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        Build Log Depron Ziroli Viggen

#1 flyingfitz737 Dec 30, 2011 09:54 PM

Depron Ziroli Viggen
Hello All,

I am building a lightweight Saab Viggen from a set of Nick Ziroli plans I have had since the mid 1980's. Target weight is 1 pounds with retracts and a lightweight glass finish. Hopefully the light wing loading (7-10 oz/sq ft), will allow flight characteristics suitable for flight in a large indoor venue. I would like to have the Viggen finished for this year's E-Fest.

The model will be made mostly of Depron and sized 1:1 off the original plans. The only wood will be the balsa sticks in the wing, the mounting plates for the GWS retracts, and the ply motor mount. Sides, formers, ribs, canard and vertical tail will be 6mm. Wing sheet and ducting will be 2mm. The forward fuse section will be made of 3mm. The nose block will be carved from white foam. The whole plane will be finished with oz glass cloth and either Minwax Poly or Zpoxy. The glass finish is actually the reason the Viggen project got started. I needed a relatively simple project to experiment with glassing Depron. This will help pave the way for a much bigger project down the road.

Power will be from a 1350 MAh, 3 cell LiPo battery, 35 amp speed control and a 3400 KV Medusa Motor driving a ducted 4 in APC prop. GWS retracts will have two wheels on each main gear truck like the real Viggen. Control surfaces will include elevons, rudder, and flaps on the foreplane. Too many GWS Naro servos will provide control movement.

So far this has proven to be a great project. The airframe would have already been completed, but after seeing how cool it was going to be it just couldn't live without the retracts! Flap mixing on the canards was another thing it had to have. All this has added more complexity more servos and more weight. I haven't built in a long time and never with Depron. I am sure this will be a great learning experience.

Will update with progress and pics. Hopefully this will keep me motivated and give all on this forum something to smile about!


#2 flyingfitz737 Dec 30, 2011 10:00 PM

1 Attachment(s)
Attachment 4517873

A pic of the initial frame-up.

#3 flyingfitz737 Dec 30, 2011 10:06 PM

1 Attachment(s)
Attachment 4517882

A little more progress. I copied my original set of Ziroli plans so I would have a set for the templates.

#4 Ed Waldrep Dec 31, 2011 02:35 PM

A couple of thoughts:
1. Usually an edf unit should be mounted farther back than a glow fan would because you usually have the battery in the nose which wasn't accounted for on the original glow setup. The fan should be moved further back to compensate. However, your 1300 mah battery is pretty light so it's probably not a big deal.
2. If the 4" prop thing doesn't work, hobbyking sells a 90mm fan (3.5") that has a 28mm motor housing, and the pitch isn't excessive so you don't need a lot of watts to spin it...it's more towards a ducted prop than a normal fan. It's kind alike a big kyosho fan. I don't know if the adapters are straight now, the first ones I got were drilled crooked.

Using this 90mm fan limits the amount of power you can pump into the system due to the 28mm motor size. A more normal 90mm fan like the Wemotec Midifan lets you use a 37mm motor and thus a lot more power. It seems for such a big airframe you aren't using much power and are looking for a floater (based on your 1.5 pound all up weight).

Good luck!

#5 space 1 Jan 01, 2012 03:04 PM

3400 KV Medusa Motor driving a ducted 4 in APC prop. whould like to see this

#6 St. Martin Jan 01, 2012 05:17 PM

This was the best flyer, out of the 3 Ziroli designed for the Kress RK-720 and 740. Even with the heavy IC construction, it flew very tight.


#7 flyingfitz737 Jan 01, 2012 08:50 PM

space 1

Not sure it is going to work but it blows lots of air when on the front of the speed 400 machine!

#8 flyingfitz737 Jan 01, 2012 08:55 PM

Worked on the Viggen today. Progress was not as fast as I would have liked. Got the main retracts in, the wings skinned and the motor mount made. The motor mount and the layout of the retract servo really kicked my butt. When I went with 6mm depron on the sides it changed the geometry of the top a little bit. Spent too much time scratching my head and not enough time with the glue!

#9 flyingfitz737 Jan 02, 2012 12:39 AM

1 Attachment(s)
Attachment 4522507

Today's Progress.

Tomorrow I will try and glass the wing so it won't get damaged. Inner duct, decking and vertical tail will follow soon after. The nose section and nose gear retract will be last. Retracts were an afterthought and now I am paying the price!

#10 LuvEvolution7 Jan 02, 2012 03:49 PM

gotta love any Viggen build. deffinitely subbed. :)


#11 flyingfitz737 Jan 03, 2012 08:23 AM

Bottom inside duct installed and wing/lower fuse glassed with two coats of Minwax Poly. The glass finish is a little heavier and the Poly a little softer than I thought it would be. Maybe should have used Zpoxy??? The final coat of Minwax will go on when the rest of the fuse is caught up. Going for the upper deck today if I get time.

#12 flyingfitz737 Jan 03, 2012 03:26 PM

2 Attachment(s)
Attachment 4526267

Attachment 4526279

I like the idea of the 90mm Hobbyking fan. But it would go faster with this 1500 watt version!

#13 Janusz Jawien Jan 04, 2012 02:42 PM

Make sure that those inside ducts will not collapse even under low power that you planning to use. Ups....is it a cheating hole on the bottom of the fuse?
I just saw it....
Anyway, very cool project !


#14 flyingfitz737 Jan 04, 2012 03:41 PM

The cheater hole as depicted on the plans. Hopefully it will help with the slow speed, higher alpha stuff if it has enough power to do that!

#15 Janusz Jawien Jan 04, 2012 03:48 PM

Yeh, I see.... plust those scale intakes are much to small ....
I like the sugestion by Ed in post #4 ....IMHO this light fan is a way to go....

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