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Old Dec 03, 2012, 05:44 PM
Pusher jets rule!
crxmanpat's Avatar
Mesa, AZ
Joined Jan 2006
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Did it seem to have enough power to fly, or was it struggling to stay in the air?

Pat
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Old Dec 03, 2012, 06:08 PM
Callsign: Jolly Roger
MyDigitalParadis's Avatar
Ridgecrest California
Joined Jun 2006
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Always check that the prop is facing the right way. Number facing forward. If they are facing back it will push but not enough and down you will go even at full throttle.
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Old Dec 03, 2012, 07:35 PM
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Joined Jun 2012
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Quote:
Originally Posted by tripn4days View Post
Yeah.... so lets just say the "pusher" design is a whole new way to fly. Maidened mine today, for about 10 seconds, 20 seconds and 10 seconds. Followed by a crash, another crash and, you guessed it, another crash

Never flown anything quite like it. Had CG perfect, wings swept or opened, didnt matter. It felt like I was trying to "surf" through the sky rather than fly. The only way I can really describe it is like trying to drive a car in reverse at really high speeds; or, trying to balance a baseball bat vertically in the palm of your hand...

::Saddy Face::

I'm kinda bummed, as I put a lot of energy into her, but that's the way the chips fall sometimes. I definitely wasnt prepared for the foreign flight characteristics. I thought it would fly just like any other plane...

But there is definitely a difference between pushing through the air and being pulled through the air. I was worried about the weight, but that didnt seem to be the issue, as at one point I accidentally shot straight up into the sky for like 60-70 feet
tripn, I'm sorry to hear about that experience. I can't help but think it's a setup error. With wings swept forward the MDC F-14 is one of the more forgiving flyers I have flown, and there are many people on this thread who have built the plane who have had good experiences with it too. With wings unswept (i.e. wings back into the body) the MDC F-14 rolls like a drill so that's something to be aware of, but easily fixed by sweeping the wings back forward.

I also feel a bit guilty because I recommended a power setup.

Can you tell us more details about how it flew, where it was balanced, the flying conditions, and how it was built? Pictures will help lots too, there may be something you missed that other posters can catch.

Based on your description, I'll echo the other posters here and say that it sounds like you are describing a tail-heavy plane. It could also be that the thrust angle on the motor is wrong and pushing the tail down (there is a very slight upthrust built into the plans). It could also be something that is wrong with your control surfaces under load. Also, as MyDigitalParadis said, if this is your first pusher you need to make sure that your prop is facing the right way (it will be reversed from what it normally is on a tractor setup) otherwise you will get very little thrust.
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Old Dec 04, 2012, 04:59 PM
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The only difference between being pushed throught the air or pulled through the air is in your mind, with a little slipstream effect on the side. The slip stream of an 8 in prop over an airplane with a 35" span is a little over 1/5 of the plane feels the slipstream. The rest is the same as being pushed. If your c.g. is correct and your control throws are right it will fly, can't do nothing but.

Check everything and try it again.
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Old Dec 04, 2012, 05:21 PM
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birdofplay's Avatar
United States, IN, Indianapolis
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Plus a prop in slot design pushes against the Vectored thrust tabs ( elevons )

With the consequence of having control-ability at very low speeds as long as the motor is running.

A slight under hand toss should get you in the air.

Bob
Hoosier Cutout Service
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Old Dec 04, 2012, 07:23 PM
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Rayonnair: Please dont feel guilty. Your setup recomendation provided plenty of power and had nothing to do the flight of this plane.


The 7x5 prop was certainly installed correctly. Likewise, the CG was spot on, eliminating the tail heavy theory....

However, I did install the motor at a slight angle, thinking it should help keep the nose up. I read somewhere on this thread that 2 degrees was the correct pitch, but I did not actually measure it. Perhaps I should have installed it square and level or taken the time to find out what 2 degree looks like...

Could slightly overdoing the angle cause a tail-heavy type effect? I would think with the elevators so close to the propwash, any angle would more or less be almost immediately negated as propwash flowed over the level elevators...

Quote:
The only difference between being pushed throught the air or pulled through the air is in your mind
I did not orginally anticipate any noticeable difference, but this thing flew like a motor boat in the air. Very wishy-washy and not very naturally inclined to go straight.

Perhaps I should have set up an expo? Again I am unfamiliar with jets and pushers and I've never dealt with a thrust vectoring design.

On the other hand, I dont fly my 3D style planes with any expo....


I would have to agree that the plane did exhibit some "tail heavy" like characteristics, but the plane balanced out well with wings open or closed. Perhaps the downforce of the engine being installed at a slight angle was to blame. I will revisit it and try again if I can manage to salvage the plane.

What does this mean:
Quote:
Originally Posted by AlfaXray1 View Post
slip stream of an 8 in prop over an airplane with a 35" span is a little over 1/5 of the plane feels the slipstream.

Check everything and try it again.

I might also add that this is my first experience with the elevon setup.
How are throws supposed to be setup? I had up/down/left/right setup correctly and responding properly, but I did not adjust the range or "blends" of throws at all...

In other words, my left/right "ailerons" travel the same distance as my up/down elevators... Is that a correct setup?
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Old Dec 04, 2012, 07:30 PM
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Old Dec 04, 2012, 10:00 PM
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Maybe you should add nose weight and bring the c.g. forward. A nose heavy airplane will fly sluggishly, but a tail heavy airplane will fly once. I fly mine on a DX8 and I received advise on this forum to mix aileron to aileron and elevator to elevator. It allows 100 throw on both controls and it made the elevator pitch sensitive but the ailerons were perfect. It is totally controllable in all realms of flight and is quite a sight in the air making a high speed pass. Mine is slightly bigger but heavier and with a Turnigy 3536-1300 and 40 amp speed control and 2200 3s pack it is perfectly powered. Not unlimited vertical but will go as far as I want it to go.

Something, whatever it may be is off slightly on yours otherwise you will be have ing a blast flying this plane.
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Old Dec 04, 2012, 11:34 PM
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Quote:
Originally Posted by AlfaXray1 View Post
Maybe you should add nose weight and bring the c.g. forward.
Yeah that's kind of what I was thinking... My original setup had the battery ahead of the RX and the plane was slightly nose-heavy. After some finagling and servo extensions I was able to switch positions. Perhaps I will switch them back and give it a whirl.

Quote:
Originally Posted by AlfaXray1 View Post
It allows 100 throw on both controls and it made the elevator pitch sensitive but the ailerons were perfect.
I think that's how mine is setup and I would agree that the elevators were a bit twitchy.



BTW, your fabulous pics are making me jealous...
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Old Dec 05, 2012, 12:37 PM
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tripn4days I found on 2 of my F14's I had to set the CG at the leading edge of the wings to get them to fly correctly. Both were over weight by 4-6 oz. Your experience seems to track mine. The last model was on target and I was able to move the CG back to the spar brace as indicated in the manual.
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Old Dec 05, 2012, 12:49 PM
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United States, CA, Aptos
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Question: how do you add pictures to these messages? I want to post photos of my plane but all I see is a link to a web site and no upload capability.
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Old Dec 05, 2012, 12:59 PM
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United States, NM, Clovis
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Quote:
Originally Posted by Poporbit View Post
Question: how do you add pictures to these messages? I want to post photos of my plane but all I see is a link to a web site and no upload capability.
When you are doing a post scroll down and you will see a click box that says manage attachments. Just click on it and you can upload pics.
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Old Dec 05, 2012, 01:01 PM
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birdofplay's Avatar
United States, IN, Indianapolis
Joined Dec 2005
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Do a Go advanced 1st then do the scroll down
to manage attachments..

Bob
Hoosier Cutout Service
http://www.balsabuddies.com/
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Old Dec 05, 2012, 03:46 PM
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Quote:
Originally Posted by Poporbit View Post
tripn4days I found on 2 of my F14's I had to set the CG at the leading edge of the wings to get them to fly correctly. Both were over weight by 4-6 oz. Your experience seems to track mine. The last model was on target and I was able to move the CG back to the spar brace as indicated in the manual.
Interesting you should note that, as my first internals setup (battery ahead of RX) brought my CG to right at the LE of the wings when open... So, I had to adjust all the internals to get CG back to the spar...

Very interesting...
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Old Dec 05, 2012, 03:52 PM
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Doing a search in this thread for CG

I found some refs and pix at post 2767

http://www.rcgroups.com/forums/showp...postcount=2767

Bob
Hoosier Cutout Service
http://www.balsabuddies.com/
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