Stream of bubbles

[umop_apisdn]

When sailing my weekender, I see a stream of bubbles trailing out behind the boat. They are about a foot under water, and near the windward edge of the boat. They are very consistent in their size and location.

Anyone else see these? Any idea what causes them? I am assuming that some kind of eddy or vortex near the bow of the boat is sucking air down under the boat?

Noel.

[Barry Pyeatt]

Many things can cause the little eddies and turbulance beneath the boat. Often it is no more than a little rough spot that just disturbs the flow enough to create a stream of bubbles. Most often they will occur off the tip of the rudder.

[ken connors]

try leaving the lid up on your porta-potti and see if they go away. you may have a combustion problem there :wink: :roll:

[waynemunro]

I have a theory on this one, as I have noticed this myself and wondered about it.

I think it is small amounts of water being entrained right at the bow through movement and wave action, these are then strung out into a long consistent line of bubbles as they move down the hull and move along the hull bottom, moving towards the wind a bit as the hull is tilted up that way.

I have a short video somewhere that I took of the underside of my weekender while travelling at about 1 knot (much faster and I can't hold the camera under due to the water pressure) and I could see a few bubbles doing this at that speed...

.. this is of course still mostly a theory.

I could find the video and downsize it for web viewing if anyone was interested.

Wayne

[Stump]

Yup, I see it too. I figure it is just the boats way to prove that it is moving. :wink:

[Russ Sylvester]

Mine did the same thing. Seemed like the faster the boat went, the more bubbles came out and in a straighter line.

I always figured that when the boat is reaching along, one side of the keel has a lower pressure on it than the other. Kind of the same deal as on the sail. This lower pressure would create a suction that would pull a little air down along the edge of the keel until it detached and came out the back.

I have no proof of this at all, it's just a theory that seemed to fit. Although I did see the rudder do the same thing a couple of times. It would pull a little air down the lee side of the leading edge and it would detach at the bottom.

Russ

[Mike Henderson (Oregon)]

Yep, I got 'em.

[capt jake]

I got 'em also. At times I can tell that they come from the bottom of the rudder, while other times I have the mystery bubbles as described. I never thought of air entrapment thoguh I see them on the leeward side of the boat.

Went out yesterday and it started out rather calm; light winds developing into nothingness. Noticed the bubbles at times. Then the wind changed, and changed in a hurry!! :shock: Didn't have time to look then as I was trying my darndest to keep Mom and Stepdad comfortable and trying to balance things in the blow (hard to move three people around in the cockpit with a tiller when it is blowing). It was ....'interesting'. Mom got miffed as she didn't understand my instructions when it came time to douse the main. We ended up motoring accross teh bay back to the launch point. I also ended up plain getting in the water to guide the boat on the trailer as the wind was still blowing quite hard.

[Guest]

I use to see a bunch of bubbles when I was a kid on the tv show with Lawrence Welk but always thought it was some fellow behind the curtains with one of those ringy things and a bottle of soap. Gee now I find out that it was a weekender boat now behind the stage. Gee have they been around that long?:twisted:

Heck you guys need to check for some grey moss on those rudders and keels.