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Careful with that Silicone AntiFoul


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Thats a good article. But I need to correct one error. 5 Boaties sitting around discussing the subject will result in 10 answers, not 6. :-)

The overall article highlights the one common point. There is no one simple answer and for every attempt to reduce Hull resistance through the water, there is a whole new set of Physical laws that fight against you.
There is one important point that always needs to be kept in mind. Friction and Resistance to movement is as much your friend as is your enemy. If you have no friction/resistance, you will never sail into the wind at all, nor even sail beam on and you will only ever go as fast down wind as the wind itself. So there needs to be some form of resistance so as things like Hull shape, Rudder shape, Keel shape/size and length, all work in combination, so as to create a forward movement when another force is applied (ie wind in sails). With no friction and resistance, water would simply flow around rather than over a surface. Remember that all the shapes of a Hull are such to create lift through the water.

Said another way to make it easier to understand, a Car tire will give you greater grip the wider it is. But the friction ends up increasing as well, so it's harder to roll on the road and you use more fuel. If you decide to reduce that friction to save fuel, lets say you spray oil on the surface of the tire as you travel, you end up no longer staying on the road. You cannot turn corners, you cannot maintain a straight line and you cannot accelerate etc.

 

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Kim Klaka used to hang out on rec.boats on Usenet.

He is (used to be?) a researcher at an institute or uni in western Australia. Lars Larsson used to be a hydrodynamics professor at the university I got my degrees at (*). My brother was one of his PhD students. My brother met Kim Klaka during a trip down under in 1995.

Now this pops up here. Small planet :-)

/Martin

*) My boat was built in the workshop of the marine engineering department of that university.

Usenet: https://en.wikipedia.org/wiki/Usenet

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I found that article years ago and kept it for occasional re reading, most people know its important but just not how much advantage it is to have a smooth clean hull. 3% is free money! 

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So I ended up doing a complete antifouling 'facelift'. It cost me a month of our sailing season plus, of course, a bunch of money. I went for Hempaspeed TF which is not silicone based so this post is off topic.

Hempaspeed TF is a bit odd to apply as it is rather viscous and I found it would not flow to a smooth surface which is a bit of a dissapointment after all the work. It is glossy which is also a little odd for an antifouling in my experience.

It will be interesting to see if algae and barnacles like it.

/Martin

PS It is my understanding that Hempaspeed TF is currently only released in Scandinavia.

817912780_frdigmlad_5e_juni_3.thumb.jpg.d0aeca8bfce501d741d994fbf3921755.jpg

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Hempaspeed is a "Hydrogel" type AF. In other words, once in the water the surface becomes slimey/slippery to the touch. The idea came about due to the fact that Fish have a natural Hydrogel over their skin which prohibits Barnicles growing on them. Hempaspeed is designed to perform in a similar way.

Please keep the forum informed on how you find the performance of this.

As form smoothness, I have not used it myself, so cannot comment. It is designed to be applied by roller or brush, so I suspect that the type of roller might be important. One designed for applying Gloss top coats would likely be required. ie. Short Mohair.
 

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Yes, I intend to keep you posted.

Yes, short mohair roller. I was coached on the procedure by a recently retired Hempel employee who my old boat building buddy knows through his job as a marine engineer. Disclaimer: my coach admitted that he had no first-hand experience of applying Hempaspeed TF,

I will try to quantify and document the 'smoothness' before launching.

/Martin

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3 hours ago, MartinRF said:

So I ended up doing a complete antifouling 'facelift'. It cost me a month of our sailing season plus, of course, a bunch of money. I went for Hempaspeed TF which is not silicone based so this post is off topic.

Hempaspeed TF is a bit odd to apply as it is rather viscous and I found it would not flow to a smooth surface which is a bit of a dissapointment after all the work. It is glossy which is also a little odd for an antifouling in my experience.

It will be interesting to see if algae and barnacles like it.

/Martin

PS It is my understanding that Hempaspeed TF is currently only released in Scandinavia.

817912780_frdigmlad_5e_juni_3.thumb.jpg.d0aeca8bfce501d741d994fbf3921755.jpg

Sleek looking boat Martin … very little rocker by the looks . What’s the design and where’s the keel/ centreboard ? 

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