Jocasta

[Jim Newberry - Nuviation Ltd.]

Hi Folks,

Just thought I would introduce my latest own design project, called Jocasta. The concept is very similar to my Jemima model which was the February 2013 free plan - ie simple, rugged construction from predominantly 1/4" balsa, high wing vintage style, easy to fly model.

I liked Jemima a lot and immediately started to think about how it would work as a longer, leaner version and so I have drawn up some plans for a similar model of 60" span (Jemima had a 54" wing, so we are only talking about an extra 6" but with the same chord to give a slightly higher aspect ratio, straight dihedral and with the option to build ailerons and even flaps into the wing.

The fuselage has been stretched slightly, both in front of and behind the wing and the windscreen will have more of a "raked" look so it will look a little less stumpy - stop me if the aerodynamicist terms are getting too technical!

Anyway, here are some of the early drawings to give you the general idea.

 

 

 

I have the printed plan - not a full version but more of a working drawing to build from, and I had a set of parts laser cut by SLEC - it's a simple enough design and laser cut parts are not really required but I wanted to save myself some time and - having already built two Jemimas with hand cut parts - I felt justified in taking the lazy option!

The parts arrived yesterday and so this morning I fitted a new, lethally sharp, blade into my trusty Swann Morton and set about creating balsa dust.

So far I have a complete fin and rudder, while the tailplane is currently drying on the building board. I tried uploading pictures of the day's progress but the internet is being a bit slow so I'll try again tomorrow.

My first impression on seeing the plan at full size is that this is a lot more model than Jemima - it might only be a few inches larger in all directions but suddenly it seems that there is a lot of it! Construction is broadly the same though, so I'm looking forward to a few weeks of good ol' fashioned aeromuddling.

I'll let you know how I get on.

Edited By Jim Newberry on 10/07/2013 22:45:39

[Jim Newberry - Nuviation Ltd.]

Well I have managed to get one picture uploaded - here is today's progress. Apologies for the poor picture quality, I'll get some proper photographs taken soon!

[riverlandgirl.]

Looking like a very good flyer, judging by the plans. Float or wheel option? It's suprising how the model comes out a different size to what you were expecting! (my last one came bigger than expected....)

Good stuff, looking forward to watching your progress

[WolstonFlyer]

Very nice looking model Jim

Are you hoping to get the plan published?

[Jim Newberry - Nuviation Ltd.]

Thanks for the comments. RLG - I'd like to try making some floats for it, although it will have wheels at first. If I do make some floats they will have to sit further forward than the picture shows - that was really just a bit of doodling to see what it would look like but I think it would make a good looking seaplane. WF - I hope so. I'll certainly offer it to Mr Ashby and see what he thinks.

Starting on the fuselage today. Lovely weather here so I'll be taking the building board outside.

Pictures to follow this evening.

Jim.

[stevejet66]

To top it i reckon a nice fourstroke motor would be nice., Im hoping at some point to get a ben buckle kit for my os35f/s. There nothing like a bit of vintage modelling. Looks good, Nice work.

 

Edited By stevejet66 on 12/07/2013 19:28:08

[Jim Newberry - Nuviation Ltd.]

I agree about the FS engine - I have noise issues at my field so it will have to be electric but I'll make sure it has a few dummy cylinders poking out!

On day two of the build I got the fuselage sides built and the forward formers fitted so it's starting to take on three dimensions and looking good. I have had to leave it alone now and go to work for the weekend but I'll be back with more on Monday.

Jim

[Jim Newberry - Nuviation Ltd.]

[WolstonFlyer]

Hi Jim

Any updates? I would love to build this model.

Cheers, James

[Jim Newberry - Nuviation Ltd.]

Hi WF. Thanks for the interest. I've been working on it - had a bit of a hold up over summer caused by a few domestic issues - nothing serious, just stuff that took up a bit of time. Now at the almost ready to cover stage with all major components built. I just need to make one aileron and a wing tip, then I'd like to take a load of pics before covering starts in earnest. I have some time off work now so plan to have it finished by the end of the month. As an aside, I am turning it into a kit to give to my dad for his 70th birthday next month but shhh! It's a secret! I should have some pics up within the next week so watch this space!

jim.

[Former Member]

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[Former Member]

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[Jim Newberry - Nuviation Ltd.]

Glad to see I'm not the only one who does that, Percy! Actually I didn't know about the length of float in front of the prop, so thanks for the pointer!

Jim.

[Former Member]

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[Jim Newberry - Nuviation Ltd.]

Thanks for the link Percy, very useful.

I have just joined the wing panels together and they are drying overnight - if it's a nice day tomorrow I'll try and get around to dragging everything out of the workshop and taking some pictures (as I promised I would do some weeks ago!)

Remaining jobs are:

1. Making the undercarriage. It's one of those jobs I always put off but then find I quite enjoy it once I get going!

2. Covering and painting. I have yet to decide on a colour scheme.

3. Fitting the radio gear, ESC, battery etc.

4. Making a windscreen.

5. Maiden.

I had hoped to have all this done by now but other things have got in the way, as they tend to. I sent the CNC cutting files off to SLEC this evening, ready to give to my dad as a birthday present, so I hope I got the design work right or I'll be giving him a turkey for his birthday!

Jim.

[Jim Newberry - Nuviation Ltd.]

Well I finally got all the bits together for a picture. The cowling looks a bit "chinless" at the moment as I plan to fit an air scoop underneath for cooling. Once again, I am surprised at how much larger it seems than Jemima. A couple of people commented on the narrow track undercarriage of Jemima so this time I have made the track a good deal wider to improve the ground handling. The legs are quite long to give plenty of prop clearance as I plan to make a pair of skis for winter flying. Anyway, here is Jocasta in her undies!

[WolstonFlyer]

She is looking very good Jim. I really would like to build this one if the maiden and test flight go OK (and you publish the plan).

I tried to suggest her for the 2014 Mass build but people pointed out that the design was not quite ready and not flown yet ... I think it would have made a very good model to put in the voting.

[Jim Newberry - Nuviation Ltd.]

Thanks WF - that is extremely kind of you to have suggested it as a mass build candidate! Hope the maiden lives up to expectations!

[Jim Newberry - Nuviation Ltd.]

Well I have finally got around to taking some proper pictures of the construction before I start covering the model, so here they are...

First up, fin and rudder. While I was having all the parts laser cut, I decided to make interlocking pieces wherever possible. I'm quite pleased with how this has turned out and it certainly speeded up construction no end, the parts slotting together very nicely indeed. In the middle of the rudder leading edge you can see a notch which will eventually fit over the wire joiner for the elevators.

Next up, a view of one end of an aileron.

Conventional wing construction showing cap strips and shear webs. Lightening holes are optional but I always like to have them, especially on a broad chord, fairly deep section wing. They also make it less likely that I will forget to make holes to route the servo leads along later!

More to follow!

Jim

[Jim Newberry - Nuviation Ltd.]

More pictures...

For the wing tips, I made the outline from 6mm balsa and then added curved sections to carry the line from the upper and lower wing surfaces to the tip. When I built my Jemima model, these were simply triangles but this time I felt it would look neater to make them semi elliptical. The sub spars run underneath the cap strips on the wing ribs and so will not be visible under the covering.

Although intended for a scale model, these 4" cub wheels should do the job nicely!

The forward fuselage formers have been laser cut from 6mm balsa, while those in the rear end were made up from 12mm x 3mm balsa strip.

F1 is made from 3mm birch ply. Large kidney shaped hole makes for easy access to the ESC wires and allows cooling air to flow over the hot bits. Fuselage sides are 6mm balsa, underside is 3mm balsa, grain crossways.

The battery bay allows easy access for lots of different size packs. I'll see how much I can get away with in terms of capacity - it woujd be nice to be able to fit a battery pack large enough to give plenty of flying time and at the same time avoid needing ballast to get the CG right.

[Jim Newberry - Nuviation Ltd.]

Last set...!

As the fuselage sides are more than 4" deep, they would not fit onto a single sheet of balsa so had to be split lengthways and then rejoined. The formers each had tabs which located into slots laser cut in the fuselage sides, imparting additional strength and making assembly very quick and easy. In this picture you can also see the 6mm square holes which accept balsa rails to support the battery and servo trays. As ever, I was impressed with the quality of the laser cutting from SLEC which meant the parts just slotted together square and true with very little effort to ensure a straight fuselage. Note the holes for the wing dowels - I plan to use rubber bands to hold the wings on. For sport models I always thing rubber bands are the best method unless some other means is clearly better (e.g. for fast or aerobatic models). It's quick, simple, cheap and robust. The oval windows will be glazed on the inside.

General construction view. Laser cut 6mm balsa forward fuselage sides, 6mm square built up balsa aft of the wing trailing edge. Some Jemima builders complained of a weak spot behind the wing and so the half-elliptical shape to the fuselage sides aft of the wing seat takes care of this with no tendency toward cracking being evident. If you look closely you can see three ply plates on the underside. The front two will take the saddle clamps for the undercarriage while the third will be unused initially but may form the aft hard point for float mounting at some point in the future. Motor is a 4-Max unit, as usual, with 5 degrees of down thrust.

Jemima veterans will recognise the tailplane - exactly the same planform but flat plate this time. Slightly more flexible, having lost the stiffening effect of the upper spar, but hopefully strong enough! While I was having the other bits laser cut, I decided to have a bespoke leading and trailing edge made with rebates to accept the 6mm square balsa sticks.

That's all for now folks! Colour scheme has been picked out and decals ordered - details to remain a secret for now (although if you look closely at the pictures above you may just spot a clue...)

Jim

[Jim Newberry - Nuviation Ltd.]

Well apologies folks, this model was supposed to have been finished, flown and put to bed months ago but I've been a bit distracted - I put a lot of effort into turning Jocasta into a kit for my dad and then I got a bit, well, Jocasta'd out if you know what I mean! Winter set in, the shed got cold and with one thing and another Jocasta got put to one side. I'm back now and hope to crack on with things over the next few weeks ready for a spring maiden.

Today I got busy on my lathe and turned up a couple of dummy cylinders from aluminium. They will be poking out of the cowl to make Jocasta look like she has a flat twin engine hidden away and I must confess to being quite pleased with the result. SWMBO is out tonight so the shed beckons once more. Tomorrow and for the next few days I have to be at work but a big push will follow, I promise, and Jocasta will be flying in no time.

Jim.

[WolstonFlyer]

I like the dummy cylinders Jim, they will look very nice installed on Jocasta Do you think you will release a kit of this model?

[Jim Newberry - Nuviation Ltd.]

Thanks WF. I have considered the possibility of releasing a kit of the model, having already produced one for my dad, but the reality is that it's just not viable. The costs involved would make the kit more expensive than, for example, a Super 60 - and that's before any sort of profit is considered. I can't imagine enough people would be willing to spend that amount of money on a Jocasta kit to make the exercise worthwhile. I'll offer the plan to RCM&E and if they don't want it I'll be happy to make a small number of plans and parts available to forum members.

Just need to get on and finish the thing now - it's taken me far too long!

Jim.

[Jim Newberry - Nuviation Ltd.]

Well folks here - finally - is Jocasta. All complete and awaiting the maiden tomorrow. I really am quite embarrassed by the length of time it has taken me to build this model but the build has been interrupted a few times by other projects. Hope you like it!