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Author Topic: CATAJETS: Design and Development  (Read 57171 times)
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MKelly
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« Reply #650 on: July 03, 2018, 04:57:16 PM »

At 16g your Schwalbe should fly quite nicely!  Mine weighs about 25g.  To give credit where it's due, the short kit I built from was designed by Henry Toews and "productionized" for laser cutting by IronMike.  I fiddled with the wing rib configuration and beefed up the nacelles (thus the somewhat portly flying weight).

Look forward to your flight reports Paul.

Mike
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tross
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« Reply #651 on: July 05, 2018, 01:19:53 PM »

It looks like a flier Maxout, the stab doesn't look big.
Glad to hear you have a laser cutter now, it will no doubt speed things up. Smiley

That's a nice looking cat jet Paul, they should give you plenty of extra points. Cheesy
Your wing design is just standard stick and tissue?
Very cool.

Hi John yes. I fly them straight at the trees until they get bored and give up. Cool

The first few iterations of the SR-71 flew fine as long as there was a breeze.
Trimming in calm conditions highlighted it's inability to self correct in pitch.
I made a couple of voodoo modifications, but was just putting off the inevitable.

The new model is bigger, and with an 8" span it's nearly 16" long. Shocked Shocked
There's a slight rise in elevation or climb out at high speed.
The transition is smooth and the glide is very stable.
It's a slower glide now for obvious reasons (see pic).
But as the nose lowers the on-coming wind encounters the smaller outboard elevons and we see a nose up correction.
If the nose starts to rise in the glide and then starts to slow, the on-coming wind is deflected by the larger inboard elevons.
The degree of launch bunt/loop is a balance of the four elevons as a whole.
The outboard elevons control the roll at high speed effectively, and can turn the model in the glide with a neutral rudder.
Tilting the model over at launch with a half pull of 1/8" rubber, the model rolls out at 40 ft. and heads straight for the corn.
Turning in the glide eats duration as expected.
Very little ballast is required.
Weight for this larger version is 6.8 grams.
The weather looks nice for the weekend, so I may stop down at the school to let it loose. Grin

Tony
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Instructions: Step One...Assemble the pile of sticks shown in pic "A" to look like the model airplane shown in pic "B"........
MKelly
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« Reply #652 on: July 05, 2018, 01:36:29 PM »

Very cool Tony.  If you get a chance to stretch it out at the schoolyard please take video!

Mike
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tross
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« Reply #653 on: July 05, 2018, 10:37:15 PM »

Hi Mike thanks.
Of course. Always taking some video if possible. Grin
I'm still a little hesitant to let it rip completely.
Just trying to stay out of the corn. Roll Eyes

https://youtu.be/Zvn4mSZfPlI

Tony
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tross
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« Reply #654 on: July 07, 2018, 04:10:41 PM »

Those flights are hard to see. Tongue
Here are a couple low launch flights that circle back around (which is nice, less walking). Smiley
This set up would probably work well enough for any type of SR-71 free flight model. Cool

https://youtu.be/-jHW3hKCz9w

May I ask what type of airbrush paint you guys/gals are using for these?
I have a couple of options but would appreciate suggestions.

The slow trim is a little strange for a jet, so I set everything back to zero and trimmed minimums for a faster glide.
It climbs higher and flies faster but the duration is about the same.

https://youtu.be/eWKIFRWDiFs

Cat Jet fliers might get a kick out of this next video.... Grin Smiley Cheesy Grin

https://youtu.be/5DLD8rtTKTM


Tony
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LASTWOODSMAN
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« Reply #655 on: July 07, 2018, 04:48:54 PM »

Great videos Tony !    Shocked Shocked   I really enjoyed them.    Now I know what a lawn dart is, in the truest sense of the word .... that SR-71 Blackbird catajet not only finishes like a lawn dart, it actually looks like a "lawn dart" going in.   Smiley

LASTWOODSMAN
Richard
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OH, I HAVE SLIPPED THE SURLY BONDS OF EARTH ... UP, UP THE LONG DELIRIOUS BURNING BLUE ... SUNWARD I'VE CLIMBED AND JOINED THE TUMBLING MIRTH OF SUN-SPLIT CLOUDS ...
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« Reply #656 on: July 08, 2018, 12:39:42 AM »

Fancy treating your $ 1 to the power of - billion balsa SR71 like that Tony. Grin lots of fun for very little money except time.

What would Kelly Johnson say? Cheesy Cheaper than wind tunnel testing.

Thanks for your vids

John
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tross
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« Reply #657 on: July 09, 2018, 08:27:38 AM »

Thanks Richard. Much appreciated. Smiley
I think the next time it darts in I'll just leave it there.
It would make a fitting snow gauge for an aero modeler. Grin Smiley Cheesy Grin

Kelly Johnson would say I'm a nut job John. Roll Eyes
SR-71 and glider in the same sentence just sounds weird.
It's only been about a week and I've found it to be surprising easy to fly.
I made a design change that added 5 seconds (30%) to the average duration.
More of a left turn roll out, less of a loop.

The third launch is the highest.  Shocked
I put an evening calm wind launch in there for the record.
Spent some time on the roof, in the trees, and out in the corn but it was a good day of flying. Grin Grin Grin

https://youtu.be/QD89062aPQE

Tony
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Instructions: Step One...Assemble the pile of sticks shown in pic "A" to look like the model airplane shown in pic "B"........
Bigbandito
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« Reply #658 on: July 09, 2018, 02:15:03 PM »

Beautiful plane and great flights. I wouldn’t have thought it possible. Thanks for sharing.


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"If you love something, set it free...  Just make sure you've got a DT on it."  - Richard Bach (paraphrased)
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« Reply #659 on: July 09, 2018, 08:34:02 PM »

Well done Tony.

John
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MKelly
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« Reply #660 on: July 09, 2018, 09:00:44 PM »

Very cool Tony, what's next?  XB-70, maybe an Ekranoplan?

You're making me want to do another jetcat.


Mike
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tross
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« Reply #661 on: July 10, 2018, 12:48:53 PM »

Absolutely Mike, you should build another one. Smiley
The Valkyrie would be a neat trick.
Although I'm on the fence a little about dealing with a canard, it might be a plus.

Thanks for the reply Bigbandito. Much appreciated. Smiley
These little planes are something else. Crazy fun. Cheesy

As well for you John. Smiley I see now why this is a thing.
I lost it in the corn last night but it was near retirement.
Part of the deal.

Tony
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Instructions: Step One...Assemble the pile of sticks shown in pic "A" to look like the model airplane shown in pic "B"........
Maxout
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« Reply #662 on: July 11, 2018, 11:29:19 AM »

It looks like a flier Maxout, the stab doesn't look big.
Glad to hear you have a laser cutter now, it will no doubt speed things up. Smiley

It's turned into a consistent flier. Flights are mostly in the mid 30's when I'm not doing stupid stuff. Even then it usually pops into a nice glide at thermal catching altitude (I normally fly in the evenings so those are rare).
https://www.youtube.com/watch?v=XlxRz9kRsmU&t=2s

I'm enjoying your SR-71 efforts. Would love to make a kit of that bird but Lockheed is really nasty about requiring licensure of these things. Maybe I'll try something silly like an XB-70...
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tross
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« Reply #663 on: July 12, 2018, 12:56:46 PM »

It looks like a fun jet Maxout. Smiley
Very cool and nice paint job (what kind of paint is that BTW  Roll Eyes).

I hope you get some time to draw up, and kit, a delta.  Grin
Unfortunately, I could use a bigger yard... Cheesy

Tony
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« Reply #664 on: July 17, 2018, 12:36:13 PM »

It looks like a fun jet Maxout. Smiley
Very cool and nice paint job (what kind of paint is that BTW  Roll Eyes).

It's just the rattle can stuff. I put down a coat of clear dope and then painted it. It's not a super heavy coat of paint. The splinter type camo definitely makes the model look less simple and plain.

I hope you get some time to draw up, and kit, a delta.  Grin
Unfortunately, I could use a bigger yard... Cheesy

I might tend to do such a thing... Wink
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tross
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« Reply #665 on: July 17, 2018, 04:05:17 PM »

Thanks Josh.
So just a coat of sealer or dope, and some enamel is common for these then. Smiley
I like this one next.
Pretty, isn't it? Grin

Tony
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MKelly
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« Reply #666 on: July 17, 2018, 04:37:35 PM »

You going to do it with the asymmetric wing Tony?
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tross
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« Reply #667 on: July 17, 2018, 04:45:39 PM »

With lots of pin holes..... Grin
It'll probably be this version, which I think was the original set up..

tross
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« Reply #668 on: July 29, 2018, 09:28:39 PM »

I think you might get a laugh at the "cat" in this cat jet video Peter (Pit). Smiley
Just a couple of low powered glide trim flights.
No tail, no worries... Grin Smiley Cheesy Grin

https://youtu.be/qZJY8cpxZac

Tony
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OZPAF
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« Reply #669 on: July 29, 2018, 09:38:46 PM »

The cat liked it Tony.  Smiley He didn't see it coming on the second flight - It must be stealthy Smiley

John
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MKelly
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« Reply #670 on: July 29, 2018, 10:03:21 PM »

More incredible stuff, Tony!  That looks really stable, and very cool - the split ailerons (drag rudders?) seem to be very effective.  Would you consider posting your plans in the gallery here?

I posted this over in the "What did you do airplane-wise today" thread, but thought some of the folks here might like it - got a 2+ minute thermal flight out of the Me-262 jetcat this morning:  https://www.youtube.com/watch?v=o724ae5QLyU&t=36s

Not all that much to see on the video as it drifted quite a distance from the launch point.

Cheers,

Mike
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tross
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« Reply #671 on: July 30, 2018, 08:00:58 AM »

Thanks Mike.
It launched right into one and then searched for another. Shocked Shocked
That was awesome. Smiley

I appreciate the suggestion but the plan is just a balsa wing.
Unfortunately, I wouldn't be able to express the mechanics of flying tail-free on a plan. Embarrassed
Good eye as always, drag yaw. Cool

Tony
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OZPAF
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« Reply #672 on: July 30, 2018, 08:38:26 PM »

I didn't check this out thoroughly yesterday Tony and missed the split aileron/drag rudders that Mike mentions. Very clever. I agree it does look quite stable and the drag rudders look powerful. Do get interaction between the drag rudders and the elevons on top?

Very nifty plots as well - the airfoils have a very defined low drag sweet spot. Interesting. Keep the wing loading low and stay near the sweet spot.

Using the laminations to show the cockpit detail is innovative too.

Good stuff.

John
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tross
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« Reply #673 on: July 31, 2018, 02:37:40 PM »

Hi John,
From the field notes.
The upper and lower elevons are blended equally and not effective for ailerons.
The CG is set directly on the AC, and too much drag from the drag rudders results in a behavior typical of aft CG.
Without sufficient drag the plane wanders in yaw.
Roll is sluggish but effective utilizing the mid-span elevons, and the gust attenuators need to stay along the airfoil profile.
Any elevon lowered below the airfoil profile results in unstable behavior at increased airspeeds.

You're spot on for the light wing loading.
The outer panels are utilized for pitch stabilization and don't contribute to lift. Unless it's upside down. Grin Smiley Cheesy Grin
Lift roll illustrates the situation.  Shocked
With an AUW of 6 grams, only 35 in² of the total 46 in² of wing area accounts for lift, and the result is an approximate loading of .2 gr/in².

The structural engineering department has stepped in and suggested a wing upgrade. Cool

When the sweet spot has been trimmed in it just floats along. Grin

Thanks again,

Tony
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OZPAF
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« Reply #674 on: July 31, 2018, 08:22:47 PM »

Thanks for the details Tony. The span loading chart from Lift Roll is I suppose what you would expect from a flying wing. It does empathise that the pitch stabilizing elevons should be situated at the end of the wing to ensure a reasonable CL for the main section of the wing.
A bit like an extreme Bell shaped distribution.

John
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