30 lbs. . . . .MX-2

[KrisW]

That's the target.

At 4:30 this morning (March 30) I was at the freight terminal picking up my Composite-Arf 40% MX-2. An hour after I got home the landing gear and tail wheel were in place, and I had it hanging from my Wally World Digital fish Scale.

Weight of the complete airframe, including LG and canopy, is 18 lbs 10 ounces. this includes the CF wing tube I bought from Desert Aircraft, Two 4.5" Sullivan Skylite wheels, 10-32 bolt axles, 35% Titanium Tailwheel assembly from RC-Blimpro, and 4 fender washers on the main landing gear legs to spread the load.

A few comments on the MX-2.

First off. . the quality of the molded airframe is EXCELLENT!!! Except for some Peel ply that got stuck to the inside of the motor dome during the layup, this is an absolutely gorgeous aircraft. I ordered mine in All White, instead of the Scale green-blue-white scheme. Yes, the scale scheme is very pretty, but I got a $300 break on the price by going all-white. if I had it to do again, I'd get the Scale scheme. It's just so pretty that not using it is close to a crime.

Secondly, all the control horns are already in place, and the stabilizers are hinged from the factory. The canopy frame is already fitted and bolted to the fuselage for you and everything fits so close that you have to appreciate the extreme attention to detail that makes it possible.

Third, the production MX-2 motor dome is NOT like the one pictured in Mark Trents thread, but resembles the one used in the production Extra's that CA produces. This means that the dome goes all the way to the sides, top and bottom of the fuselage, and the cowl attaches to the motor dome instead of to a cowl ring.

Being used to the 3M and 3.1M Extras, when you pull the MX-2 out of the crate it looks. .. small. Then you get it together and it looks. . not so small, but not big either. Kind of like a cross between a 2.6 and 3M extra (which is the reason I bought it) The shape says 3D and IMAC in the same word, unlike an Extra or YAK that yells out "precision. . precision. . precision". Then, you just gotta love those wing and tail fillets that just looks so. . .sexy!!!

(SIGGGHHHHH)

Okay, time to take pics, then . . "Git 'Er Done!!!!"

Time for another cup of strong coffee, too, this is gonna be one INTENSE and quick buildup .. I want it flying by next Thursday.

Pic #3 shows the BME110 and 2" standoff box. The Falkon ignition is mounted INSIDE the standoff box, ignition battery zip-tied to the roof of the motor dome, and how things align on center.

Pic #2 shows the bottom of the engine installation, with shorty headers that will be attached to PEFA "LL" canisters. The combination of very short headers and the LL canisters actually picks up about 150-200 rpm over in-cowl mufflers, and is a whole lot quieter. Note the attention to keeping the ignition leads away from any exhaust pieces, since heat is any wires biggest enemy.

Pic #1 shows an internal view of the nose of the plane. On the roof of the dome is the ignition batery, a 1650ma 4-cell NiMH pack. Using NiMH gets rid of the complexity of using a regulator, and is no heavier than a 2400ma 2-cell Li-Ion pack and regulator setup. The switch is a Cermark charge-jack switch. Total cost of the ignition power is LESS than the cost of just a li-ion pack, about $35 total. Also notice the routing of the fuel lines and fuel dot setup to keep the lines on the side of the plane, and well above any exhaust pieces that will be inside the fuselage. the slack of the fuel line going to the Fuel Dot is sufficient to let it be pulled 6" from the plane, but short enough to prevent it drooping down and touching the exhaust canister muffler. The tubing will be secured to the side of the plane as it passes back to the wing tube area, to ensure it never gets out of place.

[KrisW]

OH. . did I mention that a BME110 w/canisters is the power for this plane??

Okay . .WHY the BME110??

It's LIGHT. .and powerful. Ifyou want to get a plane lightened up, the best place to start is with the heaviest component, the engine. The total engine package of BME110, Pefa LL canisters, ignition battery and switch, spinner and Mejzlik 28-10 propellor comes out at about 7.5 lbs. compare to a DA150 with in-cowl exhaust deflectors, spinner, prop, and ignition at about 11 lbs, and you realize a 3.5 lbs weight savings.

Okay, everyone is going to scream "But it won't BALANCE!!!!!"

Sure it will. Videos of this plane show me that with a DA150 on the nose, and things like rudder servos and batteries on the CG, the plane appears to be flying very nose heavy. Waterfalls "fly" instead of flipping around, Blenders don't quite flatten out, no matter if you have 50 degrees of elevator throw and a ton of engine thrust on hand, and the nose drops very quickly during low speed 3D flight if the elevator is relaxed for even an instant. This yells at me. . NOSE HEAVY.

So. . not faulting the builders of the planes I've seen in videos. The planes fly great. But how much CG shift would it take to have them flying neutral, or even slightly tail heavy? My guess (and it's only a guess) is that the MX-2 would need the rudder servos at the back of the cockpit area, and the battery packs back there as well, to achieve neutral-tailheavy CG. That's about 1.5 lbs shifted aft in most cases (from cg). Take that same weight, shift it forward, and now you can run a lighter engine. How much lighter is the question, and will I have to add ballast is the other question.

There's only one way to find out. . .isn't there?

[Biff]

Kris,, great thread and thanks for sharing! I've been watching the thread and have some questions. First of all I think it's awesome that modelers are always trying something different. That's one of the things that have kept my interest in the hobby for so long. I salute you Devil Dog for going outside the box !!! Hoorah!

My question is why? I know wing loading and because it's there thing, but throw it in a pot, boil it down and don't you end up with a 30# airplane with a 110 on it? If a company offered a 30# plane specificly for a 100-110 it better be a scaled out war bird, or sales would be dismal.

I've seen 50 pound airplanes TR and pull out with a 150. But isn't gut wrenching power what we're all about? I understand you'll see a 3.5 pound weight savings, but at what cost? I'm of the opinion that 3.5 pound weight reduction isn't worth thrust reduction. I can't quote static thrust difference between a healthy 150 and a good 110, but it would seem enormous.

My last thought is, look at where weight is most critical. TOC, Don Lowe Masters, Tucson Shootout,XFC freestyle. If weight is so super hyper mega critical, why add 3 pounds of smoke? Seems to me I'd go with a 12 oz. gas tank and hope I timed it right!

Dude, understand the last thing I would ever want to do is rain on somebody's creative process! I just want to better understand what you're going for. Light is awesome, but honestly so is thrust and inertia. Seems as though trading 3.5 pounds for such a big difference in thrust and inertia isn't adding up for me.

Fill me in Kris, I know you know my intention is to better understand. I love oblique thought!!

[SleepyC]

Let me add.... new plane, working on it all day on a Thursday?
MAN.... I want that schedule!! Whats the deal Kris?!?!
Can I get this magical schedule!?!

Looking forward to the build!

[GremlinX]

Nice looking aircraft... Very nice.

[KrisW]

No rain here, Biff.

Okay, lets talk pushing the limits. you yourself have stated that the MX-2 with a DA150 on it (not even piped) has a "moonshot vertical". .

WHY? whats the point of all that power if you are running around flying at 2 clicks off idle 90% of the time. It's like driving down the road in a 1000 hP Blown Hemi Chevette. The only thing it's good for is 1/4 mile blasts, and the rest of the time the entire way the vehicle performs is compromised. I'd much rather be driving a near-stock 300zx twin turbo that has been breathed on with 500 hP, yet outperforms the Chevette in EVERY aspect besides acceleration. More comfort, tons better braking, it can TURN, and much better mileage.

Look at it as a "Total Package" concept. IMO Composite Arf actually made a big mistake with the MX-2 by designing it around a 150 instead of changing things just a little bit more and aiming it at the 100-120cc market. By moving the wing aft a mere 3/4" all those little CG nuances would be alleviated, and people would be lining up in droves to slap their DA100's, 3W106's and BME110's in the little monster. The planes handling would be a noticeable step better than current 33-35% offerings, truly cmpetitive IMAC pilots would take a much harder look at it, and the REALITY of a "balanced package" would be more easily realized.

Every ounce of wing loading you can remove, down to a certain amount, is an improvement in how the aircraft will fly. The same holds true for overall structure weight as well. People say that my 29 lbs Extra 330 has to be a real handful in the wind, but it's just not true. Yes, the plane is harder to land in the wind, and may take a bit more effort to track straight in a hard cross wind, but overall flight characteristics when compared to a heavier version of the plane with a 150 on it are GREATLY improved. It snaps sharper, damps out of any wobble faster, is almost impossible to accidentally stall so hard pulls and pushes are actually flown, not aimed through, and flies soooo slow in 3D without a high AOA to keep it flying.

I guess what you could say I am aiming at is the "Ultimate balanced package" of power, manuverability, stability, lack of polar inertia when snapping and doing hard manuvers, and lighter stresses on the airframe, lower fuel consumption, and lower overall cost for better overall performance.

Think ZEN. . balance. . . focus of purpose. . . think Total Package, not just 1/4 mile acceleration times.

All those yahoos ask . .How fast will it go. . how high will it go. . how much does it cost . . .Answers: Who cares. . .who Cares . .A lot less than the other guys.

Think Zen

[SleepyC]

DUDE..... GOOD answer but what about my question!!!

	Quote:
	Let me add.... new plane, working on it all day on a Thursday? MAN.... I want that schedule!! Whats the deal Kris?!?! Can I get this magical schedule!?!

[Biff]

Thanks Kris! Zen and Biff ain't two words that colide in a sentence often! I'm very keen on seeing how this works out. I'm sure it will be a fine airplane. Guess she'll be at the Nall huh? I'd love to have a couple moments at the helm to see what she'a all about. I do agree that as long as the plane keeps going up through a couple snaps there's enough vert. Go for it guy and thanks for sharing your thoughts! Nice buildthread guy!!

[KrisW]

	Quote: Originally Posted by SleepyC
	DUDE..... GOOD answer but what about my question!!!

Oh, well .. I work weekends, so I take off in the middle of the week.

[KrisW]

	Quote: Originally Posted by Biff
	Thanks Kris! Zen and Biff ain't two words that colide in a sentence often! I'm very keen on seeing how this works out. I'm sure it will be a fine airplane. Guess she'll be at the Nall huh? I'd love to have a couple moments at the helm to see what she'a all about. I do agree that as long as the plane keeps going up through a couple snaps there's enough vert. Go for it guy and thanks for sharing your thoughts! Nice buildthread guy!!

Well. .you gotta PROMISE to keep it away from "THE TREE".

One thing I forgot to mention. . it will be MORE than a mere 3.5 lbs difference. Drop 8 ounces for a CF wing tube, another 8 ounces for NO wheel pants, and no such thing as a powerbox.

I'm probably looking at saving 4.5+ lbs compared to a DA150 setup taht uses al the normal "high end" gadgetry.

[Cracky]

Are you planning on painting it or just leave it white to save the weight?

Thank goodness that they don't use lead based paint anymore...could you imagine how much weight that would add???

[Edge 540]

Kris W
I love the avatar. Best on here!