Kort nozzles,
There is a company called Propguard which have an improved version of
the Kort nozzle for small boats. I read somewhere that a Kort nozzle
has a pressure build up problem somewhere and the ring is best split
into two, fore and aft, with a gap between which is what the propguard
does.
http://www.getaprop.com/content-categories/cat-896/prop_guard_hydrofoil.html
there is an 11 inch version which could be modified. I am wanting to
get a small cheap one so I can get to see the engineering behind it.
Kort nozzles are no good above 10 knots which is fine for subs. There
is also an improved version called a Rice Speed nozzle which has a
modified profile with reflex built in.
If anyone has seen or knows of the paper referring to the pressure spike
I would love to get hold of it. I found it once and now cannot find it
again. Hugh
*From:* owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] *On Behalf Of *Brian Cox
*Sent:* Wednesday, 10 February 2010 8:27 a.m.
*To:* personal_submersibles@psubs.org
*Subject:* RE: [PSUBS-MAILIST] Kort nozzle
Frank, It seems like it would be pretty easy to fabricate a prop out of
a piece of flat plate steel. Cut out your shape with a plasma cutter
and them turn each prop the desired angle. A multiple blade prop with
say 8 - 10 blades would give you a lot of torque if your RPM was low
enough and the motor was the right power.
On another note I'm starting to lean twords a connecting pontoon
arrangement with an outboard engine for powering to dive locations.
This would solve an imediate problem for me until I develope a true
diesel electric that could submerge. In the meantime I could get my sub
running with just batteries and attack that problem at a later date.
Brian
-----Original Message-----
*From:* owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org]*On Behalf Of
*ShellyDalg@aol.com
*Sent:* Tuesday, February 09, 2010 11:08 AM
*To:* personal_submersibles@psubs.org
*Subject:* Re: [PSUBS-MAILIST] Kort nozzle
Minnkota has a couple of new products out. There is a newer motor
rated at 2-1/2 HP coupled with trim tabs and electric actuators. The
site I read said the dual motor set-up would run a standard pontoon
boat at 5 knots.
I too will be using the regular Weed Wedge 2 props for now but would
like to use three or four bladed props as an upgrade later on the
two rear thrusters. They have 3/16" thick stainless prop rings on
them now, acting as kelp guards and rudders. I think I could
fiberglass a Kort nozzle shape onto the SS rings so adding multi
blade props could add more "push". My side thrusters will need to
keep the "Weed Choppers" as they have no guard rings.
I was thinking it might be possible to fabricate some props from
FRP. Balance would be an issue and longevity too as the FRP is soft
making it wear quickly. For sure you couldn't run into anything with
them.
Could it be possible to buy aluminum props without the hole and
machine the correct size hole for a Minnkota shaft ?
Another thought is to fabricate a new replacement end section that
fits a Minnkota with a magnetic coupling so no pressure compensation
would be needed. Bolt it on in place of the factory end section.
The overall diameter would need to be larger than the Minnkota
housing to accommodate the mag coupling but if the shaft was
extended a few inches a taper could be used to clear the area
directly in front of the prop.
I mentioned this to my machinist son-in-law and he said he would be
glad to make something if I could draw it up. ( maybe later )
I know Minnkota spent a lot of expertise designing their props for
the motor but I wonder if having it designed for chopping weeds has
reduced it's thrust output.
True, I don't know shit about props, but there may be room for
improvement here.
I finished the drop weight/carriage yesterday, except for some tabs
to attach the lead bricks and a little finish polishing. It's
freakin' heavy already. It has 6 steel rollers rated at 1500 LBS.
each and two smaller rollers so the sub will "teeter" on the main
rollers. Should make it easier to move the sub around on the shop
floor and will be used when loading/unloading on the trailer. Once
installed, the sub will be MOBILE !
One step closer to Florida !!!
Frank D.
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