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Author Topic: Planking with superglue over a painted hull?  (Read 1796 times)

Edward Pinniger

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Planking with superglue over a painted hull?
« on: September 07, 2009, 07:30:37 PM »

I have a model boat hull which is constructed from thin plywood sheet over heavier ply frames + keel. The outer surface of the ply skin appears to have been treated with something to increase its watertightness and strength, it has then been painted white (looks like Humbrol enamel) over the top of this.

I'd like to plank the outside of the hull with thin strip wood, both to represent the hull planking of the prototype it's based on (since the scale is around 1/18, this should be clearly visible) and, most importantly, to give the hull more structural strength - I'm not confident the thin ply (about 2mm) will stand up to accidental collisions with submerged branches or similar!

Ideally, aliphatic (waterproof) wood glue would be the best adhesive for this, but I don't really want to attempt sanding the whole hull down to bare wood, not only would this be very hard work but I don't want to risk damaging the thin ply skin in the process.

Would it be practical to glue the planking strips on with superglue (cyanoacrylate) after first sanding down the painted surface? Or would the bond produced not be durable or waterproof enough for a working model? The strip wood I plan to use for planking is quite thin (about 1.5mm) and flexible, and it will be varnished and painted once finished.
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DickyD

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Re: Planking with superglue over a painted hull?
« Reply #1 on: September 07, 2009, 08:20:36 PM »

Not a good idea as the bond with the paint will be a lot stronger than the bond between the paint and the wood.

You planking could pull the paint off the wood.
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Colin Bishop

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Re: Planking with superglue over a painted hull?
« Reply #2 on: September 07, 2009, 08:29:06 PM »

Richard is right, could be trouble! Might be worth treating a small area with paint stripper to see if it is wood underneath and not somethiong else such as polyester resin! Once you know what you are dealing with you can look at possible options.

Colin
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Shipmate60

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Re: Planking with superglue over a painted hull?
« Reply #3 on: September 07, 2009, 09:28:18 PM »

Edward,
Please don't just glue the planks on.
As Dicky and Colin have already said you don't know what the base condition is.
There is only one real way to do this and, yes, that is to rub it all down.

Bob
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Edward Pinniger

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Re: Planking with superglue over a painted hull?
« Reply #4 on: September 08, 2009, 03:09:31 PM »

Thanks for the advice. I thought it wouldn't be as simple as just gluing the planks on (and don't worry, I wouldn't have attempted this until I was more or less certain that it would work... it's some time before the model will get to this stage anyway, I'm still working on the radio/motor installation and ballast)

The model is definitely skinned with wood (ply, about 1.5mm thick), its interior surface is completely unpainted. As I mentioned, though, it appears to have some sort of coating on the outside surface (polyester resin?), which is a pale greyish-white colour, under the paint.

I should have made this clearer in my original post - I wasn't intending to glue the planks straight onto the painted surface, I planned to sand as the paint down as much as possible to the treated surface underneath, then glue the planks to this. Assuming the wood is treated with polyester resin, will superglue form a strong bond with this?

I was also considering painting the interior surfaces of the wood with sanding sealer or possibly Cascamite wood glue to add strength and prevent water damage. Would this be helpful, or would it be counter-productive in making the (currently quite flexible) thin ply skin stiffer and more brittle?)
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nemesis

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Re: Planking with superglue over a painted hull?
« Reply #5 on: September 21, 2009, 09:57:45 PM »

Hi, depending on what is underneath, if it is wood then I would use cascamite, it gives you "Time"
to do the job & it is an industry standard material,
                                                Nemesis
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Shipmate60

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Re: Planking with superglue over a painted hull?
« Reply #6 on: September 21, 2009, 10:06:43 PM »

There are at least 2 problems with using superglue.
Once set it is rigid so any flexing of the hull (even putting her on her stand) can cause the hull to flex slightly.
The other problem is if the paint coat is damaged and water gets under the planks it will release the superglue from the basecoat.
My own preference is as has alraedy been said cascamite or PVA waterproof glue.
But they are far longer setting than superglue.

Bob
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