102'' OMP YAK SP55M with Plettenberg Predator

[bluelevel]

A few months ago I purchased a new Plettenberg Predator 30/8 motor through my favourite RC forum, which is waiting for work since then. Because I completed all my other projects and I was keen on building something new, I gathered info on an appropriate home for the motor. Already months ago I stumbled upon the EG Aircraft YAK SP 55 M, which made a positive impression to me. Here in Germany the EG Aircraft models are distributed by Engel Modelltechnik, where I picked up a huge box and squeezed it into my station wagon. In the US these fantastic models are available from Ohiomodelplanes.

The look of that plane seems to be "inspired" by the yellow finish of the well known Sebart models, optically it looks like the big brother of a SU 140 by Sebart, which I have in my hangar as well. The YAK has a wingspan of 102'' and I expect the final weight to be about 25lbs. So despite the electric setup I think to be a little lighter than a 100cc boxer with full tanks.

I plan to use the following equipment:

Motor Plettenberg Predator 30/8
Prop 28x10 Mejzlik
ESC Yeti Spin 200
12s Lipos SLS ZX 6000 35/50C (only available in Europe)
4x Hitec HS 7985MG on ailerons
2x Hitec HS 5955TG on elevator
1x Hitec HS 7955TG on rudder
Spektrum receiver AR12100 with integrated power box
2x A123 2300 as RC power supply

The next days I will post detailed info on this awesome model as well as lots of pictures to document my building progress. Since large aerobatic planes with more than 2 meters wingspan are still very rare, perhaps this thread works up the appetite for more...

[Jeffery]

Yep, don't see very many Yak 55 models.

[cwojcik]

Yep, don't see very many Yak 55 models.

Agreed. The 54 is everywhere, and I am sick to death of them. But you don't see many 55's other than the Krill, Comp-Arf, and this. I really like the 55.

Can't wait for your build.

[NumbSkull]

Cant wait to see how the build goes.

I have to agree with cwojcik, I'm SICK of yak 54s, but have a real soft spot for yak 55s.

Might have to look at ohio models and see what they have to offer!! :D

[bluelevel]

Here are the first photos of the OMP Yak 55:


Pic 1: All parts are delivered together in one huge box. Wings, stabs, cowling and accessories come in extra boxes and are secured with bubble wrap or styrofoam.

Pic 2: A part of the designated rc equipment. A highlight is the new Spektrum AR 12100 receiver with integrated power management, which I will use with two A123 Packs without voltage regulation.

Pic 3: Uppper and underside of the wings provide a good contrast, thus attitude recognition should be no problem. The covering quality is excellent, the film is high-quality "Oracover" from Germany (as far as I know it is sold as "Ultracote" in the US).

Pic 4: On the left this is not the horizontal stab, this is one wing of my 76'' Sebart SU-29. Who copied from whom seems to be obvious ...

Pic 5: All accessories are wrapped in separate bags sorted by assembly groups. The overall quality of the hardware is very high. I will use all parts except the servo arm extensions, so I don't have to spend additional money on pricey extra hardware.

Pic 6: Exactly as the wings the stabs come completely pre-hinged. The covering quality is as good as the wings.

Pic 7: The root rib is made from solid GF material and not from cheap plywood. Thus the stabs can be mounted securely to the fuse.

Pic 8: The wheelpants are not scale, but painted nicely. The pants are beefed up in the mounting area, they come pre-drilled and captive nuts are mounted already, too.

Pic 9 and 10: View inside the wing. The bondings look clean and neat, the manufacturer did not save on glue. The wing tube reaches far into the wing.

Pic 11: The engine mount appears very rigid and is reinforced with aluminium brackets from the inside. The covering quality of the fuse is good, there were only a few smaller wrinkles which had to be removed with a heat gun. The fuse shows a few unsightly overlappings of the covering film, but I think it's almost impossible to cover a 90 inch fuse with one end-to-end piece.

Pic 12: In the fuse there was a fully assembled fuel tank mounted with velco straps. I think I won't need that part ...

Pic 13: The wing tube is adequately sized and perfectly glued like all other areas of the fuse.

Pic 14: The fuse has openings for two standard size servos or one jumbo size. Also a good idea is the cable tube, which makes it easy to wire the elevator servos.

Pic 15: The gear mount is reinforced with aluminium brackets. All gas fans will like the huge exhaust tunnel.

Pic 16: The canopy is already glued and fits almost perfectly. Unfortunately the paint job shows a few minor inclusions, so it seems as if one was not careful enough with painting preparations.

Pic 17: The cowling has a diameter of almost 12 inches and has a mounting ring, so you will not see any screws. The bonding of the mounting ring was not done perfectly, so I will reinforce this area with a carbon rowing. This seems to be a common problem of this model, because I heard of a similar problem on Flying giants. But if you know it, it's not a big deal to fix. Unfortunately the cowling shows the same minor dust or dirt inclusions in the paint.

Pic 18: As an example here you can see the elevator hardware. The kit comes with rigid double GF control horns and titanium push rods, which have a left/right handed thread. This makes length adjustments easy without having to unscrew a ball coupling each time. Also not a matter of course are the black anodized servo extension arms.

Pic 19: The CF wing tube has a diameter of 36mm and a wall thickness of 1mm. The fit is perfect.

Pic 20: The fit of the wing to the fuse in the rear area is fine, there's almost no gap.

Pic 21: Solely in the front area there is a small gap of about 3 to 4 mm.

Pic 22: The carbon landing gear is fabricated perfectly, weighs only about 300 grams and is even airfoiled!


Alltogether I am highly satisfied with the quality of the kit and the provided hardware. As defects I only noticed the bad bonding of the cowling's mounting ring, the small gap of the wing fit to the fuse and the few minor painting flaws. The covering job is excellent and the amount of pre-fabrication with pre-hinged control surfaces is outstanding. So EG Aircraft delivers a very high quality for adequate money.

I already started the build, more pics will be added the next days.


Thomas

[bluelevel]

Because of the rainy wheather I was able to continue the build of the OMP Yak 55, here is the second bunch of photos:


Pic 1 & 2: Should I ever require to put the model back in the box, this should be easier with a removable rudder. Therefore I cut the robart hinges and slided a piano wire through them.

Pic 3: As usual for this size of model, the elevator servos are mounted inside the horizontal stabs. The glass control horns fit perfectly in the milled slots. I sanded and glued them in place with slow epoxy.

Pic 4: The CF landing gear comes factory pre-drilled and is mounted to the fuse with 5 screws. The middle one also secures a small hatch to cover the mounting.

Pic 5: I'll use a single Hitec 7955TG as rudder servo. If the power will not be sufficient, I'll add a second one. The fuse is already prepared for two coupled servos.

Pic 6: Also the provided CF tail gear makes a solid impression.

Pic 7 & 8: I already prepared the 10cm long spacers to mount the motor. Like in all my models I use turned aluminium bushings with an inside thread. The bushings are bonded in carbon tubes. To add strength to the bonding, I let the glue cure in the baking oven for about 2 hours. For my smaller 2m (75'') models I usually take a 12mm CF tube with a wall thickness of 1mm, but due to the higher power of this motor I decided to use a 14mm Carbon tube with 2mm wall thickness.

Pic 9: The Plettenberg Predator 30/8 is really impressive. It weighs about 1500 grams and has a diameter of 10cm (approx 4 inches). It is good for up to 12kw of power.

Pic 10: This is a picture of the new SLS 6000 55C cells which I am going to use. In fact of the light setup I plan to go with a single set of batteries instead of 2p in series.


Thomas

[Magne]

How many Watts do you plan to draw out of that motor with 12s6000mAh?
What sort of flight duration are you expecting?

Regards,
Magne

[bluelevel]

Hi Magne,

with that prop I expect not to draw more than 160A. Although this is a very tame setup, I still will have about 7kW. More than enough for a plane that weighs approximately 11,5kg...

I have slightly smaller planes drawing about 140A as maximum, which I fly with 12s 5000 cells. Even with those smaller packs I have run times of about 7 minutes, what is absolutely fine with me.

Thomas

[Magne]

Hi Thomas.
Thanks for the reply.
The reason for asking is that I have a 2.7m model which weighs about 14 kg with a 116cc engine, and I have considered converting this to electric.
I fly electric F3A, and have standardised on 10s packs and several chargers limited to 10s. However, I dont know if 2p (9600-10000 mAh total) would be enough, or if I would need 3p (15000 mAh total)
I see that it is common to fly F3A-X with 10s2p F3A packs, however these models are typical 2.5m and 10kg max.
(Total "tank size" in your case is 12x6=72, while I would have 10x10=100 or 10x15=150) as a rough relative number estimate.

Regards,
Magne

[lazyboyflyer]

Nice project, this plane looks better built than I expected.

[bluelevel]

Here is the latest progress:


Motor and ESC are mounted
I strengthened the bonding of the cowling's mounting ring with a carbon rowing
Two packs of A123 cells were soldered and shrunken. These will be used as as RC power supply
Receiver and satellites were mounted


Thomas

[MikeAnderson]

So whatever happened to this build thread? Did the plane ever fly this Summer?

[flyingrally]

Subscribed!

Interesting question but does the watts per pound theory still apply when you get to 3m plus sport planes ?

I've been looking at a thunder tiger 40% Katanna and wondered if it would fly with a setup similar to this ?