SHORT BROS NIMBUS SCALE 1:3.5

B Sharp · Post by **B Sharp** » 03 Feb 2019, 09:20

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

Post by **terry white** » 03 Feb 2019, 15:04

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

Post by **Jilles** » 12 Feb 2019, 03:55

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 at gull radius

: brake hinges and horn

: hinges and horn epoxied in place

: servo screws added from underneath

: srews sanded flat and brake fitted in wing

: checked movement

: ply surface added to brake

Post by **Jilles** » 12 Feb 2019, 04:17

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

: 6mm balsa sheest between ribs at gull radius

: l/e sanded , balsa to top of spar

: cutting ply d-box sheeting

: second sheet prepared glue area taped.

: PVA added waiting for an hour now

: iron on the wet ply

: second sheet in place

Post by **Jilles** » 14 Feb 2019, 09:43

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

: area is filled in with 6 mm balsa and radius sanded

: final result

: two more ply section added today

Post by **VinceC** » 14 Feb 2019, 10:20

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

Post by **RobbieB** » 14 Feb 2019, 11:14

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.

Post by **Jilles** » 26 Feb 2019, 09:21

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

: securing wing inner section to board

: checking if wing is level

: checking if wing is level

: servo wire harness fitted

: Front planking completed

: Front planking completed

Post by **Jilles** » 26 Feb 2019, 09:54

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