Hyperion Yak-55 "10" with Scorpion power system - build log - RC Groups
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May 19, 2007, 05:59 PM
ramovan's Avatar
Build Log

Hyperion Yak-55 "10" with Scorpion power system - build log

This is a build log on the Hyperion Yak-55 "10" sized 3D airplane. There are other threads on the Yak-55, but I haven't seen anyone using a Scorpion power system in one yet so I thought I would create a new thread for those insterested in this great airplane or the the new line of Scorpion brushless outrunners.

This build is dual-purpose for me. One: This airplane will be a great addition to the hangar. The Yak-55 is a beautiful well-made plane and after seeing the video I knew I had to have one. Two: I sell this airplane and all of the components that will be used. Although I have bench-tested many of these products I think it's time to do some really fun real-world testing by actually building and flying an airplane. I like to have the hands-on experience so I know what works well. Specs are great, but you never know how it's going to work until you actually use it.

First, some information on this airplane....

This is an ARF thats 98% completed and made of wood which appears to be mostly laser-cut ply with some balsa sheeting. It includes a magnet canopy for instant battery access, removable wings for easy transport and storage, tough aluminum landing gear, & high visibility striping. They are available in a blue or black color scheme, but we'll be building the black one as I think the black/yellow is looks really cool.

Airplane Specs:
Length: 806 mm (31.7")
Wingspan: 980 mm (38.6")
Wing Area: 17.3 dm2 (268 sq. inch)
Kit Weight: 340 g (12 oz)
Flying Weight: 660 g (23.5 oz.)
Suggested Motor: HP-Z3007-26
Suggested ESC: HP-TITAN-30P
Servos: 4 (2 aileron, rudder, elevator)
Transmitter: 4 channels or more

Here's the flight video that sold me on this airplane....

Here's the data sheet....

After I received my airplane I pulled it out of the box and examined everything. My first impressions were absolute amazement at the incredible detail and quality of this airplane. It is very well-made and designed. I've built many airplanes from a lot of different manufacturers and I've got to tell you this is one of the best I've seen. There's a lot of thin laser-cut ply used throughout the model which makes it very strong yet still lightweight.

The motor mount isn't just a box mounted on the front of the plane, but rather a long well-constructed unit that continues almost half way into the fuse as if it were part of the fuselage itself. It has a nice roomy and extra long battery tray that should really help when setting the CG. I was glad to see this as I had to add weight to the tail of my last two airplanes since I tend to over-power my models with the larger power systems and they had no room for moving the battery back further. There's also a lot of height area in case I decide to use a 4-cell lipo some day. The motor mount is not balsa or ply but rather a fiberglass board that seems much stronger.

The other thing that impressed me was the covering. Not only does the color scheme look great but it has been applied much nicer than I could ever do myself. On ARF's I usually have to do quite a bit of re-shrinking with the hot air gun to get all the wrinkles out and loose covering tight, but I was surpised to see how nice and tight the covering was on the Hyperion.

The cowl is made of fiberglass and is hand-painted. It's a piece of art just like they say on the data sheet. It appears to match up great with the covering both in color and alignment. The large round cowl is one reason I like the style of a Yak-55.

The plane comes packed well - I'll spare you the details, but here's how it comes out of the box....

Here's the fuelage. I've had some experience with other 3D wood models that would seem to crack and crumble every time I picked them up so I was quite pleased to see some strength here. I appreciate a light airplane, but not to the point of being overly fragile.

The hand painted fiberglass cowl is beautiful and has louvers molded in. The paint and striping are a good color match to the model covering.

Randy Moody
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May 19, 2007, 07:05 PM
ramovan's Avatar

The power system

For the power system I'll be using a Scorpion 3008-28 motor, Scorpion 35A ESC, and a X-caliber 20C 3-cell 11.1v 2200mah lipo battery. The total weight of these components with all the required connectors and mounts is just under 12oz. It will produce 43.88oz of thrust with an APC 10x5E prop and pull 23.52 amps at full throttle. I'm using the 35A ESC as I want the extra flexibility and power rating in case I run 4 cells instead of 3. Besides, it's usually a good idea run a higher rated ESC to keep things running cool.

I really like to over-power my airplanes and since this is a Sport and 3D capable model I want it to have lots of available power. I'm building this on the heavy side by using the highest capacity battery recommended but I will be flying this more as a aerobatic sport plane rather than 3D. Still, with such a long battery tray in this plane I should be able to use a 1300mah battery for those days when I feel like doing some 3D maneuvers.

I was thinking about using a Scorpion 3014 series motor but decided against it when I saw how tight the fit was going to be. The 3014 motor would have ridiculous power in this plane with a greater than 2:1 thrust ratio at 52oz of thrust with a APC 11x5.5 prop. Since I would have had to do a lot of cutting on the airplane's mount to fit this motor and deal with the heavier weight I decided to use the 3008-28 instead. This motor is still going to provide insane power - 44oz of thrust on this 25oz airplane.

Lucien from Innov8tive Designs (www.innov8tivedesigns.com) was very helpful as always in helping me choose a good power combination. The prop charts that Lucien makes by doing real-world bench tests on a well controlled set up are an incredible help when trying to find a power system for a new plane. They have all of the important specs and information available with a level of detail you just don't see with other motors. This way you know exactly what you're buying and how it's going to perform. He is a great resource if you need help choosing a Scorpion power system. Check out this thread if you have questions... https://www.rcgroups.com/forums/showthread.php?t=660918

Here is the chart Lucien posted on the 3008-28 brushless outrunner
May 19, 2007, 07:38 PM
ramovan's Avatar

The Radio System

For the radio I will be using a Futaba 7CAP 7 channel computer radio, Hitec 5 channel Micro 05S receiver, and 4 Waypoint 060 6g servos. The 5 channels will allow me to use flaperons with differential on the up-down throws or at least let me trim out each aileron individually. I chose the recommended Waypoint servos because they are smaller and lighter than Hitec HS-55's that I normally like to use and will fit in the plane with very little work on sizing the servo mounting. HS-55 servos would also work well on this plane, but there would be a little more cutting involved.

I'm going to install a spinner on this plane to make it a little more sexy. I chose the 44mm aluminum electric spinner from MPI. It has a nice mirror finish - if you look closely at the picture you can even see a reflection of the camera mounted on a tripod taking the picture.

Thats about it for the main components. Time to start building. I'll post more on the progress and take some final pictures and video when the airplane is completed.

I welcome your feedback and questions.
May 19, 2007, 11:49 PM
Registered User
hemituda's Avatar
Sounds like a great set-up, although be very careful while flying as it gets a bit unpredictable at the weight that yours will come in at. The video sold me as well but that is an awesome pilot making a sport plane look like a 3d machine. I initally flew mine at 31 oz and it snapped like mad if you got it slow but when I changed to a lighter set-up(23 oz.)it flew like it should, a capable imac practicer.

Just my .02
May 20, 2007, 03:58 PM
ramovan's Avatar

Believe me, I don't expect to fly anything like the guy in the video! He's obviously far beyond my current skills. I know this airplane won't be the best 3D flyer, but I plan to fly it more as a sport plane anyway. I hope the final weight will be 26oz. The kit is 12oz and the power system is 12oz so it should be close. I agree, if it ends up at 31oz it's not going to fly well. I'll take a final weight when finished and let you know where it ends up.
May 20, 2007, 05:26 PM
Registered User
Hi Ramovan,

I have flown the 3D profile version of this plane and can verify that the build quality of Hyperion products is first class. Yours should be an interesting build and I will watch this space with great interest.

I hope you don't mind me saying this, but I would NOT recommend those particular Waypoint servos at all. I tried them once and had one strip the gears before the plane left the ground. Sent the whole lot back and bought Hitecs instead. They are much better servos.

The Waypoint specs read just fine but the geartrains are weak. It's your choice of course but if it were my plane I would go with Hitec HS55's or my personal favourites the HS65HB - 11g, ballraced output, karbonite gears, quicker and higher output. Also available with high torque metal gears HS65MG for the same weight.

The HS55's should fit just fine, but the HS65's are slightly bigger in the casing. It depends whether you consider the weight difference to be a disadvantage. If so, go with the 55's.

Good luck with your build.


Last edited by vpp; May 20, 2007 at 05:40 PM.
May 20, 2007, 06:41 PM
ramovan's Avatar



Good feedback on the servos. I too like to use HS-55's in most of my airplanes. I have not used the Waypoint 6g servos before which is exactly why I am using them on this build. I want to know if they are any good by putting them thru the paces. If they don't perform well or the gears strip it will be important to find this out. One deciding factor for me was the size of the servo. They are a bit smaller than HS-55 servos and fit in the wings without as much cutting. I use Waypoint 9.2g servos on my T-rex 450 and have been really happy with them. The Waypoint 6g servos are a lot smaller though and their smaller gears could be a problem to watch for. I'll be pretty hard on them in order to find out.

May 20, 2007, 10:12 PM
ramovan's Avatar

The Wings

The Documentation
The instructions that come with this plane are pretty good. If you've built a few models with broken-english instructions you'll appreciate the correct spelling and sentences that actually make sense. However, there is very little text present or needed in the well-illustrated simple instructions. If you want to do some heavy reading you can check out the manual which has some good information and a lot of text on the building of the airplane.

The Wings
The ailerons are glued to the wing using three CA hinges. The ailerons didn't need any work to be a nice fit. Next I cut the covering where the servos and control horns would be installed and easily fed thru a 12" servo extension. The Waypoint 6g servos are very small but you still need to make the servo mount a tiny bit wider and a little longer to fit these servos. You'll have to do more cutting yet if you want to install HS-55 servos. I just shaved them a little bigger with a x-acto knife. I used the screws that came with the servos to secure them in the wing. I like to use screws instead of glue whenever possible so I can change them later if there's a problem. I was pleased to find there was some good thick ply here and the screws really anchored in well (it's the little things!).

I was not impressed with the wooden control horns that came with this airplane. I really didn't plan on using them but after I saw how nice they fit I decided to go with them. I wasn't wild about the way the horns look on the other side of the control surface but I guess this isn't a scale build anyway. You also only get one hole in the horn for the control rod but that didn't bother me as I tend to make my adjustments on the radio rather than the plane. I may use a black sharpie on the horn anchor so it's not so noticeable.

I used Du-Bro E-Z connectors on the servo control horns so they would be easy to adjust. It all turned out pretty good and was really easy.

Here's the wings with servos, linkages and extensions installed.

I was really happy with the nice fit of the servo in the wing.

The other side of the wood control horn is not pretty.

RC Dude
May 21, 2007, 07:40 AM
Registered User
Hi Ramovan,

The control horns are quite adequate for their job. I have a PA Electric Shock that uses carbon fibre ones, and honestly it doesn't make any difference that they are plywood.

Interestingly, they don't protrude through the Yak 55SP 3D profile kit like they do on your wings.

A tip I picked up from another post said that in order to get maximum affectiveness from the control surfaces and to prevent tip stalling (most important) they should be taped to prevent air passing through the gaps. I use "Blenderm" surgical tape for this on all my models. It will not crack with use and remains flexible with age.

Good luck with the servos.


May 21, 2007, 11:25 AM
ramovan's Avatar

Servo horns

It doesn't bother me that the control horns are made of ply as they don't seem fragile at all. I just think they are a little ugly on the other side on the control surface. If I did it again I would probably just cut the horn so it didn't potrude thru the other side. They fit tight and there is so much surface area to glue that it's really unnecessary to have that archor on the back.

I decided to cut off the excess potrusion on the other side of the ailerons and black them out with a sharpie. It's much less noticeable now so I'm happy with the control horns.

May 21, 2007, 04:34 PM
Registered User
Ramovan, sorry for getting a little of topic here but Id like to say thanks for the great service. Your prices, quick order processing and extremely fast shipping make you one of top online stores for my R/C needs.
Keep up the great job!

Ralph P.
May 21, 2007, 06:33 PM
ramovan's Avatar

Customer Comments

Thanks Ralph,

You can be off-topic as much as you want with comments like that! I'm always amazed how many customers go out of their way to tell us about how quickly they received their order. I know when I order something on the internet I hate the waiting so I always try to ship orders ASAP and use priority mail. Sometimes this means an extra trip to the post office but it's a day less you have to wait for your stuff.
May 21, 2007, 10:06 PM
ramovan's Avatar

The Tail

Elevator and Rudder
Next in the instructions was to install the elevator and stab/rudder on the tail and CA the hinges which you do after they are installed. The covering on the elevator and stabilizer needed to be removed where they would be glued into the fuselage. This is easier said than done since the covering is really bonded to the wood. I used 5-minute epoxy to glue them in so I would have time to adjust the elevator for proper alignment. The way these install in the plane makes it virtually impossible to not turn out perfectly perpendicular. No triangle needed.

I then installed the pushrods and control horns which I "painted" black with a sharpie. Before installing them this time. BTW Dave the horns potrude a lot on the other side because I was supposed to use one of the wooden anchors on BOTH sides of the horn. I didn't see much advantage to doing this as the horns are already really anchored. But if anyone is really paraniod about control horns popping off you could use anchors on both sides.

Tail servos
The servos for the tail are located inside the airplane which I really like. I know that servos mounted outside on the back, closer to the control surfaces might give better response, but I just don't like the servos hanging out there detracting from the scale look. The tubes for the pushrods are cleverly mounted. Instead of being anchored in one spot they are in slots that allow you to mount your servos any way you want. Plus the pushrod is able to move with the servo which makes even less resistance on the control. I decided to mount my servos in the middle of the tray with the arms to the outside as this makes the pushrod an almost completely straight shot to the control horn. I had to dremel a shallow notch in the middle of the mount to fit the 6g servos. I'm using the outermost hole on the control horns as I want full mechanical movement which will later be tamed by the radio programming (rates/expo). I used Du-Bro E-Z connectors again for easy adjustments.

The tail was really easy to install.

Here's the control horns and pushrod connections.

The rudder and elevator servos. Notice the slots for pushrod side-to-side movent.
Last edited by ramovan; May 21, 2007 at 10:54 PM.
May 22, 2007, 12:05 AM
ramovan's Avatar

The Landing Gear

Main Gear
The main landing gear is aluminum and mounts with three wood screws in holes you have to drill. The wheels that come with the kit are smaller than what I would have liked. I normally fly at a club field with a grass runway and larger wheels would really help the roll on take offs and landing. I'll see how it goes and put some larger wheels on if needed. I don't think this airplane will need much runway anyhow.

Tail Wheel
The kit comes with a small wire tail skid that didn't impress me much so I decided to install a small Du-Bro steerable tail wheel instead. It's still not going to taxi that well on grass runways, but it looks good and keeps the tail off the ground. I was actually surprised how easy this was to install. I used 2 tiny peices of ply, stacked, and made from the control horn scrap to bridge the gap from the wheel's control arm to the rudder. After the glue dried I tried the rudder pushrod and didn't really notice any more resistance from adding the tailwheel.

The Mains

The Tailwheel

The close-up

Randy Moody
May 23, 2007, 01:40 PM
ramovan's Avatar

The Power System

In order to fit the motor into this airplane you'll need to make the center hole in the front of the motor mount a little larger to allow clearance for the motor's retaining collar. It's a tight fit getting this motor in, but once installed there is plenty of room. As you can see in the pictures I spray painted the front of the motor mount black. This way it will look a little better when staring into the cowl. I may glue a print of a radial engine on the face if it looks OK.

I mounted the ESC on the motor mount with some thick double-side foam tape (to dampen vibration) and loose zip ties. This way I'll get good airflow running over the heatsink. The 35A ESC should run really cool since I won't be pulling more than 25A max.

I glued a strip of velcro on the entire length of the 3-cell 2200mah battery and glued a small peice of velcro in the middle of the battery tray. This is just to keep the battery from sliding around. Another velcro strap keeps the battery secured to the tray.

The ESC looks good here and should have good airflow

There's plenty of space after you get the motor in.

The complete power system installed


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