Model Boat Mayhem
Technical, Techniques, Hints, and Tips => GRP & Epoxy => Topic started by: durhambargeman on April 03, 2007, 02:15:33 pm
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Hello, Back to the theme of applying fibreglass to a hull. Does anyone know the difference between fibreglass matting and fibreglass tissue? Having had a look at both I can see that the tissue is lighter in weight and thickness, but, is the tissue type suitable for doing the full job, or, is the tissue used for something else and not suitable for fibreglassing a complete hull?. If anyone has any experience of the two products I would appreciate their comments. Thankyou
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What type of construction is the hull ie. timber?
Richard ;)
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Are you talking about a wooden hull? Do you want simply to reinforce or waterproof it inside, or do you want to apply fibreglass on the outside as a finish? I think we need more information. Either way, tissue isn't really a suitable medium on its own. Its general use is as a backing for the surface gelcoat which is applied to the inside of a mould. After that, either chopped-strand matting or woven cloth is applied over the tissue to give the GRP moulding its strength and thickness.
There are several members of this forum who have much more experience of using fibreglass than I have . Let's hope one or more of them will be able to add some useful stuff to these bare bones!
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Hello again, The hull plywood framed with balsa planking.
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Send a Personal Message to Clive [ kendalboatman ]. One of his boats was thin birch ply and tissue.
Richard ;)
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Thanks, I`ll sen him a PM, cheers
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Kendalboatman.
Or anyone else. Please respnd in the public arena as I am also very interested in this topic.
Thanks
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Hello, Back to the theme of applying fibreglass to a hull. Does anyone know the difference between fibreglass matting and fibreglass tissue? Having had a look at both I can see that the tissue is lighter in weight and thickness, but, is the tissue type suitable for doing the full job, or, is the tissue used for something else and not suitable for fibreglassing a complete hull?. If anyone has any experience of the two products I would appreciate their comments. Thankyou
There's no single answer to this question, we really need to know what kind of boat hull is involved, and also how large it is. Glass tissue will add very little strength, it's only purpose is to create a resin-rich surface. Left to itself, anything more than a thin coat of resin will drain and create puddles, but the tissue will hold it while it cures, and for some applications a coat of resin with minimal glass reinforcement may be all you need. There are many grades of tissue, some more suitable for sheathing a hull than others, and some aren't too easy to apply, being happier to stick to your brush than the hull. so you keep dragging it all over the place. Having said all this however, it can be used successfully on small hulls. I've sheathed lots of hulls with glass, and I've almost always used glass mat. This adds a useful amount of strength, though also weight of course, and will resist knocks and other damage far better than tissue, or even thin glass cloth. The disadvantage is that it's not all that easy to apply, especially if the hull is a complicated shape. You'll really need a washer roller as well as a stiff brush to achieve a neat surface without air bubbles. Thin mat, say 300gm or 1oz in imperial measurements should be enough for most applications, but take care to cut panels fairly accurately to fit, and don't thin it by trying to stretch the wet glass too much over compound curves. When it's cured, use coarse paper on a sanding block to flatten the surface, then fill any small hollows that have been revealed with a filler like P-38. After this, a thin brushed coat of resin should rub down well enough for a primer coat of paint. These are a few basics, if you tell us more about your hull, there's probably quite a lot more I could add, and I've assumed that you are working with polyester materials, though you wouldn't normally think of using glass tissue with epoxy.
By the way, to be perfectly grammatical, your topic heading should have read 'Matting or Tissueing', as I think I've pointed out here more than once before, there is only one 'T' in mat, and the word 'matt' usually applies to a paint finish.
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Kayem is the expert on this subject but it might be worth mentioning that I have successfully sheathed hulls using nappy liner tissue and polyester resin. As Kayem says, the tissue holds the resin while it sets. The advantage of nappy liner tissue, which is similar in strength to GRP tissue before application, is that when you come to rub down you are not abrading glass in resin but tissue in resin which is a lot easier. Of course it helps that nappy liner tissue is specifically designed for bottoms too... ;)
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Hi there - I haven't many quibbles about Master Kayem's statement - I will give him 7/10 for it ;D but, the only thing I would pick up on - is I believe that this gentleman is building a Thames Barge planked with balsa wood and the last we heard was he was thinking about re-planking it as he was having trouble sanding the balsa wood down.
My thoughts are, I would tend to fibre glass on the inside first with one ounce matting and then when this is cured, I would go on to sheathe the exterior whichever weight of matting he prefers, either tissue or heavier matting. This will add strength and rigidity to the hull allowing a firmer surface to work on to extract the air bubbles without the fear of damaging the balsa wood planking.
aye
john e
bluebird
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What ?? Only seven out of ten ?!?!?!
I've never tried it, but I've heard of the Colin Bishop nappy liner suggestion before. Having no recent experience of babies, I don't have the materials to hand, but it certainly seems to be a worthwhile alternative. As glass tissue adds very little strength, I can't really see any downside, and it would be somewhat cheaper.
I've thought of something else I should have added to my earlier answer, I build mainly steamboats, tugs, and similar craft, nothing very racy. For any kind of I.C engined boat or a racing yacht, my answer would have been slightly different.
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If it is planked with balsa a thin coat of resin painted over the balsa will strengthen it considerably and make it more resistant to rubbing down.
When a reasonable finish then cover as recommended above.
Bob
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Hello All, Many thanks for all the replies and suggestions. I think that I will go for the heavier fibreglass mat rather than the tissue. I appreciate that this will add weight to an already weighty hull, but, I wonder if weight is really an issue here, after all, I will be adding about nine pounds of weighted false keel, so the stronger and tougher the hull the better, surely.
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Re: fibreglass: matting or tissue ,
There is yet another option, fibreglass cloth, woven mating [thanks for the reminder, kayem] various weights also.
OK so I am confused yet again :-\
"By the way, to be perfectly grammatical, your topic heading should have read 'Matting or Tissueing', as I think I've pointed out here more than once before, there is only one 'T' in mat, and the word 'matt' usually applies to a paint finish."
Time for bed zebadee!
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Re: fibreglass: matting or tissue ,
There is yet another option, fibreglass cloth, woven mating.......
Woven mating? That all sounds just a bit too Kama Sutra for me.
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Woven mating? That all sounds just a bit too Kama Sutra for me.
The instructions say you have to get it thoroughly impregnated to achieve the desired result...
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I have used all of this type of glass fibra.
Heavy, you can do a hull over a plug and add ribs to strengthen later.
Tissue, if I plank on frame the hull , I give it two coats of tissue.
Cloth, this you have to keep your eye on, plenty of resin needs to be pushed in to the cloth, and you have to stay with it till it near sets, some times it does not lie down as it should, and if it twists when setting , its a bit of a job to correct it.
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Woven mating? That all sounds just a bit too Kama Sutra for me.
The instructions say you have to get it thoroughly impregnated to achieve the desired result...
When you're mating you mean?!
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Just my penny- I have tried once and was badly surprised, so I decided never again balsa-planking. You need minimum two layers of tissue to stiffen the planking. I just had one layer and another guy hit my boat. Not too bad, but then I saw that the bump splitted the tissue and the balsa-planking started to burst. Since I prefer Plywood-stripes or any other wood for planking I never had this problem again.
Balsa, once hit- ist too soft to resist. Any other planking would gibe more resistance. Another advantage vs. Balsa. bals follows the curvage from frame to frame. If you look on it, it always look a bit squared. Any other wood follows the curvage, which takes you from filling and sanding to get a realistic curvage.
As said before, just my penny...
Jörg
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I've assumed that you are working with polyester materials, though you wouldn't normally think of using glass tissue with epoxy.
Hi Kayen,
Why do you say this? Is it because of relative cost or is there a technical reason?
Regards
TT
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I have a question about Fast Glass fibreglass mat/tissue/cloth.
Fast Glass do two grades that I have seen in Halfords etc.
One course and one finer. Does anybody know how each should be described as mat, tissue, or cloth?
and what the approximate weights of each are?
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I've recently bought some 'Fastglas' also only two sizes.
I bought the thicker which says on the pack "Glass Fibre Mat" (GFM-UP-0614) (no weight on it)
I can't remember the other ones description, but would say it was tissue, it was very flexible.
regards
Gary :)
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I am wondering if it is cloth, as opposed to tissue.
Some of the descriptions of tissue it that it rips up and tears very easily. Having no other products to compare it with I am at a loss.
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Just had a look on Halfords.co.UK
They have two 'Fastglas' products - 'Mat' and 'Tissue'
regards
Gary :)
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Thanks Gary