Re-do your 4th diagram, increasing the volume of water to be the same as the 2nd. See where the water level ends up, especially vs. #2. That is the real point of "water channeling". It's not about flow, it's about level. Increase water level at the pump inlet & the pump finds it easier to prime & start pumping. Example: Let's use a square-cornered vessel, just so that it's easy to do the math to demonstrate. Our vessel has 1' * 2' flat bottom with squared-off "bilges". No motion, the bottom is perfectly level, & it doesn't matter where the pump is placed. If the pump needs 1/2" of water to prime & start pumping, we'll have to accumulate 144 in^3 (0.623 gal.) in the bottom of the ship before that happens. If we add a "water channel" of 1/2" that covers all but a 3" square, where the pump is located, it's only going to take 4.5 in^3 of water to prime the pump. That ~140 in^3 difference may be tough to recover from, if the rate of water flowing in is close enough to the pump's outflow rate. Water will seek the lowest level. Other forces (motion, mostly) will cause water to take an other-than-most-direct path to that lowest point. That path may or may not follow some "channel" cut into the bottom of a hull. More important than "channeling" is to create a "well" for the pump, so that it can be placed at that lowest point, where the water will end up. Ironically, excessive channeling (in terms of channel volume) can end up reducing the volume of that well, so that the pump can't prime/pick up water when there's still relatively little of it in the hull. "Channeling" can help direct water flow to the pump pickup, but won't fully counter the forces of motion caused not only by the ship propelling itself through the water & turning, but just from the bobbing effect of being on the water. Something I've wanted to do for a long time is build a fully transparent research ship, to help explore & demonstrate various things that happen inside a hull, particularly as water enters, collects, & gets evacuated; see what the real effect of water channeling is; see for sure if water really does "slosh" toward the stern (as some people think, affecting pump placement), etc. Sadly, that project is well down my "To-do" list. JM
It is both level and flow. especially in fast gun with the high pump flowrates. Level, so the pump can remove more water, and flow to direct the flow to the pump in a way that keeps the ship from becoming unstable, which is why bad water channeling is in some cases worse than none at all (personal experience on that one). There was a neat test I saw documented years ago, but I can not find now, where the navy was trying to simulate what actually caused many of its ships to sink and how to do the compartmentalization in a way to combat it. The uncompartamentalized trial always failed when moving not due to volume of water initially ingested but due to a instability/resonance in the flooding that would either roll the ship or pull it far enough to the side that it would flood almost instantly. Even some of the compartmentalized trials suffered a similar fate. Ideally you want to entice the water to flow where it will naturally with your water channel and where it will go when you are heavy on water. You also want something deep enough that you can prevent a sustainable (I.E you are not going to sink from it) volume&flowrate of water from sloshing side to side in a hard turn... There is not much you can do about sloshing in our ships other than internal component resistance once you are going down anyways (that may be before or after you can pull the ship out of the water per your rule set...) As far as why I always end up putting the pump in the stern... here is my reason: Every single ship I have, even when sitting still, sinks stern first. Almost every ship I have ever seen sink locally has either rolled turtle or sunk stern first. All my ships, when they get low in the water, get a bit lower in the stern than the bow so long as they are not accelerating. While the water will slosh back and forth based on acceleration/deceleration, if I am fleeing with a heavy ship, at best I will be running in a straight line with no acceleration at constant speed... meaning that the water will be deepest in the stern. Not much I can do about side to side sloshing, or having to slow down to turn so as not to roll...
What's up with all this "I sink stern-first" stuff? Why would anyone WANT to sink stern-first? Your props get jammed into the weeds, your rudders get jammed into the mud, your steering servo could get stripped out... It's just not a great way to sink. Personally, I prefer to sink BOW-first. And I take steps to ensure that that happens. On the ships that don't naturally sink bow-first, I place several blocks of foam in the rear end of the boat, directly beneath the deck. This doesn't affect the ship's handling while there's only a little bit of water inside, and isn't enough to prevent the ship from sinking. It just ensures that the rear end is more buoyant than the front end, and guarantees that my ship will sink bow-first. Not only is bow-first a more elegant and beautiful way to sink, controlling how the ship will sink helps me design a reliable recovery float.
Most people tend to take more holes in the bow than the stern, it being a juicer target and all. If you sink bow first these holes go underwater sooner and speed the sinking process, also if you are getting low in the bow and go forward you can drive yourself under. I don't see being damaged from sinking stern first as being an issue if you build a robust drive train.
I have tried in the past to get ships to sink bow first... never really succeeded. There is also some doubt about the legality of large blocks of foam for buoyancy sake in IRCWCC.. at least there is around here in WA when we chatted about it. So I simply build stronger rudders, props, etc.
My PE goes down on a even keel, till the deck is getting water over it, then the bow drops goes down first, but when she hits the bottom she is only at about a 15 deg angle at the most.
HI Guys.. What material is being used to make water channeling? I've used several options but am wondering what others are using? I've heard some guys using self levelling cement? Can anyone comment on its results? Thanks, Mark OAF
Mark, self-levelling concrete filler is probably the most popular choice, for many reasons that I'm sure others on this forum can tell you about. I've seen it used, and functionally it works well. My only piece of advice is to not use that stuff in high-quality wooden hulls. A high-quality wooden hull isn't just a hull, it's a work of art designed to show off the builder's craftsmanship. To cover that over with a solid grey mass, especially when transparent alternatives are available, is a crime against the ship. In all of my high-end wooden ships, I use epoxy resin in place of the concrete filler. It's mostly transparent, seals the wood, and looks really good. Of course, if you DON'T have a high-quality wooden hull, then self-leveling cement filler is great stuff. It can be used to cover blemishes and mistakes made in a lower-quality wooden hull, and of course its synthetic coloration doesn't stand out in fiberglass hulls.
I used it in my Baden with a dramatic improvement. It did make it a litlte heavy but I plan to move to NIMH soon and at that time will pour some more.
