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Reluctant to paint or clear coat my Foil

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Bajadrifty
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Reluctant to paint or clear coat my Foil

Postby Bajadrifty » Wed Feb 25, 2015 4:00 am

My foil is ready to ride but not clear coated or painted. I this necessary I would like to be able to modify it easily. it has the texture of peal ply on it. I have shortened the fuse tip after deciding front wing placement, and added a bunch of layers it's stiff
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Peter_Frank
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Re: Reluctant to paint or clear coat my Foil

Postby Peter_Frank » Wed Feb 25, 2015 7:44 am

It does not matter for you, just use it as is, so easy to modify.

Good luck with the foiling experiences :thumb:

8) PF

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Re: Reluctant to paint or clear coat my Foil

Postby TopLine » Sat Feb 28, 2015 11:25 pm

Painted is best - use good epoxy paint and sand back to smooth finish using 600 grade then 100 grade wet and dry. Always use a foam block as well.

Makes the ride so much smoother and gives you less chance of cavitation on wing. Parasitic drag is not your friend.

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Re: Reluctant to paint or clear coat my Foil

Postby revhed » Sun Mar 01, 2015 9:31 am

TopLine wrote: sand back to smooth finish using 600 grade then 100 grade wet and dry. Always use a foam block as well.

Makes the ride so much smoother and gives you less chance of cavitation on wing. Parasitic drag is not your friend.
TL,
Did you mean 1,000 g W+D to finish?
100 seems way to aggressive to me?
I like the foam block with factory attached sanding surface, I have seen these but never used.

Food for thought from http://www.boardlady.com/fast.htm

Making it Fast
a matter of finish

Water is pretty sticky: dip a paddle into the ocean and it comes up with much water attached. Move a board through the ocean – be it surf, windsurf, stand-up, or kitesurf -, and it will drag a substantial amount of water along, which, as it eventually cannot hold on to the bottom any more, emerges behind in the form of a wake. The energy that you generated with your sail, kite or paddle, went into accelerating not just you and your board, but this rather substantial mass of water as well.

To go faster, then, we need to decrease the amount of water “sticking” to your board – “reducing the drag” in techno-lingo, since the best wake is no wake!

In extensive tank testing for world-class racing boats, it was established 40-some years ago that a glossy surface has substantially more drag than a matte one. In tests I was involved in for an America’s Cup boat, we found that simply sanding a glossy bottom with 600 grit paper, reduced the surface friction by about 5% at ½ hull speed, i.e. at about 4.5 knots. Instead of sticking to the glossy bottom, the water molecules would be “tripped up” by the minute ridges left by the sandpaper. This slight turbulence would reduce the thickness of the film of water being moved along with the vessel (the “boundary layer”), and thereby reduce the overall drag.

Surfboards are traditionally finished super-glossy-shiny. Windsurfers, on the other hand, have long since followed the lead of sailboat racers and taken the gloss off the bottoms of their craft.

If you wonder if your bottom is too shiny, throw a cup of water at it: if the water beads, like it will on a freshly waxed car, then the surface tension is high, and therefore its resistance going through the water is high.

To change it to a low-drag surface, sand it in a circular motion with 600 grit wet & dry paper, until water thrown at it runs off in sheets – WITHOUT ANY BEADS forming.

Instead of wet & dry sandpaper, you can also use a “Purple Pad”, a Scotch brand synthetic wool pad designed to burnish metal and take off rust. Again, a circular motion is optimal.

To keep this fast surface fast, wash it now and then with soapy water; and lightly apply the Purple-Pad when the bottom appears yellow.


How big a difference will this make? After a bottom repair a while back, I decided to Purple-Pad the entire bottom of a windsurfing board. The owner noticed with a raised eyebrow, but did not comment on it when he picked up the board. However, he was back 4 hrs later, demanding to know what exactly I had done to his board: a friend, who had always easily passed him before, was no longer able to even keep up with him.

Or this recently from Shawn C: “I purchased an old Hifly 265 poly board that I used a couple of times and really enjoyed. I noticed that the board had a few small gouges on the bottom so I thought that I would sand them down using wet/dry 600 grit as you suggested. I then mistakenly waxed the bottom and had horrible performance on the water.


And although mostly for boats,
http://www.fsc.com.au/cproot/1076/3/kim ... bottom.pdf
As a guide, using 360 grade sandpaper will usually get you a
hydraulically smooth surface. This does not mean that if you give the hull a going over with 360 grade, you will have a hydraulically smooth surface. You have to work steadily
through the various grades from rough to smooth.

Not saying I agree or disagree with either of these just posted for thought.

I would think for most DIYers that respecting profile shapes and LE, TE sharpness, roundness are more critical to control before surface finish.
R H

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Re: Reluctant to paint or clear coat my Foil

Postby BrockDub » Sun Mar 01, 2015 2:40 pm

Try it with 600 Wetsand and a soft foam block. Use 45 degree sanding motions so as to not compromise the shape of the wing. If it looks good after that you can step up to 1000 Wetsand and do the same. If you notice a number of pinholes or highs and lows you can use a high grade marine primer such as AwlGrip 545 and spray on a light coat then sand again with 800 and then higher.
If you are looking for a quick easy way try these pads too. They work great and are easy to use and come in a variety of grits. http://www.jamestowndistributors.com/us ... ng+Sponges
Don't be afraid to fill in your screw holes with Filler or wax to get an extra edge.
Have fun getting weird on it and be as meticulous as your time allows.
Hope this helps.
B
www.brockcallen.com

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Re: Reluctant to paint or clear coat my Foil

Postby Arcsrule » Mon Mar 02, 2015 7:14 pm

nice work baha. is that your foil that ocean extreme sport posted up a couple days ago?

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Re: Reluctant to paint or clear coat my Foil

Postby TopLine » Mon Mar 02, 2015 8:43 pm

Yes sorry for my typo, I have fat fingers.

I used 600g wet and dry paper with foam block then did it all again with 1200g wet and dry. Important not to polish it afterwards, leave it as matt finish - as discussed in previous post by revhead.

I am racing my foils and noticed a difference when I painted and sanded. Maybe not a huge improvement on speed - possibly 15% or so. But found it to just be a much smoother ride.

I'm a big fan of having paint on my foil (I use white) it will help keep it cooler in the sun, give it protective coat from bumps and scratches, but most of all it gives me a hard base that I can wet and dry sand from time to time ensuring I have the most efficient surface on the foils and mast.

If you are going to race - look into a paint called DURAPOX made by Resene paints. Otherwise a good Marine 2 pack will be fine.

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Re: Reluctant to paint or clear coat my Foil

Postby revhed » Mon Mar 02, 2015 8:54 pm

TopLine wrote: I am racing my foils
Thanks for the paint info, amazing the difference a 2 component paint makes.
May I ask what foils you race? and good luck!
R H

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Re: Reluctant to paint or clear coat my Foil

Postby dwaynej » Tue Mar 03, 2015 7:39 am

"Two Pack" paints are really dangerous to work without the proper PPE and environment protection. Not something you want to do in the garage with a paper mask.

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Re: Reluctant to paint or clear coat my Foil

Postby revhed » Tue Mar 03, 2015 8:04 am

dwaynej wrote:"Two Pack" paints are really dangerous to work without the proper PPE and environment protection. Not something you want to do in the garage with a paper mask.
Well noted! :thumb:
I once had to do a large underground parking garage and with a Resin + catalist paint, a good cartridge mask was needed for sure!
R H


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