See full version: How long does Bondo body filler take to dry
Subsequently, question is, why is my Bondo not drying? If the Bondo isn't dry, it's because you didn't use enough hardener or the temperature is too low. Getting it wet didn't help. Try using a heat and strip gun. It gets hot pretty quick so keep it moving.
Generally, in a matter if a few minutes it will start to harden and get rubbery. At that point, you can carve it up with a utility knife, a hand planer or a bondo rasp. Just make sure you leave enough to do a final sanding, usually within 10 to 15 minutes you can start sanding it.
Is Bondo body filler waterproof? [links]
If your filler hardens too fast, you used too much, if it takes too long, you didn't use enough. You only want to mix what you can use in about 10 minutes. Properly mixed, body filler will begin to thicken in 10-15 minutes, and be fully cured in 30. here
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. [links]
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?
Re: Fiberglass Curing Time here
Re: Fiberglass Curing Time here
Curing time is mostly affected by how much hardener you use. Too little, and you might get a fairly long working time, but the downside is that it may not cure at all if you didn't mix in enough. [links]
I do most all of my fiberglassing in a 70 degree climate-controlled workshop, so temperature isn't that much of an issue.
It should harden, heat will help. I see your warming it, try to keep it close to 70 degrees. Theres special winter resin they use down to the boat shop for use in colder temps. As for shelf life I dont know. here
I don't know much about the Bondo fiberglass, just the body fillers, but I'll guess that there is a shelf life. here
If your repair is on the inside, as polyester resin hardens it releases styrene. Styrenes heavier than air and will lay in the hull and slow dry time.
I suggest you keep track of how many drops per ounce of resin you mix in, and record the batch with a satisfactory working time.
Just so, what is the ratio of hardener to resin? [links]
Subsequently, question is, what is Bondo resin? Bondo All-Purpose Fiberglass Resin is 100% waterproof and designed specifically to be used with Bondo Fiberglass Resin for interior and exterior repairs. Bondo All-Purpose Fiberglass Resin can be used on multiple surfaces including concrete, wood, fiberglass, metal and more, and can also be used as a waterproof sealer. more
Open the can and mix the Bondo with a stir stick if there is a layer of liquid on top. Use the stir stick to lift a golf ball-sized dollop of filler out of the can and reseal the can. Mix a larger amount of Bondo and hardener if the area you need to patch is larger.
The ratio range for catalyst to resin is 1 to 2 percent hardener to the total volume of resin to be used. For example, four drops of hardener will be 1 percent of 1 ounce of resin. Adding more of less of the catalyst agent will speed up or slow down the curing time for the resin. [links]
Polyester resin is used for laminating fiberglass reinforcement, molds and, yes, waterproofing wood. Laminating resin will become hard but will remain slightly tacky to allow paint or more fiberglass to bond to it. Waxed or finishing resin can not be painted over without removing the top layer of hardened wax first.
Mix the Bondo® All Purpose Fiberglass Resin in a paper cup with the Bondo® Fiberglass Resin Hardener. For small applications use 10 drops of hardener per ounce of resin. Working time will be 10 to 12 minutes. For larger applications, use half of the fiberglass resin hardener supplied, to half of the resin container.
Mix the Bondo® All Purpose Fiberglass Resin in a paper cup with the Bondo® Fiberglass Resin Hardener.
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For small applications use 10 drops of hardener per ounce of resin.