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Author Topic: RotorWing!  (Read 2371 times)

Offline Dave Hull

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RotorWing!
« on: October 18, 2020, 12:57:30 AM »
Here is my updated take on Roy Clough's rotorwing plane. It takes plenty of power but is fun. A very different flying experience. It took me a couple of tries to get the line rake correct, and to loosen up the rotor bearing to account for flex in the wing spar--which is simply a piece of piano wire. If one wing binds up and the other does not, well, you got yourself a rodeo there, pardner....

I intended to put some DARPA graphics on it, but never got around to it. But it looked good that way on my sketchpad....

It is more fun if there is a slight breeze. Going upwind, you can crank in a bunch of UP and the plane slows down because it really isn't generating enough lift to get much higher than level. So the drag goes up even further and it starts to hover. It is partly hanging on the prop. It does not do well in stronger winds simply because it is so slow there is little line tension.

There are a couple of things to remember when flying it. First, it's going to have to taxi a good ways to get airborne. Whipping just loads up the spar and may induce sufficient bending to lock a blade, whereupon the thing rolls over into the pavement. (My flying "buddies" thought that was the single funniest #$%&! thing they had ever seen at the field....)  Second, when the engine quits, it drops out of the sky nearly vertically. There is not much inertia in the rotors, and it does not have an autorotation characteristic.

Most people who see it find it oddly interesting. And it does have a certain whirring sound....

The Divot


Rotor span:    26"
Rotor chord:   3-3/4"
« Last Edit: October 18, 2020, 01:36:45 AM by Dave Hull »

Offline Dave Hull

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Re: RotorWing!
« Reply #1 on: October 18, 2020, 01:11:40 AM »
Here is a different view showing the slotted rotors. They are made of 1/16" balsa sheet with basswood endplates. I glued a bronze bushing into each endplate. Intially the fit was good for a rigid running fit--but it locked up when the spar flexed. I ovaled the bushing (similar to what is done in a timepiece bearing) and opened up the fit as well. No issues since then.

I balanced the rotors to within the bearing friction, so it is fairly smooth in flight. I suspect that small aerodynamic asymmetries cause as much vibration as the static unbalance. But that's just a guess.

The rotors do not generate a great deal of lift. Most of the engine thrust goes toward creating lots of thrashing. Think of this as a kind of airborne threshing machine....

The original plans said to use very hard balsa for the fuselage. That's a story in itself. Let's just say I located such a piece and used it, expecting that the thing must vibrate a ton or otherwise want to self-destruct. It doesn't. And, it would be a better flyer if it was lighter, for sure.

Offline Dave Hull

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Re: RotorWing!
« Reply #2 on: October 18, 2020, 01:23:41 AM »
I found it perplexing that there was no balance point shown on the thumbnail plans from the old magazine. So I thought about it for a bit. My conclusion was that it had to balance on the spar, since the lift and drag vectors had to go thru the rotor shaft, or else the tail would be required to do a bunch of lifting to establish the fuselage flight angle. To achieve this balance point having used petrified balsa for the fuselage, I needed to move the engine forward. I made a long spacer and trimmed it to get where it needed to be.

With this trim setup, the plane will fly level, with no "squatting at the tail." That is really helpful when the engine quits as it has less tendencies to fall out of the sky backwards onto the tail.

Offline kenneth cook

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Re: RotorWing!
« Reply #3 on: October 18, 2020, 06:04:02 AM »
             Dave, that's very cool. I love Roy's designs. I've always taken a liking to them.

Offline Dave Hull

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Re: RotorWing!
« Reply #4 on: October 18, 2020, 03:13:41 PM »
Ken,

Have you tried any of them yet?  It is fun because they are so different. Just don't expect the local "stunt mafia" to show much interest. I'm looking at the drawings for the Venusian Scout next....

The Divot

Offline john e. holliday

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Re: RotorWing!
« Reply #5 on: October 18, 2020, 09:34:35 PM »
Yes he did have some unique designs that were fun to play with. D>K
John E. "DOC" Holliday
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Shawnee, KANSAS  66203
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Offline kenneth cook

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Re: RotorWing!
« Reply #6 on: October 19, 2020, 02:54:38 PM »
           One design in particular was his "Stunt Goat" it was a stunter for a TD .09. You just don't see too many offerings for that engine and I built it. I believe it was featured in Flying Models. I didn't care for the look of the rudder but I stayed true and built it that way. I also have the Cloud Copter which hasn't been flown yet.

Offline Dave Hull

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Re: RotorWing!
« Reply #7 on: October 20, 2020, 06:07:22 PM »
Hmmm. How does the "goat" fly?

I was looking at the Venusian plans today. Gotta find me a better paper plate.

The Divot

Offline Howard Rush

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Re: RotorWing!
« Reply #8 on: October 28, 2020, 01:22:43 PM »
That's really cool.
The Jive Combat Team
Making combat and stunt great again

Offline Chancey Chorney

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Re: RotorWing!
« Reply #9 on: October 28, 2020, 08:25:40 PM »
Well, isn't that the neatest thing I have seen in quite a while.

Offline Dave Hull

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Re: RotorWing!
« Reply #10 on: October 30, 2020, 02:52:25 AM »
Here's an in-flight photo from last year with my friend Ron Duly at the controls. You can tell it's a pretty casual plane to fly--as long as you have line tension.

Notice that the rotor panels are completely independent and are not synch'ed up in any way. I think as long as the rpm is high enough, any roll wobble is mostly damped out.

The Divot

Offline Norm Furutani

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Re: RotorWing!
« Reply #11 on: October 30, 2020, 02:19:01 PM »
Dave
You need to build a Clough Little Dragon to power it! See: http://modelenginenews.org/design/design6.html

Norm

Offline Dave Hull

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Re: RotorWing!
« Reply #12 on: November 01, 2020, 12:53:25 PM »
Norm,

Like this one?

The Divot McSlow

Offline Norm Furutani

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Re: RotorWing!
« Reply #13 on: November 09, 2020, 04:56:31 PM »
Yes! Yours is further along than mine!

Norm


Offline Dave Hull

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Re: RotorWing!
« Reply #14 on: November 10, 2020, 10:08:06 PM »
My rendition of the Dragon ought to be farther along---I started it when I was in High School!

Got it out this past year to see about making some progress. Bought material for the sleeve from McMaster. Found that the Unimat I borrowed wasn't stiff enough to cut steel, even with really light cuts....so, I put the pieces back in the box.

I did make the backplate, though, so that is at least some progress. I turned the whole thing with a large flange so I could rear-mount the engine. Then filed the flange so it was just two ears. I think that will work good. It is bottom tapped for the TeeDee venturi and on the inside mimics the Cox reed setup. Will probably have to sleeve the venturi, but still seemed the easy way to go.

I could also install the brass bushing in the case. I have one turned but it's a slip fit and will have to bond it in. And could trim down the rod. I like the way you have yours shaped. I way thinking of bushing mine before I trim it down. There isn't much there to hold on to....

Fun stuff,

Dave

Offline Serge_Krauss

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Re: RotorWing!
« Reply #15 on: November 25, 2020, 10:33:04 AM »
Great little project and I'm sure lots of fun to solve those problems.

I love Roy Clough designs! He also designed a centrifugal "pressure jet" model that used a centrifugal blower mounted horizontally (vertical axis) to draw in air from above and expel it from the rear. I've always kept that one in mind.

Here is my current project, his FF slotted saucer that used an Infant Torpedo, but flew well for me, as a kid, with a Cox .020. I thought I'd build another this year, but discovered that several things that I did back then are impossible - Ha! At the moment, I have to clean up the mess I made of the 1/32" nose sheeting. I know I used 1/16" as a kid. I added some things and redesigned the fin. Anyway, my original flew well, hooked a thermal around 1963 and flew away.

SK

Offline Dave Hull

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Re: RotorWing!
« Reply #16 on: November 27, 2020, 12:48:59 AM »
Serge,

What did he call the centrifugal design you referred to?  Any idea what magazine and date? Would love to see it as I don't recall that one at all....

Sounds in some ways similar to the Avro Canadian design?

Hard to believe your basic slotted manhole cover could fly out of sight, but there are always magical possibilities when flying is involved. Hope you get your planking spiffed up and the plane ready to test.

Fun stuff!

Dave

Offline Serge_Krauss

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Re: RotorWing!
« Reply #17 on: November 27, 2020, 08:33:34 AM »
Hi, Dave -

I think I saw the centrifugal blower plane in one of those magazines with reprints of old articles. I never throw anything like that away; so it's around here somewhere. I'll look for it and get back to you. Due to my new dry-eye condition and blurriness, I did a real number on the 1/32" sheeting of the slotted saucer with my CA. That will be an interesting solution to find! I don't think I'll use 1/32" stuff for that purpose again.

Edit: I have looked through all of my archived magazines and have not found any of the three or four in which that article was reprinted. I'm mystified. But if I remember something more or run across the article, I'll post it. 'sorry!
« Last Edit: November 27, 2020, 10:02:14 AM by Serge_Krauss »

Offline Serge_Krauss

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Re: RotorWing!
« Reply #18 on: November 27, 2020, 10:30:19 AM »
Dave-

I I've found it! This was on an internet forum: "Blow Bug" plan. It's in the last post on this page:

https://www.rcgroups.com/forums/showthread.php?918046-Roy-Clough-jr-files

p.2 has some follow-up discussion and a video of an RC flight of the slotted saucer.

This is the direct link to the "Blow Bug" plan, but it won't open on Stunthangar for me:

 file:///C:/Documents%20and%20Settings/Joe/My%20Documents/Downloads/Blow%20Bug%201017.pdf

file:///C:/Documents%20and%20Settings/Joe/My%20Documents/Downloads/Blow-Bug.pdf

(This last one works for me when copied into a Word document, but not here).


SK
« Last Edit: November 27, 2020, 11:32:32 AM by Serge_Krauss »

Offline Dave Hull

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Re: RotorWing!
« Reply #19 on: November 29, 2020, 06:07:56 PM »
Serge,

Now that's pretty cool! I think I could improve the ducting, though. I might try to make an impeller and see if it's worth it to build a plane. Converted to control line, of course....

The Divot

Offline Serge_Krauss

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Re: RotorWing!
« Reply #20 on: November 29, 2020, 07:21:12 PM »
Exactly what I thought, Dave. I think he called this a "pressure jet" and just relied on raising internal pressure. I'd like to know how and electric version with twin ducting (top and bottom impellers) would work. After I saw that one, I found a couple texts on fluid dynamics application and pumps, but there was too much life in the way. Anyway, the ducting could be three levels: top and bottom for thrust, and middle for cooling and whatever thrust could be gotten from the heated flow.

Offline Dave Hull

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Re: RotorWing!
« Reply #21 on: November 29, 2020, 11:03:10 PM »
Hmmm. Not sure I follow your description. How would you feed the middle duct?

I was thinking along the lines of installing flow straightening vanes (stators) on the output side of the blower wheel. And close off all the forward radial flow directions since causing reverse flow in such a tiny plenum can't be optimal. Then add a radius inside the plenum right below the impeller. That would close off the engine bay, so you'd need a dedicated inlet and exhaust just for cooling. I'd try to keep that separate from the propulsion flow.

You might even be better off by restricting the inlet diameter to a central portion of the wheel. That would help organize the flow in the radial direction. I might try biasing the inlet toward the front of the spin axis. (Oops. On further review of the plans that is exactly what he did by using his diaphragm plate? He restricted the inlet to a center core. No bias though.)

It's all good to talk about operating off of pressure and using a plenum, but let's face it, flow losses will kill you. Ninety degree box corners will kill you. Flow that is counter to the desired exhaust direction will kill you.

In a way, this reminds me of the earliest jet engines. I believe it was the Brits that had a radial flow design. Might have been easier to conceive/analyze/build, but it was a dead end performance wise. Axial flow rules the day. So in that line of thought, this whole deal would be more practical using a canted engine axis and an axial flow blade set. In other words, another ducted fan. But it might be more fun playing with something more akin to an aerial steam engine....

Dave

Offline Serge_Krauss

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Re: RotorWing!
« Reply #22 on: December 01, 2020, 08:42:50 PM »
It's all for fun - no advantages I can see. I just see it as a couple centrifugal superchargers, top and bottom, and a dedicated cooling flow. Regardless, Roy surely didn't intend to optimise his plane, but just to have fun proving a basic point.  He pressurized the entire fuselage (plenum) and let the air escape rearward. Contouring could do a lot to decrease drag on the exiting gases, thus increasing thrust. I saw some reference to his pressure jets. I wonder whether that means he built others.

Offline Chuck_Smith

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Re: RotorWing!
« Reply #23 on: December 02, 2020, 05:41:35 AM »

<Snip>

In a way, this reminds me of the earliest jet engines. I believe it was the Brits that had a radial flow design. Might have been easier to conceive/analyze/build, but it was a dead end performance wise. Axial flow rules the day. So in that line of thought, this whole deal would be more practical using a canted engine axis and an axial flow blade set. In other words, another ducted fan. But it might be more fun playing with something more akin to an aerial steam engine....

Dave

Dave, there are plenty of "jets" flying today with radial flow. Honeywell engines have radial turbines. Take a look a the ATF3 engine. I put "jets" in quotes as in reality, there are fewer and fewer civilian actual tubojets left, almost all modern civilian engines are turbofans with high bypass ratios these days. About the only place you'll find actual jet engines anymore is military or smaller bizjets.

Chuck
AMA 76478

Offline Dan Berry

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Re: RotorWing!
« Reply #24 on: December 02, 2020, 06:43:48 PM »
Serge,

What did he call the centrifugal design you referred to?  Any idea what magazine and date? Would love to see it as I don't recall that one at all....

Sounds in some ways similar to the Avro Canadian design?

Hard to believe your basic slotted manhole cover could fly out of sight, but there are always magical possibilities when flying is involved. Hope you get your planking spiffed up and the plane ready to test.

Fun stuff!

Dave

I'm pretty sure it was Blow Bug.


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