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Old Nov 29, 2012, 12:33 PM
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Canada, ON, Oakville
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Great takeoff.... and I thought the landing was more than reasonable. Thanks for sharing..... still waiting on the weather up here!

Question - how much full flap deflection are you guys using ?
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Old Nov 29, 2012, 03:40 PM
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I don't have the P-47, but the P-51.
On all my warbirds (2x P-51, Spitfire, Me-262, Vampire) I use 80 deg flaps for full. And around 25deg for 'half'. But mine are also quite heavy - intentionally. Generally 15% to 25% heavier than stock/typical. Though I would still use the same flap levels if they were lighter anyway. (Heavier to improve the flight realism mass/inertias).

Models - especially foam, and even my own 'heavy' ones - have way too little wing loading, so they can cope without flaps at all really. The real aircraft need a LOT of flap - trying to slow down a 3000Kg+ warbird..... so they go right out to 80deg, near vertical, flaps.
By then the flaps are more an airbrake than a lift creator - but that severe angle in the airflow still produces "lift", even if it is just via "air hitting a flat plane that is at an angle to the airflow". So it does both, add some lift and act as an airbrake.

This means you NEED some power to land (though again, stock overly light can come in under no power still), which is what real aircraft do. You don't want to dead stick it because now you could end up too slow, much easier than with no flaps, or a low flap angle. So I always land at some level of power at least - as it is needed to be able to "fly in" to the landing. Well, to fly-in properly... with appropriate speed maintained.

You can land MUCH better, and consistently, with a constant speed, than a reducing or altering speed that you are not in much control of and have to guesstimate targets etc..
Come in dead-stick and you have to work out the decent rate and speed reduction rate as it unfolds with a large component of the "plane's choice".
Come in under power and it is a constant until the final near-landing stage where YOU get an easy task of deciding where to cut power, and know it will slow down well via the flaps.
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Old Nov 29, 2012, 04:23 PM
ham
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Denmark, Capital Region of Denmark, Dragør
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Quote:
Originally Posted by PeterVRC View Post
I don't have the P-47, but the P-51.
On all my warbirds (2x P-51, Spitfire, Me-262, Vampire) I use 80 deg flaps for full. And around 25deg for 'half'. But mine are also quite heavy - intentionally. Generally 15% to 25% heavier than stock/typical. Though I would still use the same flap levels if they were lighter anyway. (Heavier to improve the flight realism mass/inertias).

Models - especially foam, and even my own 'heavy' ones - have way too little wing loading, so they can cope without flaps at all really. The real aircraft need a LOT of flap - trying to slow down a 3000Kg+ warbird..... so they go right out to 80deg, near vertical, flaps.
By then the flaps are more an airbrake than a lift creator - but that severe angle in the airflow still produces "lift", even if it is just via "air hitting a flat plane that is at an angle to the airflow". So it does both, add some lift and act as an airbrake.

This means you NEED some power to land (though again, stock overly light can come in under no power still), which is what real aircraft do. You don't want to dead stick it because now you could end up too slow, much easier than with no flaps, or a low flap angle. So I always land at some level of power at least - as it is needed to be able to "fly in" to the landing. Well, to fly-in properly... with appropriate speed maintained.

You can land MUCH better, and consistently, with a constant speed, than a reducing or altering speed that you are not in much control of and have to guesstimate targets etc..
Come in dead-stick and you have to work out the decent rate and speed reduction rate as it unfolds with a large component of the "plane's choice".
Come in under power and it is a constant until the final near-landing stage where YOU get an easy task of deciding where to cut power, and know it will slow down well via the flaps.
80deg flaps sounds way to much! I have googled it but did not find anything specific other than one mentioning the P-47 had 4 steps of 10deg each, so 40deg in all. This sounds more reasonable to me, because at 80deg the flaps would not create any additional lift, which should be the primary function of flaps. All flaps also create drag, but that's a side effect. If you go for 80deg you only have the drag and not the lift that you want, to be able to fly slow.

I have flown some full size aircraft (not warbirds) and they normally have 30-40deg flaps.

-edit- Found a photo showing the flaps on a P-47. Don't know if it's fully extended, but looks like apr.40deg.
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Old Nov 29, 2012, 04:43 PM
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I have seen videos/pics.. more than that. But maybe it is really 60 to 70deg. But it is severe angle.
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Old Nov 29, 2012, 05:03 PM
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Thanks guys.... mine is quite shallow at the moment... I'll play around increasing it next time I'm flying.
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Old Nov 29, 2012, 05:05 PM
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Ooop! I better apologise for my poor "Protractor eyes"... I measured mine and I use 60deg. (I guess 80deg may as well be VERTICAL really!)
Looking over my P-47 videos it looks like 45deg area on them. I do all mine based off my original P-51 and I guess 'loosely' watching the various aircraft videos - not specifically for flaps, but also not noting any big difference to make me think to use otherwise.

I would not use less than I have as that works great.... I couldn't imagine 'having to' land faster. Though 'faster' is relative to how you want it to land. I get great control under power - which means you can still set the speed anyway - and the drag level means you have a 'braking input' too, because if you reduce power it will slow down more than a no flap plane could. (or less flap angle).

I have flown slow circuits on full flaps (that 60deg or so) and it does not prevent it being flyable at the slow speed - though as per any 'slow flying' you still have to be careful in the manner you fly, banking etc.
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Old Nov 30, 2012, 08:36 PM
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USA, CO, Parker
Joined Dec 2009
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Good discussion on flap settings going on here! I have two settings of flaps. The first is about 10-15 degrees, the second more like 30-35 degrees. Haven't measured. Maybe I will tonight as I am going to be readying the P-47 for flying at my club tomorrow. Last night I sealed up a loose piece of foam that holds the flap servo and had come loose during flight on Tuesday. Had to compensate with the aileron but did not have any trouble bringing her in for a smooth touchdown.

I really like Peter's explanation on use of flaps and power on approach, as well his points on wing loading. I have an FMS Mustang that is probably 50% over the original stock flying weight due to bigger motor, ESC, battery and fiberglass strengthening. I agree that I prefer the heavier wing loading for more realistic handling. That plane pulls over 1000 watts on a 5 amp 4S battery with two-blade 15x10 prop and performs wonderfully well in the air. The P-47 is never going to be as good a performer with its stock prop. The prop is not as efficient. But it is very cool looking and that is the attraction to me. I like the scale effect of heavier wing loading, the big four-bladed prop and the Mr. RC Sound module. As far as the power I think it is definitely better than stock and fairly scale with a 5 amp 4S battery. When I put the 5 amp 5S battery, the plane really comes to life.

Further on Peter's comments, I like to introduce half flap on my downwind as I am retarding the throttle. I like to get to about 40% throttle so the plane is maintaining altitude but slowing down for landing. On base I drop in full flaps and get lined up on the runway. From there it is an exercise of pulling off the power to achieve a good glide slope to the runway, then flaring as I get close to the runway. Ideally, I like to bleed off speed and get close to stall, then set her down on the runway while dropping the throttle close to zero. In my view the finest scale maneuver is a good, smooth landing with a decent straight rollout.

Wishing you all many happy landings,

Jackson
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Old Nov 30, 2012, 08:59 PM
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Sounds like-minded Jackson.

But I do 'fly' right into the landing. Whilst there is an aim to 'flare', my 'flare' is the fact that even under very low power the plane cannot fly level, so it is descending. As you come down to runway level almost, I then guesstimate (real-time reponses being watched) how much I can increase Up Elevator for it to try to fly LEVEL. Zero altitude rise - but that is where your visual feedback loop and some amount of experience needs to feed into prediction of what control you can use. So of course as it slows more and more, and you are trying to 'make' it still fly, the angle of attack is increasing - but altitude never does, as it can't physically do it.
If you 'error' then of course it could flare upwards, and then be a porpoise path of correction (even if just one pop up), or if it goes too far it could even stall! But that is never the aim.
Coming in with high drag, and low power to offset that, makes it all far easier to do than dead-stick! Getting that 'low power' power level optimal is the hardest part, which gives some variations.

The real-time feedback loop is not that 'speed pressured' that you can't see the process unfolding with enough time to do it all well. Plus you err to the side of 'not enough up elevator' and all that means is that it lands a bit faster, and more 'aircraft level' than X amount tail down. I guess I am really aiming for 'aircraft level', up to maybe 10deg or so tail down at most. Certainly not aiming for anywhere near 3 point.

When I watch it I can just visualise full scale Spitfires from movies... Battle of Britain etc... LOL.
When I fly - and the same for playing GOLF(!!) and any other sports I do (ex Tennis, Squash, car and motorbike racing) I am always 3rd Person visualising everything. This gives you great perception of what you are doing, so that you do the correct motions in anything you do - though I guess I probably have some innate ability to do that, because I can see doing it isn't going to help you much unless what you feel/see in your own actions ARE truly mimicking the 3rd person visualisation you are doing! There is something psychological about it.... like great atheletes must need to be able to do that process well, or something, because when your real actions and the visualisations match you move into the 'zone'!! It is very apparent to yourself - in the blending of the two, and in the subsequent results!

And the same when flying, landing etc model planes.... visualisation leads you into being at one with the plane and its motion processes.
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Old Dec 01, 2012, 12:43 AM
Feeling the THRALL
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USA, CO, Parker
Joined Dec 2009
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Hi Peter,

Agree that it is difficult to achieve a three point landing with one of these warbirds. On the other hand it is easy to touch down with lots of speed and have a long rollout. Sometimes those rollouts end badly. So, I do try to use the last seconds of flight to wring out the airspeed and get the plane nice and slow.

As far as visualization goes, it sounds from your description like you are pretty good at this. I find for myself that the best thing to improve landings is to fly a couple of batteries doing approaches, then approaches with touch-n-goes, then full-stop landings. I get into a routine for the approach and landing that allows me to make small fine-tuning adjustments.

Tonight I got the P-47 ready for flight tomorrow. I tested all the systems and balanced for recommended CG with one 5 amp 4S battery. The recommended CG is 105 mm back from wing root. This seems "about right" on the wing. I also marked the CG spot with two thumbtacks so I can use other batteries and do a field check by balancing the plane on the thumbtacks. To get to recommended CG I had to add two ounces of weight to the tail. This means my flights on Tuesday (including the one recorded on video) were with a fairly nose-heavy CG. Nose heavy is fine for flying but doesn't make for graceful landings. In any event I am hoping the plane will be close to perfect in the air now.

FYI I tested the motor with a 5 amp 4S battery and found it pulled 750 watts at 47 amps. On a 5 amp 5S battery it pulled 1120 watts at 62 amps. According to Heads Up RC these motor is designed for max amps of 65 and max watts of 1400. Since the prop will "unload" during flight conditions I believe I have finally found the perfect setup.

I am going to take my video camera and hope that someone at the field is capable of using it to get some footage of my P-47 in action. She has been a long time in the build, modify and refine process. It is nice to think that I am finally (maybe.... hopefully...) at the fly, fly, fly stage.

All the best,

Jackson
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Old Dec 01, 2012, 07:02 AM
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United States, OR, McMinnville
Joined Aug 2011
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full scale pic

This is a t28 at full flaps. Guesstimate 60 degs

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Old Dec 01, 2012, 10:35 PM
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Jackson Stone's Avatar
USA, CO, Parker
Joined Dec 2009
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Today's flying

Hi Guys,

Took the P-47 to the Crosswinds RC club and got in three flights. Last night I balanced the plane to the recommend 105mm behind wing root. Found this CG point to be tail-heavy. The plane did not fly as nicely as my previous flights at Cherry Creek. I am going to remove half the tail weight I added prior to my next flight.

On the third flight I switched from a 5 amp 4S battery to a 5 amp 5S battery. Based on testing last night the HURC Firepower 80 motor pulls 750 watts on 4S and 1120 on 5S. I was only partly into the flight when I noticed the plane was looking and sounding funny so I brought it in. Seems my plywood firewall had detached from the foam bulkhead. I will reattach with epoxy and perhaps add some screws or dowels to secure it more strongly to the bulkhead.

Did not get any video of the P-47 today. Hope to get my balance and firewall issues worked out and get back in the air soon.

Regards,

Jackson
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Old Dec 02, 2012, 04:02 AM
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All of my planes have at least that 60deg. The Vampire has 80deg (for sure).
P-51's and Corsairs, for eg, look to have huge angles and I originally started off with those as references for my model sof them, but P-47 videos I guess I saw them more as they had come in for landing and with tail down gave an impression of more angle. Thus without detailed checking I took them also as huge angle like Corsairs etc. But checking videos closer - pre-landing - it is more between 40deg and 50deg area for the P-47.
Vampire's on the other hand do use 80deg !! More of an air brake than a flap!

But I would still use 60deg area for full flaps, as lower angles hardly achieve anything. Maybe as the plane is lighter is scale relationship to a real plane - and how air molecules, that are not scaled like the model is, act with the change in surface?

...
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Old Dec 03, 2012, 02:22 AM
ham
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I found on more source stating that the P-47 had indicators on the flaps at 20, 30, and 40deg.

It would be interesting to see some airspeed data on the Vampire with different flap angles. Normally the minimum airspeed decreases when flaps are selected. On the aircraft I fly it goes from around 180kt minimum airspeed when clean, to around 120kt with 33deg flaps (full).

I can´t imagine the 80deg flaps on the Vampire does anything else than brake the aircraft
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Old Dec 03, 2012, 05:27 AM
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Well they are split flaps.
Any 'face' angled into an airstream causes air deflection. Any deflection will produce a vector of force - majority rearwards (horizontal) in this Vampire case. Becuse the flap is fixed to the wing, that force must make it pivot 'upwards' (which a lower angle flap will too, just to lesser a degree). Use elevator/pitch to keep the aircraft level and that vector is now "lift".
So ANY face into an airflow will add lift (though it needs to be at a useful position relative to CofG!). But the greater the angle you go 'down', towards perpendicular to airflow, then the greater the drag too of course.
Go to 80deg and you get lift AND huge drag. You still have "Flap action" resultant, but an air-brake in with that too!!

Which even your mentioned 180 goes to 120 is doing.
Of course the minimum airspeed value decreases because of that extra LIFT the flap action gave - whether via a cleaner lower angle, or the huge Vampire angle.

And it is also why you can go to huge angles on ANY aircraft, eg any model, and it will still work fine. More so because they are always overly low wing loadings anyway - so some inefficient drag costing 'mega flaps' isn't a problem. hehe

My 1100mm Vampire can land at not much more than walking pace, still with aileron control to 'steer' a decent amount, without 'falling out of the air' dangers. (Of course still some level of that, but it is WAY slower and still safer than without the huge flaps!).

The same for my P-51...though the aim is not to land that slow, it is to NEED higher power use to still land at "proper speed X", but it means the engine power airflow, plus the ability to 'brake' via lowering engine power, gives you better overall control right down the those lower speeds (or proper speeds) versus what a no flap, or lower flap value, can do.
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Old Dec 03, 2012, 05:36 AM
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Maybe some real aircraft have flap size, and maximum angles, set by the physical construction's strengh ability. Or they only need X amount to do an adequate job anyway.

Because our 'scale models' do not fly in 'scaled down air' they don't do everything 'correctly' as per larger aircraft, so it is quite possible that larger flap angles are needed to actually replicate the actions of the real sized aircraft anyway!
All I know is that I fly HEAVY models, and use HUGE flap angles, and it all pans out to produce what I assess as scale well controlled landing ability! Though I do like to, try to, have things all scale - even the control surface motions etc. Versus some 'poetic licence' to give priority to the scale SEEN FLYING result, above the "Who would know any better" liberties in some physical/visual areas. hehe.
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