Jupiter Junior vintage style biplane - Page 5 - RC Groups
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Feb 20, 2014, 12:41 PM
Thomas B.'s Avatar
I would not add ailerons to the JJ biplane as it flies excellent as RET. I added them to the low winger because it did not go quickly enough back to neutral after a turn.
I `m sure it`s no problem to reduce dihedral when using ailerons.
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Feb 23, 2014, 11:00 PM
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davereap's Avatar
nice model Thomas.. looks like a good easy flier for indoors..

you've distracted me yet again.. so I downloaded the plans and traced it with sketchup ..
At its full size with 270"sq its just a bit bigger than I want for a 10gm motor indoor model so I reduced it to an 18 inch span on the top wing.. this gives a better size for a 10gm setup, and the area is good, I aim for nearer to 200+sq" inches.. slightly smaller with micro gear the weight will be acceptable when done
I will use an 1811-2900. gws6x3, 6A esc , 2gm servos , orange RX , 500 2s lipo.. this is my basic indoor setup and is working well on my indoor models which are all based on around 200-230"sq total horizontal area..
Last edited by davereap; Feb 24, 2014 at 01:11 AM.
Feb 24, 2014, 12:07 PM
Thomas B.'s Avatar
Thanks for the sketchup work, Dave. I received an 1811 motor last week, so I think I will join you with building the smaller version!
Feb 24, 2014, 12:18 PM
Thomas B.'s Avatar

CG Position

I checked the CG position again, and as mojoteri observed, it is at the rear end of the possible range. So I recommend to move it some mm to the front or add a fair amount of downtrim for first flights.
The original prototype has a bit more downthrust than shown on the plan, so it flies well with the rearward CG as long as the motor is running. When the motor is cut, it tends to pull the nose up a bit.
Feb 24, 2014, 01:05 PM
Only nerd in the village
Dave, it is possible to export the Sketchup trace to a dxf file? I have a laser cutter....
Feb 24, 2014, 11:59 PM
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This guy's Avatar
Man I can't wait to build this! It looks like a well suited winter flyer.

Good work
Feb 25, 2014, 12:13 AM
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davereap's Avatar
set the camera view to parallel..
export/2d graphic and under the output filetype choices is dxf and pdf.. that's on the pro version, I am unsure about the free versions export filetypes.. however there are plugins that will do the export as well..
I think there is a phlatforum that's got more info, all to do with lazer cutting from sketchup

so first get all the parts separated and arranged nice and tightly on the screen, I expect you just want outlines, faces removed, then box them tightly in the window as you would for printing.. then export

so I had a play
here are all the parts in sketchup.. pdf and dxf format for the full sized model.. note some parts were supposed to be ply so they will need cutting separately ..also you will need to be careful sorting them out, as they were jumbled up a bit and are not now labelled..
NOTE also they were just a trace over so might not be highly accurate, it may be worth re-starting at the previous sketchup file and adjusting sizes so the end result fits perfectly... however previous models Ive done like this usually fit good enough for me..
NOTE2 from the sketchup files here its easy to scale down for a smaller motor version.. or up to go larger to 24 or 25" top wing span for perhaps a blue wonder motor
Last edited by davereap; Feb 27, 2014 at 02:04 AM.
Feb 25, 2014, 01:28 AM
Registered User



I put the 2822 and 20 amp speed controller in the 125% version. That brought the cg forward about 20mm. I have run 4 packs through it, and it makes a great
lazy flyer. I may want to move it back some once I open the throttle up, and do more than lazy circuits around the field.

I built mine with 7 degrees down thrust based on past experience with undercamered wings. It doesnt balloon up with throttle, but stays fairly level and just goes up nicely. I havent given it full throttle, and am just flying it on 2 cells at the moment. AUW is now about 280-300 grams.

I tried some stalls, and it bobs some, but is very tame. Turns are quite flat.

all in all, enjoyable to fly.
Last edited by mojoteri; Feb 25, 2014 at 01:35 AM. Reason: typos
Feb 25, 2014, 08:29 AM
Thomas B.'s Avatar
Thanks again, for your work Dave!
The only ply parts are the firewall and the 40x35mm rectangle for fixing the uc.
All others are 3mm Depron.
Feb 25, 2014, 12:41 PM
Thomas B.'s Avatar
Mojoteri, how is your elevator trim for level flight with this setup?

Here are some pics of my friend Bernd`s build.
Last edited by Thomas B.; Feb 25, 2014 at 02:15 PM.
Feb 26, 2014, 01:37 AM
Registered User

125% elevator trim

The elevator trim is currently neutral. It flys fine hands off. Throttle changes altitude, not attitude with the downthrust (about 7 degrees), and the plane only pitches up about 10 degrees or so over the throttle range I have tried. It glides just fine throttle off. When the CG was farther back, there was only one reasonble throttle setting. There is a winter storm coming in (We need the rain. This is the driest year in northern california since 1873), but if I can get out, I will try moving the CG back until it changes behavior too much for my taste. I'm using the plane as a relaxed slow flyer, and may want the CG a little farther forward than most pilots. I want to be able to look at the transmitter, and know where the plane will be when I look up again.

Don't let my tastes influence where you like the CG. If/when I cut a second one, I will probably lengthen the nose about 30mm, and stick with the blue wonder. Plenty of power for relaxed flying, but not enough nose weight. The $ Tree foam is about 4.5mm with the paper removed, and I really should have scaled up the plans by 150%, but only went to 125% to make it easy to transport in the car with the wings glued. So many tradeoffs in life. At the moment, I am enjoying the bipe as an addition to my small slow flyer fleet.
Feb 26, 2014, 02:45 AM
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davereap's Avatar
Ive put this on to my build list, I've a couple of other ideas for builds as well, and pointed a flying buddy at the thread, he loves the easy fliers
At the moment I am into building some multi rotors, but when I feel like doing some cutting and sticking as I call it, this will likely get bumped to the top of my list
Feb 26, 2014, 01:16 PM
Thomas B.'s Avatar
Here is a video of my friend`s Martin JJ. Flies great with Cg at original position, but needs about 5mm down trim. So it seems there is the choice either to add downtrim or move CG forward. It depends on what the pilot wants - more stability (CG forward) or more agility (original CG and downtrim). Either way it is a great flyer.
Martins Jupiter Junior (1 min 43 sec)
Feb 26, 2014, 07:31 PM
Only nerd in the village
Dave, looks like you left out the strut part of the fuselage in the trace

I re-traced the fuselage to include the strut and also the slot for the tailplane. I made a small change as I prefer the fuselage top and bottom to go between the sides.

I'll laser cut it this weekend. I plan to use a 1811 2000kV motor and 4gram servos. Should be fine for indoor flying.
Last edited by epilot; Feb 26, 2014 at 08:07 PM.
Feb 27, 2014, 01:43 AM
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davereap's Avatar
quite likely.. oh! yes I see what you mean...duh.. I forgot to select that set of lines when I moved/copied the fuzz sides over...

I will sort that out and replace the drawings.. DONE here is the new repaired version ..previous posted pdf and zip files are now updated..

should be good enough now.. yes some parts will need trimming.. like the top deck between the struts, but most should be fairly good...
I always end up trimming and fitting , reshaping as more often I tend to draw out models for cutting rather than printing plans and using the templates..
However my plans are already printed.. I printed the full drawings with grid at post 62..they are for the smaller 18" version...and I will cut them up to get the various template shapes I need

my flying buddy has another set of plans, he likes the model as well..

the parts only layout viewed below were only for your laser cutter.. you don't need them for anything else, at least now they are corrected. . and luckily you checked before you cut
Last edited by davereap; Feb 27, 2014 at 02:21 AM.

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