PSS A-10 Thunderbolt II - build blog

[Andy Meade]

Avro Ophelia?

[Phil Cooke]

Pete - A bit off topic for this build thread but to answer the question we are making good progress again with the PSS Hurricane (its no secret!) mass build venture - sadly some of the CAD work we had completed with Traplet was lost in the transfer but we have worked back to a position now with Sarik where very soon the first woodpack will be available for a beta test assembly before we go into production.

We have no committed dates as yet, hence our radio silence on the matter, but we are still hopeful to have this up and running early in the new year - if all goes well and with a following wind the first plan/woodpacks might even be available in time to treat yourself for Christmas 2017...

We'll announce more once dates are committed, but rest assured we are still actively working on this!

Anyway, on with the A-10...

[Phil Cooke]

The front and rear fuselage joining arrangement is now all installed after a few evenings work and some minor fettling!

In an attempt to aid alignment when rigging - as well as helping ensure a robust joint for flight loads, I based it all around a 450mm length of aluminium wing joiner tube housed in a precision phenolic outer, 16mm O/D. This was mounted in a 1/4" ply box and glued firm to the main fuselage wing box assembly in the rear half of the fus.

The phenolic tube is glued square to the ply surround with epoxy...

...and it's then 'potted' in Gorrilla glue.

A 1/4" locking former was cut to sit over the top of the tube support at the rear...

and the whole assembly was epoxied into the rear fuselage - the joiner is keyed through the front bulkhead and secured at the rear with the locking plate. Large ply-to-ply surface areas and a good epoxy/microbead mix created a very strong bond.

1/4" ply locking plate at the rear - shown prior to the epoxy being added.

[Phil Cooke]

The front half of the fuselage was then prepared to accept the joiner, which would again run through a keyed slot in the rear bulkhead and mate with a semi-former mounted further forward through the underside of the nose.

A 1/4" slot was cut into the bottom of the nose section to accept the new support former and on the inside a ply 'floor' was glued in to accept the joiner, again aiming to produce a good surface area for ply-to-ply bonding.

The fuselage was stood upright on its tail and the 2 halves were positioned together to ensure alignment - this is the view inside the fuselage taken with my phone camera - looking forward from the wing bay.

[Phil Cooke]

Before I could glue the joiner into the nose section, I needed to ensure I could saw back through the ply/tube assembly once it was firmly mounted into both fuselage halves. To allow for a saw blades width to pass through the joint, an array of 1/16th balsa spacer pads were epoxied temporarily to the rear fuselage bulkhead.

30 minute epoxy was then applied to the joiner, to the mating area of floor in the nose section and just a small amount on each of the balsa spacer pads, the 2 fuselage halves were then brought together and carefully positioned to ensure correct alignment before it was left to set firm overnight.

[Phil Cooke]

The fuselage was then cut back into 2 halves, the joiner tube and the remains of the balsa pads were sanded back flush on each side of the bulkhead joint - and with the aluminium tube fully inserted into one half, the first 'proper' assembly thankfully proved a well aligned, accurate joint - just some form of anti-rotation pin is needed at the top of the formers to ensure accurate, repeatable assembly.

With the fuselage halves joined, they need retaining and following the lead of classic designs like Matt Jones' Canberra and Simon Cocker's Antonov 225 I planned to employ some 'over centre' latches which could be worked from the inside of the fuselage joint through the open top hatch.

I found these quite heavy duty latches in Homebase, ideal in size and also including the locating tabs which will 'cross key' when multiple latches are in use.

The latches were epoxied and screwed to the ply plates as a joined pair, they were then separated and glued firm into each half of the fuselage, top and bottom.

The top half was only mounted onto foam, so I keyed the base plate into the bulkhead for better purchase...

Ply mount and latch shown dry fitted prior to screws and epoxy...

[Danny Fenton]

That is some super neat building there Lovely to see such attention to detail inside a model

Cheers

Danny

[Harry Twist]

Superb work there Phil - pure precision! Thanks for sharing.

Edited By Harry Twist on 19/11/2017 21:54:20

[Chris Barlow]

A "clip together" A-10! I like the idea.

What is the total length of the fuselage nose to tail?

[Phil Cooke]

Thanks guys - this has been a difficult part of the build to guarantee alignment of the locking assemblies on each side, access and viewing angles are limited in the front half once they are joined together. It would have been much simpler to build the fus in one piece, install all this gear then cut it all in half and face the mating faces last, but I just didn't have the room in my little garage to build it like that!

Chris, assembled the fus is ~106" long.

[Tim Mackey]

Beautiful as always Sir

[Phil Cooke]

The 2-piece fuselage now latches together well, however there are a couple of further joining features needed to make this assembly robust and repeatable.

Although the latches are solid and pull the fuselage bulkheads strongly against each other, the round aluminium joining tube means an anti-rotation feature is needed to ensure repeatable fuselage alignment, (or timing), and with only 2 latches built in I wanted to 'belt and brace' the flange joint with a couple of M6 nylon bolts mating into captive nuts fitted to the front fuselage section.

The picture shows the 2 fuselage halves, with the fitted joiner tube and latches. I've decided to mount the 2 x M6 bolts where the blue circles are - these will be accessible with a driver through the open fuselage hatch just a few inches rear of the flange. This led me to position the anti-rotation features on the bottom half of the former.

I drilled the rear fuselage former with 2 x 10mm holes and squarely mounted some end-capped carbon tube, sanded flush with the former. Into that I placed 2 lengths of hard wooden dowelling, which I'd shaped so the end formed a central marker point. The fuselage halves were brought together and clamped, this resulted in an accurate mark on the mating former.

The wooded dowels were removed and replaced with carbon 'pins' made from carbon tube end capped with thickened epoxy (which makes them look a lot like liquorice allsorts!) These were epoxied in firm.

With the mating tubes mounted in the front section, the fuselage joint is now 'timed' and needs only the captive nuts and guide holes drilling for the M6 nylon bolts...

Edited By Phil Cooke on 25/11/2017 10:53:19

[stu knowles]

So the overcentre catches are just to hold the two halves together until they are secured by the 6mm bolts??

Great build by the way, thanks for taking the time to post all of this, I'm learning lots of useful stuff.

regards, Stu k

[Phil Cooke]

Hi Stu

So the overcentre catches are just to hold the two halves together until they are secured by the 6mm bolts??

Not exactly, the toggle latches are well proven already on other large PSS models and combined with the aluminium joining tube I think would be more than adequate for flight loading - although I'd fit 3 or 4 - not 2 as currently installed.

This is more to do with landing loads which can be erratic even on a 'good' slope arrival - I just think the addition of bolts nipped up once the latches are engaged will help re-enforce the joint and keep everything firmly in place.

[stu knowles]

Thanks Phil, I appreciate the response

[Phil Cooke]

The 'belt and braces' fuselage bolts and captive nuts are now fitted - completing this part of the build.

1/4" ply load spreaders were cut to rear face the main fuselage formers in each half, giving plenty of meat against which the bolts would pull. Here the front fuselage section is shown with the shaped load spreader (reversed to show the 6mm captive nuts) and a slot cut to suit immediately ahead of the former.

Here's the assembly dry fitted, the load spreader is a couple of mm sub-flush of the veneered fuselage - the 'gap' is an optical illusion although there IS ample clearance around the captive nuts. The 6mm nylon bolts are still to be cut to length...

All glued up with epoxy - I used a pair of metal bolts to pull the 2 ply faces together tight - applying plenty of Vaseline to the bolt and nut threads to avoid the inevitable epoxy bond just where I didn't need it! A skim of P38 filler will finish the small recess and bring the surface back to its original fuselage profile.

The rear fuselage section has had similar treatment - I just need to add some plastic tubing to enable the nylon bolts to be guided and tightened accurately from the rear face of the open wing bay access.

[Phil Cooke]

Rear fuselage is now fitted with the tubes needed to guide the bolts to the blind nuts in the front half - big thanks to Matt Jones who supplied an offcut length of home made fibreglass tubing - perfect for this job.

Focus again returns to the canopy fit on the front nose section.

[Chris Barlow]

Nice an neat Phil. I'm beginning to wish I'd done something similar for the U-2 fuselage now!

Looking forward to your cockpit work next.

[Martyn K]

Stunning. Nice job Phil

[Phil Cooke]

A quick A-10 progress update...the past few weeks it's been off the bench again as some 'test build' work was needed to ensure the PSSA 2018 Hurricane Mass Build will go ahead on plan - that's now all but complete and the A-10 has reclaimed the bench - for a month at least until we start building production kit Hurricanes of course!  

The large blue foam blocks fitted to correct the shape of front fuselage cockpit section have been sanded back and blended into the original veneered foam section.

The cockpit bathtub is now fully lined with balsa and the dashboard is ready for some detailing - I still need to add the console fairing and HUD...

And the two piece canopy has been incrementally trimmed back to suit the new profile, still needs a little refinement in places but its more or less there now. There's an annoying kink in the front canopy at the front which needs to be removed - I might cut it away and build up a wooden make up piece at the front.

With so much exposed foam and filler in this part of the airframe I'm desperate to get it to a condition of final shaping and then glassed up in an attempt to minimise the inevitable hangar rash as work continues.

Edited By Phil Cooke on 06/02/2018 09:20:04

[Andy Meade]

Good to see the Hog getting fettled again. Where is the "kink"? Just where it meets the fuselage?

[Phil Cooke]

yes just forward of where the 'glass' section of the cockpit ends - will be easy to remove and replace with wood up front - will aid canopy retention too.

[Andy Meade]

Yeah mine needed a quick kiss of the drum rotary sanding tool from a dremel, then a "fair amount" of P38 to make the blend. I think there should have been a step in the mould, to pull the edge away from the framework.

[Andy Meade]

double post, sorry

Edited By Andy Meade on 06/02/2018 09:37:03

[Phil Cooke]

I've now recessed the hinges on the ailerons, as Andy has reported a 'trainer like' roll rate without the flaps being mixed in on his model, which I won't be able to do with the knuckle type hinges I've used on the flaps... so bigger 'A-10 like' throws are required!

With the revised geometry the ailerons can achieve a much bigger throw without binding - the second photo shows the original hinging arrangement which limited movement to +/- 30 degrees before they started to bind.  With the mod I can achieve more like 70 degrees if required.

Edited By Phil Cooke on 09/02/2018 11:34:50