Gelcoat repairs

[Bav34]

Need help

I've looked at various web sites and they all seem a bit general ... for example ''use this wet and dry ... or that wet and dry'' ... but when do you change?

So.

I've taken the bits I understand and started to repair the 14 chips and scratches caused by someone doing a hit and run on my boat.

I masked up the repairs, applied gelcoat mixed a little 'harder' as it was only 12 degrees today ... then the first bit of confusion.

I put sellotape over 12 of the repairs (two were really small) and this seemed positive as it smoothed out the surface. I wondered at the time how could the gelcoat cure but assumed some sort of internal heat generation caused by the mixing of the hardener.

Four hours later the 2 that had been open to the elements were rock hard but when I pulled off the sellotape there was a very chemically smell and the surface was still tacky.

So, should I have put the sellotape on? If so, how does the repair cure?

I'm going down tomorrow to 'hopefully' find that the repairs have cured.

This moves me into wet and dry territory. The repairs are all proud of the hull by just the masking tape thickness... I'm actually quite pleased with the visual effect but if I start rubbing with say 240 when do i work through to say 1000? How do I stop the 240 affecting the surrounding surface ... or do the subsequent finer grades take care of that? If I use 1000, when do I stop??? Do I need a paste as a final step before polishing?

Incidentally I don't have a mechanical polisher ... just a hard block and a more flexible one.

Final question ... for some unknown reason I have a big tube of Farecla G3regular grade paste compond. Where does this fit in the scheme of things? Somewhere between 240 and 1000 or after 1000 ... or not at all?

As usual ... any help appreciated.

 

[Chris_Robb]

Need help

I've looked at various web sites and they all seem a bit general ... for example ''use this wet and dry ... or that wet and dry'' ... but when do you change?

So.

I've taken the bits I understand and started to repair the 14 chips and scratches caused by someone doing a hit and run on my boat.

I masked up the repairs, applied gelcoat mixed a little 'harder' as it was only 12 degrees today ... then the first bit of confusion.

I put sellotape over 12 of the repairs (two were really small) and this seemed positive as it smoothed out the surface. I wondered at the time how could the gelcoat cure but assumed some sort of internal heat generation caused by the mixing of the hardener.

Four hours later the 2 that had been open to the elements were rock hard but when I pulled off the sellotape there was a very chemically smell and the surface was still tacky.

So, should I have put the sellotape on? If so, how does the repair cure?

I'm going down tomorrow to 'hopefully' find that the repairs have cured.

This moves me into wet and dry territory. The repairs are all proud of the hull by just the masking tape thickness... I'm actually quite pleased with the visual effect but if I start rubbing with say 240 when do i work through to say 1000? How do I stop the 240 affecting the surrounding surface ... or do the subsequent finer grades take care of that? If I use 1000, when do I stop??? Do I need a paste as a final step before polishing?

Incidentally I don't have a mechanical polisher ... just a hard block and a more flexible one.

Final question ... for some unknown reason I have a big tube of Farecla G3regular grade paste compond. Where does this fit in the scheme of things? Somewhere between 240 and 1000 or after 1000 ... or not at all?

As usual ... any help appreciated.

Hi John

Were you at hardway today? Tried to get a PM to you via Innesker to meet up lunch time as I was doing work on the boat.

I am sure someone will come back - certainly from Oz by the time the sun comes up there.

Sorry to hear you were hit as well.

 

[TQA]

Gelcoat will not cure fully in air. You must either apply tape or a coat of PVA after the gelcoat starts to cure.

 

[oldsaltoz]

Hi John

Were you at hardway today? Tried to get a PM to you via Innesker to meet up lunch time as I was doing work on the boat.

I am sure someone will come back - certainly from Oz by the time the sun comes up there.

Sorry to hear you were hit as well.

OK here we go. Normal fibreglass resin has wax in the mix, when you add the catalyst the reaction is kicked off and the wax makes it's way to the surface and helps the resin cure and not leave a tacky finish.

Gel coat is the same resin but has no wax added, only pigment to give it colour. After mixing and matching the required colour the surface must be covered to exclude any air, like the wax would have; so you need to apply a film over the top and tape the edges to ensure no air gets in.

Tip:
When rubbing down before you add anything to the damaged area, try collecting the dust from the old gel coat, mix this with the new gel coat, it will help get the same colour and also help the fade rate later.

After it has cured, use the courser wet and dry paper first to remove the bulk on the material that is above the surrounding levels, then the finer grade to get to the same level, finish off with the polish.

I Hope this helps.

Avagoodweekend......

 

[Bav34]

Thanks for that, but do I have to work my way through the grades of wet and dry or is it 240 to 1000 to polish

 

[oldsaltoz]

Thanks for that, but do I have to work my way through the grades of wet and dry or is it 240 to 1000 to polish

240 then 1000 then polish should be fine. just a bit more control if you use a 500 between the above as it leaves shallower marks for the 1000 to remove.

 

[Bav34]

Brilliant thanks. Just wished I'd left the sellotape on as there'll probably be a soggy goo (sounds like a curry) there tomorrow.

Learning all the time.

 

[saxonpirate]

Just a couple of points....You can actually buy wax to add to your gelcoat from anyone who sells GRP supplies. If you are mixing just a small amount, just a couple of drops is normally enough. It does away with the need to mask it up.

The only reason you mask up is to try and replicate the curing process within a mould, where the gell is applied to the mould and then the CSM and rovings layed up on it. Add a little wax and it'll be fine.

 

[Bav34]

Interesting stuff ... I mixed it on the inside of a tupperware lid ... worked fine. When I was clearing up I picked the lid up, it flexed and the surplus mix detached.

The side against the lid was flat, shiney and dry. I'd be well pleased if I get that result on my boat.

The side exposed to the elements was still tacky.

I really thought it would be the other way round with the 'weather' side curing first.

Bit nervous about tomorrow

 

[saxonpirate]

Yeah....let's hope you have a bit of luck today Bav....

Don't envy you repairing all those small dings. I've done loads of gel repairs over the years, but must admit to hating the pea size ones. By the time the repairs finished the pea size area turns into a 6" diameter with the flattening off. Trouble is, if you try and localise just a small area, there's a danger of creating a dent. Which shows up when polished.

Anyway....hope you succeed today, but if the gel is still tacky I'd get yourself some wax. Might save a lot of frustration in the long run.