HobbyKing Yak55 44.4" EP (new thread) - Page 2 - RC Groups
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Dec 06, 2012, 08:28 PM
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Just found this thread, nice build. Actually, I just finished and maiden my Hyperion Yak 55sp 58". It came from the same Chinese factory (Haikong Model) as your HK one. But allerc.com has it on sell for $127 and free shipping! I use 5055 kv 580 with falcon 15x7 on 6s 3300. What a great 3d flyer! She can also slowdown like crawling. The quality of the ARF is no less than my 3dhs or EF planes except the LG mount. On my second landing, I landed it like a feather on rough grass field btw, the right LG bent and torn out the mount. Upon inspection I found the designer chosed two 3/32 plywood glued together for the lg mount plate, but cut many holes on them to save weight, which is a very bad idea for a 5.5lb plane. No fiberglass or carbon fiber reinforcement on either side of the plate, so, one small bump on the field resulted a torn LG plate along the cut-outs. I replaced the whole mounting plate with solid 1/8 plywood with 1mm carbon fiber reinforcement, now the LG is rock solid. I would suggest you look closely to the mounting plate as well!

Good luck to your build and maiden!
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Dec 06, 2012, 10:21 PM
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Thanks Vince!

I appreciat ethe comments. The plane is coming along nicely now... except that my wing mount screws don't go more than 1/4" into the wing, and are not in enough to hold the wing!

I may try using a plier to turn it, but my guess is that they have something inside the threads that are blocking them. I may just get a 2.5-2.6mm cap screw and mount it inside with epoxy instead... I gues that U should have checked this, but I never expected that!

I also just realized that with my mods, my CG is a lot closer to the middle of the plane than I initially expected, though even with some of my mods, there's NO way that a battery can fit into my plane (a 2200mAh almost does, but not quite!) I am going to have to probably go with a set of two 1300 3S batts in parallel, or go with two decent 2S units in series.

I hear you on the gear - my new CF gear is great, and I internally reinforced the gear plate using CF rod, epoxy and some balsa blocks (pre-hardened with CA). It should withstand a lot now - since the plane should only be around 1/2 your AUW.

Does your plane balance the CG very nearly on the wing spar (ROD) position? my tubing that joins the wings seems to be that way. Also, do you recommend just epoxying the wing and be done with it? I may do that too, but I sort of like the option to remove wings when travelling.

Thanks again. More photos on the way when I am finished figuring this quandry out!

Dec 07, 2012, 01:55 AM
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ALMOST done... test fit wings and throws again

Below are the pictures of the new Yak 55 sans spinner (stuck in the mail still!)

But all the hookups are done. Just have to clean up the wiring a bit, and figure out a few layouts for batteries, and fully attach the wings.

This plane has a LOT of throws on the control surfaces, so I set 50% for low rates (63% actually, 1/2 of the 125% I'm running the servos at on high rates).

This plane's color scheme and layout are truly superb, IMO. I really love the color scheme and format, and I am very proud of this model with the extras I put into her, such as the vanes, and CF gear. It really looks cool on there, and gives a very stable stance now to the plane. I'm SO glad that I did it...

Dry empty weight with no batteries is about 34.5oz (975g).

Comments welcomed. I am not sure exactly when I can maiden her, as it's very cold (-18C) and very snowy. Probably a few weeks before I may be able to take her up.

*I am also deciding on battery layout - this plane's CG sits right about where the main wing joiner tube fits, 85mm aft of the wing leading edge. However, I have NO way to fit standard 2200mAh batteries in her, as there's too much cross member and stuff to permit it. Further, even if I could, I'd probably need about an extra 30-50g minimum in the tail now to balance her out. Yes, the vanes and CF gear probably added about 2oz total, but the joiner tube is sort of in the way (but has to be there!). I'll figure it out, probably 2x 1300 30C 3S Lipos in parallel.

Sky Cadet
Dec 09, 2012, 05:19 PM
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Yak55 complete - throws set, just waiting on new batts

I finally finished the build!

It turned out fantastic. A few minor quirks, but nothing too difficult to surmount. The wing blind nuts were offset by about 1/16", just enough to prevent using the thumb screws on my model. so, I used 4-40 capscrews inserted into the back side of the nuts after reaming out with a drill, then epoxied these on - ~1/2" from the wing is all that was needed, and then I used lock nuts and small washers to hold the wing.

The pins fit in well, but not totally into their slots so I used 7/64" push nuts to bite into the pins and hold them securely to the sides, and epoxied them in. The wing is rock solid, secure, and mates ideally with the fuselage.

The aluminum spinner fit perfectly, and the final static tests revealed around 360Wp Perfect! Plenty of thrust too, enough for unlimited vertical.

So, just waiting for my Zippy 1300mAh 3S lipos from HK. They'll be put in parallel, and will fit right in front of the main wing spar. Balance will be right in the 85-90mm regime aft of the wing, as recommended by the manual.

It may be several weeks before a maiden is even possible. It's cold and very snowy here in Edmonton, well below seasonal norms and more snow than we usually get in winter. Phooey!

Pictures of the plane below... It turned out very well...

Dec 10, 2012, 01:18 AM
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Looking good! The three blades porp, aluminum spinner and cowl details are so stand out! Can't wait to see your maiden video.
I flew my 55sp on Saturday, my rebuilt on LG mount passed the test! just need some sunny days!
Dec 10, 2012, 01:52 AM
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Thanks Again, Vince!

Yeah, I was pretty happy with the look of the front there! A bit of extra work, but not a lot.

It should fly great. Lots of pull on the 3S system. Empty weight is around 34oz. AUW is going to be around 42 oz.

Glad to hear that your upgraded gear worked well! I find almost every model I buy has the gear as the weak point and it always requires some form of upgrading - esp. if one flies on grass fields, like me. LOL.

Just out of curiosity, what is your plane's AUW with your 6S system there? Just curious as to wing loading and how it should compare to my "little brother". My Maiden will have to wait until our lousy winter weather here warms up a bit, probably in month or two.

Dec 10, 2012, 02:59 AM
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Thanks Vince!

Yeah, I was really happy with how the front end turned out! Thanks... The plane should weigh in at ~42oz (1190g) when all-up including batteries. It weighs around 34.4 without batts.

I really found that CF gear to be great - it is WAY better than the stock aluminum gear, and is one piece which is preferred. I always find the gear is probably the single most weak point on any model kit, and always upgrade it. I fly grass mostly, so its good to have the extra clearance and strength.

What does your plane come in at fully loaded? Just curious. These Hyperion kits (my HK kit is hyperion made too) are superb. a few minor quirks but nothing too outrageous.


Last edited by SkyCadet; Dec 10, 2012 at 03:03 AM. Reason: Thought the first replay did not show and re-did it, tried to delete this one.
Dec 10, 2012, 11:58 AM
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I just happened to weight my two planes last night.

Hyperion Yak 55: 58"ws, 57" total length, 5lb 1oz with 6s 3300. Wing area is 713 sq-in.
3DHS 59" Slick: 59" WS, 56" total lenght (strangely, 3DHS published 54" in length), 5lb 3oz with 6s 3300. Wing area is 659 sq-in.
Torque 4016 MKII in the Slick is about 1oz heavier than the Aeolian 5055 kv580 in the Yak. Otherwise every thing goes in to the two planes is the same.

Because the Yak has a fully sheeted round fuse I am surprised to see the Slick is heavier and has higher wingload. Also the motor box on Yak is definitely more beefy than the Slick's. An interesting comparison, my 42" Slick is 910g without battery (3s 1800, 145~150g), which is about the same as your 44" Yak. My Omega 103g produces the same output as your 3536, and the Slick is super floaty in the air, so, yours should fly really good. But with 3 blades, you probably will have a lot of prop torques.

I had 5 flights on the Yak so far, have not found the right CG yet. The recommended CG is very good for sport flying, but a bit nose heavy for 3D, but still she can fly in very slow. Just completed the built on the Slick, probably will maiden her the coming weekend. I built these two planes because they were both on sale earlier, but I like WS under 45" better due to transporting issue. So far I have a Slick 42" and a GP Ultimate both are amazing flyers. I am interested to see how yours fly! I crashed my Valuehobby Yak 54 a while ago and I miss a smaller Yak. Always love Yak!
Dec 10, 2012, 12:58 PM
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Thanks again Vince!

You know, when I first saw this plane (the ZH Yak 55 EP) on HK, I immediately fell in love with the color scheme, very easy to discern orientation! I had to initally get used to the Yak 55 layout, but once I did, I now REALLY love the looks of these Yaks!

I found a Realflight version that I adjusted to have similar power:weight ratio and have been flying like crazy on it! If my real Yak flies even 90% like this one, I'll be in heaven!

I think that your Yak is the 55M variant, as the canopy is not as bubble like; I understand that Yakolev made this variant after the 55 to permit a bit different performance (roll rates with slightly shorter wings for example).

Both the 55 and 55M were total trend setters - you see Sukhoi, and many other planes like these but they are NOT a YAK!

I'm probably going to target my CG for about 90mm in mine (just aft of the main spar, as the recommended CG is 85mm aft of the wing leading edge, right at the spar) to get a bit more float. Both our Yak 55 wing loadings are bang on the same within less than 1%, BTW.

It's good to know!

I'll send you a PM shortly. we should chat!


PS - smooth skies!
Dec 10, 2012, 02:59 PM
Registered User
My first 3D plane is actually a Yak54 from Valuehobby. I just love the look of a Yak, they look much better than the mainstream Edge, Extra and Slick in my view. However, I was afraid of flying the beautiful 54, so I maiden her 6 months after I built her. During that period of time, I bought two EPP Yak 54, 38" and 44" from TechOne, homemade a 32" EPP Yak 55 and practiced a lot! Finally maiden the 54 three month ago, flew wonderfully but crashed her a month later due to poor quality hardware, to be exact, the super thin, stock push rod on the elevator compromised at full speed dive. So I started looking for a replacement and found Hyperion. After more research, I found Hyperion's models are made at Haikong Model who is also a vendor to Hobbyking. But the price I got from allerc is even better than HK's offer.

I have tried but found not much of info on your 44" 55m, Hyperion had a similar product before but again, it was a 55SP. I also found that sealing hinge line is a "must" on the small 55SP to prevent sudden stall. You might want to do that as well. My "inventory" can easily fit a 55M, but I probably will wait until next spring or when HK has it stocked in the US warehouse.

Based on the 3 blades, I guess you would fly her more on the scale side. I think if you use a single 3s 1550 ~1600, she will be very floaty. However, judging by the size of the rudder, she maybe a bit handful at high AOA stuff, which is very important to me because I fly off a small school yard with heavy, rough grass. So I need to do a very steep approach and then bleed off speed with harrier before landing. My current fleet does very well in this department (of course for those weren't staying in my boneyard) So, let me know how your 55m performs!
Dec 10, 2012, 03:52 PM
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Actually Vince, MY Yak is the 55, your larger version with the sloped back taper is the 55M variant I believe. The original 55 had the bubble canopy like mine. No biggey - they're both YAKs!

Don't let the 3 blades fool you: the 11x7 turns around 7800 for approx. 5lb. of static thrust, and even if this is theoretical, I should be able to hold vertical around 60-65% pretty well, according to what I see in my other planes. Won't know until I fly her!

However, I want to run 2600mAh total in the plane. Yes, more weight, but why curtail all that awesome fun after 4-5 minutes?! I should get around 8-10 min. with general or slightly aggressive flying, and closer to 6-8 on more crazy stuff. I'm more of a sport aero guy than a 3D one, though I admit my Beast micro 3D is a lot of fun to hover!

I'm also going to install an ORX 3AS V2 unit in her to stabilize in wind; the V2 has remote on/off through a Gyro or spare channel. Should work well to hold harriers!

Jan 10, 2013, 09:57 PM
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Yak ready to go when weather warms up!

All the things needed to run my Yak are finally here. The last were a set of batteries. All tests and placement are finalized, CG is JUST at the recommended 85mm aft of the leading edge. This MAY be a touch nose heavy there, but I won't know until the weather warms enough for a maiden, probably at least 1 month away.

I am very excited! Stay tuned for developments...


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