Last of Kevin's OSCARIIs

[southern or]

Re: Last of Kevin's OSCARIIs

Interesting thing about the prefab motor housing, it isn't wide enough so I'll need to cut it apart to have the props line up.

It isn't necessary to have the prop shaft(s) line up with the shaft on the motor housing. Instead of trying to obtain perfect alignment, use either DuBro dog bones or miniature universals. Completely eliminates the problem and you won't ever have to worry about binding.

-Jeff

I'm already going to use a universal joint, but after a dry fit I found out that the motor housing doesn't fit and is actually too wide, so I'm going to need to cut out the center of it anyways. The nice thing about the motor mount/housings is that they have a reduction gear built in rather then being direct drive. Any ideas on how to make sure the prop shafts are aligned correctly? I would rather not have the blades hitting or have the props facing different directions. Thanks!

[JWLaRue]

Re: Last of Kevin's OSCARIIs

Any ideas on how to make sure the prop shafts are aligned correctly? I would rather not have the blades hitting or have the props facing different directions. Thanks!

...not sure I correctly follow your question. (I'm not very familiar with Oscars, so please bear with me)

Is the concern around the props being too close together such that the blades hit? Looking at the photos you posted, there doesn't appear to be any choice as to where the props fit at the ends of those pylons. I'm not at all clear what "props facing different directions" might mean?

Regarding aligning the prop shafts - in general what I do for one or two shaft boats is to make a jig that holds the forward end of the shaft in place. Then I figure out and construct the necessary support(s) and bushings to hold the shaft in that desired location. The jig stays in place until after everything is epoxied into place.

Another suggestion, this for your internals. If practical, try to keep the Engel pistons at or near the centerline of the hull. This will make trimming the boat much easier.

-Jeff

[southern or]

Re: Last of Kevin's OSCARIIs

Any ideas on how to make sure the prop shafts are aligned correctly? I would rather not have the blades hitting or have the props facing different directions. Thanks!

...not sure I correctly follow your question. (I'm not very familiar with Oscars, so please bear with me)

Is the concern around the props being too close together such that the blades hit? Looking at the photos you posted, there doesn't appear to be any choice as to where the props fit at the ends of those pylons. I'm not at all clear what "props facing different directions" might mean?

Regarding aligning the prop shafts - in general what I do for one or two shaft boats is to make a jig that holds the forward end of the shaft in place. Then I figure out and construct the necessary support(s) and bushings to hold the shaft in that desired location. The jig stays in place until after everything is epoxied into place.

Another suggestion, this for your internals. If practical, try to keep the Engel pistons at or near the centerline of the hull. This will make trimming the boat much easier.

-Jeff

Oh, I was referring to having one prop misaligned, like having a pitch off center, but you covered that . Thanks for the heads up on the pistons! I'm not sure why, but Engels has them off center to the right and left on the Typhoon plans. I still need to cut the Water Tight Deck to fit, and open the top part of the hull (conning tower, water intakes, dive plane slots, ect.) as well as add all the control surfaces to the aft before I'm ready to start epoxying the hull. I think I've setup the aft to the point that once it's together, it can't be undone. But then again the WTD setup is pretty much a one time permanent setup too.

Something that I've been worrying about is how much solid ballast to add to the inside of the WTD before I install the works in it. Engel has something like a couple of pounds and a lead acid battery for weight. The OSCAR will be powered by 3 NiCad batteries and the WTD will be cut to fit, so it'll loose some volume. I'm still unsure if I got the right size tanks, but the TAE2 setup is everything I want out of a static dive system. I'm actually looking forward to trimming so thanks for that tip again! If I get tired of trimming, it will have a plane control system so I can activate that.

Engel's instructions say to put the pressure sensor intake holes in an area that isn't subject to the pressure added by propulsion. Would a intake hole within the wet hull on the aft of the WTD work? I need two because it'll have two sensors.

As for the brass props, yeah, those are a little bit bigger then the props it came with and if the alignment isn't perfect, they will hit each other. Also, is it counter-clockwise clockwise, or clockwise counter-clockwise for the props?

Almost forgot, but this is a long ways of yet, how do you ballast the sub for the surface and submergence so the boat remains on an even keel in both modes? I get that the ballast tanks need to be near the keel, but I've only done dynamic boats to this point. I'd rather not have it roll when it dives.

[tsenecal]

Re: Last of Kevin's OSCARIIs

Thanks for the heads up on the pistons! I'm not sure why, but Engels has them off center to the right and left on the Typhoon plans.

they are off center in the typhoon to make room for the piston rods when the ballast tank is full. can't forget about the rods.

[southern or]

Re: Last of Kevin's OSCARIIs

Thanks for the heads up on the pistons! I'm not sure why, but Engels has them off center to the right and left on the Typhoon plans.

they are off center in the typhoon to make room for the piston rods when the ballast tank is full. can't forget about the rods.

Oh, that's right!

[JWLaRue]

Re: Last of Kevin's OSCARIIs

Something that I've been worrying about is how much solid ballast to add to the inside of the WTD before I install the works in it. Engel has something like a couple of pounds and a lead acid battery for weight. The OSCAR will be powered by 3 NiCad batteries and the WTD will be cut to fit, so it'll loose some volume. I'm still unsure if I got the right size tanks, but the TAE2 setup is everything I want out of a static dive system. I'm actually looking forward to trimming so thanks for that tip again! If I get tired of trimming, it will have a plane control system so I can activate that.

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.

Engel's instructions say to put the pressure sensor intake holes in an area that isn't subject to the pressure added by propulsion. Would a intake hole within the wet hull on the aft of the WTD work? I need two because it'll have two sensors.

That sounds like a good place for them.

As for the brass props, yeah, those are a little bit bigger then the props it came with and if the alignment isn't perfect, they will hit each other. Also, is it counter-clockwise clockwise, or clockwise counter-clockwise for the props?

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).

Almost forgot, but this is a long ways of yet, how do you ballast the sub for the surface and submergence so the boat remains on an even keel in both modes? I get that the ballast tanks need to be near the keel, but I've only done dynamic boats to this point. I'd rather not have it roll when it dives.

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

[JWLaRue]

Re: Last of Kevin's OSCARIIs

Thanks for the heads up on the pistons! I'm not sure why, but Engels has them off center to the right and left on the Typhoon plans.

they are off center in the typhoon to make room for the piston rods when the ballast tank is full. can't forget about the rods.

Good point! Depending on the length of the WTD and the size of the pistons, the offset/angle may not need to be very large.

-Jeff

[southern or]

Re: Last of Kevin's OSCARIIs

The offset will have the tanks no less then the full width of a tank between them. By the typhoon design, the batteries and most of the electronics are in the middle sitting on top of a fair amount of solid ballast.

[JWLaRue]

Re: Last of Kevin's OSCARIIs

Yup, the Engel Typhoon has a huge WTD and as a result requires a lot of weight to get it to trim out.

-Jeff

[southern or]

Re: Last of Kevin's OSCARIIs

Yup, the Engel Typhoon has a huge WTD and as a result requires a lot of weight to get it to trim out.

-Jeff

Yep, I got a spare one from Engel's for the Oscar because the OSCAR is long enough and tall enough for it. Only problem is that the aft tapers down so I'll be cutting it to fit.

[wlambing]

Re: Last of Kevin's OSCARIIs

Gents,
On twin screw ships it is way more efficient for the screws to turn outward at the top, port screw counter-clockwise and starboard screw clockwise (when looking at them from aft). Turning inward, the "prop wash" is deflected by the hull and flow is significantly diminished. All USN twin-screw, or multi-screw ships use this convention.

Have a lovely modeling day!

B^)

[bwi]

Re: Last of Kevin's OSCARIIs

Gents,
On twin screw ships it is way more efficient for the screws to turn outward at the top, port screw counter-clockwise and starboard screw clockwise (when looking at them from aft). Turning inward, the "prop wash" is deflected by the hull and flow is significantly diminished. All USN twin-screw, or multi-screw ships use this convention.

Have a lovely modeling day!

B^)

You are right…..but allow me to add following:
there is a tendency in commercial vessel (offshore) that the propellers are identical.....it is a budget aspect......you will need only one spare propeller instead of two (with clock and counter clock). If the vessels is equipped with Azimuth drives you need only one complete spare unit instead of two. The only disadvantage with two identical props is the course keeping it’s a little bit harder....but hey that what’s autopilots are designed for. Speed and staying undetected is not an issue with these vessels but budgets are.

Grtz,
Bart

[ober freak]

Re: Last of Kevin's OSCARIIs

Gents,
On twin screw ships it is way more efficient for the screws to turn outward at the top, port screw counter-clockwise and starboard screw clockwise (when looking at them from aft). Turning inward, the "prop wash" is deflected by the hull and flow is significantly diminished. All USN twin-screw, or multi-screw ships use this convention.

Have a lovely modeling day!

B^)

Which hull on a sub? (since those streamlined designs)

Ok, the Oscars also use this standard orientation.


K-132 Irkutsk


K-141 Kursk


K-186 Omsk


K-442 Cheljabinsk


K-456 Tver'

[wlambing]

Re: Last of Kevin's OSCARIIs

I was thinking diesels, where the screws are forward. I'm a child of the 50's. When I got to New London, there were more diesel boats there than there were nukes! Anyway, as you can see in the pictures, the screws turn outboard on each side.

B^)

[JWLaRue]

Re: Last of Kevin's OSCARIIs

Drat! Got it backwards!

Thanks, Bill.

-Jeff