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karoliina last won the day on August 10

karoliina had the most liked content!

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About karoliina

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  • Birthday 05/24/1974

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  • Real Name (Public)
    Karoliina Salminen
  • Location (Public)
    Espoo, Finland, EU
  • Occupation
    Senior SW Engineer / Project Manager / SW Architect
  • Bio
    Flying, composite aircrafts, music (making, listening), Linux,...

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    Diamond DA40D, Diamond DA20, Cirrus SR20, Cirrus SR22

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    Other (Non-canard)
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  1. One little addition: Unlike two surface canard, a tree surface aircraft achieves both: high Clmax and minimum trim drag. Canard only achieves minimum trim drag and low Clmax where conventional achieves normal trim drag and high Clmax. Three surface is a kind of best of both worlds. The forward wing can be also tuned so that it makes the plane stall proof. There is one downside though: the protruding wing in the forward fuselage spoils the airflow over the fuselage potentially causing a otherwise laminar flow to become preliminarily turbulent. However, planes this is compared with don't maintain extensive laminar flow over the fuselage anyway, the fuselage shape has to be like in best sailplanes for the forward section with no joints, protrusions, pitot tube, access doors etc. to achieve the laminar flow potential anyway.
  2. I wouldn't call that poor performance. If the specifications are at all true, it is a very good design in terms of efficiency. 160 kt is fast taken in account the low engine power and low stall speed (stall speed - cruise speed has its limitations). It is also three surface design which can take advantage of flaps on main wing. And from this tandem design, the rear occupant can actually see something. The design seems to be in harmony and putting a O-540 on place of the small engine it was designed for, would essentially ruin the design. Power loading and wing loading are not in a good balance in many experimental aircraft (the design is not very optimized when e.g. the engine is total overkill) but in this case the power loading and wing loading are both quite reasonable - the design exhibits high climb performance while not overdoing the power loading - the aircraft have multiple parameters which affect their performance at the same time, and changing just bigger engine usually will not help (it helps some to some extent, but is not the whole solution), but will rather hamper the sophistication potentially achieved in aerodynamic design otherwise by adding weight and thus cruise wing loading and cruise angle of attack over the optimum value the airfoil selection was made for etc.
  3. This is an old thread, but I just found it accidentally. Interesting topic indeed. You say getting more than 1.6 CL is not feasible. How about this (see attachment) - it is the airfoil used in all Diamond models (from motor gliders to DA-42 Twin Star). fx63137sm.txt
  4. It looks like propably some people have mixed mph and kts and I have interpreted the numbers as kts where they were mph. That sounds like reasonable number. Ok, looks like my basic assumption was wrong. I went to check the cafe report and indeed it stated that the bobbing started at forward CG at 68 kt. So hereby I stand corrected. Thanks for correcting me. That was based on the specs given by the Finnish Cozy Classic -flyer (which may be incorrect or inaccurate): - He uses approach speed 110 kt which is as fast as some passanger jet. I have witnessed that once on board of his plane. It was so fast that I have never been that fast landing on any light plane, e.g. RV-8 used 82 knots as approach speed and it was considerably slower. - 6000 feet runway gets really short - He once attempted landing on 3000 feet runway and his comments are basically that "never again" - My home airport has 4000 ft runway and he don't attempt landing there because he says that it is not possible to land & take off safely from there because there is a obstacle at the end of the runway which makes the usable runway length so much shorter that he just can't make it safely. There is a hill, trees and houses at the end of the runway. On the other end there are several houses, small elevation, high current power lines and pretty tight turn to right to avoid getting out of the pretty small airspace reserved for this airport. - The 2700 feet airfield in Lapland which is one of my favorite places to fly, is completely out of question according to Rauno (elevation 738 ft) even as a solo/light weight. So what I could conclude from that: - The Cozy Classic in question has something wrong with it, w&b, aerodynamically or otherwise - Or it is flown at improperly high approach speeds - Or I am totally confused and don't know what is correct and what is not. I see that the selection of examples I have evidenced is too narrow to draw any conclusions. Maybe I should get on somebody else's plane and see a different view that way. And demonstration of landing & takeoff with forward CG with full load to a 2500 ft runway would really change the whole perspective - the majority of small airfields happen to have runway length 2500 ft - 3000 ft and they are rarely larger and there are often obstacles in form of tall trees in both ends of the runway. Being restricted to only the handful of the large airports would reduce the versatility quite a bit in this country and also add cost by landing fees, parking fees, taxi tickets etc. Things would be so much easier if there would be a lots of large airports around and if one could rent a car from any airport, but that service in general is not very often available except on the Helsinki-Vantaa airport that I do not use anyway (the GA traffic fees are very high on that airport and quite large amount of the days it is closed from GA alltogether). The small airfields add the possibility to go to camping and with the large airports, the vacation would be rather a hotel-vacation only at the handful of biggest cities which by definition is pretty boring in this country.
  5. Just to add some of my thoughts to this thread: - I have Cozy plans (original ones on paper) and I have now LEZ plans too (on CD-ROM). What I can say is that they are almost identical except some text and drawings are redone by Nat, but the part, layup schedule, everything is the same except it is wider. Some things are covered in the Cozy plans in greater detail. Some sentences have been modified a bit and some are exactly the same than on LEZ plans. Some Burt Rutan's original pictures even have ended up in the Cozy plans. The widening has brought some downsides which may or may not affect the choice. In my case, it didn't affect the choice until I learned what the Cozy IV specs actually mean in practise. So the deal is about this: - Long-Ez has longer canard, lighter wing loading on canard, and more aft CG than a Cozy with two persons on front seat Sounds like a little difference. At least it sounded like a little difference in the beginning. However, the thing is that with Long-Ez you have stall speed at around 65 kts. With the two full grown persons on front seat, the stall speed on Cozy gets up to about 80 kts according to reports. The Cafe foundation's report 72 kts is apparently for the original length canard. At least some tinkering with X-plane (yeah, I know it is a simulator only) also concludes that the stall speed is around 80 kts on the most front CG that occurs when you place two times of me on the front. The front CG was verified with Marc's weight & balance calculator. In our use case the CG will get always to about the max forward position. The safe landing speed is usually defined to be 1.3 * stall speed. 1.3 * 80 = a lot more than 1.3 * 65. There is a huge difference if you make your approach at 85 kts or 105 kts. FAR part 23 defines the maximum of 61 kts for stall speed for single engine aircraft. With exception Pilatus has got 65 kts approved, the airframe and cockpit is strong enough to handle 65 kts off-field landing without very high risk of resulting fatalities. Not so surprising thing is that Rutan's plane gets barely just on that figure. However, by widening the LEZ to Cozy and not changing the canard and wings to keep the wing loading the same as in LEZ and the canard is shortened instead, it is pretty obvious that Cozy don't fit into the FAR part 23 stall speed criteria, not even nearly. In fact, Cozy has higher stall speed than Viperjet, Pilatus turboprop or even turboprop Lancair IVP (or any other Lancair model). So what will the higher landing speed then matter? I think it does not matter if you are only operating on large airfields and never get so unlucky that you would need to do a forced landing. However, with slower approach speed and lighter weight when fully packed, the LEZ takes theretically shorter amount of runway to stop. I have never flown in LEZ and I have only once flown in Cozy Classic, so I am not the person to give real world comparisons, but I would assume based on simple logic that LEZ equipped with similar tires and brakes (e.g. Matco brakes) than Cozy, stops in a significantly shorter distance than the Cozy will and therefore provides more versatility on airfields shorter than 4000 feets and also gives more opportunity for interrupted takeoff whereas Cozy wouldn't stop before the end of the runway comes. If that counts something to you, then you might consider Open-Ez. If it doesn't, then you can pack more stuff inside the Cozy and have side by side seating which is useful e.g. if the co-pilot handles navigation and operates radio frequencies etc. and leaves the pilot free from these tasks. If you don't want to experiment but want to get a plane to fly, then go and buy e.g. a Diamond DA-40, DA-50 or Cirrus SR-20/22/... The number of hours marketed is different from the actual number of hours really required - plans built aircraft is what it is, takes a very long time to build and that means a long time by dedicating all available time every day for an extended period meaning no movies, no tv, no fun, no nothing but doing the plane. I have found out that managing time for allocating time for building the plane is very difficult for someone working in demanding day-job where days can get longer unpredictably etc. And the simplicity marketed is different from the knowledge required to complete the project in a meaningful time period. You have to know a lot and if you don't know, you have to gain the knowledge. That is on the other hand one of the major reasons for building an aircraft - to learn.
  6. Maybe prototyping an aircraft then costs about the same despite on which class it is intended for and the parts cost is not the major factor on the prototyping price. Burt Rutan allegedly prototyped & flight tested Adam A500 twin predessor for one million USD (information from Adam Aircraft web site - based on the quote of Burt's alleged statement "This is going to cost you one million bucks".
  7. Hi, Our X-plane computer is now set up. The version is 8.40 Linux. We would be eager to test Cozy MKIV if we could get one from somewhere. Computer specs: - AMD 64X2 4200 - 2 GB RAM - Nvidia Geforce 7800GT (256 MB) - 550 W passive cooled power - Passive cooled SLI mainboard - Watercooled enclosure With "INSANE" -settings all on, it reaches around 24 fps at 1600x1200. With standard settings it goes over 100fps. Best Wishes, Karoliina
  8. Hi, Me too wants the X-plane 8 version of Cozy since we just bought a new computer to run X-plane (AMD Athlon 64X2, 2GB RAM, Geforce 7800, water cooling). It would be suboptimal to use the older version as the new version has so much more nicer scnery etc. X-plane 8.x (currently in version 8.40): Best Wishes, Karoliina
  9. I made that assumption based on the fact that Greg Richter does not go faster than 200-240 kt with his Cozy-Jet according to the article. That is not very much considering that there is a lot of more power available in the jet engine than there is in a piston engine (no matter what horse power) at the same altitude. I may be also incorrect with the assumption, but to me it sounded like the drag starts to rise exponentially above the normal speed range of the canards because the airfoils are not designed for a such speed range. As a matter of fact on the other hand, I am not aware to which speed range the airfoils of Cozy are designed to and would appreciate if somebody with more knowledge would enlighten me. Best Wishes, Karoliina
  10. One thing to consider is: - Canards have currently quite thick wing profiles. - thick profile = more drag - it is thick because of the strength required and it is achievable only with a thick profile if glass is used. - with carbon it would be possible to use thinner profile - with increasing intentionally the lift of the fuselage, maybe the wing span could be reduced a bit too. - the Eppler 1230 mod is a thick turbulent profile and propably quite draggy (haven't tried to simulate it or anything), a person like John Roncz would be capable of designing a new less draggy laminar profile for a replacement I am sure. In a very draggy airplane, the wings create something like up to 60% of the drag of the airplane. Replacing the profile with a faster one, which would be better optimized for the higher cruise speed. With the current profile, adding power does not help much. For example Cozy-Jet isn't very fast compared to how fast a jets usually are. If the drag of a profile increases exponentially above certain speed, you could be using a Saturn-V rocket engines and still be slow. I am quite convinced that making the plane faster, requires to change the wing profiles, in addition to making the fuselage etc. smooth. Small optimizations help a little, but new wings and canard could help significantly (IMHO).
  11. dpaton, one does not need to be a structural engineer to understand that this yardstick example is preaching and not based on any engineering, otherwise everybody would be building their wings from gum. The fact that something is less flexible does not make it less strong since it is about static load and not static flexing that is measured. In other words, one could build a wing out of carbon fiber and it would fail with lesser amount of flexing than a e-glass wing. However, it would require lot of more force to flex the carbon wing enough to make it fail. And the more the wing flexes, the more at risk is the foam inside to either break or separate from the skin. If that happens, the strength of the sandwitch is lost immediately "bam" and the wing will fail. The blue foam can flex to certain extent without failure, but after that, the failure happens immediately without warning. I have my doubts if Burt have ever said this thing which appears in the "Howdy Burt, I Fixed Your Puny Spar", the real story is propably something else and the reasoning is propably something else than presented in the story. I had some structural engineering in my engineering studies, but I have largely forgotten the equations etc. we were using about everyday. However, the one thing that has remained (as common sense) since reformatting my brains with C/C++/etc., is that with thinking it even a little, the claim represented in the article you are referring to, can not be correct. If you do not believe, you can do a test laminate and test with static loading which part fails earlier. The strenghtened part fails later despite its flexture at failure may be less, especially if the material is carbon fiber. If somebody strengthtens some component, he or she needs to take account also does it require some other reinforcements. Fixing wing in one place can make it fail from another - it needs to be strenghtened equally and of course the core material is one important thing that contributes to the strength of the resulting sandwitch. There are better structural foams than blue styrofoam out there in that sense, but for the construction method (hot wiring etc.), the blue foam is irreplaceable. Karoliina
  12. Sounds cool. Actually something I have planned. Lets setup openaero.org and put wiki engine and mailing list running on there. If you want server space, we can offer that for free from our server (www.katix.org). We can also offer free name service without backup name service (we don't have ns2 running since it would increase the electricity bill too much for no real redundancy). The downside with our server is that it can be down now and then couple of hours, no backups are done usually and nothing is really guaranteed with it. Good thing is that it is free for projects like this and all you need to do is to say yes. Some other server would propably be better, but I can offer this if something else is not available. The plans could be licensed under Creative Commons license, it would define rules how to use the design and guarantee that nobody could sue about any ownership stuff ever (avoid things like Cozy vs Aerocad debate some time ago) and it could be also defined with that that the implementations based on these plans come with ABSOLUTELY NO WARRANTY OF ANY KIND .
  13. Wasn't Opus-3 an original canard, so it is not really a Cozy-mod(?) and differences in it are not directly applicable to Cozy.
  14. karoliina


    I am just curious since I am not planning to build IBIS. How it is possible to equip IBIS for night-VFR with €25k? I am interested because what I have learned from CAA here, is that night-VFR requires certified aircraft engine and certified propeller (propably a Lycoming IO-360 + MT Propeller, with EASA form 1). (I am building Cozy MKIV). I don't see how it would be possible to fit certified engine + certified propeller + propably certified instruments and the airframe to €25k in case of IBIS. Therefore my question is that are the rules for night-VFR less strict in Germany than in Finland? Usually rules that apply in Germany are adapted later in Finland, and if it is so that it is possible to get a plane good for night-VFR without certified engine and propeller, it could mean possibilities of significant cost savings. Best Regards, Karoliina Salminen
  15. Didn't Dan Patch have Rotax 914 in his Vari-Eze? I have Rotax 912UL in my TL-96 Star. Rotax 912ULS (100 hp) would be fine for Vari-Eze I think. For bigger planes like Cozy it would be underpowered. Used Rotax engines are hard to find and usually people just buy new ones. The 912 can not be rebuilt, it has 1500 hours of lifetime and at that point it is returned to Bombardier-Rotax as an exchange for a new engine.

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