Category: Product Commentary

I’ve spent a fair amount of time scouring the forums and am currently up to about page 400 in the 1000+ page discussion of the E-Flite Carbon-Z cub on RC Groups.  If you care to read all about it click here.  Just to be clear, the cub doesn’t necessarily NEED any modification to fly well.  It appears quite capable and fun to fly right out of the box but I’m one to “tweak” a bit on every plane in order to get a bit more out of the plane, increase the fun factor and hopefully the life of the airplane.

Using input from the discussion group and based on my own experience with this model as well as others, here are three areas where I’ve made changes to the airplane so far.

1.  I continue to be disappointed with the paint.  Just normal handling, battery insertion, etc.. has caused 3 or 4 areas of paint flaking off already.  My first step in combating this was to head to the local home improvement store and get computer matched blue and gray, satin, interior house paint samples.  Each is a half pint (probably a lifetime supply barring drying up) and cost is only about $3.  It was suggested to take the two hatches in to have them computer matched… but of course I forgot and left them at home so had to find the pictures in the forum on my smart phone and have them mixed off the numbers on the labels that someone was kind enough to post.  I suggest you do your own computer match instead as that has a better chance of exact matches to the paint on your cub but mine came out excellent… I was lucky.  Using this paint I have already touched up 4 spots on the cub and other than a very small difference in “sheen” I’d say it is an excellent match.  It does take two coats of blue to get the color perfect over bare foam.  Also, it does look bright when you apply it but after drying it is a great match.

2.  Bought and static tested an APC 15×6 E prop which has received some good reviews on line… Static tests indicate that a full charged stock E-Flite 3200 6S 30C pack with the stock 15×5.5 propeller is drawing 59 Amps right off charge.  The cells sag to maybe 20V which equates to about 1200 Watts.  1200 Watts with a sub 9lb airframe equates to ~133 Watts per lb.  For a cub… that is somewhere between high and rocket powered!  In addition, 59 Amps is just under the 60A continuous rating of the speed controller and well under the 75A peak allowed so all is well with this setup.  Static testing of the new APC propeller had it pulling only 54 Amps.  Flight testing and perhaps some static thrust measurements will be interesting.  If the APC can produce as much thrust as the stock setup and use less amps it would prove that it is simply a more efficient airfoil… If it does not produce equal or better power than I may stay with the stock prop for at least a while longer.  Stay tuned on this one.  Propellers are often a quick and easy upgrade and this test so far proves that you cannot use diameter and pitch measurements to compare propellers across brands.  The airfoil design is key and the listed measurements from the manufacturer are to be taken with a grain of salt.

3.  I purchased some DuBro 6″ inflatable tires to replace to stock foam tires.  The stock tires are considered by most to be acceptable for grass fields only.  I don’t even really like them on grass as they seem to have almost zero cushioning capability and the heavy wire landing gear is mounted into foam and plastic which seems like a possible weak spot.  In order to protect that mounting, I am going to try the DuBro wheels with minimal air pressure.  They are almost 3/4 of a pound heavier than stock so I will lose a little power/weight ratio but I can compensate somewhat by keeping to smaller battery packs (folks are running up to 5500 mah packs… so far I’m staying with 3300-3700).

I’m considering quite a few other additions, modifications, updates, etc. that I’ll discuss as I decide on and implement them.  Most likely there will be telemetry installed as well as some personalization of the color scheme, flap/elevator mix testing, and more.

Right now I’m getting prepared to go flying on new years day which is currently being predicted to be a balmy 20-25 degrees(F) and 10-15mph winds…  First to explore is whether I can get the Cub into the trailer fully assembled to avoid freezing fingers having to assemble in the cold!

After waiting for the warmest temps of the day to arrive (while watching my favorite NFL team squeak out another win) I and my buddy Steve headed to the field to get a first flight on the Carbon Z.  We had about an hour of daylight left with temps in the mid 40s and a mild 5-10mph wind mostly down the runway to work with when we got to the flying field.  For early winter in these parts, about as good as it gets.

Assembling the cub in the cool weather was a bit chilling but not overly difficult or time consuming.  If you have to have struts, these aren’t to bad to put in place.  First order of business was to make a short hop to check trim and dynamic balance and overall just get a feel for how the Carbon Z would fly.  The result?  Pretty much as expected.  The big Cub found the sky very quickly before I had gotten much past 1/3rd throttle!  Subsequent takeoffs were found to be possible in about 4 feet… and that is without use of the flaps.

With only a couple clicks of trim, the cub flew nicely.  Using the wing and somewhat less control throw than recommend even for “low” settings in the manual, the cub was immediately discovered to be more capable than any cub I’ve ever flown or even seen flown.  Power was adequate for nearly unlimited 90 degree vertical climbs, continuous knife edge, 20 foot diameter loops, rolls, stall turns, etc…  No problem.  After 3 minutes or so, a nice, gentle main wheels only landing was accomplished.  We quickly then rigged up my friends brand new KA-8 glider and with a very smooth mid-power climb he was hauled up to about 250 feet where he successfully released and began floating around the field.   The cub was brought in for a quick landing so I could watch Steve’s KA-8 floating about and then making a near perfect “spoilers” landing within 20′ of where we stood.  Nice job on the first flight Steve!

After clearing the tow line and moving the glider away, Steve took the Cub up for a quick spin and commented immediately on the ample power and stability of the Carbon Z.  After a few minutes of fun, Steve brought the big bird down for nice landing of his own.

Before the light could totally fail, I took the bird up for one more flight.  First, I climbed up to a safe altitude and tried deploying the flaps.  The resultant pitch up was fairly dramatic, and that was with the lesser of two flap settings I had programmed.  That will require some more research and programming!  Pushing the envelope a bit further I started through the basic IMAC sequence as best I could recall from earlier this year.  The Cub seemed to be doing fine with the maneuvers until the motor started to pulse and it was time to come in for another easy landing.  Altogether, I had been above 10% throttle for about 13 minutes.  Better than I expected for the 3300mah pack, especially in cool weather.

Even though the Cub landed very gently, I do want to get some softer wheels for those times when something slightly more harsh occurs and the flap mix and travel are going to require some more adjustment and testing.  As well, I will be getting some more batteries of somewhat varying size and brand.  I think the cub could easily handle somewhat larger cells and I wouldn’t mind to have a bit more flight time per pack.  With a safety margin, the 3300s would appear to give me a solid 10 minutes of more aggressive or maybe 12 of pure cruising.  I’m guessing this might translate to only 2 or 3 glider tow climbs and in this mode I really would like to have to stretch that to 4 or 5.  Once I have some more batteries in hand I can do some test flights and see what sort of trade off between capacity and weight is possible.

Overall, after one battery (3 short flights) I can already tell the big cub is going to be a lot of fun.  I’m looking forward to getting her out at the next club event (the Freeze Fly on January 1st).  With these bug tundra style tires, even a little snow shouldn’t present a problem.  And if the snow gets deep… the floats are sitting in the box out in the shop.

With cold weather and rain the rule for the first few days after the initial assembly of the CZ Cub I turned to setting up my radio and adding one or two “upgrades”.

First up, I went through and put triple rate control throws and levels of expo on my radio. Also I set up for a stopwatch timer as I am unsure of the flight times I can get from the recommended Eflite 30C 5S 3200mah battery I purchased. From there I setup the flap system with a nice slow 2 second deployment and 20 percent of down elevator throw. Unfortunately with no indication of how much Flap throw is considered normal there is no way to know how much flap or how much elevator mix will be required to offset it. The manual says 42% of elevator but that is hardly helpful with no idea of 42% of what!

Continuing on, I had read some forums that indicated that the paint around the front hatch was prone to damage due to trying to get hands and batteries in and out and that a new battery tray that was laser cut helped with this issue. I decided that this made some sense so I ordered the Morgan Mills RC battery cartridge system and installed it. Assembly was easy once I viewed the assembly video on line about 3 times! If you don’t do that, good luck as there are NO included instructions!! The tray and cartridge seem very nice so far and definitely make getting batteries in and out easier.  This is the part that replaces the plastic tray inside the airplane.

And this is the battery holder that you put the battery in before insertion into the airplane.   I added the small rubber dots you see to keep the pack from sliding even the small bit that is allowed by the tray.  I also used my own double sided industrial strength Velcro instead of the stuff that came in the airplane (it seems a bit weak when you consider how heavy the battery is that your securing).

So far, playing on the bench, it seems to work very nicely and the ability to easily reposition a battery to exactly the same spot every time you put it in the plane is certainly going to help, especially if you plan on running more than one size/weight pack (like I likely will).

The downside of all this is that folks are right on when they say the paint in this area is fragile. In fact, I think it is pitiful… Even being aware of the issue and trying to take great care, I have already lost a fair amount of paint in this area before I’ve even made my first flight. This is very disappointing… I realize this is a foamie but it’s a fairly expensive foamie (not the original cost so much as the total investment) and there’s got to be a better way to get the paint to stick to this foam. It really worries me as to how well the rest of the paint is going to hold up. My investment at this point with battery, receiver, plane, floats, and glider release servos is over $600. I’d like to have this thing look decent for more than the first 2 weeks! I was thinking the overall price on the CZ Cub was pretty nice for this large a plane… foam or not… but I was expecting to keep the paint attached for more than a few days.  Very disappointing even if it is only cosmetic.  Here is a close up shot showing what has already occurred in just a few days.

Next I went to install the glider tow release servo. I love that the CZ Cub has this built in with only a servo needed to make it operational. I have two buddies who would love to have a good tow ship available to get their gliders aloft and this thing could be just the ticket! I wish the instructions were a bit clearer… or maybe just a better diagram but the actual mounting point looks a bit different than the diagram with no direction given as to what type of screw to use to mount the servo… at least E-Flite is consistent! In actual practice I ended up using one screw through the servo mounting hole on the servo and another just overlaps the end of the servo mounting tab and clamps it in place. It seems very strange but seems to work so far.

At this point I am ready to fly and while I am trying to tamp down my expectations I really am expecting some good performance.  The plane only weighs 8.5lbs ready to fly at this point and with the 6S power, flaps and huge wing area it should be a real floater with some excellent power to weight ratio.  Can’t wait to fly!

 

 

I recently purchased a new Carbon-Z Cub, produced by E-Flight and distributed by Horizon Hobby.

  Carbon Z Cub <– Click here for purchasing options via Amazon

After some research, I bought the PNP version because I really didn’t want the AS3X in a plane of this size. I’m a big fan of that technology in the small planes where it can aid immensely. I’ve owned a couple with AS3X and these planes fly well in windy conditions that would completely overwhelm me (and I think most pilots) without it. There are lots of other reasons I went this way (in spite of a very low delta in price) but the two main reasons are that I don’t like the receiver essentially limiting what I can do with my radio (things like end point adjustments, rates and exponential) and maybe most importantly an 84″, 8.5lb Cub probably just doesn’t need it!

So back to the beginning… I got the cub home and started to unpack it. Firstly, it seemed to be very well packed as you can see below…

with only one really noticeable case of shipping rash and no real damage. Here’s the worst of it… the right wingtip.

It’ll probably get worse than this soon… but I can’t help wishing it had come out entirely pristine!  Oh well, it’s probably to much to ask that an airplane made of the same materials that it is packed in is going to come out of the box perfect.  Actually this is pretty minor compared to the rash many planes come out of the box with.

After laying it all out on a large table (the plane is big). I started assembly and immediately ran into two of the issues that I have heard mentioned before. First, the included wheels are made of some sort of very dense foam and while lite… are very, very hard. It is an effort to even dent them by gripping them and trying to crush them by hand. Combined with the landing gear mounting in foam and hard plastic and this leads to a concern about how well the landing gear will hold up in the long run, especially whether the foam will crush or the plastic crack under the stress. The wheels sure aren’t going to cushion anything!  I’ll have to consider finding some wheels with a bit more bounce.

Next there was an issue trying to find the right screws to mount the gear and this issue continued throughout the assembly of this ARF. This has apparently been an issue since day one and even the addition of single sheet “fastener guide” didn’t do enough (at least for me) to sort out the issue. It’s kind of funny when you realize that this has been overcome quite effectively by many ARF manufacturers in the past using a variety of methods but somehow E-Flite couldn’t figure out a simple way to label the various parts and call them out for easy identification.  Adding to the confusion is the fact that extra hardware is included in the kit… normally a very good thing, but in this case… adding to the confusion. Eventually I figured it all out… I think.

As the assembly progressed I ran into another issue where the instructions could have been improved. Keeping in mind that you are working with a largely foam and plastic (and very large) airplane, it might be nice to mention just how tightly some of these fasteners should be. For instance, in a later step you attach the wing with a couple of bolts but if you tighten these down to much… foam starts to crush. It doesn’t take as much force as you might think, so be cautious not to over tighten!! It IS a big plane, but it’s still a foamie!

One more assembly item came up when I was mounting the motor. There is a lot of wire between the motor and the speed controller and no mention of what to do with it all in the instructions. This is important because the motor is an outrunner and you do NOT want the wires to abrade against the motor casing. I did not like the idea of stuffing the wires back around what might become a rather hot speed control… hot metal and wires don’t mix, nor did I want to block airflow. So, I wrapped the wires inside the cowl and secured them with some clear silicone calk… Here is what that looks like…

Hopefully this works out well.  I’ll try to keep an eye on them.

In spite of all of the above, it only took around 2 hours to complete assembly of the big Cub and depending on how the landing gear survives, it looks like the result is a fairly well built and finished airplane. I’m really looking forward to getting a warm day to see how it flies! This is by far the largest electric I’ve ever owned and I’m looking forward to trying to trade some “electrons for altitude”!

One final assembly and initial setup note… I was surprised to see that no actual control deflection measurement are specified in the manual! To me this is clearly unacceptable. I realize that for those who purchase the BNF version, these are not needed and I’m happy to see what appears to be fairly complete instructions for those folks but what model does NOT specify control throws?? Usually for at least two “rates”.

All in all, so far I have mixed feelings about the Carbon-Z Cub.  At first, it seems like a fairly big investment for a foamie and there are a couple of small assembly issues, but… It does seem to be fairly well built and with this size wing, the option for glider tow, floats, full flaps and the chance to break into a truly large electric…   I think the value is pretty good.  Of course flying is the real goal so I’ll withhold judgement for a bit longer.

Right now I’m fairly happy with what I’m seeing and I’m looking forward to see how it performs in the air.