Trying to reno a really old surf / wide board for daughter to use for first water starts (floaty/ wide/ easy) - and give my eldest practise learning to glass and clean up - so he can fix his own surf board dings

Background...
Mostly I have worked with epoxy fixing nipper paddle boards.
So not enough know-how on what goes wrong with polyester resins..

I sanded off - cleaned with acetone - and decided to put a coat of just resin on to get a regular base. So mixed up 1:100 catalyst to resin as about 27 degrees when I did it - painted the mix on - the left over went off great - it set in the pot - rock solid - but the stuff on the board is sticky and about the same as when it went on (24 hrs later!!!) - I have tried heating with hair dryer (Need to confess to the boss later) - still sticky - Does this mean it is an epoxy surf board??
So what to do, & how can I side step this ____ waste of time for round 2??
1) Clean it all off?
2) try a thinned down mix of catalyst and paint that on to try and cure the coat?
3) Sticky it in the sun (when it pops out - raining / cloudy alot) and let it cure?
4) A better plan - (apart from the tip!!)

Needless to say the eldest is really impressed so far
So give me a fix If U can

Thanks

AP

No, the pot went off as the heat generated helped it cure. Anything goes off faster in the pot and if there is insufficient hardener it can go off in the pot but take a year to go off when applied thinly.

Go to 2:100 for that temp

And the acetone does not "affect" fibreglass it just is a solvent for the un-set product.
If you clean it with acetone, it all evaporates off long before you have mixed up resin and appied it.

Mark _australia said...

No, the pot went off as the heat generated helped it cure. Anything goes off faster in the pot and if there is insufficient hardener it can go off in the pot but take a year to go off when applied thinly.

Go to 2:100 for that temp

And the acetone does not "affect" fibreglass it just is a solvent for the un-set product.
If you clean it with acetone, it all evaporates off long before you have mixed up resin and appied it.

what he said^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Agree with previous, but there's a couple of other factors.
Back in the old surf shop days, we'd leave the brushes sitting in acetone, just give them a shake out before using, wiping the board with it first won't have any effect unless it's still really wet when the resin goes on.
Unlike epoxy polyester is very sensitive to moisture/humidity and air!

Laminating resin doesn't set on it's outside skin, just about always remains tacky.
This allows a chemical bond with the next layer.

General purpose/filler/finishing resin has a small quantity of wax added that floats to the surface and prevents contact with the air. This allows the resin to set hard right up to the surface.
If you paint a very thin layer on, there's not enough depth to allow enough wax to float to the surface, and it will not set.
I'd try a 2 to 3% mix and paint it on reasonably thick.
But be careful about upping the catalyst if doing a bigger job. Nothing worse than having the resin go off before you've finished. (temp is also a big factor)

Also be aware catalyst will absorb moisture over time and become much less efficacious.

Mark _australia said...

>>>, just use epoxy for repairs it is easier and always works. Polyester is a pain in the butt

AMEN!!!!!!

I refuse to use it now, it's epoxy or nothing.
And too bad if you want a nice clear finish, there's too much carbon dust around for that.

How sticky is it? Is it hard but sticky or just tacky? Did you use laminating resin or filler?

If you used Laminating resin it will stay tacky until you sand it.

Epoxy is stronger but far harder to use IMO. Most manufacturers will use Polyester filler coats on Epoxy boards for this reason.

Mark _australia said...

and all in all, even if the board is a polyester one, just use epoxy for repairs it is easier and always works. Polyester is a pain in the butt

so could I use 5 minute araldite then?

AquaPlow said...

>>>>>>

I went with the polyester resin as there are a number places the foam core is visible and do not want to 'melt' it with epoxy.>>>>>>>
AP

You're back to front here, epoxy won't melt anything unless you've thinned it with a solvent.

It's polyester that does the melting!!!!
Hope the exposed foam is urethane not styrene!

decrepit said...

AquaPlow said...

>>>>>>

I went with the polyester resin as there are a number places the foam core is visible and do not want to 'melt' it with epoxy.>>>>>>>
AP

You're back to front here, epoxy won't melt anything unless you've thinned it with a solvent.

It's polyester that does the melting!!!!
Hope the exposed foam is urethane not styrene!

Ahhhh - Thx 4 That.
Have done a thinner melt out (epoxy)
Have done a 'doohh - Homer style' Q-cell melt-down - it looked great on the top - out-side - but got bloody hot inside - so the guts of the repair sank thru to the glass on the bottom of the nipper board - about 40 mms!! (epoxy again)

Had not questioned what melted what - no melt down on surf board (youngster would have demanded pay for training!!) - infact surf board back in the sun to hopefully cure the rest.

With polyester, still not sure what sort of lay-up time I have with a 1% mix in say 25-28C - I know I had 8+ minutes - I was distracted by the owner of the hair dryer - BBQ duties - when I went back - pot set - board as above.

On an alternate note,
If you are feeling really lazy and do not need to hold too much of a shape then Solar-rez is good - It is an epoxy resin with a UV curing agent, and chop, mica, and probably some other goodies in it. Basically do a clean up - light sand for adhesion - get the cling film setup on one-side - squeeze on the Solar-rez pull the film over and smooth (use tape to hold in place) then walk out in the sun hold your breath - 30 seconds or so and you are done. You can mould shapes etc but it is fiddly and U must allow the UV to get to the resin for it to set. That is where I started (and the youngster is using up my supply!!) and have graduated to glassing up for better result and bigger fixes.

I have heard you can buy UV catalyst for polyester but someone else would know more about benefits / problems.

The only benefit of polyester that I can think of so far is price, a 1/3rd or less.

Thx again AP

AquaPlow said...
<<<<<
With polyester, still not sure what sort of lay-up time I have with a 1% mix in say 25-28C - I know I had 8+ minutes - <<<<<<<
The only benefit of polyester that I can think of so far is price, a 1/3rd or less.

a 1% mix is fairly standard, I used to be able to glass a board with that. But you have to pour almost all the resin onto the board and spread it quick, it's going to go off too soon in the pot.
Now how long did it take me to glass a board? At least 10min I guess, probably 15 to 20. And I don't think I'd have tried in 28deg.

Polyester is also harder, but more brittle.
So if you do an equivalent lay up with epoxy, it won't fracture as readily as polyester but it will dent more.

AquaPlow said...

G
CMC - polyester filler?? - sounds great - I have some car bog but it is a bit heavy - I normally use 'Q' cell mix in epoxy resin and planned to do the same with polyester resin.

The Polyester filler I was referring to was Laminating resin with Wax in Styrene mixed into it to make it go off not being sticky and better to sand.

In surfboard production you laminate with Laminating and fill the cloth with Filler resin as above. Lam will feel tacky until sanded and gum sandpaper along the way. Filler is very sandable and much better to mix with Q-Cell for repairs etc.

Personally I think Epoxy lams with Polyester filler coats are the way to go even on PU blanks but that's just me.......