Marc Zeitlin

This is not an unreasonable analogy - as John Slade said, the rate of shoveling would be equivalent to the RPM. The "static" thrust is a combination measurement of the engine power and propeller blade size/pitch settings. "Climb" props will have a much larger static thrust than "cruise" props on exactly the same engine, but will obviously not obtain the higher cruise speeds. The Thielert engine/propellor combination runs at lower RPM with a very different propeller than the O-320 setup. In order to fully compare the two installations, you'd need to see the full graph of climb vs. weight data as well as the top speed vs. weight data. It's very possible that with the current Thielert setup that the performance of the plane with the Thielert engine will be as good (or even better) than the O-320 for the following reasons; even with 15 HP lower THEORETICAL, the Thielert is turbo-charged, meaning that it will put out it's maximum power all the time, while the O-320 will be density altitude limited. If they've tuned the prop for climb (or even used a CS prop), the Thielert will have a better climb rate and roughly equivalent cruise speeds due to the better ACTUAL power output from the turbo-chargine. If you turbo'd the O-320, you'd get better performance than from the Thielert. That certainly looks like a good diesel candidate, but it weights 185 kg dry, or 407 lb. This is more than 100 lb. MORE than an O-360, and that's without the radiator/coolant/PSRU. You'll need the PSRU to get the speed down from the 4000 RPM to 2700 RPM or so. If you say that the fuel burn is 12 - 15 lb/hr. less than the gasoline engine, you could claim that you could reduce the size of the fuel tanks by 75 lb. or so, and get back most of the difference (not counting radiator/coolant/PSRU etc. weight). You might have a difficult time doing the W&B, with the extra 100-140 lb. so far back, however.

That's the plan, thanks. Geez, you know, if you had asked me this in 1995, when I started building, I would have said "you bet" - I saw two likely contenders at OSH that year. Now I can think of Deltahawk, Zoche, Continental, and SMA - I'm sure there are others, too. However, the Deltahawk is, AFAICT, a shoestring operation that has made almost no progress in the intervening 8 years. Zoche has likewise made little progress, and the price is out of sight anyway. IIRC, continental's entry is now on the back burner, and I don't know what SMA's status is. So, is it possible? Sure. Would I hold my breath?.........

I wouldn't say that it's "left over" from cars - cars have a different operating environment than aircraft, and torque AND HP have more of an effect on the performance of automobiles. Acceleration is a function of the torque output, and having lots of torque at low RPM (starting from a dead stop) is important to a car/truck. Aircraft engines do not operate at low RPM (relative to their max. RPM) - they're always at ~75% RPM or more when you're trying to get power out of them. Cars might easily be at ~15% or less of max RPM when you're accelerating away from a light. Cars are also usually operating at much lower than maximum torque levels, so that when you want to pass on the highway and you step on the gas, the difference between the operating torque level and the maximum available torque level at the operating RPM is what will determine how quickly you can accelerate. Aircraft are almost alway operating near max. available torque and max. available HP. The operating environment has a great deal to do with what's important to measure. Your turbodiesel putting out 178 HP at 2700 RPM would be completely appropriate for a COZY MKIV (assuming the weight was reasonable), if such an engine were ever to become available. My response was to the claim that torque was important, and HP not - it had nothing to do with whether the HP came from the Otto cycle, Diesel cycle, Rankine cycle, Sterling cycle, or hamsters in a wheel. God had nothing to do with my post, nor with the relationship between HP and torque, and AFAICT from your response here (as well as your previous ones), there's only one ignorant bastard on this forum. As you can see from the followups to my original corrections to your misleading statements, many people do, in fact, appreciate having the theory and data explained to them so that they don't remain ignorant. Especially when the data comes from someone that's not hiding behind an anonymous moniker, and claiming omnicience.

By definition, no. Since: HP(crank)=Torque(crank) x RPM(crank) If you set HP and RPM, then the Torque is defined. Pick any two, there's only one answer for the third.

Popular misconceptions about Torque vs. Horsepower abound. These types of discussions occur on a regular basis on the rec.aviation.<your pick> newsgroups. The statement above is incorrect. Torque IS a rotational force, but HP is the ONLY thing that matters, as long as you have a PSRU to ensure that the propeller turns at the optimal rate. Here are the equations: HP(crank)=Torque(crank) x RPM(crank) RPM(prop) = 1/N x RPM(crank) where "N" is the gear ratio of the PSRU Torque(prop) = N x Torque(crank) The HP and Torque produced by an engine are NOT independent - look at the Torque-RPM curve for any engine at WOT. There is only ONE Torque and ONE HP output at a given RPM. An O-360 produces 350 ft-lb of torque at 2700 RPM, for a power output of 180 HP. At 2200 RPM, it will produce 150 HP and 358 ft-lb of torque. Let's compare this to the Subaru EJ-25 engine, which has a maximum torque of 162 ft-lb, as shown at: http://www.protekperformance.com/rv7/engine/dyno_graph.htm Holy crap - if torque is what we care about, this bites the big one in comparison with the 60 year old Lycoming design - it's less than half the amount of the O-360. However, it puts out 165 HP - almost as much as the O-360 - how can this be? It does it by producing the HP peak at 6000 RPM at 150 ft-lb of torque. You need a PSRU with a ratio of about 2.2, so the RPM at the prop drops to 2700, and the torque at the prop INCREASES to 330 ft-lb - close to the O-360 #'s. So, let's take a look at the Thielert Diesel. It claims 135 HP at 2300 RPM, for a torque of 308 ft-lb. Not as much torque as the O-360, but twice as much as the subaru - wow - a COZY should SCREAM with this puppy, yes? Wait a minute - that's at 2300 RPM, remember? Use a PSRU with a ratio of 0.85 to get the prop RPM back up to 2700 RPM, and the torque at the PROP drops to 262 ft-lb. Less than both the O-360 AND the subaru. This is NOT surprising - the HP is what counts. What "us aviators" care about is power delivered through the prop to the air as a motive force. This comes from the POWER output of the engine, transferred through a PSRU if necessary. There are many books that explain these relationships, and a simple primer is online at: http://homepages.bw.edu/~katchins/csc131common/a_papers/student2/torqueHP.htm

I worded my response poorly - what I meant was that the COMPUTER CONTROL was unnecessary, since the only thing that was controlled by the throttle WAS the fuel supply, and hence the mixture, with the RPM being dependent upon the load. It will be set by the load, the throttle setting, and the torque/speed curve of the given engine at a given throttle setting.

IIRC, diesel engines do not have a throttle plate, and control power by setting fuel flow. Airflow is set by RPM, so effectively the "throttle" IS the mixture control, and you can have extremely low fuel/air ratios at low power settings without a restriction in the air intake, which is one of the reasons why diesel engines are more efficient than otto cycle engines. You are correct that in an otto cycle engine with a single power lever (like any car built within the past 20 years) that the computer will set the mixture ratio, but that is not necessary in the diesel engine. It's a lot simpler, and not dependent upon fuel injection for the single power lever.

I'm going to try real hard to be calm and diplomatic here. There is a mailing list that exists in which one of the criteria for joining is the submission of email and real addresses and phone numbers, so that people can contact each other for help/communication. People are told that their information will not be either distributed outside the mailing list, nor will their information be used for ANY commercial purposes. This forum does not require that any contact information be supplied. That probably means that more people will join, since the opportunity for anonymity (and unaccountability) exists, but it also means that there is no easy way to check a database of phone #'s or addresses, or even email addresses of people in a certain geographic area. I have a real problem with using information collected in one group (under certain pretenses) for distribution in another group. I would say that one would jeopardize their membership in the COZY mailing list if they distributed confidential information from it to anyone outside of the list, UNLESS one obtained the explicit permission from each of the people who's email one intended to distribute beforehand.

In 1995, when I started building my COZY, I went to OSH. I saw the DD there and liked it. It was only a year or so away from readiness at that point (as was the Zoche diesel, and who knows how many other engines). When I went back to OSH in 1998, the DD was about a year away from readiness, and was mounted on a Velocity (sans wings) doing some taxi test/demos. If they're saying (in January, here) that they'll be ready to sell them by the end of the year, it's apparent to me that they've got a slip rate of almost exactly "1" in their scheduling over the past 8 years at least, and that based on that, you should look elsewhere for your engine needs. Undercapitalized engine manufacturers starting from scratch are a poor place to look for the most important single component of your aircraft. At least the rotary, Thielert and Subaru conversion folks are starting from known good engines, and the Continental and French (can't remember the name off the top of my head) diesels are well capitalized.

John Slade says: "The last thing we need is another place to check for information." All I can say is that I'm flabbergasted by the irony of this statement.

Evan asks about VFR --> IFR setups: I have a UPSAT SL-40 COM purchased new (~$1300). I also have a used Narco AT-50A transponder purchased used (yellow tagged) off EBAY for ~$500. They both work great, and along with my Garmin 195 handheld GPS (also purchased used on EBAY for ~$600), I have all the VFR avionics I need. The SL-40 has a standby frequency that can be monitored while on primary, so it's like having 1.5 radios. I also have a ICOM-22 handheld as a backup radio/NAV (it has VOR/CDI built in). I wouldn't go NEAR Narco for new equipment - both UPSAT and Garmin have advanced substantially past Narco's capabilities and size. You do NOT need Mode-S, and (hopefully) it'll be a LONG time before it's mandated, if ever. If I ever want to go IFR, I'll install a Garmin 430, and I'm good to go. With respect to MT's laptop setup: There are many moving map applications that already exist - unless you're somehow going to advance the art, you can buy one for well under $200. Also, the laptop is hardly the "expensive" part of your aircraft - the radio/Nav/Transponder stack and Gyros will be much more. General purpose laptops screens are nowhere NEAR bright enough to use in bright daylight without a hood - that's one of the reasons that outdoor readable LCD's are so expensive. I'm also unwilling (after 10 years of using NT/2000) to stake my life on a Microsoft product, and I'm not sure about Linux either. Evan, if you only want a VFR setup to start, a handheld GPS such as the Garmin 195/196 is MORE than adequate - you don't need a panel mount, and they're less than $1K. They also have good resale value if you do ever put in the EFIS, but I'd keep it as a backup - it's got a lot more functionality than just a sectional if the EFIS fails. With respect to the integrated CDI's (such as on the UPSAT SL-30), that only works for the internal NAV, and is only good for VFR navigation - they're not approved for IFR (and obviously have no GS).

MT asks about Vne and top speeds: You are forgetting that Vne is in IAS, and Cruise speeds are in TAS. There is no COZY around that has enough power to operate at IAS's of 220 mph (~192 kts) at altitude. See the performance graphs for the COZY at: http://www.cozybuilders.org/performance/cruise.html You can see that at 7000 ft., max IAS is 180 kts., and at 14,000 ft., max IAS is 162 IAS. This says nothing about TAS, which must be calculated, but you won't bust Vne except in a dive with a 180 HP (or even 200 HP) COZY. Evan Kisbey asks about cowl flaps and surface finish: Cowl flaps are doors which control how much air goes through the engine cowling. A large portion of the total aircraft profile drag is cooling drag caused by airflow through the engine compartment, and the airflow is sized so that at low airspeeds, there's still enough air to cool the engine in a climb. At high speeds, less cross sectional inflow is needed, since the mass flow of air is much higher. Cowl flaps are usually placed at the inlet to the cowl to limit the air intake at high speeds, and thereby reduce cooling drag. Other than the canard, the surface finish is completely meaningless. That's the only laminar flow region of the whole plane. It'll look like crap, but you can have weave showing everywhere and you will have a hard time measuring the speed difference. I've never heard of "ambient drag" - sounds like something from the Beach Boys "Pet Sounds" album. Dust asks about TAS at 15K ft., using Jim Sower's calcs as a starting point: As Jim points out, turbo-normalizing will get you back to 100% power (up to some altitude, depending upon your turbo and waste gate). If we check the web page indicated above, we can see that at 14K ft., the IAS is about 162 kts at 2800 RPM, but this will be about 60% power, due to the decreased air density. If we want to get back up to 100% power, we'll either need a different prop (or a CS prop) to keep the RPM below 2700/2800, and we'll get about 18% more airspeed out of the 66% more power. This will get us an IAS of 191 kts at 14K ft., which is about 240 kts TAS or so. Remember, this is at 100% power - you won't be doing this for long. This is also right about at the Vne (220 mph = 192 kts), and at altitude Vne will slightly decrease, so this would be a really bad idea unless you'd like to do extended Vne testing. Hope this helps.

Just as a clarification in response to Matt Evans' post, I have NOTHING to do with the CA list, which is moderated. I ONLY administer the COZY list. If you have problems with something going on on the COZY list, I'll be happy to listen and attempt to fix the issue. If there's a problem with the CA list, I can't help you - I'm only a member there, just like here. And thanks for the continuing input.

MT asks about retracts, spinners and 220 HP engines. I don't believe that there is anyone flying a COZY MKIV with THAT configuration, so any projections of speed will be just that - projections. While there may be some questions as to whether wheel pants add 6 or 10 mph, the contention that speed is related to the square root of power is incorrect - actually it's related to the CUBE root. The drag force is related to the square of velocity, and power is force x velocity, so the power required is related to the cube of the speed. This is modified by the fact that we're not only considering profile drag, but induced drag as well. Although in theory induced drag decreases as AOA decreases (speed increase), every airfoil has what's known as a drag bucket (you glider flyers will be familiar with this term) meaning that there's a small range of AOA's within which the drag coefficient of the wing is minimized. As the AOA changes in either direction, the drag can go up considerably. What do these facts imply? Let's assume that a standard COZY MKIV with wheel pants, spinner, and 180 HP engine can top out at 220 mph TAS. If we just increase the power to 220 HP, and make the assumption (incorrectly, but it's all we've got) that the induced drag doesn't change much, that's a 22% power increase (1.22 times as much). Since speed is related to the cube of power, we should see a speed increase of 1.22^1/3 x 220 = 1.07 x 220 = 235 mph, or about 15 mph (7%, at these power and speed settings). Nat didn't see this on his plane, but it's not at all clear that his installation was ever developing full power, or that he had the appropriate propeller for the Franklin. I wouldn't use his installation as an indication. The gear retraction will reduce drag considerably, but since power is LINEARLY related to the profile drag coefficient, reducing drag and increasing power are both related to the cube of speed - a 22% reduction in drag will also give a 7% increase in speed. Hope that clears things up somewhat.

With respect to cruise speeds, you'll see a lot of variation because sometimes people are referring to COZY III's and sometimes to MKIV's. Some people have wheel pants and some don't. Some have spinners and some don't. Some have the GU canard and some the Roncz canard. Some have climb props and some have cruise props. I have a 180 HP MKIV with the roncz canard, Catto 3-blade prop and no wheel pants. I've seen TAS of 204 mph so far, and I'm told that wheel pants will add 10 - 12 mph to that. With respect to Vne, the published Vne (as shown in all the literature and owner's manual, as well as the web pages) is 220 mph IAS. Part of the confusion stems from Vne being measured in IAS, while cruise speeds are measured in TAS, so you see people cruising at 220 mph while the Vne is 220 mph, but they're in different measurement systems.

The unknown marbleturtle spoke thusly: You obviously don't know me, and have decided to turn this into a personal battle, rather than the open exchange of information that you claim to desire. As you yourself have pointed out, you had two ways to interpret the questions I posed, and rather than assume the best in others, you chose to assume the worst. This says far more about YOUthan it does about me. Others that have known me for years have responded in my defense - I won't bother (thanks to Rick Maddy and Nick Ugolini). You are, in fact, an "ignorant" newbie, but ignorance is neither shameful, congenital, nor permanent - it can be easily fixed by gathering information. Stupidity and meanness, however, are much more difficult problems with which to deal. You claim to be an opinionated know-it-all, and your response here proves that false - at least the second part. Had I wanted to ridicule you, anyone else, or the forum, I would not have chosen such a circumspect methodology. As it turns out, some of the other more reasonable members of this forum have provided succinct, meaningful replies that do, in fact, explain some of the advantages that people find here. I'm not sure I buy into them completely, but it certainly is possible that within a few years, the mailing lists will die out and the web forum will take over. If other people have more feedback regarding the pros and cons that's different than what's already been stated, I'd certainly be interested in hearing it. BTW, Both Merriam-Webster and Webster's New World dictionaries defines the plural of "forum" as "fora" or "forums". No mention of "forae", I assume since we're speaking English here, not Latin. Once again, the "opinionated" part of marbleturtle's signature may be correct, but......

So I've been monitoring this CCF for a few months now, first as a visitor and for the last month or two as a member. This is my first post. What I'm looking for is feedback regarding the relative appeal of this forum vs. the canard_aviators and COZY mailing lists. I guess mostly what I'm looking for is an understanding of what advantages this forum has over the two mailing lists - other than the emoticons, I'm having a difficult time seeing any advantage whatsoever. What I DO see, though, is a lot of repeat discussions (from a historical standpoint - witness the paint color one) in which incorrect information is disseminated and not corrected. I see many newbies asking questions about anti-ice systems, pressurization, and turbines. These questions are valid ones to ask, but the depth of knowledge vis-a-vis responses to them just doesn't seem to be available on this forum (or else those who CAN respond knowledgeably don't seem to do so, possibly because responding on THREE fora is a lot more work than responding on one, or even two). I'm not trying to disparage this forum or it's methodology - if there ARE major advantages, then maybe the members of the other two fora should be migrated (slowly or quickly) over to this forum. If, however, there AREN'T major advantages, then it would seem to me that it would better serve the members of this forum, especially the non-builder newbies, to join one or both of the other fora instead. So, what do people find are the advantage (or disadvantages) of this forum vs. a traditional mailing list? Why are people interested in being on two or even three discussion fora that have 80-90% topic overlap? Thanks for any insight.