Carbon Z Yak 54

[squidger]

Hi Peeps

Am currently away with work for a month and have decided that since I am working hard and spending time in a boring hotel room I would cheer myself up and look for my next model. I really like the look of the Eflight Carbon Z Yak 54. Has anyone got any info on these. ie Have you owned one or even just flown one and can give me some feedback. These aren't cheap in the UK but they look to fly really well and it would make a good testbed for my new DX8 radio that's due to arrive soon as well.

Any views welcome good or bad.

Edit. DOH Just spotted the post below with alot of info on the Carbon Z.

[dkrhardy]

I know several people that have them, very popular. That wing is very strong but the rest of the plane is just average, you CAN break it!

BTW, wait until you TRY to make sense of the graph screen on the DX8! It was driving me crazy until I decided it is just window dressing. When you move the %'s for DR and Expo, this graph thing shows what you did. The weird, and difficult to understand part, is that the numerical values the GRAPH shows differ from side to side. And I have no idea why. You'll see my point when you program yours! GL
Don

[squidger]

I look forward to it.

[squidger]

The Yak arrived but with a severely bent fuselage so I returned it. Anyway replacement item came today and looks good. All assembled and set up with new ar 8000 receiver. Gonna fit telemetary unit later but first want to maiden. Weather forecast is pants with wind and rain for next week or so but will see if I can find a window of opportunity. Heres some pics before I damage it lol.

[squidger]

Maidened her yesterday. She flew beautifully. Needed just 4 clicks uptrim and flew straight and true. So much power (750 watts/50 amp)
Had 2 greased landings in 8 knott wind. Third landing was a bit hard in zero wind. She came in a bit quick and I was running out of runway so had to put her down. Slight bend in U/C but not too bad. Tried again and landed even harder doh. Straightened U/C again and ran out of battery power. I only have 2 batteries with a third on order. AT £45 a go I'm not buying too many. Have decided to invest in a car booster charger that jumpstarts cars but more importantly has a built in 17 AH gel battery and can supply a 12 volt charger although I'm not sure for how long. Costs a little more than a replacement battery for the Yak but will allow me to charge on site so 3 batteries should then be enough for all day.

[dkrhardy]

If the approach isn't good, go around and try again. Might just save your landing gear! You are actually lucky ..... I have "pranged" a plane or 2 by trying to save an approach!
Don

[JetPlaneFlyer]

Squidger,

£45 for a 4s 2800 battery! you can get them a lot cheaper than that. You might want to give Gens ace batteries from Giantcod.co.uk a try. gens Ace may be well priced but on performance they are second to none: http://www.giantcod.co.uk/gens-2600m...-p-406478.html (out of stock at the moment but they will get more)

Or even a top branded battery like Hyperion can be had for a good bit less than £45: http://robotbirds.com/catalog/produc...oducts_id=4100

The carbon Z yak is a nice plane but the price puts it against some really top class competition. Did you consider getting a Balsa ARF 3D plane?.. You can get some really serious 3D models for less than the price of the carbon Z yak (for instance you could build up this:Extreme flight Extra for less, the 48" EF models will build up about a pound lighter than the Yak. I guess it comes down to if you like foam or balsa and if you are prepared to spend a few hours assembling an ARF?

[squidger]

Yeah I thought about going the balsa route but just had to get the Carbon z yak out of my system. I am using 3200 mah Overlander batteries. Yes you can get cheaper but I find the less I spend the less life they have. These Overlanders will still be around next year whereas cheap batteries tend to lose their punch after a couple of months.

[JetPlaneFlyer]

Hyperion are a top brand, certainly not 'cheap' in any way. Gens Ace are quite cheap but they have developed a reputation for being as good as anything out there. I've got five of them and they out perform anything I've had so far and 4 months down the line and with maybe 20 cycles they are as good as the day i got them... Which is more than I can say for the Nonotecs I've tried.

3200mAh is pretty big for a plane of this size, fine if you want to fly pattern type earobatics or sport and you should get good long flights but it probably makes the plane a bit heavy for 3D flying. It's a nice looking plane though, good to see that you are pleased with it.

Steve

[squidger]

I'll look around. To be honest the original is a 2800 mah and the 3200mah batteries weigh not much more and are physically exactly the same dimensions. I cant give you a comparison weight wise cause the one that came with the Yak had a broken balance wire so I returned it and am still waiting for a replacement. When it arrives I will weigh them both and see the difference. The 3200 mah batteries are giving me about 8 mins of fast flying and throwing it about. I suppose I should throttle back and see how long I get but it's not that kind of model. It craves rapid full throttle climbes and flat spins etc or at least I do lol. Thanks for the advice. All taken on board.

[JetPlaneFlyer]

I get 7.5minutes out of 4s2200mAh on my 48" extreme Flight Edge, that's mixed flying but plenty of WOT verticals and KE spins and the like.. And that's with a 1000W set up. Light weight helps flight duration, the Edge is 51oz

[squidger]

Yak is 64 ounces. Everything is new though. I expect longer flight times when it loosens up.

[RMG]

Watching the vids of this plane I fell in love with it, but out of my price range (at least to stay married lol). Have heard of people having servo issues and having to replace. I'd like to see video if you ever do any, and a report as to how it does as it gets flights on it.

The bent fuse... was it a smashed box, or poor quality control? A plane at this price I'd hope it was shippiing damage.

[squidger]

Box was unmarked. Must have been poor quality control or stored in heat and it warped. No servo issues. Also had a battery with a broken balance wire so charger wouldn't charge it and kept setting alarm off.

Have got 10 flights under my belt now and she flies great. So much power it just disappears vertically and keeps going. Hangs on prop at half throttle. Luvly knife edges and a super fast roll rate even on low rates. Lands beautifully into an 8 knott wind but needs flaps on full to come in slow enough on calm days. Undercarriage is really strong thank god cause with no wind on the first day I arrived with a bump. In fact it's so good I bought a spare undercarriage and fitted it to my acromaster as it's much stronger than it's original. Everytime I fly it my heart rate doubles and I am relieved when it's down safe. Our grass runway is a bit long and it sort of grabs the spats on landing and tries to nose it in but I'm sure once we cut the grass that will sort itself out.

It's all stock except the 13 x 4 prop which is better for 3D than the 12 x 5 original. It's the sort of model that attracts attention cause the noise is infectious. Under power she roars around and gliding at idle the prop makes a loud woosh noise as you go by. Inverted is rock steady and confidence inspiring. Have already came past the runway at about 2 foot high inverted cause it just stays where you point it.

Verdict.

Excellent if a little pricey.

[JetPlaneFlyer]

That prop at 13x4 is super fine pitch. Don't you find yourself a bit short on speed?

[squidger]

I havn't used the original prop so can't make a comparison but short on speed is not a description I would attribute to this model. Open the throttle and she screams past at a rate of knotts. Pull up and it's out of sight in 5 seconds.I have flown hotliners that aren't as fast to be honest. Maybe I should slave in a 12 x 5 and see the difference.

Heres a guy using the 13 x 4 prop.

Carbon-Z Yak 54 with 13x4 APC prop

[JetPlaneFlyer]

Originally Posted by squidger

Heres a guy using the 13 x 4 prop.

I think the video illustrates my point quite well.. A very fine pitch prop is great for static thrust and is 'punchy' out of the hover and good low down acceleration but severe lack of top speed. The plane in the video spent 90+% of it's time hovering and probably never broke 25-30mph at any time. if you want to fly in the same way then it's the prop for you. Pitch speed with that prop and motor will be about 40mph.. max level flying speed maybe 30mph.

I do appreciate that 3d models are not about top speed but it can be nice to have a good turn of speed in your toolbox.

Steve

[squidger]

Yeah perhaps it wasn't the best video to illustrate the speed capability of the yak and while I agree the pitch is less, the 13 x 4 is 1 inch larger in diameter. I don't know what difference in thrust there is between the two but do know that the 13 x 4 pulls 750 watts and 50 amps and much more would be approaching max on the 60 amp esc. I will try a 12 x 5 though just to see the difference.

[JetPlaneFlyer]

APCe Thin electric props generally pull quite low amps for their size and pitch and are pretty efficient, you may even get away with a 12x6 APC. As a general rule props that are significantly less than half square (pitch less than half diameter) tend to be very inefficient in normal flight and limiting on top speed, they are best suited to slowfliers and maybe 3D models where you mainly want to do slow speed 3D.

Comparing static thrust for different diameter props, you can work it out with math. If power and efficiency is held constant then static thrust is proportional to the square of the prop diameter. So this means that if you went to a 12x5 prop and if it pulled the the exact same power (750W) then you would be down on static thrust by (12/13)^2 = 0.85.. so that's 85% of your original 13" prop static thrust. But speed would be up maybe 15% and your available thrust at normal flying speed would probably be higher too.

For general sport flying and pattern type aerobatics a 11x6 or 11x7 might in fact be the better prop, but not much use for 3D.

Hope this helps.

Steve

[squidger]

Surely if you are down on static thrust you would also be down on speed given that speed is directly proportionate to thrust and drag, unless by speed you mean prop speed.

[JetPlaneFlyer]

Originally Posted by squidger

Surely if you are down on static thrust you would also be down on speed given that speed is directly proportionate to thrust and drag, unless by speed you mean prop speed.

No, because static thrust is only when the plane is static and is no indication of what thrust will be available in forward flight. As the plane moves forward the thrust decreases. The rate of decrease depends on the pitch, fine pitch props loose thrust very rapidly as forward speed increases, courser pitch props 'hold onto' their thrust for longer as the forward speed increases.

Static thrust is therefore a very poor indicator of how a prop will perform in forward flight. Once you have some airspeed the the smaller courser pitch prop will probably give more actual thrust than the larger fine pitch one, even though the smaller one had less static thrust. If all you want to do is hover like the guy in the video then static thrust is all you are interested in, but for most people it's thrust available at normal flying speed that's important, hence a slightly courser pitch prop is better.

Confused?.. you will be

Steve

[JetPlaneFlyer]

Squidger,

I ran a couple of simulations in Motocalc for your plane with a 13x4 and a 12x6 prop. they didn't have your exact motor or battery but I picked ones with the same spec. The 13x4 one makes for interesting reading under the 'aerodynamic problems' heading. Compare that section the the 'aerodynamic notes' for the 12x6 prop. Note that with the 12x6 motocalc predicts you will still be fine on Amps.

I didn't do anything to skew these results, the only change from one run to the other was the prop. Power, weight, wing area are exactly as per your Carbon-z Yak spec. You can probably ignore the power system warnings, Motocalc is pretty conservative on power systems and throws out a lot of warnings if you drive your motor hard.

[JetPlaneFlyer]

For kicks here's a report for a 11x7 prop.. All looks good with this prop too, current is 52A so well within limits and you now have a predicted top speed of 70mph.. that's up from 26mph with the 13x4

In summary, the 11x7 is about the best prop for speed and pattern aerobatics, the 12x6 is probably the best all rounder having decent speed and still good static thrust for 3D, the 13x4 is pretty much useless for anything other than hovering, and is verging on being dangerous due to narrow stall speed to max flying speed margin.. That's what Motocalc says....

[squidger]

Motocalc warns about motor temp problems at full throttle and zero airspeed. Not sure how you would ever be at full throttle with zero airspeed given that she prop hangs at 50% throttle. Give it full throttle and airspeed rises rapidly. That said I am going flying tomorrow and have fitted the original prop (12 x 5.25) . Have balanced the prop first cause of all the horror stories ref Eflight out of balance props. It was out of balance but not badly. Have just put it on the meter and it's pulling 980 watts at 62 amps WOT. Obviously it won't pull 62 amps while not being held back but this is very close to maxing the ESC out. The only saving grace is I can't see myself holding full throttle for too long cause the Yak will be out of sight quickly. Anyway gonna testfly tomorrow and report the results and probably bring it back in a binbag lol.

[JetPlaneFlyer]

Hope you have a ball flying tomorrow. It will be interesting to see if the motocalc predictions are anywhere near the truth, it's usually pretty good. Weather forecast looks great up here, hope it's as good with you. I'll be out too flying my new Hobbyking Slick 360.

Steve