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Old Aug 13, 2015, 09:49 AM
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Pilatus B4 Yuki and Sonic Modell

There isn't much information out there about this plane, so I decided to start a thread. At first I was going to put it into the scale sailplane section, but decided it was a better fit here. The scale section tends towards larger and more expensive models, and this is a cheap foamie with a high thrill-to-dollar ratio.

http://www.sonicmodell.com/en/produc...PSid=34&id=108

At a glance it looks a bit like a hotliner but it's not. It's a sailplane and the fun starts when the motor stops. Even though it is made of foam, there are no problems with vertical dives and high-G maneuvers. It has enough power to go vertical, which is a good thing because it will eat up a lot of altitude dancing around the sky.

Like many receiver-ready models, the hardware is not the best quality and there are some things about the construction that made me shake my head. Nothing that a little ingenuity can't fix. It doesn't have flaps and takes quite a bit of room to land. If you try to float in, it will tip stall immediately. I went through many cartwheel landings before finally realizing it will not fly slow. That's ok because I have a Radian for that. Using reflex on the ailerons helps by providing some extra washout.

It works very well for sloping in a stiff wind. It will also thermal on a good day, but it's not made for that.

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Old Aug 13, 2015, 04:54 PM
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Thanks for starting the thread. Hopefully there are more than 2 of us with one. I've found an old review that seem to be the same sailplane but marketed in Europe as the Yuki B4
http://www.rcgroups.com/forums/showthread.php?t=1896805
There seems to be a fair amount of interest in Europe re the Pilatus but between bad Google translations and my lack of German, I'm reduced to watching pretty pictures of soaring with no helpful info.
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Old Aug 14, 2015, 10:18 AM
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There is one more that I know of. One of the guys in our local club picked one up after he saw how much fun I was having.

Good find on the Yuki model. It looks like the same plane except his description of the wing spar doesn't quite match. He wouldn't be the first person to be fooled into thinking that black stuff was carbon fiber, but on mine the ends are not tapered as he described.

I have some videos but they aren't worth uploading yet. They are actually crystal clear, but by the time Youtube does it's magic they look like they were taken with a ten dollar camera. There's something about the business of uploading videos that I'm not getting.

Here is a beautiful video of a full size Pilatus being flown by a world class pilot.

Inverted low pass with Pilatus B4 in Vipiteno (2 min 19 sec)
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Old Aug 18, 2015, 11:22 PM
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My Pilatus showed up today and quickly answered the question….will a 2200 battery fit? not a chance.
A few quick questions for you.
-30 degree deflection on controls as per instructions?
-Are you using their C/G?
-Did you set up as glider or acro? Keeping it simple with acro flaperon set up would give reflex or camber without having to pgm full house glider.
-Aileron differential?
Thanks in advance for any input.
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Old Aug 19, 2015, 10:10 AM
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30 degrees sounds about right judging by how far mine move. Just make sure there's no conflict between the elevator and the rudder. I didn't notice any adverse yaw issues so didn't bother with differential. The last time I checked the CG it was about 3mm behind their suggestion, but every time I change the battery position I retrim the elevator and do a dive test.

You may as well just set it up as Acro with the ailerons on separate channels. There's no point going with full house setups with no flaps and no reason to have the motor on a switch. Camber would be a little scary on this plane because it just loves to tip stall. Try that out with lots of altitude.

I crashed it again while slope soaring a few days ago, and this time it's going to take some work to get it back in the air. The first time was because of too much wind and this time there was not enough. The problem with slope soaring is that the ground is never that far away, and if it goes into a tail spin there isn't room to recover.

My suggestion for the first few flights is to keep it high and fast, and don't try to slow it down too much on the landings.
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Old Sep 05, 2015, 04:45 PM
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Center of gravity?

Hi!

I just bought a Pilatus B4 in KIT form from our local RC supplier, www.hpi-racing.ro. They are resellers of Yuki Modell, so i could order the recommended brushless motor from them.
Problem is, the user manual is that of the ARTF model, and there is no frigging mention where should be the center of gravity at this model.
I couldn't find any information I can only see that there are some round CoG markers (on the user manual - I got them separately on a decal sheet) above the holes where you secure the wings, toward the leading edge. I think that is to far in front..

Can you please tell me where is the CoG? And what battery to buy for this modell? A 3S 2200mAh doesn't fit. I have a 3S 1300mAh but I think it is to weak for this motor.

Please if you can take a picture of the wing and show me where is the CoG related to the holes where the wing joiner screws are. If you can also put a ruler or something so it is easier for me to figure it out.

Thanks!
Alpar
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Old Sep 06, 2015, 09:42 PM
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Quote:
Originally Posted by blacksto View Post
Hi!

I just bought a Pilatus B4 in KIT form from our local RC supplier, www.hpi-racing.ro. They are resellers of Yuki Modell, so i could order the recommended brushless motor from them.
Problem is, the user manual is that of the ARTF model, and there is no frigging mention where should be the center of gravity at this model.
I couldn't find any information I can only see that there are some round CoG markers (on the user manual - I got them separately on a decal sheet) above the holes where you secure the wings, toward the leading edge. I think that is to far in front..

Can you please tell me where is the CoG? And what battery to buy for this modell? A 3S 2200mAh doesn't fit. I have a 3S 1300mAh but I think it is to weak for this motor.

Please if you can take a picture of the wing and show me where is the CoG related to the holes where the wing joiner screws are. If you can also put a ruler or something so it is easier for me to figure it out.

Thanks!
Alpar
Mine was already assembled and the CG markers were 34 mm from the leading edge of the wing. It is another 12 mm back to the screw from there. It flew ok with that CG but seemed a little nose heavy so I moved it back.

A 3s 1800 will fit nicely in between the servos, but you need to devise a way to hold it down so that it doesn't interfere with the servo arms. A 1300 battery has plenty of power for this plane, and that's what I usually use.
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Old Sep 07, 2015, 02:37 AM
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Thanks for the quick info Jovanx!!! I hope I can maiden it soon, I'll get back with the results! Cheers
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Old Sep 08, 2015, 05:31 PM
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Quote:
Originally Posted by Jovanx View Post
Like many receiver-ready models, the hardware is not the best quality and there are some things about the construction that made me shake my head.
------------------------------------
Indeed....I was working on putting a 3s 1300 battery between the servos in the cabin when the seam on the fuselage under the cabin decided that it didn't have enough glue on it and split open. An easy fix but it did make me take the motor out to check the firewall.
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Old Sep 13, 2015, 11:33 PM
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I have one!
Flew it today after many months of non use.
Crashed first three attempts! Finally got it in the air climbing with a steady 80% or so throttle. That huge motor seems to torque roll it hard to the left if throttled up from a toss at low speed. I now give it a hard toss!
Using a 1300 battery shoved as far forward as possible with the esc as far back as possible.
Reinforced the battery area with carbon tubes after my first flight.
Balance? Probably near but aft of the marks.
Added wing tip fences made from gift cards. Glued right on the wing tips. It's been a long time since I last flew this bird but I think the wing tips helped a lot in reducing tip stalls.
Thermalled it today!
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Old Sep 14, 2015, 07:58 PM
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That's an interesting idea with the wing fences. Might have to give that a try. A few millimeters of reflex also helps to keep it from tip stalling. I have it on a switch and have spent quite a bit of time deliberately stalling it to see what happens with and without the reflex.

I finally got the plane rebuilt after the big ski hill crash and flew it today. The trick to launching is definitely to go light on the throttle and heavy on the throw. I had to do some reconstructing of the front, added some CF stiffeners, and replaced the canopy with one made from a soda bottle. At this point I'm just using rubber bands to hold it in place, but it's nice to make some use of the extra space it provides.

The screws that hold the wings together no longer work, so I ended up taping the wings together for today's flight. In spite of all the glue and tape and rubber bands, it actually looks fine and flew better than it ever has.
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Old Sep 14, 2015, 09:50 PM
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One of my wing screws gave out also and I too tape the wings to the fuse. Great idea of using the plastic bottle canopy, I've never been to happy about that tiny space.

I'm stealing your reflex idea. Cool idea adding it to a switch for instant feedback!
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Old Sep 20, 2015, 03:06 PM
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Jovanx, nice work on the repairs. Would magnets work for the wings and canopy? Lee Valley has a great selection of small powerful magnets.
http://www.leevalley.com/en/wood/pag...363,42348&ap=1

My receiver/stabilizer showed up this week and I'm ready to maiden. Winds are 30-45 k today so I think I'll give it a pass.

I've set it up with 2-8mm of reflex on a switch and switch and slider for stabilizer on/off and gain.

I'm not convinced of the need for a stabilizer....more a sense of curiosity
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Old Sep 20, 2015, 05:34 PM
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Quote:
Originally Posted by mw757 View Post
.
I'm not convinced of the need for a stabilizer....more a sense of curiosity
My advice would be to try out the stabilizer on a plane that's easy to fly, and one that you are familiar with. If you're already comfortable flying it in calm conditions, then it makes sense to try out the gyros in a big wind. The Pilatus is not a forgiving plane to fly, and for the first few flights you probably don't need an extra layer of complication.

Stabilizers can do amazing things in the wind, but one of the downsides is that they mask the symptoms of an impending stall. By the time you see the problem it's too late. This plane is prone to tip stalling without giving much notice, and a stabilizer might make it even worse.

I still haven't decided exactly how I'm going to attach the homemade canopy, so for now it's just rubber bands. It's securely attached along one side with a tape hinge, and it flips open sideways. Magnets might work. Right now I'm working on a velcro wing holder that is permanently attached to the underside of one wing, goes through the fuse, and sticks to the other wing. That method has served me well on the Radian.
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Old Sep 30, 2015, 03:03 PM
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I haven't bothered to turn the stabilization on yet.
I'm using 2 levels of reflex and aileron differential which seems to moderate the tip stalling.
It definitely needs to land hotter than the Radian Pro.
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