Re-painting Aluminum AB RIB

[tookish1]

Soon after getting our 12' AB RIB, paint started flaking off. I'd like to strip the remaining paint off and re-paint. Inside will need to have some anti-skid added.
What is the best approach to prepare and re-paint my dinghy?
Thanks!

[Hoofsmit]

I am sure there are more knowledgeable people than me here, I do know aluminium needs an etching coat to enable topcoat adhesion, and Ali oxidises very quickly after prepping the surface.
Search the www. On aluminium coatings and preparation.
I know the etching coats can be volatile , they also may damage the tubing ? Or it adhesion to the hull
Hopefully some one will chip in with more knowledge than I !


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[witzgall]

The truth is that an aluminum hull, on a dingy, is not going to hold paint well, for long. Once you get a nick in the paint coating, it will, over time, fail at that point. I don't know any way to avoid this.

This is why we made sure our AB came unpainted. I know that does not help you, but perhaps the answer is not how to paint your hull, but how to effectively remove the remaining paint?

Chris

[tookish1]

Originally Posted by witzgall

The truth is that an aluminum hull, on a dingy, is not going to hold paint well, for long. Once you get a nick in the paint coating, it will, over time, fail at that point. I don't know any way to avoid this.

This is why we made sure our AB came unpainted. I know that does not help you, but perhaps the answer is not how to paint your hull, but how to effectively remove the remaining paint?

Chris

Chris:
That's a very solid point. How would you get the rest of the paint off? A chemical stripper if we get a great masking job on the hypalon?

[a64pilot]

Go to any good automotive parts store and buy a gallon of "aircraft" paint stripper. It will remove almost any paint, but I don't know what it may do to the tubes, so keep it off of that, stuff is thick almost jelly like, I use a pressure washer to remove it and the paint once it has bubbled the paint up.
Be best to Alodine the aluminum as a paint prep, but not essential, aircraft are almost always painted with a two part, single stage polyurethane paint, pretty common stuff.
There is a very common "walkway compound" type of paint that is very common and you just roll it on with a roller, but get it shaken by the paint shaker before application, it's just sand in the paint but the shaker mixes it very well and uniform.


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[a64pilot]

As far as paint not staying on aluminum, it seems to stay on aircraft floats very well. If it will stay on an aluminum aircraft float, not sure why it wouldn't a dinghy?


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[Bulawayo]

Our 100% aluminium dinghy (which has aluminium tubes) is totally unpainted - we just have marine carpet inside for comfort and to reduce slippage. The dinghy looks just fine. The dinghies are produced in Australia and come, as standard, unpainted. Why worry about some paint flaking off? Just leave it - it may reduce the chances of someone else wanting to acquire it, sort of customises it. We stripped the paint of our outboard engines after removing the decals and painted them yellow - not very attractive to the 'collectors' as they are very distinctive.

[colemj]

Originally Posted by Bulawayo

We stripped the paint of our outboard engines after removing the decals and painted them yellow - not very attractive to the 'collectors' as they are very distinctive.

In case someone wants to follow your advice - you meant you stripped the paint off the OB plastic cowling, and not the aluminum body and drive leg, correct?

It would be a very bad idea to strip and attempt to repaint the aluminum body and drive leg. Those are typically specially treated during manufacturing when bare, and coated with specific etchers, primers and paint - usually paint that is hardened in ovens. This paint system is a large part of the corrosion resistance of the engine.

But even if you did both, why strip the underlying paint rather than just paint over it?

Mark

[Cheechako]

Originally Posted by witzgall

The truth is that an aluminum hull, on a dingy, is not going to hold paint well, for long. Once you get a nick in the paint coating, it will, over time, fail at that point. I don't know any way to avoid this.

This is why we made sure our AB came unpainted. I know that does not help you, but perhaps the answer is not how to paint your hull, but how to effectively remove the remaining paint?

Chris

Yep, it seems to be a roll of the dice as far as paint staying on aluminum. Regardless of how it's done. Many of us have had paint issues on masts... that really aren't immersed. Mine was "properly" done and had issues within 2 years on the bottom 6 feet above deck.
Friends of mine had their 48 alum cutter painted 3 times in... about 8 years. By one of the best yards in Fl to Trinidad to Cartegena... didn't matter who did it... it didn't stay long. They probably spent may 40K on painting in that time... maybe more.
There's a reason the French don't paint.
It's probably not that aluminum cant be painted and last well in a perfect world... but unfortunately .... the world aint perfect.

[colemj]

Specifically to the topic of aluminum AB's - I have never seen one of these where the paint wasn't flaking off after the first year of use. And that represents zero boats out probably 50 or so that I have seen.

Personally, if it was mine, I would just live with it and let it flake. These aren't status symbols - they are utilitarian tools. It would take a lot of persuasion to get me to go to the trouble of stripping the remaining paint off. I would never repaint it.

Mark

[s/v Jedi]

Put Treadmaster on the floor and ignore the rest

[colemj]

I think they come with treadmaster or similar already.

So your advice boils down to "ignore it"!

Mark

[Bulawayo]

Originally Posted by colemj

In case someone wants to follow your advice - you meant you stripped the paint off the OB plastic cowling, and not the aluminum body and drive leg, correct?

It would be a very bad idea to strip and attempt to repaint the aluminum body and drive leg. Those are typically specially treated during manufacturing when bare, and coated with specific etchers, primers and paint - usually paint that is hardened in ovens. This paint system is a large part of the corrosion resistance of the engine.

But even if you did both, why strip the underlying paint rather than just paint over it?

Mark

Hi Colemj,
Not exactly - we spoke to the Yamaha dealer who sold us the motors - he wanted to do the job and earn himself a few dollars. We have done this before. Yes, we stripped both the plastic covers and the ali body/leg. We took the motors to a local auto paint shop and they stripped the bodies and leg to the bare ali. We then used sprayed specialist primer before painting with the same specialist top coats. Our Yamaha Malta engines were painted around 12 years ago and we have had to do some minor touch up since. Our two Yamaha Enduro's (15 & 25HP, both 2014) we did immediately after running them in. Yes, I accept that the warranties are binned, but when the dealer is already thousands of miles away I am not particularly fussed. More importantly, the thieves have no idea what the motors are - they could be anything to the majority of people. Importantly, they are a bugger to reinstate so the theft risk is dramatically reduced. Thieving is second nature in some parts of the world (lets not discuss why) and so anything that reduces the possibility has to be considered. Our engines are very distinctive as are our dinghies. They really stand out, something that we hope shall be obvious to any potential crook. Naturally, our engines are also locked to the dinghy, and the dinghies are locked when on board. We have seen people return to their dinghies only to find the whole transom has been cut off with a knife and the transom and outboard engine gone. In Mozambique a few years ago a South African boat had a pirogue sail under his transom - a slash with a panga and the whole dinghy was cut free from the davits, fell onto the pirogues decks and they were gone into the dusk. Several of us tracked them on radar to where the pirogue went ashore. When the owners went to the police the thieves claimed salvage as they had found the dinghy!

Before anyone gets the wrong idea, the Indian Ocean is not like this everywhere, by anymeans, but you need to be alert and aware to thieves everywhere.
Painting your outboard in a violent colours helps a lot, in our opinion.

[minaret]

Prep to 80 grit profile per ASTM; acid etch while bright, maximum 45 minutes after abrasion, surface must be at least 5 degrees above current dewpoint (etch with Alumprep 33). Then alodine, then a high quality primer such as 545. Prep, fair welds, and apply topcoat of choice. No solvent wipe before etching, only very clean high pressure air.

Too much work for a dinghy...

[colemj]

Originally Posted by Bulawayo

We have done this before. Yes, we stripped both the plastic covers and the ali body/leg. We took the motors to a local auto paint shop and they stripped the bodies and leg to the bare ali. We then used sprayed specialist primer before painting with the same specialist top coats.

Why not just paint over the original paint?

BTW, I doubt you have concealed their identity from thieves. I can pretty much tell most common makes and models, including HP, just from shape and other features regardless if they are painted paisley.

I bet a dollar that every thief in the world recognizes Yamaha Enduro's. Even blind thieves.

I do agree that making them difficult to pass about without notice is helpful in thwarting thievery - as long as there isn't a big market for used parts in the area, or a distribution line to farther-flung places.

Mark