Moderated Discussion Areas
ContinuousWave: Whaler Repairs/Mods
Epoxy and Foam
|Author||Topic: Epoxy and Foam|
posted 03-25-2002 03:14 PM ET (US)
Fishing season is starting soon and its time to start working on the boat. If I fill an old screw hole with epoxy, will it fill the hole? Will the curing of the epoxy leave a void between it and the foam core of the boat
or will it bond to the foam? My boat has a lot of old screw holes and i posted a few questions last season about how to fill old screw holes. Every time I think i know how to deal with a repair i hear some small part of how different products interact.
There were several different postings about how to repair old engine mounting holes in the transome. What is considered the best way to repair old mounting holes in the transome after a boat is repowered? What problems can occur if these holes are not repaired?
posted 03-25-2002 04:27 PM ET (US)
Look at my question for today . I think your asking the same thing or very similar. Do you use a filler under the epoxy to fill the void between the fiberglass deck and the foam?
I dont know but if /when you find out please advise.I would think so becuase I dont see the epoxy holding down the deck with the foam??
posted 03-25-2002 08:43 PM ET (US)
I just used white marine putty epoxy to fill screw holes. No sanding, and it buffed out so that it was barely noticeable.
posted 03-28-2002 02:27 PM ET (US)
What I am confused about is: Will the heat generated by the epoxy when it cures cause the foam to melt and leave a foid between the cured epoxy and foam? How much structural strength does the foam have to hold the epoxy if it does bond to it?
posted 03-28-2002 07:00 PM ET (US)
I talked to the West System rep at the Maine Boatbuilders Show last Sunday and asked him those questions about the heat building up and melting the foam. What he said is in agreement with my experience with building several cedar strip canoes with the W S epoxy. If you mix up say a quarter cup of epoxy and let it sit in the mixing cup(old yogart container is best) for 10 minutes or so, it gets quite hot as it starts to set. But take the same amount of epoxy, mix it the same, and then spread it out over a wide area, that is to say, increase the surface area greatly, or put it another way, reduce the cross section, and there is very little heat generated, I don't even think you could feel warmth generated if you spread it out thin. The chemical reaction is an exothermic reaction, and is accelerated by heat so that if it produces heat, that heat quickens the reaction, which in turn produces more heat. (Until the ingredients have completed polymerization) Increasing surface area allows excess heat to escape without altering the polymerization time. If you are still concerned that your particular setup will produce excessive heat during polymerization, use a " slower" hardener, such as West 206, or pack ice bags around the setup. Do not try to alter the ratios of hardener to resin in an attempt to modify setting times or speed.
The second part of the question relating to adhesion to foam core, he said it would adhere, without disolving or melting it chemically.
posted 03-28-2002 08:18 PM ET (US)
if you are using this to fill a void under deck (drill hole and squirt method) you need to remember that a micro thin layer will complete the adhesion process. You dont want to let it build up under the deck surface. Get it all laid out and work in sections and once you squirted amount under the surface apply pressure by weighting the deck down so it is spread very thin. If you dont weight it down it will be your worst case scenario because a wad of epoxy will trap itself in a closed space and will heat up greatly. As long as you get it on quickly and then immediately (5 minutes with 206) apply the pressure to spread it out it will work great. many guys feel they need to build it up which is exactly the opposite of what you want to do.
posted 03-28-2002 11:50 PM ET (US)
Good advice on the epoxy heating. It also seems to cure faster with temperature, so if working in the sun on a 95-degree day, a little pot of epoxy will "kick" very rapidly and generate plenty of heat.
The "marine putty" stuff may be a reference to MarineTex, which is an epoxy forumulation with filler. One feature of it is it can be cleaned up with water (until it sets).
You can make a similar compound from WEST resin and hardener that has been thickened with fillers. WEST cleans up nicely with vinegar.
Filling transom holes: I need to write a reference article about this, as there has been some excellent discussion. The most interesting data point was the comment relayed from Whaler themselves that they recommend using a layer of cloth around holes filled with wooden plugs to help prevent the gelcoat top layer of the hole from being popped out.
I fill all my vacant screw holes with epoxy, using unthickened WEST System epoxy to create a water-tight seal. I leave room for a second coat of thickened and tinted epoxy or gelcoat as the top layer and color match.
I find titanium white with just a trace of raw sienna makes a nice match for desert tan. I use acrylic pigments from an art store.
posted 03-30-2002 12:59 AM ET (US)
Thanks everyone for the responses. I remember reading somewhere that when laying up glass, try not to lay to many layers at once. The heat generated by the resin will not escape. This goes along with what simon said about the epoxy in the cup. I think I will use marinetex for old screw holes.
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