How weight affects the plane?

[Red_Line64]

So I have been looking on the forum and haven't found this subject so I'm sorry for posting since I'm sure it has been discussed. However, I am curious how weight will affect an airplane when talking about the wind. For instance. Will a heavier plane be more steady then a lighter plane in the same conditions? I ask because this is how I lost my plane, and now I know that I was in over my head with that plane. But for my next one I am wondering if I should get a slightly heavier plane? What kind of advice do you have for me? Thank you for your help!!

[slipstick]

Heavier planes fly faster. That can help penerate into wind and they may not be quite as badly affected by gusts. But of course that also means the plane stalls at higher speed and needs to be landed faster.

It's not a simple choice and it depends how light you're starting from. Generally very lightweight planes are impossible to control when there's any wind. OTOH very heavyweight planes are difficult to fly in any conditions.

Steve

[Jurgen Heilig]

Heavier planes fly faster. That can help penerate into wind and they may not be quite as badly affected by gusts. But of course that also means the plane stalls at higher speed and needs to be landed faster.
...

If you have two identical models (not gliders) and put ballast in one of them, what happens?

The heavier model will actually be slower in horizontal flight, accelerate slower, climb slower, can't turn as tight, and can't fly as slow as the lighter model. As it has a slower top speed, it won't penetrate a headwind any better either. Due to the higher inertia, it won't show the effects of gusts as much, but that does not mean it is not affected by them.

:) Jürgen

[MCarlton]

In my experience, as Jurgen says, power models don't really benefit from being heavier, gliders sometimes do, because we are then using gravity and mass as a motive force, so ballast helps to penetrate into wind, fly a bit faster and cope with gusts a bit better.

The best advice for a plane which will cope with windier conditions is to get one that is designed to. The reason a lot of trainer models struggle in the wind isn't their weight, its their design, they tend to have more drag, less responsive controls, lower power and greater lift than sport models.

I'd still stick to building whatever it is as light as you can whilst keeping the structure sound, even with a glider, its far far easier to add ballast if you need to than to remove surplus weight after its built.

Matt

[slipstick]

I don't think the OP was intending just to add a bunch of lead to an existing model. I read the question as "Will a larger, heavier plane handle wind better". Perhaps I was wrong.

But hey, I guess it serves him right for asking his question in Modelling Science where he should have known that he was only going to get involved in an argument ;).

Steve

[MCarlton]

Think you're right mr stick, but I think the same logic applies, a bigger heavier model won't necessarily handle wind better unless something about the design of the model allows it to.

I can fly a 2lb slope soarer in a wind that would keep a full size piper cub on the ground, so size and weight don't always mean that much.

[vintage1]

In almost all ways, weight is a bad thing.

- higher stall speed.
- higher takeoff and landing speed.
- worse rate of climb
- greater crash damage :D
- cant tur ona dime.

BUT in one respect, a heavier model has an advantage. Greater inertia. That DOES mean that gust's shudder it, rather than tip it on its side.

In steady wind, I'd go for a light model, and more power to beat upwind, but when dealing with turbulence, heavier is better.

It also has the advantage that landing speeds are higher anyway, so the chances of a -5mph wind shear making the model fall ot of the sky are less.

I have had two 30" models One weighed 8oz and had 25W power, and would skip around like a gnat..the other weighed 190z and had 160W of power, and would punch through anything. The biggest problem was slowing it up enough to land it in calm air..and hand launching it as well. stalled at about 18mph estimated..javelin style chuck needed. Top speed over 65mph estimated.

Horses for courses.

Adding weight to a lightweight model won't help. but starting off with a heavier model with more power, built for it, will. But you lose the nice parkflyer style of flying.

[Gary Warner]

Speaking from the sailplane flier's view, a heavier sailplane is desired for a higher L/D. This effectively increases the best sink rate speed and L/D speed. But because increased airspeed causes increased drag, our sink rate is higher when we add the weight. The practical reason for ballasting up a sailplane with extra weight is so that we can move upwind on a windy day. It does no good to fly in a thermal that's moving downwind so fast that you can't get back onto the field for the landing. The choice to ballast and if so, how much, is a hot topic come contest day. I do enjoy the extra energy the sailplane has when zooming off a winch, but the price in handling and thermaling is a bit too high for me. I'm usually the last on the field to add ballast. Instead, I usually like to reflex the trailing edges a touch on high wind days because once a thermal is found, I take the reflex out and now I have a thermalling advantage. The reflexing is somewhere between no ballast and full ballast.

Sorry this doesn’t address what the OP was asking about, but this might offer a broader view of the effects of adding weight.

[Brandano]

IIRC, Attack planes designed for Hi-LO-HI or LO-LO-HI attack profiles usually have a higher wing loading to make them less susceptible to wind gusts and turbulence at low altitude. Naturally, once they are free of their ordnance the wing loading is massively reduced. However, this also means that they will stall more easily if they enter any extreme maneuver or if they slow down. On the plus side, the higher inertia gives more time to the pilot to exit the stall before the plane enters a spin. Naturally, this is all fine and dandy for full size planes, radio controlled planes are a different realm altogether.

[mnowell129]

Speaking from the sailplane flier's view, a heavier sailplane is desired for a higher L/D.
I agree with what you're trying to say, but adding ballast doesn't change the L/D, it just changes the speed at which you fly at that L/D.
The effect you mention does happen, that is you can fly upwind with the heavier sailplane.

One thing to keep in mind is that the sink rate varies as the square root of the weight, not a linear factor, so doubling the weight of the sailplane only increases the sink rate by 40%.

[Gary Warner]

I agree with what you're trying to say, but adding ballast doesn't change the L/D, it just changes the speed at which you fly at that L/D.
The effect you mention does happen, that is you can fly upwind with the heavier sailplane.

One thing to keep in mind is that the sink rate varies as the square root of the weight, not a linear factor, so doubling the weight of the sailplane only increases the sink rate by 40%.
Yes, it should read higher speed at best L/D.

[BMatthews]

Red Line, in your case I would venture that the loss of your model was a combination of the model's trim setup and your own inexperience with flying in windy conditions.

Trainers are typically set up with a more forward CG and more wing to tail angle to help them right themselves from an error more readily. However this same "stability" can turn against you if you're trying to fly in windy conditions.

You also need to get used to windy flying by letting the model tell you when it's not flying the way it should be flying. Running downwind the model may look way too fast which can lead a novice wind flyer to try to slow it down so it "looks" more normal. Then the controls get mushy and you're near a stall even though the model appears to be moving like a bat outta hell. And when it comes to gusts that same trainer model with the extra dihedral can be susceptable to getting kicked up onto a wingtip if a sudden side gust should hit the model. Then there's the wind shear effect you get on really windy days where the model seems to be descending happily down with almost no forward speed and suddenly the bottom drops out of the model and it pancakes into the ground. This is due to wind shear and on really windy and especially on gusty windy days you want to ensure you've got a little extra airspeed and only flare a little and at just the very last second to try to minimize all this wind shear effect.

See anything there that matches your crash scenario?

And FWIW I'm in agreement with Jurgen and the others that all say that a heavy model has way more bad traits from the extra weight than any minimal good help it can provide. The right design with controls that react strongly and some extra flying lessons and you'll wonder why you posted this. But even your basic trainer can fly in bad winds as long as you go into the flight armed with some realizations about how strong the wind is and what % of the model's flying speed the wind represents.

[Red_Line64]

Yeah that sounds kind of familiar. I actually had it trimmed pretty good! I was surprised! It was flying straight I was getting ready to turn around but before I did it kicked right and down. Then at full power it didn't take long to make to the ground and hit head first. I got powered down and was pulling up but it didn't have time to do much. It weighed about 15 oz. So I was just thinking that buying another plane that was heavier would help prevent that. I mean I didn't even think it was that windy, which is why I chose to fly that day.

[Jurgen Heilig]

...
I got powered down and was pulling up but it didn't have time to do much. ...

If your model was going down because of a stall, pulling up is about the worst thing you can do. You need to correct any spinning motion, increase the airspeed and then gradually pull out of the dive.

:) Jürgen

[MCarlton]

I think what happened here was that you fell into the downwind flying trap of mistaking groundspeed for airspeed. Flying downwind, the model was probably near to, if not actually stalled. At that point, throttling down and pulling up FEELS like the right thing to do, but as Jurgen says, you need to get the airspeed up before you can do anything else.

To a beginner it feels counter intuitive, because you fly downwind and think that the model is flying faster because groundspeed is higher. It isn't, it could actually be flying slower.

What you need to do is keep the airspeed up when heading downwind, so putting the nose down and opening the throttle a bit is handy.

Pulling up elevator when heading downwind with low airspeed is a bit of a recipe for disaster, it is important to note that contrary to what might seem obvious, pulling up elevator does not make the model climb, it slows it down, and the same for throttle, closing the throttle will not slow it down, it will make it sink.

So I was just thinking that buying another plane that was heavier would help prevent that

Only in as much as the stalling speed would probably be higher, once the model HAS stalled (as in your case) extra weight will work against you and make it more difficult to get the model back up above its stall speed. The trick (and this isn't a criticism) is to try not to get into the stall situation in the first place, by making sure that you keep the airspeed up, even if that means the model is travelling a lot faster over the ground than you are used to.

I mean I didn't even think it was that windy, which is why I chose to fly that day.

It isn't the windspeed that is the problem, its the relationship between the windspeed and the model's airspeed. A 40mph wind might be hell for a lightweight trainer, because it is near to the cruising airspeed of the model, but for a full size aircraft, say, for example, a modern fighter, with a cruising speed of probably 600mph, that 40mph wind is a much smaller fraction of the cruising speed and thus affects the aircraft a lot less.

Scale that up the other way, think about that 40mph being maybe 80% of a models flying speed? Imagine an modern fighter jet in a 450mph wind and you begin to understand how much wind can affect our models.

Thinking that through logically, you can't change the windspeed, but you can change the airspeed. If the windspeed is say 80% of the models normal airspeed, if you increase the airspeed by 25%, you reduce the percentage of airspeed that the windspeed represents and thus reduce its impact on the model.

How high was the model at the time? Remember, when we're standing on the ground, we're not feeling the true strength of the wind because at our level, it is slowed down by the ground.

Imagine a stack of paper on a desk, if you give it a shove, the top sheets will move more than the bottom sheets. Same goes for windspeed, once the model is up at a reasonable height, there could be a fair bit more wind up there.

Its all part of the learning curve though, and part of the fun of this hobby, we've all been there and done it, so don't feel like a boob, we know what we know because we've piled models into the ground, but the important thing is we learn from those mistakes.

Sometimes there is a macho tendancy to blame crashes on everything else, including the colour of a passing dog, but what it boils down to in 90% of crashes is pilot error. The other day, I piled a slope soarer into the ground, I could put it down to turbulence near the ground, but in honesty, it was my error in not compensating for the turbulence I knew would be there.

EDIT:

Some people might not agree with me here, and I'm not sure how it applied to power models, but when its windy, it is sometimes worth putting a bit of extra weight in the nose to bring the CG forward, then trim that out with elevator trim. That increases pitch stability a bit and can help the model to "ride out" gusts and turbulence on a more even keel.

Basically, and I apologise for my lengthy post,

If its windy, fly faster :)

[Red_Line64]

Yeah that all makes sense. Thanks for the help guys! It can be hard to find people friendly enough to just help you rather then laugh at your rookie mistakes! :) So thanks again!!!

[HugePanic]

one thing i learned at my water sport activities:

"gust get worse at higher airspeeds" (sounds like murphy, doesn't it???) :p

at 15kts it is unlikely to have a 15kts gust.

at 30kts it is much more possible to have a 15kts gust...

[JetPlaneFlyer]

one thing i learned at my water sport activities:

"gust get worse at higher airspeeds" (sounds like murphy, doesn't it???) :p

at 15kts it is unlikely to have a 15kts gust.

at 30kts it is much more possible to have a 15kts gust...

Can you explain your thinking behind this a little more. Are you saying that wind gusts are somehow influenced by how fast you fly a model :confused:

As far as i can see the strength of a gust of wind has nothing to do with the speed that a model airplane is flying ... What about if there were two models in the air together, one flying at 30kts and one at 15kts. If they were both close to each other at the time the gust occurred surely they would both experience the same gust?... If not why not?

Steve

[Jurgen Heilig]

Can you explain your thinking behind this a little more. Are you saying that wind gusts are somehow influenced by how fast you fly a model :confused:
...

I think he meant "wind speeds", not "airspeeds".

:) Jürgen

[HugePanic]

yes, i meant airspeed relative to ground!

gust = change of airspeed in my world

[JetPlaneFlyer]

yes, i meant airspeed relative to ground!

gust = change of airspeed in my world

Ahh.. i think the confusion is down to use of the word 'Airspeed'

From the Oxford English Dictionary:

Airspeed

• noun the speed of an aircraft relative to the air through which it is moving.

In my world:-
Gust = change of wind speed (not airspeed)

Anyway FWIW... I do agree that gusts tend to be bigger when the average wind speed is high...

[BMatthews]

Red Lion, if your model is in the 15 oz weight range that implies a rather small model. With smaller models "lighter is always righter" and going to a heavier model will just make things worse.

It sounds odd but due to the lower stalling speed of a lighter model the overall speed range from stall to max is actually wider than with a heavy model that has a higher stall speed and thus a more narrow range of flying speeds. So in reality you have more windy weather buffer with a light model than you do with a heavy one.

As mentioned already when the model departs from normal flight that radically it's generally not a gust that caught it but rather a glitch or a stall and fall off.

[vintage1]

I can't agree here. You may well have the ability to fly faster with a lighter model, but that is not the whole story.

It has to be landed. If your model wont come DOWN at more than 15mph airspeed, without being dived into the ground, you have REAL problems in winds gusting in the 5mph-15mph range.

Its going to need to be flown in at groundspeeds from 0-10mph..a big range of spoeeds to compesnate for with the throttle. Its also going to tip aroond a lot in turbulence. Now if you are a good pilot and have ailerons, that is not too hard tp do..yu fly in into the ground and hope you can keep it there..but any gust - especially if its a taildragger - may cause it to take off again.

I fly a lot of RET stuff and with having to yaw the plane to undo any roll, approaches in such conditions are very tricky. I generally won't fly in winds much above 7mph especially near trees and buildings where rolling gusts can flip the model all over the place.

A model that lands at 20mph or so is a lot easier and less affected by the wind variations.

[HELModels]

In almost all ways, weight is a bad thing.

- higher stall speed.
- higher takeoff and landing speed.
- worse rate of climb
- greater crash damage :D
- cant tur ona dime.

BUT in one respect, a heavier model has an advantage. Greater inertia. That DOES mean that gust's shudder it, rather than tip it on its side.

In steady wind, I'd go for a light model, and more power to beat upwind, but when dealing with turbulence, heavier is better.

It also has the advantage that landing speeds are higher anyway, so the chances of a -5mph wind shear making the model fall ot of the sky are less.

I have had two 30" models One weighed 8oz and had 25W power, and would skip around like a gnat..the other weighed 190z and had 160W of power, and would punch through anything. The biggest problem was slowing it up enough to land it in calm air..and hand launching it as well. stalled at about 18mph estimated..javelin style chuck needed. Top speed over 65mph estimated.

Horses for courses.

Adding weight to a lightweight model won't help. but starting off with a heavier model with more power, built for it, will. But you lose the nice parkflyer style of flying.

I found that a cracked tailboom on a V-tail handles really gusty conditions very well. I flew 2 versions, one with a stiff boom, one which was cracked and springy. In high winds and associated gusts, the buggy whip version was less likely to require huge control inputs to counter the gusts. It absorbed the gust. The stiff boom version needed full deflection to get back on track, where the whippy version would flex and snap back before input is really needed. Both models weighed around 12 oz. with a wing loading around 9 oz/sq ft. I find myself flying in 10-15 mph winds alot, too. The buggy whip cracked and springy tailboom version had/has a slight lag in response to big inputs which I assume is the side-effect, but it isnt noticeable in calm conditions because the bigger inputs arent needed then.

I notice the springy version wiggles and waggles in gusts, but it "springs" right back, whereas the stiffer version goes off. It must be the spring constant or something.

[David22]

one thing i learned at my water sport activities:

"gust get worse at higher airspeeds" (sounds like murphy, doesn't it???) :p

at 15kts it is unlikely to have a 15kts gust.

at 30kts it is much more possible to have a 15kts gust...

interesting

[macboffin]

If the real problem is flying in wind, then a flying wing is recommended, their auto-stability in wind is amazing. But keep the speed up!

[David22]

This thread has been so helpfull.
I have experimented with weight and find lighter is better, unless it is very windy.

I would rather have a little weight problem with lots of power. hehehe

[MCarlton]

A model that lands at 20mph or so is a lot easier and less affected by the wind variations

Is this not as much to do with the "volume" of the model as much as the weight, if that makes sense. Weight on its own isn't really a measure of how well a model will perform in windy conditions, or in gusty conditions for that matter, it is more to do with the difference between the windspeed, gust speed and airspeed.

Whatever the weight, like V1 said, if the model has an optimum landing speed that is near to, or even below the wind speed at ground level, then the turbulence and wind shear at low level is going to cause a problem. You could have a "light" model that has a higher landing speed than a "heavy" model, simply because of the design, wing section and so on.

A large floaty vintage job might well have a landing speed of, say, 15 or 20 MPH, but a similarly sized sport model with a more slippery, less lifty wing section, but the same weight and loading, could have a higher landing speed, or at least, could be landed at a higher landing speed more comfortably. In that scenario, the actual weight of the model isn't making the difference to how the model copes with windy/gusty conditions.

I would rather have a little weight problem with lots of power

There's an element of truth there, but usually, lots of power means lots of weight, take our typical .40 size model again. You could build it overweight, say 7lbs instead of 5. Ok, so you up the engine size to a .60.

That weighs more, so you may need tail weight. Now you have more weight at the longitudanal extremeties, which isn't a great move.

So, with the added weight of the .60, plus a bit of tail weight, you have increased the total weight some more. So now, perhaps it weighs 8lbs.

Lets look at the figures again.

5lbs weight with a normal .40, say 1.2BHP = 4.12lbs/bhp

8lbs weight with a normal .60, say 1.7BHP = 4.7lbs/bhp

So, by increasing the power because you have an overweight model, you actually end up with a heavier model with a lower power/weight ratio.

The figures above are a bit arbitrary, but you get the idea.

The trick is to fly a model which is suitable for the wind conditions, or to wait for wind conditions to be suited to the model.

I know gliders are a little different, but here goes a little comparison.

I can quite happily fly a slope soarer weighing perhaps 2.5lbs, with a wing loading of maybe 10oz/ft2, with a span of say 60inches, in a wind of maybe 30mph without any real problems. Why? Because the model is not very draggy and is designed for those conditions. Landing isn't a problem because the structure is designed to allow me to land the model without damage at an airspeed much higher than its stall speed. I can, therefore, dive to the ground, thus penetrating the wind, and punching through the turbulence and spear the nose into the ground.

If you took a different model with the same stats, for an example, a lightweight vintage model, I don't know, say a lightly built Junior 60, with maybe a .25 up front. You might well even have more weight and a higher wing loading, but would you feel comfortable flying that model in a 30MPH wind?

So, in summary, I would stick to the old adage that "light is right" and build your models as light as you can, commensurate with the right structural strength requirements for what you want the model to acheive.

If you want to fly in higher winds, then you need a model which is capable of performing well in those winds without being overweight. If that means that your current flying skills won't permit that as yet, then so be it.

Stick to flying your model in lower wind speeds until you get more experience.

Similarly, as V1 relates, if you have a particular model in mind, then you need to be patient as regards the weather and fly it when conditions are right. Making it heavier or overpowered won't make a difference.

I would rather have a little weight problem with lots of power

Remember, all that power is absolutely no use to you whatsoever when you throttle back and try to land.

[David22]

very interesting
keep it light
or it will fly like a brick
lol

[David22]

Been practicing with weight
my aerobird3 i have learned that with the correct cg
it makes it glide way way way better

[JetPlaneFlyer]

it makes it glide way way way better

Please define 'way way way better' :confused:

'Better' glide in what respect?... Looses height at a slower rate? Stays up in a thermal easier? Can be slowed up more for landing? Can be turned tighter without stalling?... I'd be 100% sure that adding ballast would make all of these aspects of the glide worse, not better.

If by 'better' you mean the glide is faster so the model penetrates into wind more effectivly and is less disturbed by turbulence and gusts then yes, this is what you would expect. However these 'gains' are made at the costs of the items listed above, and also at the cost of poorer climb performance when under power and shorter duration from the battery.

If increasing weight really made models glide in all respects 'way way way better' then gliders would be cast from solid lead rather than built from balsa or foam ;)

Steve

[David22]

I run a power system not stock
but pushed the bat. and esc way back
it floats or glides way better
if I had to compete for air time
having the cg the way it was tonight
it just floats
not faster just floats goes way further with out power
does that make sence?

i did not increase weight just shifted it back

"Looses height at a slower rate? Stays up in a thermal easier"

need less power to fly

i hope to never add weight to a plane
will just put a larger bat. or motor in if I have to

[David22]

waiting for a really windy day to fly in
i mean really windy
then i will shift the weight forward

[JetPlaneFlyer]

Ahhh... I see you were not experimenting with weight... you were experimenting with CG location. Yes a more rearward CG will make the glide (and powered flight) 'better' in most respects; until you get to the point where the model becomes unstable and difficult/impossible to fly.

However this thread is about the effect of increasing the weight of a model, not the effect of shifting the CG... You should have started another thread if you wanted to discuss CG shifting effects.

Steve

[David22]

oh I see
How weight affects the plane?
you are wrong

[JetPlaneFlyer]

oh I see
How weight affects the plane?
you are wrong
Here is the question that started the thread:
So I have been looking on the forum and haven't found this subject so I'm sorry for posting since I'm sure it has been discussed. However, I am curious how weight will affect an airplane when talking about the wind. For instance. Will a heavier plane be more steady then a lighter plane in the same conditions? I ask because this is how I lost my plane, and now I know that I was in over my head with that plane. But for my next one I am wondering if I should get a slightly heavier plane? What kind of advice do you have for me? Thank you for your help!!

Now tell me I'm wrong in saying that this thread was not to discuss the implications of shifting the CG

[David22]

I have been experimenting with different sized bats. and how the weight and placement affects the plane

I have found that a smaller bat. and its placement really makes a difference regarding how my planes fly

get over it

[David22]

made a plane supper light with small bat.
learned that weight helps control the plane
almost like there is a purfect weight for each plane

[Texas Buzzard]

Adding additional weight to a glider or a powered plane will cause the plane to HAVE to fly a little faster in order to maintain altitude or glide angle.

The stall speed will go up if weight is added. Landings will be faster. When the wind blows most experienced sailplane/glider guys will add ballast. My Olympic II (100") likes an addional 6 ounces when the flags are standing straight out. It penetrates into the wind better.

[David22]

I have limited experience here but have found that I have found the purfect weight for one of my planes.
Too light no good and too heavy you know.

But what i do is rather than add weight I just move cg forward for very high winds

I might be wrong but I think there is a purfect weight for every plane.

[MCarlton]

But what i do is rather than add weight I just move cg forward for very high winds

Moving the CG forward won't really help that much in high winds, except by perhaps giving you a bit more pitch stability, it won't help with penetration or gust tolerance.

I might be wrong but I think there is a purfect weight for every plane

In general (excluding gliders) I would say the best weight for any power plane is the lightest you can get, whilst keeping the right amount of strength. Anything over that is surplus and you just need more motive power to drag it around.

[JetPlaneFlyer]

But what i do is rather than add weight I just move cg forward for very high winds


Moving the CG forward is really the wrong thing to do in high winds because it increases the model's pitch stability so it will make it more sensitive to airspeed changes caused by gusts.

For a glider adding weight on the CG can be a good idea in high winds as gliders derive their forward 'thrust' from gravity. A power model on the other hand will have a higher top speed (in level flight and climb) if kept as light as possible.

Steve

[David22]

I will try what you guys say.
So in high or no wind do you shift cg
and/or add remove weight ?
my cg must be all over the place and use different sized bats. for adding removing weight

keep good cg right

[JetPlaneFlyer]

I will try what you guys say.
So in high or no wind do you shift cg
and/or add remove weight ?
my cg must be all over the place and use different sized bats. for adding removing weight

keep good cg right

It's a power model so I'd not add / remove weight or adjust CG for different wind conditions. Just adjust the CG to give best flight characteristics and leave it there.
If you use different size batteries than adjust their position so that the CG always remains constant.

Steve

[MCarlton]

Like JPF says, the CG stays where the model flies best, usually that will be more or less where the kit/plan whatever dictates.

Moving it around will not help you at all in terms of windy weather.

If your model is a handful in high winds, then you need a model which is more capable of handling a wind, if your skill level is high enough for YOU to handle a high wind.

You cannot take something like a slowstick and "make" it perform better in a wind, because it just ain't designed to. Whatever you do, adding weight, changing the CG, will only make it worse

[David22]

i did have fun today thinking what you guys said
there is a close relationship with weight and bat. performance as well
if you know what i mean
a really nice bat. and good wind
then cg, power and weight all come into factor
X3

IMHO all three have an influence
weight not only is dead weight but for electrics means power
and constant weight and constant cg
get all three right on with the wind and lets rock

[MCarlton]

weight not only is dead weight but for electrics means power

To a point, because your ESC and Motor will only allow a certain input voltage, so whilst you could go from (in conventional battery terms) for example, a 8.4V pack to a 9.6V pack, if you kept the capacity the same, would you not lose something in endurance?

So, to keep the same endurance, you need a larger capacity pack (read heavier). That extra weight would negate to some extent, the power gain you would get from having an extra cell.

You could keep the cell count the same and up the capacity, but this would not give you any more power, just more endurance and potentially a slightly higher initial rpm due to lower internal resistance of the larger capacity cells.

But, if you add more weight, then you need to may need a higher throttle setting to get the same climb performance.

Weight is, as I have said (with the exception of gliders) almost universally a BAD thing. One of the things the electric flight community has been striving towards is high capacity, high current capable battery packs with the minimum weight.

Hence the revolution of Lipo / Li-Ion batteries, allowing the same capacity for less weight, we don't WANT the weight of the battery, we just accept that it is a fact until someone develops an even lighter form of motive power.

a really nice bat. and good wind
then cg, power and weight all come into factor

Well, flying in any kind of wind is only really important in terms of groundspeed, if you ignore the ground, the model doesn't care what the wind is, as it is in the moving body of air (other threads go into this ad infinitum)

Ditto, the CG is the CG regardless of whether you are flying in flat calm or in a gale.

Power does come into it, but only in terms of being able to drag the model into the wind, but this comes at great expense in terms of fuel (battery) cost, in order to acheive the same groundspeed (penetration into wind) you need more throttle, which eats your battery.

At the risk of reiterating myself, you cannot, by changing CG, battery, motor or anything else, make a model which is not designed or suitable for flying in a high wind, BE suitable for it.

Remember, when thinking about flying in a high wind, what we are looking for is the potential to penetrate the wind to keep the model within a reasonable distance and get it back to us, and the ability to recover from (and to an extent, be immune from) the effects of low level turbulence, wind shear and gusts which throw the model around. In that scenario, responsive controls, a surplus of power, a high pitch speed and a slippery design are WAY more important than weight.

[David22]

If it is really windy i would put a larger mah pack in and shift it forward, change cg
and the opposite for light winds
regardless of the plane
high winds seem to make me feel tail heavy if i do not do that

the cg changes depending on your measurements from the leading edge there are recommended settings though
and depending on the wind that changes with how you like to fly

when it comes to heavy winds i do not go for flight time but I do want the most powerfull bat. with the right weight positioned just where i like it
nose heavy

[vintage1]

In general adding weight increases the stall speed, and moving the CG forward will tend to make the model dive and increase airspeed with loss of power.

Adding weight will also increase the model's inertia.

All of these can make the model easier to fly in turbulence.

The crucial issue is to prevent the model stalling in turbulence. An experienced pilot will move the stick forward and increase power. And simply not fly anywhere near the stall, even on finals.

Inexperienced pilots may find the added weight/forward CG beneficial.

Although the models inertia also improves, the thing you really want is to increase moment of inerta, to avoid attitude changes in turbulence. Adding weight near the CG doesn't do a great deal for that, sadly.

[MCarlton]

the cg changes depending on your measurements from the leading edge there are recommended settings though

The recommended CG range is there as a guide, within which you will, or should, find a CG which you are comfortable with. As a general guide, moving the CG forwards will result in a bit of extra pitch stability and more sluggish responses to controls, and, as V1 says, will generally result in more of a tendancy to dive when power is cut.

However, the CG isn't infinitely variable, yes, you can put the CG anywhere you like, but the model will be all but unflayble if you take it too far out of the recommended range.

high winds seem to make me feel tail heavy if i do not do that

This is getting into the realm of the dreaded down wind turn argument. What is making your model seem tail heavy isn't the wind, it is more to do with turbulence. This turbulence is worse at low level.

A light weight model, flying in smooth air, is no more difficult to fly than a heavy one, the only difference is, as I said, the ability to penetrate upwind in relation to the ground.

In turbulence, then I agree, a lighter model can be knocked around more, simply because its low inertia doesn't allow it to "punch through" turbulence and gusts.

Thus, again as V1 states, you would almost be better, in terms of resistance to gusts, to add weight to the nose, tail and each wing tip, but keep the CG in the same place.

This increases the moment of inertia and makes it more difficult for the turbulence to upset the model.

Unfortunately, it also makes it equally difficult to deliberately disturb the model, making control problematic.

and depending on the wind that changes with how you like to fly

Not really, if you look at sailplane models where ballast IS used in high winds, then you will find that it is added at a location in the model such that there is no CG change.

Once you are happy with a CG, it should stay there, regardless of the weather conditions. Start of with it at the front of the CG range if you like, and move it back as you gain more confidence and experience, but don't change it for different wind conditions.

when it comes to heavy winds i do not go for flight time but I do want the most powerfull bat.

I'm not really sure what you mean by "powerful", what I was getting at is that adding weight has drawbacks, and I am of the opinion (others may differ) that adding weight to a powered model is not a fix for flying in windy weather.

What you need to understand is that it isn't the wind itself that is making things difficult in high winds, it is the turbulence and gusts that do that.

For example, I have a little slope soaring glider called a Talon, it spans 50 inches, and weighs just under 16oz. You would think, from those figures, that it would never be able to fly in any sort of wind, but it can, and does, comfortably fly well in anything upto a 25mph wind without a problem.

It is, however, affected by turbulence and gets knowcked about in the air a great deal more than, for example, my PMP Sierra, which is not all that much bigger, but flies at an AUW of 42oz. Importantly, the Talon has a built up wing and light weight built up tail surfaces, meaning it has a low moment of inertia, and is thus easily "wobbled", whereas the Sierra has a heavier foam wing (more weight at the tips) and a heavy all balsa tail group and a big lump of lead in the nose. That means more weight at the extremeties, thus a higher moment of inertia, thus it is more difficult to knock off course.

But! It needs more sky to fly in and cannot be abused in the same way as the Talon (especially near the stall), because the high moment of inertia also makes it slower to respond (especially at low airspeed) and slower to recover (eg from a stall)

As V1 says, the trick is to keep the model moving at a speed a good deal higher than its stall speed. Thats where flying in a high wind is actually an ADVANTAGE, because you can land with a low enough GROUNDSPEED not to damage the model, but with a nice high safe AIRSPEED.

So, why is my little Talon not badly affected by wind? Because it has a fairly low drag design, has quick ailerons and elevator and a nice slow stall speed, meaning I can fly it safely well above the stall throughout a flight.

If I then built a scale Piper Cub, again with a 50" span and 16oz AUW, I would expect it to be much more of a handful in a high wind, simply because of the design.

[David22]

cool thanks i understand way better now
very interesting

[MCarlton]

Happy to help, I'm not an aerodynamics expert though, so some of my explanations are a bit clumsy and unscientific, someone else could probably explain all this a lot better than me.

[Brandano]

Personally, I think that adding weight gives you a much more satisfying "thump" sound :)

[David22]

Thanks guys Not only have I learned about weight but how keeping your speed up helps alot

[David22]

I have been experimenting with weight and power systems.

It all depends on what you want to do, how you fly.

cg is within mm's, that is a given, but low weight planes with high power systems
are my type of plane!

A heavy plane sucks!