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Sunday, August 26, 2012

First Look__Extreme Flight 60" MXS

Everyone has been chomping at the bit for this airplane almost from the day that the 48" MXS EXP was released on the modelling public. The 48" is such a bad ass little machine that a larger version would be very much like the 60" Extra EXP..... more of a good thing, and it certainly is.

The MXS has always been a very special plane for me. The wild pitch authority plays itself perfectly into my flying style, and aside from that, it is pretty much like an Extra EXP, which has become my favorite for all around flying. The MXS is for those days I want to hang in right on the edge the whole time, and now we're getting to do it in a bigger size.

New Stuff
There has been a lot of talk about the new construction, and there is even more new stuff on the big MXS. Some people are lamenting the loss of all the carbon and G10 composite that we have been seeing on the original three 48"EXP models (Extra, Edge, MXS), but that was then, and as we have seen on the 48"  Laser EXP, the newer construction is the way forward.

While some of the composite has been eliminated, it has still been retained when a better way couldn't be found. There is still a big block of G10 composite for the landing gear mount. Instead of carbon tubes, the MXS has always had the bottom corners of the fuselage sheeted. Chris Hinson tells me that "Honestly it wasn't a cost issue regarding the carbon tubes. The sheeting on the botton corners of the fuselage adheres so much better to balsa and was plenty strong and rigid. The carbon tubes will be in the 60" Laser as there is no sheeting on the bottom corners of the fuse."

I have no doubt the sheeting makes for a stout assembly. You could almost play baseball with the 48" MXS fueslage, so I have no worries the big one will be just as rugged.  Certainly the engineering in the original EXPs was awesome, but Extreme Flight is always raising their game and forcing the industry to follow suit.

I do sort of miss all the composites from a bling point of view, but from an engineering standpoint things like the angled motor box sides makes for a stronger airframe that is less complicated. The composites were certainly functional enough, and great fun to show off, but this is probably a better way. It also keeps the airframes costing less money than the competition's.

Let's start at the front and work back.

Motor box
Gone are the carbon rods used to brace the motor box on the 48" planes. The carbon rods were put in the older planes to stiffen the motor box from the front side, and keep the motor box sides out of the battery area, allowing much more room for changing out the pack.

Instead, now the sides of the motor box now extend deep into the battery tray which has the effect of stiffening the entire motor box from behind. You might think that now the motor box sides are again interfering with battery change out, but instead, the sides are angled away from each other, making the box wider as it goes back. by the time the sides reach the battery compartment, they are well out of the way.

Also note that there is triangle shaped wood stock where the sides, top and bottom of the motor box meet. This arrangement is so strong, and there is so much surface area that is glued that I did not bother to go over it with CA. Normally that's asking for trouble, but the motor box on this thing is so stout that I am not worried.

Recessed Wings.
This is a technique that I personally first saw on one of my smaller Brand X Yaks 54s, and later on a lot of giant scale models. I am sure there are advantages I don't know about, but two of them stand out pretty clearly.

First, the wing recesses into the fuselage, and any imperfections in how the wing matches up to the fuselage now disappear into that recess.

 Secondly, the wing retention bolts are now facing upwards so you can get to them with an allen driver. If you don't have arthritis, you can't truly appreciate how much easier this is on your hands than it was twisting the nylon bolt at a weird angle for 10 minutes. This is much, much easier on my old hands.

While we are looking at the wing attachments, there's even more improvement. Now the formerly fiberglass tube in the fuselage that supports the carbon wing tube is made of thick plastic, and so are the tubes inside wings.

At first I am thinking "What the heck is this?" Then I realize thick plastic will compress a lot less over time than thin fiberglass and the wings will stay tighter longer. I also believe the thin fiberglass was useless for adding strength, but the plastic tubes will probably also give the fuselage much more torsional rigid in that area, and we all know a tighter, more rigid airframe flies more precisely and lasts longer.

That, and Chris and the factory keep finding new ways to make these planes tougher and tougher.

Radio Compartment
I'm still a big fan of the old radio layout, but I am learning to appreciate  the new one. Checking out how things are done, I figured out that the receiver is supposed to go on the tray behind the wing tube where the wing bolts go in. The tray isn't quite long enough for my Futaba receiver, so I used a piece of scrap wood from another project and glued that on. By running the servo leads through the holes thoughtfully provided in the formers, the wires lead right up to the receiver, and they are also kept from falling out the bottom of the plane through the cooling slot.

Ball Links And Such
I really like the ball links provided on the 60" planes. On the 48" you have to be very careful not to over tighten the retaining bolts or that will create friction and drag. You don't want a draggy ball link.

These ball links still operate freely and smoothly well after you have socked them down hard. I use Dubro case hardened allen bolts on all my planes simply because I like them and how they look. I also get 2mm lock nuts from Micro Fasteners. After I tighten the lock nut down real good, I check for smooth operation, and then use a standard hex nut on top of the locking nut and turn them together, a technique called jam nutting. That alone assures nothing is going to come loose in anything short of a nuclear holocaust, but being the paranoid type I put some thick CA on the exposed threads anyway.

Control Set Up
There's not much here except to provide the clearest photos I can of how it all goes together. The pushrods thread deep into the ball links so there is almost no danger they could ever pull out. I used a drill to run the pushrod into the ball link that I would attach to the control horn. Then after attaching the servo arm to the other ball link it was easy to use the arm as leverage for twisiting that link on. The worse my arthritis gets the more I have to pay attention to things like this. I simply can't grip things like I used to.

Having has so much success with  Hi Tec 5265MG  digital servos in our 60" Extra EXP, there was never a question of going with anything else on this plane. The plane came set up for them, so the servos simply dropped right in, just like they did on our Extra.

One thing I found on these servos is that you need to check the dead band to get the best performance out of them.  Generally speaking, the lower you set your dead band the better centering the servo will have. On the Extra, setting the dead bands turned it into a completely different and much more locked in airplane. For the MXS, I wanted to take care of that right away, and I had the right tool for it too.

For this you can go as inexpensive as an HPP21PC servo programmer (About $25), but I wanted something I could use at the field and went with the  HFP-25 Digital Servo Programmer & Tester.

This is a nice little unit, but at least initially I was pretty intimidated by all the features and optional settings. If there is something you can adjust in the programming of these servos, this takes care of it. You can also set your end points and test servos, so clearly this is a great tool that I have needed for awhile. I just have to make the time to learn to use it better.

 So far all I have learned to do with it has been to reset the programming on the servo, and then set the deadbands. The instructions are pretty comprehensive, but all the heli guys at my field know the unit forwards and backwards, so I have access to good help. It can't be too hard, but I haven't had the time so far to sit down with the unit and play with it.

A nice bonus is that the same Durbo long heavy duty servo arms that fit the HS225MG servos also fit these. I have got a lot of those left over from my Ultra Stick 25E days, so it was nice not to have to buy more.

Aileron Set Up
Just like the on the 60" Extra EXP, there's not much here. You just screw the ball links all the way on and you might have to back it off a turn or two. I like it that way because the pushrod threads deep into the ball link and that's a lot of threads holding things together.

I don't mean to make it sound like a bad thing that this set up is so simple. It's actually a damm good thing because complicated things tend to unravel in the air at the worst times. I like simple a lot and strive to keep my planes that way.

Simple, that is.

Elevator Set Up
More simple stuff here too. Again, the ball links are threaded deep onto the pushrods. They are very nearly bottomed out and maybe backed off two or three turns. I think it is remarkable these planes are engineered this closely and mass produced to this lind of tolerance.
Rudder Set Up
Again, simple and elegant. Not much to put together, not much to maintain or adjust and nothing to fail.
Awesome Wing Tips
The wingtips still blow me away. They aren't fiberglas or plastic and painted. No. It doesn't get any more delux that these. They are built out of balsa with ribs and sheeting, and even the holes for the bolts that secure them to the wing have plastic guide tubes. After all of that, they are covered with Ultrakote by hand! That's a staggering amount of labor. It would probably take me at least an hour to cover one of them, and even then it wouldn't be half as nice.


Those could have much more easily and less expensively been made out of fiberglass, like on the 48", or even plastic, and no one would have noticed or complained. This is how you can always tell a quality product. The effort and craftsmanship goes into places you would not normally look. They all look pretty on the outside, but the deeper you look into an Extreme Flight plane, the better it gets.

The Build
The only little snag I hit was once I got the cowling on, and removed the canopy, it was too tight to slide the front of the canopy back under the cowling. I went too far out of my way to get a snug fit and succeeded.

I plugged the holes (using toothpicks and CA) that I driled in the fuse for the screws on one side, and put the canopy back on with two strips of tape out the outside where the cowl rests on it. Then I redrilled through the holes already in the cowl. After removing the tape the cowl now sits a tiny bit higher and that is enough to allow the canopy to slide in much easier. This is an old trick I used on a different brand, but forgot it because the 48" EXPs cowlings don't overlap the canopy like it does on this plane. My 60" Extra is the same way, but Jim built that plane.

This time I did the build a little differently. I did all the little grunt work first, like filing the flat spot on the tail wheel wire and assembling that, threading the ball links onto the push rods, putting the motor hardware on, gluing all the hinges into the control surfaces, heat shrinking the servo extensions, and installing the control horns. This was tedious, because I really just wanted to get my hands on the plane, but it helped when it came time to do the actual airframe assembly. Once the tail was on and hinging was done, everything else just bolted on and the rest of the build was a breeze.

I can't do a nail yet because I haven't flown the plane, but so far it's been a really rewarding project. The nicer an ARF goes together, the better the whole experience is, and we're off to a great start with this plane.
Outside of the little mistake I made mounting the cowling (which was my own fault) it was a perfect build. Some of this I attribute to having built so many EXPs and having learned a few tricks, but mostly I would have never gotten this far if I had not been building from such premo stuff. I would have gotten fed up and quit long ago if I had to work stuff that didn't go together or had to be rebuilt to make it work. This plane almost literally fell together by itself. 

On the whole, the build was a really gratifying experience. Everything fit real nice and the only surprise was that it came out much nicer looking that I was expecting.

Battery Placement
Since we haven't flown it yet, this is sort of my best gusstimate for where the battery will end up. This puts the CG right on the front of the wing tube, but I usually like them right in the middle. I've been liking the big Extra with the CG a little more aft than what I like on the 48" models, swo I am guessing this will be sort of the same thing. As always, start off nose heavy and work backm not the other way around.  Where I am starting will be very close, but still a little forward.

EDIT: On my fourth flight with this plane I moved the battery all the way back to the wing tube, and the balance seemed very good. I might put 1/2 ounce in the tail (bolted to the tailwheel bracket maybe) next time out just so I can see where tailheavy is and then back it off a hair. Right now it is very close. It might be perfect, but to find the limit you have to exceed it a little and then come back.

These are the same Thunder Power 6s 3850 65C Pro Power packs I have been running in my 60" Extra EXP. I did extensive destruction testing on a prototype 4016/500, so these pack have been ridden really hard. I never low them low, however, and they are still flat while fully charging and kicking back their full capacity. I still have to run one lower than 22.50, and I think that's what's kept them in good shape will still running the crap out of them.



  1. Nice job on this. Can't wait to get mine...

  2. Thanks Doc. Very helpful. Perhaps one on the 60" Laser?

  3. Eventually. It was a very expensive year for a lot of reasons, and right now I just can't do it.

    1. I totally agree and am sorry to hear that. I hope you are REALLY excited!