SAS snorkel head valve - modifications

[Slats]

I'm yet to get my SAS SDs so hoping that this doesn't seem presumptuous, but was thinking of ways to modify the SAS snorkel head valve to live within what will be a very tight fit in the Permit class I'm building later this year, and also activate higher up - close to the sail top.



The photo above is the Permit class snorkel resin part in 1/72. The real one was a pesky item for crews mounted ahead of the conning area.
Note the flip/ hatch valve - actuated by the long thin push rod astern of the induction pipe.

Now I could try and get clever and make that flip lid, and mimic exact scale, but if I'm honest I think the this would be a problematic sealing item. I could see it either having a bias to stay open - not good, or stay shut, not good.
So here's what I have mocked together.

I figured use the actuating push rod to act in the same way David current seals off the internal sail mounted float valve, but use a the junction guide support atop the snorkel to hold the pipe to be sealed off.





The push rod can be activated by foam float inside the top of the sail.
I figured using o'rings to enhance the seal, but the smallest one's I could get my hands on are a tad too big.

Then it occurred to me - use pieces of rubber clippard line in place of an o'ring. The air line diameter we use is indeed at its smallest the clippard line.
The photo below shows the clippard line o'ring substitute in place


The photos below shows the completed prototype. The top of the two tubes are of course sealed, and need scale upper features added.
The push rod actuator needs a thin tube support to hold it operating true, which could be mounted lower down in the top of the sail.
The cross piece is of course a little out of scale, but not that far away.




Jump in guys, especially David. What do you think?

Cheers

John

[redboat219]

How about using a telescoping head to seal off the induction opening. You use the operating shaft to raise and lower the snorkel head. A rubber element inside ensures against leaks. The whole snorkel head is operated by a float connected to to the operating shaft by a lever.

Got the idea here btw, http://www.gentoosjournals.co.uk/Lin...-S-Winans.html

[Slats]

How about using a telescoping head to seal off the induction opening. You use the operating shaft to raise and lower the snorkel head. A rubber element inside ensures against leaks. The whole snorkel head is operated by a float connected to to the operating shaft by a lever.[ATTACH=CONFIG]21009[/ATTACH]

Got the idea here btw, http://www.gentoosjournals.co.uk/Lin...-S-Winans.html

Nice idea - I like it - might have some concerns in the Permit class - small sail area, small width too, and sail planes complicating the avalaible space. I like the fact the float is high in the sail. Any others comments please keep them coming?
Thanks

John

[trout]

John,
I think the bigger concern is the float. It will need to be buoyant enough to lift your wire up when you dive and heavy enough to break that seal (vacuum) when you surface. What are your thoughts on that?

[Slats]

John,
I think the bigger concern is the float. It will need to be buoyant enough to lift your wire up when you dive and heavy enough to break that seal (vacuum) when you surface. What are your thoughts on that?

Yep
for my setup was thinking of running float on a hinge inside the top of the sail. Imagine the gas saver float in the ballast tank in days gone by. You'll get a little benefit of the fulcrum, with the push rod sealing the valve working off the extreme end of the float, lifting away from the pivot as the float pops up. The float and the whole mechanism only need move a few mm to open and close the vent. The float here is largely horizontal orientation, in David's set up its largely vertical, and thus engages lower down the sail.

Opening I'm thinking won't be a problem - gravity at play although as you point out there is a tiny bit of internal suction vacuum at work if the LPB is running. I'm hoping the small tube size will help too.

Case of suck it and see. (no pun intended)

J

[He Who Shall Not Be Named]

I like this. The weight of the push-rod works for you -- force needed to pop the seal against the vacuum within the SD. You can get by with a surprisingly small float. Very inovative stuff here, guys. Keep it up! Reducing the inlet area of the nipple reduces the force the differential pressure has across it. Use a 1/16" internal diameter tube for the snorkel head-valve inlet nipple. Big enough to pass enough air to empty the ballast tank without choking too much, and small enough to limit 'holding' power of the differential pressure across the valve elements.

M

[trout]

Wow, this is interesting. I am not sure I get it all, but I will watch and learn. As David said the smaller tube reduces the differential pressure which in a lower intake might open up a bouncing motion, but because your intake is higher up, the float is submerged and giving the full lift to keeping your seal closed (this a good thing). hmmmmm, stuff to ponder on. Also, The sail is thin and small, in David's design, he uses foam ( good buoyancy and great for mass production), would making a one off hollow plastic float give more lift in a small area?

[He Who Shall Not Be Named]

floatation (buoyant force) is directly proportional to the displacement of the float, be it made of goose feathers or U-238 (the common isotope of Uranium).

[trout]

O.K. - so foam or thin walled float will depend in which one displaces less. Eureka!

[Subculture]

A thin walled plastic snorkel float will be very squishy. Foam is really impossible to beat in this application.

[Buellman1]

Just a thought, but what about a water sensor triggering a solenoid valve? The sensor should be small enuff to mount anywhere you want. Someone out there should be able to make a small board to control the solenoid via two probes.

[Slats]

Just a thought, but what about a water sensor triggering a solenoid valve? The sensor should be small enuff to mount anywhere you want. Someone out there should be able to make a small board to control the solenoid via two probes.

Nope
- you still need a valve mechanism and you won't find a solenoid that small that can cope with water and air - the passive dynamics of water rising and falling around the sub are best.
-you need to also consider the external wires to / from the WTC - which in my 20 years or running subs are the biggest PITA I have ever encountered.

J

[Slats]

Use a 1/16" internal diameter tube for the snorkel head-valve inlet nipple. Big enough to pass enough air to empty the ballast tank without choking too much, and small enough to limit 'holding' power of the differential pressure across the valve elements.

M

a K&S Brass 3/32 pipe has a 1/16" internal diameter.

do you think it needs a rubber seat / seal David like I have suggested?


The advantages I see boys and girls with getting this valve amongst the masts is if you spend most of your day sailing at PD (which I do) there is less propensity for the water spilling down the induction pipe should the snorkel head valve for whatever reason pop open, and if you can get the float activation in the sail up higher (say above the dive planes), you get to using the outside air much faster than the SD air space. This means less work on the SD air.

The disadvantages I see is **** head skimmers Foxtrot Uniform Charlie Kilo -ing up you masts!

J

[He Who Shall Not Be Named]

Yes, you'll have to broach the sail to drop the float, opening the head-valve. No getting around that.

Skimmer's will get you eventually -- the only cure is to establish a 'submarine operating area' and inform all boaters on site as to that area and the need to keep out of it unless you're operating a submarine.

M

[redboat219]

What ever happened to this cool project?