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Just laid 3 coats of epoxy to the deck of my miracle sailing dinghy.
Its taking a while to cure so i recheck the label.
It says 2 parts epoxy for 1 part hardener.
Ive been mixing 3 to 1!!!!!!!!!!!!
Its been 4 days, not v warm ones, and the glassing ive done seems to have set hard. Its not tacky.
The decks when sanding have been a bit smeary, even after 3 days.
Been sanding a fair bit because it was sagging and bobbling.
Now i know why.
Am i trully stuffed or will it fully cure?
The deck needs to be waterproof but structurally wont be taking a load.
The reinforcing of the transom using epoxy, filler and tape seems to have hardened nicely but will it fall apart over the season?
MEK doesn't have quite the flash off of acetone and is a stronger solvent. Both of which are desirable properties in this usage. Breathing the vapours or significant and prolonged skin contact is not desirable with either. But then I've used MEK as an emergency lighter fluid before so why would you trust me? (g) (and don't use acetone for that or you'll light your whole face) Work, as always with solvents, in a well ventilated space. MEK also cleans up your still wet epoxy brushes quite well also. It's the primary ingredient in PVC pipe primer and a derivative is the catalyst for gelcoat resin.
If you spill it on your boat you'd best be wiping it up rather soon as the stuff will dissolve about any plastic if left to rest.
"I can confirm you can use Epoxy with CSM (chopped strand mat) but it has
to be the powder bound version. This is sold by CFS and is on our online
catalogue if you would like to take a look"
The prompt reply was nice but he hasnt really told me if the 300gm sq/m is "powder bound". Ive been all over the online catalogue and if its there its not obvious.
That's why I like going to a marine store to grab a salesperson (ironic isn't it?) and shoot questions... What to use, where to use, how to use, where is she from, is she single...Hold on! That's not related to the thread... Anyways, ask the person until you've got the answers you need to start with...
Thank God I'm not alone
With proper force and right lifting you may be able to take the hole thing out on a hot summer day... That's what I did afterall... Then mek'ed it to clean, 120 then a 220 sanding to begin a fresh start with proper technique...
Good luck...
PS: The chopped fg is easier to work around the curves and etc... Mat on the other hand really hard and I'd say use it between successive layers of chopped fg to add strenght to needed points of repair...
If you do take this boat out, please wear a pfd. I personally would ripe it out. I ripped out a keel repair done using mat and epoxy. I replaced it with 4 layers of 6.5 oz e cloth wetting it out fully with epoxy. I also used 12 inch wide 9 oz fiberglass "tape". I then put 4 layers of epoxy over the entire bottom of the hull.
I'd agree with Free... wear a PFD and file a float plan before going out in it. I would highly recommend ripping out the CSM, since the tensile strength of the sizing is relatively low, and that is effectively the weakest link in the repairs you've made, since the epoxy is bonding to the sizing—not the glass fibers within the sizing.
How much force do you generate swinging even a heavy screwdriver. Compare that to the force that is applied when the boat comes down off a wave with two people in it.... one is significantly greater than the other, don't you agree??
It sucks so bad to take apart work you've done I totally feel for you. If you do end up taking the layers off you can really save yourself some time by using a grinder instead of a belt sander. 40 grit and 10,000 rpm makes quick work of taking down glass. Good luck.
Okay, so this explains why i had one hell of a time making CSM take the shape of the rail on my rowing dink. I did make it work, but it was tough. I covered that repair with fibreglass cloth and epoxy and it seems solid. I also did a repair on the bottom of the bow using a layer of CSM and cloth. Its also solid, i think.
Its not chemically bonded but it is structurally bonded.
All that hard epoxy permeating the matt and well keyed to the wood.
Ive ordered some Biaxial Tape 150 mm 450gsm tape to add another layer.
I have zero credibility in this thread since I thought mat and epoxy was fine, but I think I understand what stu means. When I used them together, I did fill the void with something hard. I did get the mat wet with epoxy; there weren't bubbles or soft spots. But according to the info I read the other day, the mat was supposed to unbind and have the fibers mix so that they would bond like one unit and I guess that didn't happen.
But stu, think about this (and try it if you're really bored) - if you soak an old sock in thickened epoxy and let it dry I bet you can whack it pretty hard with that screwdriver and it will feel pretty solid. But even the crazy cheapskate doesn't build or repair boats with old socks...
I wouldn't call it a surface coating. It's over, under, around and between the bunches of fibers. The mat gets soaking wet with epoxy. I know because I have done it. That's why I thought it worked. I soaked the mat then put it in the void and there was epoxy all through it. But I didn't know that the mat should have started pretty much disintegrating. But this is from what I read the other day and I could just be digging my hole deeper.
The epoxy isn't adhering to the bundles of fibers...it is adhering to the sizing that is holding the bundles of fibers together... big difference. It is basically a surface coating and the major difference is simple. In a true laminate, like using polyester resin and CSM-the fibers can no longer move relative to one another as they are encased and adhered to by the surrounding resin. In the case of using CSM and epoxy, the epoxy is adhering to the binder coating, but under high stress loading the fibers may shear their physical connection to the binding sizing, which isn't really all that strong as a material or as an adhesive, and the fibers will then be able to move relative to the material surrounding them. Which do you think is stronger???
I was never argueing it was stronger.
I know i probably come across as someone who is just argueing until he gets the answer he wants,
but ive been see sawing back and forth on this one between posts.
The phrase "the fibers may shear their physical connection to the binding" is quite alarming.
But if you look at the pics you can see ive only done the inside of the hull so far. If that was it, i think you'd be right. It might be alright, but you dont want to worry about it dropping of a wave or bumping on a beach/trailor.
Im gonna wait for the approriate material arrives to do the outside.
I guess I just dont see the the csm epoxy coming apart, especially as the edges and the right angle to the bulkhead are taped with the correct material. And what damage might i do ripping it all out?
With Biaxial Tape 150 mm 430gsm on the outside of the hull it will be far stronger than the surounding wood.
Thanks for all the posts. Although im being stubborn and arguementative i do appreciate them.
a year on and its still holding together.
To be fair, its been wintering under a cover for a lot of that time, but ive had a few hard trips out.
This was always going to be a bit of a messy learning curve project. The boat was almost dead when i got her and i learned a lot about bot epoxy and polyester along the way.
I got away with it because the weak epoxy csm mix repair on the inside of the hull was not part of the structural strength of the boat. That was achieved using the correctly mixed matt and epoxy on the outside of the hull.
The helpful advice i have received warning me not to believe in the strength of my bodged inside repair is correct. How wise i sound now after the fact.
As a general point I believe anyone reading this post should and wondering what the hell were all talking about should not be deterred. There is no substitute for getting your hands dirty and having a go. Worst case scenario is the boat breaks under me and i have to swim to shore. Ill bet its not gonna happen and even if it did its a great story for sailnet (as long as im wearing a life jacket). Im safety conscious, but i also believe in getting on and learning! This balance is every individuals personal choice.
It won't cure properly!!! I did the exact same thing. I was fixing a hole in my hand-me-down dinghy and mixed it wrong. That was a month ago. Its still gooey. In fact, it rained and the stuff ran down the side of the dinghy. Best to scrape it off and do it properly!
Teresa Sailing, Simplicity, and the Pursuit of Happiness
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