Another oddity in a Belite

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PTAirco

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Take a look at this video of a Belite Ultracub under construction:


See 8:19 and 8:59.


Note how the ends of the first and last drag struts are not attached to the spar, but to the middle of another compression strut. What was the designer thinking here?? I don't think it was to make room for a tank (my first thought), but even if it was - that's just horrible. Why do people throw out all basic principles of engineering when it comes to ultralights? "Oh, it's just an ultralight..."
 
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mcrae0104

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I doubt the designer designed it that way--the builder seems to be highlighting changes he made, such as the addition of the fifth tube.
 

Airworthy

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He says the number of sail antisail changed. But the previous design had the same number i think just different length. Sail/anti sail was previously mounted midway to the wingtip/root via socket made in the wood and glued. Now its mounted to the square tube.

Circa 2010

a4790-leftwingsection1.jpg9a7e8-leftwingsection6.jpg
 

PTAirco

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And what happens to that square tube when the drag strut starts to exert a load? Tension or compression? It's going to bend that tube like it was made of cheese.

Where did the term "sail/anti-sail" strut come from? Never heard that before; is it an ultralight thing?
 

clanon

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Does it have any importance that the force Node ,being in the middle of the rib(soft point) would assert less force on the Composite glued Joint...:ponder:

a4790-leftwingsection1.jpg

More like this...?

PS: The wood rib is wing root ...right ?
 

BBerson

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It makes sense to do a diagonal midpoint like that for the wing tip rib because it prevents fabric tension bow in of the tip rib.
No diagonal is needed at the tip bay for anti-drag loads.
Now the root bay should have a proper anti -drag diagonal. And possibly a second diagonal to prevent fabric bow in at the root rib.
This particular builder may not have installed both root bay diagonals. The original might have two.
Just post him on his blog and ask him. Might save his life.
Since he said at least six times the instructions were lacking.
 

TFF

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Where are the fuel tanks? The engineering goof might be to include something like that.
 

Victor Bravo

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That wing MIGHT be wire braced, meaning it has tensioned wire diagonals that do connect to the spar/compression tube intersections.

If that is the case, then the diagonal brace that has been mentioned could be there to prevent the fabric from sucking the root rib in and nothing more.

So the key would be to look for wire bracing fittings on the PLANS, before anyone points the "Fickle Finger of Fate" (thanks Dan and Dick) at Mr. Wiebe.
 

pfarrjam

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Hi all, that was my video and what you see is the result of changes to the wing design that were not in the build manual, not in any annotated builder announcements, and not in any notes or documentation offered by Belite. When I called to ask what to do with the sail/anti-sail struts (aka compression struts) that didn't match the plans, along with a small pile of extra parts that I couldn't figure out, I was told the design had changed. They sent me poor quality pictures of the new wing layout and I matched my build to their "specs". I definitely point the fickle finger at Mr. Weibe, in my estimation he is an engineer who loves to tinker and tweak and change things on a whim. His lack of support for builders is very challenging. I had a very hard landing 3 years ago and ended up in a tree line, the wings held together extremely well. What you see is precisely in alignment with Mr. Weibe's design, nothing more or less. Anything you find on the web relating to the Ultracub is base on revisions on top of revisions on top of alterations, so very little is relative to the current design he's pushing out the door.
 
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