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SHORT BROS NIMBUS SCALE 1:3.5

Let us all watch your new project progress.
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B Sharp
Posts: 649
Joined: 19 Mar 2015, 17:18
Location: Perthshire

Re: SHORT BROS NIMBUS SCALE 1:3.5

Post by B Sharp »

That is a seriously impressive piece of work Jilles.
Brian.

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terry white
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Joined: 18 Mar 2015, 21:08
Location: wareham,dorset.england

Re: SHORT BROS NIMBUS SCALE 1:3.5

Post by terry white »

Excellent work as always Jilles and a super build tread too. Well done.

Jilles
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Joined: 22 Mar 2015, 10:27
Location: Australia
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Re: SHORT BROS NIMBUS SCALE 1:3.5

Post by Jilles »

Spar front webbing at wing joiner sleeve and near gull radius added. Hinges and horn for air brakes fabricated. The hinges are fabricated from scratch from square brass tubing, The prototype has the brake blades behind the main spar but is hinged at the front to the spar. The hinge main body is a 5/32"x0.014 square tube the hinge bit a 1/8"x0.014 square tube. all brass from K&S engineering. The reason to go for square tube is that it gives a better contact area for hard soldering the parts together. The hinge pins are 3/32" brass round bar. It makes no difference if the round pin hinges in a round or square tube. Because the hinges are running over the main spar the spare is actually sunken below the rib surface top & bottom otherwise one has to make a slot in the main spar, what I did nor wanted for strength reasons. The brake fitted in to the wing, checked movement and added ply surface
note in picture W11 that the sunken main spar has the advantage that the shoulder spars can run over the main spar resulting in a proper shear joint

ply webbing to front of spar
ply webbing to front of spar
ply webbing at gull radius
ply webbing at gull radius
brake hinges and horn
brake hinges and horn
hinges and horn epoxied in place
hinges and horn epoxied in place
servo screws added from underneath
servo screws added from underneath
srews sanded flat and brake fitted in wing
srews sanded flat and brake fitted in wing
checked movement
checked movement
ply surface added to brake
ply surface added to brake

Jilles
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Joined: 22 Mar 2015, 10:27
Location: Australia
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Re: SHORT BROS NIMBUS SCALE 1:3.5

Post by Jilles »

With the brake in place the balsa leading edge was fitted and sanded over the full wing length. on top of the main spar balsa was fitted and sanded flush with the rib surface. 6 mm balsa sheets added between the ribs in the gull radius for future ply support.
My drawings specified 0.4mm ply on the D-box. Due to the larger area to cover I decided to go with 0.6 mm up to and including the gull radius.
Ply sections were prepared and ironed on with PVA. The ply section will be between 400 to 450 mm long. Longer sections are harder to control
When applying the PVA masking tape is used so only glue is added where required. One could fit the top ply cover over the full wing length in one day was it not for the fact that we have here days of 35-38 degrees C. making it 40+ in my workshop. so only early morning working sessions are possible.
Note the leading edge was sanded only 5-10 degrees past the vertical at the bottom. I do not want to take the wing from the base board until all the top D-box ply is in place.
How things are kept in place for the bottom ply will be revealed later

air brake ready
air brake ready
6mm balsa sheest between ribs at gull radius
6mm balsa sheest between ribs at gull radius
l/e sanded , balsa to top of spar
l/e sanded , balsa to top of spar
cutting ply d-box sheeting
cutting ply d-box sheeting
second sheet prepared glue area taped.
second sheet prepared glue area taped.
PVA added waiting for an hour now
PVA added waiting for an hour now
iron on the wet ply
iron on the wet ply
second sheet in  place
second sheet in place

Jilles
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Location: Australia
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Re: SHORT BROS NIMBUS SCALE 1:3.5

Post by Jilles »

To cover the D-Box over the gull radius I did the following. At radius area in the D-Box 6 mm balsa was fitted between the ribs and sand to the required contour. A ply section was cut to size and three grooves were cut running approximately from halfway to the front. The slots start with a zero width ( knife cut) to 1 mm wide at the front. The ply was fitted with the PVA iron- on method and worked well. Because of the compound curve at the front there would be to much ply material, the three wedge type slots took care of this. This way would never be possible on a full scale because it would weaken the wing structure, but on this model with 6 mm balsa backing it is not an issue. There are probably other ways of doing this but for me it worked well .Because it will be a painted model the slots will be invisible. After this two more play sections were added, two more and the top of the D-Box is fully planked and I can start thinking of the bottom.
Ply section cut and slotted
Ply section cut and slotted
area is filled in with 6 mm balsa and radius sanded
area is filled in with 6 mm balsa and radius sanded
final result
final result
two more ply section added today
two more ply section added today
20190214_192320.jpg

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VinceC
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Re: SHORT BROS NIMBUS SCALE 1:3.5

Post by VinceC »

Good work Jilles and coming along well. On my See Adler, with a very rounded Gull Break, I followed the full size system and panelled each rib bay individually, although I relied on a substantial ply support between the top and bottom spars

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RobbieB
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Joined: 07 Mar 2015, 22:22
Location: North West

Re: SHORT BROS NIMBUS SCALE 1:3.5

Post by RobbieB »

On my Gull3 I too sheeted the radius gull transition with individual pieces, scarfed and wrapped right around the LE and continued underneath back to the spar in one piece with no balsa support underneath the sheeting and it it has been fine.
The resulting flat sections of sheeting over the gull transition were rounded out with thin layers of filler - again not visible under the paint.

Jilles
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Re: SHORT BROS NIMBUS SCALE 1:3.5

Post by Jilles »

The underside of the D-box is now planked completing the planking in front of the spar. the building tabs were only removed in front of the spar
The remaining tabs on the spar webbing and to the rib rear ends were used to check that the wing saw level and then secured to prevent a twist in the wing With the front planking now completed the wing is rigid. prior to closing the box the servo wire harness was fitted and double checked that all connections are as it should. because I can get them for free I do use high quality screw plugs used in professional electronic equipment. The female plug comes with a 3 meter wire fitted, 8 wires in my case. I removed the outer rubber protection for weight saving. I do prefer a single plug if more than one channel is involved. This wing has 3 servos/channels. This prevents mixing plugs at the field. I do not like the Multiplex connectors. hard to plug in or undo
wing underside
wing underside
securing wing inner section to board
securing wing inner section to board
checking if wing is level
checking if wing is level
checking if wing is level
checking if wing is level
servo wire harness fitted
servo wire harness fitted
Front planking completed
Front planking completed
Front planking completed
Front planking completed

Jilles
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Joined: 22 Mar 2015, 10:27
Location: Australia
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Re: SHORT BROS NIMBUS SCALE 1:3.5

Post by Jilles »

The T/E is a 1.5 mm ply core ( part of NC-laser kit) 1. 5mm balsa to top & bottom sanded back towards the rear edge until 1.5mm ply is just visible at the rear end
6 mm balsa fitted to aileron end ribs for stiffness against tension in future film of cloth cover 0.4mm ply planking prepared and glued to T/E. A steel bar is used to assist in clamping and keeping things straight. Future builders can use a solid balsa T/E if they wish but I like this setup on all my models. It is a bit time consuming but they result is a strong and straight edge . It stays straight over time as well.
The prototype ailerons are hinged at the top. The model is the same with Dubro 257 Nylon hinges with removable cotter pins. The aileron is 1.2 m+ long so 6 pairs of hinges are used. I like these hinges because of the removable pins. 1 mm deep recesses were cut into the top spars of wing and ailerons to make the hinge blades flush with the underside of the future 0.4 mm ply planking. Because of the long aileron, like the prototype the ailerons is moved at two locations, two servos in the model. Each with its own channel

aileron diagonal ribs fitted
aileron diagonal ribs fitted
1.5mm balsa added to T/E
1.5mm balsa added to T/E
0.4mm top ply T/E clamped with steel bar
0.4mm top ply T/E clamped with steel bar
T/E planked at inner section
T/E planked at inner section
top of inner section planked with all bits and pieces
top of inner section planked with all bits and pieces
T/E planking prepared for aileron
T/E planking prepared for aileron
first aileron T/E planking fitted
first aileron T/E planking fitted
top spars recessed for hinges
top spars recessed for hinges

Geoff Pearce
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Joined: 18 Mar 2015, 09:11
Location: SN11 9EE

Re: SHORT BROS NIMBUS SCALE 1:3.5

Post by Geoff Pearce »

Jilles, that looking really nice, I like the gull angle.

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