Union Models

Hi all,

Some time ago I bought a MK/ kato Aurora 60 kit. To many of you the Aurora needs no introduction, its gracious sleek looks, certainly make the Aurora stand out.

I'd looked at the kit contense many times putting the kit away for ' One day I'll build it '
Well that time has come, and the lovely Aurora made it's way into the workshop.

My intensions were to utilise a foam wing and tail, instead of the balsa built up construction the original kit utilised. For power, I choose to use a YS91FZ combined with a Hatori 580 flexiable Header and Hatori 674 tuned pipe.

Attached is a picture of a electric Parkfly Aurora made by Union Model Co. sadly no longer available.

Mike

rainedave

My Feedback: (1)

Man, you have no idea how much I'd love to put a Norvel in that park flier!

Keep us posted on your kit build.

David

hrrcflyer

Hey Mike,

A build thread on a classic like the Aurora would be awesome. Would you consider doing one? I, for one would follow along like a lost puppy...

Union Models

Hi Guys,

Yes I'll be doing a build thread.

Firstly I'd like to thank ATLANTA 60 ( Chuck ), also BOOTALINI ( Jeff ) as they have both been of valuable help with this project.

You may like to follow BOOTALINI build thread of an electric Aurora. My build thread will not be as detailed as Jeffs. http://www.rcuniverse.com/forum/m_49..._1/key_/tm.htm

For those of you who have never built a MK / Kato kit, it has to be the best quality / workmanship of parts I've ever seen. Everythings well cut, machined parts, bagged and a well drawn plan.

The first thing that struck me of a possiable problem, is how tight fit a YS91 would be. My kit was for the Aurora 60, intended for a YS60 two stroke. I soon discovered with corresponding emails with ATLANTA 60, that MK also produced a Aurora 90. This is basicaly exactly the same size of airframe intended for 90 sized four stokes. The only difference being is a realinement of the fuselage firewall.

Pictures courtesy of ATLANTA 60 *** Please do not ask ATLANTA 60 for this kit, it's NOT FOR SALE ***

Union Models

To start the build, I usualy constuct the fuselage first. This is like any conventional model fuselage, consisting of balsa sides, strengthened with 1/16" plywood around the nose.

The engine is mounted on a beam mount, in conjuntion with a MK soft mount, other wise known as a ' floating mount '. This is constructed first, then glued into the fuselage, along with the liteply and balsawood formers.

It struck me as to how much block and sheet wood is involved in the fuselage construction. With a balsa plane, a great deal of carving is to be done to give the Aurora is nice curvey looks. One neat item included in the kit, is a liteply fuelage template, which is a great aid in knowing how much to plane off.

The fuselage was jigged to ensure its staight, we all know bent models don't fly well as they should.

Weight of the fuselage without engine bellypan, and retract is 515g ( 18.2 oz )

Union Models

With most of the fuselage complete, It's time to move onto the tail. As mentioned earlier, I intend on making a foam wing and tail. The original utilised a balsa built up structure, sheeted with 1/16" balsa.

The tail cores were hot wire cut from high density foam. As the quality of the wood in the kit was very good, I decided to use it to skin the foam cores.
On previous models with foam cores, I've used a vacume bag and epoxy to attach the skins. Some may argue the toss as this is overkill on pattonships, but it's worked fine for me in the past.

Prior to laying up the balsa skins, I gave the skins two coates of sanding sealer, lightly sanded inbetween each coat, to prevent the epoxy from soaking into the balsa skins.

laminating epoxy is applyed to the balsa skins, removing as much as possiable with an old credit card. It's important to remeber not to apply too much epoxy, as this only adds unwanted weight. The skins were offered onto the foam cores, into the plastic bag, then the vacume applied.

Once cured, a very strong light weight tail is a pleasing result. Next the balsa leading and trailing edges were added, shaped, tail half's jigged to ensure there straight and joined together, finishing off with a epoxy fibreglass bandage. Final weight of the tail was 110g ( 3.9 oz )

Union Models

On with the wings. Temperlates were cut from 1/16" ply drawn around the original kit supplied balsa wing ribs. Again high density foam was used for the cores, cut with the aid of my father.

Two liteply false ribs were let into each wing core either side of the retracts. These offer more strength for the retracts, as I my flying site is a well mowed grass stip. We all know retracts don't always fair well to grass strips ! A liteply box with hardwood beam mount is also let into the core for the retract mount.

The aileron servos boxes and wires were hollowed into the core with a small hot wire cutter. I drew onto tracing paper where they were located in the wing, as once the wing is skinned, tring to locate them can be troublesome.

As with the tail, the wing cores were skinned with the kit supplied 1/16" balsa and vacume bagged.

One thing that struck me, was the wings were not as light as I would have liked. This was due to the high density foam, also the balsa kit supplied skins were a little heavier than if I were to use contest balsa. Despite this, I proceeded on to cutting the retracts and aileron locations lining the retracts and boxes with 1/16" balsa.

The wings halfs were then joined together. With two incidence gagues at each wing tip, the wing halfs were out of aline by 1/16" at the root, something I could live with.

The ailerons were cut out of the cores, faced with medium 1/4" balsa. I was kind of amused that a foam balsa skinned aileron weighed exactly the same as the kit supplied preshapped solid balsa aileron. The solid balsa kit ailerons were used instead of the foam ailerons, as the aileron horns would be a solid mounting.

Finishing the wing required the epoxy bandage around the centre section, balsa wing tips and wing mount to be glued in place.

The all up weight of the wing without retacts and servo is 738g ( 26 oz ) Humm.... I think I should make another wing []

Union Models

While I debate on making a new lighter wing ( I welcome your comments regarding if I should do this or not ), it's onto cutting the belly pan.

I took the opportunity of making a glass fibre mould incase I accidently break the original or decide in years to come, build another Aurora

The mould was made from polyester glassfibre resin, 163g cloth with chopped matt strand cloth. Lucky for me with Atlanta 60 help via email, the mould worked out perfectly.

I made a tempory bellypan from one layer of 163g cloth. This was very flexiable. This was used to cut away until the belly pan fitted around the YS91. Once happy, I drew the cutout locations of the cylinder head and exhaust onto the original kit supplied belly pan.

It's a tight fit, I'll tell you with a YS91. Those of you who have experience of the soft mounts know the engines rock quite a lot on tickover. therefore more machining is required so the engine will not catch on the bellypan at tickover.

So here we are, I'll keep you posted as I progress with the build. Till then I welcome all your comments, constructive or not, we can all still learn something.

Atlanta 60

My Feedback: (18)

Fantastic!!! Thank You sooo much for sharing your photos/experience with us!! Your workmanship looks Awesome!! This is very inspiring for me in particular since the Aurora is my #1 all time favorite...I hope to join you soon in getting one of these baby's in the air!!

(edited: Didn't see the weight of your wings in earlier post)
You mention using high density foam for your wing cores and now you feel your wings may be a little heavy??
I know light wings are important and rolling maneuvers are really effected by moment of inertia...Other than that I'm defiantly no foam wing guru as I'm just getting started messing with them myself...To me your's seem like they are really nice...26oz seems light to me.. (I wonder if your just playin'..What would you expect them to weigh??)

I have yet to sheet a set of wings but I have a few sets that are already done by the factory or another builder that I bought airplanes from...I thought I'd weigh what I have and maybe it would give you some idea where you stand as far as weight of your wings...These are all one piece wings which are in similar stage of construction as your's appear to be...I know this will not be super accurate but at least you will have a ballpark idea of what other foam wings are weighing in at...


Modeltech Calypso wings (Factory Sheeted which I joined):
wingspan: 64"
wing area: 730 sq in
weight of my wings: 24.8oz (note: no retract's..switched to fixed gear and patched holes)


Philips Aircraft Conquest IV: (Sheeted by other builder)
wingspan: 65"
wing area: 790 sq in
weight of my wings: 30.3oz (finished very similar to your photos)


ZigZaw Atlanta: (Factory Sheeted..Joined by another builder) (note: retracts moved from factory location to use a t'dragger)
wingspan: 65.3
wing area: 775 sq in
weight of my wings: 28.4oz


Desire 60: (Sheeted by another builder..Not joined yet..Very Very light wood used!! These wings look and feel extraordinarily nice!!) (not joined yet)
wingspan: 64"
wing area: 850 sq in
weight of my wings: 21.1oz (plus materials to join wing halves..I est 23oz) (Makes me a believer in using Contest Grade Balsa, Light foam & Honeycombing the cores)


The Aurora has a wingspan of 67" with wing area of 775 sq in...With your weight being 26 oz I'd say your in Awesome shape!!

Your wing looks Beautiful!! As does the rest of your airplane!!

You could always do another set of super light wings later if you wanted...Maybe do some honeycomb cutouts and all that neat stuff... he he

Just My Opinions..Again I'm no Expert!!

I'm Really Jealous!!

Chuck

dhal22

i have actual proof of the advantage of a balsa skinned foam wing vs a built up balsa wing. over the weekend i crashed a .45 size speed plane full speed nose 1st into the ground. the plane left a 8" deep hole but the plane essentially survived. the sickening crack i heard was only the wing momentum tearing a few pieces of the plane off between the wing and the fire wall. the wing survived completely intact. what i thought was going to be balsa shreds ended up being a few rebuilding hours to get the plane flyable again. no way the wing survives if it's all balsa.
david

Atlanta 60

My Feedback: (18)

Did you use any sort of "Dihedral Brace" ?? (ARF Term I suppose..he he)

Or did you just join the halves and then glass the center section??

Thanks..

Chuck

dhal22

who? union models or me?

david

Atlanta 60

My Feedback: (18)

I was curious what Mike (Union Models) did on these wings...But I would welcome anyones comments cause I'm trying to learn...

My Desire wings are the next set I have to join..The drawings do not really address that particular item which leads me to believe you don't put a dihedral brace in there...Or it may be a given building technique and your suppose to know and take it upon yourself to make a dihedral brace?? (The cores do not have a slot cut)

My new AztecAir LA-1 calls out an 18" Dihedral Brace and then an additional 5" (1/8" ply) doubler in the center...So that leads me to believe a Dihedral Brace is important...

I'm just a little cornfused is all...

Would like to know what others have done or are doing...

I like the addition of the lite ply false ribs for the retracts cause I'm flyin' off grass too...I'll incorporate a structure similar to that into any wings I build up...I can't do much about the already completed wings...But I'll stash that info for later use..

I'll also be interested to see your method of cutting out the ailerons cause I gotta do that on the Desire too...For some reason I'm Skeered I'm gonna goof that up...Don't know why I'm intimidated buy that process but for some reason I am??

Thanks..

Chuck

propbuster

My Feedback: (1)

Chuck, What I do is, run the wing cores (in their shucks) through my table saw to make slots to accept lite ply braces. After skinning the wing halves, just apply epoxy and slide the braces into the slots when you are joining the two. No glassing of the center section needed!

Union Models

With regards to joining wings, In the past for a built up balsa wing I've always used some sort of plywood brace. My last two patton models utilized foam wings. The wing halfs were joined together with PVA wood glue and a 150mm wide glass bandage of around 163g cloth and epoxy. The models are still flying today.

The Aurora wings were butt joined with PVA and a epoxyed glass bandage.

For cutting the ailerons, I use the same method as PROPBUSTER, place the wings in there outer cores, then run them through the bandsaw. This way you can be sure the leading and trailing aileron edges are straight.

Thanks ATLANTA 60 for giving some kind of comparison on the wing weights, I feel a little more at ease

Mike

Atlanta 60

My Feedback: (18)

Awww Shucks...I should have thought of that...

Thanks allot for the info fellows!!

Have Fun...

Chuck

flywilly

My Feedback: (121)

Hey Union Models,
Great looking Aurora! Your wing weight is acceptable as you've seen from the data above. If you were competing at the FAI F3A world championships then, yes, a lighter wing might give you a little edge. The effort involved in shaving a few ounces of weight is considerable (honeycombing, very minimal application of adhesive, carbon fibre reinforcement, etc.) may not be rewarded with noticeable flight improvement. I was obsessed with saving weight (building competitive pattern planes) back in the 80's & 90's, but now I fly mostly for my own enjoyment; so straight and 'acceptably' light are my construction goals (no more honeycombing!!!).

-Chuck,
I've never used a dihedral brace constructing a foam wing, just the traditional butt gluing the cores then reinforcing with 6" wide fiberglass cloth (4-6oz cloth). That's about 30 pattern wings. I've had one failure at the center section (details in a moment) and that includes several high speed vertical 'landings' (ok crashes...) The wing that failed at the center butt joint was on a Mistress. I was flying in 105F temperatures and had flown several flights consecutively. There was very little clearance between the bottom of the pipe and the wing - actually to get the bellypan to fit I had sanded a small trough down the centerline of the wing. At the end of the 4th flight as I flying past to check that the landing gear was down I turned away from the runway and saw the wing slowly folding up. I tried to roll inverted, but was too low. The impact speed was pretty low, but the damage was pretty extensive to the fuselage. The wing had folded because the epoxy used on the center section reinforcement had softened enough to allow the failure - it was still soft when I examined the remains.
Regards,
-Will

Atlanta 60

My Feedback: (18)

Thank You Will!!

Sounds the epoxy used on your failed wing must have reached it's Tg (glass transition temperature)...That's a bummer... [&o]

Union Models

So we continue.... Firstly thankyou to all who commented regarding my query on the wing weight. My intentions are to use this model for my own amusement, built for nothing more than nostalgia, I'll continue the build with the wings presented here.

Fin. This is quite simple, consisting of pre cut sheeted sides of 1/16" balsa located over a diecut fin ribs. The rudder is preshaped solid balsa, minimal time required to build with cyno.

Next a preshaped block tail faring is tacked in place with a draop of cyno along with the fin. One nice feacher with the kit is a 1/32" ply strip let into the fin faring to be used as a centreline guild.
To remove the majority of balsa on the fin fairing, I used a dremal drill with abrasive wheel disc. The contors to blend into the fin were carved with rough sand paper wrapped around a jam jar. Light sand paper to finish off.
The reason why the fin fairing was tacked on was to enable the MK dual belcrank to be fitted later, forward thinking needed in some cases.

Union Models

The retracts I'm using are Romair. One slight differnce in the nose wheel mounting I came across in comparison to the kit ,was the original MK retracts are mounted directly to two thin hardwood beams. The Romair nose retract requires a slightly modified mount. This was quite simple, using a beech hardwood block, held in place with JB Weld epoxy.

As you will see, there isn't much room with the YS header pipe next to the retact, but they don't interfear with each other.

Finally for today the wing retaing bolt is epoxyed in place with JB Weld.

Attached are the belly pans mentioned previously. A mould is shown furthest away, next is a light flexiable temperlate used for locating cylinder head etc, lastly the original belly pan supplied in the kit.

Mike.

KLXMASTER14

That's some nice work there, my friend. I'm really enjoying this build thread, please keep up the good work.

Enjoy,
Robert

Atlanta 60

My Feedback: (18)

Agreed..Very Nice!!

Union Models

Thankyou all for your kind comments, I'm pleased your enjoying the build thread as much as I am building the model.

Finishing off the nose retract. This required a cut out for in the belly pan. Another job for the tempory belly pan I made. You will notice the masking tape stuck around the nosewheel cut out. This was where I cut too much off the belly pan, the masking tape are the final cut lines.
Just as well I didn't go ahead and work directly on the kit supplied belly pan, as the nose wheel with my model is 1/4 " to one side where the original kit should have been. The reason for the offset nosewheel in the kit, was to miss the manifold for the 2 stroke 60 engines.

Next to finish off the cockpit. The canopy was roughly cut to size with a dremel drill and cutting wheel. If you cut the cockpit with scissors, it will simply crack the plastic.
To help contour the cockpit canopy to the fuselage, rough sandpaper is wrapped around the fuselage, with the canopy slid back and fourth. Becareful here, if you get carried away as I did, the sandpaper can sratch the canaopy in places you dont want. Nothing too serious lucky for me.
The cockpit floor is made up from 1/16" balsa, one neet trick I learned from BOOTALINI ( Jeff's ) electric Aurora, was to let the cockpit into the fuselage. Our trusty freind Mr Dermel was once used to carve a shallow groove into the fuselage using a abrasive disc wheel.

A couple of coates of sanding sealer, sanded in between helps the dope to adhear to the balsa fuselage. Light weight tissue was used for the covering, along with a couple more coates of thinned dope, finishing off with a light spray of cellulose grey paint.

While on the subject on paint, I'm pondering on how to finish the model off. My previous pattonships utilised a painted fuselage with filmed wings / tail ie oracover. For the this subject I was thinking of covering the fueslage in lightweight glass cloth 20g / m2, the wings and tail with light weight tissue and dope. For the paint, cellulose with a 2 pack clear coat to fuel proof.

Would just using 2 pack as the final colours be a lighter finish than cellulose paint, then a 2 pack fuel proofer ? I welcome your comments.

Mike.

Atlanta 60

My Feedback: (18)

Was wondering how your build was going?? Hope all is well!!

Union Models

Well work on the Aurora is still ongoing. My concerns the wing was too heavy got the better of me, currently a new lighter wing is being constructed from 3/4 lb foam and lighter balsa.

Mike.