To scupper or not

[Boris]

Something like this ??

 

[Matt_E]

here....


i get his idea, but idk if when the ski is upside down you would get a great seal. water closing a scupper is one thing air closing a scupper is another thing.

I think the air will push both of them open.

My one-way valve is letting out air because the air is at higher pressure than atmosphere (getting pushed by water from below) NOT because the valve is upside down.

 

[Matt_E]

Something like this ??

During normal operation, I am convinced that any water trying to get out of the bilge will close that first valve.

 

[Matt_E]

Matt,
I phrased that last part wrong, if the scupper is held closed, and your air intakes reach the bottom of the hull, what would cause the water to come in? Just trying to brainstorm on here.
Bri

The air inside the hull is pressurized by the water from below. The air is pushing the one-way valve open.

The valve is working as intended - this is the very same mechanism that makes it evacuate water quickly.

 

[Flash-FX]

How about a duckbill valve with the stock bilge and FX-1 style hood air inlet design. All the SJ hoods seem to do nothing but LEAK in EXCESS water. What's with that? Or do you guys like to do back to back subs and fountains all day?

 

[Boris]

During normal operation, I am convinced that any water trying to get out of the bilge will close that first valve.

I'm sure that the water will try to close the first valve but with the ski bouncing and pitching you never know.
If I have some time tomorrow I will pick up a couple valves and try to rig something up.

I never had an issue with my current setup (single one-way and a scupper) but this sounds like a fun little project.

 

[Matt_E]

How about a duckbill valve with the stock bilge and FX-1 style hood air inlet design. All the SJ hoods seem to do nothing but LEAK in EXCESS water. What's with that? Or do you guys like to do back to back subs and fountains all day?

I think it's particularly bad on skis with bad hoodseals and other water ingress problems.

My hood doesn't seal well, and the pole bracket lets in water, too.
I think duckbills would work well.

 

[SJ/XPBri]

I guess the problem I'm having is this, where is the water coming in from in the first place? If your air intake is all the way to the bottom of the hull, it's above the waterline when the ski is upside down. Where else can the water enter the hull to allow the scupper to affect the inflow of water? I'm starting to think the scupper isn't the problem, it's most likely the air breathers that people use, or a crappy hood seal.
Bri

I type too slow LOL

 

[Boris]

I used duckbills on my couch and they did a great job.
The only problem with the duckbills was that every once in a while a piece of zip tie would get stuck in them keeping them open just enough to let water in. Not a big deal but I did almost sink my couch once when it was docked.

 

[Matt_E]

I guess the problem I'm having is this, where is the water coming in from in the first place? If your air intake is all the way to the bottom of the hull, it's above the waterline when the ski is upside down. Where else can the water enter the hull to allow the scupper to affect the inflow of water? I'm starting to think the scupper isn't the problem, it's most likely the air breathers that people use, or a crappy hood seal.
Bri

I type too slow LOL

The air intakes are always below the water line when it's upside down. How else would it work?
Air intakes let in air when it's right side up.
That necessarily means they will let in water when it's upside down. Has nothing to do with whether they are crappy or not The ski must let in air to work right. That means it will let in water.
The scupper accelerates that.

 

[Boris]

I guess the problem I'm having is this, where is the water coming in from in the first place? If your air intake is all the way to the bottom of the hull, it's above the waterline when the ski is upside down. Where else can the water enter the hull to allow the scupper to affect the inflow of water? I'm starting to think the scupper isn't the problem, it's most likely the air breathers that people use, or a crappy hood seal.
Bri

I type too slow LOL

The scupper doesn't let water in, it relieves the built up air pressure in the bilge thus allowing water to replace the air quicker.

 

[SJ/XPBri]

The air intake (think of the factory setup) is designed to extend the inlet of air to the bottom of the hull, so when the ski is flipped upside down, the tube is above the waterline- no water enters through the air intake. Now for those people that run the typical pool hose breather into the pole, this system no longer works.
Bri

 

[Matt_E]

The air intake (think of the factory setup) is designed to extend the inlet of air to the bottom of the hull, so when the ski is flipped upside down, the tube is above the waterline- no water enters through the air intake. Now for those people that run the typical pool hose breather into the pole, this system no longer works.
Bri

Incorrect. The tubes extend to the bottom so that water goes directly to the bottom, and not on top of the engine.
Water will indeed come through those intakes when it's upside down.
Remember - that ski (particularly the bilge) is heavier than water. It wants to go down. The only thing holding it up is the air in the bilge.
And that air has a nice easy escape path through the scupper.

 

[Boris]

The stock setup relies on trapped air in the bilge to add buoyancy to the hull keeping the breather tubes above the water line when the ski is inverted.
When you relieve that air pressure the hull quickly looses buoyancy and starts to sink dragging the breather tubes below the water level.


My "pool style" pole breather tube extends all the way to the bottom of the hull instead of just barely making it past the pole bracket.

 

[demolition_x]

Incorrect. The tubes extend to the bottom so that water goes directly to the bottom, and not on top of the engine.
Water will indeed come through those intakes when it's upside down.
Remember - that ski (particularly the bilge) is heavier than water. It wants to go down. The only thing holding it up is the air in the bilge.
And that air has a nice easy escape path through the scupper.

i want to say that water will not travel all the way up those hoses.

i think that was their intent along with the bringing the water directly to the bottom of the ski when right side up

 

[SJ/XPBri]

I've got it LOL
run a string down the scupper tube, attach it to the scupper "door", than at the other end attach it to a small pulley- then put a weight on the end of it. when the ski flips upside down- the weight hangs in the hull and pulls the scupper door shut. under normal operation the door opens without any problems. Although there probably is a way to make this work, I know it's pretty impractical.
Bri

 

[Matt_E]

i want to say that water will not travel all the way up those hoses.

i think that was their intent along with the bringing the water directly to the bottom of the ski when right side up

The water will, 100%, every time, travel up those hoses, provided that the air has a way to escape.
Try to picture this....the only way water will not travel up the tubes is if the air pressure is holding it at equilibrium.
The scupper prevents that. It lets the air out, bingo, water can move up the tubes.

Yamaha's intent is good & well, but the system you describe absolutely relies on the air being trapped in the hull.
Which it is not.

 

[demolition_x]

negative ghost rider....


your lucky i had some time to mess with this.

cup, straw, gum.

the top of the cup represents the scupper, inside of the hull open to atmosphere aka no pressure inside the hull. the blue line out side is the same height inside as the tube inside. put the cup in your plugged up sink filled with water. the water has to be above the tube for water to get in. since atmospheric pressure is acting on either side the water in the tube is the same height as the water outside the cup (hull). if there was no scupper aka the cup ad a lid the pressure inside the cup would be greater than the outside so the water in the tube would not go up the tube.

 

[SJ/XPBri]

Demo- good demonstration :Banane25:
I'm going to start selling my automatic closing, inverted ski, scupper sealers.
You get a piece of string, some glue, duct tape, a small pulley- and a fishing weight. I'm quitting my job tomorrow in anticipation of an early retirement.
Bri

 

[Matt_E]

Not buying it.

The ski is heavier than the water, it's getting drug down.
The only thing preventing that is trapped air.

The water from the bottom + the weight of the ski are compressing the air inside the bilge.
Normally, this would lead to a waterlevel inside the tubes slightly lower than the actual waterline.
HOwever, with a scupper, the air will not be pressurized. IT will simply escape, dropping the ski down further and further.


The fallacy with the cup is this: The cup is not heavier than water (or not significantly so) Use a steel cup and do the experiment. I guarantee it will sink.

Think carefully...the ski is not keeping itself buyant, the trapped air is. The scupper untraps that air.
I guarantee it.