want to know more of Twin mico-jet from multiplex

[Babylon5]

Yes thats true and not true.

You are looking at it froma statics point of view..that is the plane is stationery... When a plane is stationery...thrust = weight...thats ture

But when a plane is moving, the equations change....

Thrust(force pointing up)= weight(pointing down) + drag(pointing down)

What Im saying is this....your thrust is no longer a constant when the plane moves...it varies with speed. You assume that your thrust is 1.2kg(static) and will be 1.2kg when the plane moves.....thats not entirely true....if you go to any motor calc program like this one here....you will notice that the thrust in flight is less than the static thrust...it is possible for the thrust to drop below the weight of the plane and hence your unlimted vertical is no longer true.....it is only true if your thrust in flight is still greater than the weight of the plane....

http://www.s4a.ch/eflight/fancalc_e.htm

Input your parameters for battery, motor and fan and play around with your flight speed value...as you increase it...you will notice the thrust in flight drops....So no matter what...you alwasy got to ensure your thrust in flight is The drag must greater than the weight fo the plane in order to have your unliimted vertical...

WELCOME TO AERODYNAMICS.....

Hi, what you say is true if the aircraft has very high drag factor.

If the plane is design properly and streamline in design like the twin MJ , the drag factor should not become an issue.

Coming back to the twin MJ ,the drag effect you mention didn't happen on this aircraft. Like many of the MPX plane , the drag factor of this plane is not significant to cause the phenomenon you just mentioned. The vertical performance is still very good with a good 3S Lipo cells.




Cheers

[Hawkeye]

Babylon.

Im merely stating that you cannot ALWAYS assume that if the static thrust is greater than the planes weight that it will do an unlimited vertical. You have to do actual test in flight to prove that to be true.

Its simple actually....on Saturday....lets point your twinjet upright 90 deg and see if it will take off at full power vertically. If your in flight thrust is still greater than your drag and the planes weight...it will launch vertically unlimited...if it rises a short way and falls...than the inflight thrust is less than the planes weight and drag. Its and easy experiment.

[joe yap]

Hi, what you say is true if the aircraft has very high drag factor.

If the plane is design properly and streamline in design like the twin MJ , the drag factor should not become an issue.

Coming back to the twin MJ ,the drag effect you mention didn't happen on this aircraft. Like many of the MPX plane , the drag factor of this plane is not significant to cause the phenomenon you just mentioned. The vertical performance is still very good with a good 3S Lipo cells.




Cheers

Huh? Excuse me. Properly designed and streamline like the twin MJ? To me, it's one of the planes with the highest drag. The thick wings are over designed due to the fact that it needs the mass of foam to achieve sufficient structural integerity. The foam finishing adds tonnes of drag which is an eyesore to a speed monster purist. All these and plus the fact that it has such a low aspect ratio wings can only mean one thing; apart from the sharp looking fuselage, it has no ingredient for the recipe for speed, in term of airframe design. Just look around. Which one of those 'jets' can really fly properly on brushed motor? My balsa plane can do much better and glide longer on the same setup.

Not to add salt into wound, these jets can hardly soar in clean configurations in Bedok reservoir slope. The Picojet can do better only at Sedili slope, but not really something that you'll really enjoy.

[Babylon5]

More video

Putting aside the difference in opinion on the thrust , drag performance
Here are some video clips that I download . Its grainy. Its divided into 3 parts.
Plane is a bit head heavy during the video short.
Pardon the grainy videos it is taken from a camera in sequence
are the Launch, mild aerobatics and some fun flypast.

http://youtube.com/watch?v=RarLXnaG9UQ

http://youtube.com/watch?v=gtd4tvmAsNs

http://youtube.com/watch?v=ZvCWaLIjcsw

Cheers and enjoy the video

[$h@d0w]

Oh man, sorry......... My question about the definition of unlimited vertical opened a can of worms. Oops.

[Hawkeye]

Where is the unlimted vetical...as in 90 deg straight up!!

Most planes will climb at a shallow angle unlimted ie: 20-30deg....


I think we have some inconsistency with the defination of unlimited vertical here....maybe it should be rephrased as "unlimited climb at angles < 90 deg"

[fuse]

agreed not many planes have unlimited verticle, most i have seen are either 3d foamy with 3:1 power plant or gliders with huge prop and suck over 100amps.


ok back to the topic,

tell us more on your set up pls. the twin jet looks like a fun plane.

[Babylon5]

Babylon.

Im merely stating that you cannot ALWAYS assume that if the static thrust is greater than the planes weight that it will do an unlimited vertical. You have to do actual test in flight to prove that to be true.

Its simple actually....on Saturday....lets point your twinjet upright 90 deg and see if it will take off at full power vertically. If your in flight thrust is still greater than your drag and the planes weight...it will launch vertically unlimited...if it rises a short way and falls...than the inflight thrust is less than the planes weight and drag. Its and easy experiment.

Hi Hawk eye, I think you misinterprete my statement. I merely stated that "unlimited vertical is possible with this setup...what is wrong with dat!.

Think for a while what the difference between a pusher and a traction aircraft.

As the aircraft travels vertical, it forward speed is reduced.
When this happened to a pusher configuration, the forward speed of the aircraft drops so low that the surface control no longer is effectivel . Unlike the traction aircraft there is no air slip slipstream to aid in the surface control for the pusher. As a result the aircraft loses stability and unable to continue in its vertical flight path. Yes drag factor reduces the forward flight but it is not the main reason and the assumption you make to describe why the aircraft is unable to maintained vertical flight inspite of having thrust to weight ratio.

For this reason a standard pusher plane will never be able to hover like a traction plane.

Regarding launching the plane vertically from ground zero. For a traction plane it is possible if given sufficient thrust.
Sorry to say I am not insane or stupid to try to launch a pusher plane vertically .

Maybe you can try your pusher plane first.

[Hawkeye]

Babylon,

If you read my explainations carefully regarding in flight thrust and drag and look at the equations very very carefully...

Both drag and IN FLIGHT THRUST are factors whether you are able to attain unlimted vertical. Not one or the other....so stop harping about the drag bit....you are forgetting to include the inflight thrust.

As for your statement..."about a possible unlimted vertical" whats wrong with that......Well forst of all I think its a misleading statement ...especially for inexperienced flyers learning....they would think...

"wa..as long my plane got more thrust than weight when i power up the plane on the ground...sure unlimted vertical"

And since you are too smart to launch a pusher vertically....than lets put the plane in straight level flight and turn it up into a vertical climb at full throttle and see it it does an unlimted vertical....time to put your statement "possible unlimted vertical" to the test..

[fuse]

relex bros, its just a discussion.. its christmas soon you know hehehhe


no need to test simi vertical la. just fly and enjoy.

cheers

[Babylon5]

Babylon,

If you read my explainations carefully regarding in flight thrust and drag and look at the equations very very carefully...

Both drag and IN FLIGHT THRUST are factors whether you are able to attain unlimted vertical. Not one or the other....so stop harping about the drag bit....you are forgetting to include the inflight thrust.

As for your statement..."about a possible unlimted vertical" whats wrong with that......Well forst of all I think its a misleading statement ...especially for inexperienced flyers learning....they would think...

"wa..as long my plane got more thrust than weight when i power up the plane on the ground...sure unlimted vertical"

And since you are too smart to launch a pusher vertically....than lets put the plane in straight level flight and turn it up into a vertical climb at full throttle and see it it does an unlimted vertical....time to put your statement "possible unlimted vertical" to the test..

Hi Hawkeye,

The Twin microjet with a good batteries will develop sufficient thrust to maintain vertical airspeed and possible untlimited vertical.
As far as I am concern this is fair statement and In am not bragging about anything or give misleading statement as you claimed.



Moreover, I did not mentioned "sure" to go vertical. I use the word "possible"
Possible= by internet definition feasible or practical

Sure(your words)= definite /certain...what a world difference
like dead sure=100 percent , certain...so your definition of "possible" is this way than I have no words to say .......

Back to your drag theory...

Your explanation would have make sense if you have given further thoughts and consider the following situation.

1.)In the pusher as the plane climbs vertically, and depending on the thrust , the plane would continues upwards. As it loses speed the airflow over the control become weak to a point where the control surface it no longe become effective.
(In a vertical climb , wing of the plane has practically no lift in this scenario, it is power by raw thrust and momentum)

2) In this situation , the plane become unstable and start to wobble and slip out of its flight path. The laminar airflow over its airfarme start to break up and induce drag causing the aircraft to slow down further.

3) The induce drag further slow down of the aircraft and situation becomes even more unstable , vicious cycle

4.) By this time the aircraft would have slow down till the control surface control is no longer operative.

5.) The aircraft is now upright and represent an object with a tall profile and is at the mercy of gravational forces ...very unstable will fall back to mother earth.

As you can see my explanation , yes drag is mentioned in this scenario but is an indirect result .

For this same reasoning and analysis, it also explain why micro-jet(single pusher) is so difficult to hand launch especially at full power.
The micro-jet elevon throw is very sensitive so the setting is very little just over 6mm-+ . When plane is handlaunched especially with full power , there is not enough air stream to maintain level stability couple with the fact the the elevon throw is so little that the plane is practical at the mercy the gyroscopic effect of the motor we call torgue.

If you think this post is nonsense you can ignore it but in the same token, i dislike pple saying I am misleading or add words to my statement.



cheers

[edmond22]

okok calm guys, buy Cold cold coke for both.

I am reading with interest. I dabble into flying wings too and to date, the fastest one I ever achieve has pretty good vertical, only the cost of it is high, about 70++ amp average on WOT. I tried several times to pull it into vertical and just let it go to see how far it can go, my eyes is the limit for now lol. but it does show a slight decay rate of speed.

[joe yap]

Unlimited vertical? Try helium filled baloon instead...........

[fuse]

Try helium filled baloon --- wahahahah yeah that works too...

[leonlio]

Unlimited vertical? Try helium filled baloon instead...........

Looks like we can put a fellow PFW astronaut in the moon liao.

Cheers,
Leon