[PSUBS-MAILIST] Fw: Thruster position

[Alec Smyth via Personal_Submersibles]

Hi Hank,

I had to think about the same thing not long ago given the new sub has two
vertical thrusters. The fundamental question was whether to point them up
or down. What I settled on was pointing both downward. Here was my
reasoning:

- I like diving the sub slightly positive, and use the side thrusters for
depth control. Pointing downward, they are operating in their most
efficient direction for the vast majority of the time.
- Pointing downward the wash goes UP, which prevents stirring up silt.
- By canting them outward you can crab by running them in opposite
directions, gaining an extra degree of motion.

Just two cents. If you prefer diving the sub negative you could point them
both up. That would give you more power for reaching the surface in an
emergency, but it would stir up silt the rest of the time. I have really
huge MBTs for the emergency situations, so went for what I thought was the
most convenient thruster direction in normal use.

There's one more detail that I'll just have to test. When I dive Snoopy
down on the side thrusters, she can get into really fast rotation because
both props are turning in the same direction. I counter that by tilting one
of the side thrusters slightly off vertical, but with the permanently
mounted thrusters I won't have that possibility. It may not be an issue on
the new sub, but if it is, I'm thinking I might have to install a little
vane in the wash of the vertical thrusters to compensate. Or I could
correct the rotation with the horizontal thrusters. Maybe even program that
compensation into the speed controller logic. Practice will tell.


Best,

Alec



On Thu, Dec 3, 2015 at 8:39 AM, hank pronk via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> Tim,
> My idea was to mount one vertical thruster pointing up and one pointing
> down because the props are only efficient in one direction.  This way I get
> full power from one and half power from the second in both directions.
> Tilting them may get weird, but I can easily change things over time.
> Hank
>
>
>
> On Wednesday, December 2, 2015 8:22 PM, T Novak via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
>
> Hank,
>
> Why not cant your vertical thrusters 45 degrees out from the vertical?
> Sort of like this bow on view:  /O\   where the / and the \ represent the
> thrusters canted 45 degrees out from the O which represents the pressure
> hull.  This would allow the down wash to miss the horizontal thrusters
> while both "vertical" thrusters are heaving the sub upwards.  And it would
> provide controlled translate (sidle) movement when the two "vertical"
> thrusters are powered  to thrust one up and one down.  Your ballast block
> will keep the sub from rolling and force it to translate sideways.  This
> works very well for the DW2000's.
> Tim
>
> *From:* Personal_Submersibles [mailto:
> personal_submersibles-bounces at psubs.org] *On Behalf Of *hank pronk via
> Personal_Submersibles
> *Sent:* December-02-15 11:11 AM
> *To:* Personal Submersibles General Discussion <
> personal_submersibles at psubs.org>
> *Subject:* Re: [PSUBS-MAILIST] Fw:
>
> Alec,
> I was hoping the wash would go around the motor, I have no experience with
> this, but it makes sense. :-(  I will move it back.  My original plan was
> to have them up front vectored 45 degrees, but they are very heavy, over 40
> lbs each and that takes away from the buoyancy for the arm.
> Hank
>
>
> On Wednesday, December 2, 2015 12:04 PM, Alec Smyth via
> Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>
> If it were me, I'd move it just a little bit aft, just enough to leave the
> vertical one unrestricted. I don't think you'll have any trouble at all
> rotating the boat if the thrusters are not exactly in the middle.
>
> Best,
>
> Alec
>
> On Wed, Dec 2, 2015 at 1:57 PM, hank pronk via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
> Hi All,
> This is a picture of my proposed thruster location, I am not sure if the
> motor in this location will interfere with the prop wash from the vertical
> thruster inside the can above the thruster.
> What do you guys think?  I want the motor as mid ship as possible for best
> steering.  This location is also good for cabling to the pen plate
> Hank
> On Wednesday, December 2, 2015 11:51 AM, xxx xxxxx <mp13 at live.ca> wrote:
>
>
>
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