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Old Dec 08, 2012, 12:20 PM
Cape Cod
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Mitch75,

I was actually thinking more like heavy duty marine batteries.....

Tom
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Old Dec 08, 2012, 12:21 PM
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Quote:
Originally Posted by Daemon View Post
122mm from LE is too far back.
Daemon When you advise me to CG? 110mm? I have the model of 1900mm wingspan.
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Old Dec 08, 2012, 12:23 PM
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I'd still run it about 30mm behind servo wiring slots, which on the 1680 is 75+30 = 105mm from LE.
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Old Dec 08, 2012, 12:41 PM
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Quote:
Originally Posted by Daemon View Post
I'd still run it about 30mm behind servo wiring slots, which on the 1680 is 75+30 = 105mm from LE.
Daemon on my SW1900... 30mm behind servo wiring slots corresponds to 86+30= 116 from LE... I considered 120-121mm..because some say it flies better with a center of gravity a little behind than the 1680


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Old Dec 08, 2012, 12:52 PM
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30mm behind servo wire slots is meaningless if your wiring slots are in a different place.
A little behind CG of 1680 would be alittle behind 105mm. 20mm behind that, is a lot.
Do whatever you want.
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Old Dec 08, 2012, 01:11 PM
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Quote:
Originally Posted by Daemon View Post
30mm behind servo wire slots is meaningless if your wiring slots are in a different place.
A little behind CG of 1680 would be alittle behind 105mm. 20mm behind that, is a lot.
Do whatever you want.
Daemon sorry I have full confidence in you ... you have more experience than me .. so you advise me to 105mm? Also on SW1900..always 105mm...
BTW do you know if someone has had to add 200-300g on the tail with three packs of 5ah 4S on front
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Old Dec 08, 2012, 01:30 PM
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I can't speak for the 1900mm. I don't own one and this isn't the 1900mm thread.
If people are saying that it flies good with the CG a little behind that of the SW1680,
then decide for yourself what "a little bit" behind 105mm is. Personally, I don't
think 20mm is "a little bit".

ian
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Old Dec 08, 2012, 02:20 PM
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Quote:
Originally Posted by Lennyluger View Post
I have a V5 with only one carbon rod. Wouldn't you say it is maybe an idea to glue the halves together AND strengthen them with carbon strips that are glued in both halves? What I've read, the V5 wing isn't as strong as the others in the center?

Regards
Few pages back this was covered pretty extensively.
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Old Dec 08, 2012, 02:22 PM
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Quote:
Originally Posted by Daemon View Post
I can't speak for the 1900mm. I don't own one and this isn't the 1900mm thread.
If people are saying that it flies good with the CG a little behind that of the SW1680,
then decide for yourself what "a little bit" behind 105mm is. Personally, I don't
think 20mm is "a little bit".

ian
20 mm is HUGE change in CG.. Set the CG as Ian says, then don't relocate anything and put the plane on the stand at the 20 plus mark - you will be able to feel the weight difference pushing the nose down and it will be a lot.

What is "flies better" with the changed CG?

Cheers
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Old Dec 08, 2012, 02:25 PM
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Quote:
Originally Posted by mich75 View Post
"too much friction with the air" might be the least of your problems
what you carrying in the front, a couple of car starter batteries :d
lmfao!!
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Old Dec 08, 2012, 02:26 PM
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Quote:
Originally Posted by giuseppe10091989 View Post
I would like to carry 4 battery packs of 5ah 4S in total, 3 on front and one on back to balance the model. I considered about 4.75 inches (approx 122mm) as CoG from LE.
Are you going for an atlantic crossing?
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Old Dec 08, 2012, 02:34 PM
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Originally Posted by Daemon View Post
I use stock foam hinges, and reinforce them with a set of tension hinges at each end,
and near the control horn. Has held up to quite a lot of abuse.

ian
Thanks Ian
Tension hinges?
Cheers
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Old Dec 09, 2012, 05:41 AM
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My build so far:
* 3 sections of Flat 5x1mm carbon added to the wings (glued together)
* 2 lengths of 3x3mm hollow down the tail boom
* 2 short length from the tail boom to elevators
* whole inside area covered in Velcro (move and place stuff where ever I want
* larger motor mount added and it is glued and screw dead into the foam
* 3542/6 1000kv with Aeronaut Cam Carbon 9x7

Cheers

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Old Dec 09, 2012, 06:57 AM
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The CG on my Skywalker 1900mm is usually few mm around the aileron servo wires. Very similar to what I use on my 1680mm. For me it's usually best to have it just a few mm behind the ailerons servo wires.
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Old Dec 09, 2012, 12:45 PM
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Quote:
Originally Posted by raRaRa View Post
The CG on my Skywalker 1900mm is usually few mm around the aileron servo wires. Very similar to what I use on my 1680mm. For me it's usually best to have it just a few mm behind the ailerons servo wires.
Again, can't speak to the 1900mm, but if you're flying with the CG anywhere near the servo wires
on the 1680, it is severely nose heavy. Yes it'll fly, but very inefficiently. My background is
sailplanes, so the first thing I noticed when I maidened my 1680 with the CG at the servo
wires is that it glided like a brick. That plus sluggish elevator response, and would balloon up
as soon as the airspeed increased. All symptoms of being nose heavy. There were
already people flying with it as far back as 30mm behind the servo wires, so I kept moving
it back to there (and beyond) and found it got better and better. I actually fly with it behind
30mm mark, so I consider 30 to be pretty safe.

VizBizTas
Tension hinges.
http://redigital.org/wp/hobbies/tens...ges-with-tape/
Can make and add in the field to repair damaged hinges, and they will literally hinge any
shape to any other shape.

ian
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