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Flamingo 3.5metre by Chris Williams - scratch build


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How to form a template for the rear section of the fuselage with a cut out for the fin and tailplane?

First of all I tried cardboard from an office file but found it too stiff. Maybe thinner card might do, but in the end I resorted to paper which is much easier because it bends over the shape easier. Whilst it worked with the front ply sheet, the more acute bend at the rear was too sharp.

  1. I ran my fingers over the join with the other ply shroud and made a mark in the paper. Having roughly cut the paper to size and butted the front up against the front ply, I made a mark for the middle to line it up properly.
  2. It is important to pin it in place to stop it moving whilst the remainder of the marks are made.
  3. I shone a torch behind the paper so I could see the structure through it. This helped me mark each side where the join is made with the horizontal spars.
  4. To mark a line for the edge of the tailplane join I used a 4B pencil and rubbed a mark over the join.
  5. Remember to leave an overhang of about 20mm at the rear to grip the fin and provide a shroud for the Rudder Robart hinges.

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I have always used Deluxe Materials Aliphatic before which has a better grab coefficient I think than Titebond. I made the mistake of getting the standard glue which isn't waterproof so bought this instead. I think it probably sets a bit quicker but is not as gloopy. The jury is out at the moment. I probably should have bound the ply onto the fuselage with masking tape as Chris shows in his pictures. I will try and insert it before it dries completely.

Edited By Peter Garsden on 26/10/2020 17:50:35

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Posted by Ron Gray on 24/10/2020 16:00:49:

Horn above elevator, hidden in shroud?

Not a lot to attach to in that the joiner is only 6mm balsa, unless you used 2 piece of wire instead of balsa with a piece of flattened brass tubing Also the fin post would get in the way, so you would have to make a hole in it so as to provide some clearance

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In this photo one can see that the rear upper sheeting has held well. As for Titebond, I like it but one has to put quite a lot into the joint on both service I would suggest and clamping is more important. It does, however sand well. I have filed down the sides to accomodate the tailplane with flat and round files. I tried it in situ and it is level - relief.

The fin has been offered up to the fuselage and it fits. In error I cut too much back but it matters not. One can see the robart hinges and the slots cut into the rudder to accomodate the pivots.

In order to check that the fin is vertical one clamps a ruler to F5 in line and line it up with the fin.

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I have also put together with cyano, the framework for the fin shroud that hides the tailplane bolt head and trims it in line with the tailplane. One then gets a piece of .8mm ply in the cut out parts which has to be steamed and bent round the former.

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This is a bird's eye view of the top of the tailplane support showing the join of the plywood, holes for the plastic bolt and the 2mm carbon positioning rod.

One can also see the ball link into which the control horn rod for the elevator must slide. The whole thing does fit together, just. The important thing is to make the control rod so that it is held in position but is not tight so it can move freely.

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The Fin shroud which hides the head of the bolt, is detachable, and fits over the sides of the fin is a clever design, as i is the whole plane. It is made tight enough to slip over the fin, stay in place and not slide off.

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I had to throw away the first attempt at a shroud because as I was trying to mate it with the leading edge where the curvature is very acute, it cracked and snapped partially leaving a tear. As there is quite a lot of .8mm spare, I made another one by drawing round the original.

This time I took the ply skeleton to the kettle and bent the ply round the former in situ. The glue recommended is cyano so the steam did not dissolve it as it would have done if PVA was used. I got it into position so that gluing it up was easy and involved little stress

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I glued the ply in position with 5 minute epoxy.

I have lined up the fin and epoxied it to the rear of the fuselage. It lines up nicely with the ruler at F5 but the height of the cover has meant that I have had to lift up the fin about 6mm so it will slide on nicely. I have added some balsa at the bottom of the fin, and glued it into position until it dries. I will then trim it to shape.

Edited By Peter Garsden on 28/10/2020 23:08:18

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This shows the rear lower paper template glued with pritt stick spots onto the .8mm ply. They have been outlined by taping them to the fuselage sides and marking the outlines with creases by pressing on them then marking the creases with a 4B Pencil. I have abandoned the cardboard. Works well. Important to keep a right and left with little markings to show the inside and outside.

Before gluing on one has to make the hole or holes for the rudder controls. I am using closed loop as intended by Chris so have purchased some outers from SLEC. At the outlet one creates a slot then glues to the inside some 3mm balsa doublers.

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Next I decided to attach the control horns to the Rudder. Chris advises to use 3mm Multiplex horns which I have never come across before. The plan mentions wooden dowels drilled out to take the threaded horn base. Chris says, however that he now uses carbon tube, so I invested in some 5mm outer, 3mm inner tubing.

I drilled a hole which has to be angled towards the hinge so that the pivot for the closed loop attachments are on the hinge line.

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I will glue the horns in when the covering is on.

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I have seen a blog where the underneath sheeting was wrapped round in one piece which must be incredibly difficult, so acute is the bend in the keel. Clearly the bottom sheeting has to be applied in 2 pieces.

The problem was that although the template was accurate, the bottom edges needed trimming. I suspect it was the way the paper bent round the formers, so I decided to glue the sides first, with clamps and pins. Once dry, I planed the bottom edges back so that they would not overlap, then glued up the bottom edges, and wrapped the whole fuselage in masking tape whilst it dried.

I now like Titebond. Although it is quite thin it does grab quickly and dries faster I think. It also sands well.

I don't know how I am going to clamp the front lower sheets in position yet.

I do think that I will secure the front closed loop tubes near the servo with a balsa support.

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You are right Dirk, it is quite advanced but not impossible for someone with your skills. So far steaming, bending and clamping ply is the trickiest bit. It doesn't help that i have not built a vintage scale glider before because a lot of the techniques are typical. I do find the use of thin spruce laminated with balsa all over interesting - very light but strong.

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This is the closed loop tube support out of 6mm balsa with holes as wide as the servo horn and enough space to house the clevis and closed loop to move through the throws recommended which are 40mm each way. I used cyano to attach the support to the former, and Superphatic to glue the tubes in place once having roughed up the tube with 60 grade wet and dry. I used this water based glue to avoid clogging up the end of the tube with glue and blocking the hole. I tried the wire down the tube and it moves freely. Will leave this until after covering.

Next job is the covering of the front lower sides of the fuselage which I am not looking forward to.

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As always if you are not looking forward to a job, in this case the lower ply fuselage sides, then it is never as bad as you fear.

  1. I made the paper templates as previously by pressing the edges into the paper then rubbing with a 4B pencil
  2. I stuck in spots the templates to the ply with Pritt Stick, and drew round the edges then removed the paper.
  3. I cut out the ply parts and labelled them right and left with an arrow for the front of the fuselage. I adjusted and trimmed to fit.
  4. I sprayed water on both sides, let it soak in, then steamed both sides round in the kettle. This is how they looked

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  5. I decided to go for a dry fitting using rubber bands and pins. The fit was really good

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  6. In fact it was so good that I decided to dry it out with my heat gun, glue up with Titebond and refit again to let it dry. Came out really well

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There are probably clamps with a larger spread I could use, but I just don't have any.

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Kettle indeed - and I had to buy my own large size rubber gloves as the cleaning cupboard only had small! A lot of steaming to do indeed so, and it helps to soak the ply in water and perhaps leave it for a short while first.

When I examined the ply I had put on, the joins without proper clamping were not as good as they should be, so if I was doing this again, I would definitely invest in some clamps like this

The joins in some places were not quite together which meant I had to re-glue and pin since that was the only method I could use. The bottom of the sheet should end either side of the keel which is 6mm wide. On both sides of the keel are some 6mm fill between formers to which the ply sheets should adhere.

Again the sheets were a bit proud of the joins. I planed the ply until the keel appeared. The ply edges end up at an angle and the bottom flat for about 8mm before the curve starts. Some of the ply was not glued to the keel doublers, particularly where the fuselage changes shape slightly near the wheel housing. Arguably it is a 3D shape and one blogger did this sheet in 2 parts.

I realised I would have to press it down and reglue. I chose Superphatic so that it would dry quickly, but cyano and accelerator might have been better. I had to apply a lot of pins.

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One can see a lot of filler here. The reason is that the join between front and back lower sheets of ply is either side of one of the formers. Cleverly the join is staggered. Top join is F12 and lower F11.

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The problem is that there is not enough width on a 3mm former to support both pieces of ply, so the rear sheet has no former support and thus sinks below the outline of F11. I would advise lining the rear of the former with some scrap pieces of 6mm balsa by way of support. As it is I have had to add some 1.5mm balsa shaved down to a feather then filler to smooth the step between front and back.

Edited By Peter Garsden on 03/11/2020 23:19:36

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Next is forming the wheel housing and shrouds. The recommended wheel is slightly narrower than the housings, thus, having drilled out the 3mm hole for the axle, I made some 3mm ply doublers and glued them on the inside then re-drilled the holes. It needs narrowing slightly because the gap is about 4mm.

One then makes some shrouds out of 6mm balsa. The way to do it is to cut it undersize, glue it in position then file it out with a mixture of flat and round files. Here shown is a Permagrit rough round file - ideal.

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One needs to smooth out the joins with filler - I used light filler from Screwfix, also collets for the wheel - whether or not this is correct you must tell me. If not collets what does one use?

Edited By Peter Garsden on 06/11/2020 19:48:23

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Looking at CW's photos it looks like he has soldered an axle to a thin metal plate on one end and probably another plate on the other side with a short length of tube soldered to it. The plate with the socket is screwed to the outside of the wheel side pieces then the plate with the axle is passed through the wheel from the other side, locating the axle in the socket then screw fixing the axle plate. Quite neat!

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Issue - the bottom front keels are made of 4 pieces of 6mm and 2 outer pieces of 1.5mm ply to create the shape. The flat bottom of this construction does not match the curved bottom of the fuselage. I started hollowing out the bottom of the keels with a Permagrit file, then realised that it would probably make it so hollow that there would not be enough depth for the 6mm dowels which are inserted to house the screws for the Aluminium keel coverings.

So I plumped for flattening the bottom of the fuselage as much as possible to give the middle sections something to key to, then use 30 minute epoxy to fill gaps which there are inevitably. The picture shows that the rear keel does not follow the fuselage because the wheel shrouds. You can see that I have inserted a balsa shim.

I have decided to fill the gaps with some balsa scraps then make up the remainder with filler.

With hindsight I wondered if I should have spread the pieces over the curve but this would have compromised the need for a flat surface to take the aluminium cover. I have bought some 1.5mm aluminium strip off Ebay.

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I thought with hindsight that maybe I should have attached the keels after covering, which is what Chris's photos show. Not sure where I have gone wrong with this.

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You can see where I have inserted 1.5mm balsa wedges with aliphatic resin, which I will trim when dry then fill and sand. You can see that I have already added some filler to the top so as to blend in the trailing edge with the bottom of the fuselage - obviously not sanded yet!

Edited By Peter Garsden on 09/11/2020 18:13:44

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Chris shows 6mm dowel recessed into the keel to hold screws which attach the aluminium skids

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I then marked and drilled the holes for the screws and tried to countersink them. I might change for dome headed screws. Also I am going to add a screw at the front. Ideally the metal should be a bit wider, but it is both decorative and protective. I think it will be fine. I bent the front piece to shape.

Obviously it will be removed for painting.

Edited By Peter Garsden on 11/11/2020 07:35:56

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The Canopy - I debated whether to make the canopy at this stage because Chris's photos show it being made after the wing and fairings had been finished. I thought long and could not work out how it might affect things if I didn't make it now - I couldn't think of a disadvantage so ploughed on.

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The photo isn't the best but shows how it is recommended to put 1.5mm ply spacers round the edge of the cockpit then clamp the laminating pieces of 6mm x 3mm spruce to shape.

I debated whether to ease it first with steam but decided not to as the effect of the lamination is the same. I think it would have helped, particularly where the curve is more acute at the front. Oh well. I am sure the canopy front and rear pieces will help.

NB/. Short Pack shortages - only 1 length of 6x3 mm Spruce is supplied by Sarik which is not enough for 4 canopy side pieces. Fortunately I found some birch in my scrap box but beware. Whilst we are on the subject they have not supplied any wing spruce .1.5mm x 12mm spruce trailing edge which I had to source separately.

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BEWARE - error to avoid. When assembling the canopy, I went off the plan, and could not understand why the canopy formers at the front and back were proud of the top of the fuselage ie F5 and F1A. This is because the rails fit in between the formers with a 6mm square gluing area rather than just resting on top of the canopy rails.

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I was going off the plan rather than Chris's photos. I reproduce one here so you can see. He recommends in the blurb some thin piano wire reinforcement quite sensibly. I just couldn't see how I could drill a hole to take it.

I will try to find a way of inserting some wire reinforcement and glue some gussets in the corners of the rear join between F5 and the rails. There is, however reinforcement in the shape of a ply plate at the front upon which rests the instrument panel.

Incidentally I did use some steam to add a bit more bend to the rails as they didn't quite line up at the ends.

Edited By Peter Garsden on 13/11/2020 06:12:07

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You can see in this photo where I went wrong and how I fixed the problem. I used a 1.2mm drill in my pillar drill and managed to drill a hole in the edge of the 3mm ply Canopy Former to take a small piece of piano wire. I did this at each corner. Not as strong as per the plan but strong enough.

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Here you can see the 3mm ply fill in which will take the instrument console, and reinforce the structure. This is not supplied in the short kit. You can also see the extra 3mm liteply gussets I made for the rear corner joins. Belt and braces. One can also see the corner spruce brackets which span the frame corners.

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This shows the instrument console. The base and front former only are provided, though there is a space on the 3mm liteply sheet from which the rear former can, and has been cut. The front console cover will be glued on after painting and dials have been inserted. The top of the console which was steamed to fit is 0.4mm ply.

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