JAS 39 Gripen Park Jet

[jetset44]

Here’s the latest member of the Park Jet series, the Saab JAS 39 Gripen. This design is very similar in concept to the F-18 (http://www.rcgroups.com/forums/showthread.php?t=271581) and F-15 Park Jets (http://www.rcgroups.com/forums/showthread.php?t=289276), and uses the same construction methods and power setups. Like the other jets, it’s intended to be a park flyer built using simple construction methods and inexpensive and readily available components. It’s designed to be built almost entirely from either 6mm Depron or BlueCore foam. Here are the specs:

Wing area: 258 sq in
Span: 23.9 in
Length: 42.3 in
Weight RTF: 16.6 oz as shown unpainted (estimate 17.5 oz painted)
Wing loading: 9.8 oz/ft2
Motor: Himax 2015-4100 with 4.4 gearing
Battery: Etec 11.1V 1200 mAh Lipo
Prop: APC 9x6 SF
Current draw: 11.5 amps static
Power loading: 139 watts/lb
Radio equipment: Berg 5 receiver, GWS Pico and Hitec HS-55 servos, Phoenix 10 speed control
Flight controls: Wing elevons, full-flying canard, rudder

The flight performance of this model is excellent! The Gripen has the same wide speed range and excellent handling characteristics as the F-18 and F-15 Park Jets, and is surprisingly easy to fly. The biggest difference is that the Gripen is slightly less stable than either the F-18 or F-15 and is more maneuverable and quicker on the controls. Just like I suspected, the Gripen loves high alpha slow flight and is rock solid at sustained 30-40 deg alpha. I’ve been able to hold full aft stick and 1/4 throttle and watch the model crawl rock solid at very high alpha only a foot or so off the ground. The model can also do incredibly tight low-level turns with no hint of stalling by holding full aft stick and full throttle, just like a 3D ship. And of course it also flies well at high speed and easily flies as fast as I'm comfortable flying a foam airplane (about 50 mph). Just like the other Park Jets, the Gripen performs best with a power setup that provides 15-20 oz static thrust and 45-50 mph pitch speed.

But the best part about flying the Gripen is that the double delta planform looks just awesome in the air--almost like a spaceship. SINISTER is the best word to describe it! It’s just a thrill to watch this model fly. I’m hoping to get some flight video shot and posted soon (if the weather cooperates).

Currently, I recommend flying the Gripen with mixed canard/elevon flight controls for pitch. My model is set up so that full aft stick deflects the canard trailing edge down 3/4" and the wing elevons trailing edge up 3/8”. This setup provides excellent pitch control at both high speed and low speed and good stall characteristics. However, I do intend to test other mixing combinations to see if anything else works better. My model also has rudder control, which is optional but invaluable for providing directional control during high alpha flight.

For those of you that don’t have easy access to Depron or want to save time printing plans and cutting out parts, this design will soon be available as a laser-cut kit from www.3dfoamy.com. Levi puts out excellent quality kits that will save you a lot of time relative to scratch building! Kits should be available in a few weeks.

Enjoy, and as always, post pictures if you build it!

Steve

[jetset44]

Here are some more pics of the prototype, including close-ups of the canard installation and the motor installation and a family shot showing the Gripen along with the F-18 and F-15 Park Jets.

Steve

[jetset44]

Here are some pics taken during construction of the Gripen that show the internals. I’ll post more construction info soon.

Steve

[jetset44]

Here are the plans for the Gripen Park Jet. As usual, these plans consist of two files—a scaled assembly drawing that shows how everything fits together and a full-scale parts template. The parts template is posted in both tiled and non-tiled formats. Previews are posted below to show how the plans should look when assembled. Enjoy!

EDIT: Here's a link to an illustrated construction guide for this model:

http://www.parkjets.com/JAS_39_Park_Jet_Construction_Manual.pdf

Steve

[TBolt]

All I can say is WOW! All of your designs fly so awsome. The only problem I have with your airplanes, is that I am all out of electronics to install in any more planes.
You are the MAN!

[Brauer]

WOW STEVE! These plans looks great! here's the markings used at the Gripen
http://brauer10.1go.dk/swedish.jpg

[Iswald]

Yes Yes Yes!!!!!HeeHaw Whoooooooiieeee!!!
Thanx!!!Great Fantastic !!!!
Let Construction commence!!

[Rane]

WOW STEVE! impossible beautiful plane.
-rane

[edkoz]

Steve:

Thank you.

Oh well .... I've got the extra depron. I'm off to Kinkos for some full size plans. I'm going to be on a first name basis with the people at Kinkos if you keep this up.

Ed

[Ceeray]

Damn!! And I already started the T-38....

:eek:

[fuelsguy]

Steve,
Another great model.
With this construction technique becoming popular can we keep track of how many people are designing different airplanes?
I'm half way though an F-4 build and then found the thread of the Finnish F-4 plans.
How about having people post "Designs in progress" on one of these threads, maybe the F-18 one, and maybe "Designs wanted" as well.
Just a thought,
Ivor

[kscbob1]

Steve:

I've noticed that the gears on your HiMax gearbox are opposite the way they come from the factory. The factory has the 6.66 ratio set up initially. Did you reverse them because this is a pusher?

Bob

[Micronics]

Nice Job Steve!
very cool jets!
thanks for the plans.

Allen

[trondb]

Well ,another nice one ! I`m out of words..
Steve, you keep ezoner`s busy :p

[jetset44]

Thanks for all the compliments. I'm looking forward to seeing how everyone else's Gripens come out! I'm sure happy with mine.

kscbob - Yes, I swapped the Himax gears from the 6.6 to 4.4 set since that gearing matches the speed and thrust range needed for this model better. Or did you mean that I've mounted the gears pointed the other way on the shaft? If I did, I guess I hadn't noticed that...

fuelsguy - Yes, there has been a virtual explosion of Depron jets lately, hasn't there. Isn't it great?!? And I don't see an end to this anytime soon since there are some many cool airplanes out there to be modeled and so many different ways you can size these jets (indoor micro, "pocket" size for small motors, "Park Jet" size for 100W motors, and scaled up 150% size for 150W+ motors). The possibilities seem almost endless! This is such a great time to be in this hobby. :D

Iswald - Wow, I can't tell if you're excited about this model or not from your post... ;)

Steve

[Spinner]

Congrats Steve--Another winner!! :) You certainly belong in the electric "Hall of Fame" with golden designs.

Joe

[jetset44]

Congrats Steve--Another winner!! :) You certainly belong in the electric "Hall of Fame" with golden designs.

Joe

Thanks, Joe. As a fellow "high angle of attack" enthusiast, you'll love the Gripen if you build one! It just loves flying at outrageous alpha.... :D

Steve

[edkoz]

I've got my head up my butt. This was supposed to be posted in the T38 Thread ... sorry.

It's starting to look like a Jet. Still have to sand the canopy and rear fuselage top, glue on the turtledeck, rear fuselage and set the motor mount.

I don't like not being able to access all the goodies so I made the aft fuselage top in two pieces. The aft piece will be held down with (6) 6-32 x 1/2 plastic nuts, washers and screws. I should have done this on the bottom of the fuse so they couldn't be seen. All six of the screws, washers and nuts only weigh 1 gram.

I just got the Gripen plans printed at Kinkos and it's killing me not to start it but I don't want two projects going at the same time. Should be starting the Gripen by Tuesday.

Ed

[aids]

I a j-39 too

[Thomas Nelson]

Another beauty Steve!

I've been meaning to offer a few words of appreciation for doing more than simply saying "look what I can do"; you've ALSO said "here's how YOU can too ... give it a try!" You've done more than simply help populate ezone with all kinds of pusher jets - you've gone about this in a way that has inspired others to explore, experiment and spin-off their own designs. A community where the whole is becoming more than the sum of its parts ...

It's cool to see the synergy thing in action. My hat's off to ya, guy. Looking forward to the other stuff you've got up your sleeve.

[Wayno-san]

Well put Thomas,
Thanks Steve for another fantastic design. I'm working on some nano Jets right now (currently on the F18E). I made a bluecore rought cut of an F15 that I was going to put a couple of EDF40s into, but your designs are much more scale. Not sure if I can get away with the weight of these beautiful planes and EDFs, but I'm going to try for my next project.

Thanks again for your tremendous efforts and epecially your generosity. You certainly have the right spirit for the season!

=Wayno-san

[Hepdog]

Un ******* believable.... Steve you are simply amazing. Sonic cruiser, VTO's and now this entire line of easy to build park jets. I gotta ask, do you actually work for a living or is this it ;) If it isn't, it should be. The boys at GWS etc could learn ALOT from you. I'm surprised they aren't banging at your door. Just as well, it appears everyone here is far more appreciative anyway.

Seriouslsy though, do you think a slighlty scaled down Grippen would be comfortable on CD rom power indoors seeing as it loves high A and turns tight? I don't want to wait 6 more months to try this one out.

PS I never swore up top. The server just didn't like my choice of words I guess.

[Iswald]

I a j-39 too

What landing gear Ru using??

[Brauer]

Steve, you did just inpire me to make a J35 Draken. Got the plans on the floor right now! Haven't sleep too much this night! lol :D

[erunway]

Steve... THANK YOU! FOR THE PLANSSSSSSSSS

[Mav]

That's just a unbelievable job Steve!
But though i'm not that good in building own airplanes it would be really nice to see the progress when you built it... but unfortunately it's already done =/

Just give me some depron and I'll try to build it =D

[jetset44]

Another beauty Steve!

I've been meaning to offer a few words of appreciation for doing more than simply saying "look what I can do"; you've ALSO said "here's how YOU can too ... give it a try!" You've done more than simply help populate ezone with all kinds of pusher jets - you've gone about this in a way that has inspired others to explore, experiment and spin-off their own designs. A community where the whole is becoming more than the sum of its parts ...

It's cool to see the synergy thing in action. My hat's off to ya, guy. Looking forward to the other stuff you've got up your sleeve.

Thanks for the very kind words, Tom! I've learned a lot from this community, and now I'm just giving a little back... :D

Steve

[jetset44]

Un ******* believable.... Steve you are simply amazing. Sonic cruiser, VTO's and now this entire line of easy to build park jets. I gotta ask, do you actually work for a living or is this it ;) If it isn't, it should be. The boys at GWS etc could learn ALOT from you. I'm surprised they aren't banging at your door. Just as well, it appears everyone here is far more appreciative anyway.

Seriouslsy though, do you think a slighlty scaled down Grippen would be comfortable on CD rom power indoors seeing as it loves high A and turns tight? I don't want to wait 6 more months to try this one out.

PS I never swore up top. The server just didn't like my choice of words I guess.

Thanks, Hepdog. Yep, I do have a day job and believe it or not it's also designing airplanes, except the commercial jet transport kind! :rolleyes: But after a long day at the office, I sure enjoy coming home and designing these birds--what I like to call "recreational engineering"! ;)

I think a scaled down Gripen would work very well on CD-ROM power. Maybe we can convince Sal C to crank one out for us quickly and give us a report! He's done both the 77% scale and 60% scale F-18s and F-15s, and built them in record time. It's not clear to me yet which scale works better on CD-ROM. The 77% keeps the wing loading down but the 60% lets you achieve a higher thrust-to-weight ratio. Sal--got any advice based on your experience?

Steve

[jetset44]

It's starting to look like a Jet. Still have to sand the canopy and rear fuselage top, glue on the turtledeck, rear fuselage and set the motor mount.

Ed

That T-38 is looking great, Ed! Nice work!

[RNAF]

Jetset44 RESPECT :)
I gotta make one flying BEFORE Christmas. First I gotta MAKE A CHOICE :)
I think I want a Gripen. How much room is there at the widest part? Do you reckon 2 EDF-40 can be fitted? Or do you reckon that'll be too heavy? I was thinking about elevator at the canards and aileron at the usual place.

Thanks.
Dave.

[DCobra]

Thanks, Hepdog. Yep, I do have a day job and believe it or not it's also designing airplanes, except the commercial jet transport kind! :rolleyes: But after a long day at the office, I sure enjoy coming home and designing these birds--what I like to call "recreational engineering"! ;)

I think a scaled down Gripen would work very well on CD-ROM power. Maybe we can convince Sal C to crank one out for us quickly and give us a report! He's done both the 77% scale and 60% scale F-18s and F-15s, and built them in record time. It's not clear to me yet which scale works better on CD-ROM. The 77% keeps the wing loading down but the 60% lets you achieve a higher thrust-to-weight ratio. Sal--got any advice based on your experience?

Steve


Hmmm, I'm guessing your employers name starts with a "B"??? :p

Steve, great work on this latest ParkJet! Your designs are definitely a credit to your employers engineering department, yourself, and to EZone for providing a means of mass delivery to a hungry bunch of e-fliers.

Thanks again for sharing with the R/C community, hope to see more awesome designs in '05!

[jetset44]

Got some great flying video today of the Gripen Park Jet at the local school soccer field, thanks to both the weather and the help of my wife (doesn’t she shoot awesome video?). These videos really highlight the incredible speed and maneuverability of the Gripen—I think this is my favorite Park Jet so far! Just a ton of fun to fly. Note especially how rock solid it is at high alpha, doing harriers like a 3D plane. If only I had a little prop blast over the controls, then I could hover it… :D

The video files are posted in the Ezone Gallery, but since the gallery has a file size limit of 10 MB I split the video into two files with each about 8 MB and 3 minutes long. Note the beginning of the second video features a closeup of the flight controls near the beginning to highlight how the coupled canard/elevons work. Here are the links:

Gripen Video 1 (http://rcgroups.com/gallery/showphoto.php?photo=12611)

Gripen Video 2 (http://rcgroups.com/gallery/showphoto.php?photo=12612)

I’ve also attached some flight photos taken today. The last shot shows the high alpha capability of this bird really well.

Steve

[DCobra]

Cool videos Steve! From the sounds of it, the neighborhood dogs loved it too...espescially when you opened the throttle at a minute and a half into the first video :p

Your right on with your description of the Gripen... she does look pretty "sinister". Menacing would be accurate as well. :eek:

Good stuff... got another plane to add to my ever-growing must build list!

[jetset44]

Cool videos Steve! From the sounds of it, the neighborhood dogs loved it too...espescially when you opened the throttle at a minute and a half into the first video :p

Your right on with your description of the Gripen... she does look pretty "sinister". Menacing would be accurate as well. :eek:

Good stuff... got another plane to add to my ever-growing must build list!

Yeah, the dang neighborhood dogs always go crazy when I fly at this field. That's why I usually put a music soundtrack behind these videos! But this time I thought I'd leave the raw audio since some folks like to hear the motor power up and down.

Steve

[Flyerboy]

Cool Steve !

Nice video !

Your plan couldn't come in better time.
Lost my Gripen yesterday due to an poor launch. :(

Will cut a new one from your plans :D

// Mats

Some pics from crashsite

[RoverTomcat]

Thanks a load, Steve!!!

I've printed the plans yesterday and start cutting my last two sheets of Depron later this week...

Oh, and I've just ordered a Hacker B20-18-L 4:1 along with a 9x7 folding prop for the Gripen! Ouch, this hobby is getting expensive! ;)

Anyway, the video was very impressive... I love the high alpha -> high speed transition!

Thanks again and best regards - Paco

[Spinner]

Steve,

Wow! What a video. How sweet it is! :) Expected you to reach out and hand land it!

Just an incredible display of model enginnering and flying skill. Thanks a million for sharing it. High Alpha forever!

I keep putting check marks next to names of my favorite airplanes as you continue to birth them. Just a few left:

F-8 (or A-7)
RA-5C Vigilante (one of the most graceful airplanes made--way ahead of its time technically)
SR-71
B-52/X-15 combo with pusher and drive shaft (larger version of Gary Jones model) at
http://www.rcgroups.com/forums/showthread.php?threadid=143761&highlight=5

Or any thing else with wings! :)

Thanks Again--You are the King

Joe

[Thomas Nelson]

That was a lot of fun to watch! Definitely a very aggressive profile. What kind of airtime are you getting with that combo and flying style?

[Hepdog]

Great video - good camera"person" :)

I see you installed a rudder on this one. After your test flights do you think it was totally required or can I go without?
I've already printed out plans at 75% but haven't put them together to see what that equates too in reality.

[jetset44]

Glad you guys liked the videos! Sure wish I could have posted better video quality, though. I have to compress them so much to keep the file size down...

Tom - I'm getting around 20 minutes of flight time on each of my Etec 1200 mAh packs with this "small field" flying style. I'd guess that if I had a larger field and spent more time at full throttle that might drop down to 15 minutes...

Hepdog - Regarding the rudder, if you just want to fly fast I'd say it's not necessary. But if you want to be able to crawl around the sky at high alpha under full control like in the videos it's virtually mandatory. The ailerons are very very sluggish at those speeds, and rudder is what you use almost exclusively for those low speed turns. The rudder on this bird was quite easy to install since it's a single tail fin (as opposed to the twin fin F-18 and F-15). I just ran a single .08 carbon pushrod braced by scraps of foam--light and simple.

Spinner - Yep, the RA-5 Vigilante is one of my favorites, too. But it's quite a ways down by future project list... :(

Hey Spinner, did you notice in the Gripen videos that the model appears to have a poorly damped short period mode? In most of the close shots you can see the nose gently oscillating up and down at about 1 to 2 cycles/second, at both high speed and high alpha (peculiar that it's not affected by speed). It appears to be stable and doesn't diverge, and doesn't really affect handling qualities significantly, but it is a trifle annoying. That's about the only vice I've found so far in the handling qualities of this model. I'm assuming this is due to the close-coupled canard that results in low pitch damping, but it might be due to a canard/wing interaction as well. Any thoughts?

Steve

[Spinner]

Steve,

Interesting pitch behavior, since it happens at high speeds as well as high alpha! Don't think I would blame pitch damping, tho--maybe you have a nonlinearity in the variation of pitching moment with alpha due to flow separation (or, as you suggest, adverse canard/wing flow interactions), resulting in a bounded, limit-cycle oscillation? Have you tried a more forward c.g., just to see what impact a new relationship of canard/wing incidence has on the pitch hunting?

Plan "B"-Take it with you to work at Big "B" and use one of the wind tunnels :) :)

Gotta get you a blue suit with an "S" on the chest--super designer, pilot, and researcher!

Keep us posted!

Joe

[jetset44]

A blue suit, huh? Faster than a speeding park jet, able to leap over tall battery packs, etc... :D

Anyway, I've only got 3 flights on the Gripen so far (the videos above were flight #3) so I haven't quite figured out exactly when and where this pitch oscillation is occuring. I have flown the model within a wide CG range (quite by accident!) and noticed the oscillation at both forward and aft CGs, though. You're probably right about the pitch damping, tho--a low aspect ratio delta wing wouldn't normally have a problem with that. Next time I get some good weather, I'll go out and do some more in-depth testing. I think part of the problem may also be that I have the exponential rates turned up too high. I'm running -60% right now and I can really tell when I hit the knee in the response curve in both pitch and roll--very non-linear control response. I'll tune them down a bit and see if that helps.

Steve

[GTMAXX]

You definitely got a winner there with the Gripen! Love those functioning canards - your video says it all and your high alphas with smooth flight characteristics sold me on your plane. As soon as the kit comes out I'll definitely be getting one. Please keep us updated with your developments on this one and any new settings for throws and mixing along with motor/prop configurations that you feel will make for a better performing bird. My hat's off to ya for one very fine looking and flying bird!! Keep up the great work as you never cease to amaze us with your creations!

Todd Walters
Leetonia, OH

[jetset44]

Cool! Will do, Todd.

[tolladay]

Steve,
Do you think you might try a turbulator on the canard, or maybe parts of the wing? Not trying to tell my grandma how to knit (I know it is YOUR area od expertise), but just shouting out ideas.

[Darren Hintze]

Grippen is one of my favorites. I now know which of these is getting built over Christmas break....

Hopefully I'll have some EDF conversion data by Late Jan early Feb....

Darren

[JHAN]

:) :) :)

[RNAF]

hey jetset,
I've got a lil' question; what's the max. thrust you get with your setup?


Thx,
Dave

[RNAF]

in yer backyard?

[rcjetpilot]

Pitch control

Steve,

How's the delta wing configured, Is is "mixed" elevon or is it pure aileron?
Is the canard working as the primary elevator source (pitch control)?

Generally speaking, a delta wing needs a fair amount on "up" deflection for a neutral setting. What I might suggest is setting/pinning the canard at "zero deflection" and trim the plane until you find the sweet spot for level flight. Then un-pin the canard and reduce its deflection by a 1/3.

If the canard is the only source of pitch control, it's wing area is far to small compared to the delta wing. For a pure canard planform you'll need atleast 20-25% of the main wing area for good pitch control.

The Gripen is kind of a canard enhanced delta:)

Just my 2c,

Bob.

[Brauer]

Australia?

[jetset44]

hey jetset,
I've got a lil' question; what's the max. thrust you get with your setup?


Thx,
Dave

Motocalc predicts 21 oz static thrust, which seems about right based on my flight results.

[jetset44]

Pitch control

Steve,

How's the delta wing configured, Is is "mixed" elevon or is it pure aileron?
Is the canard working as the primary elevator source (pitch control)?

Generally speaking, a delta wing needs a fair amount on "up" deflection for a neutral setting. What I might suggest is setting/pinning the canard at "zero deflection" and trim the plane until you find the sweet spot for level flight. Then un-pin the canard and reduce its deflection by a 1/3.

If the canard is the only source of pitch control, it's wing area is far to small compared to the delta wing. For a pure canard planform you'll need atleast 20-25% of the main wing area for good pitch control.

The Gripen is kind of a canard enhanced delta:)

Just my 2c,

Bob.

Yep, I realized during the design of this bird that the canard of the Gripen was not large enough to be the sole pitch control. That's why the model features mixed canard and elevons for pitch. Full aft stick produces 20 deg canard deflection and 10 deg elevons-up deflection. I fully intend to test other combinations of canard and elevon mixing, but for now I'm extremely happy with this setup and have low motivation to mess with it. If it ain't broke... ;)

For neutral trim at the CG I'm currently flying at, I've got a few clicks of up elevator trim that results in about 3-4 deg canard deflection and 1-2 deg up elevon deflection at neutral. But this is highly dependent on CG. When I tested more aft CGs the model trimmed with zero canard/elevon deflections, which indicates that canard downwash effects alone were enough to provide 1g level cruise trim.

Steve

[Iswald]

Guess were this picture is taken?

That is a easy answer......
in another airplane LOL

[DCobra]

Kinda looks like high desert areas of California and Nevada, but I'd venture to say it's more likely to be over the middle east? Whats a Swedish Air Force plane doing over a desert anyways?

[AceMigKiller]

I dunno,
Might be the desert, look at that ground formation.
Plus if I'm not mistaken those are mesa's in the background...hmm
Well, I'm a pilot not a geologist, what do I know :) Anybody got the answer?

[jetset44]

OK, OK, OK, I give. Where is it?

[Modellhobby]

Cutting Depron right now. Excellent work done on this model.
Thank You Jetset44!
Surf to http://www.gripen.com for pics and info of the real bird.
/Stefan

[jetset44]

You know, I was really hoping someone from Sweden would be the first to build a Gripen Park Jet. I thought that person might be Brauer, but it looks like Stefan is up to the challenge! :D Go for it, Stefan! I'm eager to hear how your model turns out.

Steve

[Flyerboy]

Guess were this picture is taken?

A fair guess would be SouthAfrica ???

// Mats

[RoverTomcat]

The pic's name is "grand canyon_small.jpg".

So, what's a Gripen doing over the Grand Canyon?

Paco

[empeabee]

... wife (doesn’t she shoot awesome video?).

YES

I’ve also attached some flight photos taken today. The last shot shows the high alpha capability of this bird really well.

Steve

I assume you also have the mowing contract for the field as well :D

Mike

[Brauer]

You know, I was really hoping someone from Sweden would be the first to build a Gripen Park Jet. I thought that person might be Brauer, but it looks like Stefan is up to the challenge! :D Go for it, Stefan! I'm eager to hear how your model turns out.

Steve


hehe, could have been. But since it's the last week of the term I got hell a lot of tests. Did a big physics test today... But the best part were when we were told to skip the rest of the day, just after lunch! :D Got another one tomorrow, "natureknowledge", a mix of physics, biology and chemistry. As you see I'm quite lack of sparetime this week ;)

[ravencsr]

Thankyou so much for all the effort you put into these jets Steve, its fantastic to be able to build and fly these planes you create. :)

I guess its time you give us a sneak picture preview of that F-14 Tomcat you're working on!!!! ;) ;) :D

[Modellhobby]

About the picture posted by JHAN.
Swedish Airforce did participate in the jubilee "Aviation 100 years" september 2003 in USA. Two Gripen with two C-130 as support flew from Sweden to Andrews AFB. Next stop was Nellis AFB and then back to Sweden. Of course with some stops on the way between Sweden and USA.
So, the pic can very well be from Gran Canyon.
Now, back to my buildingboard :D
/Stefan

[jetset44]

Thankyou so much for all the effort you put into these jets Steve, its fantastic to be able to build and fly these planes you create. :)

I guess its time you give us a sneak picture preview of that F-14 Tomcat you're working on!!!! ;) ;) :D

You're welcome! It's always good to hear people are enjoying these plans.

Hate to disappoint, but after going full bore on these jet designs for the last 4 months I'm a little burned out and don't plan to work on the F-14 until after the holidays...

Steve

[ravencsr]

You're welcome! It's always good to hear people are enjoying these plans.

Hate to disappoint, but after going full bore on these jet designs for the last 4 months I'm a little burned out and don't plan to work on the F-14 until after the holidays...

Steve

Not a problem Steve ;) Have a safe and great holi period and enjoy yourself.

Same to everybody else out there.

Raven.

[Iswald]

Yep Steve you deserve a long holiday!!!!
I think i speak for every one when i say yet again THANK YOU VERY MUCH!!!
Have a great holliday

[JHAN]

In USA!! (sep2003).

Swedish Air force was invited to Washinton (Andrews AFB) and Nevada (Nellis AFB). The pilot in the 2 nd Gripen took this pic after passing Grand Canyon.

[JHAN]

Sorry the year was 2003, short memory....

[DCobra]

You're welcome! It's always good to hear people are enjoying these plans.

Hate to disappoint, but after going full bore on these jet designs for the last 4 months I'm a little burned out and don't plan to work on the F-14 until after the holidays...

Steve

Wow, it's been a fast 4 months too. I went back to page one on the F-18 thread the other day and saw it was posted first week of September. Where did all the time go?

By all means take a loooong break and recharge the creative batteries Steve. Definitely get out and fly your creations too, they are too cool to leave sitting to collect dust. Maybe by the time you put out another parkjet i'll be caught up on building whats already out there. :D
And lastly, happy holidays to you and all of the other parkjet builders I've gotten acquainted with in the past few months.

-Paul

[Twin-Jet-Crash]

I am not very good on understandig the setup of the controls on this plane.
How do you get the elevons and the canard to move at the same time, when you pull the stick? Is this a setup on a computer radio, or is it hardware a hardware fix?
Will it be possible on my Multiplex Pico Line control?

[DCobra]

I am not very good on understandig the setup of the controls on this plane.
How do you get the elevons and the canard to move at the same time, when you pull the stick? Is this a setup on a computer radio, or is it hardware a hardware fix?
Will it be possible on my Multiplex Pico Line control?


It's done with radio mixing, and I'm not knowledgeable about Multiplex radios so I can't help you with that question.

-Paul

[J Morgan]

You're welcome! It's always good to hear people are enjoying these plans.

Hate to disappoint, but after going full bore on these jet designs for the last 4 months I'm a little burned out and don't plan to work on the F-14 until after the holidays...

Steve

Maybe that will give us time to build them and catch up to you Steve!


J

[tolladay]

You're welcome! It's always good to hear people are enjoying these plans.

Hate to disappoint, but after going full bore on these jet designs for the last 4 months I'm a little burned out and don't plan to work on the F-14 until after the holidays...

Steve,
If it helps I have this problem with the day job (graphic design). There's something about the creative process that needs to be carefully maintained, and that often means taking some kind of a mental vacation. In fact my escape from work is this hobby. What you need is something you enjoy that has no purpose but to make you smile. It's best if your engaged in it, and not passive (like watching movies), but it doesn't really matter what you do, as long as you do it fully emersed.

You might try taking a hike with a camera, painting (as in fine art, not the house), reading something like poetry (as opposed to fiction or airplane related non-fiction), or something I found recently that works really well, althought I must admit it sounds really silly: decorating cookies. For this you need a womens' hobby store like Michael's. There you'll find lots of stuff like pre-colored frosting, sprinkles, cookie cutters, and even pens with eatable ink. Like I said, it sounds very silly, but suger cookies are dead easy to bake, and you can get as deep into it as you want. There's something about the ephemeral quality of a cookie that makes it fun to work with: No matter what, you know it's not going to last long. Best part is you get to eat your mistakes. :D They also make handy gifts for the neighbors.

[Twin-Jet-Crash]

It's done with radio mixing, and I'm not knowledgeable about Multiplex radios so I can't help you with that question.

-Paul

Is it possible to fly this plane without this mix (controlling altitude/pith only with the canard)?

My radio have: V-mix, diff-mix and power mix. I dont have any other mixes :(

[rcguy01]

It's done with radio mixing, and I'm not knowledgeable about Multiplex radios so I can't help you with that question.

-Paul

can you give some details about how you do mixing on
your radio so we could understand and do in a similar
way in our radios, hopefully.

thanks

[Mav]

Hi.. I only have got elevon mix and v-tail mix. Can i make it anyway ?

[jetset44]

All,
I'm not sure yet what combinations of mixing will work well on this jet for pitch control--all I know for sure is that the mixed controls I've got now work extremely well as is. To achieve this on my Futaba 9C transmitter, I did the following:

* Plugged the canard servo into channel 2 (elevator)
* Plugged the two elevon servos into channels 1 and 6 (aileron and flap)
* Enabled the Flaperon function for the two elevon servos
* Enabled elev->flap mixing and dialed in 50% mixing (which makes the elevons both deflect up when the canard is deflected trailing edge down)

With the 50% elev->flap mixing, full aft elevator stick produces about 20 degrees canard deflection and 10 degrees elevon deflection. A computer radio with mixing is required to achieve this.

While I do intend to test other mixing scenarios (including canard-only and elevons-only), I am skeptical either of those will work well. I don't believe the Gripen's canard is large enough to allow it to be the sole pitch control, however, if you don't actuate the canard the airplane might not have acceptable stall characteristics (deflecting the canard ensures that it stalls before the wing, thereby producing the a good nose-down pitching moment at stall). Thus, mixed canard/elevon pitch control ensures good control power as well as good stall characteristics.

Steve

[rcguy01]

All,
I'm not sure yet what combinations of mixing will work well on this jet for pitch control--all I know for sure is that the mixed controls I've got now work extremely well as is. To achieve this on my Futaba 9C transmitter, I did the following:

* Plugged the canard servo into channel 2 (elevator)
* Plugged the two elevon servos into channels 1 and 6 (aileron and flap)
* Enabled the Flaperon function for the two elevon servos
* Enabled elev->flap mixing and dialed in 50% mixing (which makes the elevons both deflect up when the canard is deflected trailing edge down)

With the 50% elev->flap mixing, full aft elevator stick produces about 20 degrees canard deflection and 10 degrees elevon deflection. A computer radio with mixing is required to achieve this.

While I do intend to test other mixing scenarios (including canard-only and elevons-only), I am skeptical either of those will work well. I don't believe the Gripen's canard is large enough to allow it to be the sole pitch control, however, if you don't actuate the canard the airplane might not have acceptable stall characteristics (deflecting the canard ensures that it stalls before the wing, thereby producing the a good nose-down pitching moment at stall). Thus, mixed canard/elevon pitch control ensures good control power as well as good stall characteristics.

Steve


Thanks Steve, now my mind is clear. I need a new
computer radio. A primitive computer radio I have does not
have the mixing needed. Tone of Thanks again

[DCobra]

can you give some details about how you do mixing on
your radio so we could understand and do in a similar
way in our radios, hopefully.

thanks
I'd be glad to tell you, but I dont even know how to do it on my Eclipse 7...still learning all the options on that radio 9 months after getting it.

[empeabee]

I'd be glad to tell you, but I dont even know how to do it on my Eclipse 7...still learning all the options on that radio 9 months after getting it.
Hell I've had mine (computer Tx) 4 3 years & still learning !
Mike

[Akura2]

I have a Futaba 7C...which is cool because you have most of the options of the 9C..but for a lot less money if you don't need the two extra channels

[Iswald]

I was wondering .....

http://www.rcgroups.com/forums/showthread.php?t=305004&page=1

This should rock!!!
HIGH HIGH HIGH ALFA (Insert evil laugh here!!)

pic by EDC121

[fuelsguy]

Hi guys,
Here are a few shots of my attempt at a park jet a la Steve. The new(?) thoughts added are:
1, Prop shaft drive to move the motor forward
2. Use of depron to transition from square section to fully round fuselage sections. See the nose and exhaust pipe area.

Still need to add radio gear, waiting for Santa to deliver the motor, just have a GWS in for sizing.

Ivor

[jetset44]

Hi guys,
Here are a few shots of my attempt at a park jet a la Steve. The new(?) thoughts added are:
1, Prop shaft drive to move the motor forward
2. Use of depron to transition from square section to fully round fuselage sections. See the nose and exhaust pipe area.

Still need to add radio gear, waiting for Santa to deliver the motor, just have a GWS in for sizing.

Ivor

Looks very nice, Ivor. How long is the drive shaft you used, and how is it supported (ball bearings? bushings?). Moving the motor forward will certainly help the balance issue.

And did you use a solid block of Depron for the transitions?

Steve

[fuelsguy]

hi Steve,
The drive shaft is about 18 inches long, 5mm carbon tube. The front connector is a 1.5 inch tylon rod, the motor end is drilled to be a screw in fit to the GWS prop shaft, the shaft end is drilled to a sliding tight fit on the shaft, and then i used a 1/16 dia roll pin to take the torque. The prop end is a nylon bolt, also drilled to be a tight sliding fit on the shaft. Interestingly, when you tighten the prop on to the bolt, the bolt get squeezed onto the shaft, and you get a good tight fit. The aft bearing is about three inches forward of the prop. It's a ball bearing, 5mm I/D 8mm O/D. At normal running speed that's all you need, but as the shaft goes through it's natural frequency, the shaft can get a bit wild, so I put a "support" bearing about 60% of the shaft length so the shaft doesn't destroy the airframe as it accelerates/decelerates. I have a test bench if you want to play.
Round fuselages: I didn't use a solid block. What I did was build a rectangular fuselage section just like your F-18. Then I cut 45 degree slice off one side the rectangle and then glued a new depron piece over the hole. repeat for the other sides and you have an octagon fuselage which can be sanded to a round fuselage. As you get bigger you will have to go to more "sides" to avoid sanding away the depron. If you lay out a cirlce on the F-18 nose, then lay depron at 45 degrees so the outside kisses the circle you can see what I do. Transitions are easy as you just make the cut narrower and narrower until you are back to a rectangular section.

Ivor.
PS I plan to ask you to fly this on the maiden flight, with Rhodri running the video camera.

[fuelsguy]

Steve,
Forgot to add a few things. Current weight is 12.4 oz, green airframe plus motor/drive shaft. With avionics, prop and paint I figure to end up around 19oz. With a 1100 3s P-L I can balance with the battery in the cockpit, and no additional ballast.

Ivor

[jetset44]

Sounds really neat, Ivor. I wouldn't mind seeing some pictures of that drive shaft set up. Long drive shafts have always been notoriously hard to get to work due to all the vibration issues. How smoothly does this set up run throughout the throttle range with the support bearing at 60%? Is it comfortable at all throttle settings?

Great idea on the foam for getting better rounded shapes!

Ah, so we both know Rhodri. Are you a "Lazy B" employee as well? Seattle weather permitting, maybe we can meet up to do some flying!

Steve

[Wade Joos]

What you might try is actually putting a slight curve in the path of the drive shaft.
Just move your middle bearing off center a bit & see if you like it. That is if the shaft is flexible enough to do this.
It may help with the vibration issue.

[fuelsguy]

Steve, I'll get some shots of the drive shaft this weekend hopefully. Yes I was a Boeing guy for many years, now semi-retired, I helped Rhodri get in to engineering. He can fill in the details.
Wade, Thanks for the thought, I haven't played with trying to cure the accel vibration as it's only there for a moment as the motor come up on speed. I'll try it on my little test bench. Currently I'm using a teflon journal bearing so I might have to go to a bb one if I bend the shaft. The shaft can take a little offset, so it might work out.
Ivor

[Iswald]

Dont want to enterupt.......
Has anyone looked at the "Raptor pusher aerobatics"?????
http://www.rcgroups.com/forums/showthread.php?t=305004&page=1&pp=15

This should work sweet on the gripen!!!

echo
echo
?

[RNAF]

Hi guys,
Here are a few shots of my attempt at a park jet a la Steve. The new(?) thoughts added are:
1, Prop shaft drive to move the motor forward
2. Use of depron to transition from square section to fully round fuselage sections. See the nose and exhaust pipe area.

Still need to add radio gear, waiting for Santa to deliver the motor, just have a GWS in for sizing.

Ivor


Uhm... wow!
Nice idea about the drive-shaft!
I would like to see more of that concept.

Dave

[volorc]

hi steve beautiful plans you have designed.. I tried to build this plane with your plan.... I changed only the motor unit... an EDF55 with a MODEL MOTOR MINI AC1215/12 and probably 3S2P 2400 liPo battery... I didn't fly the model yet... I hope I'll be lucky.. what do you think about it...

[Mav]

Volorc:

It looks terrific! But do you think the EDF55 will be enough? What does the model weight?

[rcguy01]

good lord, finally an EDF Gripen... :-)
Please let us know how your coming EDF 55 Gripen.
What is your power set up? motor? Cell pack?
AUW? and better yet more pictures and video of maiden flight.
Thanks.

[volorc]

I'm using the EDF unit without its original motor, I mounted on A brushless motor...the type is Model Motor (The same of AXI) Mini AC1215/12, it turns 4750 Rpm per volt. and the factory says it's good for fan till 65 mm.. I have to prove it for the thrust because i have no idea... without the exaust cone it pushes very well... I still finishing the plane... and I want (a lot)to see how it flyes.... (if it Flyes obviously....)

[rcguy01]

if you could fit the GWS EDF 55 inside the Gripen fuse
then I think a better fan is the Vasa 55 that produces
more thrust than the GWS EDF 55.

We do things in different ways though.
I would think of a Razor 2500, Vasa 55 and 4s lipo.
That might be my power set up on the Gripen then

[volorc]

I'm using the EDF unit without its original motor, I mounted on A brushless motor...the type is Model Motor (The same of AXI) Mini AC1215/12, it turns 4750 Rpm per volt. and the factory says it's good for fan till 65 mm.. I have to prove it for the thrust because i have no idea... without the exaust cone it pushes very well... I still finishing the plane... and I want (a lot)to see how it flyes.... (if it Flyes obviously....)

[volorc]

rcguy01
I'm agree with you that Vasa55 are better fans than EDF..but the second one was ready and above all available at my house :) for the vasa 55 probably I should waited a lot. The problem is I'm often away from home for my job.. and i don't have so much time for waiting something by postoffice. sincerelly it was a speed idea of the moment.. the vasa maybe for the next(better) plane.