i would go w/ the 9 gram, they are so..... much stronger, just keep then way forward.

as far as motor mount goes , after many trial and errors, i do this , bring the bottom spline/ spar flush w/ the front , so u have a " T" of foam . make a small plywood motor mount that is the width of the motor X mount and tall enough to get most of the T and the center line of the motor on the c/l of the wing . the mount sticks above the top foam surface , so behind that i use a piece of 1/8 balsa glued to the foam up against the back of the plywood mount . the peice goes back far enough to mount the battery velcro to , so it makes a motor mount brace and velcro mount.

this piece also sets your right thrust as well as spreads the motor load over the foam. for additional strength on the grossly overpowered hotrod ones i use triangle balsa back a couple inches under the T , front to back and a piece of the same tri stock behind the top of the motor mount , balsa to ply, side to side.

i have had issues w/ the velcro being so strong that on some foams , pulling the battery off tends to pull off the mentioned 1/8" balsa after awhile. the cure for this ,which i do from the start now , is to drill holes top to bottom from the balsa battery mount through the foam and into the tri stock going back from the mount on the bottom . then i stick tooth picks through the holes , ca them , and snip off .

this makes a light strong balsa foam sandwich all attached to the motor mount.

w/ hot glue this all takes less time to build the whole deal than it took me to write this and has proven to take a beating.


chuck.

Built nutball #2 today. 20" with 20 degree dihedral, rudder is 6" tall. Running the 2730-1500kv motor and 12amp HK esc I was using on the 17" nutball. I moved up from a 8x4.3sf up to a 9x4.7sf and either 500 or 800mah 2s batteries. I also went from the weak 3.7g servos I was using up to 9g servos. The servos are heavier so I moved them farther forward but they have more power and are much smoother. This time I used bamboo skewers for reinforcement of the main wing. I also made my spine 1.5" tall and made a fuse from front to rear which allowed me to make a much better motor mount than my first and got the motor centered with the wing. With the extra weight from the servos, motor mount, larger spine and fuse, and the extra tape for stiffening this nutball flies much better. It can be flown inverted much better. I assume this is the dihedral change I made. I can fly it much slower and it hovers like a dream in a slight breeze. I logged in a 18 minute flight on a 800mah 25c gens ace this afternoon with lots of hovering and floating around in small circles with a few bursts b/c my bro wanted to know how fast it would go. I just need to add some landing gear and hopefully I won't crash it for a while. I will get some pics up in a bit.

Well, here she is. Be nice, I am still new to this building thing. I saw 2 color schemes from other members that I had to use on this build. Thanks for all the help and info to everyone in this thread. I must admit I am now a nutball addict.

Finally got the nutball up and flying tonight. 20 incher, built to specs. Motor is a copy of the blue wonder. It flys pretty good, but I can't get the cg far enough forward(I think). 6.6 oz total weight, 2s 500 mah battery about 2 in from the motor(landing gear in the way). Thrust is down a little over 4 deg roughly and about 2 deg right. Elevator set a little under level and when I give it full throttle it really gets 'loose'. Any tips or tricks to help the higher speed? It's just a little jumpy and I don't know where to go from here as this is my first build. Upside is I didn't crash it! Thanks for the help, this one is kind of fun, it is nice to not need a lot of space. Ben

Originally Posted by SamsDad

Finally got the nutball up and flying tonight. 20 incher, built to specs. Motor is a copy of the blue wonder. It flys pretty good, but I can't get the cg far enough forward(I think). 6.6 oz total weight, 2s 500 mah battery about 2 in from the motor(landing gear in the way). Thrust is down a little over 4 deg roughly and about 2 deg right. Elevator set a little under level and when I give it full throttle it really gets 'loose'. Any tips or tricks to help the higher speed? It's just a little jumpy and I don't know where to go from here as this is my first build. Upside is I didn't crash it! Thanks for the help, this one is kind of fun, it is nice to not need a lot of space. Ben

When you say "loose" I assume you mean it gets really twitchy. If that's the case it could be due to many things. The more dihedral the more twitchy it can be. The more throw and area your control surfaces have will make it more twitchy (you can try taking your expo down to 60% on rudder and elevator). Even with that being said, the more air you move across the wing(adding throttle) the more substantial effect your controls have. It's been said in this thread many times, more air moving across the wing/control surfaces equates to a snappier nutball. Also, post some pics of your nutball. Sometimes pics will allow other members to point out something you haven't told them. Where is your cg right now? It should be approximately 5" from the leading edge of the main wing.

I'm in the process of making the 14" mid mount underball as posted by joseico90 with a flat wing suggested by goldguy. Any thoughts on how to mount the hextronik 5 gram motor with the least amount of added weight ?

Originally Posted by melloyello

When you say "loose" I assume you mean it gets really twitchy. If that's the case it could be due to many things. The more dihedral the more twitchy it can be. The more throw and area your control surfaces have will make it more twitchy (you can try taking your expo down to 60% on rudder and elevator). Even with that being said, the more air you move across the wing(adding throttle) the more substantial effect your controls have. It's been said in this thread many times, more air moving across the wing/control surfaces equates to a snappier nutball. Also, post some pics of your nutball. Sometimes pics will allow other members to point out something you haven't told them. Where is your cg right now? It should be approximately 5" from the leading edge of the main wing.

The controls are smooth. It's almost like it is shaking. Flew again and seemed it is more when it is nose down than climbing. Climbing is smooth at full throttle, descending gets to where the whole plane shakes. Is it possible I need to reinforce the rudder and/or elevator with some carbon rod? The plane is all dollar tree foam with the paper off. It is kind of flimsy, but I thought it seemed OK. Thanks, Ben

sounds like airframe flutter, just try some packing tape . the paper is worth it's weight in some cases. maybe fly close and try to see whats fluttering and add tape.

chuck.

It could be the wing is flexing. I removed the paper on my foam as well but I went back and taped the whole top side w/ packing tape to put some weight back on it. The only reason I removed the paper was b/c wet grass will soak it and it will start to fall apart. I use bamboo skewers to stiffen my wing front and rear. Did you add any carbon fiber or bamboo to yours to give the wing some rigidity?

no , i have only built w/ the paper and no reinforcement. very strong . it may take tape on both sides . the control surfaces are prone to flutter. also make sure the pushrods can't flex.

chuck.

Thanks guys. I'll give the tape and some more CF a try. Right now I have two rods running across the wing, but nothing on the control surfaces. Should be able to stiffen things up a bit. Ben

Before adding more weight, look at your control rods as Chuck said, because from the pics it just looks like they are sitting there with nothing to keep them from flexing..

Floppy foam, high speed pitch problems and over control................

Keep in mind here guys, the NutBall was never designed to be a parkjet.

Originally Posted by vinnieg

I'm in the process of making the 14" mid mount underball as posted by joseico90 with a flat wing suggested by goldguy. Any thoughts on how to mount the hextronik 5 gram motor with the least amount of added weight ?

If it flies as well at the Warp 9 in that configuration, you'll be one happy pilot. I've seen one fly as an electron powered combat machine, but never as a 'sloper trainer' as originally designed. You might want to visit the Warp 9 thread for ideas on the amount of side area.

Looking forward to a full and successful report...................

Got to maiden my 17" nutball at our weekly indoor flying session. Did the pre-flight, placed it on the floor and with a little throttle it took off effortlessly. The 2730-1500kv motor provides power enough to really make the nutball maneuverable. I had high, low rates and expo dialed in but found at the settings I was using it would not hover. After dialing the elevons to 100% the nutball hovers easily. I had three flights with 2S 500mah batteries and using an APC 9x3.8 SF prop then switched to 3S 450mah and an APC 8x3.8 SF prop. Both power systems provided great flying. I'm looking forward to getting it outside but it is a real blast to fly inside. I told the fellas I fly with how little the nutball costs and while the UM Parkzone planes we have been flying are fun they don't compare to the low cost of the nutball.