Aurora 60

[Jack Banner]

Looking good Martyn, you do build some lovely planes. Can you let me know where you get you fool proofer from? It might stop me crashing my planes quite so much 😉

[Martyn K]

Hi Jack

Normally, on bare wood, I use Spectra Fuel Proofer 2-3 coats sprayed on quite liberally. However, Andy Green has put me on to Klas Kote clear for spraying over already painted surfaces and vinyl etc and I use Klass Kote paint for paint that does not need fuel proofing (it is already very fuel proof) - it happily goes straight on over Halfords type rattle can primers. I wish that I had taken his advice years ago..

Its a 2 pack fuel proofer or paint that needs to be thinned and sprayed from a gun, but it goes on very easily. I have also been experimenting mixing some of the paint epoxy with laminating epoxy and hardner to give a 'painted' finish to any epoxy mouldings and this seems to work well. It only needs about 5% paint mixed in to get a really good density of colour.

You can get Klass Kote in the UK from fighteraces.co.uk, but sit down before you look at the price. Put in perspective, it would have saved me a fortune in costs of rework with the paint on the Magic.

Martyn

[Jack Banner]

Thanks Martyn, I have some Klass Kote but haven't got around to trying it yet. I will do on my next build.

Whilst I have you discoursing on the subject have you had any luck in re-fuel proofing older models where the paint is already coming off? I have an old Cambrian Mustang  fun fighter which is glassed and painted. The glow fuel has badly attacked the finish and it is bubbling around the nose. Also more and more of the paint on top of the wing comes off every time I clean it. I am not really up for a fulls trip and re-paint but would like to re-seal it to stop it getting any worse. Is this possible do you think?

 

You haven't spotted the auto-correct error in your post yet then?

Edited By Jack Banner on 28/09/2015 09:26:05

[Martyn K]

Back on the build after an unwarranted summer recess..

It's also given me some time to think about what I want from this. My feminine side has told me to change my mind and I think that I am going to install a fixed undercarriage. Mainly as I am fed up with the messing around with the Magic set-up - which has now also had its retracts removed and has taken out over 8oz of unwarranted ballast.

As I can hardly see the undercarriage (or the model ) when its flying, I wont miss them that much. Apologies to the purists. Now I need to re-engineer the front end for a steerable fixed nose-leg.

But that can wait. I have started work on the fin. Quite a tricky task, I never really know whether these should be built on the board or in situ. Neither method is very satisfactory.

Anyway, starting from the fuselage..

The first think was to remove about 10mm of rear fuselage so that I can have a full length rudder post with a Kevlar hinge.

The rear block - TB1 was laminated from 3 x 1/2" sheet plus 1 x 1/8" sheet. Clamped and allowed to dry

Roughly carved and glued and clamped into place - so far so good - or so I thought...

A laser alignment check and I spotted - fortunately before the glue dried - that my carving by eye was about 5 degrees out. I checked and double checked and eventually went with the laser..

As you can see - this was before I fixed it..

The fin was built up using the rudder post as the vertical reference - checked while the fuselage sides were jigged to upright - and laser checked again. The laser is on the pile of batteries behind the fin..

Working from a plan only, there is no part information for the inner structure - just a cross section so I could measure the thickness at that point - guessed where it should be at the base of the fin and then extrapolated to the fin top. This was for the ribs and the subframe. The LE of the fin is 2 laminations of 1/2" balsa with a 1/32 ply core. Although it *looks* OK, I am still feeling very uncomfortable with the alignment.

And now it looks like this. Ready for final sanding and a little filler around the base of the fin to help blend in from the fuselage. I have added a 1/32 ply base to the top of the fin piece which isn't shown on the plan. Apart from that, its as the designer intended.

Next job is to get it sanded and filled and then glassed, I can then fit the tailplane and elevators - or possibly start work on the wing as its easier to store like this.

There was a lot of work getting that fin done, its very fiddly.

More to come

Martyn

[Martyn K]

Started work on the wing last night. The spar sizes - in fact ALL the wood sizes - are a bit odd so have had to be stripped and planed to size.

I was unhappy with the quality of wood I had available for the main spar so chose to splice a length of spruce (inner section) to balsa (outer section) with splice displaced by a couple of bays top and bottom.

 

So, starting with a cut and spliced lower spar.

A few wing ribs were test fitted with the slotted false TE. The problem with this type of construction where the ribs are angled on the spar is that they will have an inclination to straighten. Preventing that (by pinning or gluing) means the wing will try and twist instead so you need to make absolutely sure that the TE is parallel to the the center line of the ribs.

Easily done - I just pinned a couple of spacers to the first and last ribs

like this..

Added the remainder of the ribs- checking they were vertical and easing the wood slightly in the rib to accommodate the angles spar and when I finished last at 10:15 it looked like this..

All very straightforward so far..

This morning, an hour before I started work, I added the spliced upper spar and false LE. The false LE is tapered and cut exactly to size. Carefully aligning each of the ribs (upper side) to the top of the LE will ensure that the wing is flat and twist free.

So far so good and fairly straightforward.

(And while the glue is drying I have just started work on the HK Ionos I bought in the early summer). No build blog (its an ARTF and only the 2nd ARTF I have assembled yer honour) for that although some notes may appear on my personal blog.

More to come.

Martyn

 

Edited By Martyn K on 28/10/2015 09:26:23

Edited By Martyn K on 28/10/2015 09:28:39

[David Oxilia]

Martyn,

For what it's worth, I thought you'd like to know that the Aurora depicted in the first image of your thread was scratch built by and belongs to Jeff LeBoutillier based out of Ottawa, Canada. He did a build thread on RCU which is worth reading (maybe you already have).

I have seen that model in person and it is absolutely beautiful. The flying surfaces are especially light and as you can see the model was built with plug in wings. Ailerons and elevators are slightly larger than plans but not in a way that could be easily recognized. After his build, he determined that the fuse should have been built in a lighter fashion more suitable to e-power. The thick 1/2" fuse sides are especially not required with a full fuse frame like his particularly on e-power. They become more important with the full wing built glow model like yours.

As an aside, a friend and I made considerable progress on a 35 size version of the Aurora conforming to the reduced 60 size plans rather than the original 25 size MK plans. Wings were also to be plugin allowing more readily for "area adjusted" surfaces to keep the wing loading in check. The goal was to design an inverted glow engine compact model with fuse integrated pipe unlike the MK Aurora 25 model which has an external pipe. It also was conceived for optional e-power. We worked on it extensively but the CAD aspect was in my friends hands and he was unable to complete the design. The model was also re-designed with a stressed skin configuration rather than the balsa block approach of the original. It was quite a beautiful little classic so perhaps one day I will finish it.

Keep up the good work!

David

PS I have made good progress on the A40 and will drop you an email with further info when the design is complete.

[Martyn K]

Thanks David

I wasnt aware of that. I have also just found the RCU build thread - its here if anyone wants to take a look. A work of art - I'll read it more thoroughly later.

I have managed to acquire 2 more RE 40's (an ST X40 Bluehead and an Irvine 40R) and am also working on a 40 sized Mystic as well - still in the planning and checking stage at the moment though. No rush for the Arrow - take your time.

Best wishes

Martyn

[David Oxilia]

Martyn,

Great news on the engines! If you ever come across another Irvine 40 RE, preferably new, please let me know as I've been looking for one for a while. Being in the UK, it might be easier for you since they are English engines.  Likewise on the OPS 40/45 RE. The ST X40 might actually also be well suited to the A40 since it is a fairly compact model given its squarish aspect ratio design. The pipe tunnel allows for a 15" concealed pipe so a 45 size engine with an 11" prop might require a slightly longer pipe arrangement which could potentially protrude from the tunnel. A solution would be to run something like a 10x7 on a 45 to shorten the pipe. Nothing terrible but I also feel that the A40 will fly well with a strong piped 40 on a 10x6 such as the X40.

On the other hand, the original EZ Mystic 45/90 ARTF (M45) was a rather large model almost the same in size (although not in weight) as a Curare 60. I acquired a kit from which I developed CAD plans after taking detailed and extensive measurements. I am not a big fan of the extensive use of plastic in the EZ ARTF's so my redesign is an all wood fuse design except for the cowling which I expect to make out of FG - both much like Steve Dunning's Supra Fly redesigns. Also, unlike the EZ, my design has a removable top canopy deck and a fixed fuse bottom tunnel for the tuned pipe (engine is inverted). Access to all components is through the top and the wings are plugin and incidence adjustable (if desired). Having a full fuse opening makes for a nice equipment layout including the option to centralize the tank (just forward of the wing tube) for pumped engines (YS, OS). If you are interested in seeing how I went about things, I'll be happy to send you an email.

I expect to make a kit out of this one as well as it is an extremely rare model for which plans never actually existed other than in Hanno's hands (maybe). Given its size, I would recommend running nothing less than a pumped piped YS 45FR/OS 46VF or a 4-stroke 82/90 or e-power (1400W). I suppose a 10 cc gas/glow engine might also be an option (e.g., OS GGT10). Naturally, a SE engine such as an OS 55AX mounted with cylinder at 8 o'clock preserving the central line pipe would also work well in this case exposing the cylinder from the cowling.

 

 

Edited By David Oxilia on 29/10/2015 18:57:55

Edited By David Oxilia on 29/10/2015 18:59:36

Edited By David Oxilia on 29/10/2015 19:00:26

Edited By David Oxilia on 29/10/2015 19:02:10

[Martyn K]

Hi David

Apologies for the delay replying - been rather busy with the AGM for the UKCAA and then the subsequent writing up. I'll mail you about the Irvine 40RE.

However, I have made a bit more progress on the Aurora.

I now have a matching wing for the other side..

The only difference between the two is the undercarriage mounting blocks are on opposite sides of the rib. These didn't fit quite as well as expected (because I had used non standard spar sizes) so needed to be packed out slightly at the spars

Webs have been added and the scarf joint can be seen here.

One question for anyone reading this. It suggests that the inner portion of the TE may be flapped. However, there is no linkage or hinges shown or mention of this anywhere else on the plan.. Any thoughts or history known out there?

A dry fit of the wing in the fuselage to check alignment of the wing dowels and the front ply plate was glued into place. The wing was packed out with 1/16 balsa sheet to allow for the thickness of the skins

and it looks like this

Allowed to dry overnight after checking that everything does align correctly including triangulation.

A bit of a break and then the TE was added, making sure that the subTE was straight. Actually quite tricky and fiddly to achieve

The thick rib for behind the front mounting plate was imply cut from a piece of 1/2" soft balsa

Then sanded to shape

I have also added tow thick cheeks on the next ribs out to give a bit of resilience to my clumsy handling.

Hinge blocks for the ailerons using Kevlar hinge cloth

and fitted. The wing carefully weighed down to make sure it stays straight

U/C blocks in - fixed undercarriage (Sorry)

I modified the original 3mm ply doublers to take the UK standard U/C block. There is also an additional ply rib added on the inner rib that is not shown on the plan

I then started sheeting the wing and fortunately (before I got too far) realised that I hadn't put the servo mounting rails in.. . That was a close one. 10mm square pine

and then added a lite ply facing rib to box the servo in. The string is to pull the servo leads through when I get round to fitting them.

More to come

 

Martyn

Edited By Martyn K on 04/11/2015 11:32:24

[Martyn K]

Carried on with the wing sheeting last night.

The underside was done first but before I started, i jigged the wing and weighed down with batteries to make sure that the wing had absolutely no warps - or worse - twists down its length:

Small blocks placed under the LE

and TE and matched on both sides with the centre section supported as well. Keeps it nice and flat. There actually was about 3mm twist down the length of the wing so I am very keen to make sure that gets removed..

The wing was then sheeted (I had already put in the TE wing sheet top and bottom the previous day) and worked from there.

Each sheet is tapered towards the tip with the grain set down the longest edge.

So the bottom of the wing looks like this now

Final job this morning was to remove the balsa skin around the U/C legs

Coming along nicely

More to come

Martyn

[Nigel Armstrong]

I also built an Aurora from the MK kit back in 1987!! I opted for a fixed "tail dragger" layout to make the engine and pipe instalation nice and easy. The other concern was the grass strip I flew off at the time was less than perfect, so retracts were not an option as the legs bent back causing the wheels to jam in the up position.

The model flew very well but the length of time taken to build it was crazy. I could build two challengers in the time it took to build one Aurora!

[Martyn K]

Hi Nigel

Thanks for the note, its been a bit lonely here for the past few weeks .

I am still going down the trike route but mounting that front nose-leg has not been simple. I'll put some photos up later. Its just as complex to build- if not more so - than the Magic - which came as a bit of a surprise. In the main, I am pleased with the way that it is going together even though I am building from the kit plan which doesn't have all the parts drawn for me. I learnt a lot from the Magic build and hopefully wont be making the same mistakes.

In the main, happier than the Magic but I still have to finish it yet

Some progress

As per plan, I have built up the TE sections of the wing. the little triangles were all measured from the model, however, one slight difference, I have used 3/32 balsa on the lower side - which will carry the wing mounting bolts and 1/16 on the top

Marking out was easier than expected and surprisingly therapeutic.

The TE now fitted, I have also glued in the wing dowels. I didn't extend them into the wing (which I didn't like) but chose to support them with an 1/8" ply plate behind the former. I'll do some photos later.

A trip to Whitchurch models on Saturday and some decent 3/8" square medium hard balsa for the LE with a strip of 3/8" x 1/16" spruce laminated into them. Adds a bit of dingability protection and also a nice line to sand to.

The wing tips laminated from 1/2" sheet with a 1/32" ply core.

...which also helps with lining up

..and last night it looked like this.

This morning, I have started carving and sanding the LE and wing tips. That distinctive Aurora shape is starting to shine through now..

More to come.

Martyn

[Martyn K]

The missing photos:

The front nose leg assembly was beefed up using trimmed beech bearers

The lower one was quite easy.

These are simply epoxied to the retract plate, I am relying on a lot of contact area to take the load. I think it will be OK - glued with 24hour epoxy

The upper bearing point was quite tricky to get into place.Basically, the bearer was cut to fit around the former and partly into the fuel tank tube hole.

A bit dusty in there. The RH screw passes through the former, the LH screw goes into the bearer directly. Again glued with 24hr epoxy. The upper hole id for the noseleg push rod.

The wing mounting plate has been changed slightly from the plan. The plan shows the dowels passing through the front former, then through the upper sheeting into a soft balsa block at the main spar. I didn't like that arrangement so I simply cut a 3mm birch ply plate and sandwiched a balsa sheet in between. The dowels are glued into this sandwich as shown

That should be strong enough, I cant see that failing in a hurry and its far more manageable - especially when I get down to covering the model

Finally, a milestone was reached last night. The model was dry assembled for the first time and it looks like this.

and

(note - the wing is not bolted in yet - that gap disappears when its held in place - honest!)

and

I think that it looks lovely - a very sleek looking aeroplane. Quite happy with the 6 months progress so far.

A few minor dings to fill, next job will be to fit the wing fairings then glass the fuselage. The tailplane is not glued in yet - one lesson I learned from the Magic build so that will simplify the glass covering. I'll also film the wing as well to protect it. I made up some wing bags last night - that wing is very light - 605g so far.

Weight so far 1335g.

More to come

Martyn

[Bob Cotsford]

That's looking very good Martyn, it is a very slippery, streamlined shape indeed.

Edited By Bob Cotsford on 11/11/2015 09:34:08

[Martyn K]

Thanks Bob.

Typical of that elegant range of models like Blue Angel etc from the same design camp. It is nice to behold I must admit. Certainly much more pleasing on the eye than the current crop of F3A models (and a lot cheaper as well).

No rush to finish it, got all winter to get it done.

M

[minty morton]

Lovely Martyn. Looking forward to seeing it for real.

Minty

[Martyn K]

Cheers Minty. Still got that G/F belly pan to make yet which will be fun. Now that I have seen Steve's. I know what to aim for. I am prepared to have several goes at that to try and get it right. A skill I need to learn

M

[Jack Banner]

I'm still following along, just can't think of anything else to say apart from 'that looks great'! Nice to see it together for the first time.

[Martyn K]

Thanks Jack

Lousy weather here in the NW this weekend so made a bit of progress.

I added the wing fairings. I am never too sure what shape to make them so they are simply cut/faired/angled at 45 degrees along the fairing line..

They look OK.. (I think)

I also started fitting servo trays etc for the radio gear. I will be having 2 mini (21g BB MG 2kg/cm) servos for the elevators. Apart from adding redundancy, I will also be able to mix separate (One up, one down) elevator travel with ailerons - just for an experiment in madness.

The rudder servo (closed loop) mounted centrally and below the elevator servos.

I was already very happy with the dingless of the fuselage - so an hour of final polishing and the fuselage was glassed over 2 sessions (Saturday afternoon and Sunday Morning). Using Sams technique of working the epoxy in but I use a small piece of Formica - I don't have enough spare credit cards.

55g of resin used for the glassing using 60gm/meter^2 cloth.

Started second phase polishing last night getting it ready for hi build primer - which will have to wait for a spell of better weather. (Ignore that pink thing in the back, it sneaked in when I wasn't looking.  ..)

More to come

 

Martyn

 

Edited By Martyn K on 16/11/2015 13:42:24

[Martyn K]

mmmm 6 weeks since the last update.. Disgraceful and all that

Happy New Year

One of the reasons (there are 2) why its been a bit slow is that I have been prevaricating over the belly pan build. I originally planned to make the pan out of G/F using a foam plug then a polyester glass mould etc. The problem I had was that I didn't know exactly how big to make it. The plan shows almost no detail so I had to rely on Google for the answers and the best I could find was this.

(stolen from RC Groups)

The green bit is the part I need to make. It looked rather tricky especially as I had not been able to source and blue or pink foam. Time was marching on so I went for plan B - a wooden option. I also had to accept that it would not be a good match, but it may be a nicer shape.

The first job was to get the wing into place and build up the underwing side walls.

When dried, the belly pan sides were cut from 3/16" balsa and carefully sanded to fit. Dummy Lite Ply formers added all glued, clamped up and allowed to dry.

Just look at the blood - this is going to fly well

From the front - the balsa was dampened on the outside then clamped and allowed to dry overnight

The rear of the pan was sheet with grain lengthwise - 3/16" - its fairly flat

The front sheeting is curved and is formed with 3/16 balsa grain across the fuselage

Next - the air intake. This is the big difference from the original which flares into a much larger flatter area. This is formed from 1/8 Lite Ply

Next job was to temporarily refit the engine and pipe and using a Dremel and sanding drum remove the inner formers and a duct hole for the cooling air. Note the blue line indicates where the air intake should be

However, it became clear why the original had such a large flat area behind the intake - so the engine would fit. I decided to simply move my intake backwards a bit. There is also a second intake below the spinner - I think this will be sufficient especially with the head out in the open.

I then had to cut a hole big enough to get the pan over the front wheel. I am glad its not a retract.

I'll do a side view shot later, but I think it looks really quite smart. Not original but I am happy with it.

This afternoon its been glassed (2oz) and is curing as I write.

That's the last major component done. Need to think about getting it finished now. On Doctor's Orders not to use (spray) Klass Kote which is a bit of bummer.

More to come

Martyn

[Martyn K]

I have been a bit quiet on this for a few weeks. Basically, in parallel with the Mystic and the Ballerina, I have been slowly prepping the model for paint and covering.

The Fus has been primed and I am just adding colour now. However, here is the belly Pan, glassed, primed, painted and Fuel proofed

Not too bad but not as perfect as I would have liked. Nothing like a strip light reflection to show every deformity in what should be a straight line.

Need to get a move on if I want it to be ready for the UKCAA Retford season opening event in April.

More to come

Martyn

Edited By Martyn K on 19/02/2016 13:19:52

[Jon Laughton]

Dont beat yourself up Martyn its looking good!

[Martyn K]

ha ha - thanks. There are too many perfectionists here and I am getting paranoid..

M

[Martyn K]

A bit more progress over the past couple of weeks. I am at that paint stage and the weather hasn't really been very suitable for outdoor painting.

However I have eventually finished painting the Fuselage, the rudder has been attached and the tailplane went on last night.

You also get a sneak preview of the colour scheme..

From the rear

..and the front

And while the glue was drying I added some pinstripes..

One wing tip. As I said on Facebook last night. "None of your nampby pampby swoopy curves here. These are proper in your face 1980 style bold block colours in the style of fashion house Dash".

Getting near to the end now...

A bit more to come

Martyn

Edited By Martyn K on 03/03/2016 13:22:27

[Jack Banner]

That looks great Martyn.

Can I ask what you cover your stored models with? Is that bubble wrap or some other soft plastic that is draped over the two fuselages in your first pick? I have recently come to the conclusion that I need to cover my stored models to stop them getting covered in balsa dust etc. as my work space is also my storage space. I got a plane down from the roof yesterday and it had far too much sawdust etc on it.