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Old Feb 26, 2015, 12:58 AM
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Joined Aug 2009
255 Posts
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FT Blunt Nose Versa CG

This is my second BNV build. The first died a horribly tail heavy death. Taking my time on this one and want to make sure all my effort is gonna pay off.

This one seems to have assembled better. I had a slight warp in the last one that I'm sure was not beneficial and contributed to its death. I also have noted that. The blunt nose section has a slightly deeper chord than the wings. I simply trimmed it up and reglued it together so the TE was uniform. Will this affect CG? The stock CG marks still come in at 6.3" from the nose.

Things I changed. Slightly moved the motor forward. Nothing new but every MM seems to make a difference.
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I moved the servos forward of the CG marks. The leading edge of the wing has 3 stages of curve before leveling off to the trailing edge. I simply slotted the foam and placed the servos in the foam standing up. This may not be pretty but it saves from having to cut open the wing to replace servos. Let's face it, most of us aren't running metal gears in these cheap foamies.
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I also moved the electronics to the front bay. They will be mounted on opposite sides of the bay with enough room to stick in a 3000 mah brick if I want to.

For ballast I have 2 heavy butter knives in the nose with a handful of quarters on standby if I need to glue them in. Using the 6.3" marks on the FT plans the wing balances with a 2200 in the bay. The only thing missing is the motor wire extensions and the control rods. These are going to add some tail weight, hence the quarters.

Do I still use the 6.3" CG marks? As it sits if I move the CG marks to 6" it tips backwards. In fact almost anywhere in front of 6.3" results in a slow tip backwards.

Do I need a special calculator to find the CG for a blunt nose? Or do I measure out where the tip would be and use that for the center chord? I have quite a few hours in this plane and I want her to live past the maiden.
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Old Feb 26, 2015, 03:35 AM
serial scratchbuilder
Granted's Avatar
Canada, BC, Mission
Joined Sep 2012
1,532 Posts
This calculator allows multiple panels to the wing, for a blunt nose put in half the blunt width and zero sweep, root and tip chord should be the same. Then hit the "+1" button next to "Panel 1" and input the wing dimensions. Include the elevons.
http://wingcgcalc.bruder.com.br/en_US/?
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Old Feb 26, 2015, 05:36 AM
watch your head
Germany, MV, Wismar
Joined Jun 2014
100 Posts
I did build 2 of the BNV a 80% and a 140% ... both fly very well.
So if i come back from work today evening i will give you the %-value of the right BNCG
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Old Feb 26, 2015, 02:11 PM
watch your head
Germany, MV, Wismar
Joined Jun 2014
100 Posts
on mine it is right in the middle of the bluntnose. So value is 50% of the bluntnose.
Ive flown it many times and it flyes super with 3S 1000 up to 2200 mAh.

BTW, the pusher versa likes it a bit harder. You have to keep pushing especialy to start it.
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Old Feb 26, 2015, 02:56 PM
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Joined Aug 2009
255 Posts
How about control throws? I read where someone had a list of them at one point but Now I can't find it. How much throw should I have for the servos? How much for hi/low rates, and about what expo are folks using?
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