Carbon Z Yak 54

[squidger]

Ok so I flew it today with the 12 x 5.25 prop which was pulling 250 watts more than the 13 x 4 prop I was previously using. You're gonna find this hard to believe cause if I hadn't witnessed it myself I wouldn't have said it was possible. The Yak is no faster with the original 12 x 5.25 prop. If anything I would say it was slower. I did a low flyby and opened her up and whilst it wasn't slow it was quite sedate. When I did that with the 13 x 4 prop fitted it was scarily quick and if I didn't throttle back quickly it was out of sight. Gonna go back to the 13 x 4 and fly again on monday to confirm. The real difference I noticed was the acceleration was easier to manage especially on landing which made softer touchdowns easier.

All the figures suggest otherwise but the truth is the lower pitched prop is definitely the way to go.

[JetPlaneFlyer]

Well that seems very odd because the pitch of that prop and the kv x voltage only gives a theoretical 40mph, which is hardly scary fast, but I cant argue with reality

The only thing I would suggest if you are up for any more experimenting is trying a 12x6 APCe, the standard prop may just be very inefficient.


Steve

PS....Stupid question but you didn't have the 12" prop on backward by any chance?

[squidger]

Lol. I'm sure it was fitted the right way round. I wouldn't have got those readings on the meter if it was fitted backwards. I'm as puzzled as you as to whats happening. It shouldn't be but I can't ignore what is happening. Bottom line is the performance is much better all round with the 13 x 4 prop so I will stick with that for the time being. I'll try to remember my camera next time and see if I can get someone to video it.

[JetPlaneFlyer]

Originally Posted by squidger

Lol. I'm sure it was fitted the right way round. I wouldn't have got those readings on the meter if it was fitted backwards. I'm as puzzled as you as to whats happening. It shouldn't be but I can't ignore what is happening. Bottom line is the performance is much better all round with the 13 x 4 prop so I will stick with that for the time being. I'll try to remember my camera next time and see if I can get someone to video it.

Fitting it backward would not have made much difference to the wattmeter reading, and the thrust would still be 'forward'. All that happens when you put a prop on backwards is that it becomes less efficient and thrust decreases.

Prop blades generally have a airfoil shape that's similar to a flat bottom airfoil used on a wing. The flat side of the airfoil always faces rear. (sorry if you know all of this already but it is a common mistake)

Video would be cool.

[squidger]

No worries Steve. You gotta ask just in case. I'm an Aircraft Engineer so if I fit a prop backwards I auta be shot lol. Mind you I have come across many people flying models with insufficient thrust to find the prop fitted backwards. Better charge the camera up and hope I can find someone with a steady hand and quick eye to film it.

[squidger]

Right, got a few more flights in today. Was a bit windy. Probably 10/15 knotts gusting 20 at times. 13 x 4 prop is defo my preferred choice. Did some high alpha and slower flying and she was steady as a rock. Opened her up and she just screamed around the sky. Unusually I feel more at home flying on low rates, mind you low rates on the Yak is like high rates on other models. High rates is just too much movement and manouvres look untidy. Had some nice landings and one or two good touch and goes. One the whole length of the runway holding the tail up all the way. Think I'm gettin used to it finally.

[JetPlaneFlyer]

Squidger,
Sounds like however that prop is working it's working great.

Regarding the control throws, I've not been flying 3D for long so also had to get used to extreme throws (45 deg each was on all surfaces).. Exponential is your friend here, 70% or more really makes a huge difference and calms the controls right down. Lots of expo also much reduces cross input of control where you inadvertently maybe add aileron when you pull on the elevator.

Steve

[squidger]

I agree. I set it up as per the instructions.

High Rate

Elev 50mm up and down 50% expo

Ail 70mm left and right 60% expo

Rud 65mm left and right 50% expo



Low Rate

Elev 15mm up and down 25% expo

Ail 30mm left and right 30% expo

Rud 45mm left and right 25% expo




I also have the ability to use 3 different rates on the DX8 so set up a mid rate inbetween the high and low settings which is where I have been flying but low rates today were much better for clean fast flying.

[squidger]

Have ordered some sensors for the telemetry. Have ordered the pitot tube assembly and the altimeter sensor so when they arrive I will be able to get accurate speed and height readings.

[JetPlaneFlyer]

That will be interesting!.. please post the results

[squidger]

Will do. Am also gonna try an 11 x 7 prop as a mate said he flew his with that size prop and it was ballistic.

[Mysterious]

What kind of flight time does the stock 2800mah battery provide?

[squidger]

Wish I could tell you but my stock battery was faulty and I sent it back. When the replacement came 2 weeks later they had just sent me the original back which was still faulty. The telemetry module for my DX8 is also faulty (The bind button has been pushed in too far/ broken off circuit board). I get about 8 mins from my 3200mah overlander batteries if that's any help. That's spirited flying so prob could get 10 mins on lower throttle settings.

[JetPlaneFlyer]

Originally Posted by squidger

I get about 8 mins from my 3200mah overlander batteries if that's any help. That's spirited flying so prob could get 10 mins on lower throttle settings.

I'm still getting the feeling that your 13x4 is working really inefficiently. For comparison I also get 8 minutes flight time from my similar size EF Edge 540, and that includes lots of high energy aerobatics with WOT. i also stretch to 10 mins by taking it easier. The power system on mine puts out a shade under 1kW.

I'm using a 4s 2200mAh battery.

Steve

[squidger]

When I get my telemetry unit back from Horizon I will be able to give speed height temp figures and will know more about which prop gives best results.

[bonsairick]

I haven't seen anything mentioned in this thread about the Carbon Z's faulty motor mount. The metal is faulty and can (and does) shatter. If the CZ you bought was sitting on the shelf for a long time, you might want to contact Horizon. They were replacing the original mounts with a redesigned "V2" mount for free. I bought mine 3rd party on eBay. My original shattered in-flight, 3 of the 4 tabs had sheared while going vertical. (I was able to kill the throttle and dead-stick it in safely.) The prop WAS balanced. 12x6 APC is perfect for sport. The servos suck and had to be replaced. As mentioned earlier, check your control horns where they mount into the body of the plane! The rudder horn pulled loose on mine very quickly. Fun plane to fly. Replacement parts relatively cheap. Though rebuilt plane several times, the wings NEVER broke - the carbon honeycomb is REAL strong! Happy flying!

[squidger]

Mine has the v2 mount. Everything is balanced and on your recommendation I have fitted a 12 x 6 apc prop. Havn't had the weather to test fly yet but on the meter its reading 900 watts and 58 amps at WOT. Hoping for a break in the rain to try it out.

[wac]

Nice...

[Mysterious]

I've noticed a lot of people post that there are problems with the servos in this plane. What Servoss have you guys replaced the stock ones with? I'm not an experience in the flier to buy a full fuselage balsa plane so I'm very tempted to buy this because if I crash at it stands that I can repair it was some CA glue. Though I'd like to know ahead of time what additional Costs I'd have to put into the already $400 retail price

[JetPlaneFlyer]

I don't think the CZ yak would repair like a typical foamy. The structure is hollow with lots of carbon bracing. It's probably going to be no easier than a balsa plane to repair, maybe harder in fact because with balsa you can re-make broken parts and when you cover it with film it all looks good as new.

At least if you buy ARF you can select decent components and not have to take the poor quality stuff that sometimes comes in a Pnp package. A balsa ARF will also build significantly lighter than the yak making it easier to fly, especially easier when it comes to learning 3D.

[squidger]

I broke the left hand elevator and half the stab when I came in low high alpha and powered out after long grass had got jammed between elevator and stab.I repaired it but it looked bad so I bought a complete left stab with elevator.cost only £5.

[JetPlaneFlyer]

£5 is very reasonable. For sure spares availability and pricing is one of the plus points of Horizon products.