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-   -   Bob Cat Copy Falcon 120 Jet (https://www.rcuniverse.com/forum/rc-jets-120/5913492-bob-cat-copy-falcon-120-jet.html)

sweetpea01 12-29-2016 06:52 AM

Thanks Ed. I'm still thinking I'll try the direct link but not sure exactly how'll I'll make it work

sweetpea01 12-30-2016 03:51 PM

Got a few things done this week.

1a. Got the nose wheel steering is figured out. It's going to look like the video below. Since the glue was crap holding in the braces I tore the whole front thing out and will attach the servo to the front of it. I used a temp servo for the time being to set it up. I'll post a video once I clean things up a bit.
https://www.youtube.com/watch?v=iE505LhvYrI

1.a I'm also going to Carbon Fiber glass the wheel mounts and create storage areas for my airtanks so they are upfront. Probably some Battery and weight holders (so I can change the CG easier)


2. I found 4 JR8611A's I had left over from other builds. So now I only need 3 servos (1 being nose steering)

3. I ordered my engine mount and ordered a centerline A4 tank that will be used for smoke (after a few flights)

4. I tore out the blind nuts in the booms and the wings and put 1/4x20 in. Then I cut and Hysol'd bolts into the wings. I use nylon wing nuts on them as attachment points in the fuse. Been doing that on 42% gassers for years and they never come loose and are easy to put on and change out on yearly maint.

5. I put a wood dowl in the boom hole on the wing. I want my bolts more flush and it will be easier to glass this way.

sweetpea01 01-10-2017 12:23 PM

Weather here has been horrendous! It's been 60, flooding rain, then zero, then snow, then zero, now wind and rain and going to upper 50's.

I finished creating my direct link to the nose gear but I don't like it. It will create a tiller bar that is longer than I want (otherwise the linkage hits the wood gear mount) which will require a really large cutout for the nose gear and I was going to do a gear door similar to the BVM Bobcat for ease of use. So I'm probably going with the wire pull-pull setup.

I installed my Turnigy lights in the wing just to see how it will look. They are really a night/dusk light system so I might pull that out and do something brighter before I glass things up. I'm still waiting on my small wingtube and some hardware to show up. I got my 5degree engine mount though. I sanded the wing dowl down and that is now flush.

Just hasn't been a good couple of weeks for me in the shop. This weekend though I will be at it.

Dpienaar 07-24-2017 12:40 PM

Kt p80
 
1 Attachment(s)

Originally Posted by Dr Honda (Post 10970720)
For the new guys, just coming into the Falcon group... Todd at DreamWorks sells my motor mounts now. :D


Here are the 0 degree mounts. (what I use)

http://dreamworksrc.com/catalog/falc...ee-p-2405.html

Here are the 5 Degree mounts that most of the guys here use.

http://dreamworksrc.com/catalog/falc...ee-p-2406.html



Attachment 2225476

Hallo what diferance does the 5dg down do vs the 0dg DW only have the 5dg mounts in atock

Dpienaar 07-24-2017 12:41 PM

Kt p80
 
1 Attachment(s)

Originally Posted by Dr Honda (Post 10970720)
For the new guys, just coming into the Falcon group... Todd at DreamWorks sells my motor mounts now. :D


Here are the 0 degree mounts. (what I use)

http://dreamworksrc.com/catalog/falc...ee-p-2405.html

Here are the 5 Degree mounts that most of the guys here use.

http://dreamworksrc.com/catalog/falc...ee-p-2406.html



Attachment 2225477

Hallo what diferance does the 5dg down do vs the 0dg DW only have the 5dg mounts in atock

edwarda10pilot 07-24-2017 02:16 PM


Originally Posted by Dpienaar (Post 12354557)
Hallo what diferance does the 5dg down do vs the 0dg DW only have the 5dg mounts in atock

If you do not put the 5* of down thrust, you will have to re-trim the plane every time you make a change in throttle setting. A number of us have spent a lot of time making changes to the thrust of the engine to find the setting that requires NO TRIM changes with different throttle settings. That thrust setting is 5* of down thrust.

Ed

Dr Honda 07-25-2017 04:06 AM


Originally Posted by edwarda10pilot (Post 12354591)
If you do not put the 5* of down thrust, you will have to re-trim the plane every time you make a change in throttle setting. A number of us have spent a lot of time making changes to the thrust of the engine to find the setting that requires NO TRIM changes with different throttle settings. That thrust setting is 5* of down thrust.

Ed

Not true. I fly mine with zero mounts, and there isn't any real change in trim. But mine is heavy... so that may make a difference.

why_fly_high 07-25-2017 06:32 AM


Originally Posted by Dr Honda (Post 12354731)
Not true. I fly mine with zero mounts, and there isn't any real change in trim. But mine is heavy... so that may make a difference.

If you always fly at one power setting you can trim for that power setting. With mine and a 100 I cruise at 1/4, sometimes buzz around at half, and sometimes I do full throttle high speed passes. I can tell you from my experience that 5 degrees is just about right to avoid trim changes with power changes.

Dieselman1220 07-30-2017 09:41 PM

If you don't have a 5 degree mount I have found that a wheel collar under the the front mounting straps works about perfect.

charlie turbine 11-23-2017 01:13 PM

Hi
Does anyone know if there should be down thrust on the turbine or should it be mounted parallel ie no down thrust.
thanks

SeaHawk-RCU 11-23-2017 03:10 PM


Originally Posted by charlie turbine (Post 12385917)
Hi
Does anyone know if there should be down thrust on the turbine or should it be mounted parallel ie no down thrust.
thanks

Anywhere between 0 and 5 degrees has been used. My current Falcon 1.20 (no 4) has 3 degrees of down thrust (jet pipe end down) and flies well.

regards

Col

joeflyer 11-24-2017 05:58 AM

If you read the threads you'll see that most use 5 degrees of downthrust. The real answer is that it depends on your engine and how fast you want to fly. Without some downthrust the plane wants to go up at higher speeds. The faster you go the more it raises. If you don't want to be re-trimming your plane at higher speeds then put in some downthrust.

I've had two of these and have flown them with several different engines. If you're using a 10# engine then it probably doesn't matter much. For 14 - 17# of thrust 5 degrees works fine. If you've got 18# or more go with 6 degrees.

Larrythelathe 01-31-2018 04:10 PM

He!p
 
I know this old but hope some are around.

I have a new in box falcon 120. I want to go electric pusher for noise reasons. I however am finding the motor prop selection hard.

Can anyone help?

BaldEagel 01-31-2018 05:39 PM

I think the size of motor you will need for the weight of this airframe will preclude it being used as an electric pusher because of the prop size/diameter needed for the motor vs the ground clearance with the standard length undercarriage, on take off this clearance decreases quite considerably.

Mike

hobbyaire 01-31-2018 08:17 PM

I experimented with an 11 x 12 APC glow prop (they don't/didn't make that one as an e-prop) .. it was satisfactory .. it indeed did work .. not all that fast, but gave a cool turbine like sound, rather than a prop sound.
I had about a 2000 watt, 240kv motor on 10S ..
.. however, I didn't stay with that .. went on to turbines

Larrythelathe 01-31-2018 10:08 PM

3000 watt is where I I think it needs. I just cannot figure out what motor go for

BaldEagel 02-02-2018 06:54 AM

If I remember correctly someone makes three bladed pusher props, that may be your best bet.

Mike

Boomerang1 02-02-2018 11:52 AM


Originally Posted by BaldEagel (Post 12402984)
If I remember correctly someone makes three bladed pusher props, that may be your best bet.

Mike

Prop availability is wider than you think, direction can be reversed remember. ;)

Any three blade prop is on the shopping list, just remember to put the 'curvy side' to the front!

Larrythelathe 02-02-2018 12:45 PM

I was more asking what motor. I would do ic if electric is undoable but must be possible if you can do it with iIC

BaldEagel 02-02-2018 01:28 PM

Need for remembrance, this airframe was designed in the first instance for an IC engine, go to page one.

Mike

Larrythelathe 02-02-2018 01:46 PM

Yup agreed I have a noise sensitive site local. Also one I can fly jets turbines. Local one would be god hence the electric option.

What pitch was used for a three blade 1.20" glow engine? I assume /30cc petrol would be the same?

david101 02-03-2018 05:06 AM

Fan conversion
 
I have seen here in FL a Falcon fly w a 5" fan successfully. Good speed etc. I have a new in box Turbax unit w neu motor and speed control for sale. $350 (all nib)
Dave

Larrythelathe 02-04-2018 02:02 PM

Sorry if I went that way it would be a jetfan 120mm

One thing you guys may be able to help with. My wood work has been pulled from the front as it was a bit loose. Its left a run of resin. How did you all remove this? I have built up new former to allow for the steering servo. How did they intend the builder to do this?

Also how did you do the hatch and canopy?

i3dm 01-11-2019 01:35 PM

guys,
whats the recommended CG fir the falcon 120 jet?

john491 01-11-2019 02:25 PM

C G is 12-3/4" to 13" aft leading edge of the wing at the root. Just about the leading edge of the belly hatch,
John


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