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Wing Tubes

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Phil 919/08/2015 11:14:20
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4208 forum posts
198 photos

most older plans show a wing construction that produces a one piece wing. It would be very useful if they could be built to split supported with a wing tube like most ARTF's.

is there a rule of thumb of how far into the wing a tube needs to go and how many ribs it will need to go through

iqon19/08/2015 11:51:53
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1326 forum posts
237 photos

I have only made the one ( but broke loads )- goes through 3 and stops before the 4th........

Piers Bowlan19/08/2015 12:32:33
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1243 forum posts
36 photos

From my experience two is enough if the ribs concerned are thin ply or reinforced with a ply doubler where the tube goes through the ribs. This is to stop the tube crushing the balsa ribs as all the bending load is transferred from the tube to the rib. But I concur with iqon, three is better. The diameter of the tube is a factor too, bigger is generally better.

Phil 919/08/2015 12:44:50
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4208 forum posts
198 photos

I have some 1/2 inch aluminium tube from slec in the shed and I would say it would be strong enough for any model I would build (upto 1.20 size models) I don't see it being any less strong than a ply brace but most artf have a much larger diameter than this

Adrian Smith 119/08/2015 13:10:48
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1900 forum posts
617 photos

If ever you need lightweight carbon fibre wing tubes www.easycomposites.co.uk do them. I can recommend them as I bought some CF tube to replace the metal one provided in my Weston Capiche 140 was too tight and was a pain to remove.

Bob Cotsford19/08/2015 13:46:04
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7219 forum posts
406 photos

I've done two conversions and used a tube length of around 30% of the span. I've bent 20mm tubes on 60 powered models, so my King Altair has something like a 25mm tube and the 40cc petrol powered Thunderbird is getting a 31mm one. I've used liteply half rib doublers on those ribs that the tube passes through to tie it to the spars, with full section 1/16" ply facing ribs at the join.

Erfolg19/08/2015 18:51:24
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10852 forum posts
1033 photos

The approaches adopted by modellers is quite interesting. It does go to show there is no one way that works, and others that do not.

Perhaps looking at some contemporary glass high performance models demonstrates how short the beam actually can be. Some are not more than 3" long on semi spans that are well over 50". many of these will take a full on winch launch.

If you go back in time to the 70s you will find wings with similarly short wing joiners.

So what matters? It is apparent that the stresses must be distributed into the either the wing monocoupe, or in the old days into the spars.

Also of great importance is the jointing tube/bar. It needs to be strong enough in itself to take the loads, particularly at the intersection of the wing to body. In the old days on highly stressed wings, extruded brass box section, with a drawn high tensile steel blade, would often be used. The major issue was the depth to width ratio was high. If not completely constrained, a twisting force could cause kinking.

So in my opinion, today a nice square CF bar works very well, can be very short, as long as the forces are distributed into the wing structure well. The use of some ply wing ribs can be helpful in the effective transfer of forces.

Dependant on the design, the body can also see some crushing/compression forces into the body, if some consideration is not taken to what forces the body in this region could experience.

It is easy to get carried away in how difficult wing dowel design and construction can be. Yet a look at a book such as the George Stringwell "Thermal Gliding" shows how simple in reality the task is, even with a big glider.

Geoff Peacock22/02/2018 15:47:16
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157 forum posts
58 photos

I'm modifying an old plan for a 48" Sopwith Scooter monoplane (changing it from single wing to split wing - and adding ailerons) and although reasonably happy with the info above, I'm not sure about securing the wings to the centre section I'm re-designing?

Has anyone had experience of DB Sport & Scale's Wing Retaining Clips? I'm familiar with how they work, but not actually seen them in action. The wings will be supported by working flying and landing wires (I hope).

Denis Watkins22/02/2018 16:02:38
2725 forum posts
137 photos

Geoff, I have done this split wing set up with a small Taylorcraft

Leaving the wing centre section as built in with the canopy, and wing tube

Each wing is located and held by nylon bolt accessed inside the cabin

 

Edited By Denis Watkins on 22/02/2018 16:03:24

Steven Shaw22/02/2018 20:40:19
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219 forum posts
138 photos

Geoff - I'm not familiar with the DB Sport & Scale clips but this is how I retain the 3 pieces wings on my Flugboot.

dscn2754.jpg

dscn2755.jpg

I used a shorter bolt in the completed plane

20170912_164257.jpg

Don Fry22/02/2018 20:49:40
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2401 forum posts
30 photos
Posted by Geoff Peacock on 22/02/2018 15:47:16:

I'm modifying an old plan for a 48" Sopwith Scooter monoplane (changing it from single wing to split wing - and adding ailerons) and although reasonably happy with the info above, I'm not sure about securing the wings to the centre section I'm re-designing?

Has anyone had experience of DB Sport & Scale's Wing Retaining Clips? I'm familiar with how they work, but not actually seen them in action. The wings will be supported by working flying and landing wires (I hope).

These things are the working end of a mastic gun. Same principle, and they work. Proviso, the diameter of the wire the gripper grips on, is critical. I believe the previous owner d DB Sorts and Scale used to reject about 50 % of his x gauge SWG wire, as it was not quite the right size between gripping and slipping.

Flyer22/02/2018 20:49:48
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419 forum posts
48 photos
Posted by Geoff Peacock on 22/02/2018 15:47:16:

I'm modifying an old plan for a 48" Sopwith Scooter monoplane (changing it from single wing to split wing - and adding ailerons) and although reasonably happy with the info above, I'm not sure about securing the wings to the centre section I'm re-designing?

Has anyone had experience of DB Sport & Scale's Wing Retaining Clips? I'm familiar with how they work, but not actually seen them in action. The wings will be supported by working flying and landing wires (I hope).

They will be fine Geoff. They work well on much larger aircraft, so for your 48inch it will be no problem. The guy who designed them is quite an engineer, and they are well over engineered for what you need. I expect the wings would fail before the retainers.

Ade

Don Fry22/02/2018 20:55:09
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2401 forum posts
30 photos

Wing tubes, replace dihedral braces. I have never seen a brace go through more than four ribs. Including the centre rib. Someone will name one with more.

John Stainforth22/02/2018 23:12:28
192 forum posts
38 photos

Don,

OK, I am naming one with more. For my 1/5th scale S6b I am using an 7/8" x 850 mm F3a Unlimited Gator carbon fibre tube and sleeve that passes through 9 ribs in each wing panel and 2 ribs in each wing root:

s6bmodel_showingwingtubes.jpg

s6b_model_5jan2017_4.jpg

And there is also a small, much shorter rear wing tube.

I don't see wing tubes as dead weights that have to be minimised. The tubes are superb (strong and light) spars that add considerably to the strength of the wings. So even if my design is overkill (which it probably is) I don't think the long wing tube is in anyway detrimental (except its cost!)

Phil 923/02/2018 05:42:32
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4208 forum posts
198 photos

If the wing has dihedral t​hen that will limit the length of tube you can use before it will protrude from the top of the wing. With the danger being it may end up too short to be strong enough. A flat wing will allow a full width gube if you really wanted

Allan Bennett23/02/2018 08:19:53
1316 forum posts
31 photos

If the wing was originally designed as a one-piece, there's presumably enough strength in the main spar to stop it from folding. The length of wing joiner you need is therefore basically determined by the strength of the inner and outer tubes (so that one won't punch through the other), how tight the inner tube is in the outer one (to avoid slop), and what length you need to accomodate the retaining screw. The outer tube, of course, needs to be firmly attached to the main spar, in which case the strength of the ribs in that location is probably of little importance.

Geoff Peacock25/02/2018 11:17:35
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157 forum posts
58 photos
Posted by Phil 9 on 23/02/2018 05:42:32:

If the wing has dihedral t​hen that will limit the length of tube you can use before it will protrude from the top of the wing. With the danger being it may end up too short to be strong enough. A flat wing will allow a full width gube if you really wanted

The Scooter's wing has no dihedral, although I will probably add a little to the design, just to make it look like it's not drooping.

Thanks to all for their input - I'm now happy to go ahead, probably with the DB S&S retaining clips, but not sure about tube sizes. No doubt I'll end up with a bit of 'overkill'!

Denis Watkins25/02/2018 11:28:52
2725 forum posts
137 photos

Luckily Geoff, which ever tube you choose

Weight wise it sits bang on the C of G, so its weight is dispersed evenly upon the model

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