sargentw

I learned how to fly with a Firebird II. The plane now has the hotter batteries and the speed wing. I've used plenty of extra strong crisscrossed fiber packing tape (A10 warthog tape!) to make the plane indestructible. This is an excellent plane for learning how to toss, turn, and land. Don't fly too high on windy days. No way to get it down quickly.

I have trouble with my Aerobird getting the two tail screws set properly so the rudder and elevator work correctly. It would be nice to know where the COG point is supposed to be measured from the leading edge of the wing because there is a little room for the battery to go forward and aft. Do anyone have any tips and suggestions for trimming and flying the Aerobird? I want to get my confidence level up with the Aerobird so I can go higher, but so far performance seems unstable and unpredictable.

I've moved on, and I have no problems flying with my tiger moth and Slow stik. I'm getting ready to Order a Graupner Terry, however, I would like to get the AeroBird flying as well.

Thanks,

Tad Sargent


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HitecRedneck

Normal CG is 25 to 30 % of wing cord. Try 25 first and then if still nose heavy go to 30%.

sargentw

I'm posting some new information I've discovered that helped me and will save other Aerobird flyers. For newbie’s it would have been nice if the Aerobird Fuselage came with markings for the COG by the manufacturer.

I discovered that both my Aerobird bodies (yes two) COG's were way off and the plane was flying light in the nose. I discovered after many crashes that the COG has to be checked and corrected if needed regardless of whether the kit is said to be "RTF" right out of the box. In addition, newbie flyers need to be checking the COG, especially if they have repaired, the plane with strapping tape, epoxy or fiberglass. To balance the plane on the correct COG point I removed the nose foam, moved the battery forward, and placed some lead in the nose. The plane now flies like a demon even in wind!

To compute the COG point for the Aerobird do the following:
The wing at the center is 120 mm wide. With a ruler measure back 30 mm from the leading edge of the front wing slot and mark the fuselage on the side with a permanent marker in such a way that it can be seen when the wing is on. For the Aerobird 30 mm (25% of 120mm) is a good COG point to balance the plane.

My dad, a retired Aerodynamic Engineer and cross country sailplane flyer provided me with a paragraph about COG to help answer my question about what does "Normal CG is 25 to 30 % of wing cord. Try 25 first and then if still nose heavy go to 30%" mean.

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Tad,
What he means is you should ballast your model so the CG is at 25% of the wing root chord. If the resulting flight path with that setting is marked by a series of swoops and stalls when hand launched the CG is too far forward. Remove some weight from the nose so the balance point moves rearward, for instance, to 30% of the root chord. With this setting the swoops should be less severe. What you would like to achieve is a gentle phugoid oscillation where the model is gently exchanging altitude and flight speed (potential energy vs kinetic) without a noticeable change in flight attitude. As the aft movement of the CG progresses you will hit the aerodynamic neutral point (probably around 40% to 45% of the root chord). The model when so trimmed will then continue on whatever path is initiated until given a control command. Control sensitivity will be extreme. Usually we like to move the CG a little ahead of the neutral point, just enough to produce reasonable flying characteristics. In this trim configuration the stabilizer is not producing a lot of negative lift and drag. If one is being bounced around in a thermal a little sky keeping stability is very helpful otherwise you will be trying to correct disturbances when you can't really see what's happening.
Good lift,
Pop

Thank goodness for Dads!!

mikenlapaz

If Pop sends you any more paragraphs of wisdom, share them on this thread!
Answered questions I had not even thought of yet. He expresses himself very clearly.
Now to research Just kidding everyone knows what that is!

aeajr

My Feedback: (2)

I fly an Aerobird, which is the top of the line in the Firebird Series from HobbyZone. From what I read, all the planes in the series are fun. I have also had great experience with the HobbyZone support folks. So read this as a happy flyer who wants to make these fun planes even better.

There is one weakness in the series that is easily fixed. The motor mount is weak. A hard hit into the ground or a tree can shift the motor, or disloge it completely, as it did on mine. But, with a small modification, this weakenss can be corrected and you can enjoy lots of fun flights with these "birds" Read my post and see what you can do to prevent this from happening to your "bird".

There are also other planes that have similar bodies. Planes like the e-gull, the vector and the t-hawk, just to name a few. They may benefit from this modification as well.

What Happened?

Last week my Aerobird took a good shot in a hard, nose first, landing causing the motor to break free of its mounting and shift forward inside the plane. I have since learned that this is not uncommon. Also, while mine was dramatic, if it is only a small displacement, you might not notice it, but the motor can get out of the proper thrust line causing the plane to fly to one side or the other.

After some experimentation and excellent advice from other threads, I have begun to rebuild the Aerobird and repair the damage done by the forward shifted motor. There is a link to photos below.

What some other people have done:

Several people created some kind of plate to put behind the motor, inside the body. This can work, but I think this is difficult to do correctly and may require you to dismantle the plane. I think it could also reduce cooling air flow within the plane.

Others replaced the little oval metal piece "washer" that sits below the prop and holds the motor. They replaced it with a larger plate made of plywood or metal so that it covered the whole motor mount area. This would prevent a pull through and reduce the likelihood of the motor shifting left or right. This is easy and will provide reinforcement, but I don't think it is enough.


Here is what I did.

I drilled two holes on either side of the body, right behind the motor and put a nylon tie wrap there. This holds the body tight to the motor AND blocks the motor from shifting backward. I did this as part of my repair, but you can do it now, before a repair is needed.

The holes are 1/2" apart, centered on the motor. I used an 8" tie wrap, but a 4-6" wrap would probably be better as they are a little less bulky. You want the tie wrap to either sit against the motor or sit barely behind it so that, under stress, the wrap stops the motor from shifting which will either distort the motor mount area or pull it through all together.

Here are pictures of the damage I incurred and the repair.
http://www.shutterfly.com/osi.jsp?i=...21b33864ea2534

(A tip on viewing the photos. Select view pictures. It takes you to a slide show. In the upper right is a stop button. The photos will flip on their own if you don't stop them.)

The photos show a yellow tie wrap, but that was just for pictures. I cut this out and replaced it with an orange one that looks much better on the plane. I got the wraps from Home Depot, but Radio Shack has orange tie wraps as well.

After putting this tie wrap in place, there was no longer a need to put any kind of bracing plate by the prop area. This tie wrap really holds the motor solidly AND prevents it from moving forward.

Recommendation to all Firebird, Firebird XL, Fighterbird and Aerobird flyers and those with similar fuselage planes:

I love the Aerobird and think the whole "bird" series is fine. However a weak motor mount exists in all the planes. I would recommend this modification be done on ALL new "birds" BEFORE the motor mount is challenged and repairs have to be done. If the motor shifts far enough, it will hit the control board and wipe out all of the electronics. If it only shifts a little, the plane flies badly, commonly to the left or right and can't be trimmed properly.

You can do the drilling and insertion of the tie wrap without having to take the guts out of the plane. Just be careful to limit how far the drill bit goes inside the plane. There is enough room to do this, just be careful.

When you put the tie wrap in, make sure it slips UNDER the noise suppression components that are soldered between the motor terminals. You can see them in the photo. A 4-6" tie wrap is not as wide as the 8" wrap I used, so it will fit more easily with less displacement of the components, however I believe that it will be strong enough to get the job done.

Don't over tighten the tie wrap. Just make it snug, don't distort the body of the plane. If you are skilled and have some very long nose pliers, you can probably hide the square head of the tie wrap inside the plane so it looks better.

I plan to send a note to the manufacturer and advise that this should be done at the factory. Don't get me wrong, I like these planes, but they have a weak motor mount. This will take care of the problem before it becomes a problem.

I hope you find this post and the photos useful. Thanks to everyone for their advice and tips.

Don't wait, do this mod now on your Firebird, XL, Fighterbird or your Aerobird. Do it now, before you need it and you will have a much longer, happier relationship with your "bird".