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fiberglass repair gelcoat cracks

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rod baker Commited Dubber

54 posts · joined May 2009 ·

#780344
Hi all i am rebuiding an older baja that has seen its fair share of abuse and there are cracks all over the gelcoat lots of little hairline fractures

what is the best method of repair
do grind em all out and reglass and paint it all

thanks rod

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1970 BAJA BUG CHEAP N FUN ALMOST NO RUST 1500 AIRCOOLED ALL STOCK AND 1973 CONVERTIBLE BAJA http://www.rodstruckentrailers.co.au

bajachris88 The international telephone dialing code for Antarctica is 6

6,661 posts · joined Apr 2005 ·

#780345
I have the same issue... so will watch this closely.

Can tell ya that spraying primer filler and top coat over certainly didn't help 🙁, after 6 months the cracks turned up again.
(ô_!_/ô) (ô_!_/ô)
69' baja: kombi box, thing spindles, irs, disc front, type 3 rear drums, 2 inch lift kit, 31x10 rears. 👍
New engine in process: 94mm p&bs, 74mm C/w chomol Crank, 35.5x39 SP heads, turbo. Wierd combo, hopeful torque monsta!

barls Administrator Causer of Chaos and Mayhem

9,476 posts · joined Jun 2004 ·

#780348
take it to a professional boat builder they have the equipment and supplies to fix this properly
“We all pay for life with death, so everything in between should be free.” Bill Hicks
the chaos project - click me

matberry Moderator Go hard or go home

8,114 posts · joined Mar 2006 ·

#780375
Yep as above, the gelcoat needs to be redone or the cracks will continue to reappear even through the paint.
Matt Berry Motorsports...air cooled advice, repairs and mods Ph 0408 704 662
OFF-ROAD,CIRCUIT,DRAG,STREET,ENDURANCE

bajachris88 The international telephone dialing code for Antarctica is 6

6,661 posts · joined Apr 2005 ·

#780387
IS there any way to do it at home at all?

Mine kit personally is coated in all these little hirline cracks... ut its a nice thick kit. Painstakingly grind and fill? or is there a coat u can put on top?
(ô_!_/ô) (ô_!_/ô)
69' baja: kombi box, thing spindles, irs, disc front, type 3 rear drums, 2 inch lift kit, 31x10 rears. 👍
New engine in process: 94mm p&bs, 74mm C/w chomol Crank, 35.5x39 SP heads, turbo. Wierd combo, hopeful torque monsta!

rod baker Commited Dubber

54 posts · joined May 2009 ·

#780416
as i live on a right near lemon tree passage marina i have done that and was told to grind out the cracks and re-glass or just paint, gelcoat is not realy needed if painting and do it carefuly or i will make more work for my self
1970 BAJA BUG CHEAP N FUN ALMOST NO RUST 1500 AIRCOOLED ALL STOCK AND 1973 CONVERTIBLE BAJA http://www.rodstruckentrailers.co.au

VolksVair Officially Full-On Dubber

252 posts · joined Apr 2010 ·

#780424
Okay all, when you get fine stress cracks in gelcoat, you must grind the gelcoat back to the glass, if you have an area of say 15 cm round of fine cracks, you grind an area of twice that and be careful NOT to leave a deep crater at the outer edge, you must feather off the edges, in other words blend the edges into the surrounding gelcoat as to not leave an edge🤪 obtain some gelcoat(waxed) & some hardener, if you are working on a vertical panel, go into your bathroom whilst the mrs isnt looking and grab the talc powder, sprinkle talc and stir until the gelcoat is almost like a paste, then add your hardener and apply to panel, but and I say but, make sure you buy a litre of acetone and wipe down the panel before you apply the gel coat, apply the gelcoat and dont try and make it perfect, just put the gelcoat on and make sure that it is higher than the surrounding gelcoat surface, leave for a day then start blocking back. There is a product called gelcoat repair, its allready a thickened and waxed gelcoat paste white in colour and you get a small tube of hardener with it, this makes life a lot easier and you get it at all boat shops. from memory I think the brand is K & H and its a small round tin and maybe 50mm tall. Now if you have a tear in the glass, you need to grind the underside, mix some resin & hardener and lay a couple of layers of glass, let set, then grind the topside just into the fresh glass then apply gelcoat and block back, make sure that you dont do any of these repairs in temperatures lower that 18 celcuis hope I have been of some assistance cheers Frank
Adventure Before Dimentia

VolksVair Officially Full-On Dubber

252 posts · joined Apr 2010 ·

#780428
Now that you have gelcoated the panel, make sure that when sanding, only concentrate on the fresh gelcoat surface area until you are almost level with the surrounding original gelcoat, only until you get to that stage, that you are able to start to feather the fresh area into the surrounding gelcoat, and remember NEVER sand anything with just the paper in your hands!! allwayz use a rubbing block. if you only have a long hairline crack in the gelcoat, once again , just grind the length of the crack and about an inch past each end and about an inch in width and follow first instructions. now chow mama, I'm gettin back out side and under the hoist cheers Frank
Adventure Before Dimentia

alien8 Wolfsburg Wizard

521 posts · joined Sep 2008 ·

#780442
Like Frank said you have to grind/sand the gel coat off to the laminate. 60 /80 grit on a dynabraid or polisher/sander. It is better to do the whole panel if your re painting. Repairing gelcoat sections and feathering is a pita. You dont want those unseen cracks coming out of the old gelcoat after you have painted. After the gelcoat is off inspect and repair any cracks with woven fibreglass cloth and polyester resin. Apply a filler(waxed resin) coat to the whole pannel and sand flat with 120grit. Spray the gel coat or get someone to spray it on as it comes out much flatter and requires less blocking. Start with a hard soft block 120 grit and finish with a soft soft block 180 and 240 grit. Then its ready to paint.

If I was using two pack paint I would skip re-applying a gelcoat as its not needed if painting and finish the pannel to 240 grit on a filler/finish coat in prep for paint. But thats just me.

bajachris88 The international telephone dialing code for Antarctica is 6

6,661 posts · joined Apr 2005 ·

#780459
thanks guys...
sheesh... i got cracks on every panel. Looks like i got a long road ahead lol... but none the less... should last donkey's years.
(ô_!_/ô) (ô_!_/ô)
69' baja: kombi box, thing spindles, irs, disc front, type 3 rear drums, 2 inch lift kit, 31x10 rears. 👍
New engine in process: 94mm p&bs, 74mm C/w chomol Crank, 35.5x39 SP heads, turbo. Wierd combo, hopeful torque monsta!

CJ_DT Casual Dubber

37 posts · joined Oct 2005 ·

#780575
Not sure you should use gelcoat, perhaps flow coat instead, gelcoat doesnt fully setwhen exposed to air (normally has the mold on one side and the glass on the other side)

matberry Moderator Go hard or go home

8,114 posts · joined Mar 2006 ·

#780580
Waxed gel coat goes off properly for a sticky free finish, unwaxed is used in a mould and stays sticky for subsequent layers.
Matt Berry Motorsports...air cooled advice, repairs and mods Ph 0408 704 662
OFF-ROAD,CIRCUIT,DRAG,STREET,ENDURANCE