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The Atom Bomber

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Richard Harris03/06/2015 22:47:35
2051 forum posts
1890 photos

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

Mark Stringer03/06/2015 23:15:32
322 forum posts
209 photos

Nice one Rich .. looks very neat .. I cut the Spratom out this evening (will have to come up with a better name!) I may start a thread on that if I get time .. not sure what blade size I will need. .. what will the bomber use?

Richard Harris04/06/2015 19:39:32
2051 forum posts
1890 photos

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



Richard Elliot04/06/2015 19:57:52
180 forum posts
118 photos

Interested to see how you do the working bomb doors Rich, presumably you will load the ammo er I mean toffies from the hole in the top of the bomb bay.

An Led light set would make it a good night bomber!devil

Stephen Jones04/06/2015 21:29:25
2659 forum posts
1503 photos

Very nice pictures of you're build Richard .

I shall be watching this one with interest .


Ozgur Sar10/06/2015 10:05:52
28 forum posts

Looks like an exciting new model

Richard Harris10/06/2015 22:35:26
2051 forum posts
1890 photos


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.



Richard Harris14/06/2015 18:40:54
2051 forum posts
1890 photos

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

Richard Harris15/06/2015 19:13:49
2051 forum posts
1890 photos

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



Martian16/06/2015 10:05:10
2215 forum posts
1085 photos

it's certainly going to be big Rich ,will it be ready for Greenacres ?

Tim Mackey16/06/2015 10:19:48
20919 forum posts
304 photos
15 articles
Oooh nice job Rich
Richard Harris17/06/2015 07:44:04
2051 forum posts
1890 photos

Thanks for the reply gents, I thought I was talking to myself ! (though that is not unusual disgust). I will do my best to get it completed for Greenacres but it is only 3 weeks away!


Danny Fenton17/06/2015 11:20:12
9095 forum posts
3943 photos

Looking good Rich, looking forward to catching up at Greenacres

PS love the pics, really nice



Chris Barlow17/06/2015 18:22:36
1808 forum posts
1228 photos

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

Richard Harris18/06/2015 13:07:12
2051 forum posts
1890 photos


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

R Gar21/06/2015 12:51:47
1 forum posts

Looks good Rich,

What size rotor blades are you planning?

just 1.5 times the original like 66 x 675 mm.

Also what size outrunner?



Tim Hooper21/06/2015 21:12:38
2857 forum posts
2363 photos

You might well be a whirly-headed reprobate, but you're also a damn tidy builder!


Richard Harris22/06/2015 06:43:31
2051 forum posts
1890 photos


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.


Richard Harris22/06/2015 19:12:47
2051 forum posts
1890 photos

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!



Stephen Jones22/06/2015 19:43:47
2659 forum posts
1503 photos

Looking forward to seeing this one Richard ,

I can not believe how good you're pictures are , are you sure someone is not taking them for you wink


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