Sunday, 31 July 2011

Nieuport Build Part 15 - Finishing the Top Wing Centre Section - Part 2

The top wing panels are almost ready for the .8mm plywood centre section sheeting to be applied, but first the aileron bell-cranks have to be pinned to the torque tubes with metal dowels. 

The carbon fibre torque tubes had been marked up when they were cut to the correct length in the last post. 

The first stage was to drill a 2mm diameter hole in the end of each carbon fibre tube so that the hole was on the centre line of the aileron box when the tube was fitted. This would allow the bell-cranks to sit centrally within the aileron box when finished. 

2 dowels 15mm long were cut from piano wire and the ends were filed to a 45 degree angle to act as a 'lead'. This 'lead' makes locating each dowel through the holes in the torque tubes much easier.

Torque tubes, metal dowels and bell-cranks.

The metal dowels were placed through the holes in the torque tubes and then the bell-cranks slid onto the tubes until they sat up against the metal dowels.

Bell-crank, metal dowel and torque on wooden blocks.

Each torque tube, dowel and bell-crank was then packed up onto 2 wooden blocks to clear the end of the tube whilst the position of the dowel was marked onto the surface of the bell-crank with a scriber.

Both bell-cranks were marked up as shown above.

After the bell-cranks had been marked up they were cut out with a fret-saw and filed to size so as to obtain the correct fit.

 Bell-crank with metal dowel fitted.

The main components, bell-crank with cut-out, dowel and tube.

The 2 finished bell-cranks and torque tubes with
metal dowels fitted. Not glued together at this stage.

Now that the bell-cranks are finished the 'scale' spar detail can be permanently glued in place. The 'scale spar passes through the rear openings in the centre section. The holes were opened up slightly so that  the spars would be a good fit.

The 'scale' spar passed through the large
rectangular hole to the rear of the centre section.

The 'scale' spar, torque tube and
aileron bell-crank prior to installation.

Next the 'scale' spars were glued in place between the existing rear wing spars either side of the aileron boxes. At the same time the bell-cranks were also installed.

'Scale' spar in place with bell-crank fitted.
The torque tube is also visible but NOT glued in place at this stage.

The 2 'Scale' spars and bell-cranks fitted.
Again the torque tubes are visible but NOT glued in yet.

Now... the .8mm plywood centre section sheeting can be last!! This sheeting has already been pre fitted and cut exact to size and the ends sanded to a taper. The plywood sheet was marked and taped into position before gluing the front of the sheet to the leading edge.

Centre section plywood sheeting marked up prior to gluing.
It was taped in place from this point back to the curved centre section cut-out

With the sheet held securely in position from the centre to the rear and unable to rotate, it is very important that the sheet does not twist, the front section was left free so that it could be pushed down onto the surface later.  I then applied cyanoacrylate 'kicker' to the front edge of the plywood and medium cyanoacrylate to the leading edge.

The plywood was then pushed firmly down onto the surface of the ribs with a wooden block from the centre to the leading edge where it was held for a moment while the cyanoacrylate set with the aid of the 'kicker'.

The plywood centre section sheeting with the tape removed.

Now that the sheeting was held securely at the front the rest of the sheeting was glued in place with wood glue. Masking tape was used to hold the sheet down until the glue had set, over night.

The rear of the sheet was held firmly in place with 'G' clamps and a wooden block. The block keeps the end of the plywood flat and prevents it from lifting.

Sheeting held in place with tape and 'G' clamps whilst the glue sets.

After the centre section had thoroughly set the 'G' clamps and tape were removed and everything was sanded down. The tapered ends of the plywood sheeting were then blended in with filler at the leading edge and centre section curved cut-out.

As the plywood centre section sheeting is applied to the top of the ribs and no allowance was made for the additional thickness of the ply you create a 'step'. This 'step' will be emphasized when the covering is applied so it's best to 'blend' it into the structure.

Plywood centre section sheeting applied and 'step' created.

It needs to look like this...

To achieve this it will be necessary to add some strips of balsa wood here and there. The 4 pieces of balsa that were glued to each spar, front and rear, were pre sanded to a taper.

There were 7 pieces of balsa cut for each wing panel.
The 7 pieces were than glued in place with medium cyanoacrylate for speed then sanded down.

Pieces glued in place prior to sanding.

Sanding the wood down.

To prevent some areas from being sanded down 'masking tape' was applied. And finally the excess 'scale' spar was sawn off and sanded flush with the centre section rib.

 'Scale' spar installed and sanded flush.

The 2 centre sections finished.

The top wing is pretty well complete now. The aileron hinges require installing and the underside of the centre section of both top wing panels require a 'land' making around the front aluminium centre section strut mounting. This 'land' is required for  the covering to adhere to and will be made when the lower wing panels are fitted to the fuselage. I intend to fit the top wings to an inverted  fuselage, as the top wings are flat, then fit 'temporary' interplane struts whilst the lower wing panels are fitted. The wings will be rigged at later stage.

When the interplane struts are made and finished off they will replace the 'temporary' ones used earlier. Once the actual interplane struts are installed the wings can be rigged. However, final tensioning of the rigging wires will be done at a later stage, setting the incidence and washout etc. 

Remember ALL the rigging wires are functional and should NOT be omitted.

To be continued...

Friday, 22 July 2011

Nieuport Build Part 14 - Finishing the Top Wing Centre Section - Part 1

After the top wing panels had been fitted to the fuselage they were removed so that the remaining work could be finished. To be sure that the wing panels retained a good fit at the centre join whilst finishing  them off they would be bolted back together with 2 scrap 6mm thick plywood braces, but first the tubes and .8mm plywood capping were fitted.

The 4 tubes were made rough with coarse abrasive paper so that the epoxy glue would 'key' to the surface.The 2 hardwood dowel 'plugs' were glued in first, these  tubes were marked up 'FRONT' so I didn't stick them in the rear by mistake later.

Wing joining tubes, dowel 'plugs' and epoxy.

Dowel 'plugs' glued in place.

The components of the starboard wing panel less the riblets.

The plywood centre section sheeting will not be applied yet until the 'scale' spars have been permanently glued in place. The sheeting has, however, been cut  exact to size and all the short sides have been chamfered. Chamfering the edges now makes blending the plywood into the balsa leading edge and balsa centre section cut-out much easier. If the plywood was applied then blended in you risk the chance of sanding the balsa wood away first before the plywood.

Chamfered plywood before and after.

The wing joining tubes and captive nuts were than glued in place with epoxy. The tubes protrude slightly as the plywood capping ribs still require fitting.

Wing joining tubes glued in place and riblets trimmed and ready to fit.

The plywood capping and riblets were then glued in place with wood glue. Not forgetting to cut the 2 extra cut-outs to the rear of each capping rib for the 'scale' spars to slide through. Where the riblets touched the aluminium tubes epoxy was used to secure them.

Plywood capping held in place with masking tape while the glue was setting.

To give the plywood centre section sheeting more purchase at the front and to stop the sheet lifting after gluing, it's a good idea to fill in the riblet bays in this area with scrap balsa block.

Balsa block infills will be sanded down later.

Now is a good time to colour the inside of the aileron boxes and the visible section of the 'scale' spar detail. A light oak water based stain was used, light oak being the best colour to replicate 'old pine'.

Aileron box and spar with light oak varnish applied.

The reason for staining the boxes etc now is because the 'scale' spars require gluing in place before the center section sheeting is applied. If the centre section sheeting was applied first you can't get at the spars to glue them in place and these spars are functional.

Also the aileron bell-cranks have to be installed at the same time as the 'scale' spars are glued in. So I best not forget to include those bell-cranks!! I'll cover this in a future post.

Whilst on the subject of ailerons, I also cut the 2 torque tubes to length. These tubes were also marked up on each end so that I would know were to drill the holes for the aileron bell-crank retaining pins, installation details to follow.

Aileron tube being cut to length.

Next the leading edge of centre section was sanded down, this can be done with the wing panels joined together as the wings are flat.

Centre section leading edge sanded down.

Underside view of the centre section showing temporary plywood joiners.

Also seen in the above picture is a white plastic insert placed into the cut-out for the rear mounting bracket fixing. This plastic insert was there to stop filler from getting in the aperture.

A polyester resin '2 part' wood filler will be used to make good the centre section join. The underside was filled first.

Wood filler applied to the underside of the centre section, the easy one.

Then came the top of the centre section. Looking at scale reference this area was more square than round in section and therefore needed 'squaring' off.

The filler was added gradually first to the curved section then to the top section, the edge of the filler was finally sanded to a right angle.

Filler sanded at right angles, port wing panel.

Once the filler had been sanded at right angles the sharp edges were then chamfered. The amount you sand off will be determined by the size of radius you require.

Remember the 'shadow sanding' technique, it can be seen to full effect in the following pictures. The shadows cast clearly show your progress during the shaping process.

Sharpe edge sanded off, note the taper of the chamfer
so as to blend in with the trailing edge.

Both sides chamfered to a uniform shape and confirmed by the shadows cast.

And finally the sharp edges of the chamfers were removed until a 'sweet' curve was achieved.

Chamfers rounded off and final shape finished with fine abrasive paper.

All that needed to be done now was to 'split' the 2 sections on the centre join, currently held together by the wood filler. This was done with the aid of a razor saw.

Razor saw being used to separate the wing panels.

Wing panels after separating.

The next post will see the centre section finished...hopefully

To be continued...

Friday, 15 July 2011

Drilling Holes Through Hardwood and Plywood

Workshop Tip No.9
When holes are drilled through wood the drill bit inevitably tears the wood around the hole on exit. To stop this happening place a piece of scrap wood underneath the hole being drilled. The drill bit passes through the work and into the scrap wood. When the scrap wood is removed it will reveal  a clean, neat exit hole.

Use a Centre Punch Before Drilling

Workshop Tip No. 8
Whenever you need to drill a whole though hardwood or plywood it's a good idea to use a 'Centre Punch' to mark the position of the hole first. This process is referred to as a 'centre-pop' and is common practice when drilling holes through steel etc. This 'centre-pop' will stop the drill bit from wandering away from the position marked.

Thursday, 14 July 2011

Nieuport Build Part 13 - Fitting the Top Wings to the Fuselage

The 4 aluminium wing joining tubes were placed into the wings during construction so at this stage I know they are all aligned correctly.

The only tubes that require trimming are the 2 at the rear. This is due to the inclusion of the aileron boxes. All the tubes were placed into the holes in the wing ribs, port and star board, and then the .8mm ply capping root ribs were placed over the ends of tubes. The rear tubes were then marked up with a fine pointed marker pen as close to the surface of the .8mm ply as possible. The rear tube fits up against the aileron box thus blanking the tube off and preventing the wooden wing joining dowel from working its way through the tube and into the wing. The 2 front tubes do not require trimming and just needed a short length of dowel gluing into the end of each tube, again to prevent the wing joining dowel from ending up inside the wing. The 2 rear tubes were then cut to length with a tube cutter, about 6mm was removed from each.

Wing joining tube marked up ready for cutting.

Rear tubes cut to length with tube cutter.

The 2 .8mm ply capping ribs needed to have a section cut from the front and rear ends to allow them to fit correctly over the centre section supports.

.8mm ply capping showing front cut-out.

.8mm ply capping showing rear cut-out.

Later there will be other cut-outs to the rear .8mm ply capping for the 'scale spars' to pass through. The rear 6mm ply mounting plate seen in the above picture has been rounded off to attain a good fit with the steel centre section mounting plate.

Having done the above preparatory work I could now get on with mounting the top wings...

Starting with the port wing it was time to see if the panels fit. This was the first time they had been offered up to the centre section struts and the first fit wasn't too bad. After opening up the slot in the balsa wood behind the ply mounting plate the wing panel dropped onto the rear steel centre section mounting plate and the panel was clamped in place with a small 'G' clamp.

Rear top wing clamped to mounting plate with 'G' clamp.

As previously mentioned the fit was made good to the rear mounting bracket by removing the corners to the rear ply wood plate. It was at this stage I could see that fitting the captive nuts for the rear fixing bolts was going to be a bit of a squeeze!! I'll worry about that later.

Front top wing clamped to centre section strut with 'G' clamp.

When both of the top wing panels had been correctly fitted to the centre section mounting brackets the panels were 'G' clamped to the front centre section strut complete with the 2 .8mm ply capping ribs, the 4 wing joining tubes and the 2 wooden wing joining dowels. Also included was a piece of stiff card placed in the centre of the 2 panels, this substituted the Solartex covering.

View of the top wing panels 'G' clamped in place.

Top wing panels 'G' clamped in place, underside.

Now comes the IMPORTANT part making absolutely sure that the wings are 'square'. Carefully measure from a know point on each wing panel, as close to the tip as possible, to the centre of the sternpost. When completely satisfied that BOTH measurements are identical give the 2 'G' clamps a final tighten to make sure the 2 wing panels stay firmly in place. Now we can mark the positions of the fixing holes onto the ply plates through the holes in the metal bracket and front strut.

Position of fixing holes marked on wing panels.

After these holes had been marked they were 'centre punched' and 'pilot' drilled. Each hole was then drilled out to the correct size to accept the captive nuts.

Fixing holes drilled in port top wing panel and ready to receive the captive nuts.

Front captive nuts in place, star board wing panel.

'Problem' captive nuts to the rear!

Now here's where the problem lay! Out of the 10 captive nuts all but 4 were easy to install. The 4 problem ones were those situated at the rear. 2 required a 'flat' to the side and the other 2 required countersinking into the ply mount so that the 'scale' rear spar could pass over them.

Rear captive nuts installed. They will be glued in place later.

And finally the top wing panels could be bolted onto the centre section. The bolts will get cut down later and the wing joining tubes still require gluing in place along with the captive nuts and the ply capping ribs.

Top wing panels bolted in place -

In the next post I'll be finishing off the top wing centre section.

Workshop Tip No.8
Whenever you need to drill a whole though hardwood or plywood it's a good idea to use a 'Centre Punch' to mark the position of the hole first. This process is referred to as a 'centre-pop' and is common practice when drilling holes through steel etc. This 'centre-pop' will stop the drill bit from wandering away from the position marked.

Workshop Tip No.9
When holes are drilled through wood the drill bit inevitably tears the wood around the hole on exit. To stop this happening place a piece of scrap wood underneath the hole being drilled. The drill bit passes through the work and into the scrap wood. When the scrap wood is removed it will reveal  a clean, neat exit hole.
To be continued...