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Warbird Replicas Spitfire LF mk IXc


Ady Hayward

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Hi Folks.
After the skinning of the wings comes the aileron servo mounts.

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The servos are fixed to the inside face of the servo access plate so that the whole piece can be easily removed when required. There were two pieces on each side, one plywood and the other balsa so it was important to ensure that a left and right side were laminated together.

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The servo will fix to the plywood face and the balsa face will be on the wing surface to allow it to be sanded flush with the wing.

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The servo mountings were simply pieces of scrap 1/4" ply cut to fit the servo lugs, and glued in place using the servo as a jig. When the CA adhesive had cured I removed the servo and fixed a balsa buttress to the ply plate to ensure that it will be fixed firmly in place, and then fixed the servo to the plate using small self tapping screws.


Adrian

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Now that the leading edge is in place, the locating dowel was fitted in place.

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I carefully drilled through the leading edge taking care to not let the drill bit wander as it drilled through the two centre rib slots. I needed to use a long round file to open out the hole slightly so that the dowel can reach and just enter the second wing brace hole. When I was satisfied with the fit I made a very slight taper on the front end of the dowel and glued the dowel in place. I coated the dowel in a thin layer of PVA and pushed the dowel firmly home which left around 10mm of dowel protruding.

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The wing leading edges and wingtips were then sanded to shape ensuring that the shape was copied on the other half. At this stage only the worst of the blemishes were treated with some lightweight spakle (Filler) and carefully sanded to the wing profile.

Adrian

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Hopefully I should get my kit in the next few weeks. I'm thinking of glass cloth as a covering, early days I know but I like to prepare well I'm advance. Ady, I have never used glass cloth before, do you think the kit is ok for a first attempt? I don't think much of building something just to try my glass cloth skills before the Spit, but then again I don't want to potentially ruin all my woodwork. Clue me in please!

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I personally use the zap finishing resin and thin it 50% with epoxy thinner or meths. I then use an epoxy brush and stipple away until its all sorted. I quick blow with a heat gun helps evaporate the thinner and the resin cures as normal. I find this gives a light finish and after a sanding and another thin layer of resin..and another sand the surface is ready for primer and paint. This method will not add a lot of strength, but gives an excellent basis for paint.

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Hi Steve, All.

This kit is definitely one that I would recommend for a first time balsa basher and should present few if any issues with a glass cloth finish. This build will include a glass cloth covering but using Water Based PolyUrethane (WBPU) instead of a polyester or epoxy resin. Both the Polyester and epoxy resins can become a little fraught due to the finite working time whereas the WBPU being water based can be extended with further wetting. This eases the covering process considerably and allows the user to manipulate the cloth around compound or difficult curves such as wing fillets etc.

The covering adds a little extra strength and durability against hangar rash and gives a very good surface for painting especially on foamy types. If you do a search for the builds under my name you will see the types of structure where I have used this covering/ finishing method.

Adrian

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Following the sanding of the wing surfaces my next task was to cut out the ailerons. A razor saw was used to carefully cut in from the trailing edges to the aileron hinge-line (Easily seen by having a bright light shine through the balsa to show the hinge-line) and then to cut through the rib extensions and the top wing skin to release the ailerons.

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The ailerons were sanded to shape and any openings in the aileron ends or aileron recess filled with scrap balsa.

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I used some of the surplus thin plywood to make facings for the recesses and end plates for the ailerons. These give nice sharp edges that enhance the look of the ailerons.

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This completed the wing for now and I fitted the motor to the motor/ battery mount and glued the assembly into the fuselage using epoxy or PVA resin as needed.

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It is important to ensure that the assembly remains straight with zero side or down thrust.

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Adrian

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Now that the motor was fitted in place the cowling could be assembled and fitted. It proved essential to thoroughly read the instructions and follow precisely the process as the ABS can be cut, but not replaced easily.

The first thing was to sand a small chamfer onto the outer edge of the nose ring and lightly sand the (smaller) face to be glued. (I put some hatched pencil lines on the rear face to make sure that I knew the side to be glued at a glance)

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I started with the upper section and cut the cowling out leaving as much excess surface as possible and offered it to the fuselage to check out the fit. To help with this I also fitted the spinner back plate to show where the cowling front face must rest. I shone a bright light up through the cowl to highlight the former (F2) position and lightly marked it on the top cowling.

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The rear of the top section could then be cut closer to the line so to get a better fit. I repeated the exercise with the lower cowling section, but this time marked the relative positions only. I found that I got a slightly better fit by sanding the bottom section of F2 so that it matched the angle of the cowling. I cut the wing cutout only roughly and left it like that ready for when the wing is to be fitted.

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Next I taped the top cowling in position and assembled the bottom cowling to the fuselage to make sure that there was a good overlap at the sides, and a good fit at the front such that the front is circular and conforms to the spinner back plate. I then marked the overlap points and relative cut lines on the top section (Which are moulded in place). The top section was then cut to the final shape and the fit of the bottom section verified before cutting to match. REMEMBER.... CHECK TWICE, CUT ONCE!!!sdc10114 (copy).jpg

With all the parts fitting correctly the nose ring is glued into the front of either section, followed by one of the ABS reinforcement strips each side for the full length making sure that the strip is only glued half depth so that it forms a key for the joining to the remaining section.

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Befor the final joining I found it useful to use the end of a steel ruler to pull away any surplus glue so that the cowling join line is as sharp and neat as possible. When the two parets are joined use clothing pegs or small clamps and adhesive tape to keep the parts in close contact until the glue has set

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Adrian

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I then cut away the side of F1 and F2 to allow the extra joining strip to fit without causing the cowling to bulge, checking the fit of the cowling at all times with the spinner backplate in position.

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I then used a pencil to highlight the battery access panel on the cowling and then carefully cut it out using a razor saw taking great care not to have the cuts overshoot at the corners.

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I used some of the surplus reinforcement strips to form a seat at the front and rear of the cowling and to reinforce the ABS at the corners (I also used some of the spare ABS backing to make an extra long strip for the rear seating). I used two smaller strips at the front with a gap of around 12mm (1/2" for a locating tongue.

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The battery cover panel was then offered into position and the position of the front and rear strips were marked on to the inside surface.

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Two strips were then affixed to the inner sides being cut to fit between the front and rear the cowling seats. A small section of strip was also affixed to the front of the cover to form the locating tongue. A decision will be made later in the build whether to use a magnet or screw to fix the cover into position.

Adrian

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I decided to use Two 6mm x 1.7mm button magnets for the hatch retention and this is my solution:
First the cover was marked with the position of the front and rear seating strips and the 1st magnet position was marked on the centre within the seating strip marked area.

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The seating strip was drilled and opened out to allow the cover magnet to slot into it. The 2nd (cowling) magnet was retained with adhesive in a small piece of 6mm balsa which was itself then stuck to the cowling seating strip so that a good engagement of the magnets was made.

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I scored the back face and sides of each magnet with coarse emery cloth to get a rough surface and glued each in place with medium/ thick CA adhesive.


Adrian

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Fitting the wing to the fuselage is a critical operation as it ensures everything is square to the fuselage and not only will it look right, it will also fly right. The front locating dowel is engaged into the fuselage former and the wing carefully placed in position. It may be necessary to relieve some of the fuselage material to allow the wing to seat, but only the smallest amount required needs to be removed. Check the symmetry of the fuselage/ wing from the front to ensure that the wing is not canted off to one side. and that the tailplane will also be in the same alignment as the wing.
The next step is to attach two equal lengths of thin cord or fishing line from the centre of the lower fuselage at the fin end and ensure that the wing is square to the fuselage in plan view by ensuring that the lines are of equal length to each prominent point on the wing tips ie. the aileron tip at the cut outs[ or the rib positions at the trailing edges. When satisfied with the wing alignment mark the wing centre on the wing and fuselage so that they match.

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I then pinned the wing to the fuselage to immobilise it and screwed a nylon bolt with a tapered end through the wing fixing plate in via the cockpit.

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When the bolt touched the balsa wing it was screwed in a few more turns so that the point marked the wing skin.

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The bolt was then screwed through the remaining captive nut and the wing was removed and the marks were drilled out to 7mm and the wing fit checked again using the wing bolts through the correct side.

Adrian

 

Edited By Ady Hayward on 23/02/2015 10:01:56

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The wing fairings were the next task, with the first operation being the positioning of the fairing/ wing seating. The thin ply sheet is let between the wing and fuselage such that the inside edge is flush with the ply fuselage doubler.

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CA adhesive was run between the ply plate and the fuselage so it stayed stuck in place. The next was to stabilise the plate with one of the four fillet formers provided. This former fits at the trailing edge with the long section running span-wise. 2 pieces of the spare 12mm (1/2" triangular balsa were cut to 150mm length and then a series of cuts were made around 80% through the section some 3mm apart increasing to 10mm at the rear as shown in the photographs. (Ensure that a LEFT and RIGHT section is cut).

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The sections were then bent around the leading edge such that the rear end was some 135mm from the leading edge and then were glued to the fuselage and plywood fairing bases When set these were shaped to give the blending of the fuselage to the wing roots.

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The balsa top covers were offered into position and the forward ends marked so to give the position of the cut-outs for the top sheet. The balsa section is cut down 1.5mm (1/16" so that the top fairing sheet had a decent area to fix to.

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The edges were feathered to give better blending and the sections were glued in place and allowed to set.

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Adrian

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Hi Folks.

Progress is still going on. The following process takes a lot less time to do than explain so here goes:

The rear wing fairing started with the fixing of the 2nd wing fillet support being attached rearwards of the first so that it will support the leading edge of the rear fillet section. I marked a line (From the drawings) at the rear point of the fairing some 15mm upwards and parallel to the fuselage sheet line.

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The upper fairing sheet had the top and bottom edges feathered and then was offered into position where a line was drawn to mark the position of the top edge. PVA adhesive was applied to the top edge and leading edge and then stuck in position until set.

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The lower sheet section was then glued to the underside of the fairing, fuselage and edge of the ply fairing base.

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Adrian

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Hi David,

Congratulations on your purchase. I'm sure you will not be disappointed with it and many thanks for the kind comments. The motor mount is the only major difference between the Lekkie and IC versions so the build blog will still be very viable. Please add your build to this blog if you would like to contribute. The more ideas and infos the better.

Adrian

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Examining the box contents everything looks good. I bought the electric retracts and epoxy cowl too, bit more robust for the four stroke. Won't be building it anytime soon though - too much on the production line at the moment, finishing a couple of Atoms, then back to the Chipmunk to finish that, then a funfighter for Greenacres, then maybe the Spitfire. I just bagged a kit while they were available.

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Hi again,

I'm still plodding on with things. I chose to spend a little time filling and sanding and addition of the rear control surfaces. I managed to carefully open one of the bends on the elevator joiners supplied and fitted a short length of tubing to act as a simple bearing. The joiner was bent back into close to the original shape and checked thoroughly for any signs of stress which thankfully there were none. In hindsight there was very little to gain with this exercise. The joiner was offered to the rear of the tailplane and the void to the rear of the fuselage was filled with soft balsa ensuring that the elevator joiner was securely positioned along the centre of the tailplane and was free to rotate.

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Each of the elevators and then the rudder were sanded to shape. The elevators each had a slot made in the leading edges and holes drilled into the control surface to accept the elevator joiner.

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When satisfied with the fit each elevator was offered to the fuselage and the root was sanded so that it allowed the elevator to fit to the tailplane and align with the end of the fuselage as seen in the photographs. A small piece of soft balsa was then cut to shape and was glued in place to match the elevator root each side. (In the shadow)

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The rudder was simply sanded to the desired shape and set aside for covering etc the elevators were also set aside ready for the covering process.

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The wing/ fuselage join was next and again I digressed slightly from the build instructions in that I instead of using the trailing edge stock for reinforcing the point where the wing bolt heads bear onto the wing I used some liteply instead. I cut two pieces of ply around 20mm x 25mm and drilled the bolt fixing hole to suit so that the ply was supporting the wing and spreading the load, but also fitting just inside the fuselage line.

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Pieces of soft balsa were used to fair in the area forwards of the wing trailing edge and sanded so to follow the rear fuselage line and blend into the wing underside.

 

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A similar task was carried out at the wing leading edge.

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Adrian

Edited By Ady Hayward on 02/03/2015 23:59:41

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Hi Folks.

Nothing much to show at the moment. I have given everything two coats of Water Based PolyUrethane (WBPU) rubbing it down after each. Weight gain was minimal but all surfaces to be covered have a very smooth surface to attach to. The wings will be covered in 25g/ sq metre glass cloth and the fuselage and control surfaces will be covered with 18g glass cloth. Pics will follow when I cover the relevant parts.

Adrian

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Now the fun bits......
The Spitfire has fabric covered control surfaces all round the tail end and metal covered ailerons. The metal skinning needs nothing more than a smooth finish to replicate the metal surface, but the fabric covering shows the internal structure to some extent. The method that I have found works well is to use thin strips of masking tape which are placed in the corresponding position of the structure.

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The result is that when the covering is in place there is a little sag between the ribs.

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The trim tabs are picked out by scoring the surface before and after the covering is applied so to highlight them.

I have covered the control surfaces with 18gsm glass fibre cloth to keep the weight down and also to give the tail feathers a more satisfactory appearance of cloth over frames as opposed to the ailerons which are all metal.
The glass cloth was cut about 15mm oversize all round and I started with the undersides.

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I laid one of the cut glass cloth over each of the control surfaces in turn which were then given a coat of WBPU working from the centre outwards making sure that there were no bubbles, creases or wrinkles visible. When the surfaces were dry I then gently sanded off the excess glass cloth and repeated the process on the top surface making sure that the surplus cloth was on the underside where it can be sanded back and blended in with the surface.

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Adrian

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Must try to remember the masking tape when I get to my build, next winter! I could almost do with a print out of this post to supplement the Warbirds instructions and plan, shows what a good job you are doing Adrian keeping us so up to date and informed. 👍

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Hi Tony, Steve.

I cannot recall where the idea came from but it has worked well for me on a few models that were balsa, foam and depron builds. It is simple to do, the only drawback is working with thin strips that want to curl up but with a little perseverance all ends well.

Steve. I usually copy the blog page and paste into a Word document. This works well enough to have a hard copy of anything submitted. I'm glad the blog is of use and just wish more modellers could try a balsa build and post their experiences. It all goes to help people over the hurdles that go with building an aeroplane.

Adrian

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Hi Geoff,

Many thanks for your kind comments.. The masking tape is only single layer I find that the definition and sag is sufficient to give the effect of structure underneath mainly because the tape allows the wbpu to fill the weave so leaves it glossy and the fabric between still shows the weave. More layers will work but in my view are probably not worth the effort.

Adrian

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