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Old Jul 23, 2011, 02:46 AM
Bond, Hotglue Bond
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Alpha Jet 64mm

This is my short lived Dassault Alpha Jet.

Very easy to assemble: no more than 2 hours. No glue included so I used 15min epoxy for wings and tail surfaces and UHU-por for the rest.

Plenty of space to move the battery back and forht to ensure a proper CG. But the strap installed is too big and cannot secure the battery.

The CG is ok as per manual. Is difficult to identify but if you take as reference the "dog teeth" on the wings, the CG is in line with them.

I used 2200 mAh 4s batteries: nano-tech and normal Turnigy, 35C and 40C. In average I got 3min of flying time with them.

The plane is quite fast, very stable, the manouvers are relaxed, the roll rate is ok, not very fast but straight.

I flew with and without wind and no issues here.

The EDF is well balanced and powerful enough for some vertical climbing.

Landing is a horse of another colour. The sink rate is high, so you need to keep some power (~25pcnt) until she touches the ground before killing the motor.

The weak point is the odd LG placement and securing method.
On my second landing, the plastic attachment was un-glued.
The LG wire is quite weak and flimsy. Consider changing it.
I used rubber bands to link both legs together. Later I will put a fishing line to ensure the LG is not wobbling.

It even includes an external UBEC (Bravo HK!) to manage so many servo .

After 9 flights The plane on a crashed due to a wing detached in flight.

I was glued with a lot of epoxy. But it seems that the EPO don't like this glue.

Here is the video. You can see the wing falling after the plane crashes.

Hobbyking 64mm EDF Alpha jet losses a wing and crashes (1 min 5 sec)
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Last edited by Tartago; Aug 29, 2011 at 06:55 PM. Reason: Add video
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Old Aug 29, 2011, 06:44 PM
Bond, Hotglue Bond
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Alpha jet repair

Since all the electronics were ok I decide to give her another chance and rebuilt her using mostly hot glue to avoid Epoxy, that is not compatible with type of foam. (In other EPO planes I had no issues, but on this one the Epoxy peels off like white glue)
After 2 sticks of glue I got the results in the pics.

Not elegant, but at least practical. I love EPO!

To ensure the wings attachment I added a CF rod connecting both halves. I glue them with CA and contact cement.

I fixed the LG flimsyness with hot glue also.

I will re-maiden her soon.
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Old Dec 27, 2011, 07:20 PM
Bond, Hotglue Bond
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Due to interference the Alpha crashed and got totally destroyed.
Worse thing is that I arrived to the crash site after 3 minutes and somebody took out my receiver.
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Old Apr 28, 2014, 01:32 PM
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Hi, could you give, the excact position of the cg???
it would be off great help. Thanks
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Old Apr 29, 2014, 11:14 AM
Bond, Hotglue Bond
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Originally Posted by colinski View Post
Hi, could you give, the excact position of the cg???
it would be off great help. Thanks


Colin.

Notice the dog teeth near the half of the wing.
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Old May 01, 2014, 04:50 PM
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Hi,

I tried flying it with the cg on the dog teeth point.
What happened is the jet ballooned straight up after release, (I took off the gear to hand launch it.)
So I guess it was really tail heavy??

It came down flat on it's belly, damage was minimal, i was lucky!

I guess the cg needs to be more to the front?

But how much??

I read somewhere that it is 110mm aft of somepart of the cockpit???

Hope some one can help me out!

Thanks
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Last edited by colinski; May 01, 2014 at 05:12 PM.
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Old May 01, 2014, 06:42 PM
Bond, Hotglue Bond
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Quote:
Originally Posted by colinski View Post
Hi,

I tried flying it with the cg on the dog teeth point.
What happened is the jet ballooned straight up after release, (I took off the gear to hand launch it.)
So I guess it was really tail heavy??

It came down flat on it's belly, damage was minimal, i was lucky!

I guess the cg needs to be more to the front?

But how much??

I read somewhere that it is 110mm aft of somepart of the cockpit???

Hope some one can help me out!

Thanks
Colin:

I remember this jet as having just enough power to take off from the runway.
I can't say anything about hand launch, since I haven't tried it and because on hand launch there are other factors as angle and arm strength.
Keep searching on the full thread about this plane.
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Old May 02, 2014, 02:38 AM
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Maybe this will clear thing up a bit:

Some possible situations:

ONE



Above: CG position measured from the wing root at 110 cm.
The wooden stick shows where the cg line crosses the wing leading edge.

TWO



Above: again measured from the wing root. CG now at 130 mm.
The wooden stick is now in line with the point where the wings changes it's chord.
I used the point from the "dog teeth" here as a reverence.

THREE



Above: Now the CG is aligned at the break in the wing chord. In my test flight it was way to tail heavy. And I guess it is not the best position to chose.

My best guess right now is option number Two.
What do you think is right???

Hope to hear from you soon.

Thanks
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Last edited by colinski; May 02, 2014 at 02:44 AM.
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Old May 02, 2014, 06:03 AM
Bond, Hotglue Bond
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I would say with #3
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Old May 05, 2014, 12:16 AM
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Hi,

I flew it yesterday using the cg described in situation 2 in the post above.
About 125-130mm measered fron the leading edge from the wing root.
There is a small panel line which can be used to identify the spot to place your fingers when balancing.
I used a 4s nanotech 25-50C, which I placed in the lipo compartment I did not have to move it to get good balance. The end of the lipo touches the small foam ledge at the far front of the lipo bed.
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Old May 05, 2014, 04:25 AM
Bond, Hotglue Bond
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Quote:
Originally Posted by colinski View Post
Hi,

I flew it yesterday using the cg described in situation 2 in the post above.
About 125-130mm measered fron the leading edge from the wing root.
There is a small panel line which can be used to identify the spot to place your fingers when balancing.
I used a 4s nanotech 25-50C, which I placed in the lipo compartment I did not have to move it to get good balance. The end of the lipo touches the small foam ledge at the far front of the lipo bed.
And how was it?
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Old May 05, 2014, 05:43 AM
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And how was it?
Hi,

It was really nice, launch was still kind of balloonish on the first throw.
But on the second I threw it straight, and it took off nice.
CG seemed spot on.

I never flew a jet that has a high mounted wing, so I was suprised on how docile it handled. Needs a bit more authority on the turns, so I will probably mix in some rudder with the ailerons.

Power level was okay, although I kept it on 75% to 100% power at most of the flight. At WOT it drawls about 43A and puts out about 530Watts. Although it flies okay, plans already made to swap out the power plant with a Hofmann mighty might and GWS 64mm edf impeller.

Will keep you posted!
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Last edited by colinski; May 05, 2014 at 10:10 AM.
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Old May 06, 2014, 12:31 AM
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Here ya go!

Alpha jet 64mm edf (3 min 49 sec)
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Old May 06, 2014, 08:23 AM
Bond, Hotglue Bond
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Excellent flight!
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