Re: lowering volume in Ch

Posted by Laszlo on Oct 8, 2005

Hi Lenny,

The fillets don't actually hold the boat together (except until the tape is applied). The glass tape is what actually does the work. The fillets are there to smooth the transition between the pieces of wood so that the tape's minimum bend radius is not exceeded.

Glass tape is absolutely strongest when it's flat. You can curve it and still have good strength right up until you get to a radius of about 5/8 of an inch (about the same as a US nickel). If you go beyond that point, you're no longer bending the fibers, you're folding them. The fold is a stress concentrator and the joint becomes weak very quickly.

So as long as the combination of fillet and wood is no rounder than a nickel, it doesn't really make any difference for strength how thick the fillet is. On the 16LT that I built, some of the seams had fillets less than 1/8 inch wide. Others were 3/4 or so. Match the width of the fillet to the angle of the joint, use the minimum size needed to meet the bending radius requirement and the weight will take care of itself.

BTW, the numbers that I mentioned are for small, light unpowered boats using 4 & 6 oz glass tape. Please don't anyone try and build a cabin cruiser based on them :-)


In Response to: Re: lowering volume in Ch by Lenny Flank on Oct 8, 2005