what goes over fibreglass

[la Huerta]

just wondering when say for instance building a stitch and clue boat, once the boat is almost complete and the last layer of fibreglass has gone on , what would be the next step...dos'nt the fibreglass leave a prickly crapy surface, i would think that some sort of filler needs to go on and sanded to creat a nice smooth surface...could someone explain what is done...

thanks heaps...

[derekcohen]

What type of resin are you using - epoxy or polyester?

What weight glass cloth have you used, and how did you apply the resin (just wetted through verses painted on in thick puddles)?

Have you used a finishing coat?

And, if so, have you sanded back?

Have you considered a gelcoat finish, or are you going to paint?

Too many questions unanswered to give a simple suggestion.

Regards from Perth

Derek

[la Huerta]

don't get so far ahead, i'm just trying to find out what is involved, anyway say it was poly...and lets go from there...

[Daddles]

What goes over fibreglass?
A bloody big truck :D

Sorry.
Wooden boat type fetish :D

Richard

[la Huerta]

wooden v fibreglass 'mithbusted' - Adam Savage on behalf of daddles

[la Huerta]

now lets get serious...after fibreglassing (with poly) what would be done next to get to the stage of painting, filler or putty, then sand till smooth ? this is just my guess ???...

[derekcohen]

la Huerta

Use epoxy resin instead - have better flex capability and more durable. You can use a thicker layer on the cloth to fill in and smooth over the surface, then sand back. Not too thick as it is not strong on its own. Remember, resin will not "stick" to a smooth surface, so always scuff it up to "key" in a coat.

If you were building from the outside-in, I'd start with the formwork, spray on a release agent, then coat with a gelcoat, then add the fibreglass and resin, building up the thickness you need.

Don't try and combine different materials, such as epoxy and polyester, or a thick layer of car body filler over resin (a little used as filler is OK), as this will eventually come apart.

Regards from Perth

Derek

[la Huerta]

ok i just want to clear something up, so could an extra coat of poly on the surface (after the main glassing is done and cured ) be used to get the boat smooth enough for tthe final topcoat... and what topcoat would be used to get it looking A1...do these steps sound like they would all work together ok.

[Christopha]

Perhaps if you talk to the "Boatcote" Folk......

[derekcohen]

ok i just want to clear something up, so could an extra coat of poly on the surface (after the main glassing is done and cured ) be used to get the boat smooth enough for the final topcoat

Yes


... and what topcoat would be used to get it looking A1

If you use polysester resin, fill in the gaps with either a mix of micro balloons (lightweight thickener) and resin, or use car body filler (car bog). Just make sure you key it in. The micro balloons are better as car bog is not waterproof and depends on paint to do the job.

I would still use epoxy resin - more waterproof and elastic (will not fracture as easily).


...do these steps sound like they would all work together ok.

Essentially, yes.

Regards from Perth

Derek (who has repaired many surfboards and windsurfers over a few decades)

[la Huerta]

thanks dekek, that is exactly what i wanted to know...cheers

[graemet]

If you have used polyester resin, ALWAYS wipe it down with styrene or acetone before applying another coat of anything. This removes the surface layer of wax that forms as the polyester cures and allows good adhesion. Most delamination occurs with amateur construction because of poor keying of additional coats. Professional layups usually don't have the problem because the next coat goes on before the previous one has cured. If your last layer of laminate is rough, as is should be if you have rolled it well out with minimal resin, don't add more resin until the structural coat has gelled or the fibres will float and weaken your layup, Glass is strong, resin is weak. A flowcoat of gelcoat applied will even the surface. If there is too much roughness, you can sand it back a bit but remember that if you cut through a layer of cloth, the layup will be weakened at that point. A final layer of surface tissue in the first flowcoat will help it to even out more easily giving you less to sand.
Cheers,
Graeme

[Boatmik]

La Heurta,

Are you using chop strand mat (short random fibres) or woven fabric?

The woven fabric will give a smoother finish that will require less filling by whatever method.

If you want the boat to last a long time I would be using epoxy rather than polyester. It actually joins onto the molecular structure of the cellulose (hydroxyl bond) which polyester doesn't.

The polyester relies on going a little way up the cellulose tubes and hardens. Just sort of tangles up.

The epoxy tangles up the same way but ALSO joins onto the molecular structure - much stronger.

Epoxy IS more expensive but does a more permanent job. But if you just want the boat for a couple of years polyester will probably be OK and will save you money.

MIK