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The Tantrum from Mountain Models

When the Tantrum came out, it helped fill the void in small electric 3D capable planes. With its pattern style looks, large control surfaces, and long tail, the plane has a fairly aggressive look without being hard on the eyes. Since it's release, this plane has managed to carve out a large following. Is this following justified, or is it another mildly aerobatic plane with 3D tattooed all over its image?

Lets find out.



Manufacturer: Mountain Models

Model: Tantrum

Available From: www.mountainmodels.com

Wingspan:  37"

Length: 37"

Wing Area: 370 sq/in

Weight per mfg: 12-13oz (with Li-poly)

Weight as tested: 13.5oz

Wing Loading: 5-6oz sq/ft

CG per mfg: ½-3/4" behind spar

CG as tested: 5/8" behind spar

Power Recommended: GWS EPS300C-D or brushless equivalent

Power Installed: Astro 010 14t with GWS 4.4:1 gearbox

Prop: GWS 12x6SF

Radio Recommended: 5ch computer

Transmitter used: JR XP642 6ch computer

Receiver: Berg-5 DSP

Servos: GWS Picco BB (x4)




* Laser cut interlocking pieces 

* Full Hardware Package (including micro EZ connectors)

* Light foam wheels included

* Detailed instruction manual (Very)

* Canopy included

* Construction is quick and fairly easy




The Kit


The kit arrived in the mail packed to withstand just about any shipping problem I can imagine (short of jumping on it).  It consists of 12 balsa sheets, 2 lite-ply sheets, 2 lengths of music wire, hardware bag, canopy, full size plans, instruction booklet, and other miscellaneous items.  After a brief examination of the kit contents, I was satisfied that there was no damage, and very excited. :) A special mention has to go to the instructions, they are very in-depth, and some spots employ good humor. Those of us who've built a few kits or scratch builds will have a few chuckles.


The Build

Unfortunately, I got so involved in the build, I forgot to take pictures of most of it.

The instructions tell you which parts you're going to need, and this is another place that the instructions shine. There is a diagram of the balsa sheet you need for that part of the build, and the parts used are highlighted, eliminating the search for which parts are on which sheet.


Horizontal and Vertical Stabilizers, Elevator, and Rudder

            The parts of the tail feathers are fully interlocking making it easy to build without pins or other building accessories. The fit is good enough that it doesn't need glue to stay together while carrying it around the house to show the family (airplane noises optional).


Once the structure is together, a drop of thin CA is wicked into each joint. When completed, the leading edge of each elevator and the rudder is beveled to give room for movement.


The kit is designed with a tailskid, which is fine because the rudder has plenty of authority, but I prefer a tail wheel.  So I modified the rudder slightly to accept a wheel.

Main Wing

            I really enjoy the design of the main wing. There's no need for a flat level surface here. The wing halves can be built in your lap and still come out strait. Attention is needed to avoid building 2 left wing halves or vise versa.




            There's not really much to say about the ailerons. They're laid out and glued, then the leading edges are beveled. That's it, and it doesn't take much longer than it took you to read about them.



            The fuse is fairly strait forward. The fuse sides are made up of the same parts, so you don't have to worry about making a left and right.  You'll be instructed to wick some thin CA into some of the bulkhead parts to strengthen them for the pull-pull cables. Don't ignore this step, or your plane may develop some fatal control slop.


She's ready to cover.



Assembly and Finish

            After covering you're ready to install the servos. The Tantrum is designed with a pull-pull control system on the elevator and rudder. This system results in precise control movement. Though pull-pull systems can be a bear to set up, I found that this plane is a natural. Running the cables is easy. I chose to use a different method of connecting the cables to the servos. The kit includes some cotter pins and EZ connectors. I'm sure this system works well, but it didn't feel right to me. I opted to use Kevlar string, running them through the holes in the servo arm, and securing them with a screw.


Not the most exotic of setups, but it works well. EZ connectors and music wire are provided for the ailerons making installation and adjustment very easy.

I was happy when I found out that the wings are bolted together. However, bolting the wings together is very awkward, not something I want to do at the field. So I won't be taking the wings off for transportation.

I do appreciate the battery mount in this plane, it mounts above the rudder and elevator servos. If you have problems with your servos, the battery mount is removable with a single screw. You'll notice in the pic below that my battery mount is in front of the bay. Because of the light power system, and the added weight of the tailwheel, I had to move my battery to the front of the bay to set the CG. After a few flights, I've moved the battery back a bit and the mount is now where it's supposed to be.




And we're done!!




(the trim strips on top of the wings are red)

Below is a link to a video of the 3rd flight of my Tantrum, please save it to your comp before watching (right click and "save as")

Thanks to Flyer351 for hosting.





          Now we get to the meat and taders. It's been very cold here, so  wasn't sure if I'd be able to fly this plane soon. A few hours after completing the plane, I couldn't take it anymore. There was no wind and it was about 10 degrees outside. Ya can't have a new toy and not play with it, can you?

            Taxi tests showed that the tail wheel provides excellent ground handling. Of course these were extended taxi tests because I was very nervous. After a good 10 passes taxiing, I pointed her in to the wind... I mean, she would've been into the wind if there had been any, advanced the throttle slowly, and she left the ground in about 10 feet. Did I say I advanced the throttle very slowly?

            The plane required a few clicks of down elevator and right aileron, and was flying strait and steady. I proceeded to fly circuits getting used to the plane and testing the stall characteristics. The stall is nearly nonexistent on this plane, it slows to a crawl, drops the nose a bit and continues flying. I did encounter something unexpected while flying the circuits, this plane is incredibly docile on low rates. It felt rock solid in the air, and did exactly what I told it to. After 5 minutes or so of doing circuits with a loop and roll thrown in every once in a while, I landed to make sure everything was as it should be.

             The next take-off roll was about 5', I took her up a few mistakes high and flipped over to high rates. Here's where the next unexpected thing happened. The plane was still very stable. I expected it to be so twitchy that it'd be hard to control, but this is not the case.


            Now we get to the question at hand. Is this a capable 3D ship?


            I'm not an ace pilot, but I can answer a very firm YES.

I was able to execute every aerobatic maneuver I know with relative ease. Harriers, hovers, blenders, spins, torque rolls, etc. The only difficulty I had was with knife-edges. It would stay in a knife-edge with no roll or tuck, but would loose altitude. I believe that is caused by not enough speed. The only thing holding the plane back was the pilot. Some of the moves will be

improved by moving the CG back. Flat spins will be flatter, hovering will be more stable, etc. I also have a feeling that they will get smoother as my skills develop.




          I have a few more flights now, and have moved the CG back a bit with each flight. Though it has become more aerobatic with each CG move, the stability hasn't suffered enough to make the plane twitchy and I haven't yet got to the point that I don't feel comfortable with it. Maneuvers have improved and I can still stay on low rates and enjoy a relaxing flight when needed.

I can honestly say that this plane is a joy to fly. Weather you want a relaxing flight, or adrenaline filled spins and tumbles, this plane does both well. The small niche of small electric 3D flyers is now flooded with planes, but this plane doesn't need rarity to be what it is. Its performance does that all on it's own.



Jason Beach


If you have any questions or comments, please let me know at beachernaut@hotmail.com or on www.rcjimsplace.com