PSS A-4 'Thunderbirds' Skyhawk

[Nick Rees]

So it's St Davids day here in Wales but also the start of the Skyhawk mass build project. Thankfully my 'Set' turned up from Traplet yesterday and with a clear work bench I decided to make a start. Well I didn't so much as get started building but spent most of the evening laying out the battlefield for the next couple of months.

Now having just turned forty I'm very much a metric man so all this old school imperial measurements isn't that natural so it taking time to get used to holding the rule the wrong way round! So i decided I'd label up all my sheets to spend less time measuring. So I've cleared the bench popped on my styrofoam building board and got my timber sorted.

Hopefully with a bit of luck I can really get stuck in tomorrow.

[Nick Rees]

OK, so what's the Thunderbirds thing all about? Well I appreciate 1:1 scale stuff but with my models I like to have a bit of fun with the livery. Most of the time it’s simply vinyls printed and added to stock ARTF airframes. However the Skyhawk is a build from plan and having not covered a balsa plane for over 25 years I didn’t want to stretch myself too much. So with a good big of Googling I found the gallery of Clavework Graphics on Deviant Art and decided his Thunderbird 1 inspired Bae Hawk was a great target. Three simple colours and some stock vinyl’s should pose an achievable target on this Scooter build.

Edited By Nick Rees on 01/03/2016 23:34:41

[Phil Cooke]

Nice one Nick, great to see you underway, looks like you have everything you need to hand!

I hope you enjoy your build (we'll soon have you selecting imperial balsa sizes by eye!)

[Peter Garsden]

Looking forward to seeing this one progress. I haven't started yet as I am still finishing off my Jart. Looking good so far.

[Harry Twist]

I hope Parker and Lady Penelope will be occupying the two seats - Parker driving of course...

Great colour scheme and enjoy the build.

Regards and FAB

H

[Nick Rees]

Only manged a little work this evening due to getting home late from work. Started by covering the plan in some clear cellophane floral wrap I picked up earlier from Hobbycraft. Hopefully it will keep my plan in good nick during the build and at just £4 for 20 meters it's pretty cheap. So I can replace it several times if need be.

So with only an hour or so available I managed to get the fuz sides sorted. After much deliberation in my head I think I've got it right. Being a noob at building from plan I'm not 100% sure how I'm going to transpose the fuz side shape to the balsa.

[Phil Cooke]

Hiya Nick. There are a few tried and tested ways of transposing the fuselage side details from the plan onto the balsa, here's how I do it.

You will find that the fuselage sides are made up of a number of straight lines, the only curve is over the wing saddle - more on that later - so straight lines makes things easier. Its really important to get the fuselage sides the right shape, as they ultimately set the incidence of both the wing and the fin (and therefore the tailplane). Its equally important to make the 2 sides the same (until you add the doublers when you need a LEFT and RIGHT handed pair!) but with the fuselage sides alone I tend to cut one to the drawing then make the other match the first by tracing around it and cutting to the inside of the traced line.

Anyway, plan to balsa.

Modify the plan. Start by extending all the fuselage side lines out beyond the reach of the balsa when positioned on the plan. Don't think of this as defacing the plan, its actually making it a usable drawing! Here you can see this will work for the vast majority of cuts needed, only around the 're-entrant' section in the cockpit do we need to employ another method. Extend all the lines, top, bottom, front, back.

Once all the lines are extended accurately with a long rule, place the first fuselage side over the plan aligning it on the bottom front edge (to the solid black triangles) which does not need cutting.

With the balsa in position and pinned down, run round the fuselage side and draw all the lines to suit. It can then be cut to shape.

For the re-entrant cockpit area, the best thing to do is to trace that region of the plan and overlay that tracing onto the wooden sides once cut to the main outer profile. Use a pin to prick through the tracing to achieve the 'corners' of the re-entrant cuts required. Draw in the straight lines with a rule onto the balsa and cut the material away.

This method should produce 1 accurate fuselage side. Its worth carefully marking up all the former positions at this stage too, on the inside of the first side - in the same way by extending the vertical lines axially positioning the formers on the plan - drawing these axial stations on the wood will help accurate assembly later. Remember to cut the 3 slots for the air intake formers at this stage too before you add the doublers, much easier whilst its just a flat plank of 1/8" balsa.

As for the wing saddle curve, once the former positions are accurately marked, dry fit the 3/16" fuselage saddle doubler from the woodpack and use that to draw the correct shape onto the fuselage in the correct position.

Once you've got one fuselage side accurately cut, align it on top of the other side such that the bottom face at the front matches as well as the little wing T/E step formed by the small additional piece. Then simply trace round the first fus side to create the shape for the second. Cut to the INSIDE of this line and you will make a matching pair.

Again, you need to draw lines on the INSIDE of the second fuselage side to aid assembly later.

Edited By Phil Cooke on 03/03/2016 19:57:47

[Nick Rees]

Thanks Phil for the info however it was a little late for me by the time I read it. I used the tracing paper method that I found on other forum threads. Although your method might have saved me time and the £1 for the tracing paper.

I got my sides cut out and started on the triangle sections. I did notice that you have to watch the cut angles when fliping sides but the old addage, measure twice cut once.

I've also cut and tidied all my formers and made up F3 and F6.

Good progress so far, hopefully more tonight and maybe even a end of week beer.

[Andy Meade]

A good start there Nick

I use a ribbon of LED's under my workshop shelves too - works a treat

[Steve Houghton 1]

Watching this with interest and the tips from everyone is very useful!

[Nick Rees]

Last nights session although productive was a bit of a rocky road. I made a few errors that needed to be resolved but shouldn’t make a difference in the long run. I’m concluding that this is all down to my inexperience at scratch building and having more of a follow instructions step by step mentality. The good thing, it’s all knowledge to dump in the memory bank.

Having cut out all the triangular section I glued these down. As it turns out I misinterpreted the plan and cut the section over the wing too short and not following thru to the front of F4. Also despite pictures in the magazine I also cut short the section that intersects with F3. It’s not the end of the world and some fillets will fill those gaps.

Now I didn’t notice the F4 issue until I got to the gluing it in F4 and so a little MacGyver was required. It was also at this point I discovered that my ½” triangular section is 9/16^th on one side so I’m going to have to watch my joints and any affect it has on the interface of with fuselage formers.

With formers F4 thru F7 glued I moved onto the mini puzzle that is the battery box. It seems Traplet made the centre tab ‘off-centre’ so you’ll have to shuffle things until it all lines up. With time getting late and a beer in the fridge waiting for me I set one half of the battery box and called it a day.

[Nick Rees]

Another evening in the workshop working on the Scooter. I did get rolling eyes of my misses before I left but she knows what I’m like. Once I get going on a new project she won’t see much of me in the evenings.

Having left the battery box half done I started by setting the other half so that it would be workable a bit later and complete the whole box. The theory of doing two halves was that if they were both square then the whole assembly would be square. Like Hannibal from the ‘A-Team’ says “I love it when a plan comes together”

In between the battery box part drying I proceeded to put the two fuselage sides together. Now for some reason F6 and F7 didn’t want to sit right, being 1mm higher. This would mean that the whole thing would be out of shape if I left it like that. Now I measured every thing from the distance from the datum to the wing seat doubler where F6 sits to even putting the fuselages sides back to back and it was all the same. There was nothing wrong with any of the formers and it should have all gone together nicely, but it was having none of it. In the end I made an executive decision to remove 1mm of the wing doubler where F6 sits. Once that was done it all lined up bang on.

With the fuselage setting against as many engineers squares I have (maybe I might get a few more :D) I moved back to the battery box and following the magazine I dry fitted F2 & F3. I dug out my ¼” to do the bottom for these to sit on and disaster! I’ve only gone and bought 3” sheet instead of 4”

I pondered my options; did I have anything in my stock pile, No; could I get away with 3”, maybe but I’ll get stuck further down the fuselage; what about biscuiting two 3” to make six and then cutting down to size, but that’s just desperation; In the end the final and winning option was to call it a day and go home for some chilled beer out of the fridge. I’ll order replacements Monday but maybe to make the postage worthwhile I’ll get the material for my next project, Andy Conway’s L39 Albatross.

[Nick Rees]

I've split this post out from my usual ramblings as it's worth highlighting. Phil emailed me earlier today pointing out that I hadn’t inserted the captive nut into F6. Now I was aware that it needed doing but reckoned on it being done later down the line. I am so glad Phil emailed and said to do it now before I went any further. It wasn’t the easiest job to sort out as the hole is 6.8mm and my captive nut was 7.5mm. Ordinarily with a block of softwood I might pull the captive nut into the wood but I thought that was likely to cause damage to F6 with the hole about 1mm too small. So carefully I opened up the hole with a 7.7mm bit and also made four small 3mm holes to ‘pilot’ the prongs from the nut. The later might be over-kill but I wasn’t convinced that the prongs might not damage F6 when it was pulled home. I also added a dollop of super glue to the nut when I was happy to make sure it wouldn’t go AWOL on me.

My advice, get the captive nut sat in F6 before you add it to the first fuselage side. It’s gotta be much easier than what I did.

[Peter Garsden]

Great blog Nick, very clear, so accurate in all your work - sounds like an engineer talking to me - wish I had that much patience, still hey ho as those who like flying more than building, you won't notice a mess when its going 50mph.

Great tip re cellophane. I used baking parchment but you can't see through it. I have heard solarfilm backing recommended but I never have big enough pieces. My dad used to have a hugh roll of it in his workshop but it disappeared years go, so this is a good tip. I am sure you could buy a huge roll of it somewhere.

Anyone know of a large commercial supplier?

[Peter Garsden]

Sorry - just thinking about your engineer's squares - have you thought of an SLEC fuselage jig. I use mine for every model, not just for lining up the fuselage square, but also for holding it in place for tricky jobs eg. Solarfilming the top of a fuselage with a rounded base which won't stand up straight, lining up the fin and tailplane etc.

Maybe you have one - if so ignore me.

**LINK**

[Peter Garsden]

Sorry - just thinking about your engineer's squares - have you thought of an SLEC fuselage jig. I use mine for every model, not just for lining up the fuselage square, but also for holding it in place for tricky jobs eg. Solarfilming the top of a fuselage with a rounded base which won't stand up straight, lining up the fin and tailplane etc.

Maybe you have one - if so ignore me.

**LINK**

[Nick Rees]

I have to confess although I'm an IT consultant I did mechanical & electrical engineering thru college before focusing on electronics during Uni. So I guess some of it stuck with me over the years. I also have a fetish for tools especially buying them and with Axminsters Tools 15 minutes down the road my wallet has taken a hammering lately!

I guess the best place to buy the cellophane cheap would be a floral warehouse. I found some 100m x 80cm online for £7.79 which is much better value. But I did find that because my board and worktop are 60cm deep the roll I bought was perfect only needing cutting along one edge. I used Stix 2 Anything Very Small Craft Dots again from Hobbycraft (again their 15 minutes away) to hold it down over the plan.

Oh and your right Peter I do have one of those Slec jigs. Although mine has inset screws and hex bolts rather than the ones offered by Slec. I just bought the grid and brackets sourcing the other stuff on eBay. I have to say the brackets are not super great and I’m already thinking of making a modified version on my 3D printer, when I get round to buying the printer. :-D

[Nick Rees]

Not much done last night as I don’t have the ¼” balsa for the front fuselage. Rather than do nothing I worked out if there were any bits I could prep ready for later along the build. So I cut out the ½” soft balsa for the nose. I cut out a pair using my usual S&M scalpel but they were a bit rough so I though why not use my Proxxon jigsaw. Proper job!

I also cut out the intake parts and formers ready. I spent the rest of the time tiding up my workshop, it’s amazing how tools seem to spread themselves out everywhere.

[Nick Rees]

I’ve not been able to do much on my Scooter build in the last week because I’ve been waiting for my order from Balsa Cabin with the 4” x ¼” sheet. Even today the order has yet to materialise and in the end Friday I drove the 40 minutes to Western Valley Models and bought a sheet of ¼”. That cost me more than just the sheet balsa as I walked out with a PA Addiction 3D plane!

With the weather being so good the last few days I’ve been banging the packs thru my existing 3D plane, an E-flight Extra 330SC BP, and also maidening my Pilatus B4 that I recently finished. So workshop time has been limited. However tonight I managed to get on with the build and make some progress. I’ve made up the front bottom, cutting oversize as Phil suggested in his build and pretty much following the suggested method of build.

Hopefully I can get back on track and get some serious hours in the workshop this coming week. Maybe my balsa order will show up as well!

[John H. Rood]

Nick, did you know that their ops base on Tracey Island includes a SLOPE?!

(Actually, by the looks of it, SEVERAL slopes!)