IAR-99 SOIM (hawk) for 90mm EDF


Building Fool-Flying Noob
90mm EDF, 80A ESC and 3000 6S battery with no plane.
Looked around, the diamond looks appealing. but I thought about what else... and decided to design the Romanian Air Force IAR-9 SOIM (hawk)


Plane Specs:
from the Wiki Page:
General characteristics
  • Crew: 2
  • Length: 11.01 m (36 ft 1 in)
  • Wingspan: 9.85 m (32 ft 4 in)
  • Height: 3.9 m (12 ft 10 in)
  • Wing area: 18.71 m2 (201.4 sq ft)
  • Aspect ratio: 5.2
  • Airfoil: NACA 641A-214 (modified)
  • Empty weight: 3,200 kg (7,055 lb) equipped
  • Max takeoff weight: 4,400 kg (9,700 lb) Trainer; 5,560 kg (12,260 lb) Ground attack
  • Fuel capacity: Internal:1,370 l (360 US gal; 300 imp gal); External:up to 450 l (120 US gal; 99 imp gal) (in 225 l (59 US gal; 49 imp gal) drop tanks)
  • Powerplant: 1 × Turbomecanica/Rolls-Royce Viper Mk632-41M turbojet, 17.79 kN (4,000 lbf) thrust
  • Maximum speed: 865 km/h (537 mph; 467 kn) trainer, clean
  • Maximum speed: Mach 0.76
  • Range: 1,100 km (684 mi; 594 nmi) Trainer with internal fuel; Ground attack with internal fuel 967 km (601 mi; 522 nmi)
  • Combat range: 345 km (214 mi; 186 nmi) hi-lo-hi at 5,280 kg (11,640 lb)all-up weight
  • Service ceiling: 12,900 m (42,300 ft)
  • g limits: +7 / -3.6
  • Rate of climb: 35 m/s (6,900 ft/min) at Sea level
  • Wing loading: 235.2 kg/m2 (48.2 lb/sq ft) Trainer; 297.2 kg/m2 (60.9 lb/sq ft) Ground attack
  • Thrust/weight: 247.5 kg/kN (2.42 lb/lbfst) Trainer;312.7 kg/kN (3.06 lb/lbfst) Ground attack

Build Specs:

Alpha Set 90mm EDF IAR-99
1 of 4, 2 of 4, 3 of 4, 4 of 4

Come build with me...


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  • IAR-99 Model 1of4.pdf
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Building Fool-Flying Noob
I managed to cut this out and start building.
I feel I made some Good Headway. Here are the progress photos.
I had to adjust the rear fuslage sides and top to adjust for the angle of the bottom. I trimmed 3/8" (2 thicknesses.)

IMG_20181012_003025912.jpg rolled over to see if it lines up. wing cut and ready? IMG_20181012_012014866.jpg
Nope, I need more Cowbell, well higher spar at least;

Now I've glued the fuse up and tested to fit the EDF. As designed I will be cutting groves for the lip. so far working great. the nose seems like it will come together nicely. (held off for now.)

Got the wing folded over, and wanted to look at a photo before I add the tiny dihedral that is present. I didn't want to add too much.

Lay-up mock-up, yup. the vision is coming together.

So FAR, i am pleased. I'm worried about the size of the wing vs. weight/size of the plane... now to work out the details. :devilish:

Out you devil! :)


Building Fool-Flying Noob

the dihedral is like 3-4°
3 sheets of foam board on each wingtip. That will do for now.


Building Fool-Flying Noob
I'm been excited and anxious about the canopy. I want to do a foam one, for now, then use this as template for overhead or reflective mylar.
I designed one up and tried it out. I also put together the undercarriage part. What's that called?
Here's some pics, I'm very happy how they turned out. See for yourself.
IMG_20181025_012003166.jpg IMG_20181025_012020347.jpg

This is my first real attempt at 100% pre-designed curvy stuff. It did need a tiny of trimming to fit flat. 😀


Elite member
Looks really great! 90mm EDF on 6S? That's a lot of power.

You said you were a little worried about the weight versus the wing size - what do you think your final all up weight will be?


Building Fool-Flying Noob
Lets see....
600g 6S 4.2Ah Battery + 310g motor + 82g esc + 6g receiver + 4 MG servos - 50g + 4 sheets of FB and glue - 340g = ~1.4 KG? with 2.6 to 2.8g+ of thrust...
I know the ratios are fine, It's a small thin wingfoil. I'm used to Flite test style, which makes me worry about how much lift I'm going to get on those wings.


I know nothing!
Just chiming in to say I think it is looking really cool! I've said it on this forum before, and I'll say it again: I can't wait to see that thing in air!


Building Fool-Flying Noob
I have glued the canopy down to a base (note to self:add canopy base to drawing set) and the rest of the turtle deck. I also cut the wing profile out of the bottom...
1554442076328401336829.jpg 1554442108518140469761.jpg
and for the tail assembly to the turtledeck and maintain a motor access hatch.
It's looking promising to me.

I want to add retracts. Let me fly this first.
I have to spend some quality time with the air intakes and an iron to the wing edges.

Stiffen here, mould there. Pretty soon you have an airplane.

I plan to do the canopy like the viggen battery hatch. And latch it with a magnet or two
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Building Fool-Flying Noob
Just chiming in to say I think it is looking really cool! I've said it on this forum before, and I'll say it again: I can't wait to see that thing in air!
Thank you @buzzbomb. I'm working on the "finish what you start" new-years resolution.


Building Fool-Flying Noob
Besides the mass amount of projects I've taken on, this project had stalled because of Building a swap-able/removable edf pod. (I have other jet's l'd like to see go.) Nothing really made sense... so I wait. it should be easy-ish. build a box around the edf. and then frame-out the box in the plane to just drop it in. A seal and magnets and I'm in the air like a Silvaire.
:rolleyes: sorry.
Point is I/we should be able to figure something fool-proof, and scale-able. Something like the power pods that we can design the planes around. like 30mm could be a 1.2x1.2x1" box. 50" 2x2x1.5 and 70 2.5x2.5x2 etc...Dunno. I have been letting my mind percolate on it... and it has failed me. Mayhap it's time to put it back to the forefront. I think more folks would jump into EDFs if you could swap them between 3-4 jets in the fleet.

like a 70mm between the Viggen, X-29, a large L-39 Albatross and a smaller version of this guy.


Building Fool-Flying Noob
I did some work on the IAR 99 almost there!:D.
The bod piece is I finished the duct top and bottom.

IMG_20200725_005001618.jpg IMG_20200725_005035794.jpg
with That done, it's time for electronics. IMG_20200727_024137987.jpg IMG_20200727_024118483.jpg IMG_20200727_024219400.jpg IMG_20200727_024211020.jpg

Time to connect the batt tomorrow and fire her up.


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Legendary member
nice build. My biggest "worry" is the intake...if big enough openings to get air to EDF, possible you need some cheater holes. Have you calculated it?

About swapable... make edf unit with thrust tube, make lower half of fuselage rear (the length of edf/thrust tube unit) be easy possible take away (magnets eg.) So when you take away the "rear belly", a couple screws/ u- clamp hold the EDF/thrust tube unit .