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Old Oct 18, 2014, 11:14 AM
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jetjock50's Avatar
United States, SC, Florence
Joined Nov 2004
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fuel tank weight

That might be a useful number for reference. If wanted to do that!!
Roger
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Old Oct 27, 2014, 08:15 PM
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Belgium, Walloon Region, Mons
Joined Jan 2012
394 Posts
worked on mine today,
i finally found the " good" spot for the batteries
and after some work on the rear , i actually got the lipo's just right behind the canopy area with the CG at 1/4 inch in front of the main former ,as roger said and showed up

the plane is just balanced at this point with all the lipo's in place
but still wondering if i will be good like this ,as i m still not confident with the stock cg
and those damned tanks....
still wondering if byron wanted his planes to be nose heavy already with tanks empty? or neutral ?or will be tail heavy a bit ,because you "never " land with fuel tank full empty ....you got it?, m still asking how far forward do i need to go to be good on cg
still thinkin the stock cg could be anything but tail heavy..
i was taxiing today with cg at 1/4 and it behave like a tail heavy jet as hell !! the nose was almost always get slightly off the ground (strut not so compressed)while running !
so...... freaky!

what do you think ,again..?
the best way is to know how much fuel is in the tank and calculate

i will post some pictures
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Old Oct 27, 2014, 09:27 PM
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United States, WA, Duvall
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Sorry been really busy i will eeigh yhe tanks tonight
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Old Oct 27, 2014, 09:54 PM
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CA
Joined Oct 2006
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I would not base the balance by how light the plane sits on the nosewheel as this will depend on the gear location. The Byron is going to be much lighter on the nose gear becuase of the non-scale straight struts, and still mounting the retract near the scale location...very close to CG. That said make it a bit more nose heavy if that makes you more comfortable. It obviously wont have much trouble rotating...even if somewhat nose heavy....with that main gear location. That said...dont pull up elevator until you have some good airspeed....because it will rotate very easily!! This is opposite the standard problem with the Hornet on takeoff.
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Old Oct 27, 2014, 10:37 PM
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United States, MN, Hermantown
Joined Dec 2008
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This may or may not be of any help, but I had Dan Savage figure out my CG for my KMP F-18.. Smaller than this by a long shot, at only 65" long, and WS of 46", but here's what he got.

This will be on a JF90/Het 1200Kv on 12s
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Old Oct 28, 2014, 10:52 AM
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United States, SC, Florence
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Cg

Gianni, where I learned to fly , I was told to error on the side of slightly nose heavy.
That said, using the stock cg and making the plane hang slightly nose down with gear up and no fuel, makes it slightly nose heavy. Obviously with say approximately 24 ozs. of fuel aboard in the stock tank location it would be a good bit nose heavy. And yet it would still rotate and l fly nicely!!! That would tell us how much the nose would hang down with fuel. Then you would check how far the cg moved with fuel and could make that the forward cg limit with batteries in. And still fly nicely!! From there you can move the cg back toward the stock rear limit to suit your flying style. I suspect that even at the stock cg setting Byron was a bit conservative, about moving it back.
I was also told that for most planes 25% of the MAC is a good place to start. As you can see in Cooler's pic , not sure how far apart the lines are from 20% to 25 % I would think either of those lines would be fine again the front line would most likely by safer for a test flight.
All this being said, I believe that starting with your cg say 3/4 " in front of the main former would be good for a first flight. Again, being sure the plane is hanging nose down , a good bit.
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Old Oct 28, 2014, 02:10 PM
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United States, WA, Duvall
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tank weight

Ok so i literally just pulled the tank out and filled it up, and i got 767 grams or 27.055 oz or equal to 1lb 11.055 oz. Sorry for the delay my byron f16 i set the cg tanks empty, tanks full cg was forward but flys fine.
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Old Oct 28, 2014, 02:23 PM
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Just my two cents worth flying both full scale and rc scale always cg forward i am sure you all know this already , on the byron f18 if we go forward on the cg when the mains retract they go aft which should offset some of the forward condition in flight, that being said it looks like to me the center of pressure location on the wings we shouldn't have a problem rotating on rollout we have enough elevator authority. Again just my opinion i could be way off
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Old Oct 28, 2014, 03:59 PM
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United States, SC, Florence
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Thanks BB

LOL,
I agree there always counters to everything, though. Yes when the mains retract they swing back, on the other hand that is pretty well offset when the nose gear swings forward. I was guessing from memory about the 24ozs. of fuel. Thanks for giving a solid number.
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Old Oct 28, 2014, 06:58 PM
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Belgium, Walloon Region, Mons
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thanks for all the advises guys!
never get safe enough with a maiden flight !
i'm close to it , so let's pray it' ll be ok with all that numbers

i'll start with a 3/4" from the main former and will give a feed back as soon as the weather get more clear :/
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Old Nov 05, 2014, 08:29 PM
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United States, OH, Columbus
Joined Oct 2007
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balance the plane just nose heavy with the batts behind the canopy area,it will fly great,trust me I know. I still have my dyn e max powered bug,will probably paint it this winter. I balanced it with batt installed per byrons c.g. instructions.
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Old Nov 05, 2014, 09:15 PM
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United States, SC, Florence
Joined Nov 2004
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Hi Paul

Good to hear your input on the cg. Pretty much confirms what I had in mind. I had assumed the stock cg, and instructions would be good with batteries in, but then for safety margin figured moving it slightly forward as if it were full of fuel would insure a safe first flight. Look forward to seeing your bug with paint on it.
I am looking at some options for retracts which would look sort of scale, so I can move forward on this bug. Have been filling and sanding the inlet openings, but the big push this month is my other passion deer hunting.
Roger
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