X_MAN

On the papers, ASP 61FS is rated at 0.83HP whereas Saito is at 0.90HP. but slightly heavier than the Saito.
Anyway, I don't really trust the advertised HP figures... You really have to try them out, to see if it works for you..

A safer bet would be a 70 FS or 50 2 stroke.

What is the actual weight of your plane with the Saito56 combo?

zul_cessna

x man, i did not measure the overall weight but i keep minimize as possible.

Bonified Wingnut

Sorry 'bout your plane.
I had something like that happen to me when I first started flying, with an electric I had scratched out.
Right after it rolled and did a nosedive I started walking toward it and went to collapse the radio's antenna and....oops I didn't need to..I had forgotten to extend it..ha.
Right thrust is good...and your motor should have had plenty of power for the plane...it might not have flew 3d or whatever they call hanging on its prop.
More power on an unbalanced plane will get you to the ground even faster then the last time.

zul_cessna

bonified, i agree with you too, at least, when i post it here, i got a clue where goes wrong and as a lesson in the future. first place, i thought small engine should be enough for this plane since its body very lightweight compare to other plane in its size.

tIANci

Just a little something about RX antennas ... Ihad 3 crashed on a Futaba 6EXA, never knew why. Later whilst flying a foamie I saw that the antenna was cut, this happened because I did not put and relief on the antenna. Always make sure you use a button or a bit of fuel tubing on the inside of the fuse.

zul_cessna

Now i'm getting saito .72 engine, what is the best prop for this 40 size yak and .72 4c engine ?

X_MAN

Benchmark prop for the 0.72 is 13X6, you may want to consider APC props. MAS props too much flexing. Bolly is a good alternative.
Just spent sometime to run in the Saito and it will gives you a very good performance with this combo.

You can try 14X5N APC if your ground clearance allows..

Remember to balance the plane to the recommended CG as in the manual, that should give you a slightly nose heavy plane for stability, and although optional, I would always balance mine span wise. It Flies better.

Anyways, if you happen to Visit JB, send me a PM, we can fly together!!

All the best!

zul_cessna

thanks x man, can i still use 12.25 x 3.75 coz i prefer torque instead of speed, which prop with give the fastest to get maximum rpm

tIANci

The Saito 72 will give you best performance when you prop it to about 9,750 RPM - 10,000 RPM, no use getting it to spin at 12,000 RMP at all with the 3D prop. Just go with the 13x6. Again, if you run 25% nitro you will see that that motor is superb.

X_MAN

Zul,

You will over rev the engine with the prop.

If you want more thrust, try a 14X4 wide prop. Keep the peak RPM to 9800~10000rpm. The suggested, 13X6, is a good prop for the 72, with a good balance between Speed and thrust, a 15% nitro content fuel is good enough.
Try 25% or 30% nitro fuel, if you wants more torque to spin the bigger prop.

The APC12.25X3.75 prop is basically designed for Control line stunt flying with 40 sized 2-stroke engine, running at Wide open throttle.

zul_cessna

thanks a lot to tianci and x-man, you guys very helpfull, I probably going for 13 x 6 or 14 x 5 (APC), YAK 54 repairs done and now applying monokote cover. I sent to bro Maman for the repair work and he did a good job to align back the small pieces of broken part and use new wood/balsa to cut into shape. But of course, it will slightly heavier than original due to epoxy and glue.

alan0899

G'day Mate,
Were you at full throttle when it stalled & crashed?
IMHO, you stalled, due to lack of airspeed, caused by lack of prop pitch, that 12x3.75 or whatever is a 3D prop, not a good one for the first flight of any plane, try an 11x6, or 12x6, & keep the airspeed up.
Also, what angle was the aircraft when it started to roll, was it level or was the nose pointing up at a high angle?
When you get used to the way it flys, then play around with props, you can always throttle back if it flys too fast, but if it won't fly fast enough to avoid a stall, at full throttle, you are stuffed.
I just thought of something, when you tested the plane on the ground, did you check the ailerons at the maximum throttle setting.
I got cought with this problem on Sunday, I checked out a guy's plane, on the ground, engine running at idle, ailerons, elevators & rudder OK, taxi out & take off full power, lift off, plane rolls left, apply right aileron, no aileron response to the right, thottle back, & ailerons respond, just enough to get the thing rolled to right knife edge, in she went between trees, small damage, when checked out in pits, found that the thottle servo arm was fouling the aileron servo arm, at full thottle.
He had put the arm on so it was in the centre of the fuselage & not with the push rode running close to the side, easy fix, & now I will make sure I check every new plane I test fly, at full thottle for servo response.
Sorry to ramble on.

zul_cessna

Hi. Alan0899, I was at full throttle when it stalled, I guess its due to lack of airspeed because once the tail lift up, I pull the elevator which I shall stay on the ground a little more, also I agree with you about the prop, I should use 12 x 6 instead. About the throttle linkage and servo, I think shouldn't be a problem since I place it in front of the fuselage.

X_MAN

Zul, it's 14X5N for Narrow blade, With the normal 14X5, the 72 will not get to it's optimum rpm.

All the best for your next flight!

zul_cessna

X man, I have 13 x 6 narrow(APC), can i use it, what is the result ?

tIANci

Zul - yes yes yes ... you can use the 13x6, just tach her to about 9,750 RPM max ...

nubli

ZUl cessna.. long time no hear about your yak 54 with it's new 72 4c engine.. how it goes with remaiden..

that thing sure fly good with 4 stroke. i love the 4 stroke sound...

good luck

zul_cessna

Hi Nubli, thanks for asking, have had installed everything even the engine but have no time to break in the saito .72. Currently fly my trainer 25 with .25 engine and CAP232 40 with saito .80. Will update once I maiden it.

zul_cessna

After rebuild my YAK 54, i found that the firewall slightly down by 3mm from the original, I have tried many ways to move it up but there's no way because it has limited space for carburetor. will it cause any problem it i just leave it with current position (3mm down from actual), meaning my engine also will come down at 3mm lower.

nubli

Zul, should be ok la... 3mm down not much la.. just the fuel tank level will be a bit higher by 3mm.. may be flooding the carb a bit, just try... you may have to retune the needle.. or lower the tank also by 3mm.. it solve the little 'problem'.

just make sure the thrust line is same not going up thrust by 3mm then will be problem when you give more throttle..

good luck buddy..

zul_cessna

This is my YAK54 aftr repair works took place, rebuild with light plywood and covering with monokote at the bottom and right side of fuselage, cowling still looks new since i didn't use it during the maiden flight. now installed with saito .72

tIANci

Zul - looks decent for sure! This time enjoy the plane and keep her alive ok.

zul_cessna

tianci, I couldn't find a standard 13 x 6 APC, so far I went to a few shops and only found 13 x 6N. I do not want to fly fast, what is your advice if I use 13 x 4 APC ? 14 x 4 not giving a good ground cleareance by looking at the flying site condition

X_MAN

13X4, 13X5 should be Ok, gives a lot of thrust, not much speed thou...

Al Lewis

If you want to fly it on the prop then an APC 13x4W will fly it great with that engine. Otherwise go to a straight 13x6. The 13x6N is for high speed stuff and shouldn't be used on a YAK. The plane is aerobatic and needs thrust as well as speed. BTW From what you said of your first crash I would say you simply tipped stalled due to lack of speed and power. The prop you were running wasn't nearly enough.