I've just bought a ready built unflown Saab Viggen (Jim Fox). It didn't come with any plans, or instructions so can someone please tell me where the C of G should be?

Thanks

m.lello

Hi
Finally found my plans for the Viggen. On the 1/10th size the CG is placed 100 mm (4 in) behind the leading edge of the main wing where it enters the fuselage. This is a safe starting point for balance.
Otherwise, the most valuable tip on setting up controls, be very careful with the aileron throw. Use MAXIMUM +/- 5mm ( and some expo for my liking).
Use +/- 20 mm for elevator throw.
For first flight, do not use canards, you can experiment with them later, most people here never use them, as they have very little effect, but complicates flying the model.
Good luck!!

Here is a picture of my Viggen 1/9th scale. Kit and gear from Einar Johansson in Sweden. Still in primer, but it is flown!

Trying again

Viggen internals. Own made ducting and tanks. Powered by a Simjet at the time of the picture, later changed to and flown with JetCat P-120.

Hello,

Where to get the Einar Viggen kit, is there any website ?

What is included in 1/9th scale kit, and what is the quality of it ?

Is it full composite with panel lines or standard GFK/foam ?

Best regards,
Kristijan

I have an original Cressline Viggen semi kit if anyone wants it at a great price...fuselage, cores and inlets. I have rough plans.

Dave
PS I originally got it from Gary Mueller

Great plane. I would love to have one at 90"------- Awesome

Dave R

Here is a picture of Einar's 1/8th Viggen taken at Barkarby, Stockholm last year

Einar makes excellent kits, but they require a lot of work. Fiberglass fuselage with foam cores. No panel lines molded, but the outline and profiles are accurate scale, based on SAAB factory drawings. Einar is a Viggen fan, and has made molds for 1/10, 1/9 and 1/8th scale.
I do not know if he is producing kits at the moment as he is busy on his new JAS Gripen model.
Quite a few Viggen kits have been made, but not nearly all completed, so it should be possible to find one lying around.
Rumor has it that www.overfly.dk has obtained a set of molds, maybe a place to start.

Hi Per Strommen:
Thank you for the pic's. Could you send them to me, They are so small I would like to see them larger. May I ask why he would make a Gripen in such a small scale. I mean that plane should be done in turbine size a least.

Dave R [email protected]

Dave,
his new Gripen is definately turbine size. I am not certain about the scale, but the model is nearly 100 inches long.

Will mail you the Viggen pictures.


Per

Hi Per:
Thank you------- Oh my God, If he is a scale designer like you say, you have made me a very happy man. I love the Grippen and would love to have one at 100". That would be Awesome. I have the full documentation on it and have been waiting for someone to do her. As with the Russian SU-34 in Navy scheme, sideXside.

Thanks, Dave R

Thank you for sending out the pic's. That is one sweet bird. The detail is incredible.

Dave R

Per Strommen,

I'm building a Viggen from scratch. It's a little smaller than 1/10 scale at 56" (142 cm) long. I plan on using a Wren MW54 to power it.
Are you using separate ailerons and elevators? I've seen pictures where they seem to work in unison as elevons. The inner portion looks like it works separately when the canards are deflected. I believe that the canards are only used as flaps in that they only deflect down. And lastly, how does in fly?

Thank you in advance,


John

Hi
Leif Poulsen at Overfly has all the moulds Einar made, so this is the only source.
Brgds Thomas

John,
The full-size Viggen was designed with a two-part elevon for possible separate elevator and aileron. After initial test flying the two part were bolted together, and Viggen has since flown with one elevon on each side. If you look closely at good pictures, you can see the joint in the elevon.
The canards are used as flaps for takeoff and landing only. They contribute to the STOL properties of the fighter.
The model flies very well if kept light. High AOA approaches look extremely nice if you have the guts to really slow it down. They require a fair amount of thrust.
Orientation is sometime a problem because the fin has the same shape as the wing, and the camouflage does not help either. Do not let it go too far away.
My 1/10th flew very well on a Ramtec with OS .91 and an empty weight of 5.2 kg (11,5 lbs), and the 1/9th is a rocket with the P-120, weight dry is 8,6 kg (19 lbs).
Tjena, Thomas

Per

Per Strommen,

Thanks for the information.............that explains a lot!. I've got literally hundreds of pictures of the Viggen. Among these I have three pictures from just about the same angle of a AJ-37, Sf-37 and JA-37 on takeoff. The AJ and SF (early versions) show the ailerons deflecting differently than the elevators. On the JA the are in unison............now I know why! I'm building an AJ, but maybe I'll keep it simple and lighter and just use two elevon servos.

Here's another one for you. I've never seen a picture with the speed brakes deployed. The MW54 is probably a little big for my Viggen. In order to combat residual thrust, I plan to use the speed brakes. I'm just curious as to what they look like deployed.

Regards,


John

John,

Not many people have seen the speedbrakes deployed. I do not know if they are welded shut, but a fellow pilot in Sweden told me they were never used. Just pulled a high G turn and the plane would stop. Lots of drag in that double delta at high G!
I have seen speedbrakes on a model once, Hans Blom of Sweden did a superb model for the World Masters in Austria. No pictures here I'm afraid.

Per

John
I just spoke to a colleague of mine and Per S. He´s an x-AJ37 driver. Speed brakes is rarely used during normal operations. Main usage is during formation flying to instantly make small adjustments in your position compared to the leader. Throttle is a slow way to decrease speed since there is a time lag in changing thrust level in a jet engine. By deploying the brakes a small light is lit adjacent to the brake, this to make it possible to see if your leader is slowing down in darkness.
Brgds Thomas

Thomas,
Thanks for setting me straight on the speedbrakes, I actually thought they were inop. Funny with the light, the Viggen must be the only fighter with a stop light showing from 6 o'clock. Helpful for a wingman, but tactical? Must be a swedish invention! :-)

Per

Thanks, guys for all the information. I think that I will utilize the speed brakes to slow the thing down on approach. My Viggen is built as a one piece airframe, so the top speed brakes provide good access to the engine mounting screws as well as the glow plug!

Regards,


John

Cactus Flyer,
You won't need speed brakes just do a tight turn! The induced drag is very significant with this model and a reasonabl;e amount of throttle work is required if you need to do a tight circuit. But you can land on a sixpence at virtually walking pace. The canrds work well for take off and landing. About 10-15 degrees fro take off and max 45 degreees for landing. you will need quite a lot of down elevator compensation with 45 degrees flap and around half throttle in circuit and still 1/3 on finals (depending on powerplant of course). Put the flaps away if you go deadstick.
I had a Jim Fox df sport model for years and it was great fun and very safe.
I have another one built scale which will have a MW54 should be perfect.

JohnMac,

Thanks for the information. My Viggen is a slightly smaller than the Jim Fox airplane. I guess that I will hold off installing the speed brake actuators pending the CG location. If I need tail weight, I'll make them active. Otherwise I'll just use the top speed brakes for access to the glow plug.

My Reaper is HUGE in comparison to my Viggen. With the MW54, I find it hard to slow down, so I'm a little leery of the residual thrust on the smaller Viggen. I guess with the canards extended, one can get a fairly high drag profile established. Additionally, the wing loading is going to be a lot higher which will necessitate more AOA hence, DRAG.................Right?

I've done some testing with a hand-toss model of the Viggen with positionable control surfaces and it seems that the ratio of down elevator to flap is about 4 to 1. That is, 40 degrees of flap needs about 10 degrees of down elevator. Which brings the question: Did you use elevons or separate ailerons and elevators on your Viggen?

Regards,


John

Cactus Flyer,
I used elevons and my new model likewise. It would have been difficult to get thin enough servos in a good position to drive outboard ailerons.
I would say that your elevator to flap mixing ratio is a good starting point.
BTW, if you have a slow function, use it on the canard flaps. They also work as elevators quite well. In fact, for particularly short runways I mixed down flap with up elevator in take off mode. This was as well as some flap set in this mode anyway. It would rotate the model at a ridiculously low speed. The Viggen properly set up would not stall in this condition, just rock its wings a little.
Regards,

john.