Fiberglass Curing Time

[Parkhil2]

I was wondering if anyone had any suggestions as to how long i should wait, if at all to apply gelcoat to viynlester resin, Also, this is a transom rebuild, how long should I wait to hang the motor back on?

 

[ondarvr]

Re: Fiberglass Curing Time

You can apply the gel coat as soon as the resin is hard, if you wait more than a couple of days VE resin can surface cure even without wax and then you may not get a good bond without sanding it.<br /><br />If the repairs are hard you can put the motor on.

 

[Jilly - 5]

Re: Fiberglass Curing Time

I agree on the "hardness" test. But more importantly, especially for a transom, is the ratio of hardening agent to resin that you used and the ambient temperature. If too much hardening agent,in teperatures over say 75 degrees, the resin will surely get hard, but too quickly resulting in brittleness (not good for a transom that's getting a motor). It could easily harden within hours. Generally, a hard and strong application should be ratioed to harden over say a 24 hour period. It would be tacky at 12 hours, you could leave your fingerprint, but you couldn't "dish" the resin with your finger. Resin is comprised of long hydro-carbon molecular polymers that join and bond in a criss-cross nose-to-tail fashion in a long curing process. Too much hardener coupled with high temperature doesn't allow them to "line up", but rather "freezes them in place". The molecules are more stuck together, than bonded together. The only remedy for a fast-cured application is an overlay of a slow-curing application. <br /><br />How big is the transom and what horse power will it carry?

 

[ondarvr]

Re: Fiberglass Curing Time

This resin is most likely formulated to be catalyzed at 1.25 or 1.5% and tested at 77*F. Don't use more or less catalyst than this and you won't have a problem. <br />There is no cure for an over or under catalyzed layup, if its not right, it won't ever be.

 

[Terry H]

Re: Fiberglass Curing Time

within an hour of the layup work you should have the gelcoat ready to catalyze and apply. Chief

 

[Parkhil2]

Re: Fiberglass Curing Time

Thanks for everyones input. I plan to layup the glass, mixing at a ratio of 1.5oz to a gallon, as spec'd by the manufacturer, let set up, then start the gel coat process. The motor wont be hung for at least 36 hours after the layup work.

 

[BillP]

Re: Fiberglass Curing Time

Gelcoat can go on immediately after the resin tacks off enough to leave your finger print. If you use laminating resin it needs no prep as long as the surface stays tacky...which can be weeks. That's why laminating resin is used in production...there's no other reason. <br /><br />Ya just might want to check with the mfg of your resin to get their curing time details. Ask the chemists, not the sales reps. Poly resin mfgs used to give charts that showed the kick time, curing time curve and hardness factor. Most I saw needed to kick hard within an hour or so and cured for approx 30 day to reach max hardness. Undercatalyzing to make an extremely (many hours)long kick time is a no-no because the resin never reaches it's max Barcole hardness that way. Epoxy is different.