[secant0give]

I've often pondered getting a model of one of these. It's an interesting plane and quite a successful design in the full size version.
So when this one went up for auction on ebay starting at 99 cents I thought I might keep an eye on it, but some how I accidentally clicked the bid button............................ and well,,,,,,,,,,,,,,,,,,, it ended up arriving on my doorstep Tuesday morning from super and cheaper.

http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=400219574365&ssPageName=STRK:MEWNX:IT

Here are a couple of Pics of the fuse sitting on my work bench awaiting some attention.

   

Looking at it's construction it seems very nicely made and remarkably lightly built. All laser cut ply and balsa.


This is the motor I'll most likely be using in it

http://www.hobbyking.com/hobbyking/store...duct=14408

and this is the ESC

http://www.hobbyking.com/hobbyking/store...oduct=8921

It should be quite a good bit of fun to fly with that set up as it will probably work out lighter and more powerfull than the intended powerplant
and the air frame design lends it self to electric power very nicely

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I must say the instructions are not that good and there's a mistake in the way they are written so that if you follow them and hinge the elevator before attaching the tail plane you won't be able to put it together at all. Which is a bit silly. I won't be falling for that tho'

[Skidz]

How will the Yak 55 shape up to the Extras?

[samste]

That's One Big Plane wow 5kg weight

That site was one of the earlier sites i use to buy fron sonic saber, a10 etc for 99 cents plus 29.95 shipping. lol

Steve

[secant0give]

How will the Yak 55 shape up to the Extras?

I guess it will be similar to fly. there are differences between the other two.
The Red white and blue edge 540 Has Quite tapered wings and it will drop one if you give it to much elevator in a tight turn or pull out of a dive to hard. It's not a heavy model by any means and it's lucky that it isn't as I'm sure that this tendency would get worse as the wing loading went up. having said that about it it's not as bad as a lot of models, as far as tip stall goes, but it's gotta be in the back of your mind when flying it. The saving grace of this one is that it has an excellent power to weight ratio. Being heavier it also has inerta it seems to carry it's way a bit after you back the throttle off and takes longer to accelerate when you power up. In knife edge you have to balance the aileron against the rudder a little but not much, It doesn't like having the C of G set far back either, It's a fun machine to fly and it wasn't that expensive as it uses a turnagy motor and ESC, The servo's are a little pricey tho. But other than that it's a pretty cheap and cheerful set up.

The Precision Aerobatics Extra MX is a very light model. It's almost a Kg lighter than the Edge 540 the wings are less tapered and of wider chord so it has quite a lot more wing area, This further reduces the wing loading and it doesn't tip stall at all no matter how you disrespect it. In Knife Edge you just hold rudder and it stays there. It's the nicest plane to fly being just so forgiving, more so than most trainers. The Extra is light it doesn't have much inertia so when you back it off it tends to slow up quickly as long as it's not pointing at the ground that is. When you pour on the sauce it really moves instantly. When it stalls it's sink rate just gets more and it hardly even drops the nose. It has a very healthy power to weight ratio but not as a good as the Edge 540 tho' close to it. The cost of this model was nearly twice as much as the Edge 540 but you do get what you pay for.

The Yak 55 is a fair bit bigger than the other two which are about the same size, it will be heavier so it will have more inertia. I expect it will have a good power to weight ratio, the fuselage is quite round so it will be interesting to see how it goes in knife edge, the wing plan form is about midway between the Edge and the Extra as far as taper goes, I guess the wing loading should be similar to Edge 540 but since it's a bigger plane it should be easier to fly. I'm expecting nothing difficult in the air but it will be different to the other two. It's going to be about the same cost as the Edge 540 perhaps a little more, but it will be a fair cheaper on per Kg basis. I should be able to use two of my 3000 6S packs from the Edge 540 to power it. Just have to see where the C of G will end up to be certain of this

As far as build quality of the 3 Kits is concerned. I'd say the Edge and the Yak are nice light and straight with poor instructions but good hardware. The Extra MX from precision Aerobatics is altogether different. The quality of the build is SENSATIONAL the Instructions are thorough, they truly leave nothing out, and the design and use of materials is something to behold. It's almost a shame to risk it to flight as they are such a work of art. But they way they fly means that you barely give that a second thought. You can buy these with everything including the recommended motor, ESC and servos and it's the way to go but again it's more costly, however there is certainly great value for those extra dollars.

[secant0give]

Due to the inclement weather I've spent a little tinkering with this today
One thing I did notice when trial fitting the aileron hinges was that the slots cut for the outer two
in the port wing weren't quite on center. It wasn't much but enough to bug me, so I shifted them and got them spot on in the middle. All the other hinge slots were good. I'm not sure why the last two weren't bang on but just something worth watching if someone else gets one of these Kits.

Another thing I did when trial fitting the tail plane, I put the wing spar in and used it to eye ball against the tail to make sure it's straight. On this model it was slightly out perhaps 2 to 3 mm This was easily corrected with a sharp Exacto knife just shaving away at the seat where the tail goes in, 'till it sat nice and straight looking against the spar.

here's a pic
   

   

[samste]

Looking Good, ARF Builds always have there little Obstacles, Its Good You pick them up before there an issue or they make you start to custom them the hard way.

Steve

[secant0give]

One thing I must say is that the wings fit very nicely to the fuse

Here's a pic of them trial fitted. Nothing more to do here.

   

---

Looking Good, ARF Builds always have there little Obstacles, Its Good You pick them up before there an issue or they make you start to custom them the hard way.

Steve

First rule of any build. Think twice cut/glue once

[secant0give]

I've been busy today trying to work out how to mount the motor far enough forward as there is quite a good deal of space up front of the Yak, It was designed to accommodate a 30cc gas engine.
A quick trip into work before lunch to pick up some 6mm depron turned into a short mission in machining as well and here's the result. It's ready to be fitted.

   

[Skidz]

Nice job !

[smuzz]

Very nice Jason! Looks like a bought one.

[secant0give]

Thanks Guys

Here's a quick sequence of how I marked out the mounting holes in the engine cowling. It's not my idea, it was straight from the instructions for the PA Extra MX. I think it's a brilliant way to do it tho' and it's very easy to get the holes spot on.

A couple of pictures saves a thousand words as they say.

Add tape with out cowling on and mark hole position on tape

   

Peel back tape only partially tho' so as not to loose the hole position

   

Position cowling and put back tape with hole positions marked on it and drill through tape and cowling.

   

[secant0give]

Motor's mounted,

Just got to do some wiring mount the ESC and the fusalage will just about be ready.

   

[kizza42]

Very nice! Keen to see how it balances out considering the size of the intended motor. Might have to swing a Tungsten prop

[secant0give]

Very nice! Keen to see how it balances out considering the size of the intended motor. Might have to swing a Tungsten prop

Just put two 6S 3000 mah packs in it and it looks like it might balance nicely



I don't want to run a heavy prop or spinner as I want it to spin up as fast as possible

[secant0give]

I did some prop testing this afternoon.
After putting a set of new 3" wheels on it
I carefully balanced two new wooden props and removed and rechecked the
one I flew with the other weekend.

The first prop I tested was a 2 blade JXF wooden 21X6 it pulled down the pack voltage to 42V from 50.3V
Pulling 119A full peg static, this equated to 4998 Watts. I could barely hold the plane with one hand as the other operated the throttle stick. No great vibration was noted

The second prop I tested was a 3 blade 17X6 JXF wooden prop it pulled down the pack voltage to 43.34V from 48.8V
Pulling 69.83A full peg static, this equated to 3069 Watts. It was difficult hold the plane with one hand as the other operated the throttle stick. No great vibration was noted

The third prop I tested was the one I flew the test flight with, an APC 18X10
it pulled down the pack voltage down to 42.50V from 47.83V
Pulling 76.45A full peg static, this equated to 3317 Watts. It was also difficult hold the plane with one hand as the other operated the throttle stick. No great vibration was noted but there was a lot of prop noise at just over 2/3 throttle. This could well be due to the pitch of this prop being a lot greater ie 10".

I think I might use the three blade 17X6 for the next flight.

[secant0give]

Well it's had a few flights now and I must say that after a bit of tinkering with the Cof G and many thanks to Darren it's set up pretty nicely as far as balance throw's and controls go.

However the motor now needs some attention. I know Gaz was keen to find out my thughts on the Turnigy G160 motor and how it went on 12 S.

Well the news is not all good

It was flying great Yesterday!! but started making some strange noises while in the air on the third flight . Landed OK and packed it up. later on at home I took the motor out and found that about half of the magnets have come loose. Luckily none of them are damaged and I can hopefully just bond them back in place. Also lucky it didn't just jam up and stop the motor completely.

The design of the motor is such that the end of the magnets are located in pockets cut in the aluminum that forms front plate of the motor. This is I'm sure what stopped the motor from having a totally catastrophic failure. It was still flying the plane OK.

I'll take it in to work tomorrow and over a few lunch times this week. I'll check it all out bond the magnets back in and re balance the motor. It should go back in the plane before the main strip is all dry again.

Perhaps the Eflight or Hacker motor is a better choice for a big bird like this.

[secant0give]

Well I managed to get the motor magnets all sorted. I found out that the best glue for this purpose is called Loctite 325 and it's used with loctite activator 7075. You put the activator on one surface and the glue on the other.
This is the stuff that the guys from CSIRO used in the manufacture of their solar car motors, Infact most of the front runners in the solar care race used CSIRO motors at about 25K$ a peice.
Aparently bet best technique is to use the loctite 325 to bond the magnets in and then grout the spaces in between them with Robnor PX700K special epoxy.
How lucky can you be, They Just hapined to have some in the fridge that was going to be thrown out because it had recently reached it's used by date.

Well let me tell you it was no mean feat getting the other 6 magnets that wern't loose out of the motor with out breaking them. I figured that If half of them had let go the others might well soon follow and it would worth doing the lot with the good glue.

It was almost as much fun scraping the old adheasive off the magnets and from the inside of the motor's flux ring to get them nice and clean. I must mention that I marked the 14 magnets with red and blue perminant marker for north and south as they have to go back in the correct order, alternate north and south otherwise the thing won't work properly.

Then came time to put the glue on and place the magnets back. They are bloody strong magnets and you have to hold them with a pair of plyers and some force to get them in the position you want them in. Fortunatly I had another caperable pare of hands to give me some much needed help in holding the motor while I wresseled the sticky glue coated magnets into place with my trusty long nose pliers. On more than one occasion flowers in the garden were seen to wilt due to the nature of the language being used.

Finaly all magnets were bonded in, hopefully this time for good, but not before hands plyers and many other things were covered in loctite 325. I don't know if you know the smell of loctite but It realy irritates me and once you get it on you it's very hard to wash off.

By then I needed a Bex, a cuppa tea and a good lie down.

The nest day I cleaned then grouted the spaces in between the magnets. Cleaning with acetone
and grouting with Robnor PX700K epoxy. The epoxy was just a little on the thin side and I mixed a small amount of filler with it so it wouldn't slump. this made it a lot easier to do the grouting.

All in all It was a difficult and unpleasent task but the end result looks very nice. I'll put the motor back in the Yak tonight and might even get it up for a fly on the weekend, weather permitting.

Moral of the story is, buy a good motor the extra money is definatly worth it. If I was to charge for fixing this one it would be enough to buy two good motors I reckon.

[gbanger]

Well done Jason, glad it was you and not me I would have lost the plot and sent the thing into orbit. Patience with things like that is not one of my forte's. I would have thrown it in the bin and bought a new one.
Gazz

[secant0give]

I got a chance to test it out on Sunday
After a quick few runs up to full noise on the ground I gave it a flight testing
Three flights of about 5mins giving it as much stick as the gusty conditions would allow
And the back to the bench waiting for a few spare minuets to pull the cowl off. Just finished looking at the motor this afternoon. Im happy to say All the magnets seem to be still stuck fast.
Hopefully they'll stay that way

[gbanger]

Good job Jason

Glad you got it sorted, Im glad I didnt have to pay you for the labour to fix it!

I had a close call with my Dueces Wild at Penrith yesterday. The Right hand motor mounting plate let go at about 300 ft over the centre of the strip at almost full speed. The noise it made scared the crap out of me.
I shut off the throttle immediatley, hit full flaps, droped the gear and turned it into a tight spiral decent. Had too much pace on when I hit the tarmac (I didnt want to drift to far down range and not make the runway) so the landing gave it a pretty nasty jolt, but apart from breaking the prop the beastie came out if it without a scratch.
Didnt know my heart could make so much noise.
Gazz

[Skidz]

Sorry for the thread hijack Jason... Gazz, close shave there ol' boy. I presume you hadn't practiced dead-sticking the DW so it was a mighty hot landing. Fixed now?

[secant0give]

Well done Gazz !!
Glad you got it down OK

It's disconcerting hearing a noise like that especially, 'cause initialy, you've no idea
what caused it. Kind of adds some extra pressure to an unplanned landing!!

[gbanger]

Disconcerting is an understatment Jason,
At the time I thought "Oh No, Goodbuy DW."
No Dave... I have not repaired it yet. I am going to modify the firewall mounts on both motors and that is going to take some time due to the restricted acces to that area, probably wont be in the sky for another 2 weeks (putting in some big hours at work at the moment).

[secant0give]

diagnosis......................pilot error probably caused by a combination of dumb thumbs brain fade and flying with the ground too close.

   

[secant0give]

Going slowly back together.
I think I left a couple of peices behind in the swamp
and I need to get some 20mm diameter carbon tube as the
wing joiner snapped clean in half. But it's a start

   

[secant0give]

A bit more work on it this weekend

[secant0give]

Did some more work on the Yak tonight
She's getting closer.

A bit like all dressed up and nowhere to go at the moment with the area 51 situation

[secant0give]

Well it flies again !!
I test flew it and had two flights with the beast on Saturday
I was realy happy with how it flew, will try some different props with it now to see what works best

[Claudius]

Nice work Jason - looks like a heck of a rebuild effort!

[secant0give]

Nice work Jason - looks like a heck of a rebuild effort!

Thanks Claudio,
It was a bit of an Eppic repair, but I did have a few missions in between, like building, then repairing, the little Zeke after it's structural failure and starting some work on the Yokosuka float plan. Not to mention the repairs generated from two separate Mid-airs with the little edge 540 now know as "the yellow Peril".

I'm glad I did rebuild the Yak. I got another Yak 55M airframe the same size from HK AUS warehouse and would probably have just shifted all the gear over to that one but the paint work on the cowl was all wrong. I'm still arguing the point with HK via Paypal. It's taking some time to resolve and I wanted to have one of the two Yaks in the air before Christmas, I only just made it