SATURDAY AFTERNOON MASTWORKS

[bob mitchell]

In my original first blog REBUILDING WILSON (hull #113) I did a NEWPORTER MASTS POSTMORTUM ANALYSIS from some pieces of thrown away masts I salvaged from the previous owners back yard. Now that I have the main and mizzen masts from Sans Souci, I went back to those pieces for many reasons.
1) being a southerner I have not worked with sitka spruce, so here was an opportunity to feel the wood.
2) the mizzen on Sans Souci was roughly handled during the removal, and a seam opened up - so playing with my old mast pieces seams seamed like a logical idea. There seem to be many solutions to seam repair, one being routing or sawing right down the seam (or more specifically to one side) and regluing. My gosh that sounds radical! So a little practice on scrap masts to fine tune your guide would be great.
3) The top foot of the mizzen is soft and will have to be rebuilt. Amazingly enough I think I have salvaged enough sitka spruce from my old mast pieces to do it.
4) There is always more to learn. Thats why I keep writing to you people who have had to work on their masts - contribute, please.

So, of course I talked to Clyde first, and he sent me this advice and picture.

FROM CLYDE
I don't have any info on hand (if I ever did) as to when those masts were built, place of build, or the hull number. But if they were built in New Jersey I'd bet that they are with solid blocking and plywood rabbets. My first thought is to route out (or saw out, see attachment) the glue line needing rehab and glue in a sliver of wood (same specie or close) the thickness of the kerf. But I'm still mentally in the pre-epoxy era, having very little experience with the stuff. Seems like there are a lot of boats being built these days (small ones, anyway) that have joints you can drive a truck through and are filled with thickened epoxy and taped over. So your idea may be the modern way of doing things. Go to it. I doubt seriously that you will leave the mast in a condition less than original. It will most likely be better.
FROM CLYDE, 2nd response: My first idea, and lightly mentioned, was to rout the seam. You seem to be thinking smaller. With a router you would need a fairly thick piece to fill the gap, making two glue lines, but I kind of like the fill wood to be thick, to have its own strength. If you rout it out you must keep the bit to the outside of the glue line and take no more than twice width of the glue line from the inside piece. Looking at the attachment I sent, outside is to the right, inside to the left. The idea here is to make sure you don't take the edge off the plywood rabbet and allow the top piece drop down. A little nick off the ply's upper right corner-as illustrated-shouldn't hurt. For a cutter (blade) a dado cutter set at up to about 1/4 inch would also work, if you can get one on a circular saw.

So with that suggestion, I set out to test some guides for seam ripping. The thing is, althougth it is a lot of work, I know that if I cut and reglued (epoxy) the whole mast I KNOW it would be bombproof. And if I ever get to the ocean that is what I want. PLUS it gives me the opportunity to inspect and beef up the inside (like a triangular piece in the corners to increase the glue surface.) Also, since I have added an upper helmstation windshield my mizzen boom will be 6 to 8" higher, so I need solid internal backing where the boom contacts the mast. However, I guess this technique could be applied to sections of a mast just as well as the whole thing - and if only one side has sprung loose, you could just do that side, and reinforce the other internally with a glued in triangular corner piece. Here is the guide I came up with.

So here is what I learned.
1) The guide is not hard to use, but does require careful calibration to get the cut just right, ie taking all of the wood on one side of the seam, and leaving the surface of the seam clean (see clyde's comments above). I am more inclined to run a thin cut and then fill with epoxy and a carbon fiber ribbon up the mast, as opposed to a thicker cut and wood spline, but this is a WORK IN PROGRESS, AND I WELCOME ANY SUGGESTIONS, INSIGHT, OR COMMENTS.
2) The saw wants to wander so keep pressure applied to the side of the guide. I used a saw blade with an 1/8" kerf (what was on my saw) but have purchased a MARATHON 1/16" carbide tip for the actual deed, if I do it.
3) UNFORTUNATELY, typically the stave scarf joint, if exposed to moisture, fell apart after I made the seam cut. In my limited sampling this occurred especially where the mast was solid core and there was a lack of ventilation. Look at the photo above carefully and you can see I laid the upper scarf joint board across the mast. (the scarf joint itself is right in front of the saw.) Fortunately, this mast had been wrapped with carbon fiber at the scarfs. (clearly visable in photo) I was astounded at the strength of this minimal wrapping, and of the four or five joints wrapped none of them had come apart. They only separated after I cut the rapping. I am also going to explore with Gougeon Brothers (West System Epoxy) the possibility of injecting the scarfs with epoxy, ie warm them up for maximum penetration, then drill right across the scarf surface (1/8 to 1/16 diameter) two or three times, and then inject with penetrating epoxy. Not only might this adhere, but also would form a "key" against compressional loading.
It is important to remember that these mast pieces had already been neglected for years while they were on the boat, and then they laid around in pieces in the rain outside in a pile for at least a year or so, so they are hardly reflective of the conditions that might exist in a well maintained mast.

That about raps it up for today. Definitely will be updating this blog as things develop.