Boat Polishing

[insideout]

I was polishing the car the other day, and one of my mates kids asked what i was doing, to which i replied"polishing the car"....."why?" was the next question, to which i gave a long winded answer about "so the sun does not fade the colour" and"to keep it shiny and looking like new"and "to make it go faster- less wind resistance, use less fuel "ect , ect , ect..

Then i noticed that he was heading around the back with the polish in hand , and i asked what he was doing."polishing the boat " he said............ which leads me to my question...
does polishing a hull of a glass boat have little , if any influence on the drag/ fuel burn, and does a painted underbelly of a plate boat slip through the water better than an unpainted one??
Is the difference in fuel noticeable after evey full tank used?

Or do i have much to much spare time on my hands of late to contemplate such things.......;) ;D

[Noelm]

In theory of course it will make a difference, but in practice I guess it will be almost unmeasureable, but in (say) a moored boat with a tonne of growth and Barnacles on it, then you will see a huge difference, but between shiny gloss, and not quite as glossy, not a lot, but it will be SOME!

[Timfishin4fun]

Hi guys, I polish mine as it makes it easier to clean next time and I believe it does protect the gel coating to keep it looking new. I'm not worried about fuel savings but if ya never cleaned it I'm sure you would feel the difference sooner or later.

Tim.

[kingtin]

Can't get mine dirty enough for it to need polishing :'(

kev

3 dollars a week will supply water for an entire village in Tanzania', says Oxfam. So how come Brizzy council charge me 30 dollars a month for my 4 bedroom? The fleecing buggers

[artesian]

Sharks have rough skin (denticles?) to make them more slippery in the water, if memory serves.

[kingtin]

Sharks have rough skin (denticles?) to make them more slippery in the water, if memory serves.

The roughness is only apparent if you rub from tail to head..........rub from head to tail and they're smooth.

kev

[PWCDad]

Many moons ago I had a National Speed Record for Scale Model Boats, a mate and I ran between 50mph and 85mph with monohull and hydroplanes.

All our boats were rubbed with 3000grit sandpaper on the wetted surfaces of the gelcoat to break water tension and therefore reduce some friction.

The faster we went the more the gains from the dull surface verses out of the mould gelcoat ...

I also did a dew years at TAFE learning the art of fibreglass molding and lay-up .... the skiff hulls (sailing) were all rubbed dull on the bottom surfaces ... which is where we got the idea from to rub the power boats. This was circa 1978.

A bigger influence on hull speed for a given power was any "hook" in the hull i.e. place a straight edge along the hull bottom and any gaps of undulations were filled for a 5mph gain at around 70mph. The hook in the hull, in effect, is changing the water direction as it flows over the hull so creates higher hull friction against the hull surface and slows the hull speed. It affects hydropanes far less than monos because there is much less hull in the water.

As a further example the rideplate on my 160hp personal craft has been "trued" (filled and sanded flat) for a gain from 58.5mph to 59.67mph. It had a about a 1.5mm dip in the centre of the aluminium rideplate. A pic of it below ...

Another area of reasonable gains was making any object that dragged in the water (turn fins, water pick-ups, rudders etc) shaped like an aircraft wing in section. Same as the leg of an outboard ... sharp surface presented to the water and a sharp surface as the water leaves the object.

So I reckon polish away on any bit of hull above the water line .... and run the hull over a sand bank or two for a dulled off bottom (wink).

I believe there are some good gains from lanotec on the hull bottom ... I believe the Stradbroke Cat (Taxi ?) was using 50litres less per round trip to Straddie from Cleveland ... had Lanotec sprayed over hull bottom from memory ....

Regards
PWCDad

[PADDLES]

top bit of info there pwc, i remember a phase of surfboard designs in the late 90's that were made with a deliberately matt finish to allow a boundary layer of water to "adhere" to the board and theoretically make them more slippery.

[roydsy]

Can anyone tell me the best way to remove scratches on the hull of a fibreglass boat. We hit a stump at Borumba at low speed and left a nice love scratch on the bow of the full boar.

Do I sand it and polich polish? Also this boat is blue so will sanding remove paint.

[insideout]

thanks PWCDad, i would have never have known about rough hull being more slippery through the water than a smooth one!! The lanotec you speak of, is that the anti corrosive spray- or some other product from the same name company?

[PWCDad]

Insideout,

Its the anti-corrosive spray in Heavy Duty form ... there is a light and a heavy version.

Also ... I did some tests on some impellers in my jet pumps ... they run around 7000rpm and propel a 90mm stream of water at 180kph ... I heated the impellers to 180 deg C and painted the surfaces with lanotec heavy (dont breath the resultant fumes). It stayed on for quite some time as a surface appearance (5 months or so) and probably much longer as micro coating IMHO. The impellers are stainless so I only did it as an experiment to see if it would stay on under extreme conditions.

I got damn barnicles on the hull of my Seajay 5.0 CentreConsole, I use it so much !!!! I used a Gerni and a scotchbrite to clean the hull .... so now I'm thinking use a lanotec coating on the wetted area to keep the barnicles off !!!

The boat is trailered to home everytime ... but lately I've lived on the Broadwater .... hehehehehehe ! A week in the water on the school hols got me the barnicle collection !!!

Roydsy,

If the blue area is paint be careful ...dont sand just use a buff compound as best as possible, and go easy peasy ... if the blue is a gelcoat, as against paint, read on ...

If you dont want to get it pro repaired ....

Use a fine sandpaper (2000 grit) and water/detergent mix as a lubricant to even the surface out as best you can .... into the scratch and just beside it about an inch or so .... then work with a buffing compound if possible ..... then a good polish or speed glaze to remove buffing compound trail ... and it will disappear as best as possible without a full repair.

You are not trying to remove the scratch just blend it in somewhat by making it glossy again the same as the surrounding area ....

The first cut is the deepest huh !!! (wink) The second wont seem so bad !!!

Regards
PWCDad

[roydsy]

Thanks PWCDad I think I might leave it to the pros and get it repair properly, as I have no idea what the blue is gelcoat or paint.

cheers
Roydsy

[RAEDAR40]

(New member - be gentle with me) I have been trawling thru the boat chat threads and just saw this article. My 385 Explorer is three years old and looks brand new (dealer in Coffs wants first refusal if I sell) and I often get asked when launching have I just taken delivery of my new boat.
After every trip, on the way home, the boat and motor gets a quick wash at a car wash when I come in off the salt: one spray and the salt falls straight off.
Then when it is ready to be put away for a spell, it is washed more thoroughly and then polished as is the motor. This method has kept my hull pristine and new looking.
Also, just a quick reference to another thread about running the carby dry. I was told when I bought the boat, to rinse the motor thoroughly and let it run dry. Has this issue been resolved yet ? Is that the correct thing to do ? Or should I let it run for X minutes then stop the motor, leaving fuel in the carb ?

[Blackened]

G'day

Roydsy, chanes are the blue is gelcoat, and it will be a bitch of a job colour matching. Best off taking it to a pro. Go and see john keen at ship shape ships, he's in horizon shores.

RaeDar40, no, the methods of running an engine dry is yet to be resolved

Dave

[jigsnreels]

Great info thre

pwcdad, did you notice a difference in speeds on dead flat oily looking water to water with a very slight ripple?

jigs