Oberon submarine

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Oberon submarine

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13 July 2009 at 18:42 #21978
ashley needham
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@ashleyneedham69188
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
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13 July 2009 at 18:42 #6578
ashley needham
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@ashleyneedham69188
19 July 2009 at 10:06 #22104
ashley needham
Participant
@ashleyneedham69188
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
19 July 2009 at 11:02 #22108
Bob Abell 2
Participant
@bobabell2
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
19 July 2009 at 16:11 #22111
ashley needham
Participant
@ashleyneedham69188
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
23 July 2009 at 07:04 #22174
ashley needham
Participant
@ashleyneedham69188
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.
23 July 2009 at 07:41 #22175
David Meier
Participant
@davidmeier28154
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.
23 July 2009 at 07:44 #22176
Bob Abell 2
Participant
@bobabell2
Ashley………………Very pretty model……..10 out of 10!

But how long is it?……………….etc….etc

Bob

PS…….Don`t need any crew either!
23 July 2009 at 18:17 #22181
ashley needham
Participant
@ashleyneedham69188
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
28 July 2009 at 19:01 #22286
ashley needham
Participant
@ashleyneedham69188
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
31 July 2009 at 23:24 #22327
ashley needham
Participant
@ashleyneedham69188
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..
2 August 2009 at 15:41 #22366
ashley needham
Participant
@ashleyneedham69188
Well Well, the test today. on, or IN the pond. It looks fantastic on the surface, and the performance appeared to be adequate, however it would not dip under the water even at full throttle, SO

I balanced a few weights on the rib (spanner, box spanner, srewdriver and a few bits of lead) until just the rib was surfaced, and popped the lot below decks. After much tweaking, extra weights, redistributing weights and changing the propellor…..It dives, or at least, bits of it do, but not all at once.

The front OR rear goes below, or the front dives and the back resurfaces…….the best i acheived was running roughly horizontally about an inch over the rib, so fin still 2 inches out.

There are two things here. There is not enough power, and the radio reception is not great. I need to make some larger front diving planes, and switch the existing front planes to the rear, this will give me more diving power and so a better dive at less than full speed. I must admit there is just a small if not strong possibility it wont sustain a steady depth but it doesnt matter, as long as it goes under a bit that will do. I have changed the motor to a speed 400 for more go, as when the front was down and the back was coming up it definitely seemed as if a bit more shove would be handy to force the back down again.I had a chat with a man passing who was into model subs and he had some interesting comments to pass. Ashley
2 August 2009 at 16:12 #22368
60watt
Participant
@60watt
Posted by ashley needham on 02/08/2009 15:41:06:

I had a chat with a man passing who was into model subs and he had some interesting comments to pass. Ashley

What is it that he said that wasn’t worth passing on?
2 August 2009 at 22:01 #22370
ashley needham
Participant
@ashleyneedham69188
well….we or at least he, talked about the change of trim that occurs when the boat starts to dive and then actually submerges, we chatted about various methods of sealing the hatch (although the boat was in the water for 1 1/2 hours today and was bone dry inside the sealed bit). he talked about the behaviour of his Ohio, although that has a different shape entirely, we chatted about the diving vanes and operation therof; i was reminded of a method of controlling the foreplane via a v shaped flag on a wire..the plane is held at a downwards angle, and when the boat dives, eventually the flag gets submerged, levering the plane into a horizontal position for running, the plane being kept down in the normal position by a light spring. THEN (after he admired the general shape of the beast) we chatted about ballasting in general and where the weight might be put and possibly what effect it would have in the different positions. THEN (after it was appearing that i MAY HAVE to get a 3 channel set.)…I discussed the plan of action with all and sundry whilst fending off various small boys showing an interest. Talking of ballast, as you do, an interesting device was mentioned WHEREBY a pin would be inserted in the boat, or possibly several, and one would have various weights with hokes in so that adjustments could be made by placing said weights on the pins. An easy method of swapping ballast and one which keeps the ballast in the right place. A spot of glue, and hey presto, the stuff id firmly set in the right place. A mention was also made of the temperature of the water, this affects the density and thus the ballasting /trim requirements, but i said i would make the diving planes a bit bigger and the motor much more powerful and that would take care of it. AND THEN….He being a submarine buff , pointed out various idiosyncrasies of the O class, the fact that the sonar dome varied in size and shape between refits and nationalities, the hatches in the top of the fin, where I should put a Jolis Rouge flag(the Jolly roger is a corruption of the French “Jolly Red” term) , where the torpedoes were and why there is a littly “walkway” under the fin.

Sorry, you did ask !!!

Ashley
2 August 2009 at 22:35 #22372
60watt
Participant
@60watt
Can you control the planes at the moment?
3 August 2009 at 07:23 #22377
ashley needham
Participant
@ashleyneedham69188
No, they are just fixed, at least, they are adjustable via some screws inside for experimental purposes. I have room in the sealed portion for another servo, but dont want to go to the expense of another radio set just for the one model. Ashley
3 August 2009 at 07:32 #22378
60watt
Participant
@60watt
If you can stretch to a servo then you can make the rear planes keep a level trim without another channel.

How about that?
3 August 2009 at 07:38 #22380
ashley needham
Participant
@ashleyneedham69188
That would be very good…..how?
3 August 2009 at 07:49 #22382
60watt
Participant
@60watt
I’m surprised the “man passing who was into model subs” did not tell you how.

They use a pitch controller that senses tilt.
3 August 2009 at 08:07 #22383
ashley needham
Participant
@ashleyneedham69188
He did mention various devices as it happens but they sounded expensive to me. The sophistication may be at odds with my relatively simple build. However its certainly an option. I have made some larger `planes now, and fitted a speed 400, and also made some lead “saddles” to fit over the rib so I can effect fine changes of ballast. I am suprised that no other submariners have put in their penny`worth yet ? have you indulged? Ashley
3 August 2009 at 08:11 #22385
60watt
Participant
@60watt
have you indulged?”

Posted by ashley needham on 03/08/2009 08:07:26:
. I am suprised that no other submariners have put in their penny`worth yet ? have you indulged? Ashley

Me?

or do you mean “where is everybody?”

Edited By 60watt on 03/08/2009 08:15:18
3 August 2009 at 08:25 #22387
ashley needham
Participant
@ashleyneedham69188
“where is everybody” as usual !
3 August 2009 at 08:40 #22389
60watt
Participant
@60watt
I think they’ve been quietly reading your progress report but were scared of giving feedback.

Something to do with “I think I’ll make a sub” and six days later a scratchbuilt sub appeared.
3 August 2009 at 10:52 #22394
Bob Abell 2
Participant
@bobabell2
“Where is everybody?”……….Ashley asks?

I was a bit dubious of asking anything………………Having seen your exhaustive replies!

A few paragraphs wouldn`t go amiss, Ash!……..They give the reader a chance of a breather and can pick the text more quickly?

Just trying to be tactful, Ash!

Bob
3 August 2009 at 13:17 #22396
ashley needham
Participant
@ashleyneedham69188
60. Its wonderful what you can achieve with 2 sunny days off work! but its not a very complicated design.
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