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Old Nov 07, 2011, 07:01 PM
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bobcat/condor/falcon type of scratch build, first ever

So I whipped this up in a few days out of my imagination (didn't use any plans, just went off pictures on the internet). This is my first scratch build so I'll be doing a lot of experimenting. what do you think? One has a carbonfiber fuse and the other is just foam which will be reinforced with bbQ sticks.


Can anyone tell me how to find the proper CG for these types of planes? I set it currently at about 1/3 from the leading edge and it seems to be guilding nicely.


Pretty easy to build and it only cost me 4bucks in materials so far and that was a single sheet of 20X30 inch foam board in black. Cut out and built the second plane in about an hour or so.


Planning on using a 2600kv on a 3S lipo with either 1300mah or 2200mah with a 6X4 prop and 3-9G servos. Still waiting on stuff to come from China though.



P.S. anyone know how or have tips to make wheels/landing gear for planes? I dont need retracts, just standard rolling wheels mostly to save the prop from getting hit on landings would be nice.
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Old Nov 07, 2011, 07:18 PM
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did one of these from pics and it turned out nice,same motor/ prop, flew great. Whatchout for weak servos on high speed turns! I found out the hard way. I liked it so much i built one of the falcon 25 jets with a fat scorpion motor pulling 90 amps on a 7x5 Apc prom does about 120. w gear up. HE HE! Just guess on c/g Its an easy bird to fly anyway.
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Old Nov 07, 2011, 07:34 PM
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Quote:
Originally Posted by superinstaller View Post
did one of these from pics and it turned out nice,same motor/ prop, flew great. Whatchout for weak servos on high speed turns! I found out the hard way. I liked it so much i built one of the falcon 25 jets with a fat scorpion motor pulling 90 amps on a 7x5 Apc prom does about 120. w gear up. HE HE! Just guess on c/g Its an easy bird to fly anyway.
for this plane, I didn't put any type of airfoil, its just a sheet of foam board. Is that ok or does it need something like a step or a real airfoil? how did you make your wings?
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Old Nov 10, 2011, 07:25 AM
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havent flown this plane yet, still waiting on stuff from china. Need a servo Y connector for the ailerons.

I did make another plane out of half a sheet of cardboard I got from Costco and it turned out pretty good. Fairly stiff (I can grab it anywhere and shake it hard with no flex in the airframe, Couldn't do that with my other foamies) with the BBQ stick supports and 100% free basically. Also, its ZUW is 11oz which is about 4-6oz less then the foamboard versions I have made. thats about a 50% weight savings! Perhaps I can use a 1300mah 3s lipo instead of the 2200 3s lipo now since I wont need as much weight up front. Should be intresting to see if it will actually fly. It glides pretty darn good.
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Last edited by eccvets; Nov 10, 2011 at 07:30 AM.
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Old Nov 12, 2011, 09:47 AM
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No airfoil needed, I did one w/ one sheet of 6mm depron from rcfoam and it flew amazing. the fuse was 10 layers sanded down. I left the middle 6 layers hollow for the batt and esc, dont forget to cut a SMALL intake and outlet for battery cooling.

Also found some basic plan from parkjets and it think the c/g was marked on it.
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Old Dec 08, 2011, 07:39 PM
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Ok, I finnaly got all the eletronics in and put her together last night. I used the profile plane without the full fuse this time. the eletronics added 6oz to the foam frame and it turned out to be 14 oz before that so 20 oz with out the battery which weights in at about 7-8 oz. AUW is 28oz now which is much heavier then expected. Im using a 50g or 1.7636981 ounce 2600kv outboard motor and 3X9g servos with a y servo splitter as well as a receiver and some how this added 6 oz... it has 194sq/in of wing area and wing loading is about 20-21 oz/sqft... when I go full throttle/WOT it has enought thrust to hover and actually push up into my hand but just barely. I havent thrown it into the air yet but am a bit worried about how it will fly or if it will even fly at all... I have made one airframe which weights in at 7oz with gorrila glue instead of hotglue at the joints and i think the eletronics would weight the same. that would give me an AUW of about 20 oz. still heavier then I think it should be though.

I am using foamboard with the paper still on both sides, should I rip the paper off? how much does that save weight wise and is it worth losing the strenght/stiffness?
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Last edited by eccvets; Dec 08, 2011 at 07:45 PM.
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Old Dec 09, 2011, 02:10 AM
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recharged the batteries just now and retested, it def has more then a 1:1 thrust to weight ratio although I'm still not 100% sure if it will actually fly. sorta scared to lauch it and im not 100% sure how to launch it.
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Old Dec 11, 2011, 05:40 AM
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made some wheels for this sucker, just gotta wait for the wind and rain to stop.
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