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Old 12-01-2005, 11:15 PM
Starship 1 Starship 1 is offline
Corvair/Q2 builder
 
Join Date: Dec 2005
Location: Carson New Mexico
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Default Multi Blade Composite Props on Canard Pusher aircraft

Had to sign up and jump here on the Forum. On Starship (NC1 and 2) we installed 5 blade Composite set of props. These were Aramid (Kevlar) and before NC2 could get around the patch at Beech field BOTH props lent a new meaning to "feathering". We almost lost the plane over Greenwich Road!! And it almost took the roof off the car dealership on the South end of the field (Beech field is over a mile long and elevation is at or near 1000 ft, and it was not in hot temps).
You won't hear that from the PR folks at Raytheon; but its a fact because your's truly was there on the ramp when the engines were shut down and the golden fibers were simply hanging like limp rags. A very mad test pilot to say the least! It was funny after the panic and we all had a good laugh but it was an expensive goof!

The question of multiple blades on the CP configuration has to do with clearance, HP to thrust yield, and durability. Those of us building our own have to be concerned with costs too...at least more so than the factories.

Long story short. The 5 blades looked very sexy..but didn't pan out nor did the aircraft perform worth a hoot. 3 blades were almost as bad...too little thrust, couldn't make them long enough and still have clearance. So 4 was the way it worked. As far as balancing.. the more blades the easier to balance. Also, the more blades the greater your engine output must be to absorb the potential of the props thrust (and mass). If you've ever heard Starship fly overhead you will know what it is because of the distinctive "rasp" and slightly higher pitch of the engine sound. all of them used 4 blades means 2 of them are moving through disturbed air at around 20 degrees of shaft rotation at all times in flight. The POC that Scaled built for Beech did not have 4 blades. It used 3 bladed units and the Pratt and Whitneys were kept at design fuel trim. Beautiful! It was the way the aircraft should have been built. The right size, the right aerodynamic systems... it all worked. But that is another topic.
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Old 12-01-2005, 11:44 PM
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Dust Dust is offline
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That is very shocking info - how did this not occur in ground testing??? didn't they do it with disturbed air in a test cell???

are you thinkin of, buildin or flyin?
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Old 12-02-2005, 09:09 PM
Starship 1 Starship 1 is offline
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No testing other than on NC2 (Non-Certificated). Harzell brought out these sexy 5 blade Kevlar jobs and the hubs. The run up didn't show or sound like any big deal other than the RPM's were now under control. Chief Test pilot (Mr. Top Gun) threw the horses to it and off they went... and rolled..and rolling..and then a really slow rotation..then more rolling....more rolling!! jeez..it's getting an awfully looooong way down the field..then eeeever so slowly the sunlight was under the mains... I swear..the aircraft couldn't have cleared Stevens Toyota roof more than 100 feet if that. It never gained more than maybe 700 ft off the field elevation. As he turned East the sound began to change.. it was a "whispy" noise is all I can thing of to describe it. Kinda like Rita what-her-names' voice on the Fox News channel.

He never made a turn to base..it was all one big arc back to the threshold. And the party began.

Keep in mind guys that all this stuff like Aramid was a new deal to us (this was in 1982 or 83). Even Carbon pre-pregs were really "spacy stuff". We didn't understand the Kevlar adhesion to it's bonding epoxy was not all that great and like I said..we didn't build the props at Beech. I don't know why the spec went out to purchase them made with Aramid (I guess bulletproof ment indistructable??). At the time I was a simple shop hammer out there getting black lung from grinding on the black funny smelling stuff that put sharp needles in your hands. Without any protection at all (we were told the dark cloud particals in the air after grinding parts were too large to hurt our lungs, so stop complaining; though one or two of the folks had their doubts! Cough cough cough).
I was also part of the Flight line team all the way up to proving the tooling which I made myself to production in Plant 3. I worked all kinds of hours because.. I WAS IN LOVE WITH THE AIRPLANE.. so ok.. I admit it.. I'm older and maybe not so foolish now (Hmmm maybe not, or why am I building a Quickie 2 with a 40 year old auto engine in it?)..

Anyway...we had no idea the "dirty air" aft of the wing would shake the Epoxy right out of the fibers. The bonding of Graphite is much better so the Carbon fiber blades work. Metal does too of course. Wood works very well as you folks building Cozy's and true Canard Pusher designs know. A pair of wood 4 bladed props on Starship is not a picture of "hi-tech" now is it? Even though it might have worked a LOT better.. It was all about Image....

Let me tell you guys something here about the factories if you didn't already know. There are PLENTY of big boo boo's made all the time over what seems later to be an obvious mistake. I know.. I see them and have to put out the fix on them all day(evening) long. There are VOLUMNS that others could tell you besides me..so don't think for one minute that "common joe" working his fanny off in the garage is a Neanderthal or something. NOT SO!! YOU are a much better risk as a builder. Why? You have more at stake, right?

You know what Beechs' (it's NOT Raytheon, Beechcraft is still on the roof, thanks anyway).. nickname is here in Wichita?

Jurrasic Park.

Know why? Because they have a lot of new techno toys and autoclaves and such but the Dinosaurs still run the place.

Many a stormy 2nd shift night I helped the poor machinists in Plant 1 cover Million dollar CNC machine centers over with plastic because the roof leaks like a sieve. They would try to continue running parts to prevent line stoppers and the machines (of course) would overheat. Then what? I had to re-write EVERY order that was on the hot or AOG sheets to the conventionals. You think they'd fix the roof, right? Nope!! Too expensive.. no budget.. NOW you know why your Bonanza parts cost what they do.

Ever stop to think why Beech aircraft almost always have doo-dad's all over the flying surfaces (including Starship)? How many companies would buy a (junk in my opinion) competing design (DH125 and the Mitsubishi for example), rename them (Hawker and Diamond), THEN plunk down a Billion bucks or more on something that was already being built better across town (Premier 1 and Horizon/ Citation)? Why not bring the Starship back, do it right this time, and with TURBINES on it? Olive Ann is no longer calling the shots..she's not around to say "no jets on my field" like she did back in 83..

As far as Props go I doubt Beech would have the skill set to do it right, at the corporate level anyway. There are very talented people there..don't get me wrong..but they are smothered in an ancient caste system..and it's a pity.
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