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Author Topic: Fibreglass a Hull  (Read 5004 times)

Henry70x

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Fibreglass a Hull
« on: August 29, 2016, 08:59:00 am »

I am going to fibreglass the external part of the hull which has a thin ply skin.
I have read conflicting methods:
a) Cover with strips over lapping at the keel.
b) Lay a complete sheet over the hull.
The question is which is right or best, and is there another method which any one has tried and had succeeded with.
Look forward to your replies.
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canabus

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Re: Fibreglass a Hull
« Reply #1 on: August 29, 2016, 10:09:17 am »

Hi Henry 70x
A number of boaters use a ladies stocking, but apply a coat of resin first as I restored a boat which the resin had not bonded to the plywood.
So I removed it all and only fibreglass resin the plywood.
But before hand I used car spray putty to seal the plywood(sanded finds the high and low spots).
The final coat of resin I applied with a cheap foam paint brush, this gives a smooth finish and less scanning down.

Hope this helps.
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Sonar

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Re: Fibreglass a Hull
« Reply #2 on: August 29, 2016, 11:07:28 am »

I am going to fibreglass the external part of the hull which has a thin ply skin.
I have read conflicting methods:
a) Cover with strips over lapping at the keel.
b) Lay a complete sheet over the hull.
The question is which is right or best, and is there another method which any one has tried and had succeeded with.
Look forward to your replies.

If your using Fibreglass.

Tear all the joints so they mash into each other that way there will be NO lumps
When cured sand down to as smooth as you can without going through the glass layer.

Several way for a finish now the first is car body filler and sand to smooth using higher grades af sand paper then a very fine coat of gold top car body stopper  .
Sand again and paint.

The other option is a little harder to sand is flowcoat

Make sure it is warm do not add too much catalyst  then apply thinly using a brush or foam roller the roller will do about one coat before it is useless.
Sand fully down between each coat as Flowcoat has a wax in it the will come to the top on every additional coat. Unsanded it will peel off.

The filler method is the way I would do a small hull.

Just to seal a hull for paint there is another way resin and glass fibre Tissue same method as Laminating  but very little if any strength in the layers.


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Brian60

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Re: Fibreglass a Hull
« Reply #3 on: August 29, 2016, 01:40:44 pm »

The material of choice would be fibreglass cloth, not mat. Mat is too heavy and you will lose any definition in the hull. Buy the lightest cloth you can, remember its alrady waterproof with the timber, you are using the grp as a belts and braces waterproofing/strengthener. Make sure it is well wetted out when you apply it or tends to form bubbles that are a nightmare to remove. Again do not try to do it one complete piece, I've seen this go badly wrong. Large flat section can be done as one piece but when you get to compound curves smaller is better, but don't go for large overlaps in the cloth, keep them as small as possible.

Once its set up 24-48 hours for maximum strength either 'paint' the outside with more resin or better yet flowcoat resin. Once that has gone off another 24-48 hours, sand until smooth, the extra resin coat on the outside will help fill any weave of the cloth that wants to misbehave.

John W E

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Re: Fibreglass a Hull
« Reply #4 on: August 29, 2016, 04:52:13 pm »

Hi there Henry, is this a plywood hull - the Fire Tug Gatcombe? which you were discussing earlier - about construction methods.    I have just read through the article in Model Boats Special Issue 2015 - where it states in the article that the hull was planked in plywood strips - are you thinking about/have you already planked the hull in plywood strips?

If you haven't done so and just considering it - as you can see there are several ways of sealing a hull.

I believe we may have already put a link on to the Cervia Tug build in the Masterclass - also in amongst the masterclass builds you will see several other builds which I have done - and others too - on the trawler hull I did I also fibreglassed the external of the hull; then covered it with plasticard to assimilate shell plating.

If you let us know that it is the hull tug Gatcombe that you are contemplating or have already built; then we will be able to help you with various processes of sealing that hull.  Do you have the article from the Model Boats Special 2015?

John
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Henry70x

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Re: Fibreglass a Hull
« Reply #5 on: August 29, 2016, 08:51:46 pm »

Thanks to all for your input.
To Bluebird: Yes the hull is ply strips, and the model the Fire Tug Gatcombe.
I received from another member of Model Boat Mayhem a copy of the article, and have since accorded a copy of the magazine Model Boats 65 years of modelling, which this article comes from.
I have 1oz Super Lightweight Glassfibre Laminating Fabric, and the resin is due to arrive on Wednesday 31st August, so in the mean time I am reading anything I can find on the process. Any help will be appreciated.
Thanks
Henry !
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John W E

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Re: Fibreglass a Hull
« Reply #6 on: August 30, 2016, 05:52:15 pm »

hello Henry

are you proposing to seal the hull as the article mentions, where you apply cheap masking tape to the exterior of the hull to prevent leaks and then fibre glass with the matting on the internals of the hull?

The reason I ask you this

1.   Advantages

It does make a slightly stronger hull when you fibre glass on the inside - but - that is about it

2.   Disadvantages

The disadvantages of fibreglassing in between frames is it can be extremely difficult to get the matt to lie properly over the planks and between the frames without a lot of air bubbles.   The other thing is if you taped the exterior of the hull it is extremely difficult to get the tape off and you may end up sanding it off - how do I know this - I have done that and got the teeshirt. :-)

The other thing to discuss is are you going to use polyester resin or epoxy resin?   One of the problems of working with polyester resins is you have to get the ratio right between hardener and resin and this can vary between manufacturers - depending on who supplies it to you.

If you add too much hardener, you literally can end up with a chemical fire.    If you don't add enough you end up with a sticky mess which can stay sticky forever and you end up scraping it all off.

Also, you have to have the correct temperatures to work in.

Epoxy resins especially Z Epoxy I have found personally is easier to work with and I have found it more forgiving and its a mix of 1 : 1 normally.   To me its a lot easier to calculate your quantities.     It is not so much affected by outside temperatures and also the other thing is its not so 'smelly' as a polyester resin.

From what I can see, you have already pre-ordered your matting and it sounds likes its a woven matting - similar to a material - rather than fibreglass matting which is pieces of short strand glass bonded together with a bonding agent which breaks down when polyester resin is mixed with it and NOT EPOXY resin - Epoxy resins will not break down the bonding agent in the chop strand matting but it will work well with woven matting.  The trick here is to apply your Epoxy first to the hull and then lay the matting over the top of the wet epoxy mix and staple the resin through the matting.   A lot of people make a mistake of pouring resin on top of the matting and trying to work the resin through.

If you are happy with what you are reading and quite comfortable and decide which way you want to try it (in other words what resin you are going to use - epoxy or polyester) and also are you going to fibreglass inside the hull or would you like to do it a different way - similar to the way in which I sealed the Cervia Tug Hull.?   This does have its advantages as well -

John
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Henry70x

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Re: Fibreglass a Hull
« Reply #7 on: August 30, 2016, 06:25:37 pm »

Hi Bluebird,
                I already have the Glassfibre Laminating Fabric ( from Deluxe Materials ), the epoxy which should arrive tomorrow ( Wednesday 31st ). I note what you say about sealing the inside of the hull, which is as per the article in the magazine, and on reflection will not attempt to do it.
I am slowly working my way through your build article on the Forum re: cervixHEnry p Tug.
As this will be my first attempt at epoxy resin to the hull I'm rather cautious, but understand that once I start I will be committed ( probably should be  :-)  )(committed that is )
Thanks for your insight, and guidance.
HENRY 70x
( David )

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John W E

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Re: Fibreglass a Hull
« Reply #8 on: August 30, 2016, 06:29:19 pm »

I see you must have women on your mind, never mind tugs - i.e. cervix :-)  I like it
 :-)) :-)) :-)) {-) {-) {-) {-) {-)
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Henry70x

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Re: Fibreglass a Hull
« Reply #9 on: August 30, 2016, 07:39:58 pm »

Hi Bluebird,
                 Sorry about the mis- spelling, was not being disrespectful about your article, or the build, it's the one finger typist or modern technology, you know what they say about " old dogs and new tricks ;) )
As for women on my mind that's the only place they are likely to be these days <:( .
Just had a late delivery from the "river people" so its take the bit by the teeth tomorrow and start with the epoxy resin on the hull, will let you know how things go.
HENRY. 70x
( David )
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nivapilot

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Re: Fibreglass a Hull
« Reply #10 on: August 31, 2016, 07:47:54 am »

I am new to modelling and have an old model boat in the form of a river/broads type cruiser.
It was made of wood, ply and solid wood......it apparently was the first model a 90yr old made a long time ago.

The paint started to split, and being fearful of losing the boat due to water ingress, I decided to strip the paint off and fibreglass the hull, to strengthen and seal it................it also was to be my first time............

I read about it, and watched a couple of youtube videos......and then bought, some z-poxy, some 28gram / 1oz cloth and some methylated spirit.....I know......but I did say I'm new to this.....

I started by thinning down some z-poxy and applied to the hull with a brush....tried to lay the mat over the hull and came against my first problem.....double curves....welll as I was already committed, I cut the mat and laid as best as I could over the hull.....eventually ending up with double layers in places, I hen laid another piece of cloth over the keel and made sure that all corners and sharp bends were well seated......walked away and left for 24hrs to harden......it looked carp.

I left it another 24hrs and then started the sanding process, down to 1200 wet and dry, used wet, and the hull is lovely and smooth, I am very pleased with it as a first attempt.

If you make a start and it starts to go wrong.......walk away from it......don't overwork the resin and mat.......come back to it after 24hrs and sand it back and start again.....the results will be worth it.
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John W E

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Re: Fibreglass a Hull
« Reply #11 on: August 31, 2016, 08:40:07 am »

Hi there
I wasn't meaning to pick u upon your mis spelling of Cervia, it made me really laugh :-)
If you are u are unsure about fibreglassing -one of the tricks of the trade is to cut an end piece off and play around - i.e mix abit of resin and bit of scrap mat and try that on a bit of wood.
You can get small tumblers - similar to the ones you measure medicines in.   get some of them and keep one for hardener and one for resin - using the graduated marks on the side of the tumblers so you get the measure of resin right.
Last thing I know a lot of people talk about mixing methylated spirit with epoxy resins to thin them down but if you are new to the game forget it - it doesn't really work that well.   The resins, if you work it properly. will work well and work in easy.
John :-)
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Subculture

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Re: Fibreglass a Hull
« Reply #12 on: August 31, 2016, 09:23:57 am »

If the hull is very curvy you should use a twill weave cloth. This drapes very well and conforms to the curves without creasing and offering resistance.

Epoxy resin is better to work with on this sort of thing than polyester. Firstly it's much slower in curing, giving the laminator much more time to work, secondly it's tougher, more resistant and doesn't stink to high heaven.

Downsides, it must be kept warm to cure well, and it's expensive compared with polyester.
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Henry70x

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Re: Fibreglass a Hull
« Reply #13 on: August 31, 2016, 09:30:55 am »

Hi All,
          Having received my resin later yesterday evening the next problem I encounter is,
The instructions state the mix is at a ratio of 100 to 1, and only wishing to mix a small quantity initially any ideas how I can measure such small quantities of hardener.
Thanks any input welcome
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Subculture

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Re: Fibreglass a Hull
« Reply #14 on: August 31, 2016, 10:40:46 am »

I use a pipette (ebay sell them cheap, you want the very small 0.5ml-1ml type). However you do have a fair amount of tolerance, the trick is, don't mix too much up at once, especially on a hot day.
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Brian60

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Re: Fibreglass a Hull
« Reply #15 on: August 31, 2016, 11:20:41 am »

Resins are usually mixed by weight not quantity, so get yourself a set of cheap electronic kitchen scales, mine read up to two kilo in gram increments.

With these you can weigh out 100,200,300 or whatever amount of resin you require. For instance in your case 100/1 ratio, weigh out 100grams resin and then squirt in 1 gram of catalyst from the bottle supplied. The catalyst usually comes in a squirty bottle.

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Re: Fibreglass a Hull
« Reply #16 on: August 31, 2016, 12:25:04 pm »

I find volume works fine for me with polyester resins. I use weight with epoxy, which is much more critical, and you use a lot more hardener than polyester.
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Henry70x

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Re: Fibreglass a Hull
« Reply #17 on: September 01, 2016, 06:13:49 pm »

Well I've been and gone and done it :-))  Fibreglassed my hull, it's the first time I've done this, and it went great, very pleased with the results so far, still work in progress, rubbing down etc. I wish I got into this fibreglassing a long time ago.
Thanks to all who led me along the path.
HENRY70x
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Re: Fibreglass a Hull
« Reply #18 on: September 01, 2016, 06:23:44 pm »

Well done Henry :-))


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Brian60

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Re: Fibreglass a Hull
« Reply #19 on: September 01, 2016, 06:40:39 pm »

 :-)) :-))

Brian60

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Re: Fibreglass a Hull
« Reply #20 on: September 02, 2016, 02:41:55 pm »

Make sure when rubbing down that you are covered. hands, face, arms. don't leave any skin uncovered, were goggles of some description and a breathing mask.

You might consider this overkill, but there is nothing worse than the dust created from sanding grp for irritation. Imagine rubbing the old fashioned itching powder you used to buy as kids - its worse than that. You don't want to be breathing it in either.

You don't notice at first, but 30 minutes later as it works into the skin pores it itches and burns. Its not easy to get rid of either, lots of soap and water and a cloth to wipe with.

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Re: Fibreglass a Hull
« Reply #21 on: September 02, 2016, 05:51:30 pm »

After a bit of a lay off, then re-organising the workshop and then getting around to fit the anchor ports and bulwarks, I have bitten the bullet and fibreglassed my GRANIT.


All I can say is thank you to those who have put up comprehensive details on how to do this. I was very apprehensive at first, the thought of ruining the hull was my main concern, but decided do or die and so far it has gone better than expected. I just have the last coat to go on then just a matter of rubbing down to get a nice smooth surface.


I shall post pictures etc on my thread as soon as I have finished this process.


Thanks once again Mayhemers, appreciated.


Stewart
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