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PostPosted: September 21st, 2005, 11:15 pm 
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Joined: July 12th, 2005, 7:46 pm
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Location: Saginaw, Michigan, USA
I started the layup of my Kevlar/Carbon canoe today, however did not finish and had problems. I need the advice of you good folks again.

Some of the problems include: fabric was not wet through in areas, there are bulges and wrinkles, and the underlying mold was damaged by the adhering epoxy when I tried to fix the problems.

Please see the webpage for further detail on the problems I have made for myself. Pay special attention to the last two images.
http://www.microtek-inc.com/canoe/thelayup.htm

I had to leave this step of the project unfinished today (due to frustration and health) with just the first layer of fabric on the mold.

Can these problems be fixed or should I just write off this attempt and start again after fixing the mold? I know any fix will not be pretty, however, I hate to just waste the expensive fabric already used. I have enough of the hybrid fabric left for just over one more layer (as I had planned), it is unfortunately already cut.


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PostPosted: September 22nd, 2005, 1:21 am 
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deleteriousone Sounds like you had yourself quite a day....... :o

Your site finally loaded for me and I was able to give the pic's a look. Also noticed your mention of the temp there... 85 deg's is way hot if you were using the 631 hardener. I took the quote below from Raka's site.......
Quote:
A three oz. mass at 77 degrees F. it has a pot life of less than 12 minutes.
Be even less at 85 degs..... :doh:

Also noticed from the pic's that the sun was hitting the boat. The dark fabric would attract the heat and there were likely "hot" spots on the hull surface, just made matters worse.

If the cloth you applied has hardened epoxy in it, it's a write off. Better to peel it and start over. Not a comforting option but likely the best route.


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PostPosted: September 22nd, 2005, 1:43 am 
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Location: Saginaw, Michigan, USA
Komatiq wrote:
deleteriousone Sounds like you had yourself quite a day....... :o .
Frustrating is the word (disheartening is another apt word)

Quote:
Your site finally loaded for me and I was able to give the pic's a look. .
I changed hosting companies
Quote:
Also noticed your mention of the temp there... 85 deg's is way hot if you were using the 631 hardener..
I agree, however, Larry at Raka recommended that I get the 631 hardener when I told him of the project. I objected wanting plenty of work time and was considering the 350 non-blushing. Being ignorant and assured I should have no problems I relented to the recommendation.
Quote:
. . . just made matters worse.
tell me about it. I did not know the fabric was so dark when I ordered it or would have purchased a different color if not only for the comfort factor when using the boat.

. . . . . edit . . . .
update: The epoxy vender of the epoxy (Raka) stands by use the 631 (fast & hard) hardener even at these temps and even for a novice with epoxy such as myself. He (Larry) does state that I should have help with spreading the epoxy and it should be done in shade (not just overcast). I have no choice in location at this time. :(
As for the bulges Larry says to power sand the off and continue the layup.


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PostPosted: September 25th, 2005, 11:17 am 
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Well, scrapping the project will be an expensive lesson. I would try to rescue it if it didn't cost me much more then the original estimate.

You could sand the ripples down and apply patches of carbon/kevlar to the area.

I think the main problem was the hardener. Hindsight is 20/20 but I have never used a fast set, preferring to go slow for the additonal working time.

For the remaining wet out I'd get my hands on some slow hardener from Raka. You cna mix it with the fast for a medium cure BTW, which would be OK for the subsequent and finish caots. .

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PostPosted: September 25th, 2005, 8:55 pm 
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Location: Saginaw, Michigan, USA
jjoven wrote:
I think the main problem was the hardener. Hindsight is 20/20 but I have never used a fast set, preferring to go slow for the additonal working time.

Thank you for the advice,
The main problem was inexperience. The 631 hardener was recommended by Larry at Raka as a ‘harder hardening and just what you need’. I also gave him the temperature ranges we have been having here. I expressed hesitation about the quickness and informed Larry that I have never worked with any layups.
It was too hot and I mixed a too large a batch of epoxy because I did not take into consideration the volume which would be produced with a 5:1 ratio measuring the hardener first.

Now having worked with small batches (and with lower ambient temps) I am becoming a bit more comfortable with use of the epoxy. I have been trying to fix some of the bulge by cutting the bubble, mixing a small batch of epoxy and holding the bulge down until the epoxy hardens. In this case I wish it would cure much faster than it has been (the temps have dropped and no sunshine).

The result is not great, however, it is for the most part better than the big bulge.
I will post pics on the website when I get my broadband connection back (it has been out for two days and they say they will send a rep in two more).
I have come to the decision that I will try to rescue the first layer of hybrid fabric and live with any imperfections which result or start again and have only one layer of hybrid. I will not be able to put more money into this project but will use the supplies for which I have already paid.
Lessons learned . . . which is why I am posting my mistakes on the website so others can learn from my attempt.


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 Post subject: sandbags
PostPosted: September 30th, 2005, 9:19 am 
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If you want to use sandbags to hold the crease repairs down simply cover the patch with a piece of plastic painters dropcloth before the sandbag. The epoxy will not stick to the plastic and itcan be peeled right off.

That twill hybrid sure is a beautiful fabric.

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......(___|/____)
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PostPosted: September 30th, 2005, 9:46 am 
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Location: Grand Marais, MN
I think Larry was right in recommending the 631. You'll have a stronger boat in the long run with this hardener. Make sure that you wash the blush off of the canoe before you add more layers.

I wouldn't worry too much about the bubbles. It looks like you're doing it right. If you can't get them completely flat, just sand them out and patch a piece of fabric over the resulting hole. At this point, I'd be more worried about the overall finished hull shape instead of a perfect fabric layup.


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PostPosted: September 30th, 2005, 12:36 pm 
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Joined: July 18th, 2001, 7:00 pm
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Location: Mounds View, Minnesota US
Bryan,

Do you have any data for the Raka resins/hardeners? If so, I'd sure like to get it. I've previously compiled a sheet with data but at least back then, Raka didn't publish data on their products. With this said, most of the data on resins I have doesn't show much difference in physical properties between any of them, maybe 10-15% across the range. This includes West, MAS, System 3, Adtech, and a couple others. Note that these are all 2 part, NON heat cured resins.

As for the resin/hardener choice. I personally like the slowest mix I can find (and least viscious) as it takes a bit of effort to wet thin, tight cloth.

Also, I won't wet a canoe with blushing resin/hardener, period, no exceptions.
With all the good non-blushing resins out there there's no point in asking for trouble.

Dan


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PostPosted: September 30th, 2005, 8:10 pm 
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Dan, I haven't run any tests or anything like that, but the 631 hardener is suppose to yield a stronger result than the other hardeners. It's not for clear coating. Personally, I use their 350 non-blushing hardener, but with the 631 our kevlar canoe builder needs to wash off the blush.

I've almost talked myself into building a carbonfiber/ bamboo touring bike frame so any info on a good strong epoxy that you have would be helpful. Otherwise, if I do this (Any good places to buy bamboo in MN?) I'll probably use 631/127 from RAKA.


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 Post subject: slow and fast hardener
PostPosted: October 1st, 2005, 10:23 am 
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I agree that 631 hardener might give a harder overall epoxy, but if it is causing problems what do you think about using a slow hardener for the wet out and then switching to 631 for the fill and finish?

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Solo canoes and single blades, with a sail for those windy days...

...........O
......(___|/____)
.........../


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PostPosted: October 2nd, 2005, 11:04 pm 
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I'm not an engineer, but isn't it the wet-out that gives the lay-up its strength? And the fill coats are basically cosmetic?


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 Post subject: me too
PostPosted: October 3rd, 2005, 7:13 am 
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Good point, would like to hear from someone more knowledgable in laminating.

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Solo canoes and single blades, with a sail for those windy days...

...........O
......(___|/____)
.........../


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PostPosted: October 3rd, 2005, 11:33 am 
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I'm not a composite engineer either, but that is also my understanding too, that the fill coats are just to provide a smooth surface and do little for strength.

And in even more, I believe that one reason for vacumn bagging is to reduce and make "denser" the fabric to resin ratio, with the more glass/reenforcing to resin the stronger. (and of course this also makes it lighter)

Bryan, I sent you offline 2 files of resin and cloth data.

Dan


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PostPosted: October 4th, 2005, 6:44 am 
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Yes, fill coats add little to strength. Vacuum bagging does improve the strength to weight ratio but the down side is that the loss in thickness can reduce ridgidity. You have to balance all your objectives.

We often hear someone say such-and-such is stronger but we don't know if they mean stronger in tension, compression, impact, or flexural or whatever.

For example, which is stronger Polyethylene or a carbopn fiber laminate? Depending on what you want, you can get a different answer. The racing paddler who wnats a stiff light boat will say carbon fiber. The whitewater paddler who wants something to resist those rocks that keep jumping up at you would say polyethylene.

I think most people get too hung up on strength issues. Most canoes are more than strong enough just because the builders want the stiff.

The home builder rarely calculates the properties his boat will need. As a result he just does the best he can based on experience (his or someone else's) and that isn't a bad thing to do (some of the time). :D

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