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Fiberglass crack

I have a motorcycle saddlebag I'm painting and the top hatch door has a crack underneath on the side,
doesn't appear on the outside gelcoat. Should I vee grove this out and add resin or is there something
better to use? I'm concerned it may crack again from opening and closing the door then come through
my paint. Thanks


jim, you will need to "V" that out and patch that with some glass...unfortunately. dont use just resin. if you dont use glass it will probably crack again. you might get by with mixing up some epoxy resin and adding a thickener to make filler out of it BUT glassing it it will be best.
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So, add some fiberglass matt strands to the resin? Is that what you're saying?
Should the surrounding surface have a layer of cloth added?
And do you think I should go ahead and vee out the other side too?


Trying to be the best me, I can be
Check out this video by SEM. Should answer all your questions.

Although they are talking about SMC (sheet molded compound) the principles still apply. And you can use the SMC repair compound on fiberglass as well.


evil painter
If you can't see anything on the good side, probably best leave it alone. Any repair will shrink some now & a tiny bit later throughout time, so I wouldn't create another issue if I'm sure I didn't need to. When you grind into the backside , you may see the crack stops....
Cloth is not something you'd want .
I've generally done similar repairs the traditional v- groove & a little matt with resin. Polyester can work, but epoxy is best.
I haven't looked into the new repair stuff like in the link Chris posted, but I have cut & glued back together thick fiberglass(butt joint) on the end of my personal custom car hood with Smart's 3-m 8115 type panel adhesive 3 years ago & it won't budge when beat on, so some of these new to me repair options may be easier for you.
Hood in picture was cut to change from 2010 camaro profile to more angular 2016 profile. small part upfront was leftover cutout part used to extend now longer front profile. Point is yes the new adhesives are strong, BUT before paint on the upper side that will show the most it will get a traditional v-groove repair job to avoid a possible bad shadowing issue from all adhesive joint with no glass fibers.
Strength , shadowing, & shrinkage are the main factors to consider in a fiberglass repair.
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