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Sub 2oz. Aerobatic Micro Pitts - Build Begins here!

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Sub 2oz. Aerobatic Micro Pitts - Build Begins here!

Old 01-21-2005, 12:26 PM
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WarpdSpazm
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Default Sub 2oz. Aerobatic Micro Pitts - Build Begins here!

OK, here's my situation. I have Chris O'Reiley's Micro Pitts. 12"ws 36in^2 area. Built per plans she comes out at 28grams. Loading works out to 4oz/ft^2... Pretty damn light.
It's only RET. I'm going to make it ARET so I can do some more aerobatic moves. With some calcualtions I'm looking at upping it to about 42 grams. gives me a 5.88oz/ft^2 loading.
I have the Cirrus MJ setup. 5amp esc - 2cell 150mah lipo for 7.4v

My questions are; Is 5.88 oz/ft^2 too heavy to be aerobatic? (This is the max.. I'm hoping to keep under 40g for a low 5.XX oz. load)
and what would be a good light motor/gearbox combo that I can use. Hovering would be kick*****, but to be able to loop from level would be fine... This is for indoor afterall.
Old 01-24-2005, 04:32 PM
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Nitrocharged
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Default RE: Sub 2oz. Aerobatic (3D?) Micro Pitts

Ray, when you say 28g AUW - what bits are making up that weight?

I used a joule system in Chris's Micro Moth and it came in at 33g. Model weighed 8 grams and all the junk that followed really piled on the weight. Remember every gram saved counts on these tiny things - so cut all the plugs off and solder it up etc.

I know many people have made the Pitts model up to 35g and had no problems getting it to fly. With a 2 cell set up in the joule system ( which I tried in the Moth ) it rocketed along and had no problem getting it to ROG quickly even with the worst of props attached to it. If you can keep the Pitts under 40g, I think you'll be fine.
A flying buddy has made an aileron version of the Pitts and at 20g it flies extrememly well using actuators and the stock KP-00 3.67:1(?) gearing.

I have the 4.75:1 in my Moth, throwing a Kenways 4" blue prop on a single lipo and it zooms.

If you want to hang off the prop - Uttam1 over at rcgroups is working on a 3 gram brushless that puts out 68g of static thrust on 2 cells. ( can also run on 1 cell at about 38g thrust)
I'll be sticking that in a model I made especially for that motor when it becomes available.

I think the down side is - if you hit the deck - its gonna be ugly as these things are fairly fragile but can take a hit or two at stock weight because they are light. With the extra weight they tend to need to go faster and when they hit - ouch! I speak from my last crash which made a mess of things.
Keep us posted on your progress - I am keen to hear how it goes.

Nitro.
Old 01-24-2005, 04:46 PM
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Default RE: Sub 2oz. Aerobatic (3D?) Micro Pitts

That would be a fantastic little motor! I may make my first one a bit more simple and light weight. Work out the bugs and all. When that Bl comes out I could do a second one a bit better...I guess we'll see how heavey this one comes in. I was going to flat sheet the bottom of the wings to help avoid dropping like a rock when i roll it, but that may hurt a lot of the lift and increase flying speed to the point it's not really flyable indoor.... I'll have to test and see. Micro really adds a whole new level of complexity to RC flight.
Old 01-24-2005, 04:48 PM
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Default RE: Sub 2oz. Aerobatic (3D?) Micro Pitts

Chris' 28grams included the RFFS system with 2 actuators out on the control surfaces. Think he used the KP-00 setup. not sure the fine details... I have them at home. When I get all the components together I will weigh them and see what i'm "really" looking at... 40g may be an over-estimation (one can hope).
Old 01-31-2005, 11:14 PM
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Default RE: Sub 2oz. Aerobatic (3D?) Micro Pitts

I'm still debating what to do and so in the mean time, I decided to at least start painting the parts up. After I finish them all I'll weigh them to get an accurate starting point for the frame.


The pic shows the parts I've done so far along with my "painting tools"

In person, it looks shockingly good (to me) considering its done with 2 pens, some crayola markers and a 6" length of cardboard for a ruler.
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Old 02-03-2005, 09:55 AM
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Default RE: Sub 2oz. Aerobatic (3D?) Micro Pitts

Well I began to assemble the fuse. and that's where I stopped. The two halves were of different thickness. Of course I didn't really notic this until AFTER I painted them all nice and purty. I then made the dumb mistake of thinking that the thicker one was the correct one and the thinner was just thinner than needed... WRONG ANSWER. Thankfully I snapped the thick side when trying to bend it... and the correct side is still intact. I'm waiting on an order of contest balsa from lonestar right now, so i can cut my own pieces. Thankfully all the other pieces in this kit look OK to use.

I also picked up enough wood to build a 16"ws version, which after some calculations show promise to fly better and slower than the 12"
Old 02-03-2005, 04:21 PM
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Nitrocharged
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Default RE: Sub 2oz. Aerobatic Micro Pitts - Build Begins here!

Ray,
I'm suprised you didnt grab your trusty sanding block and thin the fat side down!
I sand mybalsa down all the time as my LHS's dont carry 1/32" only the 1mm metric stuff.
I sift through their stock to find the thinner cuts and then I have to sand it further to get where I am going.

I thoroughly steamed my sides to curve them before attempting to get the shape.
Old 02-03-2005, 04:59 PM
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Default RE: Sub 2oz. Aerobatic Micro Pitts - Build Begins here!

Ya know, I had started to sand and after hacking up both lungs from the super fine dust, I said scr3w it. I may go back tonight and sand again. The balsa order is mainly for my 16" version and a 20" version Extra 300s I just got some 3-views for. all that considered, I may mothball the 12" until I can get a 4ch board and actuators like the JMP system.
Put the Cirrus gear in the 16" and Pico and naro stuff in the Extra - which will be my outdoor small space a/c.


I'd prolly spend less on a major drug addiction.
Old 02-05-2005, 03:55 AM
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Default RE: Sub 2oz. Aerobatic Micro Pitts - Build Begins here!

Check this thread for accurate thrust info on the 3 1/2 gram and other brushless motors: http://www.rcgroups.com/forums/showthread.php?t=331374

A 7.7 gram motor makes almost that at 56 grams thrust and the 3 1/2 gram motor making 40. An 11 gram motor makes over 125 grams.
Old 02-05-2005, 10:18 AM
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Default RE: Sub 2oz. Aerobatic Micro Pitts - Build Begins here!

Cool, a couple of familiar names from the other side of the street. I am also going to try an aerobatic (3D) micro and will make the attempt with the 7 gram BL. Have tried with the kp00 4.75(10cm blue), which to me seemed to have the most thrust, but not enough. It will make a nice little MILD aerobatic number if the plane is in the sub 30 gram range thou.
Keep us updated!
Old 02-05-2005, 10:52 PM
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Default RE: Sub 2oz. Aerobatic Micro Pitts - Build Begins here!

Here's an update.. After much sanding and re-sanding of the thicker fuse half I was able to wrap the formers... Did I mention how thin the friggin formers are! Snapped them all and had to CA them. damn, more weight... Thankfully, I have deemed this one my prototype and ordered fresh 4lb balsa to make two more... A "production" 12"ws and a 16"ws ver.

so now I've come to a stall again... I've decided to look into the JMP micro setup with actuators. it's 4ch and will be less weight than the MJ stuff... does anyone know if it's proportional like the RFFS gear?
The engines suggested by mike seem to be the way i'm going to go... either MiniDisk BL or the 5.9gram by Uttam

For the wings on the 12" I'm thinking, leave the undercambered design and put the ailerons on all four wings. Not sure I'd i'd be able to roll it... though with the MD BL motor, i should have enough to do most anything? Enough babbling, on to the pics.
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Old 02-05-2005, 11:54 PM
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Default RE: Sub 2oz. Aerobatic Micro Pitts - Build Begins here!

You need to be looking at regular brushed motors with either the RFFS or the JMP - both have built in ESCs, and neither will run a brushless motor. Your choices are pagers, the M-20 or the N-20...
Old 02-06-2005, 12:11 AM
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Default RE: Sub 2oz. Aerobatic Micro Pitts - Build Begins here!

I read in a thread somewhere... Can't find it at the moment to quote it exact, but BSDmicroRC.com supposedly has a JMP RX that is modded to handle these BL motors... I'm going to check in with them this week and see if it's true of not... Else, small tools inc has a nice 10mm geared setup 6.6g and 22g of thrust, unless you know of another setup below 7g and giving me more than 22g thrust, I think that'll have to be my alt route... If you DO know better setup, then PLEASE let me know.

THanks
Old 02-06-2005, 01:30 AM
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Default RE: Sub 2oz. Aerobatic Micro Pitts - Build Begins here!

There are light weight brushless controllers coming, and there are not too heavy brushless controllers already here, but they don't fit on an RFFS or JMP; they have their own built in.

You can fit whatever sort of controller you want on a Penta (which is postage stamp receiver weighing 2.2 or 2.4 grams) or the MJ and fly brushless. A cheaper solution is a Kenway N-20 motor w/5x3 prop, on a 2-cell mod'ed RFFS or JMP only!, at 7 volts produces up to 38 grams of thrust at .6 amps - well within the limits of the radios' ESCs.

Larry Parks motors are very nice, light and well-made. You need to be aware that most of Larry's development is in the low-speed range, and the thrust measurements may only be valid at either 0 to 4 mph speeds. The particular motor/gear/prop you are looking at is for a slow-flyer. If you just want to hover, they may be fine, but if you need airspeed, they are stuck in low gear... The 5x3 orange prop, Kenway N-20 and 2 135 or 170 LiPolys gives me enough power and speed to have decent looping airplanes at ~35 to 40 grams.

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