Last of Kevin's OSCARIIs

[southern or]

Re: Last of Kevin's OSCARIIs

Red markers are the outside markers for the WTD. This is just a "will all this crap fit?" test. The fore servo needs an extension.


All the guts in somewhat of their proper locations.


Still trimming the hull to fit, but it's all coming along.

[southern or]

Re: Last of Kevin's OSCARIIs

Word of advice, if you get the idea to bash a Engel Typhoon WTD, don't. I'm committed to it, but cutting it to fit sucks. Other then that everything is going well and that scares me. I'd normally have some sort of disaster by now.

[JWLaRue]

<<Originally posted by "southern or">>

I ordered some more control components. How good are the clevises for push/pull rod control? I don't have the tools to bend the rods.

So just now I had a brilliant idea and after my parts arrive I'll get cracking. Thanks for all the help!

[southern or]

Alright, I got a bunch of new parts so I don't need to bend the rods and I got longer shafts too. I'm pretty excited about the shafts because they have sealed bearing ends so I don't need a gasket bullet on the WTD. Pics coming. I can now finally start mating things together! Her Buttocks might look a little weird however.

[southern or]

So I've hit a road block and I need some help. By my calculations I need 13.3 pounds of ballast to compensate for the WTC and the removal of the 9.4lb lead battery that is part of the design for the WTC. The Typhoon the WTC is used on also calls for 3-4 pounds of weight. Am I on the right track here?

[JWLaRue]

It's going to require more information in order to try to answer your question.

For example, how did you arrive at those numbers? What is the volume of your dive module?

-Jeff

[southern or]

That's usually the $64K question when building any r/c sub. My preference is to make the WTD only as large as it needs to be to minimize the overall weight required to overcome the buoyancy of the WTD. When using pistons, you'll want a total WTD volume that is somewhere around 2-3 times the total piston volume. This to minimize the overpressure that the shaft and servo rod seals need to contain. You'll get all sorts of answers to this one as there are lots of variables. I believe that you will have loads of space in the wet portion of the hull for weight....and the weight can go anywhere.


That sounds like a good place for them.


I think the Russians follow the same configuration as the U.S....port prop spends clockwise (top spins towards the hull) and the starboard spins counter-clockwise (again towards the hull).


Ideally, you'd like the top of the pistons at the surfaced waterline. This helps to maximize the roll stability.

There are several methods of trimming a boat (of course!), but my preference is to establish a submerged trim, then work out the surfaced trim. You will almost certainly find that you will have needed a number of foam pieces to get it trimmed. When you go for the surface trim, those foam blocks (or parts of them) can be moved to be either above or below the waterline as needed to get a surface trim. Moving the foam above the waterline means that the foam only provides floatation when submerged, while foam below the waterline always provides lift.

Throughout the process you will also find yourself moving both weight and foam forward and backwards to get the pitch correct, left and right to get the roll correct.

-hope this is helping!

Jeff

I did think about a cylinder, but decided against it mainly because for me at least, they're hard to work on after they're built. The tanks are smaller, at 500ml each rather then the Typhoon's 825ml each. The OSCAR is slightly over a foot shorter then the Typhoon, but the deck will be loosing close to 30%-35% of it's volume off the top just to fit. I might lower the deck too, but I haven't decided yet. The thing I like about the decks is that I can line up the motors with the props, rather then having a u-joint spin at a weird angle. I'm not a huge fan of that after I had a u-joint fail when the pin snapped, but I'm also prone to bad luck and failures happening where and when they shouldn't.

I came up with that figure after going over the Typhoon's plans and adding up all of the ballast on it, plus the weight of the battery I'm not using. I'm thinking 13-14 pounds is a lot, but Engel calls for that much in the Typhoon. This boat is about a foot shorter, and 2.25 inches narrower. So yes, I will be trimming the WTC a bit, but I'm also using 2/3 of the ballast tank volume of the Typhoon. I haven't started final assembly yet because I want all my ducks in a row before I hit a point of no return with a screw up. The WTC design calls for ballast under the tech deck so I need some idea of what to add.

Thanks for responding, I hope this sort of helps you guys help me. I'm SO close and I've set myself this goal of beginning trials by mid June. It sounds crazy, I know. This is part of my recovery from a series of unfortunate events and I'm trying to get back being on top of everything. Building things used to be my thing until I had some problems and wound up with nerve damage and this is me trying to get back on the horse. Also helps that I found real doctors who are Asperger specialists.

[southern or]

Okay, this is the bottom portion of the hull. Pictured next to it is a mess and the WTC (that I reassembled). Inside the hull is all of the guts-yes it's a mess and no, almost nothing is where it is going be when the boat gets assembled. I have extension cables for my servos, but the female ends on them are missing the polarity correct fit lip, so I haven't clipped and filed the servo male plugs to fit them yet. The new props are longer so I could move the WTC forward. Plus they have water tight bearings so I'm really excited about that.

I'm thinking I worrying about the weight thing for nothing because as you can see, there isn't much room anyways.

[southern or]

I'm also open to ideas on what to do with that mass of wires when the time comes. It looks like a fire waiting to happen, but it does all work!

[Wheelerdealer]

I have now had a read through your thread and I can see what you are trying to do. Instead of tapering the Engel middle deck like that I wonder if you could reduce the length of the middle deck by making a vertical cut and then repositioning the bulkhead, and move it forward to the point where it will fit (before the hull tapers). You would have a shorter WTBox, moved forward in the hull, but as you have smaller tanks, this should not be much of a problem.

The ballast you need to add is primarily to sink the top of the water tight box to the designed water line. If the top of your box (inc the lid) is at or just below the waterline, then I reckon 600ml of piston tank volume is enough to dive this thin hulled boat. The lead ballast does not all have to go in the WTB, you can add some outside at either end. I would go with what Engel recommends goes inside the WTB with the Typhoon and reduce by the percentage you have reduced the volume of the box by. There will be more to add later as per the Engel instructions for the Typhoon. Better to add too little than too much if you are going to bond it in permanently.

Do use a PVC sheet as a flat base to mount the piston tank and component, the ballast in the WTB can go underneath this sheet. I would keep the power lines and servo lines down separate sides of the boat.
Here is one I did earlier with a lot more wires than you are using. Labelling them up helps too.

[southern or]

Thank you SO much! I got creative with where things go, and the WTC could stand to loose 5-6 inches. I'll need to have the pistons out to make sure it'll all work, but that shouldn't be to hard. All I'll really need to do is cut off the end and mate it at the spot where that metal bar is by the opening.

[JWLaRue]

You will need (want) to know the volume of your dry space. That will determine, in large part, how much weight you will need. As Wheelerdealer noted, as a rough, rule-of-thumb you'll want to be able to get the top of the dry space at the waterline when surfaced.

-Jeff

[JWLaRue]

re: wiring

I use various kinds of wiring sleeves that tidy things up. Check out Mouser or Digi-key......

-Jeff

[southern or]

A rough estimate given that the WTC is not a perfect cylinder or square, about 6 liters empty after it's shortened.

[southern or]

After assessing how much volume is lost from the gear, batteries, motors, ect. I came up with 4.25 liters of positive bouncy only needing 4.27 lbs. to obtain neutral. I used plastic bottles and the tub to test it. I'm going to start with 1 kilo of shot on the bottom of the WTC and trim from there. I know it'll need the other 2 pounds and change, but with the WTC being centered I know I'm going to have trim issues. This is because the props, the extremely long prop shafts, drive motors, ESCs, and 2 of the 3 batteries are going to aft of center.