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Phil's F-86 Sabre build thread


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yeah gluing the fin on with the thinner front fairing and then adding that pesky fillet is a job for me to do once the wing seat is all sorted, I need to be able to fit the wing in my cradle with the fus upside down and this is imposs with the fin attached.

Every job has its place! wink I am surprised you are daunted by the painting Dirk - I thought thats where you lead the field!!??

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Good to get the workshop all dusted down and tidied enough to set up for some glassing. Other than the dullness of my best scissors - making the cutting of the cloth panels to size a little difficult - all went well and the new Jenny brushes courtesy of Amazon were great!

I've tackled one side of the rudder, the underside of the ailerons and taiplanes, and then the wing underside on a second mix of resin.

Panels are cut to size with a good inch of overhang all round. I'm using the 25g/m2 cloth from Fighteraces, and their Epoxy resins - the same bottles I did the A-4 and Hurricane MBs with in 2016 and 2018! It keeps well.

glassing wings 1.jpg

glassing wings 2.jpg

I think Dirk's foam roller method might be easier on the bigger panels. I stipple all over with the 1" brush then drag out the excess resin to the edges with an old credit card - aiming for a single coat - no flow coat if I can avoid it.

glassing wings 3.jpg

Not too little, not too much... that's the trick to glassing - lets see what this looks like in the morning. Time for a beer.

glassing wings 4.jpg

beer

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Some more work on the droptanks over the past couple of evenings - getting the foam and balsa assemblies ready for paint. I was undecided whether brown paper and PVA was better than 2 layers of glass cloth and resin. In the end I wasn't happy enough with the surface finish where the blue foam meets the balsa and I went with the thicker of the coverings to better bridge the minor sins!

I was keen to try and minimise the number of brown paper patches, so some time creating the required 'net' was spent before applying any water and PVA. This took a couple of attempts to get right as the rate of change of curvature and reduction in circumference as you move fore and aft wasn't quite taken into account correctly on my first attempt... leaving small gaps in places.

So this first net was a fail... crying

tank net 1.jpg

tank net 3.jpg

The second net had less material removed at the nose and tail and longer axial slits between the fingers... this fitted much better. In addition, I made some additional panels to sit onto the flatter top side and around the pylon - these bits would be added first before the main body panel.

tank net 4.jpg

The night before I'd painted the entire assembly with undiluted PVA, this was left to dry and the raised 'nobbles' were sanded back gently before the paper was added. First, the 4 top panels around the pylon...

tank net 5.jpg

Once dry, the paper edges were feathered as best I could before the rest of the net was added.

tank net 6.jpg

Once positioned correctly around F3 and F4, the fingers were pasted down one by one with a watered down PVA mix - like pouring cream. Each finger overlaps the last just be a few mm.

First the nose...

tank net 7.jpg

and then the tail - all done.

tank net 8.jpg

Once all dry, the paper overlaps will be feathered back again which should result in a surface fit for primer. The tips of the nose and tail will get a couple of coats of epoxy resin - the rads are too tight for the paper without creasing and wrinkles!

I've not weighed them yet as they are still 'damp' - and as the PVA dries the weight reduces! laugh

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A little work on the wing seat and front dowel mount this afternoon...

Following the lead of Steve McLaren and Harry Twist I've elected to 'overcut' the fuselage sides away by a few mm to enable the wing to sit securely onto the ply formers which govern effectively govern the incidence.

wing seat 1.jpg

I've dropped the fuselage sides by ~1/8" beyond the 2 ply guides - more than allowing for the dihedral effect. This gap will be built back up as you would a fillet from the wings top surface once its all dowelled and bolted down securely.

wing seat 2.jpg

Despite me leaving a few planks off the underside of the nose, there was not quite enough room for my fingers to mark up the wing for the dowels as intended - this required a remote marker making up with a short pencil - short enough to allow it to 'orbit' and accurately trace the hole once inside the fuselage.

wing seat 3.jpg

Easy enough to scribe the circular mark through the location former in this way... the right tool for every job - even if you have to make it yourself!

wing seat 4.jpg

Success! - the 2 location dowels were epoxied into the wing and left to dry in position... now onto the wing bolts and the ply load spreader at the back.

wing seat 5.jpg

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Yeah the join is a little tricky Chris, and I've not finished yet! The weird thing is - as Dirk also explained - the dihedral is positive for the majority of the chord but as the rib thicknesses become greater towards the root it actually drops away like anhedral forward of the max thickness posiiton. Its a complex interface! Overcutting helps align the wing securely onto the ply incidence formers in the fus, but it then needs building back up with a little fillet adding at the front and rear.

I got the wing bolts, load spreader and belly pan sorted today - good to see it with the wing bolted on for the first time!

I marked the position for the wing bolt holes accurately with the old 'sharpened nylon bolt' trick.

wing bolt 1.jpg

I then added a 1/8" light-ply load spreader - I extended this forward to ensure it mated and bridged securely onto the main wing panel instead of just the T/E stock. I sanded it to section as best I could before it was epoxied onto the wing.

wing bolt 2.jpg

wing bolt 3.jpg

Note it's still not quite as deep as the fus in the middle, so will need a little balsa skin to blend at the back. Less material is needed at the front.

wing bolt 4.jpg

I then added a 1/8" balsa belly pan made in two halves to aid the compound bending required. This is too deep for the fus blend at the front and will need shaping. My belly pan tapers very slightly in width - 100mm wide at the rear and 92mm at the front. I'll add the 1/16th balsa along the centre from the rear to about half chord, it all then needs blending in to the fuselage profile. Hopefully not too much sanding needed before this can be glassed.

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The sun was out so it was a good chance to rig the model in full to take stock of my position... still a number of jobs to do all over, only the tailplanes, rudder and drop tanks are finished and ready for paint - but nice to bring all the bits together and have a general walk around.

rigged shot 1.jpg

rigged shot 2.jpg

Hmm, not sure my drop tanks sit at quite the right angle they should be a bit more nose down IMO...not easy to change now.

rigged shot 3.jpg

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That's the difference between you and me you see Phil. Tanks look perfect to me says the man who just about knows the difference between Spitfires and Hurricanes. As Ivan keeps telling me "you won't know the difference when it is flying past at top speed." Wings look a lovely tight fit. You won't need filler fairing pieces like I did. Mind you I am on with my Jart and finished a month ago.

Was flying yesterday at the Mermaid but social distancing makes launching other people's models difficult.

What say we all to this? Is it allowed if one wears gloves?

Edited By Peter Garsden on 18/05/2020 15:32:13

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Yeah they do look massive in the profile shot, I think its just an optical illusion - the photo was taken with an i-phone and I was close to the wingtip - which is why the tip looks like it goes as far back as the tailplane - the tanks appear bigger than they really are!

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Belly pan all sanded to profile and shaped front and back to blend into the fus.

belly pan 1.jpg

The belly pan gets very thin towards the front where 1/8" balsa was more than required with the excess sanded away. The nylon bolts go through the additional thin balsa veneer needed at the back and torque down onto the ply. Just a smudge of filler required and its ready for glass!

belly pan 2.jpg

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With the wing location all complete I could finally close up the fuselage and complete the planking around the lower waist!

planking ends.jpg

I've also filler primed and then sanded back the drop tanks - needs another coat and another sand before the final primer. The pylons are masked off as they still need to be glassed.

drop tanks paint 1.jpg

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Just wanted to credit Phil at Fighteraces for some 'ace' service.

Running fast out of skinning resin, and with the fuselage, fin and pylons still to glass, I placed an order yesterday afternoon at 1pm. Phil emailed me within the hour to say the package would be boxed and shipped that afternoon, and this was with me before 9am this morning! Awesome job!

resin.jpg

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Some work finishing off the wing saddle today.

The method of matching the fuselage to the wing with its complex dihedral and anhedral shaped zones was pinched from the learning gained in the build blogs of Harry Twist, Dirk Tinck and Steve McLaren. Good stuff gents!

So having just overcut the fus sides to ensure the bolted wing is sat onto the inner ply formers - which act as incidence guides - the gaps had to be evened up and opened up to allow some 1/16" balsa to be glued in whilst sat on the wing and clamped.

At the start the wing gap was just big enough to get a course grit paper in. With that cleaned up and free to move along the entire chord front to back I glued the paper to some 1/64 ply, creating effectively an abrasive feeler gauge.

wing blend 1.jpg

That was then used to open up the gap a little more, incrementally - each time it became fully free along the chord I added another shim of 1/64" ply to the bottom of the tool, until eventually I could get 1/16th balsa in the gap smoothly all the way along.

wing blend 2.jpg

The top wing skin was taped to ensure I didnt glue the wing to the fus in the next step. I made up some 1/16th balsa caps which with the wing off again were glued onto the base of the fuselage side and up against the ply formers using PVA. Whilst the glue was still wet I carefully added the wing and bolted it up - pinching the balsa caps at the required angle. I've left them over size to allow for a little 'ooze' - they will be sanded back flush with the fus apart from the last 70mm or so at the T/E which will form the base of the little wing fillet. There is evidently no fillet needed forward of that - the wing apprears to run straight into the fuselage with a sharp angle.

wing blend 3.jpg

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