Doc's Place

Ding Repair-

"bjamin" wrote:>
I've seen and heard the terms: hot batch and cold batch.>
Can someone define them for me. Does hot batch actually mean I heat up the
resin/catalyst on the stove or is a hot batch referring to adding catalyst
to the resin? Thanks. I'm working on some delam problems.
Bjamin

Okay, benjamin, let's see what we can do here;

First of all, a batch of resin needs catalyst to make it harden. A slow batch uses some catalyst, a hot batch uses a lot. Due to this the resin will either go off fast or slow.

Heating resin and catalyst on your stove, well, I would be curious to see what would happen. I would prefer to be curious from a considerable distance-say 500 yards away, as it would probably make a loud noise and maybe a cute little fireball.

So, why does anybody use a slow batch and not hot batches all the time? To begin with, resin goes off in a catalytic reaction. The catalyst helps things happen, but given enough time, the stuff will go off by itself.

The more catalyst, as I said before, the faster it happens.

Now, there are other things that make the resin go off faster. Heat, sunlight (UV) dry air and so forth. Cold working conditions,shade and dampness slow things down. If there is a thick coat of resin, or a deep, wide hole you are patching, it goes off quicker too, and it can get warm from the chemical reaction going on. Which makes the thing go faster still, which makes more heat, which....you see where this is going.

Neat, you say, but so what? Okay, think of the liquid resin as a whole lot of short pieces of chain. If you link them together, the stuff hardens.

A hot, fast setting batch will only get a chance to make a few connections, tie together a few pieces of the chain. It is kinda weak compared to the long chains that are made up in a slow batch. Hot batches tend to crack. They are weaker in any case.

And of course, hot batches are literally hot. The chemical reaction happens fast and ugly things can happen. I once watched a board catch on fire. Not one of my boards, fortunately. Saw another that was kinda strange-all the foam had burned, leaving a black soot inside this hollow fiberglass shell.
Anyhow, that's enough for now.
I have to sand some dings. Always a thrill.

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bjamin wrote:
Doc;
Thanks for the explaination. I appreciate the response. I will not heat on the stove! :)>
So, I want a cold batch (less catalyst to resin ratio) to make as many connections as possible.

Exactly. Another thing I do when fixing delams is to thin the resin somewhat with acetone to the thickness/viscocity of, oh, half and half cream. This not only penetrates to the very edges of the delam, it also penetrates into the foam somewhat and winds up as a better, longerlasting job.

You will want to have a kind of resevoir for the resin so that it will continue to flow in as it penetrates, much like the sort of thing they use in sand-casting metals, if you are familiar with that. I have used a cone of wax paper, held in place with masking tape, to hold resin and to let it flow into the delam as the foam and such absorb it. This keeps the delam full of resin- no air pockets.

The acetone seems to retard drying a bit as well. So, I play that by ear. When I do something like you are describing there are a couple of other steps as well.

Once the resin has gone off, I then sand lightly over the whole thing and then rinse it a bit with more acetone. This does several things; cleans up the area, removes any residual wax and chemically etches the existing glass a bit. This helps for the next step- glassing over the whole thing and a bit past the edges with fairly heavy (8-10 oz) cloth. I think this helps to prevent the delams from spreading or reoccuring.

> I'm working on a delam 18" x 4". Bought some syringes. Have a few holes drilled. Once the board is dry, I'll mix that cold batch.

Do you sand by hand or with a machine like an orbital sander?

Oh, it depends.

I will preface this by admitting that I make a fair amount of my summer pocket money fixing dings, so my setup is kinda industrial strength. My sander collection goes from a little triangular pad detail sander all the way to a 13 amp Milwaukee disc grinder. The thing is, I have to get things sanded pretty thoroughly in a short time, so I can do the job at a fair price.

But if I was going to use one sander, I'd pick one of the Porter Cable random orbit, variable speed types. I have, and like, the Model 7335. Great little tool. With a little practice, it will work for any sanding job in ding repair.

I have noticed the real difference between a good ding repair and a bad one is in the sanding. Nobody hand-sands enough. I use power sanders for everything but the very last step. I then give the ding a quick wet sanding with several types of paper, all the way down to 600 grit. This leaves a pretty good looking surface, and it can be done in a minute or two.

> wishing ya some clean lines your way,
Bjamin

~~~~Thanks. We can use them-Doc

Todd Clemetson wrote: I just bought my first board yesterday. After waxing it this evening, I set it up next to the door in my living room. To make a long story short, my dog's curiousity got the best of him, and he ended up knocking the board over into a table.

Been there, done that. In my case it was my first board and one of my little brothers.

Lesson 1: Boards are relatively fragile out of the water. Think of a good place to keep it where this won't happen again. You are not alone, though. I would guess that 90% of the dings I fix are what I call 'garage dings'. Taking them off the car or out of the house is kinda haardous. Buy a good, padded board bag. Trust me on this one.

> > After examining the board closely, I noticed that the fiber glass on the > left rail had been pushed into the foam of the board and created a 1 x 1 > centimeter hole. I just started surfing a month ago and have no idea if > this is fixable or if I can even ride on it before it is fixed.

Okay, you can fix just about any board, any ding if you really want to.

This is a small, minor ding.

Duct tape it. You will be able to surf it then. DO NOT put any wax in the ding. The wax will only make life miserable for whoever winds up fixing it. You see, the resin or whatever will not stick unless you remove every trace of wax. This usually means cutting out the waxed areas of foam and such. I use a saw. A little, minor ding becomes a crater.

I generally charge $20 extra if the ding was waxed-for being STOOPID.

Another reply suggested buying a ding kit. Good idea. The guy at the surf shop will know how to fix the board as well. It may be cheaper to have the board fixed by a pro. It will come out better too, as the pro has more experience, better materials and better tools.

I know I am gonna get flamed a bit on this, but Solar Rez sucks. I hate the stuff and I refuse to use it. It's a second rate temporary repair at best.

What it is is a UV resin with some fiberglass fibers in there to hold it together to keep it from cracking right away. Sort of like what boatbuilders refer to a 'kitty hair' . In any event, that makes it very tough to get it all into the little cracks and crevices in a ding...which means air bubbles and eventually leaks and delams.   Very bad.

When I am confronted with a solarez ding that somebody wants to have redone, I charge extra above and beyond my usual rates for ripping it out and redoing the gaping crater that results. Takes more labor and materials...no fun at all. And it _has_ to be ripped out. Air bubble, trapped, get warm and expand and nasty stuff happens.   For temporary repairs, I use duct tape instead. Won't hold a fin or stick a board back together, but neither will solarez, no matter _what_ anyone may claim. It is easier to get it off later.

> Anyone know what effects will this have on the board? Will water seep in > through the crack and make the board less buoyant?

Bouyancy is the least of your worries. The water, along with sunlight, has several effects on the foam onside the board, none of them good. You should fix it soon.

Should I kill the dog?

Naah.When winter comes, bring him to the beach with you. A nice, warm dog is great to have around after a cold session.

>> Thanks>> Todd>>

.You're welcome
Doc

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