Fiberglass quality

Ross · Mar 18, 2009

Franklin said:
BTW: is there a color difference between polyester and epoxy? Just wondering if I can tell what's already there by looking at it.

Can't depend on color but epoxy will soften at around 250 degrees F. They each have a distinctive odor when heated enough to smoke. Acetone will slightly attack polyester but not epoxy.
I have found that I get excellant bonds polyester to polyester when I work with freshly ground old surfaces with a 24 grit finish and an acetone wash. I have tried to remove my mistakes with a sharp chisel and have never been able to separate the old from the new at the interface. I always have had to pick up the grinder.

Ross · Mar 18, 2009

Depends on the size of the batch and the shape of the pot. A small batch in a shallow pan will last longer than a large batch in a deep pot. Once on the glass it depends upon the air temperature. I think that you get at least a half hour at 75-80 degrees. longer with the slow hardener.

Jumpstart · Mar 18, 2009

Franklin- good luck with your project. Some guys around here have been using XIM 400W NT bonding primer over epoxy to bond the gelcoat with. This only works above the waterline. Sherwin Williams has it or available online from XIM. Make sure you get the NT version and not the older 400W product.

Ross · Mar 18, 2009

This should be required reading for anyone contemplating fiberglass repairs. http://www.ericgreeneassociates.com/images/Repair_of_Composite_Boat_Damage.pdf

Ross · Mar 18, 2009

Do a little practice first. Wax a shape, it doesn't matter too much what shape just something fairly long and smooth like a bread pan. Then form the glass and resin over that and let it harden. Then pop the pan out of your new glass shape and wax the dickens out of the inside of that. Then build the glass and resin inside your new fiberglass mold and allow that to cure. If you have done everything right your glass duplicate of the bread pan will pop out of your mold. If not you may have a couple of pounds of junk.

Ross · Mar 19, 2009

Franklin, Your port rail should be identical to your starboard rail. If you make your mold from one it should be able to duplicate the other.

Ross · Mar 19, 2009

Franklin, from your fiber glass supply co catalog.
http://www.fiberglasssupply.com/Product_Catalog/Release_Agents/release_agents.html

sailingdog · Mar 19, 2009

Coat the section of his boat very liberally with mold release and then fiberglass over it... that's the simplest way to make a mold of it. Once the fiberglass cures, you should be able to pop it off and then use it as a female mold for your boat. Make sure to tape off the area well and tape over any openings that the resin might otherwise get into and then coat with mold release.

If doing that makes you nervous, you could use something like Post-It glue stick to attach a layer of plastic wrap to the boat and then glass over that. Using thick plastic is a bad idea, as you want to get as close a perfect mold of his boat as possible.

Franklin said:
Any thoughts on how to make a mold? I was thinking of making a mold of my friends 376 toe rail and use that to work backwards (laying down layers until I got to the last layer and then lay that whole piece on the grounded out rail). I just am not sure what material to use to make the mold and how to keep it from breaking.

So far I only have two ideas: layout thick plastic over his toerail and then 1) spray it with foam 2) lay down two sheets of cloth and polyester resin. I wonder if using polyester resin would get too hot for the plastic to protect his boat.

Thoughts? Other ideas?

Ross · Mar 19, 2009

If you are considering a short section (4' or less) and the curve is fair, then the forward end on one rail section would become the aft end on the other rail and inside and outside would be correct. Try it with a big lump of modeling clay. Shape it to one side and try it on the otherside.

sailingdog · Mar 19, 2009

You're assuming that the boat is relatively symmetrical front-to-back, and I seriously doubt it is... Most hunters have a fairly narrow bow and a fairly wide stern. I think he really needs to get the mold off of the same area on a sister boat.

Ross said:
If you are considering a short section (4' or less) and the curve is fair, then the forward end on one rail section would become the aft end on the other rail and inside and outside would be correct. Try it with a big lump of modeling clay. Shape it to one side and try it on the otherside.

Ross · Mar 19, 2009

sailingdog said:
You're assuming that the boat is relatively symmetrical front-to-back, and I seriously doubt it is... Most hunters have a fairly narrow bow and a fairly wide stern. I think he really needs to get the mold off of the same area on a sister boat.

I have seen boats that appeared to have a fairly straight run from the bow back to about the first windows before it started to curve. If the section fell into an area like the transition from straight to a curve then my idea wouldn't work.

Hermit Scott · Mar 22, 2009

Franklin did you take any pics of the damage you are going to repair? I would like to see what you are going to have your hands into.

txtowman · Mar 22, 2009

Franklin. I am just wondering why you ordered the glassing supplies online when there are at least 20 dealers nearby kemah? I had my boat at KBmarina last summer. good luck with the repairs. sid

John Nantz · Mar 23, 2009

Chain Plate Load

Franklin - a couple thoughts about the chain plate load. One thing you could do to get another handle on the load is to check what the stays and the bolts will handle. The designer came up with the bolt sizes and stay sizes based on loads so working backwards should give some more ballpark numbers to make judgement decisions with. And there are different kinds of load strengths, like elastic limit and ultimate strength.

Also, on another subject, I'd agree with a statement made earlier about taking into consideration resale value. As a thought, maybe talk to a surveyor (or two) and get a recommendation about what they would want to see in the nature of such a repair. Perhaps they would be happier if it was done by someone who is well recognized in the trade and then you document the work well. Maybe even write something up about what he did (saving him the work of writing it) and have him sign it (having this document as part of the job if he is okay with that). Let him do what is deemed the critical work and you do the rest. Sure, it might cost a bit more but you could get it back manyfold at resale time. Also, if you plan to insure it again, what would an insurance company want to see. For that matter, the next owner might want to insure it. Anyhow, this is just a concept thought.