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Falcon 120 Help!

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Old 09-12-2012, 09:23 PM
  #1
Jonboy2
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Default Falcon 120 Help!

Just finishing up a Falcon 120 and I would like to replace the two aluminum wing tubes with carbon fibre tubes to save a little on weight. Not sure of the sizes. I know I read somewhere in a thread that someone had actually found a carbon fibre tail boom off of a heli that would work for the larger tube. If anyone out there could tell me the sizes of carbon fibre tube I need to get or what heli tail boom would work I would be greatly oblidged. Thanks Jon
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Old 09-12-2012, 11:38 PM
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Default RE: Falcon 120 Help!

I have a falcon120 and read the same thing and ordered the heli tail boom, only to find that it was way to thin in the sidewall to handle the flight loads so have it sitting in a box doing nothing. the wall thickness was about .8mm

Thanks

dave
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Old 09-13-2012, 12:15 AM
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Default RE: Falcon 120 Help!

My recommendation would be to use a bit of wooden dowel and glue it in the aluminum tubes.
If you hit the deck hard you won't know if your spar is shattered and it might be on a large loop that you find out. They float I don't think you need to worry about weight.
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Old 09-13-2012, 01:30 AM
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Default RE: Falcon 120 Help!

Rcfoam has a tube carbon tube that will work.
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Old 09-13-2012, 01:48 AM
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Default RE: Falcon 120 Help!

I too used a piece of wooden dowel, about 2 inches wider than the fuselage, epoxied into the centre of the larger alloy tube.
I also turned up small pieces of plywood to glue inat each end to make sure the wing joiner extended right into the wing rib for support, as it was slightly short.

My Falconseems very light, so weight should not be an issue.
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Old 09-13-2012, 03:38 AM
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Default RE: Falcon 120 Help!

I think Wooden dowel is the way to go simple but adds a lot of strength, but I think he is looking to replace the alum with carbon to save weight.

Jonboy2
It was probably in the main Falcon 120 thread you seen it [link=http://www.rcuniverse.com/forum/m_5913492/tm.htm]Falcon 120 thread[/link]

Alasdair why only in the centre of the tube? would you not think it would create two potential bend points?


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Old 09-13-2012, 04:04 AM
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Default RE: Falcon 120 Help!

I'm all for doing mods... but there is no reason to put a carbon tube in this model. On the "Falcon 120" thread... we had this debate for a while, and NO ONE actually broke, or bent an aluminum tube without some other source of damage. (like a very hard landing) and in those cases... there was other damage that would would have keep it from flying.

As above... the Heli booms were too thin. So... that's not a viable option.


And... as XairFlyer said.... they float, and weight is almost not an issue. My falcon is 22 Lbs on take off... and flys great. Trying to save a few oz isn't worth the $$$.

Just an FYI... in my Falcon, I added a balsa block to the inside... and it supports the root at the fuse. So... a lot of the weight/pressure is supported using the wing bolts.
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Old 09-13-2012, 06:07 AM
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Default RE: Falcon 120 Help!

Yep No reason It doesn't need it , No reason to pay more money for the spars than the kit. I put the dowel in mine, in all of my crashes I bent everything but the spar. saving 5 grams is a total waste.
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Old 09-13-2012, 06:31 AM
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Default RE: Falcon 120 Help!

The reason I added a piece of dowel to the Falcon was that I had recently bent a steel tube wing joinerpulling about7 g in another model (the one in my avatar). Now it takes 9 g easily.

I did not add it all the way along since the highest stress point is at the wing/fuselage junction, beyond which (out along the wing) the tube has the added benefit of the fibreglass sleeve plus the wing structure, which gradually absorbs the load.

I added the plywood discs in the ends because, on my kit, the alloy tube was a little short, it stopped short of a ply wing rib, and I wanted to make sure that the load was transferred into that rib.

Another thing I did was run clear sellotape along the Leading Edge where the top film covering met the bottom film covering, as I have seen a couple of other ARTFs crash when air got under the front edge of the film and peeled it back.

As Xairflyer said, there is a humungus thread on the Falcon already with several hints and tips.
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Old 09-13-2012, 08:30 AM
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Default RE: Falcon 120 Help!

Those are good points. I think the later kits did have a short tube.

(Covering reminded me of this) the wings popping from pressure is a real issue. There were a few that crashed because the wings came apart in fight... but they all seemed like they didn't install the landing gear buckets. (so the wing was open on the bottom) Make sure you cover any open, external wing holes!!
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Old 09-15-2012, 07:35 AM
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Default RE: Falcon 120 Help!

Thanks for the responses fellas. Like most of you have suggested, I will just use the aluminum tubes that came with the kit. Thanks Jon
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Old 09-19-2012, 04:27 AM
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Default RE: Falcon 120 Help!


Quote:
ORIGINAL: Dr Honda
(Covering reminded me of this) the wings popping from pressure is a real issue. There were a few that crashed because the wings came apart in fight... but they all seemed like they didn't install the landing gear buckets. (so the wing was open on the bottom) Make sure you cover any open, external wing holes!!
It is time that ARTF manufacturers learned not to leave edges of film covering exposed to the oncoming airflow near the leading edge.
A friend lost his Boomerang XL when a wing disintegrated, thought to have been caused by the covering coming unstuck at the LE. It was at an airshow, watched by a large crowd.
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Old 09-19-2012, 06:45 AM
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Default RE: Falcon 120 Help!

my nitro Super Falcon arrived last week and its time to start building! I have a Zenoah 26G that i intend to mount on the plane unless someone says its a bad idea...
I would like to know what retracts work best... any ideas please
what servoes allso...
Thanks!
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Old 09-19-2012, 06:57 AM
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Default RE: Falcon 120 Help!

It's a bad idea. A gasoline engine will not rev high enough to fly it very well. Also it probably takes a 16" prop, which would hit the ground when you flair.

Joe
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Old 09-19-2012, 07:19 AM
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Default RE: Falcon 120 Help!

Yep... what he said. You would be better off using a smaller... higher revving engine. Not to mention... a g26 is heavy, and wants to swing a 22" prop. I don't think there is enough clearance for an 18".

If you want to try gas... I'd say to use a g20i, and use a 15x8 prop... and let it spin +8000 rpm's.
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Old 09-19-2012, 10:57 AM
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Default RE: Falcon 120 Help!

the engine was a gift and I looked up the spec for it and it was speced with a 16x8 and I was going to use a 15x8 3bladed prop. i was looking at mounting the engine on the higher side for better clearance. the other engine I have on hand is a OS 160... would that be a better choice?
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Old 09-19-2012, 12:18 PM
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Default RE: Falcon 120 Help!

A 160 is a much better choice. Most of the discussion in the Jets forum refers to turbinizing theFalcon 120. Isuggest that yousearch in some of the other forums. From what I remember reading anyone that put a 120 on one was disappointed, and it needs a 160 to perform reasonably.

You can also find lots of flight videos on Youtube and judge for yourself.

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Old 09-19-2012, 12:24 PM
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Default RE: Falcon 120 Help!

yea I never fly with the recomended sise
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Old 09-19-2012, 05:35 PM
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Default RE: Falcon 120 Help!


Quote:
ORIGINAL: Dc2LightTech

yea I never fly with the recomended sise

Then you should do what the rest of us have done.... put on 18 Lbs of thrust, with +1000 MPH velocity... and strap on a half gallon of fuel for a 5 minute flight. (lol)
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