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WHO'S BUILDING WHAT FOR 2021

Anything to do with gliders & gliding.
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Noël Rumers
Posts: 281
Joined: 20 Mar 2015, 10:29
Location: Hoboken Antwerp

Re: WHO'S BUILDING WHAT FOR 2021

Post by Noël Rumers »

Gromotec in Germany sell glass fiber rods in a few dia.
Petrausch sells the fenolyth tubing for them.
I just ordered for a friend a 16 mm glass rod for his 4.4 m span glider.
One could use also the hardened steel rods that are used for linear bearings.
They come with weight too but are the only steel shafts that can be used my thinking...
From 20 mm on you can buy them hollow as well.
Sizes are 5 - 8 - 12 - 16 - 20 - 25 - 30 - 40 - 50 - 60 - 80.
Hollow they come from 20x14 - 25x15.4 - 30x18 - 40x27 - 50x28 - 60x34 - 80x56<ID.
Gromotec sells glass fiber once from 2 - 4 - 6 - 8 - 10 - 12 - 16 - 18 - 20 - 25.
Petrausch sells the tubing from 10 mm ID.
He also sells Strongal ALu tubes, but these are not fit for gliders!!! His own saying to me!!!
I do hope this helps!
Noël

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B Sharp
Posts: 810
Joined: 19 Mar 2015, 17:18
Location: Perthshire

Re: WHO'S BUILDING WHAT FOR 2021

Post by B Sharp »

Noel, I am fiberglass rod averse having used it for wing joiners on thermal soarers in the past. My first experience was when one let go while winching on a breezy day. There was a mighty bang followed by a one winged model returning to earth. When the wreckage was examined the glass joiner had exploded but the fibres had not let go. They had formed something like two paint brushes joined together at the ends of the bristles. The second occasion was on a clumsy landing where one joiner let go. This time the fibres had expanded to more than double the original rod diameter and proved impossible to remove from the wing or the fuselage!
Brian. :o

Nigel Ellis-Gray
Posts: 7
Joined: 03 Nov 2020, 05:58
Location: France

Re: WHO'S BUILDING WHAT FOR 2021

Post by Nigel Ellis-Gray »

My query about wing joining materials has brought forth several different views. Mild steel will bent, fibreglass rod/tubes can fracture or disintegrate and carbon can suffer structural failure at the wing/fuselage interface especially in the case of a hard landing.

That leaves us with the original material, brass box/steel blade. This solution goes back years. I’m not suggesting it isn’t good but surely it is not the only solution for long wings of larger heavier gliders given the advances in material science.

I may well have to stick to brass box/steel blade and swallow the cost but I’d like to investigate the alternatives first.

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mjcp
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Joined: 29 Jul 2015, 08:14
Location: A wind swept hill with no wind, in driving distance of Windsor, UK
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Re: WHO'S BUILDING WHAT FOR 2021

Post by mjcp »

Consider also, the examples above of things failing are not equivalent to a steel blade: Rods are not blades and nor are bars.

The blade is *VERY* good at its job: resisting a bending force, when supported by the box and wing etc, in the vertical. A rod or bar will be less so, but will be better in the horizontal (not much use on a wing joiner), so its a little unfair to make them as "not as good", they are not intended to be, they are different shapes!


Here's an interesting article comparing Glass, carbon and Kevlar. Note under tensile strength, all three are pretty even! (would be good to find an equivalent for the steel bar/box for comparison) https://www.christinedemerchant.com/car ... ison.html
m̶j̶c̶p̶ Marc

Hanger -
Graupner (old) K-8b, Mini Solius chuck glider conversion, UMX ASK-21, HF/Czech 2m ASW27, DG808s 4m, X-models Mini-blade, Lidl glider pitcheron.

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B Sharp
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Joined: 19 Mar 2015, 17:18
Location: Perthshire

Re: WHO'S BUILDING WHAT FOR 2021

Post by B Sharp »

Nigel, I don’t think there is such a thing (in normal use) as an unbreakable wing joiner; all of them have their limits. It is unfortunately up to you decide the weight of the model, the proposed flight envelope and the likely loads and how aggressively you want to fly and choose/design the joiner accordingly.
14/15mm steel blade is very good and I have regularly used it in a variety of models over the years. The smaller and lighter models have had single blades while heavier, larger (4 to 5 metres or above) have had two parallel blades. These blades do bend and you may find that you may have to replace them if you have been a little too enthusiastic in your flying. I had one 1/4 scale glider where one side of the blade was almost tied in a knot. Having said that there was a Greenly tug with motor running dangling under it at the time.
I think all of the material options will work so long as you choose a size that is capable of handling the flight load x 2.
Brian. :)

Nigel Ellis-Gray
Posts: 7
Joined: 03 Nov 2020, 05:58
Location: France

Re: WHO'S BUILDING WHAT FOR 2021

Post by Nigel Ellis-Gray »

Brian
In the absence of being unable to calculate the size of alternative wing-joiner systems to the brass box/steel blade I will stick to that solution as it’s tried and tested. It the only sensible thing to do. I’d like to thank everyone for their input of this issue and I’m sorry if the original thread has been hijacked by this issue!! :)
Nigel

roo Hawkins
Posts: 846
Joined: 18 Mar 2015, 20:12
Location: Northamptonshire

Re: WHO'S BUILDING WHAT FOR 2021

Post by roo Hawkins »

Have you thought about titanium rod for joiner. Very expensive but good and light. There is a company on eBay that is selling meter lengths of grade 23 medical grade for £29. Used it in my 7 meter ash 31 after my steel bent no problem now.

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Peter Balcombe
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Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: WHO'S BUILDING WHAT FOR 2021

Post by Peter Balcombe »

What grade of steel were you using Roo?
I have a high carbon content (machine slide) rod for my 1/4 scale ASK21.
Stainless steel would be too soft.

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chris williams
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Joined: 10 Mar 2015, 10:50
Location: Blandford Dorset

Re: WHO'S BUILDING WHAT FOR 2021

Post by chris williams »

Bergfalke progressing nicely... Span: 3.7m, current AUW ballasted for cg: 6.5lbs
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roo Hawkins
Posts: 846
Joined: 18 Mar 2015, 20:12
Location: Northamptonshire

Re: WHO'S BUILDING WHAT FOR 2021

Post by roo Hawkins »

Peter Balcombe wrote:
18 Feb 2021, 11:31
What grade of steel were you using Roo?
I have a high carbon content (machine slide) rod for my 1/4 scale ASK21.
Stainless steel would be too soft.
Hi Peter It was stainless 303 18 mm it has been ok on all my other gliders .but the ash 31 is was over 16 kg .using titanium and I have taken 1/2 kg of lead out of the nose. .now under 14kg.

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