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To wax or not

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Old 02-10-2011, 01:36 AM
  #1
SimonsDad
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Default To wax or not

Hi All,

Just finish my first IOM, a nimbus 3 constructed as glass over balsa planks.

I've spray painted the hull and got a reasonable surface finish but I was wondering if I should try and wax it to a high gloss or if thats just going over the top.

Anybody else wax their boats and if so, what product did you use?

Cheers,
Andy
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Old 02-10-2011, 11:20 AM
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DMYC 42
 
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Default RE: To wax or not

Although this may sound like a good idea, it isn't. At least if you are going to race. It will make the boat slower.
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Old 02-14-2011, 08:24 AM
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Al Stein
 
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Default RE: To wax or not

I'm just chiming in because the truth is counterintuitive... what DMYC 42 says is the truth: don't wax.

The easiest to accept demonstration I've seen is to wax a bit of the hood of a car and then dribble water on adjacent waxed and unwaxed parts of it... notice that the water does its darndest to resist flowing across the wax while it'll flow smoothly over a dull, unwaxed area.

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Old 02-15-2011, 03:02 AM
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SimonsDad
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Default RE: To wax or not

Thanks for the feedback.

Counterintuitive as you say so Im glad I asked!

Thanks again,
Andy
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Old 02-21-2011, 11:50 AM
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Default RE: To wax or not

I understand it diferently. One thing is to apply a coat of wax and leave it on to get a water repelent hull. Another very diferent isto water sand the hull with fine sandpaper and then use polishing wax for shiny finish. After the shine we can get the wax off with water and soap.

The question is about sainy hull, not waxed hull.

Tato
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Old 02-21-2011, 02:35 PM
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Al Stein
 
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Default RE: To wax or not

Tato I don't think I'm understanding the difference you mean.

We did wet sand our dinghies in college racing, but where I was we never put wax on the wet sanded bottom. I would think that the wax would still make it harder for the water to flow over the surface... is that what you meant or does it just not happen that way?
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Old 02-21-2011, 11:22 PM
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Well I for one do sand and polish the bottom of my boat, a few years ago I used to just sand the bottom but then we got to testing some of the new polymer coatings and found that it was faster, the polymer coating is not a wax and does not act like one, I aply 2 coats the night befor a race, it takes 12hrs to cure, the one I like best is RejeX, Rain X also works good, just my 2 cents
John R.
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Old 02-22-2011, 05:17 AM
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Al Stein
 
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Aha!
Thanks John... that sounds very interesting and I have a brand new RG65 hull to experiment on!
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Old 03-04-2011, 02:38 PM
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Default RE: To wax or not

Of course polishing and buffing to get a high gloss is NOT the same as waxing. Wet sand from 400 to 1000 or 1500 grit, then apply some "auto body shop safe" polishing compound on a buffing wheel. buff the bull all over, and buff until the compound drys to a haze. Use the buffing wheel to remove the haze to get the best gloss. The "Auto body shop safe" is the important part, as there are NO waxes or silicones! OReilly's auto parts carries several different grit polishes.

The better the paint, the easier it is to get a great finish. Spray can paints will always be a bit soft, while two part urethanes or epoxy's are best.
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Old 03-06-2011, 08:10 AM
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the idea here is that the wet sanded surface is microscpicly rough and as the water flows over the surface a boundry layer of turbulence is formed. this boundry layer of tiny edies, actually "detacthes' the hull from the water's drag and creates less friction, thus a faster hull. when the hull is waxed and 'microscopicly smoother" that boundry layer of turbulence is calmed down andthe capilary action of water attempts to hold the hull still, slowing the hull down.
this phenomena was discoverd when America cup boats converted from wood to fiberglass. the common practice was to wax them down, at first. then, one of the winning teams were seen wet sanding the hull in prep for a race and the cat was let out of the bag. i can't recall which team it was, though. from that point on,subsequent research by virtually all theams provedthat a microscopicly rough hull was faster.
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Old 03-07-2011, 05:59 PM
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I think a better description is that the hull grabs a layer of water molecules. There is less drag when water molecules slide past other water molecules than when water molecules bump and bounce over, and are repelled by wax molecules. I agree that the micro scratches cause small turbulance, like turbulators on airplane winge, to help the water flow stay attached in the low pressure areas of the hull.

To a water molecule, a hull wetsanded with 400 grit looks like the Smokey Mountains, where a hull sanded with 1000 grit and rubbing compound looks more like a gravel road to a molecule. My opinion only!
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Old 03-08-2011, 01:02 AM
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Default RE: To wax or not

Thanks to everybody for all their input on this. Its been a real eye opener.

I've been searching t'internet for some definitve word on this subject and found a very interesting treatise on this subject on the UK Micromagic class association board of all places:

http://magicmicro.org/e107_plugins/f...wtopic.php?438

My interpretation of the theory discussed is that fin, rudder and bows should be as smooth and shiny as possible but the rest of the hull is at least as fast just wet sanded in the direction of the water flow. The amount of the bows which should be shiny smooth reduces as the boat speed increases and also as the surface conditions deteriorate. So, if you sail in light winds on a glassy smooth pond you probably want to polish the first 25-50% (never more) of the hull and sand the back section. As wind speed and chop increase that percentage decreases pretty quickly.

In practice, that seems to support the "Don't polish, sand" camp.

Cheers,
Andy

PS It also states that you should NEVER sand a gelcoat!
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Old 03-08-2011, 10:05 AM
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ron ward
 
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hew,
" the hull grabs a molecule of water", or in effect, just the opposite..." a molecule of water grabs the hull".....is exactly what happens when the hull is super smooth as in waxed. because of the capilary action of water the molecules attatch themselves more completely to the hull and don't want to let go as the hull passes. a slightly rough surface doesn't allow the capilary action to work as well, so small turbulences get a boundry layer of molecules roling around, none of them actually hanging on to the hull, so you could say that the hull is "rolling along" on a bed of water ball bearings and air, more or less unattatched to the water.
a rather simplistic example, if you're framiliar with "contact" cement, is that the smoother the surfaces to be glued are, the better the contact holds because the smooth surface allows more complete attatchment of the glue molecules. a rougher surface leaves voids in their attatchment, so the bond is a bit weaker.
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