Revell Type VII SAS system float-valve

[Ligamin]

Hi, I just want to ask you, how perfect should seal the safety float-valve? After a year of slowly building my type-7, I am in trimming phases. And during the tests I found that float-valve for sealing dry hull do not seal so good. It works in 70-80 percent: in case of low pressure in dry hull and opened snorkel head-valve (under water of course) means that little flush of water continuously flow to battery space. That’s not great, because in this case the safety valve is not so safety. Yes, there must be a combination of accidents, but Murphy’s laws works perfectly. So back to question – how watertight should be the valve from design point of view?
Thanks
L.

[He Who Shall Not Be Named]

You're right, the safety float-valve should work ALL THE TIME. And your testing protocol is a good one -- it identified the problem under real-word conditions. I applaud you for that. No, we don't want any water, as a constant stream, to get into the boat. However, as Manfred pointed out, a drop or two will get by the safety float-valve, so you should account for that.



Sounds like something is fouling between the rubber seat and pick-up tube within the safety float valve. Remove the inlet and outlet flexible hoses from the safety blow valve and blow medium pressure air through the outlet nipple of the safety float valve as you invert and set upright the SD -- this will work to knock off any foreign matter that got onto the internal rubber element. Reatach all plumbing and test as before.



If the blow-down fix does not work, remove the safety float-valve, remove its head, and clean and re-apply grease to the rubber element. Reassemble and test.

Let me know how that works out for you, L.

David

[greenman407]

Ligamin, You can buy one of those dishwashing sponges and cut a piece out of it and slide it into the bottom of the Subdrivers engine compartment and it will take care of that excess water by containing it. Its not uncommon for full size ships and submarines to have small leaks. Thats why they have bilges and bilge pumps.

[Ligamin]

@ David: Ok, there are result of yesterday’s tests. I removed safety float-valve from the dry hull tube. By helping 10ml syringe (hmmm, 0,33oz? sorry) I did simulate low pressure in dry hull. When the valve is dry (the valve body do not contain water), I am able suck up half and more of syringe. Ok, I return water to cup and try it again. And there a) the same situation –or- b) some water remains in valve body and the valve is watertight instantly after start of sucking. In case B the valve is so tight that I am not able suck even air. It looks like the floater is jamming in the valve body. So did try remove head, but it is so tight – how much of strength I should use? I don’t want damage the whole body…
@ greenman407: Sponge could help save a water, but the pipe from float-valve enter directly above of batteries. So they have a nice shower :) Maybe I could enter them into some rubber balloon. I am thinking about another device, some retention basin, which have functionality store a bit of water and expand stored air in dry hull. Some addon. :)

L.

[He Who Shall Not Be Named]

@ David: Ok, there are result of yesterday’s tests. I removed safety float-valve from the dry hull tube. By helping 10ml syringe (hmmm, 0,33oz? sorry) I did simulate low pressure in dry hull. When the valve is dry (the valve body do not contain water), I am able suck up half and more of syringe. Ok, I return water to cup and try it again. And there a) the same situation –or- b) some water remains in valve body and the valve is watertight instantly after start of sucking. In case B the valve is so tight that I am not able suck even air. It looks like the floater is jamming in the valve body. So did try remove head, but it is so tight – how much of strength I should use? I don’t want damage the whole body…
@ greenman407: Sponge could help save a water, but the pipe from float-valve enter directly above of batteries. So they have a nice shower :) Maybe I could enter them into some rubber balloon. I am thinking about another device, some retention basin, which have functionality store a bit of water and expand stored air in dry hull. Some addon. :)

L.

The body and cap are secured and made watertight with RTV adhesive -- which will part with a little torque. Don't worry about scratching the safety float-valve body and cap.











Grasp the body with pliers; grasp the head-cap with another set of pliers; twist; and separate the two. . After you clean off the rubber element (find out what's making the float hang up in the body and fix that first), apply some thick silicon grease to the rubber element and re-asseble. Use fresh RTV sealant to bond and make watertight the unit.

David

[Ligamin]

Hi, ok, I opened the float-valve. I didn’t find any jamming issue, dust, etc.
So I cleaned it and shine inner space (the float move smoother), apply silicon grease as you advised and re-assembly. The sealant was a little problem, because I did use one which was not so good (for metal), but the second one (what I have) fix the head to body well and watertight.
Test phase. Ok, the functionality looks much better. However there are some hints to discussion.
When I press the water (I am apologize, English is not my native language…) from bottom manifold slowly then – in most cases - works well and pass about 1ml of water, or (occasionally) close immediately. If I press water more quickly, the floater don’t react so fast and pass everything (10ml in my case).
When I suck the water from upper manifold (it is more nature to situation I think), the floater close the vent immediately (in most cases) or pass about 1ml too. The speed of sucking has influence too, but not so high.
So, it is about float reaction. I thought about some diameter restrictor (to slow water but not the air) and about some expansion tank addon (to store water and increase air capacity). By the way, the pump, how many litres of air per minute is able pump up?

Photo link below

[Sam Victory]

Hi, I'm new here and it is my first time to post. You can call me Sam V. I'm sorry that my English is not so good, because English is not my mother tongue, but I will try my best to express what I want to say. I emailed Mr Bob Martin earlier to share some of my safety float valve improvements. When I read this post, I thought that the floatation foam might not be so sensitive to water with pressure, so there is a certain possibility of leakage.
The following text was taken from an email I sent to Mr Bob Martin：


Safety float valve improvement:
The original safety float valve has some problems and in some cases it may not be safe, and there are several extreme cases:

case1: when the submarine is at a certain depth (which may be deep), the snorkel head valve happens to be knocked off or damaged or accidentally opened (which is rare) , so pressurized water might flood into the safety float valve;

case2: If LPB starts before/after the snorkel head valve is damaged, high-pressure water may still be injected into the safety float valve;

case3: If the LPB shuts down after starting for a period of time and the submarine is still at a certain depth and does not totally come up, then the snorkel head valve is damaged and opens. This is the most dangerous case, high-pressure water will quickly suck into the safety float valve because of negative cabin pressure.

The original safety valve design has the following features:
1. The floatation foam is placed directly on the bottom copper tube, and the floatation foam has a high counterweight, so that the foam become less sensitive to the buoyancy of water . In normal operation, if the water is above the bottom pipeline of the safety float valve, the floatation foam will float up for a very short distance (because the large counterweight makes it insensitive to water buoyancy), and then the water at the bottom of the safety valve will be sucked away by LPB when the submarine floats up. Only does a large amount of water flood in, the safety float valve will float a large distance to seal the air port to prevent the flooding water.

2. Only for slow water (that is, small water pressure), the floatation foam is effective. The water slowly floods in, and the foam floats up to seal the top air port. So the high pressure water and even negative pressure with high pressure water make it difficult for the original safety float valve handle these situations.

Therefore, I improved the original structure that you can see in the picture : Add a circular rubber pad (with a certain thickness )with a hole in the middle above the water storage area(colored in green) in the picture. Also, the pad has an angle to allow water to flow naturally through the center hole. The material of it is not only rubber element but also can be resin 3D printing. The rubber pad is glued with silicone to the safety valve , of course the edge of the pad is sealed with silicone. Then reduce the counterweight of the floatation foam. The exact principle is the same as the original safety valve, but it is safer, adding a perforated rubber pad (or resin pad) for cushioning the flooding high-pressure water, as well as slow down the inflow of high-pressure water; Reduce the counterweight of the floatation foam in order to make the floatation foam more sensitive to water buoyancy. Even if the high pressure water can be quickly eject from the hole（may be rare), the floatation foam can quickly float, sealing the air port.

This design, without changing the principle of the original design, increases the sensitivity of the floataion foam, and the rubber pad can give high pressure water a buffer, which can greatly increasing the safety factor. Of course, there are problems with this design~is the of the size of the small hole in the rubber pad , the small hole should be able to drain water easily if the flooding water floods through the pad~may be more than 3mm in diameter.

[Sam Victory]

For snorkel head valves, they are divided into those used in WWII submarines and modern submarines. Modern submarines have snorkel head valves up high with the air inlet facing downward, which I think is very safe. But for WWII submarines, the snorkel head valves are lower and the air inlet faces upwards, so they look relatively less safe. So if for WWII submarines: placing the snorkel head valve with the air inlet facing down, would it become relatively more reliable?

[redboat219]

MFR1964 made a water catcher for any stray drops that made it pass the safety float valve https://forum.rc-sub.com/forum/build...i-to-rc/page16

[Sam Victory]

MFR1964 made a water catcher for any stray drops that made it pass the safety float valve https://forum.rc-sub.com/forum/build...i-to-rc/page16

I left some space at the bottom of the improved safety float valve to store the droplets. Normally, the water doesn't drop too much, and the safety valve is always working. As the submarine floats, the LPB sucks up the water from the bottom of the valve. The safety valve is designed to be simple, reliable and can be placed anywhere within the WTC, making it extremely flexible.The original principle of the improved safety valve remains unchanged . What I improved is: reduce the counterweight of the foam to increase sensitivity of the floatation foam to water buoyancy, so that the valve can effectively resist water with pressure; secondly, the resin gasket also has a certain buffer effect on the pressure water.
Sam V

[trout]

There are considerations in designing a system for market. David made great system, does that mean it cannot be improved? Of course not. Some improvements may not be cost effective to manufacture. That is where we as assemblers of subs can use our creative juices. Sam V. I like your ideas and they may have merit. I made a droplet catcher in my system (the grey pyramid shaped tank) to resolve the minute amount of water that inherently will happen with a SAS system. The accumulated water gets sucked out when the pump runs.



I can imagine that even with your WWII valve, a water drop would catch or hang on the opening where the valve meets and get sucked in by the rush of air. That being said, build it and show us if it is an improvement. It helps us all get better.

[Sam Victory]

There are considerations in designing a system for market. David made great system, does that mean it cannot be improved? Of course not. Some improvements may not be cost effective to manufacture. That is where we as assemblers of subs can use our creative juices. Sam V. I like your ideas and they may have merit. I made a droplet catcher in my system (the grey pyramid shaped tank) to resolve the minute amount of water that inherently will happen with a SAS system. The accumulated water gets sucked out when the pump runs.



I can imagine that even with your WWII valve, a water drop would catch or hang on the opening where the valve meets and get sucked in by the rush of air. That being said, build it and show us if it is an improvement. It helps us all get better.

Thank you, Sir, for your advice. As a young man, I still have a lot to learn. Indeed, practice is the mother of wisdom. Unfortunately my time zone is 12 hours away from the US, I'm in the daytime and the US is at night, but that still doesn't matter.

[He Who Shall Not Be Named]

For snorkel head valves, they are divided into those used in WWII submarines and modern submarines. Modern submarines have snorkel head valves up high with the air inlet facing downward, which I think is very safe. But for WWII submarines, the snorkel head valves are lower and the air inlet faces upwards, so they look relatively less safe. So if for WWII submarines: placing the snorkel head valve with the air inlet facing down, would it become relatively more reliable?

Been there. Done that. Got the T-shirt.


David

[redboat219]

There are considerations in designing a system for market. David made great system, does that mean it cannot be improved? Of course not. Some improvements may not be cost effective to manufacture. That is where we as assemblers of subs can use our creative juices. Sam V. I like your ideas and they may have merit. I made a droplet catcher in my system (the grey pyramid shaped tank) to resolve the minute amount of water that inherently will happen with a SAS system. The accumulated water gets sucked out when the pump runs.



I can imagine that even with your WWII valve, a water drop would catch or hang on the opening where the valve meets and get sucked in by the rush of air. That being said, build it and show us if it is an improvement. It helps us all get better.

Can you post more photos of your drop catcher?

[trout]

Can you post more photos of your drop catcher?

It is in my Skipjack build.
https://forum.rc-sub.com/forum/build...skipjack-build