Model Boat Mayhem
Technical, Techniques, Hints, and Tips => GRP & Epoxy => Topic started by: tigertiger on August 24, 2008, 10:36:08 am
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I have never FG a hull before.
How do you cut and fit the tissue/mat before applying the resin.
I am thinking about how you deal with the complex curves, as this could leave gaps or overlaping of the FG tissue/mat.
Is the gap or overlap a problem?
Does the FG stretch/compress to fill?
Or do you just sand and fill?
Advice and tips please.
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I tend to use strips of matting and laminate them for the complex shapes, almost like double diaganol planking. The matting does have some give but not much. If ypu brush the resin in you shouldn't have any air gaps. Its best to try and get as best finish as you can so you only need a min amount of filler.
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Just nipped down the workshop, hopfully this will give you the idea of how I am doing the lid for my new boat.
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Thanks Phil
That helps a lot. I would not have thought of doing it in strips.
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TigerTiger Hi there
If you have a look at the Cervia build; photographs numbered 50 and 51; you will see how I have cut the tissue matt into pleats and I have overlapped them; to accommodate for the radius of the bow and stern. This is the correct way; or should I say; one of the ways in which to get matt to fold into awkward places. Tissue matter is relatively easy to work with because of its lightness.
A good laminator can actually work the tissue and matting into very awkward corners by allowing the resin to dissolve the bonding agents of the matting and actually moving individual strands of the matting around. Be warned, this does take a lot of experience/practice.
The other thing to remember about matting/tissue/especially woven roven is that they do not fold over on top of each other - they tend to spring up, especially woven roven - trapping air inside.
I would also add that the last rule is, always apply your resin first, apply your matting, then with the aid of a roller and brush - draw the resin through the matting. This helps to eliminate trapping air into the resin.
Hope that helps a wee bit.
aye
John
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Hi tt, link to what John is on about. O0
http://www.modelboatmayhem.co.uk/forum/index.php?topic=7947.0
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Hi John
I see that there are overlaps in photos 50-51.
Are these pleats left as pleats, a triple thickness?
or do you cut to make an overlap, double thickness?
And then sand them down smooth afterwards.
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Hi ya there TT
The pleats are cut and overlapped so we have double thickness and as you say, when it has all cured and hardened - sand them down.
here is a tip for you; when you have put your top layer of resin over the tissue; put one or two brush hairs in the resin and leave them there - then when this coat of resin has dried give it another coating of resin over the top, allow that to go hard. When you come to sand it all back, watch for where you have put the hairs from the brush in the resin and when you have sanded down to the hairs, you know you are into the layer of the resin which contains the matting.
aye
john e
bluebird
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Thanks for that.
Does the fg tissue cut easily or does it have a tendency to pull and tear?
And what do you use to cut it?
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hi there TT
Yes fibre glass tissue cuts easily with a good pair of scissors/sharp bladed Stanley knife. Watch the fingers - snip snip.
aye
john
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Thanks
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Can i just say that when using matting you must tear it not cut it,this way when you use your resin the fibres will open up and interweave thus leaving no visible sign theres a join.If you cut it with scissors you will be left with a visible join and a not very strong bond as the fibres wont interweave with each other.Cloth is a different matter but csm must be torn not cut.Any tight corners just take some chopped strands mix them with some resin or gelcoat depending wether you using it and mix to a paste then spread this into any problem areas like corners strakes or keels etc,this works very well.Once thats done lay your resin and matting cloth etc over the top.
Mart
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Heres a few pics of the process these are from a friends build as i don't take as good pics as him %).he as i do allways overlap the matt by a few inches to dbl the thickness at the keel and up a few inches notice because he tore the edge of the matt you cant see a visible join as the fibres interweave with each other.finally a layer of cloth goes over the matt in one piece to add strength and a nicer look also.
Mart
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Hi
One trick i use when laminating in the keel area and the chines is to wet out some uni directional tows and lay them in first to reinforce them,This applies to both polyester lay-ups and epoxy build's.Then carry on with the subsequent ply's .There's always plenty of people on the forum that'll help!.
Good luck
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Just remember you cant use mat with epoxy because the matt has a binder that wont break down when using epoxy resin.
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Hi you Polyester buffs,
Having worked in the polyester industry for a number of years, I missed the tip about using respiration protection when working with mat, specially when you use it 'as it should' by tearing it, you'll release the tiny fibres in the air.
Once they get in your lungs, they are there to stay and reek havoc with your health.
So, wear suitable protection!!
Regards, Jan. (who only works with woven glasscloth and epoxy resin at home...)
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Yes i think i did mention you should only tear matting not cut but i forgot the bit about the mask lol.In any case when using thse materials allways read what it says on the tin so to speak and its all there for you regarding health and safetey.
Mart