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Twisted Hobbys - Crack Yak-55

It's winter here on the homestead and Christmas is just a couple of weeks away.  Other than a couple of days last week that were unusually warm, which allowed some last minute flying time, my RC flying is on hold until this coming spring.  That means it is time to catch up on a few write-ups I'd put on hold.  It also means the winter build projects will get some bench time too. 

I wanted to try some outdoor 3D flying this past summer so I bought another plane from Twisted Hobbys.  It was the 32" Crack Yak-55 Standard and my second plane from them.  The Twisted Hobbys Crack Yak-55 Mini, the 24" model I had for indoor flying, wasn't doing it for me when I tried to fly it outdoors unless there was close to zero breeze.  Typically, that doesn't happen very often here in northern Minnesota.  The 32" Standard model would be a better candidate for outdoor flying.  So I bought it, assembled it, and really enjoyed flying it.  This write-up includes my comments and photos concerning the CY, as it is commonly called on the forums.

This write-up is not intended to replace the TH owner's manual which provides excellent instruction on building the CY.  In addition to that manual, there is great user community support on the RCGroups online forum too.  If you are considering the purchase of a Twisted Hobbys kit, read the RCGroups support thread for that particular model.  The links are provided for the various models on the TH website.  Some of them are very lengthy but worth the time, especially if you have extra time like I do during the winter.


Crack Yak-55 on the build board

If you are not familiar with Twisted Hobbys' line of planes, you will find that most of them are profile planes.  The CY-55 Standard is shown in the above photo and is nearly completed.  The X shaped body provides the basis for a strong and lightweight aircraft.  The lighter the aircraft, the more floaty it is and easier to perform 3D maneuvers.  Carbon fiber is routinely used for such components as control rods and landing gear.  Some of the structural spars are also carbon fiber while others are made from wood.  It believe that a balance between strength, performance and cost weighs in on the decisions made as to what is used.  All of the planes that I've looked at are made from EPP foam.  EPP is much more durable than the commonly used EPO foam used in many RC aircraft.  That doesn't mean you can intentionally abuse it, but it certainly does survive better when unexpectantly hitting the ground .  It can be quickly repaired in the field with CA glue which can be a plus if you are flying in a competition or you have a grandkid that wants to keep flying. 

Twisted Hobbys kits do not include electronics.  They do offer a "power combo" which consists of recommended parts that usually include servos, motor, ESC, and a propeller.  Each of the items in the combo pack can also be purchased individually from TH at a slightly higher price.  You can also source your parts from other vendors.  If you have a well stocked parts bin, you may have some or all of what is needed.  The TH website provides the information you will need to determine what is needed to complete your plane.  The forum users can be a very good source when looking for suitable substitutes. 


servo specs

The above photo is a screen capture of the specs of one of the servos used in the CY.  It was obtained from the TH website.  I'm not claiming that all of their parts have the specs posted on their site.  However, for those that do, it makes it much easier if you are sourcing your parts from another vendor.


Crack Yak-55 servo install

The Crack Yak-55 uses three servos, one for the ailerons and the other two for the rudder and elevator.  TH provides nice clean foam cutouts for locating the servos.  I use a couple drops of hot glue on my EPP boam builds for keeping the servo in place.  Should I need to remove them, a little bit of isopropyl alcohol helps to loosen the hot glue bond. 


Crack Yak-55 2305 1500KV motor

 Here is the Crack Series Pro 2305 1500KV motor mounted on the CY.  I don't know where TH gets their motors but they are branded with the TH name.  They pulls strong and this one is spinning the recommended EP 9x4.7 prop.  The motor comes with an installed prop saver.  The round bands are available from TH but I get mine from the local hardware store at a cheaper price.  I've not noticed any difference in performance.  The motor is screwed (screws supplied) to a fiberglass firewall which is glued to the nose of the plane.  After the glue had setup well on the firewall, I applied some more (I use Foam Tac) on the foam surface around the firewall legs and then overlapped surgical tape across each leg of the firewall.  This makes for a very strong mount setup for the motor.


Crack Yak-55 landing gear wheel

I'd read a number of forum comments regarding the installation of the landing gear.  Some folks install it, others do not.  You can see that the tires are very small.  I can see where they could work on a hard surface but certainly not the front lawn or a grass runway at the flying field.  I fly on everything except hard surfaces.  That being said, I decided to install the landing gear in order to keep the prop out of the dirt/grass when landing.  (I'm not good enough to grab the plane out of the air.)  To land, I hover at a high alpha with the tail nearly touching the ground, then cut the throttle.  It gently plops onto the ground, safe and sound.  One forum commenter mentioned that having the landing gear installed provides leverage such that a ground strike can rip the foam where the gear is attached.  Well gues what?  Yep, that will happen....but nothing a little glue won't fix.  I have a 39" TH plane sitting in the box waiting to be built.  It's quite possible that its gear will not be installed.....depends how it responds to getting the CG set correctly it it isn't on the plane.


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