What should I use to fill the stress cracks I ground out on the bottom of the boat?
 

I have a few long stress crack on the bottom of the boat I just ground out. Also along the chines, the gel had air pockets in spots and a few 1" long areas that were solid apoxy.

Should I grind deeper and wider, then fill with fiberglass or is there a filler I can use as is. I have ground through the gel and into the fiberglass a little bit, and there is no problems in the fiberglass itself. I just need to fill then sand down the entire bottom and then re-gel.

Thanks.

If you are sure the cracks stop at the gell then I would just feather it out and repaint it. Some times if they get the gell on to thick or to much hardener it will crack. If you want some added security put some Durratech additive in it so that it will be a liitle flexable and you should be fine. Just look REAL close to make sure you in fact do not have any cracking in the glass.

Jon

Thanks Jon, but the areas are too deep to fill with gel. I have done similar repairs using fiberglass bondo, but also thought about Marine-Tex. Is there another filler I should concider under the water line?

take a rag soaked with acetone and wipe the area, acetone evaporates quickly from surface, but will stay in crack if there is one.
later
Dave

All good information so far. I have used 3M Vinylester Filler with good results. Being vinylester, it is good for below waterline, as it is resistant to blistering.

I think marine tex is an ok Epoxy:D I do believe in West System epoxy but it has a learning curve as marine tex is ready to use and I think it comes in white and gray,put it on right and there will be just a little clean up of the area and your done and it may blend in well or you might not care if it is off just a shade in that area. As Audiofn said make shure that they are only into the gellcoat and not a bottom fracture.:cool:

Hello Ken, first off clean the area real well, make sure it is also dry, we don't want any mositure there, because if there is you will seal it in under the filler or gel and it might blister on you, a good cleaner is by Interlux 202 fiberglass wash, then any area's that show glass need to be sealed with a thin liquid epoxy to seal the glass suck as Interlux ht9000, or Pettit 4700, can use west systen 105/205, then you need a filler, you want to use either a epoxy resin, or i would use 3M marine vinylester filler great below the waterline, build it up then after it cures use your gel coat over the 3m filler, it will be a great repair

H2X,
We have to be careful of the "Amine Blush" that surfaces on cured epoxy. It can inhibit the bonding of the filler.
Ken, as stated above, this is really good information. I am also a fan of the West System.
Go down to BoatUS and get a WEST SYSTEM User Manual and Product Guide. Catalog # 002-950. It should be a freebie.
The other literature that is offered by WEST cost a little bit but is more detailed and well worth the money. After you look through the User Manual, you will have a better understanding of the capabilities of the WEST SYSTEM.

any cheap epoxy will blush, how do you know if you are getting a quality epoxy, see if it is 100% solid a lot of epoxies are 75% solid and 25% solvent, also look for no induction time [cooktime] also see if it say's it is blushless, one of the best epoxies out there is Progressive epoxy polymers, they are on the internet with some good info, they make many different kinds of epoxy unlike some of the others that only have one kind and they have you add "fillers" to their epoxy look at www.epoxyproducts.com

Thanks for the heads up on the epoxies.