Aurora 60

[Martyn K]

(Image from RC Universe)

I still haven't managed to date this model. Looking at the way it was fitted out and the colour scheme (reminiscent of a Wolfgang Matt Joker), I would guess that it is an early 80s design. If anyone knows what era it is, I would live to know. Whatever, I think that it is an absolutely gorgeous looking aeroplane, and not one I have seen in real life.

I started work on the model, transferring the parts sheet to DXFs a couple of months ago and these were sent to Dylan at Lasercraft Services who has converted them into a parts kit for me

and

and

Its a bit bigger than the usual models of this era.. 67" span with a 3.8kg target weight. I really want to try and keep this one as light as possible so I'll be watching the weight a little more closely.

Having sat down and looked *really* at the plan for the first time tonight, I can see that this is quite a complex build - certainly comparable with the Prettner Magic, if not even more complex.

The plan shows a Vari pitch prop, full retracts, a convoluted path for the tuned pipe, GF lower tunnel.

My plan is to simplify the build where it is appropriate without losing the character. The power plant I intend to use will be the OS61VR that I used in the very short lived Concept. The retract units are MK type air retracts and the front is offset somewhat to get the pipe to fit.

At the moment, my thoughts are to use fixed undercarriage or alternatively make it into a tail dragger (shock/horror) and just use 2 wing mounted retracts. Not sure how feasible that is as the wing has quite a bit of sweepback on the LE and the main spar gets in the way for a simple fitment.

I don't really want to have to do a major redesign, so I am still thinking this through. In the meantime, I can get on with the fuselage and tailplane.

The only other difference I am considering is to make a wooden tunnel for the pipe and possibly a foam wing. However, it would be a waste not to use the balsa ribs that Dylan has cut for me.

Therefore, a few design issues to resolve before I get too far into this

More to come...

(But this will take more than 3 weeks)

Martyn

[chris Bond - Bondaero]

Fabulous looking plane one of my absolute favourites. Can I get the kit of parts from Dylan also?

Flown by G Naruke at the 1987 F3a world championships in France

**LINK**

[Martyn K]

Thanks Chris

You are welcome to get them from Dylan - he will get in touch will me if there is any confusion or alternatively, I can share the DXF files with you (or anyone else who wants a set), the plan is available off the UKCAA web site > Resources. However, Dylan has the cut files done for his laser cutter, it would save work If we used the same file. If you do go directly to Dylan, let me know and I'll remind him which set they are.

Caveat.. There may be some errors which may need to be reworked (although there is nothing obvious). I have also put extra ply wing reinforcements in for a fixed undercarriage as an alternative to the beam type used for retracts (both sets are included - 3mm ply).

And thanks for the link, it must have been one of the last of the trike era based models

Regards

Martyn

[David Foley]

Aurora was flown at 1985 Worlds in the Netherlands. Model used in 1987 Worlds was a Silent (as seen in link)

one of the early 4 stroke designs.

Dave

 

 

Edited By David Foley on 06/07/2015 01:15:07

[Bill Michie]

I remember a couple of SA fliers using the Aurora in the mid-late eighties...............Beautiful lines & flew very well. Was right at the beginning of the Turnaround era so was really a "crossover" model with ballistic influences, but bigger for Turnaround Pattern. IIRC, was towards the end of "Swept-wing" designs too.

Lovely model, you HAVE to make it a Trike Retract model!

Regds, Bill

[Owdlad]

Try central hobbies they supply off-set manifolds for the aplication you require

[Martyn K]

Thanks All

I have checked out the You Tube Videos. I noticed that Chip Hyde (USA) also flew an Aurora in the 1987 W/C.

I am happy with the age of the airframe now and its near enough the UKCAA cut off date that no-one really seems to worry about anyway..

Retracts and pipes. Talk about Peer Pressure

I can get Just Engines to make me a manifold - that's the easy bit. The other problem I have (which I forgot to mention), is that if I use the OS61RV - with the carb at the rear, I have to move the Firewall back a bit to get the prop driver location correct and the engine to fit. That is not too much of a problem. What would be a problem though is the nose-leg retract would also have to go back as well. There isn't much space anyway (less than 3mm and reducing as the pipe swings back down the centre line) and just getting the fuel tank to fit will be a challenge as the gap between the Firewall and F4 will be reduced. (I cant move F4 as that delimits the rear of the canopy).

I think retracts is definitely the way to go, I am just not convinced that I can get a good enough nose leg installation that I will be comfortable with (allowing for my budget.

A tricky decision. I don't have to make it yet..

Possibly

Best wishes

Martyn

[Bob Cotsford]

How about making F2 in two pieces, the upper half moved back to accommodate the carb with the lower section as per plan to give room to get a decent length noseleg in? On the Blue Angel I made a box protruding through the firewall to fit the nosewheel retract, it was that or a cutout in the wing LE to clear the wheel.

[Martyn K]

F2 is already split Bob.

The problem is that the manifold needs to come out from the RE and through an orifice. into the tunnel I'll get the engine into a mount and dry fit and report back later. I only have to move F2 back to accommodate the carb, the RE will still be in the same place (thereabouts).

 

It's a tricky one..

Martyn

 

Edit - you can see F2 (2 off) on the top "box of bits" photo. Too small to split further

Edited By Martyn K on 06/07/2015 13:22:48

[Martyn K]

Well - here is the Hatori Header for an OS61RF and Aurora 60 - Need to check it will fit mine

Martyn

Edited By Martyn K on 06/07/2015 17:02:16

[Martyn K]

While considering retracts and tuned pipes and the meaning of life, I decided to make a start on the tail plane. At this point I spotted the first disparity (or error!) with the plan. Nothing serious, but the false TE is drawn far too wide. It doesn't affect the build, but it was a very good warning of other errors that I am likely to find.

The other problem was that the slots for spars etc. are slightly different to the sizes on the plan. Again, no a huge problem but the 6mm spar for the tail plane was actually nearly 7.5mm on the rib. If you are going to follow this, you will need to double check the dimensions on the cut parts.

The tailplane with he false TE and lower spar. Not much to show, but its a start. I have extended the tailplane drawing across the plan - only half a tailplane is shown plus the start of the outline for the LE and TE on the ghost half. These were extended and the rib positions drawn in by hand.

This shows the real false TE and the drawn false TE (S12) on the plan - its twice as wide.

More to come.

Martyn

[IanN]

I am in awe of how quickly you turn out models. In the time it's taken me to scratch my chin and prevaricate about the best route for the pushrods on the project currently on my bench, you've built a Kwik Fly from scratch and started this one

[Martyn K]

Thanks Ian

The Kwik Fli was a very easy build. A simple box fuselage with foam wing and I hope it inspires some of the non builders to have a go. Certainly, one of the Facebook followers has indicated that he will build one. I am fortunate that I have had the opportunity to spend an unusual amount of shed time in the past few weeks. I keep a build time log and I have spent just over 100 hours putting the Kwik Fli together, if I only had the sort of time that most builders allocate for shed time then it would have taken several weeks longer.

I make no secret though that I really enjoy building. It is a major part of the hobby (time and enjoyment) for me and if I didn't build I probably wouldn't fly either. I have currently got 3 projects on the go at the moment although one (the Chippie) is parked while I think about the level of detail that I want to achieve. It probably wont restart again until Autumn, which leaves the Aurora and the Slope Soarer design. However, I have already started planning for the next one (another Classic F3A) when this (or the Slope Soarer) gets finished. It has to be a weird addiction.. Must be something they put in the balsa dust..

Anyway, only a little progress this morning, I fitted the upper spars (hard balsa) to the tailplane and puzzled further about the rear false spar. I am not sure that it is a plan error now.

Here is a snapshot of the plan showing the tail section. The ribs have been cut from the parts sheet and slotted for the 'narrow' S12 (false TE). However, the plan has a dotted extension to S12 which is also shown on the section of plan above the tail section with part of the rib 'hatched'. No instructions (or if there are any they are in Japanese) so I have simply used the narrow S12 rather then the wide but I admit that I am puzzled about what the designers were trying to achieve. I am not going to do anything about it now - it's too late, but nonetheless I am still a bit puzzled.

More to come

Martyn

[Bob Cotsford]

Martyn, it looks to me as though S12 should be the full width to the dotted line in the last pic, with notches to locate the rear of the ribs. The tail section looks to be taken through a rib position hence it shows S12 width as being at the centre of a notch, the full width being the dotted line area. In the plan view the cross-hatched area of rib represents the portion penetrating the S12 notch.

[Martyn K]

Ah - now that would make sense. Thanks Bob..

A slotted false TE. The wing is different although a false TE is used on both sides of the rear spar inboard of the aileron

[Owdlad]

I concur. S12 is notched for the rib to interlock to add strength to the joint.

The attention to detail in Japanese kits is second to non

[Martyn K]

Just a bit more progress last night, had family round for a little while and I actually god a reasonable nights sleep this morning, so no real shed time (well 30 minutes before work).

The upper spar and false LE have been added..

and although not shown on the plan, I have added 1/32" balsa shear webs

with the grain running vertically of course..

I used medium hard balsa for the webs, may be OTT, but I don't want another tailplane to fold mid air

The other non standard bit I have added is a spar brace (only one side) in addition to the LE brace. The dark line at the join is not a step - its the web, the join is as smooth as a babies posterior.

So, with the tailplane now lifted off the plan, I can have another look at the front end engine mount and retract challenge

Engine located over the plan and you can see how far that F2 is going to have to go back. There is a bit of parallax error - front and back) so its not quite as much as it looks.

Locating the front retract (borrowed off the Magic), you can see where the retract unit overlaps the header. Also the rear parallax error has vanished in this shot

Looking from above, with the retract shown where it should be on the plan (offset to the lower side in this photo), the path for the header is quite a sharp bend upwards (in the photo) then down again to line up with the pipe. Its slightly worse than this as the engine has more right thrust than I have shown.

However, if I reverse the positions so that the retract unit is on the upper side of the photo and the correct thrust line set for the engine

then I think I can get a much easier fitment, so much easier that I think I can use the existing header. Which begs the question why didn't they do it this way on the original... It cant be that simple..

Your thoughts please Maestros

More to come

Martyn

[Martyn K]

I have decided to go ahead with the front retract but fitted to the opposite side as I described above. Fortunately, the method of fuselage construction for the Aurora necessitates building the front crutch first Last night I started gluing the Formers 2,3,4 and 4A to F9 - which is the ply base of the crutch

I have had to move F2 back about 12mm and open out the hole to allow air to get to the carb. I had already placed 2 F2's (3mm ply each) in the parts kit so I doubled these up to compensate

The former is offset slightly, the sides will need padding out with a strip of 1/32 ply to compensate for the former being moved back slightly. The taper at this point isn't excessive and I thought a little extra reinforcement wouldn't go amiss.

With the three formers fitted and a piece of additional triangle stock - which I now have space for

This shows how far back F2 has had to go, I will need to find a slightly smaller fuel tank as well.

This morning, I started work cutting the beech bearers. I need to redo the left hand bearer as I cut the notch too deep

A notch has also appeared in the lower plate to accommodate the header pipe..

The idea is to get the crutch finished, engine and retract fitted and make sure it all works OK. If it does then I'll continue with the fuselage, if it doesn't then plan B will be a tail dragger with wing retracts only. Its looking OK so far.

Fingers crossed and more to come

Martyn

[Martyn K]

Quite a good session last night and nearly another 3 hours in the shed again this morning. Insomnia has its advantages

The next think to do was actually check that the thrust lines were correct. The only reference I had was F9 baseplate which unfortunately was not parallel with the datum - 2mm too short at the front compared with the rear.

All the parts were clamped together and measurements began

F9 was then jacked up and adjusted and the little bubble app zeroed on the plate

Transferred to the bearers and check again

It should be 1.5 degrees - 1.6 is near enough..

Dry fitted F1 - this involved notching the bearers slightly. I Tried to work out how to measure the right thrust, but couldn't actually do this with all the clamps in place, I did make an approximate measurement and it all appears OK - within about 1/4 degree. However, the bearers are in the correct place as shown on the plan, the engine was dry fitted (help in place and a check that F1 was parallel with the prop driver. All epoxied up and then allowed to cure overnight

This morning I started work on mounting the engine and seeing if the retract unit really will fit.

The engine was placed, mounting holes marked and drilled, aluminium back plates added and the screw heads linked with piano wire and soldered up.

It looks like this

and

Moving on..

However, the header is in the wrong place, it needs moving upward (on the photo) about 5mm 1/3 back and about 12 mm at the end and also curving so it lines up correctly with the tunnel line.

So header off and 10 minutes or so with a blowtorch and a few mandrels and just a little brute force.

and there is now space for a front retract unit

It actually had to be adjusted again as the header was too close to F9 and needed to be lifted by about 5mm to allow the silicon junction tube to fit

It will line up nicely with the tunnel - and the pipe..

Finally, I also found a 320cc fuel tank - a bit smaller than the 400cc shown on the plan. This needed the holes in the formers opening by about 1mm each side to get a nice sliding fit.

Now it looks like this.

Just enough space for the wheel to retract.

That's the last update for a week or so as I am having a short break.

All in, I think that is good progress for week 1.

More to come

Martyn

[Martyn K]

Quite a bit of progress in the past few days. This quite a complex build and there is quite a bit of head scratching going on here. I don't have the full parts list and the plan isn't especially helpful.

2 weeks ago, I had the front ply assembly engine box completed, time to move on.

Fuselage sides have been cut, ply doublers added, errors corrected -I managed to include the LE profile when I cut the parts - I should have stopped at the former - now corrected. oh-hum

Start gluing this up. This is quite straightforward as the ply box assembly was straight and square, I just need to make sure that it was correctly aligned - quite easy as the bearers line up against the upper fuselage edge

Onto the jig for the second side. Quite a slow process as I wanted to make the section around the box was totally dry and the glue hardened before I pulled the sides in around the front section. It looks rather odd with the asymmetric bearers and I had to double check that I wasn't building something with the thrust line squinting or offset.

Looks weird doesn't it? The straight edge is an extension of the jig centre line to make sure the prop driver really is central

A quick check that the tuned pipe lines up - it does

Engine bay area fuel proofed with Klass Kote 2 pack epoxy.

The tailplane has been sheeted and the tips added. There will be ply inserts added on the inner edge for toughness and provide a nice edge for the elevators. Again - Kevlar cloth used for hinge material.

Now getting to the tricky bit. I have started planking the rear underside area behind the wing, but this area here is a little confusing. I can detect as deviation from the plan coming.

There are 2 x 1/2" sheet inner cheeks which delimit the area around the exhaust for the tuned pipe shown as F22 on the plan. What is not clear is where the G/F cowling ends and the balsa starts. Don't assume that the curve is the correct line - that is just a cross section - the shaded oval to the right of the photo is the cooling air outlet which I assume would be part of the cowling.

The assembly diagram isn't too helpful - additionally, its a poor scan which doesn't help either

This image seems to show that the two F22 cheeks extend forward of F21 - the ply former shown above but they are not present on the plan - nor should they be as that part is attached to the wing..

I think I am going to terminate the cowl at F21 and build this area with balsa and thin ply and carve it to shape.

More to come

Martyn

[Martyn K]

Not much done last night. Pondering over the tuned pipe outlet - I have now decided how I am going to do that. But while I was pondering, completed the planking on the lower fuselage

I am getting fed up with planking, however, I am quite pleased with this and even more so that there is no more to do

This morning, I have glued the balsa block for the rear fuselage and started building up the area around the tunnel. I'll see how that develops

More to come.

Martyn

[Martyn K]

Progress - but not much

The exhaust outlet area has been built up. I have elected to join the lower tunnel at the rear wing/fuselage joint

The slot for the pipe outlet has been lined with 1/32 ply to add some toughness. It still needs smooth sanding as you can see. An additional cooling hole will be added behind the slot and this will have ducting to direct the air correctly

I have also fitted the Elevator snakes. The elevators are raked so need to be driven separately. I have fitted heavy duty snakes and supported them in three positions down the fuselage using lite ply supports like this.

They shouldn't really be required but at least they will stop the tubes from rattling around. Rudder control will be via a closed loop system

I am considering two elevator servos to provide a level of redundancy rather than a 'Y' junction rod. I can use a pair of smaller lighter servos if I have sufficient space

The other job that I started on last night was adding the upper fuselage sides. It looks quite straightforward on the plan but it was actually quite tricky. The sides are cut from light 3/8" balsa, but need to be cut (bevelled), curved in 2 directions and then bent slightly. So it was lots of clamps and binding to hold it all together

It doesn't look too bad though after the edges have been taken away and the upper side sanded down to the correct shape and size

Top deck next - this is laminated as it gets thicker in a non linear way behind the canopy

More to come

Martyn

[Martyn K]

Progress has been a bit slow.

The upper deck has been added. No problems but a few additional laminations are needed to get the hump behind the cockpit correct. One of the nice things about laminations is that the stripes that are formed when sanding give a very good indication of symmetry. I have also added the top decking above the engine - same method - lots of laminations

Just a few photos.

The top deck and the hump. What has been quite difficult is that the plan refers to parts for which I don't have a cut diagram so its been very much a case of muddling through and test assembly. Hence some of the odd pieces - especially around the cockpit area. The curve around the nose incorporates the engine bearers - which are the dark areas showing. Also needs a touch of filler as well

There is a step here from the bearers to the cockpit floor, hence the join. It could have been done in one piece but my building skills aren't really up to that.

I also have a canopy! It came off the Groovy 50 that I destroyed earlier in the summer. Its not quite the right shape - it should have a sharper entry. I have found a company in the US who can do me a proper Aurora canopy for 9USD, however postage costs may be prohibitive. I'll worry about that later

Finally, I have a cooling air outlet. The inside has been fool proofed, I just need to add some ducting to direct the air outwards

More to come but not for a couple of weeks or so as I am off soon on my holidays until early September

Martyn

[David Oxilia]

Martyn,

You probably know this already but Don at rcaiir.com can set you up with both the belly pan and the canopy. Shipping will probably run you about the same as the parts - perhaps a tad less.

I'll reply re the Arrow tomorrow as I'm out all dat today.

Thanks, David

[Martyn K]

Hi David

Thanks for that, I'll investigate. The canopy looks like it is sorted, I have been thinking about the tunnel but the next job will be to get the wings built, on hold for a few more days until I get the Glass Slipper off the board

Martyn