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Author Topic: CATAJETS: Design and Development  (Read 68623 times)
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MKelly
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« Reply #725 on: October 01, 2019, 09:54:04 AM »


The tissue is printed gray to blend in correct? (except for the white areas)


Tony, I printed the markings on scrap white Esaki with a faint gray background - once you dope the Esaki it turns almost clear so the background printing didn't really make much difference.  As usual I colored the back of the white areas with a white Prismacolor pencil.

Crabby, the spins make me chuckle every time (even when its an official flight).  That's been the weakness of the F-111s - if you slow them down too much at the top of the launch they'll spin just about every time, makes it tough to come off the launch right into the glide.  I usually lose around 1/4 to 1/3 of the launch height before the model settles into the glide.

Mike
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tom arnold
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« Reply #726 on: October 01, 2019, 03:04:35 PM »

I might add to the discussion that if you fly a jet cat in FAC competition, the curved sheet wing will probably be a disqualification. Dropped leading edge slats and  dropped flaps would be acceptable but a cambered wing (unless the original plane had it) would be a killer in front of the judges. For fun flying, of course, it is a non-issue and the F-16 certainly shows the efficiency of that cambered wing.
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MKelly
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« Reply #727 on: October 01, 2019, 03:48:03 PM »

I might add to the discussion that if you fly a jet cat in FAC competition, the curved sheet wing will probably be a disqualification. Dropped leading edge slats and  dropped flaps would be acceptable but a cambered wing (unless the original plane had it) would be a killer in front of the judges.

Tom, you made me go back and read the rulebook (yes, Air Force types mostly can read).  The prohibition on undercambered airfoils appears in section III for FAC Scale.  I didn't see anything about it in section II (primary rules) or section VIII.4 (jetcat).  Seems like I've seen jetcat plans with arched wing slots - are you sure the undercamber prohibition applies for jetcat?

Look forward to seeing you in two weeks!

Cheers,

Mike
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tom arnold
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« Reply #728 on: October 02, 2019, 12:01:40 AM »

Mike, you make a good point and I will pursue this with the FAC honchos and get back to you on this forum in case there are any more WESTFAC attendees with that question.
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Indoorflyer
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« Reply #729 on: October 02, 2019, 09:03:52 AM »

Asking on the FAC FB group would be the quickest way to get the "official" answer/clarification. A few "honchos" hang out there. There have been similar cases where the rulebook didn't address an issue/question specifically, but "everyone" seemed to say the answer was "understood."
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mescal1
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« Reply #730 on: October 02, 2019, 12:52:40 PM »

I'd have to agree with Mike.  I'm pretty sure that rubber powered scale doesn't include catjets.  I'd still make sure with Dave M. just to be safe but
I don't see much of an advantage with undercamber in a catapult glider.  Would make it much harder to trim!
Mike
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tom arnold
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« Reply #731 on: October 02, 2019, 03:55:37 PM »

Hello Gents,
I have received word straight from the CINC of the Flying Aces that there is no, repeat no, prohibition on cambered wings for the Jet Cat event. Welcome news and it will be fun to see the battle between the two types of airfoils as they both have their strong and weak points. See you all at WESTFAC!
Tom
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Indoorflyer
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« Reply #732 on: October 02, 2019, 06:10:41 PM »

The FAC needs an English major with a law degree to rewrite the rulebook!  Grin
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FLYACE1946
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« Reply #733 on: October 05, 2019, 07:08:39 PM »

Hello Gents,
I have received word straight from the CINC of the Flying Aces that there is no, repeat no, prohibition on cambered wings for the Jet Cat event. Welcome news and it will be fun to see the battle between the two types of airfoils as they both have their strong and weak points. See you all at WESTFAC!
Tom
Thanks Tom for the ruling. Sure glad that happened.
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Bredehoft
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« Reply #734 on: October 12, 2019, 08:15:29 AM »

My latest - a smaller - 8.5" span - F-4.  No room to give it full power around here.  But I'll get it tested in a couple weeks, I think.

https://volareproducts.com/wordpress/wp-content/uploads/F470percent06.jpg

You can see a few more photos on my Blog: https://volareproducts.com/blog/?p=3910/

--george
CATAJETS: Design and Development
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OZPAF
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« Reply #735 on: October 14, 2019, 12:48:05 AM »

Interesting - it should have a good chance of flying well with the poly on the wings. looks neat.

John
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tross
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« Reply #736 on: January 25, 2020, 10:25:51 AM »

I like that one George.
Looks like a great little flier.

The wind hasn't let up much here.
Searching around last fall for a new subject I was inspired by this video.
https://www.youtube.com/watch?v=aAHOM_MZZBw.
Here are a few of the initial test flights.
https://youtu.be/4eaE96Af8yI
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"........
tross
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« Reply #737 on: February 15, 2020, 07:40:21 PM »

The designed AUW for the De Havilland Vampire Cat-jet was 13.5 grams with paint and or covering.
It's been flying naked for a couple weeks at 10.5 grams to flush out any issues with fly-ability or structure.
Proving it can survive a full power launch, bounce off the driveway nose first, and get hung up in a tree, etc.
Once there was some assurance it wasn't going to burst into jet confetti all over the yard it was sent to the paint shop. Cheesy

2 coats of sealer and a little thick on the paint resulted in 14.4 grams balanced for flight.
This is a work in progress. Roll Eyes

The flight report.
Friday was a chilly day, 17°F/-8°C with a slight wind chill of 5-8 mph.
The sun finally made an appearance which is always welcome, and the air was pretty good.

A few light powered trim flights in the yard and then out into the muddy field to have a look.
The average decent flights were in the 35-45 second range.
It's obvious from the video more practice is needed to see if we can smooth out the transition.

The last transition in this video hit home and one could only hope the camera was on and rolling. Grin
Enjoy.

https://youtu.be/2vN507VfygA

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 #738 on: February 15, 2020, 08:56:44 PM »

That Vampire really goes Tony - the glide is just about unbelievable.  Allen and I had the F-16s out flying today, still doing well.

Mike
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DHnut
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« Reply #739 on: February 16, 2020, 03:31:36 AM »

Tony,
       That was most impressive. I have a vampirenezzer and it shows the same sort of glide behaviour and has a very good stall recovery when it is flown with too much power. A Banks Mills .4 cc  engine is used. I am very tempted to build one. Is there anything I should be aware of.
Ricky
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tross
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« Reply #740 on: February 17, 2020, 11:27:58 AM »

Thanks for that Mike.
Unfortunately this one really goes. Tongue
I'm glad the little beast is still flying. Grin

Out again for some test flights this time on Sunday.
We had multiple flights over 60 seconds and it's obvious now the field is too small.

The transition is looking better as a whole.
https://youtu.be/vBMfKWB7nsU

Sometimes it would just be nice if it would stall and come down.
https://youtu.be/xLm6j65ZNb8

In the evening with the sun low it's a 30 second glider.
The repairs are done, paint touched up, and it's back on the shelf waiting for summer, moving on.

Thanks Ricky, your model sounds awesome. I'm sure it's a hoot. Smiley
You mentioned an interest in building a catapult jet.
I can't think of anything that wouldn't be obvious I guess.
Build light, 1st generation jets fly better, um, build light... Grin Smiley 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"........
FLYACE1946
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« Reply #741 on: February 17, 2020, 02:05:37 PM »

 You sure have the right touch when it comes to design, build, and FLY. Wow that Vampire is really great.
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tross
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« Reply #742 on: February 18, 2020, 06:49:48 PM »

Thanks Flyace.
I really appreciate the encouragement. Smiley
I caught a glimpse of your jet (Skyray was it?) in one of Mike's vids.
That thing is a beast. Grin

Tony
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DHnut
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« Reply #743 on: February 19, 2020, 05:31:15 AM »

Thanks Tony the posts have given me a ball park size to aim at. Many years ago I built a Viggen from a Flying Models plan that was a great performer from a mild bungee launch. I am not sure what a full blooded catapult would do.
Ricky
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tross
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« Reply #744 on: February 19, 2020, 07:27:17 AM »

Hi Ricky,
Oh right. Size. Sorry.
There are kits on line you could browse to check out.
The wingspan range for those is from around 12" to 18" mostly.
Some of the tissue covered kits that have a built-up wing are something like 15"-17".
I think last year's champ was a Miles M.100 14" (correction?) solid wing construction.
Wing (model) stiffness during a full on power launch is a limiting factor and I think we are pushing that boundary.
Carbon fiber can help tame flutter in places if it shows up.
John (OZPAF) and Mike (MKelly) were dealing with that on one of Mike's gliders.

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"........
DHnut
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« Reply #745 on: February 19, 2020, 02:57:15 PM »

Tony,
        That was most helpful especially the comment about stiffness. Flutter is a quick exit for any model. I intend to make a prefab design that can be assembled easiiy after transport as I have a grand daughter in Sweden who is keen on anything that flies and a catapult is within her capability.
Ricky 

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FLYACE1946
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« Reply #746 on: February 20, 2020, 04:48:26 PM »

Thanks Flyace.
I really appreciate the encouragement. Smiley
I caught a glimpse of your jet (Skyray was it?) in one of Mike's vids.
That thing is a beast. Grin

Tony
Tony that is the big Skyray all right. Sometimes I get lucky on the launch. That was probably the best launch of the big Skyray ever caught on film.
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tross
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« Reply #747 on: March 08, 2020, 09:31:34 PM »

I like the idea of a knocked down finished model ready for assembly Ricky.
I think others probably do that but thought I'd give it a try.
It really helped with the masking.
Thanks for that. Smiley

You should ask a friend to get it on film before it flies away Allen. Shocked
She's a beauty. Cheesy
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"........
FLYACE1946
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« Reply #748 on: March 09, 2020, 06:00:22 PM »

Well tross  Mike does try and we keep getting out to fly some. He gets to fly more frequently than I do but we may be having to look for a new location soon as it looks like construction is about to chase us off.
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tross
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« Reply #749 on: April 08, 2020, 11:50:33 AM »

The P59 glider is now complete.
Trimming it to circle in lift required a little more control input than the Vampire, and that had some effect on the launch.
Other than that the set up is similar.

There was some good air Sunday afternoon, and we captured around 40 flight clips to sift through.
The average decent flights were in the 30-40 second range, and I tried to include some of those.
As the afternoon went on the thermals started to rage a little, and we had to call it a day. Cry
The longer thermal flight clips are at the end of the video.

The last flight starts in the middle of the field, heads North,  buzzes over the trees in the side yard, circles back over the house, hits a tree in
the back yard and falls into a bush.   Shocked Shocked
Sometimes it's better to be lucky than good. Grin

I hope everyone is well. Smiley

Tony

https://youtu.be/d6Y_qqttY3o
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Re: CATAJETS: Design and Development
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