Build Log Ivan's Auster

[Sopwith Mike]

I've had the plan of Ivan's Aiglet for a year or so, and have always been an Auster fan. And have built four seaplanes in the last 18 months (Ivan's Minicat, my OD Bombardier/Canadair CL-415 and a little Depron Sopwith Pup-on-floats and a last-minute conversion of a Depron Supermarine Walrus from land to sea-based) so I need a plane with wheels. I have most of the hardware, so it's just balsa to buy.

I'm hoping to build it as KZ 1705, a New Zealand J/5 Auster (detailed at http://forum.keypublishing.co.uk/showthread.php?t=41688) which has the option of a float chassis or a normal wheeled UC. It seems obvious from the plan that either option can simply be bolted to the fuselage, using the same attachment points. The J/5 had the 36' span wing, so Ivan's plan will have to be stretched by about 9.5" wingspan - not too difficult.

My MiniCat repairs are almost finished and she should be flying this time next week, when I will pin down the Auster plan and start what we laughingly call "work".

More in a few days time,

Mike

[LukeZ]

Alright! I finally caught one before it was half-way over!

I'm signing up for what will surely be an enjoyable ride.


Luke

[pentaxman]

Way to go Mike.

How long do you estimate it will take for you to build this one?

Any chance for the BIMBO event?

[Sopwith Mike]

This one will definitely not be ready for the end of May! I would guess that 5 months is on the cards. I do a lot of dinghy sailing in the summer, so build much more slowly than in the winter.

Sailing today!

Mike

[Sopwith Mike]

When I was at school, an Auster landed on the playing fields and some of us got a chance to crowd round and touch it while the pilot was - I don't know; having a pee, visiting his old school, reporting to the Headmaster - anyway the memories that remain are the drum-like nature of the aluminium-doped covering and the fragility of the thing. We were chased off by authority after a very short while!

Trevor and I took a trip to the Museum of Army Flying the other day, where they have three Austers (Taylorcraft, AOP 6 and AOP 9) on display. The Museum is about an hour from Christchurch, in the grounds of the Army School of Flying, Middle Wallop, and is very good value for money (only £5 for OAPs!) but the exhibits are not as accessible as one would like and the lighting is not very good either. They have an historic flight and an Auster AOP9 was in the air when we got there, and taxiied around under the cafe windows while we were hurrying down our lunch. Anyone wanting scale detail for a very wide variety of Army aircraft could spend a happy few hours there.

The photos are not brilliant, but you do get a very good idea of what an Auster is like and how they look in brown and green (not great, was our verdict, and will look much better in aluminium dope). The photos are just a small selection - anyone wanting a specific view, please ask: you never know, I may have just the thing.

Perhaps the biggest scale deviation in Ivan's plan is the lack of flat plate tail surfaces. To scale, they would have to be made from 3/32 square and would be unacceptably delicate (or warped too badly for flight) but a 3/16 sq frame covered in Litespan should be relatively easy to make. The tail surfaces are wire braced, which just adds to the temptation to make them "properly".

More thoughts on scale fidelity later.

Mike

[Trevorh]

Originally Posted by Sopwith Mike

More thoughts on scale fidelity later.

Never mind the colour scheme, how's the model going? Some photos of freshly stripped balsa, at least

[Airboatflyingshp]

Didn't get Ivan's plan for this one but I already have a AOP7 a 72" span for glow originally and a Fibreglass cowl, nice subject,more character than a Cub or Cessna.

[Sopwith Mike]

Stripped balsa eh? Trevor is only saying that because I borrowed his stripper last week!

Well, here we go again.

I normally start with the fuselage, the most interesting bit, but the tail seemed a good place to begin, and if it turns out that a scale-ish flat plate is not suitable, well, it has only taken a couple of days out of the build. It’s a very simple structure of 3/16th and 1/8th square balsa. The spars are cut for hinges before building starts and lined up accurately over the plan. I always build the tailplane and elevators as one part and separate them for sanding. The tips are laminated: this is a well-known technique, but here is how I do it. The LE and TE are trimmed off and an internal 1mm ply strip is glued to them and the ends of the spars. The form of the bend can be adjusted by eye (on the left) or by a set of pins (on the right). Three strips of 1/16th are wetted then glued up and squeezed together and pinned round the ply inner. This method does away with having to make a separate former.

After the glue has set, the outlines can be sanded "half round." The tips are easy to sand because the grain all goes in the same direction and the LE and TE just need a few passes with a razor plane and then sanding to section. Before covering, I treat the edges of the structure to some Rustin's water-based clear varnish to bring up the grain, which is then sanded off: very necessary if using Litespan.

It just needs some small blocks for the hinge positions and the scale rigging points, then the covering can start.

Now you can't say that's not progress!

Mike

[pentaxman]

You are right, that is progress indeed.
Looks like one really great start.

I could do with the whole month off work so I could get the MiniCat done but that is not going to happen so it will not be around at the end of May.
Shame really but never mind.

[LukeZ]

Nice trick Mike with the ply on the laminated outer edges, thanks for sharing, and I will have to try that on my next project which calls for laminated tips.

Ah well PT, you'll want to save something for next year anyhow!

Luke

[pentaxman]

I doubt I will wait until next year Luke, I would guess it will still be built this year depending on the flying weather.

[roffe_ek]

I`m a beginner when it comes to rc plane construction. I have also started building my Auster Aiglet. I posted a few pictures at mountainmans thread. I find the technique for building the tailplane very interesting. I have wondered a lot about how to build the tailplane, it is described in Ivans plan that the ribs for the tailplanes should have a symmetrical airfoil shape. It would be difficult to assemble the tailplane over plans if you shape the ribs and spars first(I guess ), to me it seems that you have shaped the ribs after you have built the tailplane is that correct? what do you eventually do to make the shape of the tailplane as a symmetrical airfoil after assemmbly?
looking fowart to see more of your building.
Best
Eystein

[Sopwith Mike]

Hi Eystein, and welcome!

The tailplane and fin/rudder of the Catalina are the same basic symmetrical section construction, and so I presume are all his other models. The way I built the Cat tail was to shape the elevator and tailplane spars off the plan (tapered along the length but not chamfered). If you have a look at my Cat build at http://sopwithmike.mudefordsc.org/ht...lina.html#Tail
you can see how I did it. It's important to work out the thicknesses of packing you need to keep the spars, LE and TE at the correct height. And yes, I do use rectangular section ribs and plane/sand them to shape after taking the build off the plan. This makes the build much easier.

The reason I'm going for a flat plate for the Auster is that it is such a feature of the real plane that it will (I hope) look a lot better than the symmetrical section.

Mike

[LukeZ]

Hi again Eystein. If I may be so bold to intrude on Mike's thread, I think most people do it as Mike described, and as you supposed, sanding the airfoil shape into the ribs after they've been attached to the spars. This works quite well. However I've managed to cut the ribs to shape first and still have success, but it does involve propping the bits up to the correct height.

The more important consideration to my mind, especially on those planes where the horizontal stabilizer has any dihedral to it (not the Auster), is to somewhat disregard the plans when it comes to the stabilizer spars (actually, for the wing too). The inaccuracies involved with paper, hand-drawn plans make these parts often quite incorrect if cut to the plan. It is much better to take the measurements of what the designer intended, and then cut your own pieces with a straight-edge and ruler. I actually do this for the ribs as well, so that I am certain they will fit the spar (both for the vert and horizontal stabs as well as for the wing). This will save you much trouble in the long run. For the vertical and horizontal stabilizers ribs, if you really want to get into it, draw all your own rib "halfs" on paper, then fold them over and cut them out so you have a perfectly symmetrical rib. I can tell you the ribs on the plans are not symmetrical by and large.


Luke

[Sopwith Mike]

Seconded Luke, it's all part of the fun of building from a hand-drawn plan! I think the thing about all plans is that they are inspirational, and if you are inspired by Ivan's plans and his choice of subjects, there are lots of builders who will very happily tell you how they made theirs work.

Luke - did I hear that Ivan was thinking of coming to England next year?

Mike