Some Blisters in the epoxy coat - what to do

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Chris
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Some Blisters in the epoxy coat - what to do

Post by Chris »

After finishing the epoxy yesterday I started to eliminate some tears with a paint scraper as recommended at newfound woodworks in the not total cured epoxy. It worked fine, but on some raised tear areas I recognized that I scraped quickly in the glas. I think that happens, because there is some epoxy and/ or air under. (I went not deep in the coat, just scraped of the raised area) I´m talking about 16 or 17 small areas in the size of maybe half an inch. I put on two picture on my homepage which shows the actual situation:


www.natur-im-sucher.com/canoe/bubbles/img6424.jpg and
www.natur-im-sucher.com/canoe/bubbles/img6425.jpg

So - what to do now: It is best to sand these areas and put a little new piece of glas on it or should I simply sand a little bit in depht and fill them up with claer epoxy as they are not very big. surprisingly all that happend on only one side of the boat. I followed the instructions in canoecraft, which tell me to use a very flat angle when sqeezegeeing, but now I think that`s not working for me, because maybe I pressed resin under the coat which brings it to flow.

Thanks in advance - couldn`t think to build a canoe successfully without your help!

Chris
Last edited by Chris on Thu Feb 03, 2005 5:28 pm, edited 1 time in total.
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Todd Bradshaw
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Post by Todd Bradshaw »

The first thing to do is NOTHING - for about three or four days! Maybe I should just shut up and go away, since many of my views seem to go against the 'gods" of strip building and many of the members of this forum, but this is exactly what I have been preaching about for quite a while here. Epoxy takes time to cure and until it does, the fiberglass layer is vulnerable to being bruised or disrupted, which is what has happened here and which is clearly visible in the first photo. In trying to scrape down a drip or two, you have agitated the not-yet-hard fiberglass and most likely deep down inside the laminate where no amount of filling will ever hide it completely. If, on the other hand, you had waited a few days for the resin to harden properly, such a drip could have been scraped or sanded off in a couple of minutes without messing up the fiberglass layer.

Filler coats are a means to an end - not the end itself. The end comes after they have cured properly and been sanded smooth. I simply don't understand all the intense effort spent trying to make your filler coats as smooth as possible when you apply them. No matter how good you are, you still won't have a truly smooth hull without sanding it. If you wait a few days the glass will be pretty hard and able to withstand fairly vigorous sanding where needed. In the mean time, you can dab a little water on the offending areas to see just how clear they will go once the hull is finished and varnished. If acceptable, this can be duplicated permanently with a bit more resin painted on and sanded smooth. If they still show badly when wet, the only way to remove them is to cut or sand the cloth out of those areas and replace it will small patches.
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hoz
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Todd is correct

Post by hoz »

Let it cure...HARD. That may take 3-4 days,or even a week. Once there you can start repairing the problems.

I once saw a canoe that was in it's final stages of resin coating. The thing looked a mess. Runs, drips, humps, ripples. I wondered how in H--L it would ever look OK, let alone good. The builder said he was"letting it cure". After a week or so he sanded the thing up through the numbers until he had a really smooth hull. Varnish brought out the beauty.

He had enough coats of resin on that canoe to be able to do that, without sanding through to the glass. :big grin
someday I'll fly, someday I'll soar
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Glen Smith
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Post by Glen Smith »

Hi Chris, from the photos it looks like the glass was "floating" in those spots instead of being in contact with the wood hull. This could have been caused by improper use of the squeegee as you mention. If there is no epoxy between the fiberglass cloth and the wood hull in those spots, they will weaken the structure.

As Hoz said, the best thing is probably to let it harden a few days. Then you could proceed to "patch" the problem areas with just epoxy or with fiberglass cloth and epoxy.

Let us know how it turns out.
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Chris
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More blisters - going to make an additional coat - right?

Post by Chris »

Hello,

I told you a few days ago about some poblems I had with bringing on the first coat. Yesterday and today 6 - 7 day after to application the epoxy seemed to me ready for sanding. I did the job with a orbital sander with 80 and 120 grid paper. It happens to be that there a more areas where I hit the cloth the before. The reason is resin under the cloth, because all areas where the cloth came through were a little bit higher than the regular surface. So to get a good shape I had to sand them even. I don´t sanded very deep in the cloth I think but I decides that it would be the best to sand a good surface over all the hull an put up an additional epoxy layer to make a fine surface. Just like to knowyour opinion an doing that - I jst started hearting the shop this evening to get a good working temperature tomorrow.

BTW: In the technical information about West System epoxy is stressed to use the exaxt ratio between hardener and resin. I put in a lillte more hardener in, because I did`t recognized that the ration is 3:1 by volume - I did it 3:1 by weight (correct value by weight where 3,5 : 1) - do I have to get any problems of that?

Best regards

Chris
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Glen Smith
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Post by Glen Smith »

The places where you sanded into the glass will most likely show after applying another coat of epoxy but maybe just in the sunlight. One way to improve the appearance is to wet sand those spots starting with 220 grit paper and working up to 400 grit. Clean off the surface and allow to dry properly before applying more epoxy. This is not guaranteed to work but it might help.

Some epoxies are more forgiving than others when the ratio is wrong. I am not sure about the forgiveness of West 105/207 but I have used it and my ratio wasn't always perfect but this has never caused me any problems. However, I cannot say if my ratio was 3.5 : 1 or more or less.
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Erich
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Post by Erich »

Chris.

It looks like floating glass. If the patches are larger than 1 inch I would patch the areas with new glass. It is the easiest way to repair and strengthen the bottom. You may have waited a little too long to squeegy the coat. It was starting to flash because the epoxy was in a larger bubble. Most epoxy is usually good to about 10% over or under the recomended mixture. Happy building.

Regards, Erich
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Chris
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Nice in the shadows - ugly in the sun....

Post by Chris »

Hi Erich & Glen,

thanks a lot for your advice again. I choosed Glens Version because after sanding there are quite many spots visible and the hull had been a rag rug if putting patches all over. The most areas had many spots (more than I expected two days ago), but not very big. So today I made the sanding with 220 and 400 grid wet sanding paper (btw - should I have washed the hull because af the "Aminröte" - don´t know the englsih word for the wax which could develop on the surface when the resin cures?) Than I cleaned it with clear water and a microfiber cloth and let it dry for 1 and a half our.

I put on a addition coat by foam roller which worked well - than I made the test with bright sunlight (yes, we had a sunny day here en Germany :smile ) and the nice in-the-dark-looking-surface looked not so nice anymore grrrrmpf..

So I see now 3 opportuniteis to choose:

1. Wait two weeks, sand-it-all-aways (does that work), and start over agian - expensive and frustrating

2. Make a colored outer hull in Green or red (like Joe Seliga does :eyebrows ) - but why did I build no plastic boat than

3. Maybe I could try not a glossy varnish like the epifanes DD Lack I bought, but a silk-matte varnish (is that the correct term?) - maybe it covers my crimes



best regards :embarassed


Chris
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Glen Smith
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Post by Glen Smith »

Hi Chris, I have not used matte varnish so I don't know if it will hide anything. West 105/207 epoxy does not produce any surface blush "Aminröte" if used under the recommended conditions.

A painted hull can look very good but it would be a shame to hide the wood.

If you want to remove everything and start again, I recommend using a hot-air gun to heat the epoxy and a putty knife to lift it away from the hull. Some people have had good results by heating it and pulling on the cloth with a pair of pliers. Sanding it all off is very dusty and toxic, not the best thing to do. Also, if sanding, you will probably touch the wood in some places and when you reapply new cloth and epoxy, the hull will have sanded spots showing through the epoxy. If you heat it and pull it off, there is less risk of making marks on the wood. Go slow and be careful to not lift away pieces of wood with the cloth.
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Chris
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Post by Chris »

I feared that you would say that ..... :rolling eyes

2 things I like to know in this case:

Have you or one of the others experiences with doing that - what i mean is. Can I espect a really better result - or will I get other problems which are hard to handle...?

If I would make the hot gun method: Would it be better to do it quick during the cuirng time, or is it better to wait 2 weeks or so, maybe do the inside glassing and remove to coat than?

Best wishes

Chris
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hoz
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Post by hoz »

if the spots are on the lower hull/bilge only then I would coat it to the waterline with graphite/cabosil epoxy mix. That will cover the spots and give you a black slippery rock hard finish that doesn't show when the boat is in the water.
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Glen Smith
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Post by Glen Smith »

Do I have experience with this technique? No, I have never done it myself, I have only read about it.

Can you expect a better result or run into other problems? The result will surely be better than what you have now if the job is done properly. You could have other problems if you tear out pieces of wood as you pull off the fiberglass. If you later sand into the wood, it will show when you apply the new fiberglass. If you use too much heat in the same place for too long, you will scorch the wood.

It is not an easy process but I have read about several builders who have done it with good results.

If you decide to sand it off, let it cure for a few weeks. If you use heat, you do not have to wait. In either case, wear a respirator to protect yourself from the dust or the fumes.
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