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Black Knights Skyhawk


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Torque Rods

Shaping and fitting torque rods is my pet hate on any model, as so much can go wrong, so I wanted to get this over and done with before any more fuselage work. I used the J.Perkins 12g rods, which work out at approx 2.6mm diameter. I cut the vertical ends to 19mm long, to avoid fouling the wing nut plate F6 in the fuselage.

Normally I would fit dry fit and shape the TE first, then groove it for the tubes, and glue the tube and TE all in one go. However, due to some over zealous sanding my TE is only 1/4" instead of 5/16", so I discarded the thick plastic bushes that came with the rods and used thin brass tube instead. To be sure I fitted the rods centrally with a little space each side to attach the TE, I epoxied the tubes in place first, whilst I could see everything:

1607_1201_torquerodsleft.jpg

I like to file the aileron ends of the rods to a chisel point, to reduce the chance of them breaking through the aileron surface:

1607_1202_torquerodsright.jpg

The major benefit of glueing the tubes without the TE is that I can see that there is no fouling when the wing is fitted to the fuselage:

1607_1203_torquerodsclearance.jpg

 

 

 

Edited By Steve Houghton on 13/07/2016 00:27:59

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Let's Twist Again

For an ideal match to the wing, the ailerons need a twist to match the washout. I would normally cut them from sheet and carve the twist into the TE. However, since my balsa supplier sent 1 1/2" x 1/2" TE stock instead of 1 1/2" x 3/8", I thought I would use this instead, and carve the twist into the excess thickness at the front.

I'll include plenty of detail here, so skip on if it's too boring!

At the aileron root, I aligned the TE stock with the top surface of the wing (left aileron shown). The front is flush with the wing, and the TE aligns with the root TE:

1607_1501_ailroottopaligned.jpg

At the aileron tip I aligned the TE with the ply core in the wing tip, which is already aligned with the wing profile and washout. The front is left to adopt its own natural position, with some excess above and below the wing:

1607_1502_ailtipaligned.jpg

The red line now shows how much must be planed off the top of the aileron tip, which stands proud of the top of the wing:

1607_1503_ailtopexcess.jpg

This shows how much must be planed off the bottom of the root end of the aileron, which stands proud underneath the wing:

1607_1504_ailbottomexcess.jpg

A little must also be removed from the underside of the aileron tip:

1607_1505_ailbottomtipexcess.jpg

Removing the aileron from the wing shows the extent of the excess to be removed, and the twist is now apparent (noting that the TE will remain straight with no carving). The torque rod slot can be seen to the left:

1607_1506_ailfrontmarked.jpg

Extending the lines around the ends of the aileron shows the tip shape required:

1607_1507_ailtipmarked.jpg

... and the root shape next to the torque rod. The top of the aileron is to the left, which will be flush with the top surface of the wing:

1607_1508_ailrootmarked.jpg

No wood will be removed from the TE, which is kept as the straight reference edge. A happy half hour with razor plane and sanding block produces a perfectly contoured aileron:

1607_1509_ailfitted.jpg

The carved-in twist is now clearly seen. The TE looks bent, but this is an optical illusion, as it is perfectly straight:

1607_1510_ailfittedtwist.jpg

The next job will be to carve the tips to profile, but that will have to wait until after Cosford tomorrow - I hope the weather won't be as wet as the forecast.

 

 

Edited By Steve Houghton on 16/07/2016 00:42:53

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Wing Tip Alignment

My method for aligning the wing tip blocks was as follows:

I used the ply core as the reference line that was to run through the tip between the extremes of the LE and TE. I first drew the centre line along the tip rib and projected it round onto the TE and LE. I marked the position of the TE onto the tip (vertical red line) and glued it into place so that the ply core aligned with the centre lines at the TE.....

1607_1701_tipcorete.jpg

..and at the LE:

1607_1702_tipcorele.jpg

I used a straight edge from the outer end of the root trailing edge to the ply core of the tip block, to check that the tip was vertically aligned to follow the trailing edge of the aileron. The aileron should follow this line:

1607_1703_tipcorelevelling.jpg

OK, slightly droopy, but it's near enough for me!!!

1607_1704_tipcorelevelling.jpg

The fixed part of the TE stock at the root does not follow the true line of the TE washout, because that would have been a little too fussy to tackle.

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Love all those detail pics, Steve. Much appreciated here at the Douglas Aircraft PSS Rehabilitation Facility, Boston Campus.  The pics really help me as thus far my build keeps showing me in excruciating detail just how flippin' RUSTY I am at all these traditional model-building elements!   it is great to be back in the fray, but wow the learning curve just gets more and more fun.  Or flammable, depending on what time one checks in with me here at the House of Corrections, Douglas PSS Aircraft Division.

Edited By John_Rood on 18/07/2016 16:05:39

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Thanks John. I don't intend posting too many details, except in areas where there might be different approaches. I suspect the current level of detail will tail off as building time runs out!

I, too, had a long lay off from building, until Mr Cooke tempted me back with the first mass build of the Jet Provost. I'm still not a fast builder, but I am enjoying re-finding those building skills.

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How did I miss this great blog with lots of good detail Steve.

Am now going to follow.

Disappointed you didn't try a lost foam version Steve???

Tip for people looking for tips. DON'T USE SUPER PHATIC GLUE to attach the top sheeting as I did. Doesn't stick well enough. Use Aliphatic which is so much better. I have ended up with raised humps on one wing where the sheet didn't stick properly in parts.

Hope the judges won't notice - they don't read these obviously do they Phil??

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Hi Pete,

Good to have you along, but its a little too late after you pipped us all to it with your successful maiden - glad it went well for you.

I did use Super Phatic for the front portion of the bottom sheet, and it seemed to work alright, although the ribs were already touching, so that the glue could just wick into the joints. Apart from that little 'modernity' it has been traditional Aliphatic all the way for me.

Aren't the raised humps on your wing designed as turbulators to encourage laminar flow and enhance the lifting performance? When you're soaring above us all in September, we shall know why!

The lost foam is awaiting the F-4U Corsair, after the A-4 and the Zlin 526 have vacated the building board.

No progress this week, I'm afraid. Life's just too demanding at times.

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I, too, used Super'Phatic to attach the upper skin, and I ran into some diffculty on my first panel, in just getting the surfaces to "set" properly without a lot of fuss, and then later, after things had pretty much cured on that panel, there was a spot or two where a rib didn't fully attach as it shoulda -- oh that dreaded popping sound! Not the end of the world but still a bit more fuss than necessary to apply, correct it, and then move on.

Never wanting to learn from my screw-ups, I used the same glue on the other panel -- but this time I took a lot more care by segmenting the gluing into stages, i.e., starting in one corner, nailing it down good and sure, and then gradually working outward. Worked fine. But I agree, Super'Phatic ain't ideal for attaching the upper wing skin.

Edited By John_Rood on 21/07/2016 03:53:35

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  • 1 month later...

Still Here!

After a very wet camping holiday in Cornwall, I have now managed to dry out the tent, family, and dog, and returned to the build.

Wedges

The front of the air intakes have been assembled and shaped. I decided to add wedges to the inside top faces before fitting to the fuselage, so that I could get a good fit:

1608_2001_airintakewedges.jpg

The wedges assumed a very complex 3-D curvature that needed sanding diagnonally to get the basic fit, and then thinning on the inside edges to fit the curvature of the fuselage:

1608_2002_airintakewedges.jpg

Fairing Up

Not the weather - that'll never improve this Summer. I used the laser cut wing bolt reinforcement plate, but found, like others, that the hole was too big. I'm too stingy to waste a good piece of wood, so I just turned it round, drilled a new hole and filled in the old one:

1608_2005_bolthole.jpg

I hate making front wing fairings, they are so difficult to shape. I made this one in two halves, one for each side of the wing, which makes it less hard to shape to fit the curvature. Then joined in the middle and stuck behind the front plate:

1608_2006_wingfairings.jpg

I extended the front lite-ply plate so that it covered the whole of the front fairing, giving a hard surface against which to insert the balsa block, and to give more resilience against the fuselage:

1608_2007_frontfairing.jpg

Wooooooo....ooooh!

This spooky shot shows what happens when you follow Phil's intructions in the magazine to plane plenty off the fuselage corners. I don't think he meant it this literally! The corners between F5 and F7 ended up paper thin. That will be a real weight saving, but rather weak:

1608_2010_fuselagetoothin.jpg

To recover the problem (which at least one other blogger also suffered), I applied glass fibre tissue stuck with PVA over the corners along the triangular sections behind F5. It's not very clear, but the yellow PVA is just visible. This should hold it all together for a while:

1608_2011_fuselagereinforcing.jpg

What Else?

The fuselage is now fully sanded, and the tail section made but not assembled. More photos may follow, but I'm concentrating on building rather than blogging. If all goes to plan, I shall cover the wing this weekend, to give me confidence that I'm progressing quickly enough to meet the deadline.

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Elevator Horn

Another fiddly bit, which took me over two hours last night. Assembled with 24-hour Araldite for strength:

1608_2601_elevatorhorn.jpg

Tail Pipe

I used the cap off a 'So Him' spray deodorant (had it in stock for many years!) - just over 44m diameter. If there's time, I want to fair it into the fuselage better, so that there is no step and it looks more scale-like:

1608_2602_tailpipe.jpg

I'll show you mine

Everyone else has shown us their rudders, so here is mine. Made to Phil's recipe 1/8 + 1/8 + 1/8 with 1/8 riblets. I have engraved the rudder hinge line for better effect, and hope I can push the covering film into the indentation.

1608_2603_rudderfluting.jpg

Dry Bones

To reinforce my confidence that it will be ready in time, here are some dry assembly shots.

1608_2604_dryassembled.jpg

They would look better outside, but I want to use the daylight for further sanding and shaping over the weekend.

1608_2605_dryassembled.jpg

The wing hasn't been sanded yet, so the tips look especially rough:

1608_2606_dryassembled.jpg

Intakes

Being derived from the A-4C, the A-4SU has shorter air intakes than the A-4E, with more upright fronts. I just shortened the laser cut parts accordingly. These are tack glued for now, so that I can cover them in film before final attachment. I spent a lot of time trying to get the two intakes the same length from all viewing angles, and keep thinking they are still not right - don't look too closely:

1608_2607_intakesanded.jpg

The aforementioned wedges can be clearly seen at the top of each intake:

1608_2608_intakesanded.jpg

I hope everyone else is further on than me, or has plenty of spare time over the next two weeks! Mine will be tight, as it was with the Jet Provost, but I'm determined to be in bed the night before the event earlier than the 3.30 a.m. I managed for the last mass build.

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Hi Pete,

I find that as my children get older, and go to bed later, so my modelling time drifts later into the evening (and early hours). I think you were very wise to get yours finished so early, to relieve the last minute pressures.

Thinking aloud, I was pondering whether the next mass build should be for completion early in the year, as for the first Jet Provost build. That way, there will be less conflict with family time during school holidays and we can use the dreary winter months to sweat over the work benches (I know the solution was to start earlier, but I never manage it) - possible topic for discussion at the Orme as we all await our turn for a quiet slot to launch into the masses of Skyhawks.

Progress

However, after a 2 a.m. finish on Sunday night I now have a covered wing - pictures in due course. Phil was right, it wasn't too bad. Just need tailplane alignment, cockpit fitting, remaining covering and radio installation and the Black Knight will be set to go.

 

Edited By Steve Houghton on 30/08/2016 12:44:18

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Wheel Fairings

Like Mark Kettle, I also built up the wheel fairings, but made them off the model:

1608_2701_wheelfairings.jpg

The sides are 1/4" sheet, top (or bottom) is 1/8" sheet, with solid block tip and tail, plus some TE stock to fill in the corners to absorb the underside curvature. These weighed 11g each after sanding:

1608_2702_wheelfairings.jpg

Tail Group

I film covered the fin, rudder and tailplane before assembly. However, I chose to glue the tailplane to the fin before fitting the top and bottom 1/8" tailplane supports. By doing it this way, I found it easy to jig everything at right angles, using a couple of squares held in place by a clamp:

1609_0301_tailalignment.jpg

Like others, I did manage to film cover the ribbed rudder, but it was a tedious process, and the finish is far from smooth. However, a reasonably realistic effect has been achieved:

1609_0302_tailalignment.jpg

Mind the (wider) gap

I felt that the gap between the two lower tailplane supports was a little restrictive, so I added a strip of 1/32" balsa to each one before gluing onto the fin. This will give 1/16" more clearance for the elevator horn and pushrod, and they were later covered in film:

1609_0303_tailsupports.jpg

 

 

 

Edited By Steve Houghton on 04/09/2016 22:54:11

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Putting it all Together

All the flying surfaces have now been covered. Here are a few taster shots of the progress so far:

1609_0401_wingtailcoveredtop.jpg

1609_0402_wingtailcoveredtop.jpg

1609_0403_wingtailcoveredtop.jpg

The underside has some striking contrast black stripes. The main problem here was carrying the stripes over the wheel fairings, and keeping it all straight:

1609_0405_wingtailcoveredlower.jpg

1609_0406_wingtailcoveredlower.jpg

Tail Padding

I thought that the tail pipe needed blending into the fuselage a little more, for a better scale effect, so I added an extra ring of 1/4" balsa around it. This is nowhere near as smooth as the blend on the full size, but does get rid of the abrupt step:

1609_0404_wingtailcoveredpipe.jpg

Running very short of time now, so I'm afraid the updates are becoming rather brief.

Back to the bench......

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