73 Fiberform Stringers

[Sidserv]

I am in the process of replacing the stringers in my 1973 Fiberform Columbia 16VB and am trying to figure out how thick to make the glass on the stingers. I am using Polyester resin and have 10 yds of 1.5 ounce CSM and 20 yds of 6 ounce cloth. Right now using laminating resin I have 5 layers of glass in layers. I have 2 layers of 1.5 oz mat then 1 layer of 6 oz cloth and then 2 more layers of 1.5 oz mat. I am wondering how many more layers I should put. The origional stringers were put in with a chopper system so getting a measurment from the glass that I removed was impossible. It was anywhere from 1/4 inch thick at the fillet to 1.5 inches thick. I am figuring right now with the glass I have on there being strong enough but just not sure. I plan on capping the stingers with one last layer of 6 oz and using finishing resin. Any info on the amount of layers I should use would be great.


Thanks
Sid

 

[chargerboy]

Re: 73 Fiberform Stringers

Welcome to the forums! The more you put on, the stronger it will be. Are you building the stringers out of wood? I would build up 12 ounces of woven mat on wood stringers myself. It may or may not be overkill, but anything that makes the boat stronger will pay off in the end.

Use the search feature of the forums, and browse around and you'll get an idea of what other people have used.

 

[ondarvr]

Re: 73 Fiberform Stringers

If it was just chop to start with, then what you have on there now should be fine.

The CSM has little strength compared to other types of woven or stitched glass, so adding more increases the weight more than anything else.

6 oz cloth is very light stuff, one layer of 1708 has almost three times the amount of continuous strands and since its not woven the strength is even greater. So one layer of 1708 would possibly have been much stronger and lighter than what's on there now.

What is actually needed on a stringer can only be calculated by a marine composites engineer and he would need to know the exact details and intended use of the boat. Most older boats had no engineering done on them, they just added more glass to areas that failed, if it didn't fail they did nothing.


I think I should have stopped typing after my first sentence.