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  Topic Review (Newest First)
04-21-2009 11:10 PM
LittleFlower 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!
Sailing, Simplicity, and the Pursuit of Happiness
04-16-2009 11:38 AM
It didnt fall apart

For those that might still care...

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.
06-27-2008 01:42 PM
stu9000 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.
06-26-2008 09:57 PM
sailingdog The epoxy isn't adhering to the bundles of 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???
06-26-2008 09:02 PM
Originally Posted by Freesail99 View Post
I understand what Stu means. I repeat, All you have is a surface coating of epoxy over the mat. It will feel hard but it will not have any strength.
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.
06-26-2008 05:21 PM
Freesail99 I understand what Stu means. I repeat, All you have is a surface coating of epoxy over the mat. It will feel hard but it will not have any strength.
06-26-2008 03:33 PM
arbarnhart 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...
06-26-2008 02:51 PM
Freesail99 Epoxy CAN NOT structurally bond to mat, and that is the point, we been trying to make. All you have is a surface coating of epoxy over the mat.
06-26-2008 02:42 PM
stu9000 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.
06-25-2008 10:09 PM
SVDistantStar 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.
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