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Old Feb 09, 2010, 10:00 AM
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Advice on first foam plane build

hi everyone.

i have a built a few balsa freeflight planes in my time. basic rubber powered models and also own a wattage extra 330l (broken wing off on first throw into air).
i have a focus6 handset and two recievers but am unsure what one to use.

jeti rex 7 mini 7ch ( gold sticker) fm 35mhz rx

hitec RCD3500 rx dual conversion/ultra narrow band.

hitec Focus 6 RCD ( red lettering) with rate pots for ch1-2-4 and ch3 has hi/low atv

i am looking at the yak or 330 extra type foam shape and basic 3ch setup to learn with. then maybe advance to 4ch controling. but i am unsure on what reciever i should be using with my build the jeti reciever i can gut out from its case and would weigh in around 14 grams just under.

could someone also explain what the ATV rates are for.

in all i am looking at a 10-15a jeti esc 5g servos x3 my own handset and reciever (if possible from above) and a cheap 7.2 lipo.

i am totaly new to foam flyers and flying realy and the need to keep weight down so all advice will be used fully.

i am trying to keep the build as cheap as possible hence foam and cheap motors esc etc etc

thank you
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Old Feb 09, 2010, 10:59 AM
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Germany
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If you are looking for a 3ch trainer I would suggest to take a look at the BluBaby. Its a great Model to learn on, can be upgraded to 4ch later and iirc the 32" Version should fly well on 2s at 10-15A.
Of course an Extra or Yak looks better, but for learning a high-wing is a little easier to handle.

*edit*
Most foam extra or yaks I am aware of are are flat-winged and thus will not work very well on 3ch
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Old Feb 09, 2010, 01:08 PM
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The blubaby 33 is a good choice. I'd build it with a KFm3 wing since that is easy enough to convert to ailerons. The rolled "undercambered" wing isn't appropriate for ailerons.

There is a new design just posted for a Cessna 185 that looks pretty good for a 3 channel plane. It uses a rolled wing so you might need to do more surgery to convert to 4 channel. I suspect it would be good with the KFm3 wing.
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Old Feb 09, 2010, 01:47 PM
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Quote:
Originally Posted by philba View Post
The blubaby 33 is a good choice. I'd build it with a KFm3 wing since that is easy enough to convert to ailerons. The rolled "undercambered" wing isn't appropriate for ailerons.

.
is totaly lost here i built balsa and paper covered planes but nothing so technical. basicly i am totaly new to building. have a very basic knowledge on wings they make lift and hence fly lol. you can call me a total newbie

reason i took the yak/extra shape was its flat wing shape and no need to carve to wing to shape. basic flat slot together shape



i am looking at the kind of foam plane above they sell these at my local hobby store but i cannot afford the kit or the package deal hence trying to build my own, they use baby 2.5g servos and little tiny motors with i think it is 6-12a esc's.

i can get the little jeti esc fairly sheap and my servo's cost £10 uk each. i am unsure on my handset and recievers if they will work together or fit the plane.

my balsa extra 330l is a 24 inch wingspan and was a total handful. my first hand lauch and the plane banked hard left straight into the ground. tore motor from its mount (cobalt 400) and ripped the wings from mounting points. it has hung from my wall since that june day in 2005.
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Old Feb 09, 2010, 02:54 PM
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those planes are pretty aerobatic. They are fast and "twitchy" - i.e. very sensitive to control input. As such, they will make for a pretty frustrating trainer. ierwin's suggestion of a high wing, dihedral trainer is spot on. You will find that a slow plane will give you a chance to learn control with out every mistake meaning a repair job. I know this for a fact. It sounds like you've had similar experiences to mine!

Take a look at the blubaby thread. http://www.rcgroups.com/forums/showthread.php?t=681556
yes, it's huge but the first group of postings are really all you need to know. There is a 24" version that might be good for you.

As for foam, there are lots of cheap sources in the USA but I'm not familiar with the UK in that regard. I know there are lots of foam builders on your side of the pond.

On the radio - most receivers will work with most ESCs. In fact, it's unusual to find one that doesn't.
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Old Feb 09, 2010, 04:57 PM
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I would said something like a 20" Nutball on low rates is as good as any to learn to fly on..
On high rates lots of fun... when you can handle it. See the thread for the facts...http://www.rcgroups.com/forums/showthread.php?t=836389

There is even a kit out there...
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Old Feb 09, 2010, 05:16 PM
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I learned on a HobbyZone Super Cub, so I can't help you out with a design.

But I might be able to help you out with overpriced equipment-- check out www.hobbycity.com for better prices on good equipment.


yellow13
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Old Feb 09, 2010, 05:30 PM
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I've got some things to add from my personal experience (others please correct me if you disagree):
When we talk about foamies, in contrast to the balsa models you are used to, we often look at building times of one weekend and airframe material worth less than 5$.
So the question what equipment to get (motor/esc/lipo) will determine your future options.

If you ever crash beyond repair (and some of the trainer planes you will find here can take A LOT before that point) you just invest another weekend and a few bucks for foam and put the electronics into a completely new plane.
=> a foam plan is not a long term decision

The profile planes are great for 3D and airobatics and many can fly really slow, BUT a wing without dithedral doesn't help the pilot at all. A underchambered wing with dithedral makes the plane self correct its position. On my BluBaby I can completely let go from almost any maneuver and it will correct itself to stable flight (provided it flys high enough). => Dithedral helps the pilot
When we're talking about 3Ch controls I think profiles are out of question, simply because they will flat spin with rudder input, but wont ever fly a nice turn unless they forced to lean to one side with ailerons. => 3Ch requires dithedral
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Old Feb 09, 2010, 06:15 PM
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Quote:
Originally Posted by TamiyaCowboy View Post

my balsa extra 330l is a 24 inch wingspan and was a total handful. my first hand lauch and the plane banked hard left straight into the ground. tore motor from its mount (cobalt 400) and ripped the wings from mounting points. it has hung from my wall since that june day in 2005.
That's exactly why you are getting the suggestions for the Blubaby! Build a 33" span BB and you can fly it as easily as the several comments said, it's as forgiving as noted. It has a full fuse, so all the gear gets hidden inside, looks better as far as I'm concerned. Has a removeable rubber band retained wing, so you can build the plane, with UC wing, fly it til you get your thumbs tuned up, and/or get bored, swap to a kfm2 or 3 and fly some more, add ailerons by just cutting them out of the foam (and adding a servo to control them, of course) and do all the 4 channel acrobatics you could want. Then if you want, get really wierd and try a double rotor gyrocopter wing, all on the same fuselage. Once you get through all that, your building skills and flying skills will allow you to pick pretty much any plane you want to take on.
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Old Feb 10, 2010, 05:58 AM
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thank you everyone.

so most trainers are high wing types.

i had a look at those models mentioned and nothing catches my eye. as most trainers are high wing would a biplane be more suitable and stable to learn with.

i also checked my handset online and am able to adjust ATV's this should help with more slower controls if i am correct. i been trawling youtube for video's explaing how curve wings, cut, glue and build the planes and found i am short on alot of tools. i basicly sold up back in 2006 and never looked back.

as for my electrics

E-PRO SP20A-BEC-AIR BRUSHLESS S/CONTROLLER
Jeti REX 7ch receiver/ 6ch handset (35mhz fm)
7.2v 800mah lipo

i do not know how to match motors to a planes need, i have run brushless before but in micro trucks and powerful 8000kv castle creation mambas. i am also unsure how to match props to motors and planes also.
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Old Feb 10, 2010, 09:08 AM
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Tamiya: The high wing planes achieve stability by what is called the pendulum effect, most of the plane's weight hangs from the wing, so it is inherently stable. appropriate dihedral enhances that effect. It can still be "overcome" such that they can be really agressive flyers. (my Flying buds and I pull out our Blubaby 24's when it is too windy to fly other larger planes, as these little guys will zip and zoom no matter what the weather). If you are "typical" and want a jet, or 3d/pattern ship type design, you may want to hold off on them a bit and just do a simple high wing monoplane to get the thumbs educated on how to handle that third dimension. My guidance would be to not do a biplane first, there's issues with wing incidence, alignment, etc that you won't have on a single wing build. The idea is to do a plane that will allow you to focus on learning to fly it, not doing development on it while trying to learn to fly it. That's where lots of guys go wrong, they do a plane that is very responsive and takes lots of tuning to fly well (or at all) but have no idea how to do the tuning, or even diagnose what tuning is required. That's the beauty of Blubabys and Trainer1's as they don't require much tuning at all to fly decently.

To your last question, If you browse the BB thread, you will find Tons of help with matching motors, props, batteries, etc. just have to search for it. This goes for most all the popular planes on the forum, guys have tried most every motor on every plane at one time or another.

You definitely need a volt/ampmeter, or better yet a wattmeter like wattsup, or the several others, to know if you have picked the right combo that will not fry itself in air. If you have too little thrust, you can tell it by test flying and just have to reprop, but if you are over amped, you can lose parts!

match what you have with a BluWonder 24 gram motor and it's a good package for a 33 inch span Blubaby.
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Old Feb 10, 2010, 10:57 AM
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Matching motors/props/escs. This is certainly a confusing area for the neophyte. However, it's not bad at all once you understand the relationships.

Basically, the prop determines how much work the motor has to do. The amount of work it does determines the current it draws. The ESC needs to be able to handle the current. It's easy to see that too big a prop means you can cause the ESC to get overloaded and burn up.

A given motor has 2 ratings of interest: kV and current (sometimes wattage but ignore that for a moment). kV is the number of RPM per volt. If you use a 2 cell LIPO, it gives 7.4 volts (a bit more when fully charged) so a 1000 kV motor will run at 7400 RPM when it's unloaded. The current rating is a max - don't exceed it or the motor will over heat.

Props have 2 numbers - diameter and pitch. Diameter is pretty obvious and pitch is the number of inches (or mm) that it would travel in a single revolution (in a perfect world). You will see numbers like 8040 which means a diameter of 8" and pitch for 4". Pitch has often been likened to the gears in a car. The lower the pitch, the lower the gear - slower but with more power. In fact, low pitch props are often called "slow fly". A trainer should have a lower pitch prop.

Now the relationship of prop and motor to ESC isn't simple. In general, the bigger the prop, the more current pull and the higher current rating your ESC will need. You could get a wattmeter and test to make sure a prop+motor combo is right. Fortunately, people have done the measurements for us. Take a look at this web site: www.headsuprc.com. Look at a given motor and you will see that they have measured a number of props with each motor and tell you how they did. Here is the headsup page for the blue wonder motor You will see that for that 8040 prop with a 3 cell LIPO (11.1V), the BW produces 15 oz of thrust at 6 Amps of current draw. The pitch speed means that in a perfect world, the plane would go 35 mph. This is a good combo for the BW on a plane that weighs around 15 oz. Your ESC can handle this no problem.

Some motors are spec'd for wattage, not current. To get the current, take the highest voltage they rate it for (2 cell - 7.4, 3 cell 11.1, 4 cell 14.8) and divide the wattage by that to get the max current. For example a 120 watt motor that runs on 2 or 3 cell LIPOs will have a max current of 120/11.1 (10.8) amps.

By the way, headsup is a very good vendor though I don't know if he ships internationally.
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Old Feb 10, 2010, 11:21 AM
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thank you springer.

i have taken heed of advice and downloaded yak55 30 also bb24 and bb12.

i decided i shall build all three use the two BB and have the yak for when i think i can fly it.

i am unable to purchase all my things at once. i have matched my jeti 7ch receiver to my handset. i have my eyes on a 20amp esc , and just picked a 7.2 800mah lipo from the lhs website but have not purchased as i also need a charger.

the blue motor i am unable to get the lhs said they do not stock and cant get them but they have other different types.

Foam is my biggest headache lol, three places i tried today and none have ever head of Epp or Xps or depron tried to palm me of with open cell packing foam. have another lad also asking where i get my foam to on another site. hopefuly i have a last chance on my local flee market been told of a foam seller there fingers crossed.
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Old Feb 10, 2010, 11:40 AM
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Quote:
Originally Posted by philba View Post
Matching motors/props/escs. This is certainly a confusing area for the neophyte. However, it's not bad at all once you understand the relationships.

Basically, the prop determines how much work the motor has to do. The amount of work it does determines the current it draws. The ESC needs to be able to handle the current. It's easy to see that too big a prop means you can cause the ESC to get overloaded and burn up.

A given motor has 2 ratings of interest: kV and current (sometimes wattage but ignore that for a moment). kV is the number of RPM per volt. If you use a 2 cell LIPO, it gives 7.4 volts (a bit more when fully charged) so a 1000 kV motor will run at 7400 RPM when it's unloaded. The current rating is a max - don't exceed it or the motor will over heat.

Props have 2 numbers - diameter and pitch. Diameter is pretty obvious and pitch is the number of inches (or mm) that it would travel in a single revolution (in a perfect world). You will see numbers like 8040 which means a diameter of 8" and pitch for 4". Pitch has often been likened to the gears in a car. The lower the pitch, the lower the gear - slower but with more power. In fact, low pitch props are often called "slow fly". A trainer should have a lower pitch prop.

Now the relationship of prop and motor to ESC isn't simple. In general, the bigger the prop, the more current pull and the higher current rating your ESC will need. You could get a wattmeter and test to make sure a prop+motor combo is right. Fortunately, people have done the measurements for us. Take a look at this web site: www.headsuprc.com. Look at a given motor and you will see that they have measured a number of props with each motor and tell you how they did. Here is the headsup page for the blue wonder motor You will see that for that 8040 prop with a 3 cell LIPO (11.1V), the BW produces 15 oz of thrust at 6 Amps of current draw. The pitch speed means that in a perfect world, the plane would go 35 mph. This is a good combo for the BW on a plane that weighs around 15 oz. Your ESC can handle this no problem.

Some motors are spec'd for wattage, not current. To get the current, take the highest voltage they rate it for (2 cell - 7.4, 3 cell 11.1, 4 cell 14.8) and divide the wattage by that to get the max current. For example a 120 watt motor that runs on 2 or 3 cell LIPOs will have a max current of 120/11.1 (10.8) amps.

By the way, headsup is a very good vendor though I don't know if he ships internationally.
wow awesome info

yeah i ran 8000kv brushless systems on 7.2 and 9.6v nimh nicads back in 2005-06. lipos back then was death traps plenty of bad ones. things have moved on so much i feel new to most things.

http://www.jperkinsdistribution.co.u...8/4404520a.jpg
the esc is 20a and 24amp current peak.esc was one i just pulled from lhs and found link to picture above

HACKER A20-26M is the motor i was looking at to go with the 20 amp esc above
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Old Feb 10, 2010, 11:42 AM
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The smaller they are, the twitchier they area, Of those three, I'd build the BB24 first. a 12 inch bb would be as tough to fly as the Yak, mostly because of wing loading. You will have to use pretty much the same gear/battery in the small guy as the larger(even up to a 33") so the weight the wing has to carry is mostly the same, and that means the plane will fly faster, and glide faster, (which might sound like a good thing, but isn't when you are learning - you want slow and easy so you can make a mistake and correct it before the plane is nose down in the dirt! If you remember how it was when you drove your trucks in directions other than straight away from you, and you had to practice til handling the controls got automatic? well it's the same thing only with the added dimension of vertical!)

I know that the office supply houses in UK sell foamcore boards like the stuff we call readiboard or elmersboard here in US, and there was a thread a couple pages back where a guy found another foam source in UK I think. Used to be a floor underlayment that they could get at a building supply store (unfortunately i forgot the name of the underlayment and the store had a three letter name with one being B, i think). Keep looking!

for motors and gear, the world wide winner is HobbyKing as far as I'm concerned, but I think there's another mailorder place in Europe called giant cod or something like that.
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