Valley Engineering's new ultralight

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wakataka

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Notice how the parachute bridle is only attached to the upper member of the spar? So in the event of a deployment, all the welds would be in tension with several g's applied in one place spot on only one of the three tubes that make up the spar. I can't imagine that turning out very well. I hope maybe there's another section of the bridle not shown that extends down and connects the bottom of the fuselage or some more substantial piece of the air frame, but it sure doesn't look that way. Yikes.
 

mcrae0104

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Notice how the parachute bridle is only attached to the upper member of the spar? So in the event of a deployment, all the welds would be in tension with several g's applied in one place spot on only one of the three tubes that make up the spar. I can't imagine that turning out very well. I hope maybe there's another section of the bridle not shown that extends down and connects the bottom of the fuselage or some more substantial piece of the air frame, but it sure doesn't look that way. Yikes.
It's very hard to make such a judgment without analyzing the structure.
 

PTAirco

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It's not just the welds that bother me; it's the whole execution of the design. But yes, the welds on the one I saw looked awful to me; the diagonals joining the top spar tube appear have had their ends squashed, bent over to fit the tube and welded on. Has anyone ever seen a welded steel tube fuselage put together in such a manner? But I guess it's appropriate for a wing spar? The lower, fore and aft, diagonals don't intersect at the same node. There are no aircraft flying that use welded 6061 tubes in their wing spars and maybe, just maybe, there is a good reason for that. This is a cantilever wing; the spar tapers somewhat in thickness, but do the tube sizes change? It doesn't seem they do. It seems to me it is way over strength at the outer portion. I willing to be that despite his assertion that Gene Smith holds a degree in mechanical engineering, no real stress analysis has ever been done on this aircraft beyond perhaps hanging on the wing tips and saying: "that looks about right" .

The wings apparently are painted with tractor enamel. Because it is "superior", I assume, to proper aircraft coatings. Nothing wrong with that, I hasten to add - paint peeling off your fabric in flight probably won't kill you.

It also comes with standard a "bank Indicator" . I don't think they mean an artificial horizon or gyro driven instrument. If you've ever had a flying lesson you may recognize it as a ball in a curved tube. Never did work as a bank indicator for me though.
 

steveair2

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The Backyard Flyer is a very crude design in almost every aspect. I would like to know how many have been built and are flying. I wonder where the weakest link in the design is? One day we will know. I've seen them at Oshkosh every year for the last eight years. That means nothing I know. I'm waiting to find out which weak link breaks first.
Experimenting with such foolishness should be illegal. Where is your ultralight design?
 

wakataka

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It's very hard to make such a judgment without analyzing the structure.
Exactly. Because detailed structural analysis rarely (maybe never?) done on ultralights, I tend to pay a lot of attention to what "looks right" and this just doesn't look right to me. If the top member of the spar is able to take the concentrated shock loads of a parachute deployment with a comfortable margin of safety, then wouldn't the spar have to be way over-designed and therefore overweight for normal flight loads?

On both my ultralights, the parachute bridle is looped through the fuselage and attached to at least two structural members in the the lower part of the fuselage, near where the landing gear and the strut loads tie in. This is obviously one of the strongest parts of the air frame for the positive-G shock loads associated with a parachute deployment. Even if the wing departs the air frame, the parachute would likely still be attached to the same part of the wreckage as my sorry self.

Hopefully very few of us will ever experience a parachute deployment, so this is not a deal killer for design. I like some of the features of this airplane and I give them kudos for apparently making part 103 weight and reasonable performance with a 4 stroke engine. Few have been able to pull that off. Maybe they've done some drop or deployment tests to prove that this parachute setup works. I'd sure ask about that if I was thinking of buying this one. Or else I'd just change that bridle attachment set up after I bought it.
 

rtfm

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Bloody hell guys - give it a break. This better-engineer-than-thou attitude isn't nice. Enough already. Pretty welds don't mean strong welds. If you don't like the design, fine - but slagging off the designer/builder on this forum is not gentlemanly. If you have something negative to say about the design/build - give them a call. Write them an email. Tell THEM - not the people on this forum. I really feel uncomfortable with this thread. It isn't edifying at all.

Duncan
 

Dana

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Experimenting with such foolishness should be illegal.
Not at all. That's the whole point of 103, after all: You're free to risk yourself, but not a passenger.

I agree that those welds don't look pretty, but as Duncan says pretty welds aren't strong welds. Consider what the structure is doing: The small diagonal tubes are the spar's shear web. As such, the loads are relatively low. The primary failure mode in almost any tube structure is column buckling, which requires integrity at the midpoint of the member... where those tubes aren't flattened. For the large spar tubes, again buckling is the failure mode, which depends on elastic modulus, not ultimate strength, so the loss of strength in the weld's heat affected zone is not a factor. Looking at the big gnarly weld at the lower left corner, it looks like that's a local reinforcement sleeve for where the BRS bridle attaches; I don't see it anywhere else. I don't know what's under the webbing where it wraps around the upper spar tube, but it looks like that will carry the BRS loads to the lower spar tube as well. I also see two vertical members that the bridle wraps around, running down to the vicinity of a large bolt that may be the fuselage attachment.

I would worry more about fatigue cracks in the welds, so periodic inspection would be in order... but there are a lot of them, so there may be enough redundancy, just like the Fisher geodetic wood structure, that a failure of one may not mean catastrophic failure.

Is it crude? Yes. A lot of ultralights are crude; they have to be to be cheap. But "crude" doesn't necessarily mean "dangerous", just as pretty doesn't automatically mean safe. I don't know what level of structural analysis or testing has been done on this design, so I won't judge whether it's adequate, but I haven't heard of them dropping out of the skies, either.

Dana
 

steveair2

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Yes Dana, those are my sentiments exactly. My remark about legality was sarcastic. I've always liked this design in ALL of it's crudeness.
They may be pushing the boundaries on design safety, but they have a eight year proven track record and is proving a good test bed for experimental ideas.
That is part of what makes this sport great.
 

steveair2

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Steveair2,
Sorry, mate - I just don't get it. That has to be one of the most damned ugly little planes on the planet - why would anyone build it? It looks like a joke. There must be DOZENS of nicer machines...

Just my 2c

Duncan
REALLY!?
 

rtfm

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Hi,
Guilty as charged. I seemed to have led the way in slagging off the plane - but because I thought it was ugly. It offended my aesthetic sensibilities. If I was somehow responsible for the systematic condemnation of its engineering and build quality - I'm sorry. So I guess, yes, a change of heart.

Duncan
 

ScaleBirdsScott

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I don't even think it's all that ugly. I'm not a fan of the welded aluminum myself but I'll take that for an ultralight type setup it probably really is fine. I just wonder if the effort pays off.
 

Midniteoyl

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The design seems fine, the looks seems fine.. Even the construction seems fine except for those welds. I just cant seem to get past the welds.
 

mcrae0104

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I tend to pay a lot of attention to what "looks right" and this just doesn't look right to me.
I agree--common sense and the judgment that arises from experience with such things does count for something. But what looks right is not always what is right. I see no reason to trash the designer on the basis of what we've seen. I might not design the plane the same way, but it seems to be working.

If the top member of the spar is able to take the concentrated shock loads of a parachute deployment with a comfortable margin of safety, then wouldn't the spar have to be way over-designed and therefore overweight for normal flight loads?
No. It depends where the parachute point load is located (wing station). A spar that is designed for, say, 3g (just to pick a number) distributed across the wingspan could potentially carry many times 3g as a point load, particularly if that load is very close to the wing attach points (which is unknown based on the photographs posted, but if the designer had any common sense it's probably near the centerline of the aircraft).
 

lake_harley

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I saw a Backyard flyer in person at Culver Props a few years ago. I can't say I had a cold shiver go down my spine from fear when I saw the welding. In fact, I was pretty impressed with the welding, considering it's really thin wall tubing. Just welding aluminum that thin takes some talent. Sometime things look worse in photos than they really look in person.

Lynn
 

cheapracer

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Just welding aluminum that thin takes some talent. Sometime things look worse in photos than they really look in person.

Lynn
The spar design looks great. Flattened tube ends is quite common in engineering (maybe not so common in aircraft). The bracing tubes do not have to be in the same plane as long as they are kept within a diameter.

The welding looks like someone has gone in too cold for fear of melting the thin tube. None of us can prove from the pictures that it's poor welding strengthwise, but it's not really what most manufacturers would want or shoul present in their brochures.

I think it looks good relative to what it is, and RTFM, FWIW, I happen to like the look of all the Affordaplane/Airbike styles regardless if I disagree with the basic engineering.
 

samyguy

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Hi All I have seen the backyard flyer in person.
THAT link to a pic of their wing is from 2008, when they were MIG welding, their air frames.
IF you would check on their new production you would see they are TIG WELDING
their air frames NOW.
FOR THE LAST FIVE YEARS!!!
Sure their first ones had some not so good spots, but they have improved, where needed.
It seems to be a nice flying ultralight, ARE YOU producing a better one?? For any price.
 

Midniteoyl

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Hi All I have seen the backyard flyer in person.
THAT link to a pic of their wing is from 2008, when they were MIG welding, their air frames.
IF you would check on their new production you would see they are TIG WELDING
their air frames NOW.
FOR THE LAST FIVE YEARS!!!
Sure their first ones had some not so good spots, but they have improved, where needed.
It seems to be a nice flying ultralight, ARE YOU producing a better one?? For any price.
Careful there. Several here have built many.

Beside, the internet way of saying 'you build one better then' as a defense is, well, pure hogwash. If they are better at welding now, good for them. I guess the next time I see one I will have to go and check for myself. Thanks for the info.
 
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