djmille

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Hi guys
I don't know if there are any former PBX (X-wing) builders still hanging out in the forum, but I wanted to solicit some advice. I just finished building a double Pizza Box X-wing with carbon legs in an attempt to have a complete VTOL flight. The base of legs extends about 40". I just flew it tonight and dumped it into the ground 4 different times. Luckily the pasture was soft and I only broke rigging wires.

I wanted to know if any of you had played around with thrust angles on these things. When it's sitting ready for takeoff, I apply power and it pulls the nose up and to the right. The only successful flight was with a hand launch. I landed it by basically flying it into the ground while attempting a stationiary hover. It's very nerve racking to fly but seemed to do OK in level flight. I am wanted to experiment with CG and possibly thrust angles to get a more stable hover. My particular unit is powered with an OS 46 FX so it had plenty of vertical power. The weight is 3lb 10 oz and the current CG is about 6.25" back from the leading edge.

Any advice is appreciated (I tried to attach a picture of it; not sure it went through)
Thx
Darin

DLSmith2

djmille,

I love it! Looks great! I don't know the answer to your question, but would setting the rudder trim with a little left rudder for take off counteract the right turning tendency? It seems that there would be plenty of rudder effectiveness with the prop wash at take off.

Any more pictures or dimensions???

Blue skies,

DL

Deadeye

It is a thrust issue, that's for sure. The problem is how do you offset it on an aircraft like that? Now you know why helicopters have tails.

djmille

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I think my problem is that I only made it with one rudder on top. Most other PBX builders have put a rudder both top and bottom. The problem I am having with the single rudder is that it induces a lot of roll when applied. During a hover, the application of rudder will server to roll more than yaw. I will give it another rudder and some down thrust.
-dj

Flypaper 2

Hi Darin;
Don't have the cross Pizza box, only the plain cheese. I do have an electric VTO Pogo that I'm working on. Takes off and lands decently. You'll need the two rudders to get proper yaw control with no roll for when it tries to go over sideways on you. Very large flying surfaces help as all you have is propwash to drive them. Move the CG as far back as you can stand. Good place to start , mine is trimmed for level flight, when I flip it inverted the trim is the same. Should fly upright or inverted with no trim change, or no down elevator applied when inverted. Practice hovering it 20 or 30 ft up to give you time to recover before everything hits the fan. Fellow club member was impressed with mine so he built a coroplast one with a 28 Royal in it. Was out yesterday with it getting the bugs out of it. Hope this helps.

Dave McDonald

My Feedback: (19)

Here's a link to my X-Box thread from a couple years ago that will answer many of your questions.
http://www.rcuniverse.com/forum/tm.asp?m=463785

I would HIGHLY recommend intalling a rudder on the bottom wing panel.

I never found a need to change the thrust angle. These planes are just naturally squirrelly.

My buddy used to have a video of the X-Box in flight posted on his web site, but I'm not sure it's still there anymore. I'll see if I can find it again.

Gravityisnotmyfriend

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I saw a thread here on RCU where a guy had a PBX that had thrust deflectors. The deflectors were small - maybe 1"X 2" - and were right behind the engine. He said that this added stability to the hover. I can't seem to locate the thread, though. I'll let you konw if I find it.

Dave McDonald

My Feedback: (19)

Go to the PROFILE forum here on RCU. (the old Fun Fly forum)

Near the bottom of the page on the right you will see a SEARCH box.

Search for: PBX

You will end up with lots of posts by Wingspan99, who is the one that used the thrust vectoring flaps on his PBX-Wing.

Personally, I didn't feel the need for the vectoring flaps on my X-Box since the four elevons in the prop blast can easily overcome the engine torque.

cosmospho

plans plans plans...... where are the plans I want one.... gonna build me one as my next experiment after I finish my canard gripen

stevezero

My Feedback: (11)

www.hoverbatics.com is the website you want to check out. It is wingspan99's website. There might still be alot of disc/ xbox/xwing stuff on there.