THE ALPHA JET MK2 -FRCFoamies

Discussion in 'FRCFoamies Plans' started by F1wanabe, Jan 6, 2014.

  1. Sterling101

    Sterling101 Top Gun

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    I've accidentally just put a 7x3 prop on to try out. I may regret it but I feel more speed always helps ;)

    Edit - just thrust checked it. Plane comes in at 690g (24.34oz) and I hit 1209g thrust (42.65oz).

    Should go well enough I think...
     
    Last edited: Nov 10, 2016
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  2. Sterling101

    Sterling101 Top Gun

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    OK, so managed to get a quick flight in despite it getting close to freezing out there now.



    Conclusions...

    1 - it's quick, and take off is like a rocket
    2 - even though I had the balance about 10mm forward of the CG mark it still wanted to point it's nose up a lot
    3 - it's rather noisy and although it's balanced the prop seemed to hit resonances at certain RPM's
    4 - did I mention it's rather quick when you open the taps??

    All in all I think I'll stick with the 6x4x3 prop, possibly with a 2600kv motor. For noise and torque roll reduction mainly, but it was a good test and at least this time the camera was pointing where I wanted it to!
     
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  3. F1wanabe

    F1wanabe Administrator

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    Sterling, a couple points about this plane and how thrust effects it that may help. Dave, Jay and I had a good convo about the black magic or voodoo going on in between the wings. First, because of Jay's bi wing design with the prop wash being pulled through the plane, it will be loud! The more thrust the louder, the less thrust the quieter. A lot of thrust on this plane is not as important as enough thrust. My 2s plane with a 7x3.8 wsf prop is pretty quiet because the airflow is slower through there, but the speed is really good! It's a 15 oz plane with 18 oz thrust on 2s and its spectacular. On the other hand, the more air you push through with a larger prop the more resistance you get as well, which can limit performance. We've found that the smooth airflow through the plane is key to good performance so the 6x4x3 prop will probably provide more well rounded performance and beveling the leading edges of the depron helps air flow pass through smoothly. This maximizes performance since the stability, high alpha and aerobatics depends on the proper airflow between the wings. I also like the rear edges beveled, btw, because that decreases turbulence leaving the plane. In the end, flying this in the slow to medium speed range gets the best results. That's one of the main reasons why this is a great night flying plane because you can have stability while low and slow. Hope that helps you with the power system choices.

    Goodbye Note 7 Hello S7 Edge!
     
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  4. Well had mine out again tonight, success with failure again. It flew but having issues with roll, you could go to bank/turn and very little response and then sometimes it was like a drill, just wicked roll. Once the video is uploaded about a minute into there is a super fast roll, I didn't plan on doing that, I was very gentle on the sticks. Another time it started banking one way (slowly) but I had to be aggressive on the stick to reverse it, pitch is/was good or easy to control. New nose required again. :( :(
     
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  5. F1wanabe

    F1wanabe Administrator

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    Wild thing, did you increase expo on the alpha jet? Is it possible that expo is high so the response isn't good until you move the sticks pretty far at which point the response kicks in? The other thing is that the alpha jet really depends on thrust vectoring so if you are maneuvering with lower throttle settings then response may be less than a regular parkjet.

    Goodbye Note 7 Hello S7 Edge!
     
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  6. oh nooo! how did that happen? Fortunately, a nose job is fairly easy to do on this...
     
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  7. Here it is, short and sweet. :D

     
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  8. Actually last time out I lowered the expo, it would almost be where you thought you had a handle on it and bang it would try to ditch you. :D
     
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  9. Sterling101

    Sterling101 Top Gun

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    Great info Greg.
    Sort of confirms exactly what I'd found as the larger size and pitch, although over all faster, gave more stability issues and a lot of noise over what you'd normally expect.
    Hopefully the weather holds on tonight to test motor/prop combo number 3...
     
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  10. Well it's back together again ready for another test flight. Went through all the control surfaces, control horns servos and such to make sure everything is proper and equal, all good that way. 2 or 3 flights ago I had raised the expo and then lowered it right after that, I may even lower it some more. The unexpected roll was at 36 seconds of that video and the end of the video, not sure if it is just stalling out and falling over or what but I may try it a little more nose heavy and more thrust (4S) ;)
     
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  11. Sterling101

    Sterling101 Top Gun

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    Managed a couple of flights tonight with the new prop and slightly adjusted control settings.
    Found I had the expo too high on the aileron I think - seemed hard to roll but flew ok generally.
    First launch was a bit too nose heavy, but second was ok. Wind was very odd tonight though. Kept gusting from different directions so just did general flying rather than too much aerobatics...

     
  12. Well, daytime and decent weather lets take this little piece of foam out and make or break it. :D , I figured lets try it on 4S, make it nose heavy and give it a ton of thrust well it barely got off the ground, somewhat hard landing but only broke the prop so home I went just disgusted with this plane. I was thinking to myself it flies worse then my Batwing. (Sorry Guys) So worked on the new plane , ate supper and of course it's dark by 6pm now, I looked at the wife and said grab a flashlight light and lets go for a ride. I figured it didn't like nose heavy so let's make it tail heavy, instead of a 2200 3S battery which balanced nice I went to a 1500 3S battery, pretty tail heavy, I ran the whole battery and landed softly.



     
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  13. Sterling101

    Sterling101 Top Gun

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    Quick flight of the Alpha Jet this morning. Nice weather for a change!

     
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  14. Sterling101

    Sterling101 Top Gun

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    Popped a quick flight in this morning to see if I could get it dialled in as it's a lot tougher to do in the dark.

    Seemed ok but I think my aileron rates need upping as I seem to struggle on the roll side of things. Other than that quite a nice morning for it really. Made a nice change not to be blown away or rained on :D

     
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  15. Sterling101

    Sterling101 Top Gun

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    Managed a couple more flights this morning post Spitfire crash.
    Tweaked the aileron throws up a bit and it flies great now. Very impressive flight envelope and now I know it's trimmed nicer for night flying too :)

     
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  16. Boxermad84

    Boxermad84 Administrator

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    OK, if you guys have the flight simulator phoenix, you need to check this out!!

    FILE DOWNLOAD HERE




    alpha 3.png
     
    Last edited: Dec 3, 2016
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  18. Boxermad84

    Boxermad84 Administrator

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    Oh no, sorry about that. Maybe someone could do the other sims if they have the knowledge.

    Sent from my SM-N9005 using Tapatalk
     
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  19. Sterling101

    Sterling101 Top Gun

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    Downloaded, flown, tweaked in the editor and flown again - flies just like mine now :)
     
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  20. Boxermad84

    Boxermad84 Administrator

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    Excellent sterling! Its fun isn't it? We might have a couple more in the works to!

    Sent from my SM-N9005 using Tapatalk
     
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FRCFoamies Plans FRCFOAMIES ALPHA JET MK1 Apr 24, 2012

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