bobmaster

what about the lipo pack.....i flew on a 1300mah and about 6 minute of flight ........what is the bigger lipo pack i can put in this airplane (f-35 or the f-4(bcz they had the same batt compartment))

opjose

The included LiPo pack sustains the very HEAVY draw of the EDF just fine.

I put a 1800mAh 18C pack into the plane and found that the EDF ran poorly because it was drawing more than this battery could provide.

You can fit a thin 2100mAh 20-25C pack in or a 1800mAh 20-25C pack, but they are longer than the included battery packs.

Initially you'll believe that these batteries WILL NOT fit... but you CAN make them fit.

The "bottom" of the plastic battery cage can be cut out.

If you do this and then file the edges of the plastic smooth, you can insert a longer pack into the space.

Part of the pack will protrude into the area in the fuselage, but there is no problem with this.

And the pack is held snugly by the sides of the battery "cage".

I found that an 1800mAh pack was about perfect for the balance and weight of the plane. It increases the flight times to about 10 minutes while not degrading flight performance.

yetti831

Wow, I'm slow. And if I'm wrong about this, I'm slower. This is going to be a one input jet, isn't it? In other words, the jet will not receive aileron AND elevator input at the same time. So, if I want to turn, I'm first going to have to aileron left/right AND THEN, once the plane has banked, add elevator up/down. Am I correct with this, or totally off base?


Thanks for your previous reply.

opjose

Not quite.

If you only use the included two servos the plane acts a bit like a delta and a bit like a 4ch plane, which is why I refer to it as a "weird" delta.

When you bank the plane the nose drops. If you then pull the nose up, you get a change in roll characteristics.

Why?

Since the ailerons are linked to the elevator, banking the plane causes one aileron and elevator to go down at the same time as the other pair go up.

Likewise if you pull the nose UP both ailerons also go UP which causes the wing to develope a bit less lift.

Sounds strange already eh?

Now if you ROLL and pull the nose up, one of the ailerons changes angle against the nose up movement which acts to work against the nose up movement a bit so the vector of motion goes off at an upward angle.

Yes you CAN fly the plane this way, but it is very strange and not optimal.

yetti831

Very clear. Makes sense. Thanks! I thought my logic was strange at best.




P.S. Do you have some sort of technical degree or related work experience, or are you self taught?

bobmaster

I think that an investment of 40$ to add 2 more servos sounds a great idea to me. But adding two more servos it's a kind of challenge for a beginneer like me lol....

Simon

opjose

Actually it's very easy.

The cable is already in place. All you have to do is fix the servos in place connect the cable and set up the linkages.

I went a bit further and chopped down the cover to hide the new servos, but there is no need to do this.

I illustrated all of this in the build video I did...

bobmaster

Did you post your video, Idind't see it on the video link....

opjose

I mentioned that it will be 2 to 3 weeks before the videos are ready.

yetti831

I like this thread for some reason.

Anyway, I know that you said the 3500kv is more suited to an EDF or a geared motor, but can I remedy this problem with an appropriately sized prop?


As for the brushed setup, the slowdown was apparent in and out of flight.

opjose

Re: Prop

Well you would need a smaller prop and it would be spinning like a little bee!

Remember what is happening is that the motor is spinning the current prop so fast that a large part of the blade is fully stalled.

You could probably drop the existing prop diameter about 1" or more and also the prop pitch by a number or two.

This would increase the efficiency.

Frankly that motor is better suited to a gear drive with a 2:1 reduction.

If you did that you could run the same or a larger prop to give you more thrust.

Post a picture of how you have it mounted if you can.

It may be possible to use an in-line gear drive depending upon the mount.

yetti831

What is physically happening to the blade when it stalls?

What is meant by a gear drive with a 2:1 reduction?

And, lastly, what is an in-line gear drive? [&:]

My motor is mounted in the pod just like the original. The ESC is taped to the top of the fuse.

[link=http://site.wonderhobby.com/wildhawk_1.JPG]Wild Hawk Mount[/link]

opjose

Re: Stall

Much like a wing, the blade is not producing lift.

The laminar airflow has separated from the surface at this point, and the prop is merely spinning freely.

The blade is just a small "wing" after all.

Re: Reduction

A "reduction" drive "reduces" the number of revolutions seen at the prop by a factor.

So your 2500Kv motor when hooked to a 2:1 reduction drive, will produce approximately 1250 revolutions per volt.
That is still a bit high so maybe a 2.5:1 may be more in order.

This is like a "low gear" on a car. The motor spins more freely, but it produces more torque, allowing it to spin a larger prop, which spits out more thrust.

See: [link=http://www.bphobbies.com/view.asp?id=A1250118&pid=V787009&img=l]Click me![/link]

For an example.

Re: In-Line

An "In Line" or planetary gear drive does the same thing but it does not offset the prop drive spindle...

See:

[link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXHA26&P=ML]Planetary Gear Drive Click me![/link]

Re: Motor

How is the motor held in place?

The original was gripped by the foam pod, but with an Inrunner, you would not want to do the same thing, as it would prevent the motor from cooling properly.

yetti831

I just got back from taking the hawk out. Throttled up as much as possible before the prop stall. First two tosses failed. Not enough power. Was ready to chalk it up as a learning experience but I wanted one more toss. A bit more throttle and up she went. Albeit slowly. Couldn't get up more than 30 feet, and she was cruising at approx. 20mph. An attempt at a significant pitch produced an immediate stall. As I hadn't flown the hawk with ailerons yet, I attempted to bank. FAIL. Full left or right aileron produced more of a yaw effect, and I couldn't turn without rudder. Ailerons are about 14 inches long, 2.5 inches wide. Secured with strapping tape. Plenty of throw. A bit of a gap between the wing and control surface. Flight time was about 6-7 mins. She landed beautifully. What's the problem with my ailerons? [&o]


I've since removed the motor (I'd rather not say how it was secured [:-]). I'm picking up a sweet combo from grayson hobbies for the hawk. [link=http://www.graysonhobby.com/catalog/product_info.php?cPath=22&products_id=414]Combo[/link]

Thank you for your responses to my other questions. It's all starting to come together.

opjose

Well that's another high KV motor... almost of the same rating!

You could merely try the PROP they recomend for that motor instead of replacing the motor, as you are using pretty much the same thing.

I don't know how you plane on mounting that outrunner.

Remember: Lower KV motors produce LESS RPM but can utilize larger PROPS for more THRUST.

HIGHER KV motors produce HIGH RPM's but cannot use larger PROPS, you must use smaller props with a bit higher pitch for more "pitch speed".

Pitch speed meens the airflow coming off the prop is faster ( usually resulting in faster flight - IF - there is enough thrust to get the plane moving ).

It's all a balancing act... You need sufficient thrust and enough pitch speed so as not to stall the plane in flight.

-

Your Hawk was flying just above stall speed.

The ailerons were not effective.

The dihedral of the wing and wing tips overcame any attempt at rolling the plane.

To make the ailerons effective you will have to fly the plane faster, by fixing the motor/power problem.

yetti831

They recommend from a 4x4 to a 6x4 prop. You said I should drop both in diameter and pitch, so get a few 4x4s? Here's a video of a guy who mounted that wellgard. [link=http://www.youtube.com/watch?v=V7jxgDZvWPk]Hawk with Combo[/link]


Yes, I was thinking that because I was flying so slowly they weren't effective, but I wasn't sure.


If I am to re-mount the inrunner, how would you recommend I go about doing it?

Also, in the time being can I put the fan from the f-35 on it? [&:] I know, I'm impatient and I tend to do things half-assed. Apologies in advance!

opjose

Sure, remember though that because your existing inrunner matches the KV rating of this new motor, all you need to do is merely put in that smaller prop, and you'll get the SAME result as with the Wellgard.


Well... the problem is that the mount was designed to grab the "can" from a brushed motor.

I would be looking at a making, buying or designing a retention system for the inrunner, and then opening up the front of the foam "pod" so that air can travel accross the motor when the plane is in flight from front to back.

At this point I start looking through BPHobbies, Tower Hobbies, or Hobbie-Lobby catalogs to see what might be adapted. The latter being the most expensive, but having a great selection of unsual mounts and parts.



Nooooo don't do that!

That EDF fan is designed for well an EDF, and will produce even worst performance than what you are getting now with the inrunner motor and the default prop!

yetti831

Jeese. I can't find any 4X4 pushers. Can you direct me to some? Thanks for everything.

I see GWS 4x4s, but they look like crap.

opjose

Who said you need a "pusher"?

Sorry Yetti but I forgot you are new to this...

One of the great things about brushless motors, is that if the motor is running in the wrong direction, reverse any TWO of the three motor wires and it will change the way the motor spins...

Well what does this have to do with Pushers?

You don't need them!

Mount a standard prop BACKWARDS then reverse the leads and you are done.

yetti831

Haha. Yup. I figured that one out yesterday when the prop was mysteriously moving the wrong direction. Just switched the red and yellow leads. BAM!

Just purchased 6 4x4's from advantage. 88 cents a piece. You must buy 6. Oh well, I'll need them.

opjose

Hey Yetti check this out!

[link=http://knifeedge.com/forums/downloads.php?do=file&id=8303]Wild Hawk (stock with wheels)[/link]
[link=http://knifeedge.com/forums/downloads.php?do=file&id=8302]Wild Hawk Stock[/link]

yetti831

Can't open the file. It's an .rfx extension.

Did you pick one up, or is this some mod flying?

opjose

These are models for Realflight G4.x.

I thought you would find it interesting especially since the author did something similiar to what you have done ( see the notes ).

When I first saw the post, I though maybe you had done this ( the timing was auspicious! ), until I remembered that you said you did not have G3 or G4.

yetti831

Oh, I see. Yeah, I've always just used FMS.

It was probably ******** himself who posted the files. He pimps the wild hawk pretty hard, and it's safe to say that his review is very biased.

For one, anyone who buys the wild hawk as a first plane will have a difficult time turning the hawk. The rudder is wildly ineffective, even with the clevis on the innermost hole. But for 80 bucks you can't complain.

opjose

Good to know. That gives me a point to compare the G4 model's physis against too.