Sanding down the hull?

[whiteoaks7]

The easiest way to remove all the years of accumulated whatever from my hull is going to be 1500 wet and dry paper applied with water and soap, followed by a polish. I've used this technique in the cockpit and it works a treat. HOWEVER, I'm a bit more nervous about attacking the hull gelcoat in this way so I thought I'd gauge everyone's opinion? What do we think, team?

 

[stevebrassett]

It's not my boat, so go for it. Let us know how you got on, won't you. Then if it all goes wrong we know not to try it.

 

[FWB]

If it's a GRP hull, try Farécla G3 followed by G10. Then polish with Autoglym. The soap and wet and dry technique is good for removing scratches.

 

[tcm]

Bad idea imho. Use GRP restorer from wessex chemicals to eliminate oxidation and restore an "as new" gelcoat appearance, then apply polish

 

[Avocet]

We need to know a bit more. What exactly are you trying to remove? Just grime, or fine scratches?

If it's just dirty, 1500 sandpaper is maybe a bit aggressive. Most gelcoats are only between about 0.3mm and 0.5mm thick and they need to be there to keep the water out of the fibres so I'd be reluctant to use the sandpaper all over. I'd maybe use it on the stubborn bits followed by a good buffing with the Farecla G3 and G10 AND a proper industrial buffing machine - not a DIY car polisher. That said, you'd be amazed at what the buffing compound will remove by itself - I'd be surprised if you need the sandpaper.

 

[Strathglass]

[ QUOTE ]
If it's a GRP hull, try Farécla G3 followed by G10. Then polish with Autoglym. The soap and wet and dry technique is good for removing scratches.

[/ QUOTE ]

That is quite an interesting answer. Yesterday I started on my hull using G3.
In two hours I managed to do about four square feet. Even then some parts are not back to the original colour.

The 33 ft hull was moulded in 1977 by SOS It has never been in the water. (will be launched next spring) The white part of the topside is fine but the 2 feet wide red/orange strip is a dark red and is taking some effort to regain the colour.

I have a good profesional polisher but it is taking a long time to get back to the original colour. The gelcoat is quite thick as is the GRP in the hull.

I was going to post exactly the same question as the original poster today.

I was also thinking about 1500 wet and dry then G3, G10 and finally Autoglym.

I have sucessfully used this technique before when refurbishing well used hire boats at the end of their working life when they were being put up for sale.

It's a different matter when considering taking wet and dry to the gel coat on one's own craft however.

I look forward to all answers with interest.

Iain

 

[FWB]

My boat has a black hull which I unfortunately neglected this year. It now looks like new,if not better!, using this technique. You have to persevere and keep the hull wet when using the Farécla, sorry if this is teaching you to suck eggs etc.

 

[Strathglass]

Thanks,

Yes, aware of that I have a hose set at a mist spray beside me. It is years and years of oxygenation I have to get rid of and one or two very minor scratches.

I posted to see if anyone could sugest a quicker method.
It will certainly get there using G3 but will take a long time.

Irrespective of how experienced one thinks one is. Nobody is too old to learn.

Thanks again

Iain

 

[absit_omen]

I found that using G3 with a slow rotating, proper compounding tool did a great job on my badly oxidised blue hull some years ago. The key is to keep the hull very wet to avoid burning. You are not applying the Farecla by hand are you?

 

[Strathglass]

No,

I have a proper 1.2Kw slow moving compounding tool. I can vary the speed down to below 600 rpm.

I think it's just the amount I am having to remove. Gell coat is thicker than 1mm.

Iain

 

[billmacfarlane]

Here's an extract from an article on how to treat a badly faded hull from a gel coat supplier:
"In exceptional cases after many years of use where fading might have occurred, it may be necessary to have the gelcoat restored. According to our supplier of gelcoat, Ashland, the treatment consists of three principal steps;
1. Provide a new gelcoat surface by sanding with a dry paper of 1200-1500 grit.
2. Apply a cutting compound to bring back the deep lustre.
3. Seal the gelcoat with hard wax as protection against UV-rays and salt water.
We highly recommend such a treatment to be performed by a professional restorer.
Recommended products for treatment of polyester (gelcoat) surfaces;
§ Hard wax (3M Ultra Performance Paste Wax)
§ “Polish” including very fine abrasive (3M Perfect it III “blue or black”)
§ 1200-1500 Sandpaper (any dry paper)"

 

[pcatterall]

I thought that anything over 1000 grit was very fine and wouldnt remove too much gell coat, mine is at least 1mm.
However this year the hull will get painted.

 

[whiteoaks7]

Interesting and useful responses - thanks. Seems that polishing with paste is good but slow while using 1500 grit paper is quick but we have to worry about going through the gelcoat. In my youth I was employed by a car sprayer and we never (rpt: never) used paper dry because it clogged and tended to cut too deep so I'm going to use wet and dry 1500 with lots of soapy water (lubrication and cleaning of the grit) followed by a polish and wax.

 

[Strathglass]

Sorry for jumping on the back of your posting but we are both after the same thing.

I have also decided to use 1500 wet to start with. Don't have any choice as there is an almost constant light drizzle just now.

I was prompted to do it as the cover of my B&Q gazebo decided it would rip to shreads during last weeks high winds.
Thus I have good access to the topsides.
Still it has lasted all summer. A new tarpaulin has just arrived from ebay. So the boat will be protected for the winter.

I have attached a couple of photos.
The first one is at the bows. This was after about four hours with G10. It is quite clean, some of the apparent marks are reflections or residue from the G10 which I have not removed. It is coming up reasonably well but not perfect.
I will be sanding this area again until I get it to an even colour. Fortunately the gell coat is very thick by present day standards. Even so I have still not covered the first square meter.

In the second photo you will see the streaking and light/dark areas which will take some work to sort out.

I could respray it. But I would rather not. I have all the material, necessary equipment and experience to do it.

I was planning to change it to Oxford blue and even have the paint, thinners, accelerator and glaze coat. But trying to avoid it if at all possible. I want the boat finished and in the water by the spring. I still have to epoxy the hull before antifouling it.

Iain

 

[DaveS]

Has anyone any experience of using Polyglow on well faded topsides?