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Author Topic: painting the inside of your hull  (Read 6605 times)

portside II

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painting the inside of your hull
« on: November 08, 2008, 09:50:58 PM »

What do you guys use as to painting the inside of your hull's apart from the obvious ,a brush ! :P .
i have thought about a gell coat thinned down with accetone add the activator and then paint , but what do you think ???
daz
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Shipmate60

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Re: painting the inside of your hull
« Reply #1 on: November 08, 2008, 09:58:05 PM »

I fit everything out, remove all electrics and motor then paint with light colour household emulsion.
These new ones will protect the woodwork and mountings etc, plus it looks tidier when you take the superstructure off.

Bob
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tigertiger

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Re: painting the inside of your hull
« Reply #2 on: November 09, 2008, 03:35:31 AM »

If it is a plastic/FG hull, I have used nothing. Not even on the woodwork (rado tray etc.) no problem.

But I am about to build my first wood hull and am thinking about ordinary paint or epoxy. So I will watch this thread with interest.
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Martin [Admin]

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Re: painting the inside of your hull
« Reply #3 on: November 09, 2008, 06:51:36 AM »

Inside my Springer, I covered the motor, oiler tube, speed controller and deck (from the coaming outwards)and sprayed 2 or 3 coats of satin varnish, (Halfords/Clearcoat car type paint).
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Marks Model Bits

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Re: painting the inside of your hull
« Reply #4 on: November 09, 2008, 08:20:27 AM »

Hi Daz, Don,t use gel coat it will stay tacky for gel coat to set hard it needs an anaerobic enviroment to cure properly.  If you are thinking of thinning down gel coat with acetone, why not use ordinary resin and add a colour pigment to it, there are loads of different colours available from GRP suppliers.

Mark.
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Seaspray

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Re: painting the inside of your hull
« Reply #5 on: November 09, 2008, 09:14:54 AM »

Hi  No Mustang Mark

Have you any ideas how to thin down fibreglass resin so I can brush a very thin layer on the hull.

Its a hole in the fibreglass covering that I've sanded through and want to make it good.

Or any other ideas would be appreciated. I know there is a thread on it but can't find it.

Sorry to high jack your thread portside but may be handy to know in the future

Seaspray

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portside II

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Re: painting the inside of your hull
« Reply #6 on: November 09, 2008, 03:34:54 PM »

Thanks lad's looks like thinning of gellcoat is a no no but resin is ok .
Mark where do i get the pigments from ,when i last tried the company i contacted would only do a 1kg tin far too much for me and the price was expesive too,
i did hear that you could use powder paints like what you let the children use with water .
daz
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barriew

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Re: painting the inside of your hull
« Reply #7 on: November 09, 2008, 03:49:42 PM »

Daz,

You could always have a word with that nice man in a Boat Shed not far from you - provided you don't mind the colour being rust {-)

Barrie
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portside II

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Re: painting the inside of your hull
« Reply #8 on: November 10, 2008, 02:04:11 PM »

Now thats a thought  %) , i will be there on the 29th for the xmas open day .
daz
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wallace

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Re: painting the inside of your hull
« Reply #9 on: January 21, 2009, 05:00:19 PM »

hi I just use crown gloss white paint about three coats always because if you drop anything inside you can see it as most things that fall in are dark my paint never comes off
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dave301bounty

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Re: painting the inside of your hull
« Reply #10 on: January 21, 2009, 07:07:37 PM »

Good advert there Wallace ,,,My Paint Never Comes Off,,
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tony52

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Re: painting the inside of your hull
« Reply #11 on: January 21, 2009, 11:20:48 PM »

Must say I never paint the inside of my wooden hulls. Glynn Guest's describes why not to paint the inside in his item in MB magazine on the 'PS Phantom'. Although this is a balsa craft Glynn still advises against painting the inside. Glynn even uses non waterproof adhesives.

Some years ago I new an 'old timer' type painter and decorator, who would advise people not to paint the inside and outside of a wooden garage. He would tell them to paint the outside only, says from experience as soon as the inside was painted (as well as the outside) the wood would rot.
Another builder would only allow the decorators to paint the external surface, ends and 1" up of the inside (bottom) only of a facia board. Again this was to allow the wood to breathe, where not exposed to the elements.

From these comments gathered over the years I have never painted the inside of a wooden hull, and have never had any problems. And I use balsa. Although should a non waterproof glue be used a weak varnish could be used over the glued seams.

My thoughts only.
Tony.




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brianc

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Re: painting the inside of your hull
« Reply #12 on: January 22, 2009, 12:31:45 AM »

I always use resin for the inside of my wooden hulls, i`ve had an old Billing Krabbenkutter for the last twenty odd years,sailed it for hundreds of hours and its still pristene inside  :-))
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tigertiger

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Re: painting the inside of your hull
« Reply #13 on: January 22, 2009, 03:43:38 AM »

I have seen a recent thread somewhere else that suggests a need to seal inside and out, I think RC Groups and I think the boat was the Riva Aquarama or similar.

Because of changes in humidity the planks shrank and the hull, although epoxied on the outside, started cracking.
It was suggested that sealing on the inside would lock in the moisture.

Although I have read on yet another post that all paints etc. breath. I am of a mind that sealing inside and out may be a good way to go for wooden hulls.

I will be doing this with mine, as I am building in 20% humidity, but I know when I go back to Shanghai it will be 90% + hunidity.

Any thoughts out there in Mayhem land?
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Proteus

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Re: painting the inside of your hull
« Reply #14 on: January 22, 2009, 06:28:48 AM »

Paint is ok as it is porous, but resin can trap any damp that will get trapped between and may have long term detrimental effect so resin one side only

Proteus
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tigertiger

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Re: painting the inside of your hull
« Reply #15 on: January 22, 2009, 09:28:51 AM »

The boat that cracked was resin coated on one side only, hence the shrinkage.

Any suggestions for  this issue anybbody, please.
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wallace

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Re: painting the inside of your hull
« Reply #16 on: January 22, 2009, 09:30:39 AM »

Thanks Dave well us at New Brighton Boat Club only do the best see u at the agm
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Peter Fitness

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Re: painting the inside of your hull
« Reply #17 on: January 22, 2009, 09:46:53 PM »

I use several coats of fibreglass resin, mainly to waterproof the wood.

Peter.
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John W E

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Re: painting the inside of your hull
« Reply #18 on: January 23, 2009, 08:51:57 PM »

The question that has been asked on this Topic i.e. whether or not to paint the inside of a wooden hull – give it some form of sealant or protection; is one of those questions which has no real definite answer.

This is because the answer will come from the person’s own knowledge and experience.

However, to make it easier to make a decision – rather than falling into the pitfalls of saying ‘well I paint the inside of my hull and it’s so good and lasted so many years etc., - or – I don’t paint the inside of my hull – and its lasted for years and years’….

Let us have a look at some basic facts. 

Let us have a look at our model – how much time does it spend on the water?    On average I would suspect that a model would spend at least 2 hours per week on the water – Sunday morning sail; and the rest of the week – normally being kept somewhere dry and reasonably damp free – in a stabilized environment.    In other words, it’s not in central heating one minute and then outside in the next.

Really the water doesn’t have much time to penetrate into the fibres of the timber.    That brings us to the next question we have to satisfy ourselves with ….

What timber is the hull made from?   There are a lot of hulls made with balsa wood – in the early 1950’s - 1960’s which are still around today.    This is because: -
Balsa wood (as well as absorbing water quickly) dries out quickly as well.   With this though when the balsa wood is wet – it does swell and distort a lot more than (shall we say) mahogany or Obechi.    For comparison if we have balsa wood which rapidly swells up when wet/damp we will have timbers like teak, mahogany and oak which swell but not as much and in between we have the likes of pine/Obechi which are roughly in the middle of the table of how much timber does swell up at a given intake of water.

So, we will take our Balsa wood hull; if we painted it with emulsion paints; this is one form of barrier to water which has been around for generations and, although the paint isn’t 100% waterproof (unless it’s a 2-part epoxy paint) – over a given time the water will penetrate the paint barrier and begin to enter the timber.   This timeline isn’t 2 hours though, like the time the hull is actually in the water.   The hull would have to be permanently in the water for a couple of months, before we saw signs of water penetration.

One of the other good characteristics of using paints directly onto soft woods; is that the paint will actually expand and contract along with the wood.   So, on a warm day when the wood expands – so will the paint – and it will be less likely for the paint to peel off.  Unless of course there is some defect between the paint and the wood.

Now, if we have the outside of the hull sealed with a paint barrier, but do not seal the inside of the hull, although – unless it is an open boat – there is little chance of water actually entering the inside of the hull unless the hull is actually breached.    If this is the case, apart from our model disappearing out of sight in a downward motion, this is going to allow water on the inside to the unprotected timbers.   This is where our trouble may begin.   As the planks begin to swell they try and force themselves off fixed positions – in other words where we have secured them to the frames and keels.   Some types of glue may accept this expansion and stretch with the plank, but, some may not and you may get failure in the spot.  Don’t forget the majority of the planks in the hull are glued to one another by the edge, so this is going to restrict the movement of the plank and this will cause cracking or splitting.   This scenario I am speaking about is going to the extreme where the hull has been submerged in water. 

On average then the hull which is made from soft planks and unprotected should survive a long length of time, as long as the exterior is kept in good condition and frequently maintained.

Now, the average modeller is like me – I PRESUME – and yes Dicky we do sometimes sail our models!    :-)) ;)

When we lift them out of the water, we disconnect the battery and wipe dry the bottom of the hull to stop it dripping all over the car, whilst transporting it back home.   When at home, we remove the batteries from the model to recharge them for the next sail – and we place the model promptly back on the shelf and forget about it.   
How many times do we check the inside of the model, behind each bulk head looking for water which has crept in via a leaky prop shaft/rudder post?

The only time we actually do this is when we see pools of water in the bottom of our model boat.

This is when – a hull which hasn’t been sealed on the inside, suffers the most.

The other thing to look at is for those of us, like me, who use a polyester resin to seal the outside of a hull as well as giving a good finish to the hull.   This polyester resin BE WARNED is not 100% water proof.   Over a given time, if constantly submerged, will allow water to penetrate.

Also, this polyester resin requires a top coat of either some form of paint; which in top has some form of varnish – the other thing about polyester is, that it is prone to UV rays/sunlight rays which do deteriorate it over time.

One of the disadvantages of using polyester resin and not sealing the inside is, polyester resin expands at a slower rate than wood.   Therefore if the inside of the hull becomes wet and it expands it will have a tendency to either split away from the polyester resin skin or even crack it.   This is why it is always best, if using polyester resin on the outside, to seal the inside.

So, you are in actual fact encapsulating the timbers and sealing them for life.

Although we paint the outside of a polyester coated hull; the only time to either varnish over the top of polyester resin on the inside, is, if we are building an open launch.   We could use the more expensive epoxies and you will find these are stronger and more durable than polyester resins.   They do have a greater resistance to water absorption especially those which have been manufactured for the marine market – but, these are a lot more expensive.   It is one of those decisions where – does the hull and the time it spends on the water – warrant the expense of a more expensive epoxy.

Last but not least, some hulls are manufactured with modelling quality plywood.    Now this does have different characteristics to normal wood – due to the fact that the plywood is built up of thin veneer layers which are laminated together and the glue which is used to laminate them, do 2 things.    It controls the expansion of the plywood when it is wet and also, it also forms a barrier – that is if the material used for bonding is of a marine grade.   

What would happen, is, that the water would penetrate the first veneer of ply, but, would be unable to penetrate through the glue bond, unless of course there are any defects in the bond.

A hull made from plywood – I would still personally seal the inside as well as the outside.

One last thing about sealing the inside; when you do this, whichever materials you use – either resin or paint – it will sink into all the little nooks and crannies and fill & seal them thus preventing any water/dampness accumulating in this area and started rot.

Hope this has instilled some food for thought.

Aye
John e
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Peter Fitness

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Re: painting the inside of your hull
« Reply #19 on: January 23, 2009, 09:29:16 PM »

Very well explained, John e,  :-)) and I'm pleased that you have vindicated my thinking. When I built my first model boat, only 5 years ago, I reasoned if a timber hull was sealed, inside and out, then it would be very difficult for water to penetrate the wood, therefore (in theory) protect it from  water damage. I have used this method on all my wooden hulls, and have had absolutely no problem whatsoever with water damage to any of the hulls.

Peter.
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Boz

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Re: painting the inside of your hull
« Reply #20 on: November 20, 2009, 07:52:16 PM »

Wood is constantly moving, as it absorbs and releases moisture due to changing humidity. If sealed on one side, it means that water or water vapour can enter on one side more easily than the other, which means it will behave differently - much like steaming wood one one side only to make it take on a bend profile. This could lead to warping or expansion/shrinkage if subjected to large humidity changes. Painting both sides means that the rate of moisture absorption is slowed almost to zero, and makes the wood more stable. You will only get rot if the wood is wet when painted, or there is a defect in the paint meaning water can get in and be trapped by the paint. In normal circumstances where a cherished model is looked after and dried after use an unpainted inside will give rise to few issues. But in my opinion, I would always paint and seal it fully given it is a wooden article floating in water.
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