"Sistering" a center stringer.

[Safari]

Hi all,<br /><br />I am in the process of replacing the flooring in a 25' cabin cruiser.The boat is a 1957 model and over the years has developed areas of leakage. Whilst tearing out the flooring inside the boat, I saw that the center stringer had some rot. This stringer is a 2X6 that is tabbed to the hull with fiberglass tape extending upwards about 2". This 2" barrier has prevented water from contacting the wood. The top 4" (about 18" in length) however, is rotted away from water leaking in from the flooring topside. I have two places in which this situation has occurred. Access to this stringer is very limited. The dinette table seating assembly sits next to this area.I really don't wish to remove this as it would be a very labor intensive job. I believe that I can have access to the stringer however, if I cut out some of the flooring. Doing so would allow me to install 3/4" plywood stringer sisters on both sides of the damaged stringer.<br /><br />The rotted portion I intend to remove and fill with 2X4 that has been firstly encapsulated with 2 to 3 coats of thinned epoxy resin. This plug will be bonded to the stringer with a peanut butter resin and fiber mixture and will be located between the sisters. What do some of the more experienced ones think of this approach?<br /><br />Thank you.

 

[Chris1956]

Re: "Sistering" a center stringer.

Safari, The original stringer and other areas you wish to bond to must be clean and dry. A boat that old is likely all wood, and it surprizes me that the original stringer was bonded with fiberglass. I would have thought brass/bronze screws would have bonded the stringer to the floor. I also don't like using plywood in stringers, since it will seperate if it gets wet. I would recommend using dry pressure treated, solid lumber for the sisters, and some mechanical fasteners (SS screws) as well as epoxy resin and cloth to bond them to the original stringer.

 

[Safari]

Re: "Sistering" a center stringer.

Chris,<br /><br />Thanks for the speedy responce. The boat has a complete fiberglass hull. Even though it was manufactured in 1957 it continually amazes that the water damage is as little as it is. I swear the glass on the bottom of the hull seems to be at least 3/8".<br /><br />I have completly encapsulated the plywood, paying particular attention to the end grain. There are no voids or separations whatsoever. Have you used P.T. lumber befor, I had read that the chemicals present prevented proper bonding?<br /><br />Also, are you saying to use cloth rather than mat?<br /><br />Thanks