Help, need a fibreglass patch

**Hanne** · 16th June 2007, 11:37

Has anybody a small patch of fibreglass and some resin, need to put a patch on the back of a panel which has a crack to keep it strong.
Just a small patch (maybe 3x3 inches), so I didn't really think it was worth going to a shop for.
Has anybody got any spare bits left over?

Thanks,
Hanne

**Drum** · 16th June 2007, 14:44

I've got the fabric and resin+hardener, but cant send the chemicals in the post. If someone in Auckland has got the resin I can send you the fabric patch.

**slopster** · 16th June 2007, 18:09

Fabric costs fuck all like $5 for a square metre at the boat shops. I think resin is about $20-30 for a small tin

**JeremyW** · 16th June 2007, 18:59

We do a bit of carbon and fibreglass. Give me a call tueaday and we can sort something out.

Jeremy 0272957769

**Squiggles** · 16th June 2007, 22:11

found some in the shed that came with a surfboard the olds bought, hopefully we patched it right, curing now

thanks anyway guys, we'll be in touch if it did go wrong!

**Hanne** · 21st June 2007, 20:29

Thanks for the replies guys,
Still wasn't dry after 5 nights in a reasonably waarm shed os we have pulled off what we did (peeled, really) and I think I will start all over again, probably with some fresh resin (eould the age of the chemicals make a difference?)
(How long should it generally take for fibreglassing ot dry? Not 5 days, right??)
Thanks!
hanne

**imdying** · 22nd June 2007, 08:59

Needs to be about 20 degree minimum for best results, the colder it is, the longer to cure. Ratio of hardener to resin is pretty imortant, you can't just add more hardener to speed it up.

**Drum** · 22nd June 2007, 10:45

Last time I did some, it set pretty hard overnight.

Should be an expiry date on the container too.

**Hanne** · 23rd June 2007, 12:03

Yes, the chemicals were pretty old! We measured out the ratios according to the label, but it didn't set properly (15-20 degrees in the back shed, heaps of warmth from all the fish tank pumps!)

**imdying** · 23rd June 2007, 15:49

Bummer, have to try some fresh resin then.

**IamCornholio** · 29th June 2007, 13:13

Originally Posted by Hanne

Thanks for the replies guys,
Still wasn't dry after 5 nights in a reasonably waarm shed os we have pulled off what we did (peeled, really) and I think I will start all over again, probably with some fresh resin (eould the age of the chemicals make a difference?)
(How long should it generally take for fibreglassing ot dry? Not 5 days, right??)
Thanks!
hanne

I would think that the age of the chemicals would not matter as much as the ratio of hardener to resin and the temperature you are applying it under...

Fiberglass resin (polyester resin) is basically the same as what's in Bondo. In pure form it is like water, but usually the stuff we see is like syrup because it is thickened to make it easier to handle. The same basic ingredient (MEK peroxide) is used as a catalyst in Bondo and fiberglass resin. Mixing the correct ratio of liquid hardener to liquid resin is difficult and you need practice and experience. Temperature is extremely important. Below 64 degrees Fahrenheit the resin won't cure properly with the correct ratio of hardener. You can add a little extra hardener but too much and it cures unevenly and can trap gasses and styrene in the part or crystallize the resin and make it brittle. Over 95 degrees Fahrenheit it cures real fast and thicker areas can easily cure too hot and crystallize. It starts crystallizing over 140 degrees Fahrenheit. It's best if you can work between 75 and 85 degrees Fahrenheit (the temperature of the mold or part), and maintain some air flow and the correct hardener ratio, for a nice slow even cure.

The hardener MEK peroxide is a catalyst that produces heat in the resin. It needs to be at 64 degrees Fahrenheit minimum to cure, and the best is between 72 and 80 degrees Fahrenheit. At times I will use heat lamps to help 'speed' things up for me...

The temperature is directly proportional to the amount of hardener and it just takes time to get it dialed-in. Also always mix the batch as thoroughly as possible...

Different companies thicken their resin in different ratios, which proportionately affects the hardener ratio. It takes years of experience and knowledge to get real good at this, and I tend to screw up lot of parts when I get in a hurry and do not use the correct amount...

Hope this helped you out some Hanne, I was trying...

IamCornholio (Lord of the Harvest - Master of the Worm)

**Hanne** · 3rd July 2007, 10:34

Thanks for that IamCornholio, obviously there are a lot of things to balance up!
(I did do chemistry at High School but actually managed to set the floor of the science lab on fire with a flaming marshmallow.... ><)

**IamCornholio** · 4th July 2007, 23:29

Originally Posted by Hanne

Thanks for that IamCornholio, obviously there are a lot of things to balance up!
(I did do chemistry at High School but actually managed to set the floor of the science lab on fire with a flaming marshmallow.... ><)

I had a couple of cracks in our lower cowl and used some fiberglass cloth and resin to fix them just like you described in the beginning of your thread...

Also like you, I followed the directions on the can for mixing the hardener and resin and it was NOT working for me. (In my case the stuff was getting hard in minutes using the 'Bondo' brand suggested 12 drops of hardener to 1 ounce of resin)

I saved myself from wasting a bunch of resin by getting the 'mix' worked out by testing one ounce at a time until I got it right for our temp and the speed that I wanted to be able to work at. I ended up at about 8 or 9 drops per ounce BTW...

I bought an aftermarket pipe for our bike that 'needed' to come through the side of the lower cowl a bit because it was so big and I HAD to make the plastic strong enough to cut on it without it cracking to bits. 5 thin layers of fiberglass cloth did the trick for me and our stock plastics are now 'bulletproof' and I am able to cut and drill all the holes in them I want with no worries.

Glad some of this stuff helped you out Hanne. I appreciate you guys having me here at KB. Glad to be a member for sure friend!

IamCornholio

**lordandrevv** · 25th July 2007, 11:46

the age of the chemicals does matter, but the ratio of hardner to resin is more important. The recomended ration is 1.5 - 3% depending on temperature, the normal is about 2%. And yes heaters do reduce the curing time, however you don't want the reaction to happen to quickly as the resin will warm up to much and can crack and ruin the whole job...thats why its important to not apply to many layers at a time...