|Aug 01, 2012, 02:48 AM|
Pete's Guillow Focke-Wulf FW190 RC Conversion
This is my 4th Guillows this year - I'm totally addicted to building these. This one is Kit #406 (not laser cut )
I really enjoy the build process and this one is the biggest (not just in wing span!) that I've attempted.
I'm planning of building a model that is packed with functionality and still be able to get into the air from ROG. I'll be aiming for a sub 300 gram build. Here is what I would like to include (most parts I have I brought last year):
Motor: Hobbyking D2822/14 Brushless Outrunner 1450kv (38grams)
Prop: Master airscrew 8x6 3 blade
RX: 7 channel Frsky (V8R7)
TX: Turnigy 9x (Er9x - will use programming for slow retracts flaps etc)
Battery: 2s/3s (probably use some 460mAh 3S 42gram batteries I already have)
Servos: Selection of 3.7g-9g servos from HK
2xHXT500 for ailerons,
1xHXT900 for retracts,
1xHXT500 for tail retract,
2xHXT500 for R/E,
2xHK 3.7g for flaps
ESC: HK 20Amp
A/E/T are a must
Flaps: Will be adding flaps, may resort to using a very micro servo to save weight making them a cosmetic feature only
Main gear retracts will be a must.
Will attempt to make a steerable, retractable rear landing gear. This is probably the most ambitious part of the build.
Covering: Mostly balsa planking / tissue
I have a set of Lumifly nav lights for the wing tips which I will also include (minus the white landing light which thw Fw190 didn't have)
Let the build begin!
|Aug 01, 2012, 05:19 AM|
Look forward to your progress – these models certainly are addictive and great fun to convert
|Aug 02, 2012, 03:19 AM|
Building the wings first. The ailerons will be the size as per the plan. To do this I'm building the edge support structure while in-situ then i'll cut out the aileron.
In my previous builds I've use a solid piece of balsa, however I do not think that will work as well for this size aileron. Will be using in-wing servos - HXT500 which weight 7 grams on my scale.
My components weigh it at 236 grams, that could be lightened. I believe the plane itself will come in around 60-70grams so I'll definately be around the 300-320g mark (~11oz). That sounds OK to me 8-14oz seems to be what most are able to achieve a flying model with.
|Aug 02, 2012, 02:25 PM|
I have a couple of concerns about your planned setup.
8 servos will require a separate BEC. No way I would rely on the linear voltage regulator in the ESC to power all those.
I think that is a good choice of motor and prop and should power the model very well.
The concern is the small battery. I think the 1450Kv motor on your proposed prop will suck a 460mAh battery down fast.
I would expect a discharge rate in the 20C range resulting in flight times around 3 minutes (at full throttle). Leave a minute of reserve in case you have to go around once. A 2 minute flight is pretty short IMO. I would suggest at least an 800mAh battery.
Try to get as much throw out of those ailerons as possible. The roll rate will be slow as is. I used the scale size on my Guillows 109 and a roll takes the full length of the field!
Nice work so far, looks like the parts fit isn't too bad for a die crunched kit.
Picked a color scheme yet?
|Aug 02, 2012, 04:46 PM|
I agree with Glenn (I missed understanding that detail in post # 1)
8 servo's will take you to a new level of electronics (and weight) in terms of BEC & Rx.
It will virtually all have to go ahead of the CG point or you will have to keep adding dead weight to the nose.
That's a lot to shoe-horn into the Fw190 and its nose is not very long to assist balance.
It can be done (anything can be done) with careful layout and a lot of trial + error.
Agree also on the battery capacity rating. I never fly less than an 800 ma/hr pack in 400 series. I get a 5 min flight time with a few 'go-arounds' up my sleeve.
|Aug 02, 2012, 08:53 PM|
Thank you for the input, I value your opinions. This model is indeed going to be very challenging and yes a little over the top.
8 servos is alot, I have considered that it might be too much for the ESC. I thought I might be able to get away with it since not all servos will be in use at once. The ESC I have has a 3Amp UBEC which i believe is a switch mode. Given its like a $7 ESC I will find out if its enough with some trial and error.
Still the design is never final, can always eliminate some servos e.g. torque bar aileron system.
Noted comments regarding the battery size. I already have these batteries for my Nitro RC Car as my receiver pack. Looking to also get some 900mAh ones for the car so I will have some options here.
Smoking Beaver - You use a pull-pull mechanism for the tail rudder in your current build - do you think that would work for ailerons? I really like the idea of completely hidden mechanisms.
|Aug 07, 2012, 07:32 AM|
Have been thinking about options for building the aileron mechanism. One option which I have prototyped tonight has the servo and lever completely embedded within the wing and aileron. I saw this on another build somewhere but can't find it and I'm not sure what its proper name is.
What I've done here is take a length of 1.67mm wire and made a 45 degree angle at about 10mm from the end - this goes into the aileron where the aileron has a sandwich gap for the angled 'sweeper' to work when the servo twists the wire. At the servo end the wire has been flatten and melted into the servo spline center. That would be the weakest point.
Here it is in operation. Anyone tried this technique before ?
|Aug 07, 2012, 08:29 AM|
That's a rotary drive system. More info on the RDS here http://www.rcgroups.com/forums/showthread.php?t=449106
I've never used one myself.
How far are you from the volcano?
|Aug 07, 2012, 06:20 PM|
The volcano is about 3 hours drive away so we are safe. Doesn't seem to have caused much damage to populated areas, just some ash. Will be interesting to see if it escalates to a magma volcano rather than letting off some steam. Its in national park with cluster of other volcanoes that show some activity every 10 years or so.
|Aug 07, 2012, 06:42 PM|
That ash looks like nasty stuff. Wouldn't want it sucked into my lungs or my automobile air filter!
The searches I did it looked like it was to your north east but the maps I found kind of sucked and had no scale.
Here we are keeping an eye on the tropical Caribbean for hurricane development.
Anyway, about your model, The 190 has a very short nose, so plan on everything being located ahead of the leading edge if you are to have any chance of achieving the proper CG.
I built the 16" span Guillows 500 series 190. It flies very well on the 8mm motor and an AR6400. I can post a pic if you like.
|Aug 11, 2012, 12:11 AM|
The 190 does have a very short e, but the consolation is that the nose has a large diameter. I will aim to get as much as I can into the nose.
Having some trouble with the retractable landing gear, its a very tight fit, I am going to try to modify the airfoil to give me more room. FW190 used NACA23015 and NACA23009 at the tip. I hope this will not be detrimental to its ability to get into the air.
|Aug 13, 2012, 03:03 AM|
I have started modifying the airfoils. This is going to give me more space for the retractable wheels. I will be going a little over scale - my wheels are already over scale by 1mm width, at the wing root the Fw190 wing depth should be 21.85mm, my wing is around 24mm not including the sheeting.
Wing root chord = 7.5ft
Wing tip chord = 4.5ft
Airfoil Thickness Ratio: Root= 15.3% Tip= 9%
Have also built the fuselage to get a better idea of how this all fits together. The modified airfoil is going to impact the fuse too.
I'm also going to be using the small landing gear retracts from hobby king,
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