Skyline/Goldwing Sbach 60" Build Day #1

Today the Skyline/Goldwing Sbach 342 60" kit arrived via USPS this afternoon. It took abut a week to get here from General Hobby in California. The instructions came on a mini-CD, a 12 page PDF. Not particilarly useful but some nice drawings to guide me on those parts unique to the plane. In general anyone with build experience can have this built in about 6 hours or so. Today I just did the wings and the landing gear.

The box was in fair shape with one bad puncture, but nothing damaged inside!

 

Top off un-boxing!

 

Everybody out!

 

Aileron hinged, servo installed, servo arm and control arm fitted. The control horns are sturdy fiberglass. I used Super Glue instead of epoxy. Hitec digital HS-5485hs all around. I actually centered the servo on the receiver, not just the servo tester, pirate flag installed, all set to go!

 

The aileron control rods are steel and were about 1 cm too long. I Dremeled off about 5 mm from each threaded end. The ball links need to be 108mm apart by my measure and were well over 120mm before modification. Fit perfectly after the fix with good thread engagement. I wish the rods were carbon fiber...

 

Top side of the right wing. Applied the decal and the mini pirate flag. My Brother computer printer label maker is in storage so my blog URL sticker on the aileron will have to wait...

 

Left wing same as the right wing...

Cats optional.

 

Annoyance. The letters "Sbach" are supposed to be black... This sticker is supposed to go on the white field of the left wing. It's also a bit smaller than it's supposed to be, and, well, white. I wrote General Hobby to see if they can send me the right one, but I suspect not. Trying to get one from China will not work either. I may have to McGyver something if I can't find the right one online. UPDATE: I emailed General Hobby last night and this morning they responded they are sending me the correct sheet. I realized this isn't really their problem and really appreciate their stepping up!

 

I made another modification here. The instructions called for the wheel to be held in place by an opposing relatively flat nut and a nylon lock nut, and a second lock nut holding the axle to the landing gear strut.. This did not allow for enough space between the wheel and the wheel pant in dry fit; the wheel rubbed the pant. I could have Dremeled down the pant, but I didn't want to weaken it at all, so I replaced the flatter nut with another M4 nylon lock nut I had, and the two lock nuts created a perfect fit with nice clearance for the wheel from the pant.

 

 

The wheel pant installed. Easy peasy.

 

It was late and I am in no rush, so I stopped for the night. I put all the plane parts back in the box to keep the cats from chewing on them. I finally hung the other plane and my helis up to keep them at bay.

 

Tomorrow I have to wait for the cable guy, so will take the time to do the tail assembly, including the rudder and elevator servos, and if I get time will start on the motor and electrical harness installation, install the landing gear, tighten up the cote and test everything. I could be done tomorrow!

 

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Fly Day Interrupted

We got out today, and I actually got some stick time! Kenny and I met up, and my son Aidan came out. The winds picked up quickly, shortening my flight time, but a lot happened.

You may recall that I charged my batteries a year ago, and never got around to flying, which ruined many of them. Storage charge is around 3.8V per cell... Basically post flit discharge voltage. Mine were fully charged, So I expected the batteries to misbehave. I had discharged them about a week ago, and threw out one clearly bad one, but the others seemed fairly fine when I discharged them by running them on the Pulse XT. I still wasn't sure I trusted them, and my suspicions paid off. Of the five 4S batteries I have, 2 failed in flight with faulty power performance within minutes of take-off, causing low power and a need to land quickly. Fortunately my flying fingers did not betray me and all of these shorter flights ended safely. I plan to recharge them all and ground test them this time.

 

Aidan hanging out in the pits. He enjoyed watching the Pulse XT fly and wants to come back for more! We want to get him some stick time on a trainer box, so I set him up with an Intro Pilot ticket (I am an instructor pilot). The winds were getting gusty and I wasn't ready to declare myself fully ready, even though my year off didn't seem to be a big deal in regards to my flying judgement and skills. I do need some more experience until I call myself back up to speed.

 

Kenny Chandler working the kinks out of his new Cubby gas engine. it just wouldn't behave, and the winds made him uncomfortable for a maiden. He brought out and set up his sweet Sbach, but then, dammit, dropped his JR radio snapping off he kill switch... He wisely called it a day.

 

All in all, a good day. I got four flights in, two bad battery bail outs, and two fairly nice full runs. I battled some upper gusts and managed not to lose the plane. All of my landings were pretty sweet. I remembered why I had spoilerons set up as the Pulse loves to float in ground effect, so I took the flaperons out and reset them as spoilerons again, but I didn't get a chance to try them out. I am glad to have loosened up my flying fingers and got my jitters aired out! Can't wait to get out there again!

 

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Cat-nab-it!

Damn cat... Good thing she's cute. The other day a cat chewed my wood prop, and last night a nylon one I replaced it with. This morning my wife was brushing her teeth when she heard crunching! Caught Neko, my 3yo Siberian, munching on the left horizontal stab! we suspect she did the props. I did a quick repair this am, not my bet work, but then I suck at cote work...

 

Cat chewed the corner. I have cut out the flattened most chewed part and removed the damaged cote, didn't think to take a pic first. You can see teeth marks...

 

Another look. Still peeling the cote.

 

I didn't have any balsa, as most of my RC stuff is in storage. I McGyvered some cork. Super glued it to the corner.

 

Sanding it down.

 

Smoothed out.

 

Done, re-coted. Not my best work. The same mismatched yellow as on the other side, so now they are balanced.

Kenny and I planned to fly today, but the field is really wet and he's buried in have-to's. I may go this afternoon, but we are certainly flying tomorrow! I expect the Sbach 60" to arrive any day now. The servos came yesterday, so I now have everything I need but the airframe! I hope to have it all together and ready to maiden by this weekend. I hope to have my flying thumbs back in shape by then.

 

Now, to hang the damn plane away from the cats!

 

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Skyline Sbach 60" Electrical System

 

I soldered and made the electrical connections on the Sbach's harness today, and programmed the ESC. One of the reasons I chose the HobbyWing FunFly ESC is that I have HobbyWing programming cards. I hate and never have programmed an ESC via a transmitter. The card is so frickin' easy and they are cheap. I just wish there was more homogeneity in programming so a universal card could be used for all ESCs.This motor is the biggest one I have ever used (as is the battery)!

 

 

This is the entire harness, albeit without the servos. I bound the reciever and tested the motor figuring t which motor wire went to which ESC wire for the proper motor rotation.

Everything took about an hour! Now I just wait for my aircraft kit to arrive, and the servos. Yay!

 

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IRCHA 2014 Registration is Open!

 

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Must. Resist. Spending.

Weather sucks... Has for days. Already gusty outside, ground is soaked from torrential rains. Doesn't look good until Wed... Agita. Must. Fly. Something.

 

 

 

 

 

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Sbach Power Calculations

I did some power calculations using 6S and various prop configurations using eCalc. I estimated the built up weight at 2500gms, and put what I think is my motor in the calculator (went back to do another 8S calculation and that motor choice was gone.... Odd). The simulations seem to make it clear that 6S will be more than powerful enough, giving in excess of a 2:1 thrust to weight ratio. Turns out 8S is likely to over amp the ESC and is waaaaay more power than it needs. It also is clear that I chose a good prop at 17x7 (though a 16x10 would give a nice increase in thrust I think is overkill). Guess I could have gotten a cheaper amp if I had done the calcs first, and not bought a HV ESC...Click the images to enlarge.

Power Setup:

Motor: Turnigy Aerodrive SK 5055-430kv

ESC: HobbyWing FunFly 80A HV

6S, 17x7, 60 amps, 1244 watts, 89.5% eff, 5497 gms thrust

6S, 16x10, 65 amps, 1346 watts, 89% eff, 6377 gms thrust

8S, 17x7, 94 amps, 2545 watts, 86.4% eff, 8819 gms thrust

"DANGER, DANGER, WIL ROBINSON!"

 

So it looks like my planned setup is a good one. Using about 130 watts per pound (aggressive aerobatic sport flying) at roughly 5.5 lbs gives a power requirement of 715 watts. I exceed that by a fair margin, say, about 42% more if I did my math right. Sweet! I will watt test the setup once I get it together, then see how she flies. I can move to a 16x10 if I want some more thrust and still stay within the power limits of the setup!

 

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