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Author Topic: Chopped Strand Matting - Strength to weight  (Read 4370 times)

longshanks

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Chopped Strand Matting - Strength to weight
« on: October 06, 2010, 10:33:28 pm »

Hi Folks

Need some input.

Looking to build some hulls, dimensions ranging from 25 x 5" x 2.8lbs (635 x 125mm x 1.27kgs) to 40 x 7" x 5.5lbs (1016 x 178mm x 2.5kgs). Two to four props and associated gear. Weight given is the total displacement of the hull and equipment.

I need to build the hulls as light as possible but still have reasonable strength.

Will I be better to go for 3 x 100gm chopped strand matting or 1 x 300gm CSM? Cant find 150gm csm

Am I right in thinking three layers 2/3 times heavier due to resin used?

I cant help thinking that the 300gm csm is going to be difficult to work into the tight areas of the hull.

Anythoughts gratefully received
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Peter Fitness

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Re: Chopped Strand Matting - Strength to weight
« Reply #1 on: October 07, 2010, 01:06:15 am »

I have actually found the chopped strand matting easier to use in tight corners, although I only use it for reinforcing a wooden hull. I assume you're thinking of making a full fibreglass hull?

Peter.
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nick_75au

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Re: Chopped Strand Matting - Strength to weight
« Reply #2 on: October 07, 2010, 09:47:37 am »

The highest glass to resin ratios are obtained with woven cloths rather than CSM, CSM though gives stiffer panels, I use 600 GSM Chopped mat but parted to a light layer then a heavy layer, you can peel apart heaver CSM to make two or even three layers.
For the sharpest corners a fillet of bog makes the lay-up much easier. The bog needs to be slow setting like the resin not car filler, so the glass is layyed wet on wet(bog)

Nick 
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longshanks

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Re: Chopped Strand Matting - Strength to weight
« Reply #3 on: October 07, 2010, 10:01:37 pm »

Yes Peter full hulls - lightweight I hope.

Nick, Can you explain what a bog is ?

Cheers guys
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Peter Fitness

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Re: Chopped Strand Matting - Strength to weight
« Reply #4 on: October 07, 2010, 11:13:02 pm »

Bog = Aussie slang for car body filler, although Nick suggests using a slow setting variety. Some fillers cure quite quickly, especially in warm weather.

Peter.
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nick_75au

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Re: Chopped Strand Matting - Strength to weight
« Reply #5 on: October 09, 2010, 11:59:09 am »

Peter has it, sorry I thought it was a universal term. The product I have used is called Pro bond, it is mixed the same way as the resin Ie with MEKP, not the standard tube of hardener that comes with body filler.

Nick
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Ticonderoga

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Re: Chopped Strand Matting - Strength to weight
« Reply #6 on: November 10, 2010, 05:39:06 am »

I have actually found the chopped strand matting easier to use in tight corners, although I only use it for reinforcing a wooden hull. I assume you're thinking of making a full fibreglass hull?

Peter.

Hi Peter,

What brand do you use for your CSM matting, weight etc., and where did you get it?

Sorry for the barrage of questions

Regards,

Andrew
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martno1fan

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Re: Chopped Strand Matting - Strength to weight
« Reply #7 on: June 01, 2011, 04:29:28 am »

Yes Peter full hulls - lightweight I hope.

Nick, Can you explain what a bog is ?

Cheers guys
For anyone planning on trying this make your own bog using the same resin you intend using for the layup,take some resin in a small tub mix in some fine chopped strands of glass available at any glass supplier then mix in your catalyst take a small silicone spatula or cake mixer (ice lolly stick will do but not as good) and spread this into all tight corners edges and strakes if you have them then glass as normal.If your using polyester resin use the bog after you have applied your 2 coats of gelcoat  ok2.As for using csm it will work fine but as suggested split it into two layers and id also buy some tissue matt and use this as your first layer.Be aware you cant use epoxy resin with normal csm as it wont break down the binder holding the matt together.
Mart
heres a pic of the bog mix i apply in my moulds when i build my hulls,if you need any more info shoot me a pm im glad to help
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Howard Q

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Re: Chopped Strand Matting - Strength to weight
« Reply #8 on: June 02, 2011, 11:20:36 pm »

I will probably be shot down, but, in the past I have used the sheets of the non- woven fabric called "nappy liners" :-)) :-) as these are extremely flexible and very absorbant, a good carrier for the resin. The model you are building will be the deciding factor in your choice. The fact that these items are user friendly is a bonus, no fibres to collect in your clothing or breath in, you will have to shop around but the store well known for baby supplies is a good source, an extra plus is they are relatively cheap. P.S. please ensure SWMBO is aware you are not getting broody. Howard.
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Colin Bishop

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Re: Chopped Strand Matting - Strength to weight
« Reply #9 on: June 02, 2011, 11:52:39 pm »

Howard, at last! Another advocate of nappy liners. These make an ideal substitute for GRP tissue (if unused!) and are much easer to rub down. I used them on my Isle of Wight ferry Shanklin back in the 1980s so there is nothing new under the sun. Thoroughly recommended.

Also worth considering using Deluxe Materials EzeCote which is a one part polyurethane resin with water cleanup. http://www.deluxematerials.com/products_building.html I have been tryingt it out and have been very impressed with it.

Colin
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