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Skymaster Gripen with scale features

Old 08-23-2005, 06:57 AM
  #1  
Speedbird66
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Default Skymaster Gripen with scale features

Gentlemen (and ladies)
Here are some pictures of my Skymaster Gripen which will be ready to fly in 3-4 weeks time. The original ARTF model has been updated with some scale features:



9 added small fin's.
The leading edge of the air intakes has been made seamless and thinner.
The rudder servo is moved in to the rear of the fuse and rudder controlled by torque rod.
Cockpit updated with eject seat, pilot, instruments and head up display.
Missile pylons custom made and fitted to the wings and fuselage (+300g).
Central drop tank (100-150g)
4 off AMRAAM missiles (50g each)
2 off Sidewinder 9L missiles (35g each)
Navigation lights (red/gren)
Strobe (rear of fin)
Nose wheel door modified to 3-door set up with landing light in front door
Main doors cut up to 2-door set up to allow sequenced gear door timing (door closes when gear is out).

Finally has Michael Graff in Sweden done his magic with his air brush. Thanks again !

/Johan


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Old 08-23-2005, 06:59 AM
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Topgun2mo
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Default RE: Skymaster Gripen with scale features

Beautiful!
Old 08-23-2005, 07:46 AM
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Aero65
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Default RE: Skymaster Gripen with scale features

I saw the pics on the Skymaster site. Awesome job on the Gripen just fantastic!!!
Old 08-23-2005, 08:39 AM
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Default RE: Skymaster Gripen with scale features

Johan, Super looking Gripen!

Hey Duke, can you re-paint mine to look like that?


Regards, Bill
Old 08-23-2005, 09:04 AM
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Default RE: Skymaster Gripen with scale features

Hi Bill,
I'll have to talk to the Air brush artist about this if you are serious . . .
Old 08-23-2005, 01:08 PM
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Stig Andersen
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Default RE: Skymaster Gripen with scale features

Hello Johan.

Will you bring it to Laxå next month. I sure would love to see it for real. Just fantastic. I have got to get me one soon.
Old 08-23-2005, 03:58 PM
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Aero65
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Default RE: Skymaster Gripen with scale features

HI Bill

I don't know if im that skilled, But I could give it a shot . Man I love those scale details that johan did I will have to do one up like that when I have some time. I'll bet it will fly great with the pylons. Rob from Alabama had rails and ordinance on his and it flew and looked good.

Johan what did you make the missiles out of?
Old 08-23-2005, 05:21 PM
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Speedbird66
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Default RE: Skymaster Gripen with scale features

I'm glad you all like it guys !

Stig:
I'll see you at the Laxå meeting 3-4 Sept. I doubt my Gripen will be ready to fly but it will definately be there for static display.

Aero65:
It is funny how the small details makes such a great improvement in appearance.
All features (pylons and missiles) are made in the traditional way of moulding. They are first shaped in sold material (like Skymaster Jets do). Pylons are shaped in wood (pine tree) and missiles from aluminum tubes with wooden nose cones.
Pylons and Drop Tank are laminated with one layer of 100g/m² satain + one layer of 160g/m². Missiles from two layers of 100g/m². Missile fin's are made from 1mm plastic card.
I was cheeting with the pylons since Einar Jonsson (Captain of the Swedish JWM team) had the moulds already made up in 1:6 scale. I used his moulds to make mine but I had to adjust them afterwards to fit the 1:7 sized wing. That saved me a lot of time.
I could not find any standard g/f or c/f tubes in the right dimension Ø18 for the Sidewinders and Ø25 for the AMRAAMs so I had to do them the hard way. Man it's difficult to make a seamless tube of Ø18mm . . . I probably spent every evening in 3 or 4 weeks to make them and it wasn't the most healthy period in my life.
All added small fins's to the fuse are made from 2mm c/f laminate. They are fixed inside the fuse with c/f roving and zap.

There are some really good high res pic's on www.Gripen.com look at Gripen Images Photos 2005.

By the way - I feel like a school kid with a dinky toy when I compare my ARTF Gripen with his project. When you have seen the 100% scale gear in action you realize that there will never be any one else trying to do this . . .
Old 08-24-2005, 05:50 AM
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F900
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Default RE: Skymaster Gripen with scale features

Wow very impressive..... Makes me want to fly the Gripen again.
Old 08-26-2005, 03:17 PM
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Rob B.
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Default RE: Skymaster Gripen with scale features

Hi Stig:

Beautiful job on the Gripen, I really like the AIM-120s on your model. I did mine with a load out of AIM-9s. Here are a few photos of my model after 50 flights.



Rob B.
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Old 08-26-2005, 05:38 PM
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Speedbird66
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Default RE: Skymaster Gripen with scale features

Hi Rob,
You have done a great job with the details on your model. It looks like your missile pylons are a bit smaller and sharper compared to mine and in my opinoin your's look more like the original. The 1:48 plasic model from Alitalia is really good for reference. I also notice the details of your missiles - wow.

Were there any noticable effects of flying the model with the drop tank or missiles ? How powerful is your turbine? What is the dry weight of your model?

/Johan (Speedbird66)
Old 08-26-2005, 06:10 PM
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Falcon 64
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Default RE: Skymaster Gripen with scale features

Hej, Johan.

Like I said to you, some minutes ago... This is the best one of this model yet, and will take some efforth to top...
I might missed a few, but don`t really think soo.

I reconn my Gripen to be jumpy in take-off, as the mongst of them.. This is before my freak split (scale ) elevon setup is finally sorted out.
I`ll tell you about my scale flap/canard settings later, when this is finally sorted out.
I suppose it will lift-off moore in a nicer/slower manner after this.


Anyway, the external stores on yours, are one of a cind yet, and the guy who air-brushed the bird, can expect moore to come..
I guess you let us know how it performed very soon[:-]
Both thumbs up, Johan!

Regards

Gudmund

Old 08-26-2005, 06:22 PM
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Rob B.
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Default RE: Skymaster Gripen with scale features

Hi Johan:

My Gripen flys pretty much the same with the missiles and rails on, the centerline tank reduces the vertical height during large loops, but not all that much. I was a little worried about the test flights with all stores on it, but there really is no noticeable difference in the way the model handles. This model is powered by a BMT-120 turbine with 30lbs of thrust, I also removed the center inlet duct and added a 40oz Dubro tank to bring the fuel capacity up to 1 gallon. The model has not been weighed, as I need to buy a new scale...
I also used the same plastic model kit as a reference and an Aerofax book on the Gripen.
Also, does the upper surface color look correct, I had difficulty matching it because photos of the plane vary from more blue to more grey, so I took a guess..

Rob
Old 08-26-2005, 06:57 PM
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Speedbird66
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Default RE: Skymaster Gripen with scale features

Hi Gudmund, good to hear from you.
The rotation and take off for the Gripen models has been said to be very abrupt. The cure for this has mostly been to extend the nose leg to increase the lift of the main wing. (The Euro fighter looks like this). However, the original Gripen stays pretty much in level all the way down the runway until rotation. The answer to this (I belive) is the correct usage of the canard. I will use dual rates for the canard and apply a fair amount of up elevator and canard lift from the very beginning at take off. The original uses a canard throw compared to at least 25 mm on the model at rotation. Once air borne I plan to reduce the canard rate to +/- 5 or 10 mm and keep it that way for landing. Too much canard movement may cause the model to stall the nose at slow speed as some have reported. Some people have also reported that the gripen lands nice and smoth with a high nose attitude without even using the canards.

Anyway - I will find out sooner or later if I'm wrong . .

Rob, thanks for your info. That was really what I wanted to hear cause I really want to fly it fully dressed.
I will use my Behotec JB130 of similar thrust as yours (135N). The original 2,2 litre will have to be 3,0 for a resonable flight time.
The colour of the Gripen is difficult because the paint it self is affected by the sun and weather. Apparently when a Gripen is in for a repair and a panel needs to be repainted a colour sample is taken and the the paint is i toned accordingly! The colour of mine is made slightly lighter than the full size original because colours looks darker on smaller surfaces . . .
I just realised you are my wing man with no 49 - mine is no 50 !
:-)
Old 08-26-2005, 08:20 PM
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Falcon 64
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Default RE: Skymaster Gripen with scale features

Have a look at this picture.
Note the canard versus the elevons..
OK, this is a computer controlled full-size, but elements are to be copied on our models..

To set the AOA much higher than it`s supposed to be, is a nono to me.
A easier way to solve the problem, OK, but i think there are other ways to go too.

Gudmund
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Old 08-26-2005, 08:50 PM
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Rob B.
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Default RE: Skymaster Gripen with scale features

Hi Johan:

Here's some unsolicited advice on test flights with the Gripen. First, I would avoid doing any experimental stuff with the canards untill you have completed a few flights.( I think the main gear are mounted a little to far back, which increases the takeoff run, mine uses 425ft). Second, set the CG at 140mm and use the skymaster control throws with some exponential. 3rd, set about 7clicks of up trim in the landing pattern, this makes it very easy to see if the model's approach speed is too high. A Gripen with the nose level on approach is flying much faster than it needs to be(although it will land like this, the soft main gear struts take a beating). I can land and stop mine in 300ft with mininal braking.

Rob
Old 08-27-2005, 03:24 AM
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Default RE: Skymaster Gripen with scale features

Gudmund,
take a look at this picture:
[img][/img]
This is just before rotation. Your picture is taken after rotation. Look at the difference in canard and elevator throw.

Rob,
CG of 140mm and a very little canard input will be my starting point.
I have noticed that the main gear is very soft. I'm working on a semi scale main leg that has a wider stance and is stiffer.

I need to fly the Gripen and get some experience before I discuss this further ( or I will find my self in deep water) - but it is an interesting subject.

/Johan

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Old 08-27-2005, 03:29 AM
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Default RE: Skymaster Gripen with scale features

On a closer look at your picture Gudmund I realize that it must be landing - not taking off. At least there are no reheat. As you said before - it is computer controlled so who knows what the heck is happening anyway.
/Johan
Old 08-27-2005, 03:41 AM
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Default RE: Skymaster Gripen with scale features


ORIGINAL: Gudmund Malones

Have a look at this picture.
Note the canard versus the elevons..
OK, this is a computer controlled full-size, but elements are to be copied on our models..

To set the AOA much higher than it`s supposed to be, is a nono to me.
A easier way to solve the problem, OK, but i think there are other ways to go too.

Gudmund
What's happening here is the elevons are increasing the camber on the wing providing more lift for a slower landing speed. The canards are then countering the increased nose-down pitching force. The end result is much slower landings.
Old 08-27-2005, 04:39 AM
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Default RE: Skymaster Gripen with scale features

http://home8.inet.tele.dk/jan_p/temp/morten022.avi



Here is a video clip of my Gripen taking off on grass 300ft long.
i have added sidewinders on my Gripen not as fancy as yours but ok
and i am planning to add an center droptank.
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Old 08-27-2005, 06:21 AM
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Aero65
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Default RE: Skymaster Gripen with scale features

Hello all

Let me say first that I'm sure that many of you know some of the things I will comment about, this is just for your information stuff, if I have some facts incorrect pls let me know tks.

Please remember that the full scale Gripen has a cg that is farther rear that we would ever be able to fly without a computer so some of the control movements and deflections are possible due to relaxed stability and computer control.

The canard of the SM Gripen is also much smaller than the real Gripen and suffers from reduced Reynolds numbers like all our models do. So at the lower airspeed like landing I'm sure that the canard is not producing nearly percentage of lift possible with the real Gripen.

We fly all of our SM Gripens with 147 mm to 153 mm cg At this cg we have found that the canard throw needs to be minimal, otherwise it is very easy to get into a PIO or Pilot induced oscillation on the flare during landing.

If you are going to try and take off using lots of canard make sure you have a way of changing the throw in-flight. During your takeoff roll leave your controls neutral until speed builds to let the wings and canards start to have laminar flow. If you hold full control like a soft field take off it will take longer to get the surfaces flying, and then bang they will become effective all at once and you will jump into the air.

We were able to reduce the take off roll on our F-18E this way by at least 100 ~ 150 ft.

If you get some other control movements to work please let us know, I would be very interested to see what you find, just be cautious.
Old 08-27-2005, 08:23 AM
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Default RE: Skymaster Gripen with scale features

http://home8.inet.tele.dk/jan_p/temp/morten023.avi

video link of landing not the best landing i ever made
canard movent is 8mm up and 5mm dovn cg.145mm.
i can fly slow for landning.i have learned now to keep power on for landning.
Old 08-27-2005, 05:35 PM
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Default RE: Skymaster Gripen with scale features

[quote]ORIGINAL: Aero65

If you are going to try and take off using lots of canard make sure you have a way of changing the throw in-flight. During your takeoff roll leave your controls neutral until speed builds to let the wings and canards start to have laminar flow. If you hold full control like a soft field take off it will take longer to get the surfaces flying, and then bang they will become effective all at once and you will jump into the air.
END QUOTE

Thanks for useful info. I will have the canard set up with dual rates - the large throw only for take off (as I said earlier). The very useful piece of information is to wait with the elevator/canard input until the speed has picked up.
Intention is to have the gear set up like the original with the main wing neutral and the canard slightly negative. During take off I will then need to pull the stick back slightly to level the canard.

/Johan
Old 08-27-2005, 05:41 PM
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Default RE: Skymaster Gripen with scale features

you just have to feel the stick and fly the plane[8D]
Old 08-29-2005, 05:43 PM
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Default RE: Skymaster Gripen with scale features

This model is very good, but its price is very low from here:
http://www.jetlegend.com/show.php?sn=10

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