Use a bubble machine to release bubbles at certain intervals or under certain conditions related to the vaporetto, which are like the buses of the canals. Initially, for simplicity, the bubbles could be timed according to the boat schedule. Later, the machines could be adapted to react to motion, either of the boat or the people. A further stage of interaction may allow passers by to activate the machine.

Underlying Issue

The bubble machines would be intended to bring attention to the turbulence caused by the boats, particularly when they are docked. Turbulence is a result of the boat's propellers (props) turning underwater. The props do not cause wake, or any other particularly visible disturbance, because the water they displace is replaced by more water as quickly as it moves. The displaced water continues away from the props interacting with the water it collides with creating small localized currents of sorts. If the turbulence occurs near enough and in the direction of the docks and building foundations, it begins to erode the surface. Each bit of turbulence does not do significant damage by itself, in fact the effect is almost negligible. Due to the vast number of boats that patrol the canals daily, however, the turbulence's effect becomes much more noticeable over time. The problem is particularly bad near common docks, such as those for the vaporetto. Boats will typically run the motors slowly while docked so as to stay close to the dock and allow people to board more easily. As a result, large sections of foundation have been eroded considerably around such areas.


The bubble machines would likely be placed around average head level. This will allow the bubbles to float high enough to be seen by many people, while still being low enough for the nearest people to notice. To bring attention to the problem of turbulence, a sign with some brief facts or a short paragraph with a picture might be placed near the machine, likely just below it.
The bubble machines themselves have a variety of features to be considered, such as power sources, bubble production rates, and duration of time a single tank of bubble solution lasts. Preferred machines will have long tank durations, and battery power. The amount of bubbles that can be produced with one tank of solution is the most important aspect of the machine. If the reservoir does not last long, someone will have to frequently refill it, which a nuisance as well as a notable expense. Some potential machines are:

Manufacturer Cost Approx Duration Dimensions (Inches) Other Features
Eliminator Lighting1 $89.99, $59.99 on sale About 4 hrs 10 1/2” x 9 1/2” x 8 1/4" 1 Litre tank, 66" cord for wall power
AmeriMark2 $39.99 "Hours" 10"H x 9 3/4"L x 6"W 8 oz Tank, Plastic, Power Switch, Battery or Wall Power
Gazillion Bubbles3 $25 after S&H unspecified 7-1/4"W x 9"D x 10-1/2"H Includes 32 oz bottle of "Special Solution"4, Battery Power, Adjustable Blowing Angle
Favor Frenzy5 $14.95 unspecified 7" x 4 1/2" x 3 3/4" Battery Powered, Small
Product Links
1 [http://www.eliminatorlightingdirect.com/Bubble_Machine_p/16-fslash-410.htm]
2 [http://www.amerimark.com/cgi-bin/amerimark/postkey_find.html?cm_re=celebros-_-center-_-search%20promo&keywords=26780]
3 [http://www.qvc.com/qic/qvcapp.aspx/view.2/app.detail/params.aol_refer.false.tpl.detail.msn_refer.false.item.T24088.ref.GBA?cm_ven=GOOGLEBASE&cm_cat=SPORTS%20%26%20LEISURE&cm_pla=TOYS&cm_ite=T24088]
4 Special solution claims to make bubbles that are more colorful, last longer, and float higher
5 [http://www.favorfrenzy.com/proddetail.asp?prod=707-110-05]

note that specific durations are seldom listed, but those that are listed for constant use, so the duration listed can be spread out over the course of the day(s).

Most bubble machines seem to only last for a few hours of use on one tank of solution. The working duration for our purposes depend on how often boats stop at a given station and how long the machine runs for at each activation. For estimation, I will use the 4 hour duration. If the machine is producing bubbles for only 1 minute at a time, and boats stop and trigger the machine every 10-15 minutes, then one tank will be used up in 40-60 hours. This will likely be extended over more than 40-60 consecutive hours if the boats do not run during certain times at night. The worst case, according to this, will require the tanks to be refilled about every day and a half or 2 days. Best case in this example, assuming the boats don't run between 12am and 6am, the tanks would be filled about every 3 days. Auxiliary tanks or other storage means could be added to extend the operating time.

Another consideration is the triggering of the machine. Only one of the models mentioned above advertises the presence of a power switch, and it is unclear if the others have one or not. Either way, some components and circuitry would need to be added in order to trigger the machine off of motion, and deactivate after a certain amount of time. The other triggering concern is what to detect as a trigger. If the machine is triggered off of a general motion sensor, it will likely run constantly. In order to detect only the boats, a sensor should be placed on the side of the pier, and would trigger when a boat came near. Care would need to be taken in the design of such a sensor to ensure that an approaching boat does not crush the sensor against its hull.

The final configuration chosen uses this bubble machine. A pair of sunSPOTs act as the control system. One floats in the canal and reports to the other when it experiences significant movement. The second sunSPOT then activates the MOSFET trigger of the bubble machine, and turns it on.
Technical note: from sunSPOT, 15V turns the machine off. 0V turns it on.

Concept Art

Concept Art

A rough idea of the layout of the machine.

This is a general image with a dock on the canal. The bubble machine would likely be placed around the waiting area (shown here), or possibly near boarding point.

Here are some better images:

Implementation proposal

Use SunSpots. One to detect the approach of the boat, then that will tell the others to start the bubble machines.

Final System

Use the Gazillion Bubbles machine


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