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The Atom Bomber

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It would be rude for me not to have a go at this years Mass build so here is my attempt,I hope to get it finished this year!


The Atom Bomber is a 1.5 times bigger Atom which will have bomb bay doors to give projectile dropping capabilities! I started from scratch with the drawings rather than copying the construction of its smaller brother. Mainly because the bomb bay needs to be around the CG so as not to disturb the balance, also  the need for bomb bay space was very limited so it will be a little fatter.

So the sloping mast has gone and I have moved the servos to the rear.


I have made a start today on the servo carrying formers/ mast mount, which is made up of a lite ply and balsa sandwich very much like the original.

A few snaps of my efforts:

4 servo holes, 2 for the head and a servo each for the bomb bay doors.




10 x 13mm spruce mast used to jig the parts together.


6mm cross grain balsa used as an infill






Edited By Richard Harris on 03/06/2015 22:49:16

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Not sure what blades will be used as yet, will work it out once I have a rough idea of its AUW.

A little more done on the bomber this evening, trial fitted the servos whilst it is easy to work with. A bit of fettling with a file had them sitting nice and snug, head servos are TP MG996R's and bay doors are Corona CS-929 MG's.



The top of the bomb bay slots into the main formers like so


With another former slotting to the front of it


Slotted into the front of this is the 6mm balsa battery tray, with a lower former added



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I hadn't thought of loading from the top, loading from the underside was my initial thought with perhaps a Go Pro pointing directly down wards filming the bomb release and hopefully the direct hit!

Anyway, I have done a little more this afternoon starting with the fuselage sides made from 6mm balsa with the main former positions being marked on each.


The sub assembly simply slots and is glued into place onto one fuselage sides


The rear boom holder works along the same lines as the smaller version except this unit is sized to take 10mm square hardwood booms, in filled with scrap balsa. I also added hardwood servo bearers for the mounting screw to bite into.


Sizing up the booms


Then adding the top 3mm thick ply wood top to complete the sandwich


This assembly slots into the rear former with the fuselage side completing the square mounting hole, may well make this removable with a couple of bolts securing.


The bulkhead was then started, it is made up of 3mm lite ply laminations


The UC has been kept simple and removable, being made from one length of 4mm piano wire it simply slots snug into the bulk head and will be clamped into position. Still plenty of room above it to mount the motor.



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Bulk head slots nicely into place and has been glued with epoxy, triangular section was then added fr extra strength.


Noting that the vertical triangular balsa has been left 3mm short


Leaving room for the final former to slot into place



Had to scratch my head a little on the best way to make the bomb bay doors and decided to curve some 3mm balsa sheets, I first soaked them and left them in boiling water until it went cold which took about an hour. Then the wet sheets where taped around a suitable cylinder around the correct diameter and left to dry outside.


Once dry they held their shape pretty well.




Adding quadrant formers to match the inside bottom of the formers which were sanded square with an over hang left on each end.





Test fit on the fuselage to confirm they are close enough



You will see there were a couple of curved off cuts, I will use these to plank the front lower section of the fuselage but that will wait for tomorrow.





Edited By Richard Harris on 14/06/2015 18:42:31

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Quite a productive couple of hours this afternoon.

Using the curved 3mm wood I managed to plank the front lower fuselage, it was certainly easier than using strips of flat and no filler needed!


To the rear, this has been in filled with soft balsa block


Full view


And with the doors fitted


And open



I was in two minds whether to make the canopy from blue foam or go with plastic bottles like the smaller version. The problem I have is that a canopy will be big and I don't know of a suitable bottles that are big enough. But then a thought, bombers generally have a pilot and a bomb aimer. So I will make a plug and cut it into two, then hopefully I can shrink two 3 litre cider type bottles over each and they will match up, well at least that is the plan as it stands! I have made up a plug from balsa, I have made a start but it still needs a lot of sanding.



Sat next to its smaller brother



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Looks pretty cool and a couple of ideas there I like (and will be pinching) wink

Was actually talking to myself last night painting the Cub in the garden when I realised the young girl living next door was outside having a smoke, probably giggling to herself at my inane conversation! I think I'll avoid talking to her for a while! blush

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Thanks for the kind comments, Greenacres will be here before we know it! how time flies



Absolutely nothing wrong with talking to yourself, we all do it don't we Rich, yes Richwink 2



I sanded the main plug down to something near then cut it in half, added some extra balsa to give me a little extra to trim up. Front canopy is from a 2 litre pop bottle and the rear from a 3 litre cidar bottle, they have turned out ok but I will probably do them again as I am not really happy with the shape and finish of them. That said I think it will work.

Will have to go for a run down by the canal and scour for some more disposed bottles!!





Edited By Richard Harris on 18/06/2015 13:33:38

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Camera trickery!


I am unsure on the blade dimensions, this will be calculated once I have a better idea of what it's AUW will be.

I managed to pick up a few bits and pieces yesterday from Weston Park but not a motor as expected. Gone are the days of show bargains I'm afraid, well, for what I was after any way.

Should be able to grab a few evenings this week and crack on some more.


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I made up the tail boom this afternoon, pretty much in the same way as the Atom just a bit bigger. Added some soft balsa blocking where it meets the fuselage and roughly sanded it until it matched the curve of the lower fuselage. This will be removable to ease transportation, like wise with the mast.


I will add lite ply faces to the rear end of the tail boom to stiffen things up and give a good seat for the tailplane to be mounted on.


Slots in nicely


Roughly sanded to shape on the underside


Not a bad fit but still needs fettling


3mm balsa top decking was added aswell


Shorter tail boom than the smaller version to give a bit more rigidity, but it is certainly has Atom genes!



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Looking great as ever Rich....

I am sure you have it covered but lloks like your servo brass ferrules are the wrong way round ??. Flanges should be against the model??

Took my Atom to Weston and late in the evening was going great until the motor threw a wobble.. cruising at 1/3 throttle i dont remember the shout.. "smoke on !!...." Quick land identified 3 of the coils black and a grating when rotated... New motor purchased and installed already. Interest from the other campers on site for the Whippit and this was non stop...


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Nice to hear you got some air time at Weston thumbs up, to be honest I have never thought about the brass ferrules and which way they go round as I have just inserted them from the top and clamped them down. Thinking about it now makes perfect sense to fit them from the underside, I will be doing this from now onsmile


Plans are drawn up but I will have to alter them slightly as I am changing things as I go along embarrassed


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