How-To Article ...by Patrik Tegelberg
Learn how to make this automatic water bailer that works without any moving parts!
Here will describe a water bailer that can readily be made by everyone using easily available and inexpensive hardware. One only needs a short length of brass tubing and a short matching hose (silicone tubing). The end result is no more complicated than can be seen in picture 1 as the loop in the stern.
Picture 1. The
looped hose in the stern is a Bernoulli water bailer.
I call the water bailer a Bernoulli(1) water bailer because it utilizes a principle that is called the Bernoulli principle.(2)
V2 / 2 + g * h + p / r = constant
...states that as the velocity (v) increases, the pressure (p) decreases. So if we have access to high velocities, which we hopefully have, we can potentially have access to low pressures i.e. suction.
The loop in picture 1 leads from a pickup tube (placed where the water is expected to be) to a hole in the bottom of the hull outside which the water passes at high velocity and thus creating the suction needed to transport the water from the inside to the outside. The loop of the hose is such that its highest point is above the waterline when the boat is at rest in the water. This creates a barrier to stop the water from flowing back into the hull in case of a stop. If the water were to reach around the loop it would become a siphon and the boat would fill up with water. To prevent this from happening in case of a wave or other disturbance hitting the boat, there should be a sufficient margin from the highest point of the loop to the waterline; but keep in mind also that the higher the loop the more suction is needed to start the bailing.
When the boat comes to a stop the water rushes forward leaving the pickup dry to clear the hose of water to prevent the siphon to start immediately, or that is the theory and it has worked for me so far. When the boat is accelerating the water is rushing to the stern and is climbing up the transom to reduce the water column height needed to overcome to get bailing started, this works to our advantage and it is wise to place the pickup accordingly, that is far back close to the transom. I have used 5 mm inner diameter tube and hose. To get some real throughput the hose must not be too small.
The trickiest part is to place and shape the hole in the bottom. It should be shaped kind of like a reversed water pickup with a small ramp in the front and a smooth aft edge. The thing that must not happen is that the water hit the aft wall and start pushing up into the boat. Also for this to work the hole must be surrounded by water so it must be some distance from the transom so that the water coming off the ramp has time to reconnect with the bottom of the hull before the transom. I put my hole about 4 cm (approx. 1.5 inches) forward of the transom as can be seen in pictures 2,3 and 4.
Picture 2. Hole
placement of drain.
Picture 3. The
brass tube is folded to yield a ramp, some tough putty would suffice to. The
chip in the gel coat is not part of the construction.
Picture 4. The
smaller brass tube is just a dummy drain used in the pit.
The no moving parts character of this bailer renders it a very low maintenance unit. As a conclusion it can be said that I needed a bailer for my boat and this delivered a shipshape solution!
(1) http://en.wikipedia.org/wiki/Daniel_Bernoulli
(2) http://en.wikipedia.org/wiki/Bernoulli's_principle
The true test for me was trying this out in a relatively very slow boat. As per this youtube clip.(After others on the water subsequently sprayed prop wash into my hull I figured that the system worked quite well):
It worked for me.
Cheers
Craig
Well done. Just as I intend to do with my mono.
Nice to hear that this works good.
I will use two double water inlets. One for the engine (40 cc Blata) and one for cooling flange and exhaust.
In addition to that I will mount two reversed water inlets to work as water outlets (bailers). One on each side of the keel, as the boat is wooden build on a huge keel.
So I'm in for four double in- and outlets all together. And a nest of tubes, as you can guess.
Cheers!
Woodie.
Having test finished a 48” wooden scale Huntsman boat (that I started building many years ago) I decided to try out the Bernoulli auto bailer (good safe opportunity to try it out). The windows on the top of this boat were left open so when run with other surface drives plenty of spray went through them. When my boat came back home it was surprisingly dry inside so the method definitely seems to work.
And it is nice to know that the system requires zero maintenance and when the boat is stopped on the water there is zero leakage of water back into the hull.
Okay first image shows the boat on the water.
Second image shows the reverse mounted dual pick up viewed from the hull bottom.
Third image shows the inside minus the connecting tubes (prior to finishing with a good clean up of the fibreglass paste used).
Two silicon tubes lead into one looping over for the vertical pick up pipe. That gives sufficient vacuum suction to pull any water up the single vertical brass pick up tube to allow for siphon action to help drain any excess water out of the hull when on the move.
Cheers
Craig
