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marbleturtle

IVO Prop?

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I think that No4 had done a pretty fair job at attacking the problem. Now any of us can take his calculations and tweak them to use actual numbers as they may apply to us.

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Cheers bro,

I forgot to mention all those calcs for the weight didn't take into into account fuel burn, so even more fudge factor.

:D

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No4,

I was a bit harder on you than was necessary or appropriate. When I read your post, I was coming off one of those "bad hair days" and lost my cool. My apologies.

 

As to your science, it is somewhat incomplete and often missing supportable values for some critical parameters (most notably, power available at altitude). Your equations like power = thrust * speed are true enough, but some of your projections might be best described as "a bit fuzzy". Everyone on this list is long since aware of the science you quote. My introduction to to the entry level aerodynamic principles you allude to was in my high school physics class nearly 50 years ago. Sadly, there is a bit more to it than that.

 

A lot of your projections play fast and loose to some extent or other from the constraints of Newtonian physics or practical applications. Some of them, like "climb to some severe height to make 90 indicated equal 270 knots true" make one wonder where you get your atmospheric information. Others, such as "I'd imagine it's not going to be worse than the already excellent 2500 feet per minute ... Climb rate decreases with altitude, so give 20 minutes for the climb to FL250 ???" ignores a good deal of the "science" you qoute earlier, as well as the climb data in the CAFE report you referred me to (which I, and most of the rest of us, had read several years ago). You regularly ignore or significantly understate the power lapse a reciprocating engine suffers with increases in altitude. I saw no reference at all to the "overhead" or power absorbed by the process of turbocharging a reciprocating engine. You often lose the distinction between IAS and TAS, particularly when discussing props. There is no mention at all of Mach Number associated with propeller tip speeds at altitude. Your projection that "$10,000 on motor = + 100 knots" is, of course, utter nonsense.

 

Your statement that ...

<... I think you will find that it is the power to weight ratio that controls top speed ...>

is not news to anyone that I know, and your ...

 

Some interesting propeller driven figures

ATR-72 4000hp -20000kg-5kg/hp=250ktas

Bae Jetstream 2250hp-9000kg-4kg/hp=300ktas

Fairchild Metro-1500hp-7000kg-4.6kg/hp=300ktas

Beech King Air-1500hp-6500kg-4.3kg/hp=300ktas

Beech Starship-1800hp-6500kg-3.6kg/hp=300ktas

 

... are interesting (to me) only to the extent that they are relevant. I'm not up to snuff on cabin class twins, so maybe you can help me out ... which of the planes on your list have reciprocating engines, and which have fixed pitch props?

 

My Cozy TurboDiesel-300hp-1000kg-3kg/hp=300ktas

in 2005 and you can eat my Kero fumes if you don't believe it.

 

Perhaps I can be forgiven if I take a "wait and see" attitude on that one ... like I'll believe it when I see it. You see, some very good engineers with lots of money have tried to get 300 kts out of a Cozy, and s far as I know, none have succeeded (with the possible exception of Greg Richter, who recently abandoned his turbo rotary power plant for safety and reliability reasons).

Your inference that a newbie off the street, with a slide rule and a very rudimentary knowlege of physics and aerodynamics can achieve this goal with off the shelf parts (that have no extensive documentation on their performance) implies that all of the rest of us, who have been trying for years to go 300 kts, are some kind of doofus neanderthals.

 

I wish you well. If you can do it, so can many of the rest of us (one of which is me). We will all benefit from your triumph. I'll have to put my money on the folks who are a little more well read and experienced. I'll just have to take my chances on the kero fumes.

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Greg Richter, who recently abandoned his turbo rotary power plant for safety and reliability reasons

 

Where did you get that from, Jim? Did Greg tell you this?

When I last spoke to Greg he told me he was removing the 13B to install a turbine. He made no negative comments about the 13B.

 

I guess every good rumor has to start somewhere...

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I was talking to Steve Wright at RR last weekend, asking him why Greg gave up on his rotary. Steve said that Greg had a couple of dicey failures that seemed to have spooked him. Said "... he didn't trust it any more ..." which can mean different things to different people.

 

BTW, how fast had Greg gone in his Cozy? I didn't keep up with it well at all, assuming that when he got it all squared away he would publish an article in KitPlanes or Sport Aviation or something like that. I also talked to Turbo Tom last weekend (who seems to have been involved to some extent in Greg's development effort), and he expressed disappointment that Greg hasn't said a word to his knowledge. I should be in contact with Steve again soon - I'm going to join the EAA chapter he's in - and I'll see what I can come up with by way of details.

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Let us know what you find out. I'm leaning toward a rotary and if he's had failures of some kind, I'd like to know what kind so as to come up with some sort of remedy or contingency or something...

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Exactly. I'm sure the failures weren't related to the mechanicals (engine, PSRU), but ancillary systems (fuel, ignition, etc.) but I don't have any specifics. You've got to understand - I've already told you more than I know, and there is the possibility (though I think it's remote) that I'm talking out of school. I'll try and get some more reliable info from Steve as soon as I can. Don't know but what I've missed this month's EAA meeting but I'll check with him tomorrow.

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I know he had a vacuum pump failure early on, and I think he had a bit of a drag induced speed wall from all those scoops.

 

I'd have thought that the best way to "come up with details" would be to speak to Greg himself. Third hand info is not what we need here.

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Jim,

You accuse me of treating the others on the board as "some kind of doofus neanderthals." I'm not sure how you come to that conclusion, and I must say that I am offended. Further more you have accused me several times of being " on instruments (in the sense that there is "no visual reference to the horizon when you have your head up your ass") "; and of course " At least nodding acquaintence with Mr. Newton would help too".

 

It has been interesting to chat aerodynamics with you, as every criticism of my posts has led me to double check my workings, which I have found to be spot on every time. It seems from your replies that I should include a huge thesis every time I post. But then again I'm not sure you even read my posts, as reference in your last critique "There is no mention at all of Mach Number associated with propeller tip speeds at altitude". I wonder how many times I have to post that props become inefficient at 300 knots due to transonic flow on the tips. I have also discussed some of your posts with a 757 Captain, a 747 Flight Engineer, and several instructors, the reaction has been either a guffaw or a worried look.

 

You also say "Everyone on this list is long since aware of the science you quote." I wonder if that is true? I some how doubt it. I havn't seen the like posted on this site. Judging by the questions from people like Dust and Marble I believe this to be true.

 

Furthermore all that I know about you is that you are rude and arrogant as a person. As a self proclaimed expert you show little understanding of what is going with aircraft. From surfing this site I see that you have run out of fuel 6 miles from an airport, had another fuel emergency, narrowly escaped a burning aircraft, your velocity overheats, at idle you make 20 knots, your long EZ needs repairs from hitting a hangar after you hand started it with no brakes and full throttle, and, my personal favourite, that the doors fell off the Velocity you built yourself.

 

(A paste of a post from another thread)

 

"For hours of excellent entertainment, ask Jim about his experience with the gull wing door.

 

His starboard door recently departed the airplane at 400 ft on take off and made a dent in the port strake. Come on, Jim - tell us the story about you fighting off flying sectionals and other cockpit debris while trying to recover the pax headset before it went through the prop. Reaching across you're body with you're left hand, while flying the airplane with you're right (from the left seat). Dont forget to mention the bit about recovering from a dive 50 ft from the trees.

 

Oops. Sorry. Did I spoil you're punch line?"

 

Enough said I think.

 

You claim to be an ex Marine Corps Jet Jockey. I would say your abuse is unbecoming of an officer and gentleman, and that I have serious doubts of your claim to 4000hrs in the Cougar.

 

As for holding a multi instrument instructor rating, I don't think so.

 

I would suggest to all on this forum again that they disregard your advice.

 

Can I name a 300mph, 300hp, light aircraft with a fixed pitch?

Sure can! I'll give you a clue,

http://www.berkutengineering.com/pages/aircraft.html

 

 

Cheers

 

 

 

 

 

:D

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I asked the man himself what his experience was with his rotary conversion for his Cozy III... this was his response.

 

<quote>

 

Hi Tim,

 

The rotisserie working just beautifully in the plane, and I was very happy

with the performance I got. Tracy's redux drive and EC2 injection system

is flat out _the_ way to go.

 

I still maintain that the Wankel engine is the best solution for turning a

propeller. If I build another prop-driven airplane, which is likely, it'll

be Mazda powered.

 

The real issue I had with the whole thing was that since I flew one of the

very early and I think the first successful turbo aero-Mazdas, I had a

rather a lot of developmental engineering to do that resulted in a lot of,

well, half-assed parts that worked, but were hell to work _on_. Getting

the cowling off was a two man job that took an hour, for example.

 

To finish the install and make it as easy to wrench on as it should be

would eat up several months time and a big stack of bucks. Robert and

Valerie came across a reasonbly priced (well, sort of) jet engine and I

thought why not? Hence, now the Cozy Jet. Here's a pic from last month so

you can see what we're up to.

 

Mazda power is a good solution, as is Diesel, but jets is jets, you

know? Stop in in a few months and we'll go for a serious canard ride!

 

-G

 

</quote>

 

Jets is Jets? You gotta love this guy! :D

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Thanks for getting REAL first hand info, MT. I didn't think the rumors were accurate.

 

Knowing Greg I suspect the real reason is that he gets bored if he stands still (literaly or figuratively) for more than 15 seconds.

 

Jets is jets. Cute. Next it'll be a rocket and he'll be going for the X prize.

 

Jim. Next time you find yourself typing "I've already told you more than I know" suggest you go back to the top of the post and start deleting stuff. :D

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Can you say R-E-N-E-S-I-S?

 

240bhp, better seals, 40% less fuel consumption, 50% less oil consumption. Still a 2-rotor, lighter, and smaller.

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I stand corrected. I thought Steve was a pretty good source. I don't think I misunderstood him, but I have to entertain that possibility. In retrospect, it did sound out of character for Greg. Guess I need to think these rumors through and verify better before I "publish". I'll be much more careful in future.

 

<<seriously blushing>> Jim S.

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Ivo has a VERY bad name in the canard community - some of it deserved and some of it not. The basic problem has to do with shedding blades. Basically, the blades are not structurally connected to each other. Each blade has two bolts holding it on the airplane, and there is a gap (however small) between adjacent blades. This is a fundamentally shaky situation, that can be alleviated (if not eliminated) by meticulous and frequent torquing of the blades. To monitor blade relative movement, there is a piece of tape across the interblade gap of each blade that is to be inspected on preflight. If the tape is broken, the prop is hard down until the PROBLEM that CAUSED the tape to break (the blades to separate) is corrected.

 

The serious problems (as in accidents) have all occurred on O-360 engines that are notorious for vibration and torque reversal. These conditions are much reduced on a 6-banger, and virtually nonexistant on a rotary with redrive. Pusher applications involve much more flexing than tractor applications

 

The most infamous fatal accident involved a Velocity that had the pitch motor run away to full coarse pitch. The guy field stripped the prop, disconnected the motor, ground adjusted the prop to fine (T/O and climb) pitch [improperly I hear], reinstalled it [improperly I hear], torqued it [improperly I hear, or not at all] and launched on a longish (three hour or so) flight at night. The prop shed a blade and he and his family were killed. There is no doubt that he was flying on instruments (in the sense that there's no visual reference to the horizon when you have your head up your ass...) but the fact remains that a Performance or Catto prop CANNOT shed a blade unless you break it by passing a large, structural object (a Catto prop has survived the shedding of the lower cowl of a Long-EZ) going throuh it.

 

The design is fundamentally delicate. This can be Compensated for, but I personally would prefer a product that doesn't require so much compensation. From a performance perspective, it is pretty marginal as a "variable pitch" prop since only the outboard portion of the blade (that is physically twisted by a torque rod driven by the electric motor) changes pitch. At high/course (cruise) pitch, the inboard portion of the blade can have zero (unproductive) or even negative (counterproductive) AOA. The "magnum" prop is aleged to reduce this effect, but it's still there even if it is less prominent.

 

At this juncture, I plan to fly my rotary Cozy with the Catto prop from hell - very wide chord and pitched from here to yonder.

 

Just a theory ... Jim S.

uhmmmm...

"...the blades are not structurally connected to each other..." in ALL adjustable/constant speed props that I'm aware of.

"This is a fundamentally shaky ("shakey" was an excellent choice of words here :) )situation..." exists for ALL adjustable/constant speed props that I'm aware of. I suspect that the fundamental problem is one of vibration/torsion resonance. Matching a prop to an engine is not a simple "bolt it on" issue. Yes, many pops ahave the resonance frequency well out side the operational range. But, for my money a dynamic balance check at all operational RPMs is a minimum requirement for prop/engine installations

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You might want to check this www.rospeller-aero.com .

This is a german manufacturer.Claimed to be for rotax and others,they got diameters up to 70`.It might work with other engines at a price about 4000$.

HM

Don't do it!

The problems is related to the bangs.

A direct drive engine is not running smooth. You have 4 explosions in 360 dgr. That is hard to deal with.....talking about carbon or glass. They try to solve it by making the prop hollow or fill it with a soft material and make it as light as posible so the inertia mass is low.

 

The rotax 9xx is not a direct drive. The 4 in 360 explosions are reduced to (lets say) 1:3 and the vibrations is reduced as well (not 1:3, but significant). That makes it suitable for carbon.

 

Wood can absorp the vibrations comming from a direct drive. Stick to wood

 

Ton.

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