speed with rear CG. Will a Cozy really fly that slow? I guess if it is light enough, yes.
  5. A while back we discussed the use of newer 'performance' envelope limiting autopilots now available. Amongst other things one can limit the allowable AOA before the autopilot will nudge the stick forward. For example to keep you away from a deep stall if you are at aft CG. However I was just reading the CG testing of Chris Esselstyn's Cozy 540 RG where he reports; CG of 100.24 – Power off stall, 53 kts, and 16 degrees fuselage attitude CG of 100.57 – Power off stall, 50 kts, and 13 degrees fuselage attitude The above data seems counter intuitive to me where an aft CG sees the Cozy stall at a lower fuselage angle/AOA than a forward CG would. Can someone help me get my head around what is happening here? I would have thought the aft CG would stall at a higher AOA as the canard had more authority.
  6. The SQ2000 factory fuselage was not an advanced mould. It was simply a 'tube' in two halves with no door cutouts, windows, strakes or any other detailing. All this had to be added manually which makes the benefit of 'factory' moulds pretty small. It would be easier and better to CAD up the design, add the window/door/strake detailing and then CAM cut the mould in foam. You can see more at SQ2000.us See these photos: finalresult-flattened.mov
  7. Wow those IGUS bearings look really nice. Ordered two.
  8. Here is a shot of the Lancair IVP trailing edge with that flat cutoff. My recollection was that it was 1/4" to 3/8" On reading some IP (Wainfan Patent) https://patents.google.com/patent/US4867396A/en?q=Wainfan+micro+flap&oq=Wainfan+micro+flap it seems as though the more aggressive cutoff on the trailing edge is more about transonic stability than low speed drag reduction. Something I guess a Lancair might worry about but less so for us!
  9. Kent, thanks for the reply. I will check the wing next time I am at the hangar for reflex on the underside. The N416 wing was foam core (like a Cozy/Eze etc) however my kit came with the alternative molded wing (Lancair style with strakes and no core) and the trailing edge is pretty fat. I think what I will do is bond a 0.5mm strip of carbon on the top edge then flox under to fill the edge. (whilst the wing is upside down). The idea is that the carbon will keep the edge resistant to nicks and hangar rash despite the thinner edge. I am expecting that a feathered edge will be less draggy but read that "Harry Riblett said something about cutting off the trailing edge at 99% of chord length is better than a point for the airflow." so this is confusing me a little. I know that the Lancair IVP I flew certainly had a squared trailing edge that was around 1/4". However my hunch is that this trailing edge is there to reduce high speed aileron actuation forces rather than to reduce drag.
  10. I am finishing my SQ2000 project which has molded (not foam core) wings. The 'as molded' trailing edge on my main wing is a pretty fat radiused edge which is ~1/4" radius (1/2" top to bottom). Looks draggy indeed. Looking at the Eppler 1230 design I see that the trailing edge is 'sharp' so the question is "what trailing edge are other folks using" on their Eppler main wings? I am inclined to fair the rounded edge to make it sharper perhaps down to around a flat aft face/edge of around 1/8". I could go even sharper perhaps by using a thin carbon undersheet with micro to fair the top edge. I would have thought the sharper the better but not sure. I have seen a more blunt edge say squared to 3/8" like a Lancair? Any advice appreciated.
  11. Marc, thanks for the reply. I hadn't read of Whitcomb but have now. Its interesting to note that the 'Typical' winglet sections have outward incidence "i.deg". In Whitcomb's work, this is quite pronounced (7 degree) at the root of the winglet and still 4 degree at the top. I haven't seen this measure of either twist or incidence in any canard wings to date, unless I missed something? Its also interesting to note that the winglet is canted 15 degrees, which again you don't see in canards. Finally, I see that the lower winglet incidence is set to 11 degrees and 36 degrees cant. This seems a lot but makes sense when you think about trying to 'untwist' the vortex before it happens. Your text about full chord lower 'slab' winglets is exactly as I thought. I did read Nat Puffers explanation of them adding "at least 1/2" of aft CG" and I was planning to add them. It seems another example of how the early Velocity SE and SQ2000 designs didn't make the leap from 2 seats to 4 seats very well (like Nat did). However, despite what Nat did, I'm wondering to what extent the Whitcomb 'mini' lower winglets are as effective as full chord. I haven't yet found any data or flight reports but will keep looking. I wonder if Nat tested them? It would seem that an 11 degree incidence lower 'Whitcomb' winglet is attempting to be as effective as full slab (and probably will have the same drag!).
  12. I see these lower 'mini' winglets on older Vari/Longeze. I'm sure there is a long history of discussion about them. Can someone point me where I can read more? At the moment I have only upper winglet/rudders (Berkut/SQ2000/ERacer style) and wondering about the tradeoffs the between nothing, 'mini' winglets and full size lower winglets Cozy/Velocity style.
  13. I think the big issue with retracts is the additional weight. Weight kills speed so aerodynamic gains can be diluted by increased drag from a heaver wing loading. I have to agree with others who prefer fixed gear. However if retracts can be made lighter then the advantage creeps back. I already have Infinity Retracts on my project and just the stock hydraulic pump and solenoids weigh >10 lb. Not including wiring etc That is sooo heavy. . Looking at the history from Lancair etc these old pumps are straight out of your outboard tilt lift from the 60's and migrated to aircraft at some point. Not exactly ideal. Since I have the retracts I am keeping them, however I plan on trying a state of the art BLDC hydraulic pump (brushless DC) which weighs 0.9 lb in an attempt to cut weight from the installation. Here is the current installation. Ill update when I have the new pump installed. The goal here obviously will be to have my cake and eat it too. I
  14. Sheesh. Of course! So the cabin air ends up exiting via the spar. I should have noticed this when I was looking at my airframe. Thanks for your help Andrew!
  15. This is the kind of thing I am thinking of. The rubber 'flapper valves' let air out when pressure builds inside the cabin. Not as big as this air pressure vent from an F150 but same principle.

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