DOILY
Active Member
I plan to use epoxy and 2 inch wide strips of cloth. Do I need to be worried about the effects of gravity? Should I use a filler? I've heard about using cling film and adhesive tape. Is it necessary?
Overhead grp repairs
- Thread starter DOILY
- Start date
NUTMEG
Well-Known Member
Horrible. Did this last spring. Getting epoxy out of hair and beard was not fun. Ruined trousers and tee shirt, soaked through paper overalls. Easier to tip boat upside down in my opinion. Still shudder just thinking about mess I made. Best of luck mate.
sailorman
Well-Known Member
epoxy & tape / woven roving`s are very difficult upside down. it is a real skill / knack, do a trial section first with no more than 2 > 3 layers @ a time. if you need more layers than this therer is a special scrim added to the last lay-up that is pulled off when epoxy has cured, this gives a "bobboly" surface to aid mechanical bond with subsequent layup
boatbuilder
Well-Known Member
Mix epoxy with colloidal silica to make a paste, paint onto suface.
Wet out glass off the job and roll onto a reel.
With a consolidator in one hane roll out glass and consolidate as you go.
Easy peasy do it all the time.
Wet out glass off the job and roll onto a reel.
With a consolidator in one hane roll out glass and consolidate as you go.
Easy peasy do it all the time.
Stemar
Well-Known Member
As Sophie19 says, Horrible.
Uncured epoxy has almost no tack, so any weight will just fall off and, from memory as it's a few years since I did any, thickening doesn't make it noticeably better, just harder to wet out the glass cloth.
I had to fill a hole in the bottom of Jissel a few years ago and my carefully built up layers just fell out a few minutes after I'd got it all perfect! Fortunately I noticed in time and was able to get get the whole lot back and hold it in place with a piece of cling film covered ply propped up on some timber. It must have been OK as she's still afloat!
A couple of layers may stay up on their own, but any more and it's definitely taking a risk.
Doing it again, I'd prepare a piece of cardboard covered in cling film, tape it on one side so it's hanging out of the way of the job, do the dreadful deed and quickly smooth the cardboard over the job and attach it all round. If that doesn't give the shape you need, prop it with a piece of wood.
BTW, don't use ordinary chopped strand mat if you're using epoxy resin. it contains a binder that dissolves in polyester, but will mess up epoxy just fine!
Finally, lots of plastic sheeting to protect everything including you and neoprene or latex gloves for your hands is the order of the day. Epoxy can be quite unfriendly.
Good luck!
Uncured epoxy has almost no tack, so any weight will just fall off and, from memory as it's a few years since I did any, thickening doesn't make it noticeably better, just harder to wet out the glass cloth.
I had to fill a hole in the bottom of Jissel a few years ago and my carefully built up layers just fell out a few minutes after I'd got it all perfect! Fortunately I noticed in time and was able to get get the whole lot back and hold it in place with a piece of cling film covered ply propped up on some timber. It must have been OK as she's still afloat!
A couple of layers may stay up on their own, but any more and it's definitely taking a risk.
Doing it again, I'd prepare a piece of cardboard covered in cling film, tape it on one side so it's hanging out of the way of the job, do the dreadful deed and quickly smooth the cardboard over the job and attach it all round. If that doesn't give the shape you need, prop it with a piece of wood.
BTW, don't use ordinary chopped strand mat if you're using epoxy resin. it contains a binder that dissolves in polyester, but will mess up epoxy just fine!
Finally, lots of plastic sheeting to protect everything including you and neoprene or latex gloves for your hands is the order of the day. Epoxy can be quite unfriendly.
Good luck!
cimo
Well-Known Member
wet your surface. wet your cloth and roll up onto a piece of wavin pipe. unroll cloth onto surface while counteracting effects of gravity with brush. repeat. glasses would be good.
boatbuilder
Well-Known Member
The other thing is why are you using epoxy on what I presume is a polyester boat, polyester is a 1/10th of the price, try to use powder bound cloth , but if you are using polyester thenemoulsion bound cloth is ok.
We regulaly do 12 metre overhead hull joins, as long as you are organised than no prob , if you can get two people on the job then it is even easier.
We regulaly do 12 metre overhead hull joins, as long as you are organised than no prob , if you can get two people on the job then it is even easier.
sailorman
Well-Known Member
new polyester doesnt stick to old/cured polyester thats why repairs to polyester GRP is done with Epoxy
boatbuilder
Well-Known Member
Nonsense, I've been doing it for years. Preperation is the key, degrease, 40 grit grinding disc, degrease again, laminate. Without the same prep epoxy won't work either.
cimo
Well-Known Member
isn't there something you can apply to the prepared poly surface - helps crosslinking between old and new? can't recall at the moment. Any ideas boatbuilder?
late-night-lochin
Well-Known Member
Styrene!
Orrible stuff (and quite dangerous) but effectively starts melting the old polyester GRP.
Then clean it off with acetone before applying more resin.
Don't try and apply large sections overhead, tear CSM into maximum foot square sections or cut tape into foot long sections and apply bit by bit.
Not easy but not imposible either.
boatbuilder
Well-Known Member
Styrene is good, do the tape as I have said and you won't have a problem.
oldsaltoz
Well-Known Member
Applying fibreglass overhead be it epoxy or poly resin need not be a nightmare.
Use latex gloves and 2 on each hand, so if things get sticky you can pull one off and reveal a clean fresh one. They are cheap.
Avoid using brushes, they were never designed to work upside-down. Get a small roller and a paint tray so you can control how much resin is applied, a lot less if using epoxy.
Start by mixing a small quantity of resin and apply overhead with a small roller, do not roll fast or it will flick over you and anything nearby.
Leave this so it can start to tack off; use this time to cut your glass into sections/lengths, strips up to 2 feet patches up to one foot square.
Keep an eye on the resin to ensure it does no form drips because you applied too much, smooth it out if you see any.
After 30 to 45 minutes it should be tacky enough to begin, you can now 'stick' the dry cloth or CSM to the resin and smooth it out with the back of your fingers, do this for the length and width of the wetted area.
Now apply a little more resin with the roller, taking care not to overload the surface.
Next gently roll the area with a consolidating (Grooved) roller and check it is fully wetted out.
Put the kettle on or have a stiff drink and when tacky apply the next layer and so on.
This is not a fast method but will avoid disaster and puddles of resin in places you don't want them.
With a bit more experience you will be able to pre wet the glass and pick it on the back of your fingers and apply without problems, but that's a longer lesson.
Hope this helps.
Avagoodweekend......
.
Use latex gloves and 2 on each hand, so if things get sticky you can pull one off and reveal a clean fresh one. They are cheap.
Avoid using brushes, they were never designed to work upside-down. Get a small roller and a paint tray so you can control how much resin is applied, a lot less if using epoxy.
Start by mixing a small quantity of resin and apply overhead with a small roller, do not roll fast or it will flick over you and anything nearby.
Leave this so it can start to tack off; use this time to cut your glass into sections/lengths, strips up to 2 feet patches up to one foot square.
Keep an eye on the resin to ensure it does no form drips because you applied too much, smooth it out if you see any.
After 30 to 45 minutes it should be tacky enough to begin, you can now 'stick' the dry cloth or CSM to the resin and smooth it out with the back of your fingers, do this for the length and width of the wetted area.
Now apply a little more resin with the roller, taking care not to overload the surface.
Next gently roll the area with a consolidating (Grooved) roller and check it is fully wetted out.
Put the kettle on or have a stiff drink and when tacky apply the next layer and so on.
This is not a fast method but will avoid disaster and puddles of resin in places you don't want them.
With a bit more experience you will be able to pre wet the glass and pick it on the back of your fingers and apply without problems, but that's a longer lesson.
Hope this helps.
Avagoodweekend......
.
sailorman
Well-Known Member
Keith 66
Well-Known Member
Comments saying new polyester wont stick are codswallop, i have spent many years repairing GRP boats & as a previous poster said it is quite possible to get an excellent bond the trick is long feathered edges sanded well with 40 grit. For overhead work you can add thixotopic agent to polyester that makes it stickier.
Working at a catamaran factory once we had an overhead job about a meter square to do where the designer wanted a sheet of kevlar moulded into the deck with a heavy layer of biaxial cloth over it. We said we will have to put the glass on in strips but he insisted we did it in one, with three of us rolling it up it was not going well with a lot of cursing, in the end it just would not stay up & we had a large fibreglass monster sitting in a big lump on the cabin floor, we picked it up in a dustbin bag & put it outside in the yard where it popped & crackled expensively.
Working at a catamaran factory once we had an overhead job about a meter square to do where the designer wanted a sheet of kevlar moulded into the deck with a heavy layer of biaxial cloth over it. We said we will have to put the glass on in strips but he insisted we did it in one, with three of us rolling it up it was not going well with a lot of cursing, in the end it just would not stay up & we had a large fibreglass monster sitting in a big lump on the cabin floor, we picked it up in a dustbin bag & put it outside in the yard where it popped & crackled expensively.
Blueboatman
Well-Known Member
All been said ( and how do you imagine GRP boats were repaired before epoxies came along 25 years ago?). Epoxy is structurally stronger but that is overkill 9 times out of 10.
But I would add, buy a box of disposable gloves and put 2 on each hand, then if you get in a mess, you can easily rip one off, tadaah.
Main thing is to have a thermometer, at least 16dg centigrade on all surfaces,resin, glass cloth etc. So leave a heater on to stabilise the work area before , during and after until cured hard-to-touch.
Don't be afraid, it is not rocket science. Worst case scenario is you grind off the job and do it again until its right.
But I would add, buy a box of disposable gloves and put 2 on each hand, then if you get in a mess, you can easily rip one off, tadaah.
Main thing is to have a thermometer, at least 16dg centigrade on all surfaces,resin, glass cloth etc. So leave a heater on to stabilise the work area before , during and after until cured hard-to-touch.
Don't be afraid, it is not rocket science. Worst case scenario is you grind off the job and do it again until its right.
Quandary
Well-Known Member
Agree, I use epoxy for most jobs these days but polyester is easier in awkward places as you can make it go off much faster if you need to.
oldsaltoz
Well-Known Member
Make that 60 years ago.
The first type of epoxy resin was commercialised by Ciba in 1946. Hempel launched its first epoxy products in the mid-1950s, under the names Tanker Protect ...
www.hempel.com/.../085E68EB4DA01C29C1256EBB0034D1C1
messingaboutinboats
Member
Gravity's naturally going to impair the adhesion as the epoxy will try to drain out of the layup. Personally I'd try working with only at most a couple of layers at a time with a fairly dry mix (say 1.5 fibres to 1 resin by weight) and use a peel ply to aid in holding it all together and provide a good surface for the next layup to go on after that lot's cured. Too much cloth in one go with too much resin content and it'll just flop away, a little at a time and you'll get a good air free bond to the previous surface.
I'm no professional but I've experience working with composites in an amateur sense being involved in sailing Cherubs.
I'm no professional but I've experience working with composites in an amateur sense being involved in sailing Cherubs.
boatbuilder
Well-Known Member
If we have a big overgead job like the sq mtrjob refered to earlier then we vacuum it in position as follows.
prep area and pu on bag tape, lay up lam on plastic, not forgetting breather and bread wrap must go down first ,lift up the whole package and stick it to the bag tape. turn on vacuum . Have cup of tea.
We also use this system when making cradles for boats whilst they are still the right way up.
I the premier yard on the east coast use epoxy then the tat is thier working method, it is niether right or wrong. We use poly on poly boats, vinylester on vin boats , and epoxy on epoxy boats.
prep area and pu on bag tape, lay up lam on plastic, not forgetting breather and bread wrap must go down first ,lift up the whole package and stick it to the bag tape. turn on vacuum . Have cup of tea.
We also use this system when making cradles for boats whilst they are still the right way up.
I the premier yard on the east coast use epoxy then the tat is thier working method, it is niether right or wrong. We use poly on poly boats, vinylester on vin boats , and epoxy on epoxy boats.
