mast rot

I"ve been restoring a 67 Cheoy Lee offshore 31. I finaly got the paint off my masts. where the mast steps is a cup fitted over the end of the spar. upon removal I found rotten spongy wood. It is a box construction mast.
The Two boards that fit in the rabbits have rot. Part of the "core" also has some rot, and I suspect that the rabited boards may also have some damage but it is hard to tell now. The rest of the mast looks pretty good and it would be a shame to trash them for 6" of rot at the bottom

What can I do?
Can I scarf in the two opposing boards? Can the scarves stop at the same spot on the mast. How close can I come to exsisting scarfs? And the center block? do i need to make scarfs into that as well.

any help would be appreciated. Thanks

 

In general, is CPES flexible enough for use on spars?

Where rot does not extend very deeply in an area, but only involves a blackened area where water got under the varnish, and the surface cleans up to a "fuzzy" texture, into which one's knife can penetrate 1/16" or less, would CPES help here prior to revarnishing?

Just how flexible is CPES for spars in general, and in this setting specifically?

Thank you.
Robert

 

Soundshooter, you mast heel can be repaired, but the specific type of repair is difficult without looking at the areas of difficulty. The very least the mast should be pulled and blocked up flat for the repair, which can be done easier and without the compression loads of an upright spar making things difficult. Yes, scarfs can be used, which should be well staggered from other joints. This may mean removing much more material then is bad because of the scarf locations.

Robert, CPES is flexible enough for use on spars. It does not replace wood that has rotted away. It just seals and stabilizes the moisture content of the coated piece. If you have lost a substantial amount of wall thickness, the area should have a repair, not just a coating of CPES. A 1/16" of bad wood on a 3/4" thick mast stave is over a 16% reduction in the mast wall thickness and should be considered suspect. CPES is a sealer only.

 

I talked to a couple of guys that said because my rot was at the bottom were the mast is laminated solid I could replace it with solid wood and that there was no need to build the box. I've attached some dawings and thought I would get the forums opinion on the best way to perform the repair. thanks

 

I'd make the repair as close to original as possible, stagger the scarfs- & if they come close to an original scarf take the repair to it.The top of the base block could be suspect & inspection will reveal this or give peace of mind that all is well within. If you make it how it was it'l be good for as long as it was. Regards from Jeff.

 

One of the most important aspects of a hollow mast is keeping its ability to drain moisture that collects from condensation and leaks. The bottom of your mast and the step itself should have weep holes for just this. They probably got plugged up with years of dirt and dust, trapping moisture. A solid plug will do the same thing, except the damage next time will be higher up the mast, where the solid section begins and the hollow ends.

I guy I know made me a new mast a couple of years ago. He lives an hour from here and makes several a year. He has a 38' mast in his shop right now. He has been fixing my boats for several years and knows his stuff. His comments were, a solid section in the bottom could make the mast weaker there, he had a reason, but I can not remember it well, also make the repair plenty above the damaged area and similar to the way it was originally built, watching the scarf locations so the do not over lap any place and to insure there is a way for moisture to leave the step and heel of the mast. He said water will get in, it is almost imposable to stop it, unless the mast is new, so leave a way for it to get out. He also said if the heel is damaged the mast step is probably damaged too.