CMP EP Katana SR
 

Hi, I just ordered one of these for my first sport flyer- http://www.nitroplanes.com/cmp-ep-katana-sr.html

According to reviews that I could find, it will need a few upgrades to be capable of "true 3D", (stuff like longer servo horns, better hinges and a bigger engine and prop) but since I'm a fairly new pilot, I dont think that will be a problem.

Just wondering though, does anyone have this plane already and if so, what advice could you give on the assembly proccess? also what is your opinion of its performance? thanks!

<br type="_moz" />

RE: CMP EP Katana SR
 

Bare in mind that the recommended upgrades are only needed if you want to extend the flight envelope of this plane.

The stock setup actually performs VERY well.

The long horns on the rudder ( that is the only place you really need them ) are suggested because "Eric" the NP reviewer was flying the plane with the default low pitch prop and the lowest voltage pack it will fly with.

So that makes the plane fly relatively slowly even at full throttle, and it therefore has low rudder authority for knife edges.

What HE should have done is swapped out the included 13x4 pitch prop for a 13x6, as he was running the 4S pack... OR he could have moved up to a 5S pack and left the default prop in place.... he didn't adjust for the difference in performance between the two packs.

That said for 3D it's nice to get as much rudder throws as possible... but this is not something you'll need to worry about into you're well into torque rolls and translating that into a knife edge...

So your only real choice is what pack to use.

I'm flying mine with 4S 4000mAh packs since I have plenty of them, with a 13x6E APC prop. This is a very good combination. I may also try a 14" diameter prop for more vertical performance.

However a 14" prop with the 5S pack will burn out the motor unless the pitch is very low to compensate for the extra diameter.

Choose what type of pack you are going to use with the plane, and let that dictate the prop diameter & pitch.

Otherwise the build is very straight forward and simple. Most of the work has been done for you.

Do remove the cowl & tighten down the screws holding the motor in place, but don't overtighten them.

A bit of tri stock around the gear mounts will help reinforce that area. Remember that you use Tri-stock to help DISTRIBUTE torsional forces out further, thereby providing more strength and resistance to ripping out the wood holding the landing gear in place. I also hardened the wood with thin CA after installing the Tri-stock.

Double and tripple check all of the arms, etc. and make sure that with the stick centered all of the surfaces are set neutral/centered.

And ideally have someone more experienced maiden the plane for you.

It's a pretty sweet flying and IMHO and good buy for what you are getting.

RE: CMP EP Katana SR
 

Yeah I was wondering about the stock prop as I have a bunch of 5S 3300mah that i'd like to use on this plane. But then at 1.1lbs pre batt, I'm a bit worried about the weight of the 5S. ???

If the weight isnt too much then I'll stick with the stock 13x4 with the 5S, and maybe put a larger ESC in it, as recommended.

Also, I'm not exactly clear on what triangle stock is.


As far as the maiden is concerened, I'm not too worried because I've got many flights on my 72" Cub and a couple on my Cessna 182 now. I also have many hours on my rc helis so I think I'll be ok with the Katana, unless theres something weird about the flight characteristics that would throw me way off. ???

Thanks for your input!<br type="_moz" />

RE: CMP EP Katana SR
 

With this size of a plane? It will not notice 3300mAh packs..

I've flown it with 5000mAh packs w/o problems.

If you stick with a stock prop or even move up to 13x6 for a bit more speed, there is NO need to swap out the ESC.

If you ever do swap out the ESC, the only reason to do so is to permit a higher current draw.... and to do that safely you'll also need to put in a bigger and heavier motor too.

Don't bother... you can safely increase the pitch of the prop for more speed or even switch to a 14x4e prop ( if available )...

The motor and ESC will handle both.

The problem with the reviews are that people are putting on overly large props with no thought to the amount of current draw this produces.

See my "dumb, dumb, dumb" comments there!


Triangular shaped hardwood "stock" for hobbiest, available close to the Balsa displays at your hobby store.

Eh, Whose Cessna are you flying?

If it is a foamy, then no don't assume you are "OK"... this is a different ballgame!

If your Cessna is a larger balsa plane, then I'd get help for at least the first flight...

I suspect you'll acclimate within a flight or two, but you'll be facing things you are currently inexperienced with and could result in the crash of your plane.

Better to have someone else maiden it for you and hopefully buddy box the first time out.

RE: CMP EP Katana SR
 

[/quote]

If you stick with a stock prop or even move up to 13x6 for a bit more speed, there is NO need to swap out the ESC.

If you ever do swap out the ESC, the only reason to do so is to permit a higher current draw.... and to do that safely you'll also need to put in a bigger and heavier motor too.

Don't bother... you can safely increase the pitch of the prop for more speed or even switch to a 14x4e prop ( if available )...

The motor and ESC will handle both.

The problem with the reviews are that people are putting on overly large props with no thought to the amount of current draw this produces.

See my "dumb, dumb, dumb" comments there!



So are you saying its ok to run the 5S with the stock motor and esc AND go to a bigger prop? If so, that would be great but I dont think I'm gonna hit the limits of performance anytime soon.

BTW my 182 is a CMP 82"wingspan with a fiberglass fuse with balsa wings. I was brave/dumb enough to maiden it myself with only limited experience with my Cub, which went fairly well aside from the bouncy landings. To my suprize it flies pretty fast, faster than my Cub, but I did ok and I plan to fly it again when I find a larger and smoother landing strip.

Thanks!




<br type="_moz" />

RE: CMP EP Katana SR
 

You can take the prop up to say a 14x4e or a 14x5e.

From what I'm seeing in the current draw, this -SHOULD- be safe, but some of the guys have tried 14x8 and immediately blown the motor and ESC., so at this level you are right on the edge and should watch your throttle management.... e.g. hardly ever using full throttle.

However a 13" prop of 4-6 pitch is well under the max draw currents for both the ESC and the motor, even with a 5S pack.


You may do fine with the CMP Katana EP then.

It will land slowly, but you should fly it to the ground under low power much like the Cessna, then chop the throttle when the plane is low enough to sustain a "fall" to the ground on stall.

The Katana/Funtana's will keep flying to the point of stall, then just drop straight down.

You just want that to happen inches above the ground.

Also if you are flying off grass, put in larger wheels than those provided...

RE: CMP EP Katana SR
 

Igot my new Katana today, yay! I'm setting her up now and so far it seems like a good little plane.

Ihave a question though- how do I wire the dual elev servos on my dx7/ar7000? does the second elev servo go to aux, gear or what? Or could I use an AR500 and use a Y harness on elev?

RE: CMP EP Katana SR
 

If you use a standard Y cables the servos will then travel in opposite directions... to fix this you could set up opposite horn linkages.

Or you could set up the linkages identically and use a programmable mix on your TX, or a servo reverser.

RE: CMP EP Katana SR
 

Ok so heres what I ended up with:
(DX7/AR7000)
R aile on "Aile"
L aile on "Aux 1"
R elev on "Elev"
L elev on "Aux 2"

Using mix 5 and slaving the second elev servo on aux 2.

everything goes in the right directions and seems to work ok, but there is something odd happening with the aile; when I apply full aileron (R or L) the one going up will top out before the one going down. it does this in either direction. the aile going up always tops out first. I have messed with travel limits and sub trim but nothing seems to help. weird.

also worth noting is that the servos that come with this plane are total crap. centering is pretty random and all over the place. especially one of the elev servos. I think I'll replace them but all of the sudden this "rx ready arf" doesnt seem like as good of a deal. oh well its still a pretty cool plane and if the wind/rain would ever stop I might get to actually FLY the damned thing!

RE: CMP EP Katana SR
 

Yeah the servos are pretty typical RTF stuff... compared to better servos they are ( cough * crude * cough ).

However I doubt you'll have problems with them unless you are into heavy 3D stuff. A typical sport flyer will be fine with them.

As far as the Ailerons....

Take the horns off the servos and check the travel of both servos at full extremes.

Put a mark on the servo to assure that travel in each direction is equal.

Then adjust the linkages to equalize the movement, even if this is at the expense of maximum control surface movement.

I found that when you switch from one vendor's RX to another, the pulse widths affect how far the servos travel and where the servos center.

RE: CMP EP Katana SR
 

Thanks, I'll try the aile test you've suggested.

I guess these servos might work ok but I seem to have one that is malfunctioning, one of the elev servos. when I give down elev and then back to center/neutral, the elev goes down but then doesnt return to center, instead it comes to rest @ 10-15deg up elev. however, If I apply up elev, then it will return to center as it should.

I maidened the plane this weekend and sure enough, the plane kept bobbing up after i gave it down elev. I had to fight it long enough to land the thing but I will def not fly it again until i swap the servos.

RE: CMP EP Katana SR
 

Okay I've found another problem with this plane- the ESC is also garbage. It doesnt seem to have enough power to run all of the servos. After I replaced all servos I powered it up and noticed they were chattering and twitching, just like you see with low batt voltage. I checked my batt to confirm it had a good charge and sure enough, it did.So then i disconnected the stock ESC form the rx and used a seperate rx batt pack, problem solved!

So now i wonder if the original servos are all that bad or if they were simply underpowered by the stock ESC. Hmmmm. <br type="_moz" />

RE: CMP EP Katana SR
 

Ah...

It could be the UBEC on the ESC is bad or one of the caps on it is blown.

If the pack fixed the problem with the tail servo as well ( a good sign! )... then I'd ask Eric or Andy for a replacement ESC.

The ESC/UBEC on my plane has no problems powering the servos... I believe I found the specs for the ESC a few weeks ago ( don't ask me where as I don't remember at the moment ) and I saw that it had a 2-3A capacity @ 4S and 2A @ 5S which should be more than enough.

At worst fly with another ESC and use the replacement ESC for another smaller plane.

RE: CMP EP Katana SR
 

The discoveries keep coming.

and btw my sincere apologies to the good people at Nitroplanes for jumping to the conclusion of a bad ESC. :-) I installed a spare 100amp ESC that I had and the problem (twitching servos) was still there. So then i disconnected the red (middle) power wire coming from the ESC and plugged the rx batt pack back in and the problem goes away.

Now it seems to me that these servos (spectrum A6060) are incompatible with the power from a BEC, or at least a 'built in' BEC. I still have not tried an external BEC ???

Has anyone else run into this problem?<br type="_moz" />

RE: CMP EP Katana SR
 

Weird I haven't.

I've flown the plane with a Spektrum AR7000 and even with an "Orange" DSM2 clone receiver.

Both worked well.

There is a bit of servo chatter sometimes, but nothing I consider unusual.

RE: CMP EP Katana SR
 

do you have one of these CMP Katanas? If so, i'm curious to know if you use expo and how much. this is my first sport plane and i find it a bit sensitive, but maybe thats the nature of this type of plane with its large control surfaces.

RE: CMP EP Katana SR
 

On both high and low rates I use 50% expo ( less sensitive around stick center ).

For high rates I have all the travel I can get out of the surfaces without bind, and my radio set to 150% travel in each direction.

In the D/R settings for high rates I have 100% for high and 50% for low in all but the rudder where I have 110% and 70% respectively.

This is about what I have my Funtana set to as well.

RE: CMP EP Katana SR
 

good to know.

so do you have this mapped to your flight mode sw or do you have to select rates individually? I ask because the way mine is configured, with flaperons set to 'on', it uses the flight mode switch to set flaperons and I dont know how to setup dual rates at the same time.

RE: CMP EP Katana SR
 

I'm flying it with a JR 9503 2.4gHz.

While I can set a switch for various "flight modes" I have the rates for each control surface individually controlled by switches.

Upper left switch for aileron rates, upper right for elevator, the next upper right for rudder.

My MIX switch controls enabling/disabling any correctional mixes, and my gear switch controls elevator to reflex mixing... ( for easier "Elevator" stunts ).

I find no need for flaperons. I tried it for a while and decided I'd never use it and opted for correctional mixing e.g. a small rudder to elevator mix for knife edges...

-

What TX do you have?

RE: CMP EP Katana SR
 

I have a DX7. I used the Flaperons (which i dont think I'll need) because thats the only way to get the dual elev servos to work with this tx, or at least thats the impression i got from one of the above posters. the other option would be to use a servo reversing Y harness. i think. ?

i still have alot to learn about mixing but it seems like a useful tool.<br type="_moz" />

RE: CMP EP Katana SR
 

I'm confused as to how the flaperon function impacts the use of dual elevator channels.

If anything you may need to TURN OFF flaperons and insteadl use a mix from the primary elevator channel to the gear channel, then reverse the gear channel and disable the gear switch ( so it doesn't screw up or affect the elevator connected to the gear channel ).

You could also opt for a reversing servo harness ( worst choice in my opinion as they "drift" with temperature changes ).
You can use a regenerative device like a Matchbox or the Futaba MSR... ( a good but costly choice as each cost about $70.00 )

OR you can merely reverse the horn position of one servo, so that servo one horn points up, and the other down... then connect both servos to the same channel... ( cheapest solution and quite effective ).

For this you'll have to assure that when you set up the linkages they are both "square" to each other as well as the linkages, otherwise you'll get dissimiliar movement.

RE: CMP EP Katana SR
 

You're right, I guess the Flaperons are a seperate deal from the elev.

I played around some more last nite and found that I cant get the Aile to work unless the Flaperons are 'on'. Otherwise the DX7 thinks there is only one servo for both Ailerons, and the manual indicates this as well. I will experiment some more tonite to see what I can figure out. At the very least I'm learning more about my Tx.

And I'm starting to understand mixing but as a new pilot I'm just not sure what to mix and how much. I guess it will reveal itself when i get more time with this plane.<br type="_moz" />

RE: CMP EP Katana SR
 

Ok...

Normally only one channel controls both left and right aileron servos.

The two servos are connected to the RX via a simple "Y" cable.

However some people prefer to have each aileron servo controlled via a separate channel. That's what the "Flaperon" mixing is for on your TX.

Turn on "flaperons" and you can have individual servo controlled by a different channel.

However in addition to this control, you gain the ability to set aileron differential ( in software ) and the ability to use the ailerons as "spoilers" ( reflex ) or "flaperons"...

This is more advanced stuff so to speak, and not needed for most purposes.

The plane doesn't really need aileron diffential, unless you need to correct adverse or proverse yaw during rolls.

Flaperons are normally used to lower the stall speed, but with it's big wings, this is wasted on a Katana.

"Spoilerons" or "reflex" MAY help for certain stunts like "Elevators", or to kill lift for landings, but few people do this or need it.

I'd forgo the flaperon mixing in your shoes, and just hook up a "Y" cable.

RE: CMP EP Katana SR
 

Iget it now. Idecided to turn on the flaperons and use a seperate ch for the left aile. mainly because it saved me a trip to the LHS, since i dont have a Y cable on hand. Thanks for the tips, opjose!

RE: CMP EP Katana SR
 

What are you doing for the elevator?