cutting grp

[suse]

I want to cut away part of a very large cool box to fit much needed cupboard space. I dont like the idea of cutting grp - which mask should I use? Any other dust-damping suggestions, etc? I shall be using a jigsaw - the grp is quite thick - and a hacksaw for inaccessible bits. The plan is to replace the cut-off end of the (smaller) cool box with plywood glued in place. Will this be OK? The ply will be waterproofed and insulated. If I put the insulation on the INSIDE of the cool box, what sort should I use? At present there is a drain at the lowest point, which drains into a locker (!) If I fix a duckboard within the cool box, and am prepared to mop up regularly (actually, I have to do this to clean it, anyway), surely I can do away with a drain. It wouldnt be easy to arrange a drain to the very shallow bilges.

As ever, all comments and suggestions appreciated. Thanks.

Susy

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[gtmoore]

I find these rotary saw tools excellent for cutting GRP. I bought one called a RotoZip after borrowing one from a friend but I would imagine they are all similar.

The GRP blunts the bits quite quickly but it's far neater than a jigsaw and more accurate. I've used mine with great success to put in a portlight and a couple of instruments. If you finish off with one of those flappy sandpaper tools that go in your drill (what are they called?) you can get a very good finish indeed.

They do make some mess but don't splinter the GRP at all although the liberal coating of white gelcoat powder just about everywhere is another matter!



<hr width=100% size=1><font color=blue>Gavin </font color=blue>

 

[Mudplugger]

Suzy, 1) must admit that a I used a normal solvent paint mask with no problems.
2) didn't haveany difficulties cutting F/glass with Jigsaw, but you can stop a lot of splintering if you use Duck tape to edge where you are cutting, ( both sides of cut) it gives you a guide and a surface to run the J/saw on.
3) You need about 3" of Polystyrene on the inside, might be worth thinking of a plywood/poly/ply sandwich.
4) If you don't drain, can get a tad maloderous.. can you fit a tap with a tube to drain into a container?
Regards Tony W

<hr width=100% size=1>Tony W.

 

[snowleopard]

for cutting grp, a hacksaw blade in a jigsaw works well. the fastest cut is a metal cutting disc in a 4.5in angle grinder but the dust created is horrendous in a confined space.

no need to be too paranoid about the dust, a simple bra-cup type mask is fine. the skin irritation is a bigger problem, wearing rubber gloves will reduce the itching around the fingers.

a good insulation material is cavity wall batts, fro a builders merchant. it's about an inch thick and faced with foil.

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[john_morris_uk]

The best blade I have found for cutting GRP with a jig saw is a funny looking blade which doesn't have teeth but a sort of 'burred edge' in tungsten carbide or similar.

GRP blunts even best quality high speed steel very quickly.

The fibre glass dust is not particularly toxic as I understand things, but it is very very irritating to the skin. Barrier creams and gloves are the order of the day if you don't want to be scratching for hours afterwards.

<hr width=100% size=1><P ID="edit"><FONT SIZE=-1>Edited by john_morris_uk on 13/09/2004 20:18 (server time).</FONT></P>

 

[bruce]

you can reduce some dust by holding a vac hose next to the cutting blade while cutting, think the rotozip has a vac attachment.

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[sailorman]

Hi Suzie
try this site the fien multi-master is a great bit-o-kit i borrowed one from my local yard workshops.
it "ossolates" rather than spin ( re angle grinder ) & makes little dust, their not even expensive & mave many uses
http://www.1926woodflooring.co.uk/fein/fein_multimaster.htm
roger

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[Talbot]

<<The fibre glass dust is not particularly toxic as I understand things>>

If you breath in the dust enough you can get some very nasty breathing problems. The dust gets into the lungs and cannot be removed by bodily processes, so it just sits there interfering with our bodies ability to extract oxygen into the bloodsteam. A decent mask is essential. plus full clothing protection preferably with seals at neck and wrists. Fibreglass dust on the outside is not life threatening, but exceeedingly irratating (essentially is is ground up glass). It can cause a very bad rash, and even in a bad case where it is rubbed into the skin, can actually cause bleeding.

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[Strathglass]

If you have a jigsaw then get a ceramic tile cutting blade.
This will last a lot longer than normal blades and give a cleaner cut. Also not too much dust. A simple face mask and decent gloves should be adequate.
I have also used a segmented diamond cutting disk in a small grinder, very effective, but very, very messy.

Iain


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[Spuddy]

I had to use an angle grinder for a leak repair which produced fine dust all over the boat. Use the other lower speed tools mentioned.
My view is that the cheap masks didn't keep out the particles that clogged up lungs. It might be that other tools produce larger particles, but I'd still go to a decent pro tool shop and get a mask that looks like a WW2 gas mask with the appropriate filters: might cost £20-£30.
spuddy

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[oldsaltoz]

G'day Susy,

First a little note: You only have one set of lungs and baring a transplant later they have to last you a lifetime, so get a decent respirator, you will need one from time to time around boats so it won't be a waste.

I would also suggest some protection for your eyes and ear plugs as well a gloves.

If you are cutting fibreglass, have a very hot shower and pad yourself dry then smother yourself in talcum powder when your skin is still warm, the powder will get into the pores of your skin and any itching will stop after you shower at the end of the job, put plenty on neck, wrists, ankles and waist area, use long sleeve top and tape the cuff to your wrist.

I find an angle grinder with a diamond wheel cuts a clean and neat line in fibreglass, just rest the guard on the surface to control the depth. A fan located at one end of the boat with the hatch open should provide a good supply of dust free air and blow most of the dust generated out the other end.

If you only need to shorten the cooler box, can you cut a slice out and re-glass the end? this way you don't have to replace anything. I you need to rebuild the end, may I suggest you use closed cell foam, easy to work with, light, won't rot and has good insulation qualities.

Any timber will need treating for rot and sealing with an epoxy resin as wax or standard resins will stick to timber over a long period.

Any insulation should be at least 3 inches thick, and you should get rid of the drain, they are a major contributor to poor performance in cooler boxes.

Also note, only use epoxy resins and fabric designed for use with epoxy, no chopped strand mat or the join will be weak as it will hold too much resin. you should aim for a one to one ration of glass and resin with epoxy as opposed to the one glass to 3 resin with standard resins.

I hope this helps

Avagoodweekend........



<hr width=100% size=1> Old Salt Oz /forums/images/icons/cool.gif Growing old is unavoidable. However, growing up is still optional.

 

[john_morris_uk]

Apologies if I was ambiguous. I was referring to the inert properties of the dust - not suggesting that you should breath it in!!

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[LORDNELSON]

Re the good mask, I use a visor type one that has a built in fan powered by a small re-chargeable battery and the mask is sealed round the neck and back of the head. The fan drags air in through a filter and passes the air down the inside front of the mask keeping the visor free of condensation. Works very well and is, by my standards expensive, about £200, however as Oz indicates you only have one pair of lungs. An advantage is that the mask keeps dust off your face, neck as well.

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[StugeronSteve]

Hi Talbot, it is my understanding that glass fibre is body soluble, asbestos and conventional ceramic fibres aren't. I am not too sure what effect the chemical cocktail contained within the resins has on the respiratory system though, particularly is the volatilize during the cutting, but I've a good idea that they're not going to do a power of good.

Don't get me wrong, I am not suggesting that work should be undertaken without respiratory protection (FFP3 min standard), as I firmly believe that all dust is harmful in some measure.

Suze, damping is useless and the best dust control is "shadow vacuuming", using a vac hose as localized dust extraction, as already suggested. Do make sure that the vac has got high efficiency filters though, or it will just suck in the fibre, mash it up and blow it back out in an even finer state.

If you are doing the job inside the boat take all of the soft furnishings out, you will find it easier to clean up and you won't be itching for evermore.

Steve.

<hr width=100% size=1>Think I'll draw some little rabbits on my head, from a distance they might be mistaken for hairs.

 

[StugeronSteve]

Good advice, the disposable coveralls, including a hood, are excellent and available from B&Q etc. A good smear of barrier cream on the exposed parts helps as well. I presume that the area Suze is going to cut is fairly limited and, as such, this will not be too lengthy proceedure. It may, therefore, therefore be possible for Suze to form a sort polythene enclosure with armholes through which, visibility permitting, she can operate the cutter.

<hr width=100% size=1>Think I'll draw some little rabbits on my head, from a distance they might be mistaken for hairs.

 

[Graham_Wright]

Gets in your eyes as well.

If you carry diving kit on board (as I and many others do) then would full face mask and demand valve use have any disadvantages (apart from its cumbersome properties)?

<hr width=100% size=1>GBW

 

[snowleopard]

i have to say this thread is getting a bit out of hand!

i have built 2 40-footers from grp from scratch, under the guidance of a designer who has been doing it since the 60's. he cuts glass with an angle grinder while dressed in shorts with no mask and has been doing so for nearly 40 years. i am a little more cautious, wearing a dust filter respirator and specs, i wash off the dust afterwards with cold water.

if you are sawing the grp there will be very little airborne dust so encasing yourself in a space suit is, IMO, a bit over the top! however the choice is yours.

epoxy resin is in another league altogether and it is common to develop a serious allergic reaction to the resin which is permanent thereafter.

as regards bonding to the cut ends, the vital thing is that you abrade the bare grp thoroughly as there is a thin film of wax on the surface. new polyester resin does bond to old grp, whatever others may tell you. if it didn't my boats would have fallen to bits long since. the bond strength is 70-80% of the original. epoxy is approximately the same. the big difference is that polyester does not form a permanent bond with wood so epoxy must be used when bonding grp to ply.

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[Lee_Shaw]

Disposable, Type P2 dust mask will be fine.

<hr width=100% size=1>Steve

 

[MLBURGE]

Hi as for the best means to make the cut i find a jigsaw with the plastics/grp cutting blade. You can buy a pack of assorted jigsaw blades in 'wickes' the one you wan't is the small black one with a sort of rough edge, this cuts easily and neatly and shouldn't chip, although it is better to cut through a masking or similar tape. this should be as quick as a grinder but won't produce much dust.

hope helps. about a fiver for the blades i think

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[roger]

I feel theres a lot to be said for using a hand powered hacksaw. Its hard work but I dont think the dust goes so far.
As far as the construction goes Waeco say that Polyurethane foam (closed cell) is a much better insulator than polystyrene. YOu can get it aluminium foil coated both sides from a builders merchant. I think it is called Celotex board. I used it for my home built fridge enclosure.
For the inner lining I used expanded PVC sheets of the sort used by contractors who put replacement barge and soffit boards on windows. These contractors often also do double glazing. The boards have one matte and one shiny surface, they are easily cut with woodworking tools and can be glued together with a special cyanoacrylate glue sold by the contractors if you are accurate at cuutting or with sikaflex if you arent. The resulting surface is easy to clean but a little fragile.

<hr width=100% size=1>Roger