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Bird of Time

Old 04-19-2010, 10:17 PM
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Default Bird of Time

Is it just me or is the Bird of Time a beast to land? I am a 30 year RC pilot "on and off" and I just can't seem to tame this Bird! Flights are long and graceful but I winch every time it's time to bring it in. It seems like it drops like a rock when it's about 6 feet off the ground. I have converted it to electric so I can usually pull out of it ever so clumsily! I had to add about 12 ounces of lead to the nose to get the CG right. Is this too much? Help!
Old 04-19-2010, 10:23 PM
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Default RE: Bird of Time

wow, 12 ounce of lead in nose? something seems wrong there. after converting to electric I would think it would be nose heavy?
Old 04-19-2010, 10:39 PM
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Default RE: Bird of Time

Why don't u try moving the battery forward and lose the extra weight for starters.
Old 04-19-2010, 10:43 PM
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Default RE: Bird of Time

I haven't had mine out lately, but if I recall my old kit built one.. I removed full sized servos up front, put smaller ones under wing ...then refitted it for batteries up front...

I think I have two 3 cell 1250 lipos in parallel (think thats the term) , or I can use a 3 cell 2400 ..both balance almost the same, I think I taped a penny on the back bottom of the fuse to balance.
Old 04-19-2010, 11:03 PM
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Default RE: Bird of Time

Well if you know anytihing about the Bird of Time it allready comes with a big chunk of lead in the nose which you pound out to get the 25 size E-motor in. I have a 3-cell 2200 ma battery shoved as far forward as I can get it. But still had to add lead to the nose. Don't think I would want to fly this monster tailheavy, would you?

Old 04-19-2010, 11:41 PM
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Default RE: Bird of Time

Mine came as a box of wood, So I didn't know you had to knock lead out first ...

It's hard to believe the arfs are that tail heavy?
Old 04-20-2010, 09:10 AM
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Default RE: Bird of Time

If the plane drops like a lead sled when you get close to the ground, it's likely that it's stalling. Don't try to slow a glider down too much...you don't flare the landing. You just keep it level and let it slide in.

The Bird of Time, like any other glider, needs weight in the nose because there isn't an engine, and the radio system doesn't usually add much weight. If you have an electric conversion, the electric motor will add some weight, but usually not enough, so you'll need to add weight. 12 ounces would be a TON of weight to add. If you can, try moving batteries forward to help eliminate weight in the nose.

Please note that the Bird of Time flies at a higher speed than many other gliders. You can tell this because when you increase the speed, the model will suddenly flatten its glide. It's very noticeable in the air. Mine would look like it suddenly "hooked up" when it hit the proper speed. Flying the 'Birds too slowly is something many people wind up doing.

To see if the balance is correct, set the model up for a normal glide. Get it trimmed so that the elevator is 'hands off'. Now put the model into a 45-degree downline. Hold it there to stabilize in speed and then gently release the stick. If the model noses up fairly rapidly, the model is nose-heavy. If it tucks nose-down, it's tail-heavy. If it stays the same or noses-up slowly, your balance is OK.
Old 04-20-2010, 11:22 AM
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Default RE: Bird of Time

So when is the next bacth of ARFs comming in? My buddy wants one......to electrify.
Old 04-20-2010, 11:28 AM
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Default RE: Bird of Time

I know someone at my feild who built up the arf and electrified it. He had everything as far forward as he could cram it and it was still tail heavy. He ended up having to pour the spinner full of lead to make it balance.
Old 04-20-2010, 01:57 PM
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Default RE: Bird of Time

Sounds like the ARF versions are built very heavy in the tail. My own BoT glider version is only using the 4xAA pack and about 5 more oz of lead to balance.

Opwan, since it appears that your ARF electric Bird is on the heavy side I'd also suggest that you need to watch for the stall speed on landing. But as a long timer you already know that. But what may be biting you in the heinie on this is the ground shear effect when flying in a breeze. As your model descends through the last 3 to 6 feet the wind velocity falls off a lot. And on higher wind days this effect is even stronger. If you're flying at just a little over the "mushy" prestall speed while higher as the model descends into the ground shear layer the model has to speed up to maintain the right airspeed. Light models can manage to do this with a little more ease than heavier ones. And a BoT with a motor and 12 oz of lead up front qulifies as a "heavier one" in my books.

The trick is to hold a little more speed on approach on the windy days in order to deal with this ground shear.

Also if your model seems to get into a mushy mode with a steep descent when slowed down that you don't think should be occuring you may want to try fitting the wing with turbulator strips as an experiment. My own BoT gained a lot at the low speed end from this mod. I used two layers of 1/8 wide located at 1.5 inches back from the leading edge. It helped the model to "hang" better up to the stall point. Before it would go into a high drag "mushy" descent well before the stall.
Old 04-20-2010, 07:27 PM
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Default RE: Bird of Time

Sounds like the best advice I've heard but what are tubulator strips? This is only my 2nd glider and I'm still learning. Thanks for all the help guys!
Old 04-20-2010, 09:18 PM
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Default RE: Bird of Time

Turbulators come in a wide number of varieties. What they do is trip the laminar flow early on the wing to form a transition to a thin turbulent layer. What they are is a surface roughness or low obstruction that sticks up into the airflow close to the wing. In this case it is a raised strip that is 1/8 wide by two layers of tape thick.

This thin turbulent layer that is created by the turbulator is far more sticky than the laminar flow so when you slow down there's less likelyhood of the flow separating to form a turbulent bubble. Such bubbles create a lot of drag and spoil the wing's lift. They create the mushy sinking sort of flight that happens when you're still flying faster than a stall but the model suddenly just seems to sink.

Mind you it only works if your model is suffereing from this separation bubble issue when flying slowly. But your symptoms sure sound like it to me. And if two layers do not make things better try adding a third layer before giving up on the turbulator for your application.
Old 04-21-2010, 10:31 PM
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Default RE: Bird of Time

Where do you get these strips? I've done a ton of searches with no luck. Yes, I think the ARF version is a little on the tail heavy side, as far as saving weight in the back of the model, it's fiberglass! I've even moved the elevator servo under the wing instead of putting it in the tail under the elevator like the directions say and run it off of a nylon "very light" bellcrank!
Old 04-22-2010, 08:39 AM
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Default RE: Bird of Time

Like I said before I dont have one nor do I profess to know a whole lot about it but this is a wild suggestion.

Try moving the main wing back slightly...... not sure how easily this can be done nor what drastic effect this could have to its flying characterisitics. I would try moving it a slight nudge at a time.
Old 04-22-2010, 10:05 PM
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Default RE: Bird of Time

I think I'm gonna add a LITTLE more weight and try the tubulator strips! Heck this things got enough wing to support a baby elephant. Some planes just need some weight to fly better. I just built a 15 electric size PT-17 by E-Flite, thing flew like **** till I put about 8 ounces in the nose, now it is smooth as butter!
Old 05-03-2010, 05:20 PM
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Default RE: Bird of Time

The best thing that you can do for that BOT is take that servo out of the tail. Install a bell crank in it's place and use mini servos in it, not full size. Then put your battery as far forward as you can and see how close that comes to the CG. If you need to add a little weight, it shouldn't take very much . Not with a motor and battery up front. Spoilers are great for that thing. The worst I have found with the BOT is it doesn't want to land. It just keeps floating by until I put spoilers on mine. Now I can put it just about anywhere.

Ed
Old 05-05-2010, 12:58 AM
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Default RE: Bird of Time

Hello:

I would like to electrify my ARF version.

What power system (motor, ESC & battery) is recomended?

I would like to go with a brushless outrunner.

Any suggestions would be helpful.

Thank you
Old 05-05-2010, 09:59 AM
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Default RE: Bird of Time


ORIGINAL: ADANAC18 - I would like to electrify my ARF version. What power system (motor, ESC & battery) is recomended?
I used:

Axi 2820-14 swinging an AeroNaut 13x6.5 prop and a 70 amp ESC with two 3s1p 2200 25c packs in parallel.

A 40 amp ESC would work, but I generally go the safe route.
The two lipo packs are used for balancing.

I recommend you use a bellcrank in the tail and move the servo as far farward as possible. A few grams saved in the tail saves a bunch in the nose.

I balanced dead on at assembly and have repeatedly moved the CG toward the rear with each flight. But, that is my prefrence and it may not be yours.

Phil
Old 05-06-2010, 07:49 AM
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Default RE: Bird of Time

Guys, I just found this thread and I can't thank all y'all enough for all the "heads-up's". My own "kit-built" BoT is about 95% done (finish coats go on the fuse today) and I'm planning on 1st flight this weekend. Haven't balanced it yet but I sanded the begeeeebers out of the rear of the fuse when building so I'm hoping it's somewhere in the neighborhood anyway.

Actually, I sanded so much on the fuse rear that I sanded right through one of the glue joints and had to re-establish it before continuing with MORE sanding.

Right now I fly my Spirit-100 a lot and it has a BUNCH of lead in the nose to fly right - have a pocketful of "bullet" weights ready in case the BoT needs the same.

Wish me luck. I've wanted one of these birds for more than 40 years, I'm about to have one FLYING!!

Dave

(pics show the wings when first finished and the spot where I over-sanded the fuse)
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Old 05-06-2010, 08:10 AM
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Default RE: Bird of Time


ORIGINAL: skylark-flier - I've wanted one of these birds for more than 40 years - Dave
That is a rather long wait. Best of luck to you. Nice pics. I just painted the botton of my outer panels black. Fisrt flight with painted panels in about an hour.
Phil
Old 05-06-2010, 09:24 AM
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Default RE: Bird of Time


ORIGINAL: opwan

Where do you get these strips? I've done a ton of searches with no luck. Yes, I think the ARF version is a little on the tail heavy side, as far as saving weight in the back of the model, it's fiberglass! I've even moved the elevator servo under the wing instead of putting it in the tail under the elevator like the directions say and run it off of a nylon ''very light'' bellcrank!

Your question got overlooked?

The strips can be made from simple striping tape. Run a stripe spanwise and then add another layer right on top of the 1st. The double thickness is usually pretty good. With a BOT, you'd probably want to try it first at about the profile's high point. If you don't like how that flies, pull it off and try a different place. I once tried a turbulator strip around the 25% line on the right and about 20% on the left wing panel. Wanted to see if the results would differ, which should have proven at least one was working. Gliders are kewl 'cause you can try all manner of things with little probability of catastrophy.
Old 05-06-2010, 07:44 PM
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Default RE: Bird of Time


I once tried a turbulator strip around the 25% line on the right and about 20% on the left wing panel. Wanted to see if the results would differ, which should have proven at least one was working.

What were the results ??

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