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Old May 13, 2009, 10:19 AM
GOK
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Turkey, Izmir
Joined Aug 2005
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Phoenix Model 40 size P-51 Mustang (VIDEO ADDED)

After the success of my 1/5 Cub conversion, I am now jumping into another project. Although I still fly my park flyers quite often, I just loved the way these larger planes look, fly and handle wind.

Anyways, this time, on the bench, I have a Phoenix Model P-51. The plane was on sale and I picked it up for approx. $180 (Unfortunately, this is what we modelers in Turkey call “relatively cheap” since usually the prices are ridiculous due to taxes and other stuff). Here are the specs on this one:

Wingspan: 1420mm (56”)
Length: 1230mm (48.5”)
Weight: 2600g – 2800g (5.7lb – 6.2lb)
The recommended glow engine is 40 - 46 size.
She comes with retracts (will be my first model with retractable landing gear).

I believe (might be wrong here) Phoenix Models is more or less the same thing as Seagull Models. They are both brands manufactured in Vietnam, and seem to be relatively widely flown in Europe, although very few of their models make it to US. My first impressions are that the model looks well built. All joints and glue spots are well put together, no broken pieces, covering is real nice and no wrinkles as of yet (it says it is original oracover?). I am not sure about the quality of the included retractable gear as I’ve never before seen another set to compare to. Among other details, the pilot looks a bit funny, the tail wheel is non-scale, main wheels are none-scale, ailerons are none-scale, and the model does not have flaps. But in general, the model looks scale enough for my standards. I’ll be happy if she flies as good as she looks.

Below are a few pics.
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Old May 13, 2009, 10:33 AM
GOK
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Turkey, Izmir
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Now onto my setup and where I’ll have some questions

I already have two 4S 4800mah Hyperion packs, so I want to arrange the power setup around these packs. If she indeed ends up weighing approx. 6lb as advertised for the glow version, I am guessing something between 600Watts and 700Watts should be enough to fly her decently. I don’t know though, how much thrust and pitch speed I would need. Any pointers here would be highly appreciated.

I have two motors in mind – both from Hobbycity. I want to keep her light, I would be happy with little more than scale flight but she doesn’t need to be overpowered. One of the motors I am looking at is closer to E-flite 46 (heavier, and around 650kv), the other is closer to an AXI 2826 with 900kv and weighing approx 6oz. I just can’t decide between the two. Below are the links t these motors, I would really appreciate some advise here as well.

Turnigy SK35-48 900kv
http://www.hobbycity.com/hobbycity/s...idProduct=7393

Turnigy SK42-50 650kv
http://www.hobbycity.com/hobbycity/s..._650Kv_/_1150w

ANother issue I have is with servos. Being unexperienced with larger models, I can't decide if I should use standard servos for everything (except retracts) or would metal geared HS 65s or HS81 do the job?
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Old May 14, 2009, 03:14 AM
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Burnaby, B.C. Canada
Joined Oct 2007
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Hello GOK, I don't have this model, but I did have a me109 of the same size and weight as yours. It was the kyosho kit, 56"wing and 2.8 kg. I used a turnegy 42-60 sk motor with a 14x9 3 blade master airscrew or a 14x7 2 blade prop, with a 4s 4000ma zippy lipo. Not over powered, but good scale flight. You could use the smaller motors, but I'm sure you'd have to use 5s, or even 6s to get their rated power. As for servos, I wouldn't be comfortable using hs81's in this size plane. I used hs 225's for ailerons, futaba 3004's for rudder and elevator, and hs75 retract servo. My model flew just fine on this setup. I'm sure those retracts will work fine, the are metal, mine were plastic, and held up just fine.Good luck on your project, I hope this info helps.
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Old May 14, 2009, 01:26 PM
GOK
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Turkey, Izmir
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Hey calven,

Thanks for chiming in. Its good to hear that these size warbirds will fly fine on 4s. I usually read about people using 5 or even 6s lipos t move these birds.

Anyways, will post updates as progress occurs.

Cheers,

GOK
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Old May 15, 2009, 11:12 AM
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When you set this up, love to see how you mount the batteries.
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Old May 16, 2009, 10:03 AM
GOK
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Turkey, Izmir
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Quote:
Originally Posted by Thrawn150
When you set this up, love to see how you mount the batteries.
That's a good point there Thrawn, I've been thinking where to mount the batteries and how to access them myself. It seems a spot could be made for them over the wing pushed forward towards the cowl. I think this is my only option.

To access them. I only see two options, one is to remove the wing every time the other is to open a hatch forward of the canopy. Neither of them sound too attractive but I think I'll end up going with te hatch option.

Here is a pic of how the battery sits in the fuse pushed flush to the firewall (this is a 4S 4800mah pack). The second pic should give an idea of how forward the pack sits. A hole could be cut in the firewall to push the pack further into the cowl should there be need for CG adjustments.
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Old May 19, 2009, 06:14 AM
GOK
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Well, I finally ordered the electronics for the P51 - they should arrive late this week. I am going to try and fly this model with 4s lipos and a relatively small motor. The motor I ordered is the sk3548 900kv, I gave a link to in my previous posts. This is in the range of a power 32 or an axi 2826-12 I believe.

I know people are usually flying these 40-50 size warbirds on 5-6s and axi 4120s or eflite power46 motor but I didn't want to move up to 5 or 6s lipos just yet - particularly since I already have a few 4s packs. I thought if I could keep the model light (under 90 oz or at around 5.5lb) this motor should fly the model decently on 4s- this way, the retracts may lso hold up much better hopefully.

With 4s lipos and 12x6 - 12x8 props the motor should produce around 700-800 watts and 55-65 mph pitch speed at 45-55 amps. 60 mph is not a speed demon but with 125-135 watts per pound and 1.1 weight to thrust ration the P51 should fly quite scale - and a bit extra. This ofcourse is considering that I can end up with an AUW of 5.5lb MAX.

Anyways, the motor weighs 6oz so I realized that I had to place my batteries inside the cowl as far forward as possible. With this in mind, I completely ditched the pack placement idea in my previous post and started cutting and bashing the firewall to make space for the batteries inside the cowl. Now this is where I was really surprised. I am not familiar with these large glow models so I don't know if this is common but I found inside the firewall two huge leads pre installed (4.6 oz total) . By getting rid of them, and a few other bits and pieces, I shaved off 4.75 oz (mostly from the nose unfortunately).

Since my pack will be pushed all the way into the cowl (its a huge cowling with plenty of space) and since the pack weighs 18.5 oz, I think I will be able to compensate for that weight loss from the nose. I am feeling a bit more confident that I might be able to finish this model with an AUW of up to 5.5lbs, if I can get her to balance without any dead weight.

Oh, the access to batteries will be through a hatch at the underside of the cowl. I hate the idea of cutting into a beautiful cowl but I don't think I have choice here. Besides, I don't think it will even be noticed in flight. This method worked a treat in my 1/5 cub - only I couldn't think of making a hatch there I just cut a hole under the cowl

Here are a few pics.
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Old May 19, 2009, 04:24 PM
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with the cub how do you secure the battery?
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Old May 19, 2009, 11:16 PM
GOK
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Turkey, Izmir
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Quote:
Originally Posted by Thrawn150
with the cub how do you secure the battery?
Velcro and velcro straps. 14 flights and no problems so far.
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Old Jun 04, 2009, 03:01 AM
GOK
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OK, after a looong wait for stuff to arrive from Hobbycity, finally they are here. All the electronics arrived te other day and I started progressing with this build again.

Here's what I've done so far.

- Servos placed (not yet screwed)
- All pushrods and connections are made
- Elevator + Rudder servo tray moved forward
- Firewall cut and reconfigured
- Battery hatch cut underside of the cowling
- Motor mounted and adjusted
- Battery tray prepared ready for installation
- Esc + Bec + Motor connections made
- Stickers applied

Still has some work do be done though:

- Battery tray has to be epoxied in place
- Retracts have to be installed and adjusted
- Servos need to be fixed into place
- Belly pan and air scoop have to be mounted
- Holes in the cowling need to be cut for airflow over the motor

The model currently weighs 2580g (5.7 lb). When all is done she should be a tad under 6 lb. As is, she balances perfectly.

I've tried the motor with various props (11x8.5 ; 12x6 ; 12x8 either APC or EMP) I am getting between 580 - 840 watts with 38-58 amps, depending on which setup I use. The motor is rated for 50-55 amps bursts. So I want to stay at around 650-700 watts with 40-45 amps.

A setup of this sort should provide more than 100 watts per pound, around 60mph speed and 0.8:1 thrust to weight. She won't be a power house but should fly fairly well.

Here are some photos of the progress
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Old Jun 04, 2009, 03:34 AM
GOK
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I do have some questions at this stage, and would really appreciate any feedback.

- The spinner backplate is out of balance and is costing me a few extra amps and 10-20 watts less power Is there a simple way to balance it?

- How do I get air flowing around the motor. The spinner and the backplate are like a wall up front of the motor. If I cut a few slashes in the front sides of the cowl (like in the below pic) would this create air current around the motor?

- While installing the stab, I messed up and it is slightly crooked. Actually it is not really crooked but a little off centered so I now have slightly more right stab according to the left side. This is clear in the below pic. Need I be overly worried about this? Had it been a foamie it would have flown even without a stab But I am not experienced with models this size

So these are some of the issues I am tackling at the moment, please feel free to offer advise

Cheers,

GOK
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Old Jun 04, 2009, 12:51 PM
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Norway
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CMPro 40 size converted ( video )

Quote:
Originally Posted by GOK
I do have some questions at this stage, and would really appreciate any feedback.

- The spinner backplate is out of balance and is costing me a few extra amps and 10-20 watts less power Is there a simple way to balance it?

- How do I get air flowing around the motor. The spinner and the backplate are like a wall up front of the motor. If I cut a few slashes in the front sides of the cowl (like in the below pic) would this create air current around the motor?

- While installing the stab, I messed up and it is slightly crooked. Actually it is not really crooked but a little off centered so I now have slightly more right stab according to the left side. This is clear in the below pic. Need I be overly worried about this? Had it been a foamie it would have flown even without a stab But I am not experienced with models this size

So these are some of the issues I am tackling at the moment, please feel free to offer advise

Cheers,

GOK
We like Mustangs in Norway too :-)) It seem to me that we have nearly the same airplane and are doing the same thing. I had to place the battery closer to the CG and therefore got more space around the motor and got ok cooling of both the motor and the esc. Drilled a couple of holes where the original exhaust is coming out to let the air get out. Battery was moved backwords but I still had to add 80g in the rear to get the CG right. Total weight ended up around 2900g with battery installed. That is heavy in my opinion but we are talking about warbirds with heavy wing loading. I`m used to a very overpowered Hyperion Shukoi E25 and this Mustang felt heavy..very heavy, but good looking in the air. The retracts I used was DSR 30/46 servoless retracts but these can`t handle a 3kg airplane. Will use mechanical retracts instead.
The turnigy motor ( 50 55B-1000kv )broke before take off on the second flight. Some magnets came loose. A common problem on larger motors from Turnigy. Ordered now a Hyperion 4025-10. I am going to run it on 4 cells, but most likely I will change to 5 cells in the near future.
I can`t say how much watts I have have on the current set up, but the video shows that it flies ok and scale like with a 13/8 prop. Guessing that your plane will have about the same power or a little less because your motor is a little smaller.

Video is from the maiden flight a couple of weeks ago( May 20 ). Tried to figure out the stall speed as you can see. Was afraid of tip stalling so the approach speed is too fast :-))

Give you a new report when the Hyperion motor is installed and test flown.
Good luck :-))
RC-P51 Mustang. CMpro 40 size electric converted (1 min 20 sec)



Tore
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Old Jun 05, 2009, 09:25 AM
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United States, NV, Reno
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Quote:
Originally Posted by GOK
I do have some questions at this stage, and would really appreciate any feedback.

- The spinner backplate is out of balance and is costing me a few extra amps and 10-20 watts less power Is there a simple way to balance it?
I'd put the spinner and the backplate on a prop balancer, mark where the spinner and the backplate meet then find the heavy side. I'd then cut strips of electrical tape and add to the light side until the spinner balances. You could also try balancing by removing material from the spinner backplate but I don't like this approach as it's hard to put material back on

Quote:
Originally Posted by GOK

- While installing the stab, I messed up and it is slightly crooked. Actually it is not really crooked but a little off centered so I now have slightly more right stab according to the left side. This is clear in the below pic. Need I be overly worried about this? Had it been a foamie it would have flown even without a stab But I am not experienced with models this size
I doubt you'll notice much of an issue. The plane may want to roll a little more to the right when you're pulling through a loop but it'll be fine. There's a guy at the field I fly at who has a P-47 which he did a MUCH worse job on the elevator. In the air you'd never know it was off center.
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Old Jun 06, 2009, 01:48 PM
GOK
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toelarse, ronin,

Thanks for the feedback guys. I tried to balance the spinner backplate as sugeested by ronin, I think it helped a little, although the wobbling is still there (even if not as much).

I worked on the retracts a bit yesterday but unfortunately ended up burning my retract servo. I think I strained it a bit too much and it couldn't handle it.

I've ordered a Hitec HS 75BB retracts servo. I've mostly read good things about this one, so hoping it will fix my retract problems.

More updates to come soon...

GOK
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Old Jun 23, 2009, 02:05 PM
GOK
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Finally got everything sorted out and flew the mustang this past weekend.

She looks really nice in the air and is a decent flyer. Top speed was around 60mph, big loops from level flight are a breeze, inverted with just a tad down elevator, she will want to tip stall on slow tight banks.

AUW is 2680g (5.8lb)
12x8 EMP prop with 4s 4350 hyperion pack delivers approx. 700 watts and pulls 50ish amps.

Here is a link to a video from the first three flights.

GOKCEN MUSTANG EP TEST UÇUŞU (7 min 19 sec)
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