Just purchased your extra 330 kit (fd003_extra330l-arf) .
I hope you can help me with battery and prop size .. the manual was very vaque.
I am using the bp motor a4120-7 and hoping to be around 800 watts.

So I need to know if 3-4-5 cell lipo and what size 3000-3200-mah etc.
I assuming a 12-13 inch prop but not sure what pitch.

Any information would be good , thanks .

The best thing is to learn how to do the relatively simple math involved.

I just answered an almost identical question on this thread: [link=http://www.rcuniverse.com/forum/m_9124560/tm.htm]Click me![/link]

BTW: I also ordered that plane...

With an expected weight of 5.7lbs I'm looking for about 140-150watts per pound performance.

That works out to...

5.7lbs x 150watts = 855 watts

So you are right in the ball park with your 1000watt max motor. You should get GREAT performance.


BP's site says:

"Use this motor with 4-6 cell Li-Poly packs and 11-13 inch props on planes up to 8 lbs flying weight. We suggest propping for around 800 watts continuous. Manufacturer suggests a 12 x 8 prop on 5 cells or 13 x 11 on 4 cells. "

I would do as indicated, and put a good watt meter on the plane, to see where your power system comes out.

If you are drawing less than 800 watts, increase the prop size and pitch. If more decrease it.

Rememeber that the higher the voltage goes, the more current draw, which you need to offset by DECREASING your prop diameter and/or pitch...

Also, assuming you go with a 12 x 8 prop on 5 cells...

3.7v x 5 = 18.5v

800 watts / 18.5v = 43A so you'll need an ESC capable of at least 45A @ 18.5v.

Most ESC's are rated at 11.1v, and as you increase the voltage, the rated amperage the ESC can handle DROPS...

I will be using at least a 60A ESC as a result.

Also remember that most ESC's which have on board BEC's, have "linear" ( aka ANALOG ) becs unless they specifically say otherwise.

Analog BECs really cannot handle more than 11.1v and even then their performance is MARGINAL.

You'll need to either purchase ESC's with SWITCHING BECS ( a more expensive proposition ) or use a separate BEC capable of dealing with the higher voltage ( a MUCH cheaper and what I normally do ).

Thanks for the reply.. I have a decent watt meter .. I also am flying the eflite dueces wild with the high power setup.
That plane is running 2 60amp esc , 2 32 series motors and 2 4000mah 4 cell batteries and 12x8 props. When I watt meter
this plane I am at 1975 watts on 10lbs of plane.. so almost 200 watts per a lb. What I would like to do is try to use these batteries
or my 3500 mah 25 c 3 cell batteries.. but im not sure on weight and balance . It wont do me anygood to use larger batteries and add extra weight.. the trade off is not worth it. But then on the other side of the coin .. smaller batteries wont hold up to hard flying and will be shorter flight times. Im not looking for hard core 3d flight , but would like enough power for verticle climb and good aerobatics.

I dont know were the cg is with the batteries installed.. so I hoping these batteries will fit.. other wise I would have to buy new batteries.. I really dont want to invest in 5 cell units .. just for this plane.. I keep some cost down by cross using batteries.

Motor is on order and plane is asssembled .. so I will see were the cg ends up with my batteries. I guess I could double up 2 4 cell packs that might be a tad smaller in size .. mine are kinda long in length.

Do you have any info on battery location and size.. this always seems to be the hardest thing .. battery placement with regards to balance in weight and power .

thanks again

plane is nice kit .. little rough on instructions hope it flies as nice as it looks.

One of the reasons I ordered this plane was the rather ample space for battery placement visible in the photos.

I should have mine tomorrow.


I am planning to use some 5000mAh 14.8v packs I have on hand, or at worst two 3850mAh 14.8v packs at a time, as I also have a bunch of these.

Given the easy access I'm not too worried about having a hard time finding placement for the packs.

Given the wingspan, I doubt you need worry about your 4000mAh pack weight.

-

BTW: Have you weighed the plane w/o the electronics installed?


I don't know where the 20-25A ESC figure came from in the advertizement, unless they calculated based upon a high voltage setup... something that should have been mentioned!

I also noticed that 25 amp esc rating and thought that was way to low. Good to here abouth what batteries you are using.. maybe I will try my 14.8 volt
4 cell battery. The weight of the plane less battery / motor and esc is 3lbs 8 ounces. Looks like it will be around 5lbs 8 ounces. So technically anything over 600 watts should make this plane
perform pretty good. excluding real 3d hovering etc. Still like the 800 watts or higher !!!

hope to maiden it this weekend weather permitting .. will see.

3.8lbs is good indeed!

If I recall correctly my 5000mAh 14.8v packs weight about 14-15oz.

So I should come out closer to the 4.8lb mark or so... not too bad!

Well I got my plane.

Very interesting!

I did NOT expect the fuselage and wheel pants to be made of heavy plastic.

Not that I find anything wrong with what they did. I have just never seen plastic over ply formers!

The material used however looks like it may hold up better than fiberglass. The Wheel Pants and Fuselage are THICK, unlike some other plastic ARF pants and parts I have seen from many manufacturers.

The wings, rudder and elevators are all Balsa/Ply.

All surfaces except the rudder are pre-hinged using a top side type hinge often seen on say the Composite-Arf giant scale planes.

The included hardware is pretty good for a plane in this size and price range, and the aluminum pull-pull is a nice touch.

The elevator pushrod is identical to that used in larger CMPPro planes.

I have NO problems getting a 5000mAh battery pack in there, and you can easily get in a 5000mAh 4S through 6S pack.

The plane uses standard size servos all around.

There is a provision for an arming switch it seems.

The entire top quickly pops off at the field, via two easily accessed releases. I would suggest hardening the holes with CA.

The gear look strong and well attached though I will also harden with CA and re-inforce with more epoxy.

The plane appears to be manufactured by CMP, and many of the parts are labeled China Models Pro.

I got mine together using a 4 cell 4000 pack 20c .. with a 60a eflite esc.. spinning a apc 13x10 prop.
Watt meter reads 675 watts at 45 amps. weight is around 5lbs 4oz. Running that larger bp motor.

I expected more watts .. according to bp chart is should be around 800 watts.. seems low.

I did the verticle hold in place while throttle up test and it almost jumped out my hands.

So now I have confused myself... larger diam prop will draw more amps and watts right?

So if I go to a smaller prop it will draw less amps and watts.. but it will spin faster right?


So what is better.. im not flying 3d just precision aerobatics.

hope to fly it tommorrow.

In effect YES...

But remember that the reason you are not seeing the expected draw, may NOT be due to the motor and ESC.

With that prop you should see more draw, so it is likely that your battery packs are not up to the task.

Get a parallel battery adaptor. They are relatively cheap.

Hook two of your packs together to the adaptor, then to the ESC. This effectively turns them into one much more powerful pack of the same voltage.

e.g. if you are using 4000mAh 14.8v packs, with the adaptor they become one 8000mAh 14.8v pack.

Then try your test again with the watt meter.

If the watt level goes UP ( which I suspect it will ) your packs are to blame, and you may need to fly with two packs at a time in parallel.



Correct up to a point.

People often forget or do not understand that our 3 phase brushless motors are effectively ALWAYS trying to turn at maximum RPM.

All the ESC does is to reduce the electrical pulse width to keep the RPMs under control.

At full throttle the ESC should have the pulse width as wide as possible, permitting the motor to get maximum energy.

Hopefull the current delivered is enough to get the prop up to 80% of the planes rated KV measure.

So if you input 10v on a 1000KV motor, your motor SHOULD spin at around 8000 RPM at full throttle.

Why not a full 10000 RPM?

Because that other 20% is our effective "reserve" that kicks in when the prop "unloads".

So even with a smaller prop, there is an effective limit on the RPM's.


I wouldn't go crazy worrying about RPMs. Instead target that watt and amp draw figures.

Those will help you the most getting things set up.


Also remember that you are measuring CONTINUOUS current, while the specs give you BURST current.

Max burst current only occurs when the battery is freshly charged, and the plane is pointed straight up, while the engine is at low idle, and you quickly run the throttle up full.

At that point in time the batteries deliver FULL voltage, ( hence your burst current ) and then drop off VERY quickly.


But your best test is to do the parallel hookup I mentioned before.

Thanks for that advise I will try that test. I did fly the plane this morning.. but had a little oops .
I had the elevator set with to much down trim.. and on take off she bounced hard into the tarmac and caught the prop ..
that exploded into bits and peices ... and catapaulting the plane 25 feet into the grass on wing tips. The only damage was the prop ..
1 wheel pant andmy battery mount . So i put on a 13x8 prop removed the damaged pant and taped the battery in . After setting the elevator trim properly
it took off much better.. a little right aileron trim and some elevator trim and it flew pretty good. I could not put it thru its paces because the battery wasnt really tight.

So I will fix it up .. get a another 13x10 prop and try it again this weekend. It seemed to have plenty of power.. but I did not do any stunts or verticle climbs. Otherwise no bad habits..

stalls nice and straight and flies solid. Landing seemed a little hot but ok. Got a lot of comments on how nice it looked and what gear I had in it.

It sounds like you have a fairly good setup.

Now you need to get it dialed in.

Where do you have your C.G.?

I went with what was in the manual. Ended up using a 13x8 prop .. around 555 watts and 39 amps. I will have to get some 13x11 props broke my only one.
Pretty stout airplane.. crashed pretty hard on that takeoff .. very little damage.

I flew it over the weekend..nice plane. I was looking for something a little larger than your average parkflyer.. and
also wanted a nice aerobatic aircraft. This thing is rock solid.. flies inverted with little or no trim.. will knife edge forever.
precision 4 -8 point rolls .. wont wander flies great. Will perform on 1/2 -3/4 throttle wont go unlimited verticle but will do a
out side loop with out much problem. Using a g force 4000 mah 4 cell pack rated at 20c get about 6-8 min of flight.
The only thing is it lands hot and fast .. and the wheel pants always flip me in the grass. I also like the removable wing , without any tools needed makes for easy set up and transport. For the money this is a nice plane.. I also purchased a ultimate from nitro planes last year..same kind of performance... I give nitro planes thumbs up .

You may want to take it high, and bring it to a level but full stall, by powering off, then holding the stick back all the way.

It may surprise you.

It does not seem to drop a wing, but initially it will seem as if it needs to land hot.

The above test should show you how slow you can actually go.

I'll bet you can drop it into a decending approach at a much slower speed than you are attempting.

I will try that next time im out.. also could use the flaperon/elevator trick. But will wait with that to I get a real solid feel on the landing speed .

Also is there replacement parts available for this plane .. just in case . I already broke the wheel pant.. but a little epoxy fixed that up.

Heh, for the cost of this plane, most replacements would constitute a new plane.

Bear in mind that things like the Wheel pants are relatively easy to find by substituting others.

I have many laying around from other planes that would all work, as the size is pretty similiar to a 40-50 size plane.

White, or red pants will work.