MARINE TEX

[horsemel]

I need to make a minor repair to my bow just below the water line.  I think I will use Marine Tex to make the repair.  I have two questions. First Marine Tex works great under water I am told, but do I need to coat it with gelcoat since i am just going to paint it with bottom paint?  Second, how does the Marine Tex work in 50 to 60 degree weather.  Does it need to be 70 or 80 degrees for it to cure properly?  I know zero about working with glass and epoxy.
Mark Mueller
Blue Moon #815
1988

[RV61]

Mark,
I used MarineTex on to do a keel repair and my bottom paint VC17 held on no problem. It was 60 to 70 degrees when I applied. It is not recommended for use below 55 degrees.

Below is from marinetex.com

Will this epoxy cure in cold weather?
Epoxies need heat in order to cure. If your application temperature is not at least 60°F you must apply heat to the area before, during, and after the application in order for it to cure. We recommend you place a shop lamp approximately 12" - 18" in front of the application. The lamp will provide heat at a constant rate, so that the material's temperature is always constant. Do not apply a heat gun or hair dryer to the area, these types of heat will heat the area too much.

Only suggestion I would make if repairing fiberglass under the water line would be consider a barrier coat over top.   
Rick

[Jeff Kaplan]

mark, marine tex is great stuff. if it is cool out, as suggested above, use a heat lamp to hasten curing. once hard, it is easily sanded. one note though, there are 2 types of marine tex, white and grey. use the grey as it can be used under the waterline. also, the stuff goes a long way so mix in small batches first and add more as needed...jeff

[Jeff Kaplan]

mark, 2 things i forgot to mention. 1st, you can paint right over the marine tex and 2nd, make sure you have rags or paper towels and plenty of acetone for the clean up...jeff

[Stu Jackson]

Marine Tex is made in both white and gray.  Per their website there is no difference other than the color. Gray is not necessarily for underwater use, both can be used.

They say:

Marine-Tex is an excellent choice for repairing problem areas located below the waterline. Marine-Tex is resistant to water and many chemicals.

COLORS: White and Gray. Marine-Tex Gray is recommended for machinery repairs. Marine-Tex White can be tinted with ITW Fibre-Glass Evercoat's coloring agents for fiberglass and wood applications. Be sure to use only a small amount of coloring agent (no more than 5% of the total volume of epoxy.)

This is from: http://www.marinetex.com/marinetexepoxyputty.html

There is a modest difference in the strengths of the two different colors:

COMPRESSIVE STRENGTH*:
Gray - 13,000 PSI (910 Kg/Cm2)
White - 8,700 PSI (610 Kg/Cm2)
ADHESION SHEAR STRENGTH*:
Gray - 1,800 PSI (126 Kg/Cm2)
White - 2,300 PSI (160 Kg/Cm2)

An old little trick:  If you want a shinier surface, for instance for a visible ding, apply the material and cover with saran wrap; you'll get a smoother shinier surface, not like gelcoat, but close.  The white matches the Mark I boat white color very well.

[Jeff Kaplan]

stu, i am going to differ with you slightly on this. yes, both can be used under the water line, but i had the opportunity to go to the plant several times as i worked, at one time, in the same city, chelsea,ma. i explained to  one of the managers there that i was doing under the water line repairs to the hull and keel and he told me the grey was the preferred one to use. higher strength and better adhesion. for what it's worth...jeff

[Ron Hill]

Mark : I'd go with the gray Maine Tex and follow Jeff's advice.  Use a heat lamp to get the proper cure.  Then rough it up with some 60/80 grit sand paper so the bottom paint will stick.   

[horsemel]

Thanks for the information.  I was hoping to do the repair before we leave on a trip the end of the month, but April in Ohio sucks for warmth.  We had snow flurries again today.  I'll probably take a day off work early May and make the repair.  Boy do I hate missing work just to be around my boat! (Sarcasm intended.)
Mark Mueller
Blue Moon #815
1988