JC's Planes and Projects

Foamyfactory.com Yak-54 with Himax brushless motor

Specifications:

Wingspan: 40 inches

Length: 37 inches

Wing area: ?

Weight: 13 ounces RTF with 3s1p Etec 1200 battery.

Transmitter: Futaba 8UAPS

Receiver: Berg “Micro Stamp” 4-channel

Servos: 3 x Hitec HS-55 servos for full four-channel control.

Power: Himax 2015-4100 with GWS “D” gearbox. ESC is a Castle Creations Phoenix 10.

Prop: GWS 12x6

Finish: Poly tape and Monokote trim sheet in a Sukhoi scheme. Yeah, yeah, I know that it is a Yak, but I only had one roll of color tape. The next one will get a nice multi-color Yak scheme.

Features: Landing gear with GWS wheels. Dubro micro hardware used instead of pull-pull. Himax motor was shimmed for GWS gearbox using a Cobri products shim from eflightline.

If you are a regular visitor to the “3D” or the “Foamies” discussion boards on the Ezone website you would no doubt have seen the record-setting threads on Tim Hart’s fan-fold foam designs. I say record-setting because the webmaster has to retire the threads after they get too many posts. I think that at last count they had retired four or five threads each. This is testament to the excitement Tim’s designs have created.

The designs have flat profile wings and fuselages and use fan-fold foam for the structure. Fan-fold foam is an insulating material sold under different names by several manufacturers but the Dow Bluecor sold by Lowe’s is the most rigid and durable. Even better is Depron since it is lighter and even more rigid. Unfortunately Depron needs to be ordered from an online source since it is not used as a building material in the US.

I went to Tim Hart’s Foamy Factory website and read up on the designs and power systems. I also downloaded the videos and was very impressed with the simplicity and performance of the designs. Tim has free downloads of plans for an Ultimate biplane as well as a 3D machine called the 3DX. I chose to purchase and download the Yak-54 plans for $12.00 because it was the newest design and looked cool. Tim now has an Extra design available as well. I am sure that there are a lot of people willing to email you the plans for free. It is just a PDF file. I chose to purchase my plans because I really appreciated the work Tim put into the designs and his website. He is not getting rich at $12.00 a pop but, as he says, it gives him the pocket money to buy new equipment. If you can afford it, buy the plans and support this modeling innovator.

The plans are just a file that can be taken to Kinko’s and printed full size for around $6.00. Once you have the plans printed it is just a matter of tracing them onto the foam and cutting the parts out. The aesthetically-minded modeler will want to remove the black “Dow” markings from the foam. This can be done with denatured alcohol and a little rubbing with a cloth.

The fuse and wings are strengthened by 4 mm “pultruded” carbon fiber tubes. These tubes are available online for about $3.00 each depending on length. There was a big run on these tubes and Tim’s suggested vendors were sold out. I did find the tubes in-stock at Goodwinds Kites in Seattle. I imagine that everyone is re-stocked by now. I used epoxy to glue my tubes to the wing and fuse. However, Renaud has had good results using the foam-safe “odorless” CA adhesive. This will speed things up and save some weight. I used hot-glue for affixing the foam parts. I bought a dual temperature mini-gun from Michael’s in Ann Arbor. Using the “low” setting you don’t have to worry about melting the foam. I think it was $6.00 for the gun and $2.00 for a bag of glue sticks. Quite a bargain!

I used Hitec HS-55 servos for all surfaces and they have worked great. For surface actuation I used the new Dubro micro hardware. They offer micro pushrods and sleeves, control horns, easy-links, and screw-lock connectors that are ideal for this application. The plans call for a pull-pull system, but most people are finding that method frail and cumbersome to adjust. I recommend pushrods.

To give your model a nice scheme I would recommend using poly tape. This is the same tape that has found great acceptance for decorating the Zagi electric wings. I only had one color of tape and did a simple Sukhoi scheme. For my next design I wanted something more colorful so I ordered a box of tape from Fast-Pack. They have a sampler box of tape with every color under the sun for about $13.00.

The power system consists of a motor and a GWS EPS-350 “stick-mount” gearbox in the “D” gear ratio. This gearbox mounts to a 3/8” square hardwood stick. The gearbox is very simple and you can buy spare parts online for just about any piece for about $2.00! This will come in handy if you strip a spur gear or bend a shaft. I bought all of my GWS gearbox stuff online from AlleRC.

I originally used the stock GWS 370-sized brushed motor for power. It is probably a 6-volt motor and I was running it on an 11.1 volt Etec Lithium-Polymer (LiPo) pack. It lasted exactly two flights. Time to go brushless! I purchased a Himax 2015-4100 motor and a Castle Creations Phoenix 10 ESC. This combo is priced at around $100-105.00. Not bad, huh? I pressed a GWS “D” pinion onto the shaft of the Himax with no problems. The Himax is a little smaller in diameter than the GWS brushed motor, so I purchased a round plastic Cobri Products plastic shim online from Eflightline. The shim does a good job of stiffening the mounting of the Himax motor as well as aligning it in the gearbox. Note that I had to hone the inside of the shim with a sandpaper hone to be able to fit the Himax in. With care you can get a nice interference fit. I completed the power package with a big GWS 12x6 propeller.

To keep weight down, and to play with the latest in receiver technology, I used the Berg “Micro-Stamp” 4-channel receiver. This thing is tiny and very light. I think the antenna weighs as much as the RX! The Berg is a single conversion RX, but unlike other single conversion RXs, it is full-range. It has worked flawlessly for me so far.

Flying the Yak-54

Before test flying I programmed the Castle Creations ESC for use with a three-cell pack of Etec 1200 mah LiPo batteries. This ESC is amazing! It is tiny, yet you can program it for voltage cut-off, soft-brake, and other parameters. It was the dead of winter when I finished my Yak and outdoor flying would have been brutal. I fashioned a set of landing gear and used a Dubro Micro tail wheel unit and GWS wheels. I was soon taxiing around my basement anticipating the maiden flight at the Oakland Athletic Yard. The maiden flights indoors were a blast – only two collisions with a GWS Slow Stick resulting in a couple of “battle scars” from the propeller.

Performance is amazing! Want unlimited vertical? This ship has it. The Himax puts out an amazing amount of power for its small size and weight. It generates about 26 ounces of static thrust on a 13-ounce airplane. This gives the 2:1 thrust to weight ratio that 3D flyers demand. The 3s1p Etecs handle the Himax current load very well. I use max power only in short vertical climbs or to get out of trouble. The ship will hover at half-throttle so duration is not a problem. I have had 18-minute flights with ample hovering and towering vertical punch-outs.

The Yak can be mild or wild depending on how you set it up. Crank up the control throws and move the CG back and it is ready for 3D moves. I am no 3D ace, but I can boldly practice new maneuvers on the Yak. It is very lightly loaded so things happen slowly and it gives me time to think. It is also crash-resistant and easily repairable when the inevitable does happen. In short, it is the ideal fun-fly and 3D flying machine. What are you waiting for? Build one!

Online resources:

www.foamyfactory.com : Plans, instructions, vendor lists, etc.

www.depronusa.com : Source for Depron foam

info@goodwindskites.com : Source for 4 mm carbon fiber rods.

www.Fast-Pack.com : Source for colored packing tape

www.allerc.com : Source for Etec LiPo batteries, Himax motors, Castle ESCs, and GWS parts.

www.e-flightline.com : Source for Cobri gearbox shims, Himax motors, ESCs.

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