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Oberon submarine

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ashley needham13/07/2009 18:42:44
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6385 forum posts
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I am taking the plunge (!) and diving in (!) to build a sub. I have always wanted a sub since an early attempt in my, ahem, early years. My inspiration is the free plan by Hal Harrison  in MMI. What an admirable fellow to cut thro the mystique of submarine construction with my sort of plan.( Easy). I shall of course be modifying it a bit to make it resemble an Oberon (the last sort) class boat. This mainly means working on the proportion, and also making the top out of thicker stuff in order to give a bit of curve to the , er, top. A rib running along the top will sort the rest out. I had contemplated twin screws, but i seem to have too many boats of this configuration, all with a central rudder, and want a bit of manoeverability so will stick with one screw. I am using only two channels, which i am sure will be ok for dynamic diving in a straight line. The diving planes will be in a fixed position, to be determined by trail and error, and trail and error and and.. 
 
Its going to be a tad longer than the plan, at 36" and am at the moment wondering if a 385 motor on 7.2V will provide sufficient shove? Subs not requiring as much power as surface craft, or at least I dont know about models...
Watch this space!   Ashley
ashley needham19/07/2009 10:06:57
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6385 forum posts
266 photos


So. In the flesh.The top is held down with a set screw either side of the sail. The rudder post is very short, so unlike Hal`s version whereby he used an external brace, I have put an additional bush in the removable top, thus supporting the rudder top and bottom. Hal couldnt use this method as his top was very thin. The motor mount currently has a 540/1 MFA in it, but has an insert available to hold a 385, no mods neccessary. This will give me loads of options for power I may just be able to fit a 45mm prop and then a 555 motor for that authentic slow running submarine prop set-up.?There are very few vent holes in the top, because the projected waterline will be just above the top/bottom split, and so there will be no air to vent. I have yet to decide on the diving plane layout and position, and they have to be able to be adjusted and then fixed into position,but I have an idea for that. Both front and rear planes will be adjustable. I have room for a gel 4.5Ahr 6v battery, so will use that to start with and I  will need the weight in any case.  Hal used remarkably little in the way of ballast, but mine has a lot more balsa in it and is of course that much bigger. It is also proportionally fatter than Hal`s, being modelled on something specific, rather than just being generic.    Paint today I think!   Its going to be Black, when finished,matt if I can get a decent finish, or satin . On the other hand I may like the look of it in its very dark Grey primer. never can tell.  Ashhley
Bob Abell19/07/2009 11:02:06
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8733 forum posts
2722 photos
A nice little model, Ashley
 
I like the engineering solution for the rudder too
 
Could you give it a few coats of paint.... then carefully score certain parts of the hull, to indicate plating, but not all over, and a final coat................it would be quite nice?
 
Bob
ashley needham19/07/2009 16:11:00
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6385 forum posts
266 photos
Bob, good idea. There is not much in the way of plating on these things, but there is some detail on the rib, and the front torpedo tube covers are visible. On the other hand 90% of it is underwater when on , or should I say, IN the pond!     Perhaps I should get a jolly roger flag.   Ashley
ashley needham23/07/2009 07:04:52
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6385 forum posts
266 photos

better in Black.Test float in bath...up to the diving plane holes with just the battery, motor and rudder servo in place, so loads of bouyancy to play with.
David Meier23/07/2009 07:41:22
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205 forum posts
81 photos
It is looking very smart Ashley. Don't forget the odd rust streak.   How are you going to show us it in action? It will be under water. We will just have to take your word for it. You could take up scuba diving.
David.
Bob Abell23/07/2009 07:44:15
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8733 forum posts
2722 photos
Ashley..................Very pretty model........10 out of 10!
 
But how long is it?...................etc....etc
 
Bob
 
PS.......Don`t need any crew either!
ashley needham23/07/2009 18:17:01
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6385 forum posts
266 photos
Bob. It is 36 inches long  and 4 inches wide, the sail is 2 1/2 inches high, the curved top is made out of 1/2 balsa, as is the rib. The rib is 1.2 inches wide. Sides 3mm lite-ply. I have a 40mm prop on it at the mo, and a 540/1 MFA motor. It will have a 6v 4.5Ahr  battery. Dive planes and rudder are thin brass sheet soldered to 4mm brass posts. Control to the rudder is via an aircraft style sheathed wire. weight.. I will get back to you on that once ballasted.Ashley
ashley needham28/07/2009 19:01:25
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6385 forum posts
266 photos
I  have been mulling over sealing the hatch up. Hal no doubt took more care over getting his hardwood strips flat and flush etc than me,,,mine has a very very slight camber either end. I dont want to fiddle too much so have hit on the idea of a gasket. I like the grease seal idea, and so i have made a gasket out of felt, which I have smothered in grease. The felt will need hardly any pressure to seal against the teeny dips, and substantially the seal will still be by grease. I have put an earthing wire on the metal motor mount to ground the motor to the water, a small suggestion from someone regarding suppression. Everything is crammed in together and as the thing is grease sealed its a bit messy and time consuming to make alterations once covered. Ashley
 

ashley needham31/07/2009 23:24:03
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6385 forum posts
266 photos
Bath test tonight, and the sealed watertight box leaked, as of course they are designed to.It seems it was from the propshaft though, the greasy bit was sealing up the lid ok. i had anticipated a drop or two, but this was more like two hundred. So saying, it wasnt desperate, and for the 20 mins or so it was underwater there was only a couple of teaspoons in there..never the less. i may put SOME grease In the shaft, but will first try the greasy felt washer between thin nylon washers trick first. A set of wad punches is a wonderful thing.
The top is far more buoyant that you can imagine, and a fair bit of lead was added to achieve the correct trim. I have my doubts about its diving capability now..time will tell, and i may fit the larger dive planes from the front on to the rear, and make some extra big ones for the front. I tried the motor out in the bath, (MFA 540/1 and 40mm 3x blade brass prop) and was pleasantly suprised by the push, and on a current draw of approx 3- 3.5 Amps. Again I think a 35mm prop may yield a better performance as being more of a size for the motor.
it weighs in at about 7 pounds, or 3.15Kilos, (drained weight) .It is considerably heavier full of water, and as Hal says, looks a bit odd settling down when you put it in first thing.
No pictures, the bath is fairly boring.   Ashley
oh, one more thing, the 12 vent holes are totally unnecessary and will be filled in.
And I need a Jolly Roger flag for the ariel..

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