Dynaflite Bird of Time ARF Sailplane

[Editor]

| spec
| @905191
| <b>Specifications</b>
|> <b>Wingspan:</b> |< 118 in (2972 mm)
|> <b>Wing Area:</b> |< 1050 sq. in. (67.73 dm 2)
|> <b>Length:</b> |< 49 in. (1245 mm)
|> <b>Flying Weight:</b> |< 60 oz (1700 g) listed; 58 oz as built
|> <b>Wing Loading:</b> |< 8.2 oz/sq. ft (25.0 g/dm2) listed; 7.95 oz/sq. ft as built
|> <b>Launch System:</b> |< Dynaflite Standard Hi-Start
|> <b>Radio:</b> |< Hitec Focus 3 radio (Hobbico brand) / 1 Hitec HS-55 servo (elevator),<br>1 Hobbico CS-61 standard servo (rudder)
|> <b>Price:</b> |< $149.99
|> <b>Available From:</b> |< <a href="http://www.towerhobbies.com">Tower Hobbies</a> / <a href="http://www.dynaflite.com">Dynaflite</a>

!Introduction

Reviewing the Dynaflite Bird of Time was a true time machine experience, taking me back
to my childhood where I had a deep appreciation for the graceful bird-like wings adorning
many of the Thermic kits that were available at the time. The Bird of time also took
me back to my earliest days of R/C flying, when I first &quot;earned my wings&quot; flying
pure sailplanes. To this day I still love soaring, although I've done nearly all of
my thermal chasing in recent years with electric-powered soaring machines. In a
sense, reviewing a pure sailplane like the new Dynaflite Bird of Time ARF is a little
strange to me, having devoted all my aviation energy to electric powered aircraft over the
past number of years. On the other hand, it feels very natural, so it's kind of like
coming back home. As a &quot;homecoming plane&quot;, I don't think I could have
asked for a better choice than the Dynaflite Bird of Time ARF. The Bird of Time
undoubtedly ranks as one of the most beautiful planes of all time. There's something
about the grace and elegance of this plane, with it's classic wing planform and flowing
lines, that tugs at my heart like no other. I've wanted a Bird of Time almost since
I began flying R/C, but a lack of building time kept one out of my hangar until now.

This new ARF does a magnificent job of removing the time dilemma with very fast,
very easy assembly while offering even better appearance, now that the fuselage is molded
in fiberglass. Rapid assembly and overflowing charm made the new Dynaflite Bird of
Time ARF a &quot;must have&quot; on my list.

!Kit Contents

Opening the Bird of Time box reveals some very pleasant surprises.

Dynaflite claims a 2-3 hour assembly time, and with the amount of prefabrication, they're
probably not far off the mark. Most holes are pre-drilled, plywood structure is
already installed, and nearly everything is arranged to go together quickly and
accurately.


@905192:Major components
@905193:Even extra nose weight is provided, in case your plane comes out tail heavy
@905194:vertical fin closeout, already installed and slotted for hinges. You'll also note the tail servo hole is pre-cut (circular area along the red line with the cover taped in place).

@905195
@905196
@905197:The very complete Bird of Time ARF has servo rails, antenna tube, rudder pushrod tube, and nose weight already installed in the fuselage. Wing mounting holes are pre-drilled and blind nuts are installed.

!Assembly

!!Wing

Since this is a poly-hedral wing (no ailerons), assembly is fairly simple. The
first step is gluing the components of the wing joiners (dihedral braces) together (there
are two sets, since the B.O.T. uses a 3-piece wing). Each joiner is composed to two
aluminum plates and two plywood plates, with the aluminum plates on the outside. I
originally tried using CA to hold the components together, but the aluminum didn't bond
well so I used epoxy instead (as recommended). When the instructions tell you that
one end is narrower than the other, they're referring to the height dimension (top to
bottom). I marked the ends of the pieces before I assembled them to prevent a
mix-up. After the joiners are completed, they're installed in the outer wing panels
(narrower side). The fit is tight, and the instructions advise that you may need to
trim the braces to fit. The plans call for gluing the joiners in the outer tip
panel, but mine fit so tightly in the center section that I left the joiners as part of
the center section.

After the joiners/dihedral braces are finished, an anti-rotation pin is epoxied into
each wing. Make sure you don't push the pins in too far.

@905198:Marking the narrow ends of the joiner/dihedral brace components with an &quot;N&quot; helped prevent a mix-up.
@905199:The dihedral brace and anti-rotation pin are shown installed in this photo (my dihedral braces became a permanent part of the center section a short time later).

Adding the wing hold-down dowels and screw reinforcing plate finished
the wing. The holes for the dowels are pre-drilled in the wing, requiring only an
X-Acto knife to cut away the covering over the holes. The ends of the dowels going
into the fuselage are rounded with a file before installation. I used Carpenter's
glue (Aliphatic Resin) instead of epoxy, with very good results (almost too good - it
worked so fast I almost couldn't get the dowels back out when I pushed them in too far).

Installation of the wing bolt reinforcing plate requires cutting away the covering
under the plate, and gluing the plate in place with the holes aligned. I used
aliphatic resin here also, holding the assembly together with clamps while it dried.
Dynaflite gave a nice touch by having the hold-down plate pre-covered. I found the
plate extended a little aft of the wing trailing edge when aligned with the bolt holes, so
I trimmed the plate back once the assembly was dry.

@905200:Dowel installation. The holes are pre-drilled, and just need the covering cut away over the top.
@905201:Clamping the bolt plate.

!!Rudder

Both the rudder and the vertical fin closeout are pre-built and pre-slotted.

Dynaflite provides a sheet of hinge material from which 3 hinges are cut, and these are
installed in the rudder with CA, then the rudder is joined to the fin and the hinges are
locked in with CA.

@905202: Dynaflite supplied more than ample hinge material!
@905203: Hinges are cut to size, then the corners are cut off to make them easier to install.

Rudder actuation comes from a long pushrod run through the pre-installed
pushrod sheath. One end of the rod is threaded for the clevis. The other end
is given a 90 degree bend for the servo arm (a nylon retainer holds the pushrod to the
servo arm).

@905204
@905205

Pre-installed servo trays make servo installation for the rudder very easy. It's hard to get used to full-size servos after flying electrics for so long, but the extra weight is useful for this sailplane. Control horn and nut plate are trimmed to match the angle of the rudder before they're installed (otherwise the rudder travel would be hindered by the plates).

!!Stabilizer

The Bird of Time is equipped with a full-flying stabilizer, meaning the whole
stabilizer moves for pitch control, as opposed to having a fixed stabilizer and moving the
rudder. This arrangement has certain aerodynamic advantages, but it can be tricky to
build. Thankfully, Dynaflite made it very easy. A rod in the middle of the
stabilizer serves as the rotation point. This rod, with flattened ends, slips into
holes in the stabilizers (going through the vertical fin) and is locked in place with
small set screws. All the internal hardware is already in place. A rod on the
front of the stabilizer acts as the pitch control rod, sliding up and down in a groove in
the vertical fin. The front rod also fits in holes in the stabilizers, but it also
goes through the clevis on the control horn in the middle of the fin. Dynaflite did
a nice job in supplying the control horn pre-bent and pre-assembled with the custom
clevis.

@905206:Components of the full-flying stabilizer. The stabilizer rotates around the rear rod, while the servo moves the front rod.
@905207:The fully assembled push rod and clevis is a very nice touch! The second photo shows the stabilizer in place.

Stabilizer servo installation is probably the most difficult part of the
kit, and it's fairly simple. The trickiest part is making certain it's positioned
properly in relation to the stabilizer front bar. You'll need to use a micro servo
in this installation; I opted for a Hitec HS-55. To set the servo up, I centered the
servo arm and installed the push rod. Once I placed the servo and push rod in their
approximate location, I pushed the front stabilizer rod through the clevis and centered it
in the slot. With the clevis properly located, I could now position the servo
properly. Next, I removed the servo, attached the double-sticky tape to the back
side, and reinstalled the servo and push rod (still keeping the pushrod clevis centered
with the rod). Now that the servo was &quot;stuck&quot; in place, I epoxied the two
blocks on either side of the servo to the fin (before I installed the servo, I roughed up
the fiberglass with sandpaper and cleaned it with alcohol). After the epoxy dried, I
drilled and installed the plywood strap over the servo. As a side note, you'll need
a 24 - 30 inch extension for the tail servo to reach the receiver.

@905208:The servo in place with the hardwood blocks epoxied on either side of the servo (helping to hold the servo in position).
@905209:This photo shows the plywood strap in place and the servo fully installed. The little section of antenna wire extending out the hole has been routed in the fin.

!!Tow Hook

Tow hook installation is about the only step on the Bird of Time requiring measuring
and drilling, but it's pretty easy. Mark a centerline along the bottom of the
fuselage between 14 and 17 inches from the nose, make a mark along that line 15 inches
back from the nose, then using the pre-drilled tow hook block, mark the remaining holes
and drill. The tow hook block needs to have the blind nuts inserted into the holes
in the block, then it's epoxied into fuselage over the drilled holes. The tow hook
can now be threaded into one of 4 positions.

@905210:The holes for the tow hook have to be marked and drilled.
@905211:The tow hook block, blind nuts, tow hook, and marked and drilled holes in the fuselage.
@905212:The tow hook block installed in the fuselage, and the tow hook installed on the bottom of the fuselage. The instructions failed to mention the washer and nut used to lock the tow hook in position, but it wasn't hard to figure out.

!!Radio Equipment

The servo installation has already been covered in the stabilizer and fin portions of
this review, but here's how I installed the receiver and battery pack. There's not
much unusual about my receiver installation - I simply used Velcro hook and loop material
to place it behind the rudder servo. My battery pack installation is a little
different, however. I started with a standard 600 mAh receiver pack in the nose, but
I found the CG to be a little aft of the recommended spot (current notes on the Dynaflite
web site now give a CG range that would have been acceptable, but the instructions just
said to place the CG 3 3/4 inches behind the leading edge), and I was uncertain about the
quality of this pack anyway. So, borrowing from my electric power experience, I
placed a 7-cell 1300 mAh NiMH flight pack in the nose and ran it through a Castle
Creations Pixie 14 speed control, using the BEC capability to provide the correct voltage
to the receiver. This pack fit the contours of the nose well (I used Velcro to hold
it in place), and I can fast charge it before flying. Plus, the capacity is double
my normal flight packs (just in case I catch a really great thermal!). This is a
somewhat more expensive way to do things, but if you happen to have unused flight packs
and speed controls laying around, it's not a bad way to make use of them.

@905213:My unusual receiver pack solution of a 7-cell 1300 mAh NiMH flight pack run through a Pixie 14 speed control (using the BEC function).
@905204:My Hobbico-brand Hitec Focus 3 receiver placed behind the rudder servo.

As a side note, I made good use of left over equipment with this
project. The transmitter, receiver, rudder servo, and battery pack all came from a
defunct Hobbico Aero Cruiser!

!Finished

!!Canopy, Decals, and Wing Bolts

Only minor items were left to complete the Bird of Time at this point. I found
the gelcoat on the fiberglass partially covered the wing bolt holes, requiring a little
cleanup with a hobby knife before the wing could be bolted on. I cut the canopy along
the molded lines and taped to the airframe with plastic packing tape. There's an
option to glue the canopy to a plywood frame and use a rubber band arrangement, but the
tape method works well for me. Last but not least, I applied the decal to the right
wing panel.

All Done!

Here's what Dynaflite's Bird of Time ARF looks like when complete. A
very beautiful ship!

@905191
@905214
@905215
@905216

This is a big plane! My son, who's over 6 ft, 1 inch tall is holding the Bird of time in the above photo. That nearly 10 feet of wingspan stretches out a long way!

!!High Start

Launching the Bird of Time is accomplished with a Dynaflite standard Hi Start.
100 ft of surgical rubber tubing attached to 400 ft. of string serves to place the Bird of
Time approximately 500 ft into the air, placing it well into good thermal hunting
territory. Dynaflite recommends the standard Hi Start, even though it's usually
recommended for gliders in the 100 inch range, due to the light weight of the Bird of
Time.

@905217:Dynaflite High Start

Dynaflite's Hi Start launch system comes conveniently set up on a reel. The spike can be inserted in the center of the reel as an axle, allowing easy wind up of the tubing and string. Assembly requires tying the parachute to the end of the line (after untying the ring on the end), and tying the ring to the end of the parachute.

!Flying

When the time came to flight test the Bird of Time, I decided to use a field next to a
local school, since it met the criteria of having the space to set up the Hi Start and
having an elevated area to conduct initial test glides. My test glides went well,
giving me the feedback I needed to trim out the Bird of Time before attempting the Hi
Start.

Launching with the Hi Start proved a little interesting. In my first attempt I
didn't have it stretched far enough, leaving the Bird of Time in a stalled attitude
without a lot of altitude when the Hi Start released. Thankfully, the Bird of Time
has gentle flying characteristics and I pulled out without any problems, even gliding
quite a distance in the process. After a few more experiments I found the way to
achieve good launches was to pull it back until I almost couldn't hold it, then give it a
good heave upward. It's still something of a leisurely launch, but it will get it up
to altitude. I'm using the standard Hi Start, and it seemed at the edge of its
capability (other, smaller gliders I've owned in the past rocketed up on the standard Hi
Start). The heavy duty version would probably be a better choice for this plane.


@905218: Ready to launch, and on its way up the Hi Start.

The Bird of Time launches easily, although I felt the standard Hi Start was close to its limit. I think the heavy duty Hi Start may be a better choice.

Once airborne, the Bird of Time is absolutely delightful to fly and
beautiful to watch. In a sense it reminds me of an ocean liner in the sky -slow and
graceful, and requiring a bit of room to bring around. Thermal catching is easy with
this ship (I caught a great thermal shortly after coming off the Hi Start on my first good
launch), and the large wing span makes it easy to see. I found that the Bird of Time
responds to the lightest of lift, giving good indication of thermal activity (just
crossing roads on landing would cause it to bob up). Landing is easy - I never felt
the need for spoilers. It just settles down gently. My only caveat is that as
a large floater, it takes some room to turn and to recover if you get it into an unusual
attitude. You just have to plan ahead a little more than you would with a smaller
sailplane, but it's probably easier to fly otherwise. At the end of the day, I was
all smiles. It's nice when a plane flies as well as it looks!

@905219
@905220

In the air the Bird of Time is every bit as graceful and elegant as its looks suggest. A sweet flyer, the Bird of Time seems to float forever, catching every little updraft along the way.

!Conclusion

I have nothing but good things to say about Dynaflite's Bird of Time ARF. A great
&quot;kit&quot;, it goes together fast and easy, with many thoughtful steps built in.

As a flier, the Bird of Time is delightful, floating around in the lightest of lift
with unparalleled grace and gentleness. Of course, the best aspect of the Bird of
Time is probably its classic, beautiful appearance that stands out in any crowd. A
definite winner!

[cold boy]

Was the recommendation of the standard high start because of the light weight, or because of the wing construction problem? Better to address the issue and see if Dynaflight has made the changes. There is no doubt the Bird of Time is a beautiful classic design.

[Ollie]

Steven,

I'd sure like to know how much tension, in pounds, this model can take on the tow line without folding the wings. What size fusible link in the tow line would you recommend to avoid wing damage during launch? To me that is more important than all the other measurements in the specification.

[nuevo]

In the article, there is no mention of winch launch failers reported over and over in various mailing lists and this very site. We all know Dynaflite has made statements regarding this issue, and has made changes to the production of the kit.

This review continues makes me skeptical of published reviews.

In defense of reveiwers, I understand the delicate balance they have to perform. Bad reviews, and the editor won't publish it, because he'll run off the advertisers.

The intentional mention of the launching system (not a winch) makes me wonder. Hmmm. :rolleyes:

[ISoar]

Originally posted by Ollie
Steven,

I'd sure like to know how much tension, in pounds, this model can take on the tow line without folding the wings. What size fusible link in the tow line would you recommend to avoid wing damage during launch? To me that is more important than all the other measurements in the specification. Typically use 3 to 5 times the weight of the model in tension.

It is pretty hard to fold the wings using a histart in my experience. Generally speaking. I know Dynaflite explicitly specifies a hi-start for launching the BoT ARF.

I've never used a fusible link on a histart or winch. Not needed IMHO.

[Steven Horney]

While I realize that quite a discussion has been going on regarding BOT wing failures under winch launches, the instructions specifically state that the BOT is to be launched by Hi Start only. Therefore I chose to review it that way. Besides, I don't have access to a winch. :-) My experience with the BOT is that it flies very well, and when launched as recommended there are no wing folding issues (as least as experienced by me). I don't know what the wings will handle - mine seemed reasonably strong (in my informal "bending" test), and I really didn't want to take them to destruction to find out.

To bring up winch launch failures in my review would have been slamming a product for use outside of its recommended envelope based on hearsay (since I haven't seen or experienced a wing failure), and that would be both unprofessional and unethical (in my opinion). Since the comments of others regarding the wings and winch launches are readily available on this web site, I felt that anyone interested wouldn't have to search far for the information. It seems to me that winching a plane designed only for Hi-Start launches is somewhat like powering an electric plane designed for Speed 400 motors with a brushless system - you're on your own at that point.

Steve

[Ollie]

Steven,
Another point of view is that the market for the Bird of Time would be larger if winch launching were allowed using a fusible link. The question of the proper sizing of a fusible link doesn't slam the product. Why limit the use of this very attractive product to histart launches? I think that is an unnecessarily narrow approach taken by an unnecessarily defensive supplier.

[Ray Lowinski]

Steve,

Just to comment on your EP analogy.

I wrote to Dynaflite specifically to ask about the use of the BOT wing in an electric application. Their answer was just about as expected - It wasn't designed for that and so they won't comment on it either. I really like the idea of the 3 pc. wing but I guess I'll have to strip one and do mods if I want to go EP with it.

Keep 'em hummin'

Ray

[sierra-gold]

Originally posted by Ray Lowinski
I wrote to Dynaflite specifically to ask about the use of the BOT wing in an electric application. Their answer was just about as expected - It wasn't designed for that and so they won't comment on it either. I really like the idea of the 3 pc. wing but I guess I'll have to strip one and do mods if I want to go EP with it.

Ray

Hi Ray,

I have just purchased a BOT from a reviewer from another model magazine. It hasn't arrived yet, but included a spare center section with spoilers installed and was offered at an attractive price. :D

I have plans to fly the BOT as a EP glider also. Two questions:

1. Have you decided on a motor system yet? If yes, what is it?

2. Have you actually researched whether the glass fuse has room to convert to EP?

I'm thinking I may buy a spare fuse(if there is room for EP gear) to convert to EP and save the original for pure glider. Or, if there isn't room, I'll build a wood fuse from the kit.

Sierra Gold

[nuevo]

Steven,

Thanks for the clarification. I disagree with the constraints by Dynaflite, as anyone who flies with a club most likely has no access to a hi-start.

That said, you tested it within the stated constraints. I understand your point of view as a reviewer.

I still believe you should have mentioned the failures, as responsible reporting to your readers. You know what the manufacturer said, but you also know that many many of the potential buyers of this kit are not likely to use it that way.

I have personally seen these failures, seen how the spars were built, and have heard from others that I trust. Since you don't know me, then I geuss you can call it heresay. What you call heresay, I call eye witness testimony.

Jon

[sierra-gold]

As stated in a message above, I intend to convert a BOT to EP.

I am operating on the theory that the stresses involved in "hard" high-start or winch launching are not present in an EP launch. This assumes EP launching is moderate and not "hot liner" style.

Is my operating theory correct?

My observations in converting a Hangar 9 Aspire glider to EP, is that the launch seems to be quite easy on that less than robust wing. (Hacker B20 L15, Maxon 4:1 GB, 11x6 prop, and 10 Kan 1050 pack. 39 oz. AUW and 60 degree climb out)

Sierra Gold

[nuevo]

Sierra Gold,

You are correct. The high stress part of flight is the launch.

The only other is if very high speed flight (i.e. dive) followed by a hard pull up on the elevator. That could happen on either type of plane.

As long as you don't fly like a hot-liner, or put the weight of 22 subC-cells in there, you should be fine.

[sierra-gold]

Yep, I'm an OLD glider-guider and only want to watch the BOT float in search of the elusive thermal. No speed runs are planned. :D

Loved this plane since I first saw it in the 70s. Left RC for about 11 years and just returned this year. Really like the "freedom" of EP launches and the ability to operate from smaller fields.

Sierra Gold

[nuevo]

Welcome back to the hunt for thermals and relaxing afternoons circling in the sky. It is a pretty bird.

[Miami Mike]

Originally posted by Steven Horney
While I realize that quite a discussion has been going on regarding BOT wing failures under winch launches, the instructions specifically state that the BOT is to be launched by Hi Start only.They may have altered the manual after they discovered the defective wings, but my manual says no such thing. In the Takeoff section, on page 17 near the top of the left column, it says in part, "You must be very careful about how steeply you allow the model to climb. If the climb is too shallow, you will not get the full height from the winch or high start..."

My manual has the code "DYFZ5000 for DYFA0500 V1.0" in the bottom right corner of the front page.

Edit - Here's another thought:

Both my manual and the box my Dynaflite ARF Bird of Time came in say "Unlimited Class 3-Meter ARF Sailplane". Can you explain how one might compete in Unlimited Class Sailplane events with a sailplane that can't be winched?

[Ollie]

For over two decades the original Bird of Time and the kit versions stood up very successfully to general usage by the community of sailplane fliers, including winch launching. If these designs were over winched, the wing rod bent and the plane survived without serious damage in most cases.

Earlier this year Dynaflite marketed an ARF Bird of Time and initially made false claims about its launch capabilities. When they discovered their mistake, they solved the situation by limiting the product application to high start launches and, perhaps, redesigning the wing structure rather than by designing and having manufactured a product with launch capabilities equal to the original Bird of Time and its kit variations.

So, the question remains as to the specific wing bending strength of this otherwise very attractive, quality product. If Dynaflite or any of the reviewers know they aren't telling so far.

This is regretable because a properly moderated or fusible link protected winch launch won't break the ARF's wing. Customers need to know the proper sizing of such a link. Dynaflite's sales and customer relations would improve if their restriction on winch launching could be at least partially lifted.

[Steven Horney]

I won't deny that the ability to handle winch launches would definitely broaden the market appeal of the BOT, and as a mechanical engineer with many years of stress analysis background I can certainly appreciate a strong, properly designed wing. As a reviewer, however, I feel I generally need to test a plane under the design constraints given to me by the provider. Since this is a pre-covered ARF, I can't tell how my particular wing was constructed (short of stripping off the covering), only whether or not the plane held up for me (which it did, showing no signs of wing problems).

As a personal comment, this plane is very much a floater - it flies very slowly, and very lightly. It isn't the type of plane I would expect to use for hard winch launches or F5B electric (although I would have no qualms about powering mine with a moderate e-power system). In short, I was honestly very happy with the plane in the realm in which I tested it.

Steve

[Miami Mike]

Originally posted by Steven Horney
In short, I was honestly very happy with the plane in the realm in which I tested it.You've reviewed a lot of model planes, haven't you Steve? Could you list a few planes that you didn't like, and tell us where we could read those reviews?

In fact, can you list even one?

[Steven Horney]

There have been a few planes that weren't thrilling - a Flyzone plane I reviewed with my daughter didn't work out too well, and another FlyZone review plane (the Aero Cruizer) I never published because of problems with the speed control that never were solved (it flew well, however). I loved the E-Streak, but the power system supplied was anemic. A foam FW-190 I reviewed a while bacik with my son was difficult to fly, no matter what we tried. I've also helped friends review a few planes that gave us problems. Overall, however, most of the planes I've reviewed have been very good. I might also add that "very good" applies to how a plane flies in relation to its design criteria. I'm not looking for unlimited aerobatics from a trainer or hands off flight from a 3D ship. Seldom is a plane "bad to the bone" - most can be salvaged with a few mods here or there, and that's what you'll generally see in my reviews (comments on a weak area and how I solved the problem). I would rather look for a solution than simply trash a plane. You also won't see many bad reviews from me because I usually choose to review planes that I'm confident are well made and fly well - and they usually are. There's nothing sinister going on here - we've been blessed with a lot of very good planes on the market these days.

Steve

[Ollie]

Steve,

Sinister is probably too strong a word.

A company that advertises that a wing will be strong enough for a particular application and then sells a weaker wing is probably either careless, incompetent or dishonest. Any one can make an honest mistake. Dynaflite's behavior leaves the determination of the cause of the mistake up in the air. As a result there is a cloud over their reputation. Your review has done nothing to dispel that cloud. What was called for, in my opinion, was a large dose of objective and specific truth about the BOT ARF's wing strength. That would be best provided by Dynaflite so that you could fairly confirm the specific facts as a reviewer. There is an old saying,"Let the buyer beware." Openness and truth are the antidotes to warriness. Lacking openness and truth puts the prudent buyer in a position of having to assume the worst.

[Steven Horney]

Hi Ollie,

I agree with what you're saying, but if Dynaflite says only to HI-Start launch the plane, are they being deceptive? If you're referring to calling the BOT open class, it seems to me that designation refers to the size, rather than to strength attributes. In reviewing the BOT I read through various threads on the topic, and tried to contact Hobbico to see if they had any kind of wing changes, etc. in the works. I didn't hear back from Hobbico, and I saw various opinions in the threads, so I had to review the plane based on my experience. Before I took the plane out I applied a fair amount of bending force to the wing to make certain it was sufficiently strong for flight. In flying the BOT I saw no evidence of wing flex or weakness. It was honest and open to say the plane flew well, even if it goes against what some are saying on the threads (I knew this review would be controversial).

What I think you (and others) are really asking for is a separate review of the strength of the BOT wing - how much load can it handle, and how is it constructed? I think that would be a great idea, but it would require the sacrifice of a wing or two. I wasn't ready to destroy mine in reviewing the kit (I don't usually make it a practice to take apart the ARF's that come my way).

Steve

[Ollie]

Steve,

I can't blame you for not doing a destructive test on the BOT ARF wing since i haven't been willing to buy one myself and test it to destruction.

Lacking destructive test data, I would be willing to accept the specific material and dimension information of the spar at the wing center from which I could calculate the maximum wing bending moment capability. From that I could infer the safe, maximum line tension. Although I asked for that information from the folks with broken wings, they were not forth coming with the data. So, they share some of the blame for the cloudy situation with Dynaflite in my opinion.

When you you applied "a fair amount of bending force to the wing to make sure it was sufficiently strong for flight" did you measure the bending moment applied?

[Steven Horney]

Ollie,

I was hoping to get a look at the construction of the wing from the holes in the end ribs of the center section when I wrote the article, but they didn't offer a view of the internals. As for my own "bending test", it was purely subjective, based on a "feel", but with some experience to back it up. As a side note, it's possible I have a wing that is properly constructed (I seem to have read where some folks reported spar grain dreiction going the wrong way).

Here's what I'll do to help clear this up: If no one is forthcoming with information on the construction of the wing, let me know and I'll cut away some of the covering on my wing. That should allow us to find out how the wing is constructed. You and I can both run some numbers to get an idea what the wing will handle. I'll ask Jim to publish an addendum to the article with commencts on wing strength and flight restrictions.

Steve

[Ollie]

Steve,

I like your plan.

[Terror Dactyl]

One of the folks at our field has a BoT arf and had only high started it five times and no winch launches at all. He noticed that the tip sockets were now loose on the wing bar so he (at a building session for a club plane) cut into the covering at the box areas and saw that the shear web was split as it was installed with the grain in the wrong direction.

This has only been flown in the maner of the lessor capability and still failed profoundly.

There is another pilot at the field that has gotten a replacement wing since the supposed upgrade and to ease his own mind he also checked through the covering and the shear webbing is also in the worng direction.

I have one that has not flown as yet and I will be cutting into the wing to wrap the box with carbon and install spoilers.

There really is no excuse for the problem in the first place, but I really think that the coverup/lying as to the initial response and then the lie about the fix is just about par with anything that a Tower /Hobbico arm would pull.

I have vented and will go back to building befor getting something from Tower.

Thats me story and I am sticking to it!!!!!!!

[Ollie]

Terror Dactyl,

Would you be so kind as to partially remove the covering at the center of the wing and measure the width and thickness of the top and bottom spar caps. Also, the height, thickness and grain direction of the shear webbing. If you can, please also tell us the specis of wood used in the spar caps and in the shear webs. if there is any other reinforcement of the wing spar at the center, please describe it in quantitative terms. The reason I am asking for this data is an attempt to calculate the safe launching line tension for the BOT ARF. In my opinion, the situation calls for some numbers to guide potential buyers of the product and to add some hard data on actual wing design strength to Steve's product review. Your cooperation will be much appreciated by me and probably many others.

Anyone else who is able to contribute data on the BOT ARF wing spar at the center should contribute that data to the group. Some of the measurement will probably be easier to get from a broken wing where the spar crossections are fully exposed.

[bwaltz]

I am the other person that got the 2nd defective wing. Tower refunded my $. This is a good flier, but won't last long due to the poor construction. Bad move.

[Ollie]

bwaltz,

What happened to the broken wing? Is there any way we can get some measurements of the spar structure?

[bwaltz]

Originally posted by Ollie
bwaltz,

What happened to the broken wing? Is there any way we can get some measurements of the spar structure?

Hi Ollie,

I had to send it back in order to get the refund. I guess they wanted to get rid of the evidence.

Brett

[Joe Minton]

Ollie

I have been flying a BOT ARF off an NES standard high start for about 30 flights now. I have been using 14 -- 16# of release tension (per my fish scale). The plane weights about 59 oz.. No problems. Only a small amount of flex as she climbs.
If the wind subsides this Sunday, I'll fly her again and, when I get home, I'll strip the wing covering and fulfill your request for spar-related information. If the wind does not subside, I'll strip the wing in the morning instead of the afternoon.
BTW: 20# on the tow hook @ half-span, across two chairs, only scared yrs trly. The BOT wing didn't seem to mind all that much even though its loaded appearance brought back memories of my Hobie Hawk.

Joe

[Ollie]

Joe,
Many thanks. I'm looking forward to what your investigation of the spar structure reveals.

[gordonbw]

So, what do people think about the advisability of electrifying this plane, given the apparent spar strength problems? I've wanted one for years...

[Ollie]

The suitability of electrifying the BOT ARF depends on the maner in which it will be flown. If the airspeed is limited to air speeds not much above thermalling and climbing speeds it should be perfectly safe. However, if the air speed is allowed to build up too much and the plane hits a gust or is pulled out too sharply the wings will fail. After the wing strength is quantified, then a red line air speed can be estimated by calculation and you can determine if that speed limitation is acceptable. The downside is that Dynaflite has not shown any willingness to support any launch method besides a histart launch.

There are many potential benefits to knowing the specific wing strength.

[Garvey]

An eastern european company makes an electric version called the Bird 3000, unfortunately I don't know who distributes this model.

http://www.pbmodel.cz/bird3000.html

[Garvey]

Oh, and the website has a video which shows the model doing a few loops so it's wing should be fairly strong.

[kjkish]

I think you can find the Bird 3000 on the following website:

www.espritmodel.com

[solo6796]

I have the Bird 3000 and set it up for winch launch, instead of EP. I was attracted to the flat wing and airlerons.

Anyway, the spar on this model is simply lite ply and capped only with the very thin fiberglass D tube for the leading edge. The wings would bend noticibly under a moderate launch. I finally broke a wing while launching on a windy day.

It was a great looking model that I specked out many times, so I got another and added 1/4" CF spar caps and 1/4" shear webs sistered to the lite ply.

There is NO bending at launch now, and the ship flies great.

I have other ARF's and all required some strengthening in some areas.

If you buy an ARF, look for problem areas and beef up weak spots during the assembly stage. These units are assembly line work and will never have the attention to detail given scratch built or upscale ($500.00 and up) composites and better RTF models.

They save some time in getting to fly, but anything expected to go up on a winch should be thoroughly inspected and modified to handle the stress.

This Dynaflite BOT joiner and spar is simply not strong enough to handle a winch, the same as my Bird 3000. You can get several easy launches, but each will further weaken the assembly until it finally breaks, as in my case.

Modify it for the winch, or follow the manufacturer's launching advice without modifications. At least the process will give new modelers some building experience!

AJ

[equest]

Folks,

Follow this great link that explains on how to install spoilers on the ARF version of the Dynaflite BOT. http://www.dozone.net/public/rcsoaring/ARTICLES/Spoiling%20%20the%20DynaFlight%20Bird%20of%20Time. htm

Equest

[aeajr]

While people are opening up covering, perhaps some photos can be shot. If the grain is going the wrong way, and I personally don't know which way it should be going, I think publishing a few photos should put that to rest.

Let me provide the following. I don't know if it is useful in the discussion.

I use a NEsail standard hi-start to launch my GP Spirit 2M Select RTF. That is 1/2" rubber with 3/32 wall. It is really designed for much larger planes. The wings are two piece, joined with the standard joiner provided with the Spirit Select RTF. I tape them together at the start of each day's flying with 2" clear packing tape.

I measured the pull on the line with the NE Sail Hi-start I use. The most I could develop without crushing the body of the plane to hold on to it, was about 12 pounds, for whatever value that has to this discussion.

The Spirit has never complained even a little bit. The Spirit has been winch launched many times with a tap tap pedal.

I have flown it off of a dynaflite HD hi-start as well. That is 5/16 rubber with 1/16 wall. I never measured the pull but I don't think it ever exceeded 8 pounds no matter how far I pulled it, and may have been less. If that is the hi-start that the BOT is being targeted to, it provides a pretty soft gradual launch.

Again, I don't know if any of this info is relevent as this is a 2 meter Spirit Select RTF not a 3 meter BOT RTF.

[michaeljt]

Can anyone tell me if they have experienced wing failure after October, 2003 when Dynaflight post the below Tech Note?

http://www.dynaflite.com/techsupport/dyfa0500tech.html

[Terror Dactyl]

The purpose, IMHO, for the webbing is to connect the upper and lower spars with something to significantly improve the strenght of this assy.

This will happen when the grain of the web piece is orineted vertically.

The BoT web is horizontal and does not add a significant support as the grain is separated easily in this condition.

Take care Jim

[launch&grin]

I did not know about the wing controversy (or this discussion group) when I ordered a BOT from Tower in June '04. I originally came here to ask about problems launching my BOT with an approx. 10 year old Dynaflite HD hi-start (DYFP 8302). I used to use it for my only other sailplane, a Bob Martin Pussycat which weighed about 1/4 as much as the BOT. The 3 BOT launches were very weak and slow and it popped off about 30 feet off the ground. I wanted to ask if high-starts get too weak to work after 10 years (stored in a dark closet in an air conditioned house). How much tension should I use? After reading about the wing, I took some covering off the middle wing section and discovered that the shear webbing is horizontal (which is wrong) and the spar caps look like medium hard 1/4" X 1/16" balsa. It may be some Chinese species that I am not familiar with. They are definitely not spruce as were the spar caps in the 6 kit planes I have built. I have never heard of a built up wing without spruce spar caps. There is one layer of 3/4" wide fiberglass or nylon cloth wrapped around inboard end of the joiner box. I don't see any point in adding vertical shear webs if the spar caps are just going to fail. I have thought about adding spruce spar caps behind the existing spar and filling in vertical grain balsa shear webs, but that would be as much work as starting from scratch. Adding CF to the bottom existing spar cap would help keep that spar from failing in tension, but the top spar will be in compression and CF won't help much there. It looks like Dynaflite has created a real lemon. I wish I had come to this discussion group before I ordered the BOT. Thinking about Chinese wood species made me think about bamboo. The spars are definitely not bamboo, but would bamboo be a good choice for spar caps? Has anybody ever tried that?

[rdawson]

Hello,
I built the Bird of Time and have made a power pod for it. See pics. It has a OS Max 10 on it with a Hayes 2oz fuel tank and a servo for throttle control. The whole unit weighs
13oz. The glider weighs in at 63 oz plus 13 oz for the pod for a total of 76oz. The weight make the wing loading 10.30 oz per sq ft. The pod is held on with rubber bands. Next week you can go to my youtube page and see the build and flight review including building the power pod. Search rdawson55 at you tube aftar say 7-17-2009.
Here is the link for the webshot pics. http://rides.webshots.com/album/573406717BReylJ
Thanks, Roy

[rdawson]

Hello,
Heres my ARF Bird of Time Youtube Build and flight review using a home made OS max Power pod. Lot of fun and easy to build
http://www.youtube.com/watch?v=tstI5l9_avo
Pics and a measured drawing of the power pod at my website
http://rides.webshots.com/album/573406717BReylJ

[rdawson]

Bird of Time inflight video and flight review on youtube. See flying from a bird's eye view from the cockpit.
http://www.youtube.com/watch?v=3YitwV4xiWQ

[Bad scientist]

I am about to start building the BOT kit version, and I`m currently in the phase where I`m staring at the plans trying to understand every aspect of the build before i start. If the arf version is built the same way, you will not be able to see the direction of the webbing, because it consists of hard balsa blocks that go directly under the spar with the grain i the right direction. These blocks are hidden behind a ply capping with the grains going horizontal. So what you are seeing is not the webbing, but the enclosure.
It`s the first time I`ve seen this type of construction, but it seems to make sense.