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Author Topic: CATAJETS: Design and Development  (Read 62797 times)
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Starduster
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« Reply #700 on: May 10, 2019, 09:34:11 AM »

OK, you guys are just having WAY too much fun without me, so I thought I'd throw my hat in the ring and try my first Catajet.

As the XB-70 has always been one of my favorite airplanes, this is as good as place to start as any.

I had already done a laser kit (offered by Bob Holman Plans) for the Competition Models B-70, I simply scaled the CAD down 50% to get a B-70 with a 10.375 inch wing span. There are a couple modifications, one being the rudders now have tabs that fit into slots in the wing, and the curvature of the bottom of the rudder follows the curvature of the wing.

A couple pictures are shown of the airplane before paint. I'm going to give it a light coat of white.

This being my first Catajet, I am not sure where to place the rubber hook, but I was thinking a little forward is best so that the airplane does not pitch up at launch. I put the paper-clip hook under the canard. It's epoxied with fiberglass reinforcement, so I'm hoping it will take the stress.

The airplane, before paint and decals weighs 18.6g. Probably heavy by most standards, but I'm not looking to win any contests, just getting in on the fun!

I'm submitting the 3-sheet drawing to the plans gallery, so if you need a quick project, have at it, and please let me know how yours flies. The uploaded file will also have a decal sheet.

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MKelly
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« Reply #701 on: May 10, 2019, 09:45:21 AM »

Very cool - I'll be looking for that plan to hit the gallery.  I was quite surprised how well the delta-winged Bill Dean Skyray flew as a jetcat once the reflex was taken out of the trailing edge.  Flyace1946 has one that also flies well.  I built a roughly 6" span XB-70 glider while in school, but it was much too heavy for its size and glided about like the space shuttle.  Yours looks very good, and isn't really all that heavy.  For comparison my 11" span Skyray weighs just short of 19 grams and will do 20-30 seconds if I get the launch right.

Tony, the F-16 flight videos look great - quite a nice glide on that one.

Mike
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Starduster
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« Reply #702 on: May 10, 2019, 02:17:51 PM »

"There she is, all bridled and saddled..."

Just about ready for first flight.
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FLYACE1946
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« Reply #703 on: May 10, 2019, 02:24:08 PM »

Looks Great. Have fun ok? Make some in flight videos if possible.
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tross
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« Reply #704 on: May 11, 2019, 10:02:35 PM »

That's just perfect Rich and thanks for the plan. Smiley
I really like the finished look. Waterslide decals?

Regarding the F16 development,
I've raised the flaps a small amount.
This in turn has flattened out the glide angle and slightly reduced drag as expected.
A more coordinated turn during climb out, and a smooth transition. Cool

A cool day for flying (55°F/13°C) with a light 3-5 mph breeze.

https://youtu.be/CpHppg13CQ4


T
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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"........
Starduster
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« Reply #705 on: May 13, 2019, 10:45:35 AM »

That's just perfect Rich and thanks for the plan. Smiley
I really like the finished look. Waterslide decals?


You are welcome, pleased to share with this community. I have not had a chance to test fly my XB-70 as yet.

I went to my local FEDEX Office store and got the drawing and decal sheet printed on 8 1/2 X 11 clear "sticky back" (label sheet). I then simply peel and stick the parts onto the balsa sheets and cut right through the plastic. The decals are also just cut out and peel and stick.
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hkybob
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« Reply #706 on: July 01, 2019, 10:23:47 PM »

I'm gonna build this little 7" Skyhawk for my son, plans show a flat wing, any benefit from trying to give it a airfoil ?
Thanks
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OZPAF
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« Reply #707 on: July 03, 2019, 08:39:45 PM »

Quote
any benefit from trying to give it a airfoil ?
It will help a little and also reduce the weight slightly. However it may be best to leave it flat for strength.

John
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MKelly
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« Reply #708 on: September 08, 2019, 06:01:56 PM »

Jetcats are still distracting me from other models (one of these days I've got to finish that Sopwith 1-1/2 Strutter).  Here's a pair of F-111B jetcats built for the carrier launch Jetcat event at next month's WestFAC meet in Phoenix AZ.  For this event we'll launch jetcats flat and level off a carrier deck (picnic table equipped with a standard 9" loop of 1/4" rubber on a 3' string as the catapult).  The unique thing with this event is the dead-flat launch, which means trimming a bit different than typical jetcats.

The models are adapted from the West Wings/Estes F-111 catapult glider kit.  The swept-wing bird (marked as the Phoenix missile test aircraft) is built from the kit, 12" span with the nose trimmed to F-111B shape, a 1/64" doubler inserted in the forward fuselage and a fin cut from lighter wood.  The approach-configured bird (marked as the carrier trials aircraft) is 14" span, built using kit parts as templates but cut from lighter wood and with the wing unswept with flaps and slats depicted as deployed to get a bit more wing area.  Both have airfoil and washout sanded into the wings and all surfaces thinned out and smoothed as much as seemed prudent.  The kit had panel lines printed on the wood, so I drew them back on after sanding and before painting the models.  Paint is airbrushed on thin enough for the panel lines to show when holding the model.  Markings were printed on a scrap of esaki, doped, then glue-sticked to the models.

The swept-wing bird is a brick at 23g (I think they got their balsa from Guillows' reject pile), however, it launches beautifully with a wide climbing right turn, gradually rolls level at the top, then glides straight and fast in whatever direction it rolled out at.  Best flights have been just over 20 seconds, but it covers a lot of ground - had to climb a fence for retrieval after it flew off the field.  Video at:  https://youtu.be/p0MGONvVbDc

The approach-configured bird is lighter at just under 17g.  I borrowed the flap bending approach Tony Ross used on his excellent F-16 jetcat to increase camber and washout on the wing.  Just finished it this morning so flights have been limited to test glides in the yard.  It floats along quite nicely, much slower than the swept-wing version.  Hope to get some launches on it in the coming week.

This'll be fun...
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FLYACE1946
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« Reply #709 on: September 08, 2019, 08:09:31 PM »

Looks like a fun project. Great flights are always welcome. Great choice for the deck launch event. Already flying great.
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OZPAF
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« Reply #710 on: September 09, 2019, 02:54:33 AM »

Carrier launched Catjets.Thats innovative Mike. do you have a herd of elves working for you by any chance? Fun incorporated.

John
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MKelly
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« Reply #711 on: September 09, 2019, 09:16:21 AM »

Carrier launched Catjets.Thats innovative Mike. do you have a herd of elves working for you by any chance? Fun incorporated.

John

I didn't come up with it, I'm just a willing victim enthusiastic participant!  Tom Arnold and the WestFAC steering group chose the carrier aviation theme for this year's meet and (inspired by some interesting videos out of Japan) came up with several deck-launch events.  It promises to be entertaining...

Cheers,

Mike
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OZPAF
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« Reply #712 on: September 12, 2019, 07:39:33 AM »

Don't forget the crash helmets and the fire extinguishers Smiley

John
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MKelly
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« Reply #713 on: September 13, 2019, 05:30:19 PM »

I think I should have gone for a bit more stiffness in the wings on the approach-configured F-111B - see sequence of frames grabbed from 120fps video...

Mike
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flyfac
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« Reply #714 on: September 13, 2019, 07:17:15 PM »

Ornithopter CLG!

Best,

Scot Dobberfuhl
Forest Grove, OR
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FLYACE1946
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« Reply #715 on: September 13, 2019, 07:52:15 PM »

Mike we had fun while it lasted. The launches were just  very nice, We should have a lot of fun next Saturday,
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OZPAF
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« Reply #716 on: September 14, 2019, 06:41:18 AM »

A couple of strands of carbon on top and bottom will fix that. That is good balsa - lots of flex and it didn't break.

John
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MKelly
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« Reply #717 on: September 15, 2019, 09:29:42 PM »

A couple of strands of carbon on top and bottom will fix that. That is good balsa - lots of flex and it didn't break.

John

Actually, while the wing panels stayed intact through the flutter the top sheet on the fuselage didn't  - see first deck launch in the video here:

https://www.youtube.com/watch?v=JQcNM345AwM

As shown in the video, a strip of carbon fiber epoxied to the underside of the (reassembled) wings cured it all.

Cheers,

Mike
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Walt
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« Reply #718 on: September 15, 2019, 11:30:56 PM »

Neat stuff there Mike, I enjoyed the video.
Wally
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OZPAF
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« Reply #719 on: September 16, 2019, 05:15:36 AM »

You must have been using the afterburner Mike. Smiley Thanks for the video.

John
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FLYACE1946
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« Reply #720 on: September 17, 2019, 11:44:04 PM »

Mike I can't get the F-111 out of my head. Just gotta do the thing.
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