|Jul 24, 2014, 09:22 PM|
Twisted Hobbys 39" EPP Crack Yak
Introducting Twisted Hobbys' newest addition...
.... the long awaited ....
39" Crack Yak !
The 39" Crack Yak-55 is finally here... the long awaited bigger brother to our well known Crack Yak-55 model. New wing core with tapered tips is one of the new features creating a much larger flight envelope for strong wind capabilities. Other items include added T-Canalizer and new SFG placement for amazing KE stability at any alpha. This is a fresh new ground up re-design. Chris Jewett's original world renowned 32" Crack Yak-55 has been our go to foamie and it is now crafted into a larger size for an even more intense flight envelope.
Those that are familiar with the previous 39” models will appreciate the new hardware and construction methods with adjustable push rod assemblies EPP bracing techniques for easy assembly. While creating a new ground up airframe the duel aileron servos were re-located to create a plush/clean look. The over all flight envelope has increased greatly giving a sense of unreal control authority and increased roll rate was also achieved with the addition of outer counter balance tabs. This model was designed for the pilot wanting to learn the “next step” and also those who choose a balsa 3d model alternative.
• Wing Span = 39"
• AUW: 375-390g
• Full EPP construction
• Carbon Fiber landing gear
• Extra-large control surfaces
• Incredible control authority
• Extreme Free Style Performance
• Ideal 3D trainer
• EPP Durability.
Recommended Required Components:
• 45-55g 1000kv brushless motor
• 20-30A ESC
• Micro Receiver
• (4) 10-16g Servo’s
• 10x3.8/10x4.7 Slow Fly Prop
• 3s 600-1200mah Lipo
Available Now at the Twisted Hobbys' Website
Grey - http://www.twistedhobbys.com/RCF-39-...ak-55-Grey.htm
Green - http://www.twistedhobbys.com/RCF-39-...k-55-Green.htm
|Jul 24, 2014, 09:23 PM|
Build Highlights - Tips & Tricks
Stay tuned to this post. As mentioned in the owner thread, this post will focus on the finer points, things to look out for, things experienced builders may prefer, etc.
As with all the Twisted Hobbys planes, this one is no exception in regards to quality, completeness, build fit up and ease of assembly. I am hopeful that everyone enjoys the build as much as I am.
Except for the following items, this airframe builds the same as the 39" 540 Edge, and that manual should be used.
1.) The Canalizer.... glue it on at the end when you do the Side Force Generators
2.) The Inboard SFG are not tabbed for location and should be located approx. 2.50" from the outboard ones, not this is not super critical. Notice however that they are not symmetrical, the bottoms have a bigger chamfer to clear the ailerons at full deflection.
Things to take note of:
1.) Rectangle Spar .5mm x 3mm x 500mm is used t stiffen the fuselage, it gets glued into the precut slot.
2.) Tail push rods are 1mm dia. round carbon
3.) Aileron push rods are 1.8mm dia. round carbon
4.) Wing Spars are 1.5mm dia. x 800mm long round carbon
5.) You can glue the wings on upside down if you are not paying attentions. With the servo cut outs in the horz. fuse section facing up, you should be looking at the bottom of the wings.
6.) Make sure and leave a gap on the rudder... it is okay to bevel it if you want, but it is not necessary. If you do bevel, there will be a slight misalignment at the front edge.
7.) Wing Spar... test fit all the pieces and make sure that the center wood piece is centered in the thickness of the wing so that the 1.5mm round carbon rods still have room to be buried as well.
8.) Do the Blenderm thing for the inboard and outboard ends of the ailerons
Center of Gravity - Approx. 1.25" to 1.50" inch behind the Spar
ImagesView all Images in thread
|Jul 24, 2014, 09:26 PM|
Hi Guys, sorry for the delay but right after we got this plane in I headed up to WI for the EAA Airventure and haven't had a moment to think RC since Now I'm back home and ready to go again!
So, we have been working on a larger Crack Yak (CY) for a long time. One of my main problems was that I didn't want to make a larger CY just for the sake of making a bigger CY. In my mind we had to have some benefit to going bigger and in some way improve on the original design.
What we found in trying to do this was that if we went too big it became less durable and it was difficult to keep the wing loading high enough to fly like we like the CY to fly without making it look like another plane. We also found out that there wasn't a huge improvement in performance with going larger unless we added an airfoiled wing. With the airfoiled wing the plane rolled better, was more precise, tracked better and penetrated better.
What took us a while to figure out was exactly what size produced the best benefit while maintaining durability and how to produce an airfoiled wing in the size we wanted without making it too costly or difficult to build.
That's how we got to a 39" CY. It is large enough to benefit from the airfoiled wing and small enough to remain nearly as crash resistant as the 32" with the added performance traits of being more precise, tracking better, rolling better and flying more like a balsa bird.
We made a few other tweaks to the airframe shape and also added an optional Cannalizer. The Airfoiled wing and size allowed us to take a little of the instability out of the plane while maintaining the same amount of control authority, if not more than the original.
What we are left with is not only a larger CY but a better CY in my opinion. Yes, for cost, durability and as a first 3D plane you will probably still want the 32" but for all out performance and balls-to-the-wall insanity, the 39" is the ticket!
BTW - the 39" power system is very efficient and crazy powerful. You get the same old CY crazy power and long, long, flight times on a 750 3s..
Now, I am going to go fly mine some more.... Happy flying
|Jul 25, 2014, 08:12 AM|
Awesome videos Chris and Benton. You guys make it look so easy .
How would you describe the main differences compared to the 39" Edge?
PS Excellent choice of music Benton, Oasis right? DS
|Jul 25, 2014, 08:18 AM|
I wanted to give my flying impressions of the new crack yak 39" from flying it for the first time yesterday. After the first 15 seconds, I told my Dad "wow, this thing flies great!" The first thing I noticed was how it tracked, not much movement just stable. The roll rate is pretty ballistic. The hover is pretty hands off. And the knife edge did not require hardly any rudder at all. There was plenty of power to do rolling loops. This plane has good handling at low speed and high speed handling as well. This is a beginner or advanced plane. I even think that the larger planes like this one are easier to fly. The plane I was flying was on the stock power combo( TMW 2212-970) This motor is awesome, which is running a 10 by 4.7 prop. I also was amazed at the flight time I was getting on the batteries. My build position the battery directly over the spar. I used 3 cell batteries. The Twisted Hobbys brand 750 mah and 850 mah were used. I really couldn't tell the difference between the two. I noticed after flying for 5 minutes I still had 50% of the capacity on the battery tester, meaning I could have flown for minutes longer. I look forward to many more flights with the new Crack Yak.
I want to thank the Twisted Team for designing such a great plane. I can not imagine how much time goes in the works for a new plane. I also want to thank my Dad and Grandpa for their help too.
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