Gelcoat and wax

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Graham_Wright

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www.mastaclimba.com
I am gelcoating a fairing under the hull and, conscious that gelcoat needs sealing from the air to cure, have added the recommended percentage of wax (in styrene). It has been reluctant/refused to cure.

I am wondering if, when wax "floats" to the surface it floats out or down.

In other words is it a gravity based process or is it escaping the resin.

In desperation, I used clingfilm but it left a rough old surface.

Any help appreciated.
 
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Wax in styrene is used in flowcoating, which sound like it is what you are attempting. I don't have personal experience of this, although there have been a number of articles and references to the process over the years in PBO. Usually it is a process similar to painting and the wax goes to the surface, needing to be washed off if further coats are to be applied. It certainly works on any orientation of surface. Perhaps in your application you may have exceed the thickness of coating in which the wax can migrate successfully to the surface?

Rob.
 
I have just gel coated my coachroof and I didn't need to seal from the air. The gel was painted on in 4 coats with the final one being laid off by using a wide flat blade. The finish obtained from sanding in stages down to 1200 grit is fantastic.
 
Graham_Wright said:
I am gelcoating a fairing under the hull and, conscious that gelcoat needs sealing from the air to cure, have added the recommended percentage of wax (in styrene). It has been reluctant/refused to cure.

I am wondering if, when wax "floats" to the surface it floats out or down.

In other words is it a gravity based process or is it escaping the resin.

In desperation, I used clingfilm but it left a rough old surface.

Any help appreciated.
Click to expand...

Gelcoat doesn't need sealing from air to cure but, it can cure with a tacky surface which usually washes off with acetone. Adding wax to the mix stops the stickyness but needs to be added in very small quantities and can slow curing time.
 
Yoda's freshly gelcoated coachroof

yoda said:
I have just gel coated my coachroof and I didn't need to seal from the air. The gel was painted on in 4 coats with the final one being laid off by using a wide flat blade. The finish obtained from sanding in stages down to 1200 grit is fantastic.
Click to expand...

At the risk of hijacking - Yoda, do you have any before/during/after photos? I'm thinking of doing the same on my boat, I'd be interested to see how you got on.
If you can add any detail (especially on laying off the final coat) I'm sure it would benefit a few readers...
 
Sorry but failed to take photos during the process! Each coat was applied as soon as possible after the last was cured and in a good day we could easily get 4 coats of gel on. It was applied with a brush and laid off as best you can. The final coat was applied by brush and then laid off with a very flexible steel spreader about 4 inches wide. The last coat leaves little extra gel but seems to fill the grooves that seem to appear from the repeated application of gel. As you lay it off the spreader is kept cleen and if gell spill off the end leaving a significant ridge it is just left. I know that sounds mad but the ridges are easy to sand off, indents are very difficult to deal with as you end up removing loads of gel to make it smooth. Once cured you start the sanding process which we did first with something like 120 and 240 grit on an orbital sander taking great care to keep it moving, longboarding is much better but over large areas is very time consuming. we then longboarded the next 2 grades with dry paper and then wet and dried down to 1200 grit by hand with a block of wood. Once done a final polish with 3m (medium grit) using a buffing machine brought it up to a beautiful finish. 4 days in total to complete the job. It really is about having the patience to do it right. There are no good shortcuts! Certain things make life much better, we used a substance called MW (I have no idea what it is so don't ask) which makes the gel flow better for application. Gay abandon on the disposable gloves! Trade isopropanol wipes make cleaning up much easier. Words of warning, colour matching is almost impossible it just isn't worth it. Brushes need to be both disposable and decent so as to not loose hairs - get them from a GRP trade supplier. Buy good quality abrasive paper it lasts much longer. If you get a dimple don't sand it out, have the patience to fill with more gel an repeat the sanding. Hope all that helps. Have a go where you can put up with the results and see how you get on.

Yoda
 
Gelcoat needs wax or sealing from the air to cure.

Flowcoat is much the same as gelcoat but has the required amount of wax mixed in. You can apply it like a paint.

Just bear in mind that when adding the catalyst you bust take into account the amount of solids in the mix, some ore over 50% so you mix about half the amount of catalyst that you would to standard resin.

For a smooth finish I apply with a small (80mm) roller and tip off with a foam brush.

Use small batches in wide shallow containers and mix often, apply wet on tacky for more depth if required.

Hope this helps.

Good luck.:)
 
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