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Old Dec 14, 2003, 12:33 AM
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Punta Gorda, FL
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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.
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Old Dec 15, 2003, 07:20 AM
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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
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Old Dec 15, 2003, 04:59 PM
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Quote:
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?
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Old Dec 15, 2003, 05:17 PM
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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
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Old Dec 15, 2003, 08:38 PM
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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.
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Old Dec 16, 2003, 07:36 AM
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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
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Old Dec 16, 2003, 09:14 AM
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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?
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Old Dec 16, 2003, 09:23 AM
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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
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Old Dec 16, 2003, 02:04 PM
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Steve,

I like your plan.
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Old Dec 16, 2003, 02:48 PM
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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!!!!!!!
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Old Dec 16, 2003, 05:00 PM
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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.
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Old Dec 16, 2003, 06:18 PM
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Pearland, Texas
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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.
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Old Dec 16, 2003, 08:04 PM
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bwaltz,

What happened to the broken wing? Is there any way we can get some measurements of the spar structure?
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Old Dec 16, 2003, 08:14 PM
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Pearland, Texas
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Quote:
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
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Old Dec 16, 2003, 09:43 PM
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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
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