CARF Yak55 SP 3.3m Build

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Re: CARF Yak55 SP 3.3m Build

Postby Billy Bunter on Fri Nov 09, 2018 12:13 pm

Since the last post, we've been getting on better with the YAK55, but found that the header pipes still need to be extended.

So, its been a bit of messing around, but I've had one set extended by 3/4 inches and another by 1.5 inches.

Fitting them has required some surgery to the fuselage, to fill in the old opening, cut away part of the rear bulkhead and put in a new bulkhead. But, I just finished and and if the weather permits, I hope to get out this weekend for some further flights.

I'd never do this again though. That is to say, buy the headers and pipes from different vendors. If I did this again I'd go for a matched set, where the vendor has done the work of determining the correct header lengths.

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Re: CARF Yak55 SP 3.3m Build

Postby Billy Bunter on Sat Nov 17, 2018 4:17 pm

With some good weather today, I was able to get out with the YAK55. I completed the LMA flights, which was a good milestone and the paperwork can now be submitted to finish the process.

The engine was more lively with the 3/4inch header extension. The YAK55 now pulls out of a hover and accelerates as its climbing vertically. This is using a 32x12LF Mej prop. I think there is just a bit more performance still to come. So, on the next outing I'll try the second set of headers, which will give a further 3/4inch extension. And, I'll also give the Mej 32x12 EVO prop a try. Either way though, I'm not seeing a need for (yet more) extension work to the headers. I can see the performance is going to be where I want it with the headers currently I have.

All in all, very pleased with the YAK55. It feels locked in and flys light :dance: . Bring on next Summer....

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Re: CARF Yak55 SP 3.3m Build

Postby Billy Bunter on Fri Nov 23, 2018 3:46 pm

I managed to get out to the PMFC today to have another go with the YAK55. I'd fitted the longer header set, which definitely unleashed a few more RPM and made the throttle response just a little bit more aggressive.

So, after a flight with the Mej 32x12LF, I removed that prop and instead fitted the 32x12EVO. The engine swang this priop with command and static thrust definately went up! In the air the YAK55 now pulls out of a hover with more command and accelerates faster.

So, I'm now very happy and plan to carry on flying the model 'as is'.

From here all that is left is to do some work on the TX set up (such as adding a bit more aileron differential) and I also want to see if I can get some more throw out of the elevators.

Overall I'm really pleased with the YAK%% and also very pleased I didn't just give up with the model when the first one went in!

I've got four other 40%ers, but the YAK55 is just that bit bigger and it does seem to show up in the way it flys. Its just that bit more mild mannered in the air, which I like.

Assuming I get out this weekend, I'll be turning the smoke on and will see if I can get someone to take a few photos of this for me with the YAK55 in the air.

In the meantime, here is a photo from last weekend that a club member sent to me.

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Re: CARF Yak55 SP 3.3m Build

Postby Billy Bunter on Sat Nov 24, 2018 12:04 pm

I’m back at PMFC this morning, braving the inclement weather. But, today the mist and cloud base is much higher and so I’ve been able to really open up the engine and allow the YAK55 to eat up the sky.

I’m so impressed with the MVVS190 engine now. Having hit the sweet spot with the header length, the engine is swinging the Mej 32x12EVO prop with no problem and the vertical performance is just endless! Also, this setup is pretty quiet, with little in the way of prop rip!

Really impressive considering that I’m now basically getting the same performance from the 190 that I do with my Mintor 220s...

I’m going to have lots and lot and lots of fun with this!

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Re: CARF Yak55 SP 3.3m Build

Postby Billy Bunter on Sun Nov 25, 2018 6:19 pm

I was back at the PMFC early today and got 4 flights in on the yak55. Improvements I made were

1). Increased the amount of aileron differential
2). Added a 6% rudder to elevator (up) mix
3). Got the smoke pump working

The yak55 now rolls very axially!

Steve Roberts also had a couple of flights and Dave W a flight. Steve flew the yak55 with the smoke on, though with an overcast sky it didn’t show up that well. We decided I’m probably pumping a bit too much smoke fluid as it was strangling the engine a bit at higher RPMs.

Dave did a couple of massive knife edge loops. The first at high power saw rudder blowback whereas the second at a lower power level didn’t see this happen. So, I’m toying with the ideal of replacing the two Hitec 7990s on the rudder with a pair of the new Futaba A700 servos. This will take the torque driving the rudder from 88kg to 148kg.....!

Finally, I’m finding that since I got the header lengths sorted the fuel consumption has dropped. An 8min flight of mixed Aeros is using about 0.75 litres of fuel, which is pretty good. I have a 1.5 litre tank fitted, so have either plenty in reserve or can opt to only fill the tank say 3/4 full.

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