Romoving rust and sealing around mushroom vents

[Philippe]

Managed to get my boat booked in for blacking the week after next. While it's inside for a week I wanted to take the opportunity of dealing with some rust around the mushroom vents on the roof and sealing around them properly as they do let in water when it rains.

 

Being a bit hamfisted and ignorant on the DIY front, I wanted some advise on what to do. Apologies for all the questions but there is lots that I don't know!

 

Firstly I plan to remove the vents then strip down the roof metal, removing the rust. What is the best way to do this? I have an electric drill of reasonable quality. What attachment would be right for this?

 

Next I need to apply some metal primer. What is the most suitable type for a narrowboat roof?

 

Then I will need to paint the areas. What paint do you use for a steel narrowboat? How many coats? Do I need undercoat?

 

The roof is currently white(ish). Would it be better to repaint the whole roof while I'm at it? If so, is it okay just to paint over the bits I haven't touched or will then need preparing beforehand?

 

There are two strips down either side of the roof that are non-slip. It looks like this has been achieved by adding some grit like substance to the paint. If I did redo the entire roof, would painting over these significantly reduce the non-slip properties?

[RobinJ]

Managed to get my boat booked in for blacking the week after next. While it's inside for a week I wanted to take the opportunity of dealing with some rust around the mushroom vents on the roof and sealing around them properly as they do let in water when it rains.

 

Being a bit hamfisted and ignorant on the DIY front, I wanted some advise on what to do. Apologies for all the questions but there is lots that I don't know!

 

Firstly I plan to remove the vents then strip down the roof metal, removing the rust. What is the best way to do this? I have an electric drill of reasonable quality. What attachment would be right for this?

 

Next I need to apply some metal primer. What is the most suitable type for a narrowboat roof?

 

Then I will need to paint the areas. What paint do you use for a steel narrowboat? How many coats? Do I need undercoat?

 

The roof is currently white(ish). Would it be better to repaint the whole roof while I'm at it? If so, is it okay just to paint over the bits I haven't touched or will then need preparing beforehand?

 

There are two strips down either side of the roof that are non-slip. It looks like this has been achieved by adding some grit like substance to the paint. If I did redo the entire roof, would painting over these significantly reduce the non-slip properties?

The mushrooms should be screwed or bolted on. if you have to drill them off, make sure you have suitable replacements (check this beforehand by finding a screw/bolt you can remove).

There are plenty of brush, disc and paint cleaning attachments for drills, I would use some sort of disc and a wire brush for the nooks and crannies!

Apply some sort of rust remover/cleaner/converter and clean up afterwards. Then a good metal primer, followed by undercoat (thats 4 warm days!)

For the top coat there are a number of possibilities; Repaint the whole roof (only sensible if it needs it); Simply paint round the vents (this can be doen as a square or circle of a different colour); If you have the original paint, use that and blend into the original (more time consuming!)

[Chris Pink]

You won't need a drill, the rust can be easily removed by hand, sandpaper and a handheld wire brush.

 

You'll want a good sealant ( the most important bit) sikaflex marineflex or a GP mastic. Avoid silicone.

 

You may be dealing with lining inside depending on whether the screws go through to nuts or whether the roof is tapped with a thread.

 

Sealing the vents to repainting the roof? Looks like this job is growing.

[Philippe]

Thanks for the tips!

 

Warm days shouldn't be too much of an issue. I know the forecast is for very cold weather but the boat will be inside so the conditions should be okay.

 

Sealing the vents to repainting the roof? Looks like this job is growing.

 

Well I was hoping it wouldn't really as the whole roof repaint is almost certainly a step too far at the moment.

 

simply paint round the vents (this can be doen as a square or circle of a different colour);

 

This sounds like a great idea to make the whole thing simpler!

Edited January 11, 2013 by Philippe

[Timleech]

You won't need a drill, the rust can be easily removed by hand, sandpaper and a handheld wire brush.

 

You'll want a good sealant ( the most important bit) sikaflex marineflex or a GP mastic. Avoid silicone.

 

You may be dealing with lining inside depending on whether the screws go through to nuts or whether the roof is tapped with a thread.

 

Sealing the vents to repainting the roof? Looks like this job is growing.

 

That does rather depend on the level of rusting.

If (light) scale is forming, I'd go for the Perago 'blaster', there's an identical item under another name which escapes me at the moment. Used in an electric drill at moderate speed, avoid striking the edges of the hole the wrong way otherwise you're likely to loose teeth from the tool.

 

Agreed about the sealant.

 

Tim

[alan_fincher]

Don't assume just because a boat is undercover it will be easy to put a lot of paint on at this time of year, particularly if temperatures go as low as predicted.

 

It can be very difficult sometimes to avoid at least small amounts of moisture on cold steel, and in the worst cases paint drying times can go out from the very short times they would be in hot weather to very long times indeed. Some paint manufacturers provided data that show how much extra drying time to allow, but few would suggest you try at all if temperatures are near to freezing, I think.

 

I wouldn't try any large scale repainting now, unless your undercover area is actually heated in some way.

 

Agree with the advice about not using silicone - it will fail again eventually - the only issue being how many years that might take.

[Philippe]

Sounds like the full roof repaint is a no go then, which is a bit of a relief if truth be told.

 

If I do have problems with condensation and drying times, would just the primer be sufficient until the weather gets warmer in the Spring?

 

Or would it be better to just temporarily seal the vents to prevent more water ingress and deal with the rust when the weather improves?

 

Only just noticed my title typo! Oops!

[BEngo]

Sounds like the full roof repaint is a no go then, which is a bit of a relief if truth be told.

 

If I do have problems with condensation and drying times, would just the primer be sufficient until the weather gets warmer in the Spring?

 

Or would it be better to just temporarily seal the vents to prevent more water ingress and deal with the rust when the weather improves?

 

Only just noticed my title typo! Oops!

Temporary fix and a proper job later would be my suggestion.

 

To tempo fix:

Remove vents

 

Attack rust with wire brush or sanding disc in an angle grinder. ( A cheapo DIY Shed angle grinder is a really useful tool for boat maintenance and avoids spoiling your drill getting it to do things it wasn't designed for and isn't very good at.)

 

Fertan/Vactan iaw instructions

 

Refit vents with butyl rubber sealant ( Google e.g seamseal CV, there are others)

 

That will hold the rust at bay and keep it watertight until the weather warms up. The sealant can then be removed with white spirit and second assault on the rust made before a full paint scheme.

 

On your other questions:

 

Any decent metal primer will be OK- it needs to be compatible with the undercoat and gloss paints you are going to put on it. Craftmaster, Rylards, International and others do them. Primer is (generally) porous so no good for holding off more rust as the water passes through it.

 

Two coats of each: Primer, undercoat, topcoat. More undercoats and topcoats if you like. Rub down between coats with some 240 grit Wet n dry.

 

Painting only the damaged areas is OK- feather the edges all round before the rust treatment and primer then after every coat so you don't get a step. You will still probaly be able to see a difference between the new and the old.

 

Painting over the non-slip will reduce its properties, but whether thiswill be a problem depends on how much paint there is now and how much more you put on. To much of a 'how long is this string' question to answer without physically seeing it.

 

 

 

N

[AndrewIC]

If (light) scale is forming, I'd go for the Perago 'blaster', there's an identical item under another name which escapes me at the moment.

 

Tercoo?

[Timleech]

Tercoo?

 

That's the one. Same tool, different colour.

 

Tim

[smileypete]

Best use zinc phosphate primer, applied directly to prepped steel.

 

Sealant isn't so critical on something that small, even acrylic frame sealant should do.

 

(With windows it can be more about HOW you seal them )

 

cheers, Pete.

~smpt~

Edited January 11, 2013 by smileypete

[Philippe]

OK, looking like a temporary fix with a proper job in the Spring is the way forward.

 

Thanks for all the advice!

[Higgs]

Or would it be better to just temporarily seal the vents to prevent more water ingress and deal with the rust when the weather improves?

 

Nothing much is going to make the problem worse until the warm weather apart from the leak into the boat. I would fix the leak and forget the cosmetics until it gets warmer. Clean any really ragged areas from the edge of the mushroom and run a bead of butyl all around, smoothing down with finger. Stay clear of silicon, you'll regret using it as you intend painting at some point.

 

When you do take the mushroom off, clean rusted areas with whatever and possibly a grinder until you have bright steel. This will mean going a short distance into the paint at the edges of the rust. Personally I don't use rust inhibitors. What you need to do though is, having cleaned the area, get the paint on soon after thoroughly cleaning the job and degreasing. Priming on its own will not protect the steel completely. Primer is designed to be porous, a key for the undercoat. So, until you have an undercoat on, your steel will be vulnerable to moisture.

 

When you are satisfied with the paintwork, drop the mushroom onto a bed of butyl. But, leave the replacing of the mushroom for at least a few days after painting. This will give the paint time to cure some. The butyl that is forced out can be cleaned off easily, and best left a day or two to skin over then cleaned off.

Edited January 11, 2013 by Higgs

[jonathanA]

one thing you might want to consider, is replacing the usual brass set screws with stainless steel allen (hex drive) machine screws.

 

I think they are easier to tighten up/undo than brass screws with an ordinary slot drive which often gets damaged if you use the wrong size driver or have to get very physical. also makes them a bit harder for the scallies to nick off your roof !

 

you will need to find a proper engineers supplies/fastenings supplier and they'll be a few pence each, otherwise B&Q or midland swindlers will charge you about £5 for a little plastic bag with 3 in...(actually they won't have them but you get the idea)

[Ray T]

In this month's Waterways World (February) page 75, Tony Redshaw is selling weld on mushroom vents @ £33.00 each.

 

http://vintage-diesels.co.uk/

 

No connection. Makes them more difficult to nick.

[CaptAWOL]

Consider using something like self adhesive window tape to bed the mushroom vents on, the width (about 5mm) is small enough to bend around the base of the vent, I double it up so as to achieve a base about 10mm width, the simple benefit of tape is appreciated next time you remove the vent.