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Building Bubbles


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 Hi All!

This will be my first attempt at building a model from just a plan. My only previous building experience was putting together a kit WOT 4 a few years ago. From what I remember that wasn't really building, more like assembly, such was the excellent quality of the kit (and no plan either).

I've chosen to build a 54" span sports flyer designed by David Theunissen called Bubbles. I found the plan at www.flyelectric.ukgateway.net. This site contained model plans in PDF format, chopped up into A4 sheet sizes, ready for printing. There was also many photos of example Bubbles models that had been built by various modellers from all over the world.

Bubbles is essentially a model similar to a Wot 4 but with built-up wings and has a general light weight design that is more suited for electric power. I intend to power it with a motor initially but I must admit that I quite fancy converting it to glow at a later date, depending on how it flies. All that is a long way off because although is it a simple design – I'm not going to be a fast builder.

Progress so far has been to buy a fair chunk of balsa in various sizes and over the last few days some of this balsa has been reduced to a stack of ribs. So there you are – I'm committed.
 
This project will be quite a big learning curve for me so I'm taking things one step at a time.
 
I'd love to hear from anyone who might have built this model already.
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Chris,
 
I built Bubbles some years back - you'll find pics of it on David's site - and only recently had to retire it because of pilot malfunction (ie. I crashed it!)
 
Many happy hours of faultless performance.  Progressed from 12 Nicads and 300 watts to 3S li-po and 500 watts over the years.
 
I still have the framework for the wing, so it may earn itself a new fuselage sometime in the future.
 
Highly recommended!
 
tim

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Hi Tim,
I noticed your model on David's site. I like the covering scheme you used - it really looks the business. 
 
I think the plans have changed since your model. It looks like it's been simplified such as doing away with the ladder fuz structure and replacing with sheeted balsa & longerons. Also, the ailerons in the latest plan that I have, although still built-up, do not show the cross brace design that your model has.  I'm undecided if I should go with built-up ailrons or cop-out and go with solid ailron stock.  I'll probably go with the solid ailerons but no doubt I'll take a weight hit by doing this.
 
While pondering  that, I've cut out the fuz sides and also glued the laminated spruce/balsa spars - weighted down with 2 cases of bitter.
 
Chris
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Chris,
 
When the design was first published we were still in the days of heavy Nicads and so weight-saving in the airframe was vital. I gather that David has moved with the times, and the virtually unlimited power we have these days has let him simplify the fuselage construction.
 
Must admit though, I rather like the lattice structure!
 
Those criss-cross ailerons and elevator were my own idea.
 
tim
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Hi Paul,
 
Sadly there's very little progress to report as I've been busy with work committments .  I hope to be able to get really stuck into it in the next few weeks 
 
I'm considering deviating from the plan slightly where it calls for 1/64" ply doublers to strengthen the fuz from the fire wall to just aft of the wing trailing edge.  I'm going to try using 3mm liteply for these doublers intead, with a good part of the central area removed to help bring the weight back down.  Obviously it'll be still heavier than the 1/64" ply version but I'll keep the increase as low as possible.
 
I've decided to attempt to fabricate some built up ailerons. Hopefully they'll end up pretty straight. I figured that if I mess up I can always buy some solid balsa aileron stock.  I must admit that building a good set of wings is the area that I feel least confident. 
 
It's interesting to note that most of the pictures of previously built Bubbles show them covered in translucent film - showing off their internal structure. I think I'll be hiding mine behind the good old opaque variety.
 
Chris.
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I have now cut the 3mm liteply doublers and glued them to the fuz sides.  I've also cut a couple of the formers 'B' and 'C', all of which can be seen (dry fitted) in the picture.

 
The wings are still just a pile of ribs at the mo, and my day job is busy again so progress will remain slow for now at least.  Like I said at the beginning- this won't be a fast build, but if I keep chipping away at it...
Chris
 

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