Rockingham Model Aero Club at Lake Walyungup

Scratchbuild

Scratchbuild 1/2a All Sheet Control Line Stunt Model

Hey guys, Just thought some of you might like to see what I get up to in my tiny little workshop.
Before I start on my next big project, I thought I’d try a few new ideas on something small, and also something quick so I get back into the rythym of making bulk balsa dust.
Considering the amount of fun I’ve had with my tiny control line models, I thought I’d do one that’s a bit more sophisticated, and a little bigger. I’ve chosen as the White Lightning as the basis. This will give me working wing areas and moments (length between wing & engine and wing and tail), as well as a good guide for thicknesses of stock.
Here tis:
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Anyway, lets get down to it.
Welcome to the Inner sanctum.
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This is my workshop. It’s probably a bit different to most in that I’ve got a sheet of glass for my work top. I originally started using the glass top when I was cutting foam wing cores, as it’s pretty hard to burn through glass, and also it makes sure that the surface is as flat as I can get it. This means there’s no wobble or woofs in the table, and when I cut the cores they won’t be wonky due to the table, only the operator! Another thing to note is the green play mats all around the place. I have crappy ankles and standing around on the concrete floor for a few hours will have them sounding like they’re full of marbles. After much nagging from Erica we bought a bunch while they were on special at bunnings, and they’ve made it really nice, I can build longer and if I drop things, like small bolts they stick out like dog’s balls on the green mat. Win win!
Here’s the operational hub of the workshop.
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It may look like a mess but everything has a home. All the hardware for models, and some small tools go into the cabinets on top. I never thought I’d need this many but now they’re full I think I need more! Underneath that from left to right, I have a nook for all my cutting and sanding tools, so sanding blocks, balsa strippers (wahey!) and other assorted bits N bobs. To the right of that is my glue caddy. It’s divided up so I can find what I need, and it’s made out of cardboard, as no doubt there will be the enevitable glue spill so I’m not going to make it nice.Note there’s no CA in there. I find that CA is best stored in a sealed container full of dessicant (nick the silica gel packets from shoe boxes) as CA reacts with moisture, if you’re not build for a few months, stick the container in the fridge as the cool dry environment will increase it’s shelf life.
To the right of that we have glad wrap and greaseproof paper, and the start of my million rolls of tape. Underneath that is all my sand paper thats in flat sheets, while the rolls are to the bottom right.
The little pocket to the top right contains all the stuff for plastic models and detail work, like making cockpits and things. It’s suprising how often I delve into that patch which I need something special done.
This is something I nicked from one of the best builders in the world.
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If you’re like me you’ve probably got all your dremel tips just floating around in the box it came in, and you’ve probably broken more cut off wheels that you’ve had hot dinners. A small box with some lines drawn 25mm apart, and holes punched almost all the way through the card will give you a nice little stand, where you can see what all your tools at once, so you can pick the right tool for the job, instead of settling for the one you can find.
Here’s another cool little trick
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This is one of those el cheapo bendy lights from ikea. It has a spring clamp at the base, and is really usefull for those times when you need a little extra light around the workshop. Generally it hovers over my drill press so I can see what I’m doing, but also occasionally ends up on the workbench shooting down a fuselage so I can see what’s happening way up in the back. having the spring clamp means you can clip it on, bend it to the right spot and use both hands to do what you’re doing. Stops you having to stuff a torch in your gob for those finnicky jobs.
Ok, next post we may actually start cutting balsa

RIght, now as I said I’m going to “bash” this model pretty heavily, to suit my own style, I really want this to look like a 1970’s sleek stunt ship. If you’ve never had a look at stunt models they’re something to behold. Always super cool, and the finishes are to die for (actually they’re to win for. In the stunt rules in the US you can gain an extra 20 points to your score purely through apperance points, the prettier the model, the more points you get)
I mean just check that for a model, hooooweee!
reg.11.fanchertrivial
Anyway enough blab, lets go.
My printer at work will do A3 quickly, so in between jobs I scaled up the plans to the right size and printed them out peicemeal. When I join plans that are in bits like this I like to cut a wavy line rather than a straight one, as I think it gives me more spots to check that I’ve aligned the pages correctly. It’s probably bunk but it helps me sleep at night.
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Once we have the plan all joined up, (in this instance it’s the fuselage side) use the plan to place all the markers you’ll need on the fuselage.
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Here you can see the centreline for the engine and the end of the fuselage are marked.
To ensure everything is algned, I’m using the bottom of the fuselage as my reference. I like to find nice straight things around the workshop to ensure that all my lines are parralell to that bottom of the fuselage. This way I can be more accurate than two measurements.
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After we have our engine centreline, our wing and tailplane lines drawn in, we can get creative on a fuselage design. I’ve gone for low-rider look for mine.
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The wing is made primarily from two sheets but joined, and then wing tips are added with the grain going 90° to the main sheeting. this will stop the wing tips warping and makes shaping the tips slightly easier.
Joining sheets nicely is easier than you think. I edge sand the sheets with a big peice of angle aluminium longer that the sheet (mines 1,2m long) that’s been covered in sand paper. This is a GREAT tool which we’ll be using in later builds. ensure that you sand the edge square and not at an angle.
They should butt together without any gaps.
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Once they butt up nicely run a peice of tape down the length of the join.
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flip the peice over and using the tape as a hinge, open the join.
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put glue in there. Some like to use CA, but for this I use plain old balsa cement as it’ll pull the sheets closer together as it dries and is easy to sand
Once youve done that lay the sheet flat and look at all that glue that’s ooozed out. EEK!
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Don’t panic, while the glue is still wet grab a credit card and scrape off the excess for a perfect join.
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Now that’s done, lay it down on your greaseproof paper (just in case you missed a spot) and weigh it down flat. I use steel blocks as weights but old magazines & phone books work equally well, just make sure you put more greasproof paper on top of that before you lay the books down or you’ll a readable join.
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At this stage it’s time to stop work and clean up, and go to bed.
Till next time!

Fuselage time!
Ok, so our fuselage has two jobs, one to hold the wing and tail apart and two, hold the engine onto the wing. As our fuselage is only 5mm balsa, we need to add some strength to the nose, and we need to create a strong crush-proof mounting for the engine bolts.
Using our motor as the jig, we figure out where it needs to be so the prop isn’t sticking 2 miles out in front, and at the same time we mark what we need to cut out to get the engine in there.
Like so
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Now for the crush proof mounts, the plans call for maple, which is hard to find in WA, so we west aussies use Tassie oak from Bunnings. Mine was a bit thick so I sanded it until it matched the fuselage.
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The mounts are inset into the fuselage on either side of the engine, We use our mounts as templates we mark onto the fusleage where they go, and cut the whole area out.
Once this is done we need to add that all important strength to the fuselage and we use 1/32″ (0.8mm) ply on either side of the fuselage right back to the wing.
Here’s one doubler ready to be cut oversize.
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Once that’s been tapered at the back so you don’t end up with the ply just ending causing a weak spot, we glue the mounts and the doubler on with epoxy. Anything to do with engines I use epoxy, as its fuel proof, and will cure even if it’s 2 miles under a doubler. glues that react with air will never cure fully under a doubler.
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Clamp that baby down nice and tight!
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I forgot to mention in the last one about cutting nice slots for the wings and tail.
Getting cuts to end nicely (I dont like square ends as they are points of high stress and we don’t want any failures!) was a pain, until I stumbled across this way to do things.
Get some brass tube that’s slightly oversized, and sharpen one end using a drill bit. Mark where your slot needs to start and finish and using the sharpened end, just roll the tube between your fingers and apply some downward pressure. IF you’re patient you’ll end up with a perfectly circular hole that’s cleaner than any drill bit could ever do. After that it’s simply a matter of joining the holes with a nice sharp knife.
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Now that our wing is dry we can start to cut it up. First thing to do is to cut the taper with a long straight edge and a sharp knife..
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Next is to sort the tips out. These are bits of scrap from my giant scrap box. I don’t chuck anything bigger than a playing card away. You never know when you might need it!
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AS you can see i’ve scribed out the shape for the wing tip. I’ll cut two at a time and sand them as a pair so they match perfectly.
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In the meantime I’ve glued the other doubler on the fuselage and given everything a nice sand.
Here we are, with a wing and fuselage! Quick work!

Right, lets carry on.
Now that our wing is done, while it’s all in one peice, I sand the wing nice and flat using 240 grit sand paper. This is easier to do while it’s still a flat plate rather than in the plane.
Once I have that sorted I go and grab my trusty super long straight edge (a peice of ali t bar abour 1.3m long) and I cut off the flaps. These work opposite to the elevator to allow for a tighter turning radius. There’s a lot of square maneuvres in competition stunt, and you’re graded on acurracy and tightness of the corners.
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So, with that done, we now have to fit all this in the fuselage. Seeing as the flap is 30mm wide at the root this would be too large if we put a cutaway in the fuselage to leave any meat. so I opted for a 20mm cutaway and I’ll notch the trailing edge of the flap. Beacuse we’re removing strength from the flap right were we need it, I add some 1/64″ (0.4mm) ply to both sides and sand the ridges off. This stiffens up the flap centre nicely. With the sanding drum fitted to the dremel I notch the flap until everything swings nicely. Too easy.
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Chasin’ tail.
Well the front bits are all done, and it’s time to look at the tailplane. Rummaging around in my scrap box I found a peice just big enough for the stab, but not amount of hunting found a singular peice for the elevator. So I improvised. Joining two peices of balsa is best done with a diagonal scarf joint. I line the two peices up on a straight edge, and cut through both at the same time, trying to keep the knife at 90° to the table. once I’m done the peices should fit together perfectly.
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Now to shaping. in order to get the closest approximation from left to right, I cut one end off, and use that as the template for the other end, that way they’re as close as I can get. NO wonky planes allowed!
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And here’s the finised tail. Not sure I like the change in colour between the two peices of balsa though
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Durrr Whoops!
You know the old saying measure twice cut once? Well it seems I measured once and will now have to cut twice. When fitting the wing and flap into the fuselage it became glaringly apparent that I’d overshot on the wing cutout. If this were a show plane I’d start sweating but everyone who’s watched me fly will know this won’t last forever. So what to do?
Well in order to make sure I don’t add any undue extra weak spots, I dremelled out the flap cutout to a round, and cut a peice of round balsa and CA’d it in. A good trick here is to fit it, sand over the patch, leave the dust and CA around the edge. THe dust will act as a filler and make sure that everything is bonded nicely. WHile I was at it I added a couple of half moon doublers out of 1/64″ ply over the bottom bit that was frighteningly skinny, The grain of these doublers is set at 90° to each other to give me maximum stiffness.
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once they’re on, I give them a sand to fair them into the fuselage and we’re good. WHEW!
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And here we are at the end of another night, and a quick check to see how we’re doing. All the parts on the scales tops out at 89g. Not great but I’m not going to hang myself over it either.
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Playing with my small cox.
Hahaha. COuldn’t help myself.
The motors that I use for these engines are from the now defunct COX company, and while they’re out of business, you can still get parts and some engines from cox international in canada.
Google it if you want to have a look, as it seems every time I try and chuck up a link the forum throws a tanty.
I recently bought an old engine off EBAY and when it tuned up it was gunky and not nice. I gave it a clean and when I looked closely I noticed it was suffering from the characteristic split in the intake tube from some dolt overtighting the carby (it screws in).
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I’d heard of guys fitting a brass collar over this to stop it happening, so a trip down to suk hobbies gave me a perfectly sized peice of brass tubing.
5 minutes with the dremel cut-off tool and the sanding drum (notice the little scallop in the front to fit over the bearing barrel) and I think we have a winner.
TO give you an idea of what you’re looking at that tube is 8mm in diameter. I lost it twice once I made it
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Slide it on, give it a hit with some thin CA to make sure its stable and rescew the carb back on, VOILA!
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Mount up!
Ok, it’s motor mounting time. first thing to do is sit the motor on the fuselage and mark where the bolt holes go. I like to use a mechanical pencil for this with the lead sticking out about 4mm. It’s very fragile so be careful that you don’t push to hard. Run around the inside of the bolt holes so you leave a perfectly circular mark on the wood. DO all four bolt holes at the same time. (This also works for big engine mounts too) Once you’re done. lift off the engine and check your handiwork.
Ok, over to the drill press. We’re going to use blind (tee) nuts to hold the engine down, so find the appropraite blind nut and wander over to your drill bits. We’re looking for a drill bit that makes the outer part of the blind nut. Like so.
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This is where one of the greatest sneakies comes into play. I have a peice of 19mm balsa that was far to heavy to use in a plane, that has become my drilling & sanding pad. Rather than ding up your nicely sanded work on the table of the drill, put down your sacrificial pad, and place the fuselage on that.
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Once you’re done check again to see if the holes are right, and yes they are! I tap the blind nuts in and then coat with epoxy being careful not to get it in the threads.
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Wee! We’re movin’ right along!

Right, now that the hard stuff is over lets frame up.
With a control line model accuray is important. Once you set off if the model is out of trim you have to fly it no matter what! They’re far more suicidal that RC models, so you have to take extra care when setting up to ensure you don’t build a pretzel.
Using the fuselage as a guide cut some props from scrap. These are cut to the same height as the wing and stab slots. When everything goes together these will hold the wing and stab perfectly level (assuming they’re straight of course!)
Ok, so first things first. We need to ensure that our fuselage is vertical. I have a bits of scrap balsa that I’ve cut into 90° triangles, these will hold the fuselage vertical on the workbench.
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Glue down two to the glass, yes right onto the glass, in a straight line. but the fuselage up against those and add two more on the other side. the fusealge is now nicely held in place dead vertical.
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Next, we slot the flap and wing through (flap gets hinged later but is loose for now) make sure it’s in place left to right, and square to the fuselage. because our fuselage is a plank we can use a set square for this. On an RC model, measuring from wing tip to tail is best.
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When we’re happy with the aligment, tack glue the wing in place with some thin CA ( a drop at the front and the back is enough), and feed some bi-carb into the join. I have bi-carb (nick it from the kitchen) in a salt shaker and I shake on a bunch near the join, and brush it gently into the joint. I then hit it with a nice bead of medium CA. The bi-carb will help the CA kick and will also fill any nasty gaps.
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DO the same for the stab, and check that your props are still good, by sighting down the fuselage to make sure the wing and stab are parrallel.
That’s the framing done!
Now it’s onto the fiddly bits.
Now that the framing is done we can simply knock the upstands and props off the glass, which will leave a little dag on there.
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Get out that scraper and scrape the glass clean. I like to hit the glass between jobs to make sure that there are no CA dags or anything that will but scuffs and dings in the balsa.
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OK, so our framework is all but done. Time to add some bits and bobs.

 

A simple way to add landing gear is to mount it to a ply plate by sewing the wire onto the plate, and hitting it with CA. After that’s done you can mount the plate to the wing, or the fuselage or wherever you like (fin? nose?) Just to add a bit more pizzaz I covered the spindly wire with balsa stock to make a set of gear doors, These are set with the grain of one peice at 90° to the other to make a balsa ply.

 

 

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THe next thing to start sorting out are the controls, given the smallness and the lightness of the model, it’d be idiotic to use huge RC style horns, so I made a set out of ply. I’ve cut away a section of the horn to slide into a cutway in the flap, in the old ‘eggcrate’ style. This makes for a nice fit which when glued will add a lot of stiffness to the flap, and make sure the horn can’t break away. You can also see that the horn buts up against the 1/64″ ply doubler on the flap. The elevator is done is exactly the same way.

 

Here we are ready for finishing. Looks low sleek enough to fly!

 

 

Now lets get down down to finishing, as I’ve said before this is supposed to be a light, simply model so I’m not going into for a 50 coat buffed finish you can see yourself in. but we do need to fuel proof it and stop moisture getting to the wood as this will make it turn into a banana down at the lake!  For simple stuff like this I’m a big fan of using good old aeroflyte (now pacific balsa) dope. I thin it down, 50/50 with lacquer thinner You can get cheap stuff from bunnings but this seems to make the dope dry cloudy, so I use thinner from anchor paints on dixon road. This has retarders in the thinner to stop the paint drying too quickly, and building up condensation on it, which will marr the paint. This is known as blushing. It’s no fun. Scrounge up a metal lidded jar from the kitchen (I use old sauce jars and stuff like that all the time), and do your dope mix in the jar, rather than make a mess of a whole litre or whatever you’ve bought.

So, we fine sand the whole model with 400 grit wet and dry, take it outside (dope stinks) and give the model a liberal coating with the thinned dope. don’t worry about cleaning your brush, just sit it on top of your jar to dry. And here’s the hard part. LEAVE IT. Leave the model for a day to really let all the volatile chemicals in the dope gas off. The longer it does this, the harder and lighter the finish becomes. When you come back, the plane will be fuzzy. This is from all the little fibres sticking up from being suspended by the dope. grab your trusty 400 grit wet and dry, and give everything a sand to knock off the fuzz, and lay down another coat of dope. I tend to go for a minimum of three coats to ensure that the model is well sealed. After that it’s time to start thinking of a colour scheme.

I really didn’t want to work too hard on this as I’ve said, so I cheated and added a little acrylic lacquer to my dope as a tinter (metallic teal, not that you’d know it :D) Masked off the schemes on the wings and tail to give me a simple two-tone finish. I just sprayed enough of my tinted dope over the model to get a good depth of colour and demasked it. I should have stopped there after a a coat of something like Top Flite Lustrekote clear which is reasonably fuel proof (around 15%).

 

For the next bit I should point out that for me, every model like this is an experiment, either with construction, painting, finishing, or servo mounting, I’ll try anything I think is cool. On this model I wanted to try adding some accents to the paint. I’d heard that some guys use Sakura Micron pens to do panel lines. I couldn’t be bothered with the panel lines but I thought a little black line around the schemes may add a bit of punch, So I bought one. Here comes the other experiment. I’d found a place that does a two part epoxy clear paint that is water based, and apparently impervious to everything. Wahey! I bought some of that too.

 

After I’d got my panel lines on I tried spraying some of this amazing mixture. It came out of the gun like spaghetti. Obviously spraying is not the answer, so I grabbed a foam applicator and sullenly went to work on the plane. I hate brushed finishes, I can never make them look right, but I was committed. After a few brush strokes I noticed to my horror that the ink lines were being smudged by the foam applicator, the water based clear was attacking my water based ink lines! After taking a few deep breaths and considering my options (I had none), I decided to hang the model up to dry and deal with the consequences. As I say, in hindsight I’d have just gone with the lustrekote.

 

The last thing to do was mount the engine and tank, fit my bellcrank for driving the control surfaces and fit the pushrods, and go fly.

 

The plane flew great, but as with all things like this, the pilot at the control isn’t! I decked it about 6 times before it finally met it’s untimely demise, mostly through some dumbass at the handle.

 

Still, all is not lost, there’s a newer, bigger bird on the table, and if you guys are interested I’ll do a log on that too.

 

G

 

This build was done by Greg here