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Slingsby Petrel 3.4 metre designed by Chris Williams


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On 17/06/2022 at 14:26, MikeQ said:

Im terrible for having lots of things on the go at once.  It might take 3 or 4 yrs for a simple model to come off the production line, although there are models coming off two or three times a year if you know what i mean.  Ive got a Loaded Dice 40S pattern model thats about to drop and its been on the go about 15yrs ?.  Freeflight, control line, radio ... i always finish a project, at some point in the nine specific future.  My buddy only ever builds one at a time.  Much more sensible.  Im clearing the decks for this Petrel though..  
 

 

 

I always start with such good intentions.... then I damage a model so there are two on the go..... then a chance for a long lusted after kit comes along and thee are three on the go.... 

 

Currently have a P47, a Valiant, a Tiger Moth (rubber), and a Miniplane on the go. Plus about a dozen others that need some tlc. And I need my Ultrastick to jump the queue so I can fly it on Tuesday!

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On 18/06/2022 at 15:40, Peter Garsden said:

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More error remedying - had to insert the 3mm ply backing for the front wing attaching hook and the front of R2. Notice the lip I glued onto the sheeting to facilitate the join correctly. This is like doing a repair after a crash!

 

I don't think I have ever built a model without some mistakes.  Usually, they end up hidden and nobody knows..... except me......

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Re Covering Material. I am going to follow Chris's recommendation in the same way as the Flamingo ie Film on the wings - a pattern of red and white with clear to show off the rib open structure. I still have some Hobbyking Clear Matt which goes on very easily. Same for the Talplane. The Fin will be a mix of red and white and clear film again for the open structure. Fuselage will be covered in Oratex then sprayed a red and white pattern yet to be decided. I will be using my Iwata Airbrush which is fab.

 

Re building pattern. I am afraid I am a completer finisher I am afraid, apart from repairs and maintenance which I usually slip in, in between builds. Once I start, I go at it hell for leather until I finish. When we do Mass PSSA Builds, I am usually first to finish.

Edited by Peter Garsden
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Hi

 

I recently bought an Iwata Eclipse HP-BCS.  Its the siphon feed one. Going to use it on the Canberra with decanted Tamiya AS rattle can SEAsia colours topped off with a coat of matt 2K clear.

 

A bit on the small side for the Petrel.  Probably use the old ‘Harbour Freight’ touch up gun for that.

 

Looking good.  Great progress.

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Ailerons are very light and are built up over the plan. With the laser cut bits this is a speedy process once the leading and trailing edges are cut and laminated. The leading edge cleverly is angled away from the bottom of the trailing edge to avoid having to chamfer it. It has to be sanded at an angle before it is laid down.

 

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5 hours ago, MikeQ said:

Hi

 

I recently bought an Iwata Eclipse HP-BCS.  Its the siphon feed one. Going to use it on the Canberra with decanted Tamiya AS rattle can SEAsia colours topped off with a coat of matt 2K clear.

 

A bit on the small side for the Petrel.  Probably use the old ‘Harbour Freight’ touch up gun for that.

 

Looking good.  Great progress.

I have the Iwata HP-TH which is a cross between an airgun with the two holed side feed spray and an airbrush with a 0.5mm nozzle. Not much good for very small scale but ideal for large areas which is what I wanted it for, so you can and I did spray the whole fuselage with it.

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Not the best photo of underneath the wing where the spoiler servo will sit on these rails.

 

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Emax servo glued to a 1.5mm ply plate with a mix of Finishing Resin and Microballoons to make it easier to remove in the future. Arm in situ for one way downward (to produce up spoiler) movement.

 

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The spoiler has to be positioned 10mm out from the leading edge so that when the servo swings down it will go vertical in an arc. This is the end of a large Futaba Standard Servo I am using for the elevator and rudder with just the top hole exposed and the rest buried in a slot. Clevis will clip onto it. The pivot of the servo screw has to be in line with the hinge line of the spoiler.

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This shows the operation of the spoiler in a vertical position with a plastic clevis on one end (chosen because of its short length) and ball joint on the other (just out of sight)

 

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View showing the servo screwed down on bearers again with the spoiler vertical. Open is at 90 degrees, and closed at zero degrees with the servo arm in line with the servo.

 

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So - this is what should have happened with the port wing but didn't ie gluing in the subspars (top and bottom) BEFORE the top and bottom sheeting

 

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This spar needed quite a bit of clamping to get it to attach properly, probably hadn't prepared the notches cleanly enough. In the picture above you can see the I Beam configuration with the webbing forming the middle section to tie the top and bottom together and give the wing strength.

 

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Edited by Peter Garsden
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On 27/06/2022 at 22:38, MikeQ said:

What wing joiner are you using Peter?

 

Cheers

 

mike

 

 

I'm using the joiner recommended in the plan simply because I have some left over from the Flamingo Plan ie flat steel rods on their ends measuring 12mm x 2mm (I think). They fit into oblong brass tubes which are glued into a slot between the wing spares, which in its turn is glued into a 3mm ply surround between the wing spars. It holds the wing at the correct dihedral.

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Well nearly finished the starboard wing. I haven't posted anything because it is the same as the port wing, but this time without errors or course.

 

I made a slight error with the port aileron when building it up. I did not rest a straight edge against it when gluing in the ribs. The result was a bit of a banana, but it is no matter because the hinges will pull it into shape, only a few millimetre out. So this time I made sure I rested a straight edge - piece of angle iron against it.

 

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The trailing edge goes down first. It is longer than a standard 36 inch length so has to be joined. I found the spruce almost impossible to cut straight as the knife tends to follow the grain which weaves. One is not given already cut pieces of 12mm x 1.5mm strips but a sheet of 1.5mm spruce from which to cut ones own. On top of that goes a piece of 6mm x 3mm balsa which is later sanded down t nothing to form the trailing edge. Clever - laminated and light but strong.

 

Then the tip and root ribs are glued in followed by the leading edge made straight with the straight edge and the ribs in between added. One can see that the leading edge attaches at an angle. This means that the bottom has to be sanded at the same angle so it rests flat on the plan. This is also clever in that the gap at the bottom of the top hinged aileron is automatically formed without a lot of sanding back.

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  • 2 weeks later...

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So on with the fuselage. All the formers are made from beech ply apart from the front formers F1 to F3 which are temporary and are removed when the fuselage is formed. One makes half over the plan then the other half is joined with the fuselage off the bench.

 

Word to the wise, make sure the 6mm squre and the spruce fits the slots before you glue into place. I used cyano. It is difficult to make it fit in situ without breaking the joint. Note the use of engjneers squres to ensure the formers are vertical.

 

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One can see the 6mm square added. It has to be bent towards the nose using steam as does the 6mm x 3mm spruce which forms the edge of the cockpit. Also the 3mm square spruce is added from F4 to F7.

 

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Also one needs to file grooves in F5 to take the joining pieces of 1/16th ply to act as glue surface areas for the fuselage sheetingg - 1/32" ply. These are the tools I used to open out the grooves in the formers and to create grooves for gluing area pieces - Permagrit.

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Erratum above - only formers F2 and F3 are temporary and will, at some future stage, be removed. F1 Remains and must, of course, form the front of the fuselage.

 

Anyway onward. 

 

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So, 1.5mm plywood sheeting to the front outside of the fuselage. Chris says use PVA. I used a combination of aliphatic for the joints that will remain, and cyano for the joints with F2 and F3 which will be removed later. This also has the advantage of securing the curved bits of planking that are very difficult to clamp down albeit Chris recommends a combination of pegs and masking tape.

 

I used steam to bend the sheet into the curve formed by the front of the fuselage, which helped a lot. Ply bends easily in steam - I bought a pair or marigolds especially....saves burns to the hands.

 

One must add pieces of 6mm to the top and bottom keel - already in place in the picture, so as to enlarge the gluing area - one side of F4, F11 and F13 to the rear fuselage where the ply joins are. I used the cut out in the ply sheet and drew round it.

 

The piece you can see has no score marks in it as the other planks do - see below - but has to narrow to the front from F3 onwards. I measured the circumference of F5 and compared it with F1. I then used the same fraction of 8/11's to work out that my planks, which are 20mm at F5 have to narrow down to 15mm. I tapered it off only at the top which seemed to work.

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These are the remainder of the 1/16th ply planks duly steamed to shape and cut down to 15mm at the front from 20mm at the rear. Chris recommends, and I would heartily endorse the suggestion that one cuts wide planks - 20mm in my case then make 2 score marks at equal intervals so as to create a curved shape to hug the formers, again using a mixture of Aliphatic with clamps, and cyano as above.

 

I found that if one encouraged the score marks to crack and bend with square nosed pliers it helps a lot. This picture is taken after I had removed the fuselage half from the plan and removed the pins. One only needs to do 75% of the planking, the remainder being finished off when the other fuselage half is in place.

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And so to the other side of the fuselage. Fortunately I have an ace Robbe fuselage support which my mate Keith bought me for Christmas. It is essential for holding a spherical shaped fuselage still. One just repeats the process on the other half of the fuselage with the formers held in place with cyano due to its quick sticking power. I have also used cyano on F2 and F3 to make them easier to remove later.

 

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One can see the formers butt jointed and glued, but this shot shows how much I steam bent the central 6mm square longeron to follow the shape of the front of the fuselage. Again very important to open out the slots for the longeron in the formers BEFORE gluing up the formers as all the slots need adjusting to make them sit with no overlap, same goes for the length of 3mm square spruce.

 

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This shows that one must add 6mm square pieces to double up the central longeron so as to ease the 1/32" ply fuselage covering later, and also the gluing area over the top of the fuselage - a bit blurred but there is a piece of 6mm square either side of the top and bottom keel, which will need sanding to shape later.

 

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Obviously there is a risk of the fuselage being pulled out of shape when the central longeron is glued in place, so I clamped 2 pieces of softwood to the top and bottom of the fuselage to keep it straight. I am using some waterproof 5 minute to dry PVA which is brilliant and dries clear. You can just see a white blob of it under F4.

 

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Again sorry for the blur but this shows how much one has to steam bend the 6 x 3mm spruce longeron at the front and top of the fuselage. It then sits nice a relaxed with little clamping needed.

 

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And in situ.

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Planking nearly finished both sides. Doesn't matter if there are gaps because the whole surface will be covered with body filler (I am using P38 for both the nose, and the sides. The last piece, however is difficult to form without a paper template. You can just see the pencil rubbings with a 4B soft pencil which follow a crease I make against the surrounding edge. I then cut out the shape with a fret saw.

 

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It also has to be steamed to bend into shape and scored to follow the curve which, over the keel, is quite acute.

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On with the nose - first of all glue in the formers then fill them with body filler - P38 is my choice as it dries quickly

 

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I made some paper templates for the shape of the lead which is screwed to the front former and drilled a 2mm hole for the small wood screw which holds it in place.

 

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What a mess? Well yes but it'll be reet when the Horseshoe Sander has attacked it. The nose P38 in particular was applied in 3 layers. Sadly the bottom layer is still not set as it has too little hardener in it. Not a lot I can do now, but I think it will be OK. The inside formers will of course be removed later, and the filler is great for sealing the gaps left by the plywood planking, which is very difficult to get accurate. I hope I have not put too much lead in the nose as now the c of g is between F3 and F4. Still a tailplane and fin to add so fingers crossed.

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This shoes how you attach the bottom fin rib ie Fin 4 by placing the fin up to the fuselage to get the angle right and protecting the joint from sticking with masking tape, as I am using cyano. The other ribs are attached with the trailing edge on the bench and engineer squares used to ensure they are upright.

 

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You can see that I have penned a middle line on the fin trailing edge to ensure that the fins, and the leading and trailing edge are parallel when viewed from front to back, The RCM&E mentions getting the LE and TE parrallel which I didn't understand at first as from the side they are askew.

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This is the all moving tailplane horn which I cut from 1mm Aluminium and happened to have in stock from offcuts I had cadged from a local works.

 

I photocopied the part from the plan, cut it out, and glued it with Pritt Stick to the metal, then used tin snips to cut the lines. I then drilled the holes with my pillar drill - checking of course the correct diameter from the tubing and wire I had bought from a local internet supplier, Macclesfield Models. Better to have the holes to small than too big because then you will have a sloppy tailplane, something AMT's are famous for.

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