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chiloschista

Floating wing joiners

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chiloschista

Hi,

I recently bought a Rosenthal DG600, to find that it has a floating wing joiner. In other words the fuselage is hung on four steel rods, while the wing joiner is completely loose from fuselage.

That is genial, because I guess all wings bendings, vibrations etc are not transmitted to the fuselage. The wing joiner does not have a break point as it is free to bend over the entire fuselage span.

Now I'm wondering what are the disadvantages. I guess after a hard landing, the wing roots could get more damaged? The setting of the geometry is more difficult because the lack of a solid joiner tube?

Working on the Pilatus B4 I could use the same system. I'm at the point wings are done and should proceed with wing - fuselage fixation.

Anyone experienced with that type of joiners, that would like to share experiences and suggestions?

Thanks!

Ric

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satinet

It's like that on f3f/b type models.

 

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chiloschista

I guess in those models the wing joiner touches the fuselage. In the DG600 the hole is about 5mm wider. The joiner is completely free.

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pete beadle

Hi Ric

The MPX ASH26 has a fully floating wing joiner too, I bought one second-hand, the original owner had no problem with the joiner, and neither  did I over the subsequent two years of my ownership, so for me, I found no disadvantages nor any obvious advantages either - sorry!:no:

Regards

Pete

BARCS1702

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chiloschista

Hi Pete,

that's a useful info, thanks. I found the instructions of that plane.

Probably, with carbon rods there is less risk to collect stress, which could bring to a break in flight.

Best regards,

Ric

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pete beadle

Hi Ric

My understanding was that the fully floating wing joiner was a feature used on full-size gliders, and the ASH26 was fitted with it because it was a fitting on the full-size, and therefore more "scale-like" I didn't research the reason for a fully-floating joiner at the time of owning the ASH, but did speak to several pilots at the London Gliding Club, who confirmed their "glass" gliders were featuring a fully-floating joiner. I didn't ask the LGC pilots  why a fully-floating joiner was necessary, but did speak to some ISA scale glider owners who said, in their opinion, the fully-floating joiner was "more efficient in coping with sudden shock loads as it was not fixed at a point that would become a failure point when a shock load was applied"

I think, in your quest for the reason why this joiner type features, should best now  be referred to one or two owners of "full-size" glass gliders:yes:

PS or perhaps Gary Binnie here on the forum?

Good luck

Pete

BARCS1702 

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isoaritfirst

Most moulded F3 type models have joiners that are a sloppy fit through the fuselage. 

The joiner is a tight fit into the wings and once they are pushed together and located onto the incidence pins the pins just have to support the fuselage. 

forces are a shear load so provide wings are well in place its unlikely that the pins will shear. The sloppy fit of the fuselage may allow the joiner to meet the fuselage if the pins started to give and may offer some extra level of support when needed. Joiner is free to flex in the centre of the fuselage.

Joiners fixed in tubes through the centre of fuselages can be troublesome. particularly if the joiner is a metal rod and it bends slightly, can be very hard to remove.

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chiloschista

Interesting infos are collecting here, thank you very much!

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Gary B

My ears were burning!!

This guide from the British Gliding Association illustrates the different wing joining systems.

In most cases the spar of each wing half is extended through the fuselage to mate with the opposite wing panel root rib, steel spigots on the end of each spar slide into captive swivelling bearings.

The spars are held in place by single or double pins which take no flight loads, they're just there to hold the wings together. The spar spigots of some gliders have to be NDT inspected or replaced at set flying hour or launches intervals. There would generally be two shorter spigots in each wing root to maintain incidence, mating with swivelling bearings in the fuselage. 

Older (wooden) gliders tend to have the spars meet in the centre.

Many modern gliders have options for varying span tip panels to allow them to fly in different classes (15 metre/18 metre/Open) or fit winglets. The tip extensions have a single extended spar that slides into a pocket, they are usually not secured by much. 

I never really thought of the wing joining system as being fully floating, it is to some extent, the spars certainly clear the holes in the fuselage.  My Mini Nimbus used to crack its front swivel bearings after very short landings in muddy fields (wings trying to swing forwards under inertia), most of my MPX gliders have cracked fuselages from the same force, the ASW 22 has a dowel anti-crush strut which works. I've probably got better diagrams in an old Slingsby fibre glass repair manual, wherever it is!

   Cheers

       Gary

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pete beadle

Hi Gary

My fault, sorry.....I suggested  to Ric that you were probably THE person to have the answer to his query and, it seems "you am de man!":):thumbsup::yes:

Thanks for this - it answers my questions too!

Regards

Pete

BARCS1702

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chiloschista

Ouch, I thought it was a simple question. It is becoming really interesting instead.

Thank you very much Gary for that details (and thanks Pete who did your ears burning = : D)!

I will definitely try something with the Pilatus. Just wondering now how will it handle hard aerobatics, but I guess that's not a problem.

Ric

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Gary B

No worries!

There are a few three panel gliders, the Slingsby Skylark and I think the SZD Pirat.

Best to run away when a rigging party is needed, weighed a ton!

The ASH 25 is four panel, also best to do a runner!

There is a story of a chap who flew a 300 km task and his wings fell off as he landed because the main pin hadn't been fitted, not sure if it's true but it's possible as the wing root joints always get taped to minimise drag inducing air bleeds.

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chiloschista

Tape fixed wings 🤣

I can imagine in real aviation there are stories like in flying model fields ...

... and this remember me that I still have to find the way to fix wing halves. Multiplex, Monoblock, Hacker, ... tape 😛?

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nimbuspete

In my (limited) experience, the large majority of composite gliders have structural wing joiner pins. Some, like the Vega, have a pin that just stop the wings moving apart.

Most schempp gliders have a single load carrying pin on one side whilst DG gliders have 2 load carrying pins, one on each side (which can be a right pain of not adjusted properly).

The fuselage carrying stubs are usually mounted in spherical joints so they are no stress concentrations when the wings flex.

I agree with keeping a wide berth of anyone rigging a Skylark but most parts of a 4 part wing, Nimbus or ASH25, are not much heavier than the average 15 meter wing panel,  just more time consuming.

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pete beadle

Hi Nimbuspete

and don't forget white electrical tape consuming too:thumbsup::)

Regards

Pete

BARCS1702

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