Topsides/Hull Sanding

[cindersailor]

My recently purchased Cinder 22 has an apallingly bad paint job, although the hull underneath is very sound which is why I bought her. Not wanting to loose any sailing time this year I launched her without bothering to do anything about it. Although it is only cosmetic, I would like a nice sleek and shiney look next season, if that is possible for a 37 year old cinder 22! I am therefore starting to think about what needs to be done once she comes out of the water in October.

Questions:
1. Rubbing down all the runs and brushmarks by hand is too much to contemplate, an orbital or belt sander would seem the answer. I have the former, but would buy the latter if advised that it would do a better, or perhaps more importantly, easier job. Any thoughts/experience?
2. Paint? Two-pot polyurethane seems the business, but tricky to apply. How far behind are the single pot varieties - Toplac, Brightsides etc. in terms of finish and durability?

Any advice on putting a bodged GRP paint job right would be most welcome!



<hr width=100% size=1>

 

[Two_Hapence]

Hi,

I've just finished rubing down and repainting my boat. (Ran over too many dingys racing in the main channel in Chi Harbour

You need a meaty orbital sander and a lot of 80 grit backing pads. I tried using a small sander and finished up getting a Bosch (PSE400 I think) 400 watt variable speed job. I was taking off two pack and it took a while.

After rubbing off all the old paint I then prepared the surface with 240 grit and then filled and faired all the imperfections. What I had neglected to do was to measure the boot top all the way round and invariably you are going to dig into this as you paint the boat.

Then came the repainting with two pack primer. You need a warmish dry windfree couple of days so you can wash the boat, dry it and then you need to get at least two coats of primer on. If you can manage to repaint within the overcoating time you don't need to sand inbetween coats. You'll need to have someone rolling on the paint and someone else tipping off. Thin your undercoats by 10%.

If it is cold the paint takes a long time to cure, if it is windy you'll get lots of grit blown onto your boat and if it is warm every flying insect within 20 miles will come and wade in your shiny new paint job! If it is damp then the paint will lose all the shine.

Mix a coat of 50% undercoat and 50% topcoat and then thin it by 20%. Paint it and then leave it to cure. Rub it down very gently to get a smooth flat finish without grinding off all the other coats you put on. Wash the hull carefully. Try and put up some shading and then put on the topcoat thinned with 25% thinners - one or two coats depending on how much of the basecoats you sanded off.

Don't expect a perfect finish. Every imperfection in the hull, each ripple and ding will show if you look too closely. Stand back a bit (say 20 ft) and it will look fine. I used International paint though in future I'd probably go for Awlgrip as it seems to flow better and gives a neater finish.

Tips. Make sure you don't use textured or pile rollers. The radiator ones with closed foam rollers are perfect - but have plenty because the two-pack destrooys the foam.
Don't try and put on too much paint at a time. It will only run and then you have to sand it all down and start again.
Don't try and "repair" any bits you have done badly. The paint goes off very quickly and you'll make a mess of the area.
Don't wear woolen clothing or you'll get wool all over the paint job.
Make sure that whoever is tipping off the paint is working 30 seconds behind you and adjust the speed that you put on the paint so that they can keep up.
Wear goggles, gloves and a respirator designed to keep out the fumes.
Try and paint in the shade!

Do NOT paint when there is going to be a dew!

All in all I got a decent job as long as you don't look too closely. Even 5 ft away she looks fine. But the best piece of advice I received was "Do you want to spend your time inside your boat looking out or outside your boat looking in?"

Have fun.

Regards


Ian

<hr width=100% size=1>

 

[snowleopard]

a belt sander will cut through runs, paint, gelcoat and a fair bit of the laminate!!
a decent orbital sander will work ok but the little drill attachment jobs are pretty useless.

Hand sanding with progressive grades of wet & dry, used wet, is still the best way.

2- pack polyurethane is much better than one pack and is not that tricky as long as you follow the rules.

protect it from wind & dust and above all moisture - dew the following evening will ruin it. don't apply by spray, the 50% that doesn't stick to the hull will poison you!
don't apply polyurethane on top of conventional paint.

Apply with a roller and smooth out bubbles with a foam plastic brush as you go along. maintain a 'wet edge' by starting at the stem or transom edge then painting the full depth of the topsides all the way round.

<hr width=100% size=1>

 

[bob26]

If you are going to use 2-pack you will have to take off all the existing paint first unless you know it is compatible.

<hr width=100% size=1>

 

[oldsaltoz]

G,day CinderSailor,

If you want to avoid a lot of hard work, spend us much as you can afford on a good quality orbital sander, look for one with at least a 3 mm orbit (not a finishing sander); see your local panel beaters if you need more advice on sanding equipment. If you select one that uses grit off a roll, it will cost a lot less than the fancy stick on pad jobs also.

80 grit is normal, but if she has a lot of thick paint, start with a 60 grit and stop when you see base colour, then use an 80, finish with a 240 and fill and imperfections, any minor cracking should be ground out and filled, microballoons or 'Q' cells do a good job and are very easy to sand; when sanding repairs, always start with an aggressive grit and work to finer grits as you go, this will avoid a lot of work, and, more impotently, avoid that slight blistered look most DIY jobs end up with.

If the old paint is not 2 pack you will have to remove every last trace, or you risk the expensive two pack failing due to poor keying. Non slip areas can be cleaned with paint removers, a messy job, but you will only be doing it once, well on this boat at least.

If there is any way you can spray your paint on do it, the finish is far better and one full coat takes 15 minutes, not 4 hours; a simple plastic sheet tent with a fan at one end and an opening at the other end will the job.

If you must apply by roller and brush (you may regret this later) use the correct high density foam roller that will not dissolve and the correct foam tip off brush; and a bunch of friends, so you can apply the two coats of primer at once, this will save a lot of sanding, just have the second team follow you up as soon as the paint is hard enough, about 10 minutes on a warm day. This will show up more imperfections, you can fill with balloons/cells and sand and get away without adding more primer, provided the area is very small.

Keep an eye on the humidity, two pack paint does not like humidity much above 72%, and don't paint after 2;30 pm, or you risk dew point damage.

And finally, use only thinners designed for the paint and what ever you don't add more than the manufacturer recommends.

If you can find a supplier, try for some International Interspray 900, it has 52% solids, long chain polymers and dries to an excellent gloss as hard as any, very durable, I use on most jobs, and, no I have no connection to them, I just like the good stuff, having tried most others.

Well, good luck with your project and I hope this and other advice provided will save you some hard hours and get you the very best results. . . . . . .



<hr width=100% size=1> Old Salt Oz /forums/images/icons/cool.gif Growing old is unavoidable. However, growing up is still optional.

 

[cindersailor]

Thanks guys for a lot of excellent advice. I now need to decide whether to pay the extra to keep the boat in a shed at the boatyard this winter or take pot luck with the weather; what are the chances of a couple of warm, dry and windless days over an autumn weekend in Scotland? The shed it is then.

<hr width=100% size=1>

 

[Blue_Blazes]

"couple of warm, dry windless days" Isn't that known as a heat-wave in Scotland? )

Seriously though, go with Oldsaltoz's advice and you won't go far wrong. Please don't even think about a belt sander. They can do untold damage in the hands of a professional, let alone a beginner.

Bill.

<hr width=100% size=1>One of these days I'll have a boat that WORKS