asymmetric water flow, ripple sound, hull, ideas?

I built a 17ft hard chine stitch and glue plywood kayak many years ago and have always noticed the following issue.  When the boat glides through the water, the left side tends to make an occasional gurgle or ripple as though the flow is not streamlined as well on that side.  The sound, or 'chaos/ripple' occurs near the left knee or foot area but hard to determine exactly, and certain speeds or boat positions have an effect. Doesnt seem to be any vibration in the plywood afaik, and I have looked for say a convexity or concavity or hull asymettry or bumps etc comparing the two sides but nothing, hull looks perfect, and the boat is fast and tracks straight.  But the left side seems to displace or flow through water or sometimes set up a ripple in a way that is less streamlined than the right side. And not all the time, just sometimes.  When the water starts to make noise on the left side edging towards the right side releives or smooths it out.  Kind of odd issue, not serious, but ideas? 

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RE: asymmetric water flow, ripple sound, hull, ideas?

hi jeff321,

if you have checked the hull as you have said and it is symmetrical with no concavities, i wonder if it could be the foot-brace through hull bolts and what you are hearing is the bolt heads (which are rounded shape) dragging through the water.  

if you have the through hole bolts on the sides and depending on where the water line is relative to the bolts, maybe there is a slight difference in height or when you paddle, a slight list that puts the bolt heads in the water on one side and not the other.  or depending on loading, sometimes they are in the flow, sometimes not.

it sounds like the right location and the only item i could think of on an otherwise clean looking hull that could creat a little gurggle....anyway....thats my guess absent any other information.

if you want to take pictures of your hull with the boat upside down and paste them here....we can take a look and tell you if we see anything.

you did not mention what design you are paddling....but a picture would be great.



RE: asymmetric water flow, ripple sound, hull, ideas?

I tracked down a mystery gurgle just like that to my paddle leash dragging in the water. Same location and same preliminary fix (lean to the right). Moving the paddle leash attach point mostly got rid of it, but just knowing what the cause was took care of most of the nuisance value.

Another mystery gurgle, especially in the Fall, was caused by leaves packing around the prow. In the Summer it's usually water weed. Going backwards and rocking the boat up and down takes care of that.

Finally, another paddle leash contribution is a rythmic sound that sounds like a dog with a whiney bark off in the distance. That's caused by the braid on the shock cord rubbing against the spray skirt at the edge of the coaming.



RE: asymmetric water flow, ripple sound, hull, ideas?

 h, and Laszlo,

Thanks, those are all good, serious, helpful ideas.  I had initially discounted the foot brace bolt idea because they are on both sides and I can only get the lack of streamlined flow (the gurgle) to happen on one side.  But the idea of an effect due to footbrace bolt location or even a paddling style that tends to lower the exterior bolts more often on one side are interesting ideas.  I think it will be worth to at least retighten them to reduce possibility of vibration and take another look just to see, maybe cover them temporarily, see what happens.  It isnt a paddle leash issue, I often dont use one here, but good idea.  Also its not the junk/leaves that accumulates at the bow sometimes, I thought about that right away and I know exactly what you mean about clearing by rocking the boat but have ruled that out as the issue here. The boat is an arctic tern 17.  I may also try applying tape, e.g. gorilla to a few spots on the left side just to see if a different type of surface near the bow might lessen the flow disturbance, although its hard to know where to try that since it visually looks fine, but still...  But good ideas all, thanks!

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