mast repair

[hallaquila]

I have a 53-ft, keel-stepped, sitka spruce, composite box mast, cutter-rigged with single spreader and upper jumper struts. I recently over-tentsioned the backstay and broke the mast just below the jumper strut base and where the inner jib attaches. From the mast cap, estimate 10-12 feet to the break. I am about to haul and unstep the mast. Any thoughts on repairs to my 1951 custom steel yawl with wooden spars?
Tom
Baltimore

[Dan McCosh]

It's usually quite difficult to break a mast with an over-tensioned backstay. I would suspect that the mast has some rot in the area where it broke. Anyway, a repair with a new section scarfed in should be possible. It's difficult to tell what's going on without a full examination of the problem.

[glennmajestic]

Try to post pics so we can see the damage

[hallaquila]

Hello, Dan,
The break occured because the starboard jumper strut stay was over tensioned causing the top of the mast to cant forward. The port jumper strut stay was slack. Have a backstay adjusting wheel that allows easy tensioning, but I overdid it. As to the wood, having restored both masts, reglued West System, carbon fiber tape, etc., and totally took apart the 28ft missen, there was no rot anywhere, with the exception of a small patch at the missen mast base where water trapped. It's a straight across break, a bulged patch aft that bowed the sailtrack pulling out the screws over a foot section. There are horizontal cracks on stbd and port sides. The hollow masts have solid wood inserts at key points so possibly where the break occured. Considering the stresses, the location of the break is completely logical. Want to know about length of scarfs, whole new top section.
Tom

[Dan McCosh]

Well, box-section masts are usually assembled with the sides scarfed with 12:1 scarfs. A repair would be the same. It sounds as if you have a compression failure on the back, which would mean taking out a section. It could be that the simplest solution would be a new top section, rather than an additional four scarfs. It's also best to stagger the scarfs so that they aren't all in the same place.

[Jay Greer]

Replacing the upper section of "Bright Star's" main mast was the choice that I made last year. I started at an existing scarf and carefuly removed wood down to the glue line on all four sides. I constructed a box butt block to allow for clamping down on the scarfs. The block was tapered on its inside to allow the mast to flex at that point. It was a tedious job, the worst part being cleaning up the old scarfs. The job required the use of my full arsenal of rabbet planes
plus a set of new planes that are called "Bunny Planes".
http://www.hartvilletool.com/product/11571
The most important part of the job was constructing a proper spar bench in order to glue up the scarf and new section. Taking the time to construct a proper bench is well worth the effort. If I can be of any assistance do not hesitate to ask.
Jay

http://im1.shutterfly.com/media/47b8d835b3127ccec409239bfedd00000020O00QYsmrNy5bsQ e3nwg/cC/f%3D0/ps%3D50/r%3D0/rx%3D550/ry%3D400/

[hallaquila]

Thanks guys,
Jay, your mast looks much like mine. Yeah, you're confirming what I expected, that is, to replace the entire top section rather than trying multiple scarfs. Thanks for the feedback. I'll post on progress.
Tom

[Jay Greer]

http://im1.shutterfly.com/media/47b8d835b3127ccec40898571fa800000020O00QYsmrNy5bsQ e3nwg/cC/f%3D0/ps%3D50/r%3D0/rx%3D550/ry%3D400/
Note that the side scarfs are at a much different posistion than the fore and aft stave scarfs are. This is where the nightmare of cleaning out the old wood required the "bunny planes".
Jay

[hallaquila]

Right, Jay,
That's the way my mast is built. Can't find that kind of sitka spruce at Home Depot or Lowes.
Tom

[Jay Greer]

Are you in need of a supplier of spruce?
Jay

[redbopeep]

....plus a set of new planes that are called "Bunny Planes".
Jay



Those sounded so cute I had to go take a look. I've seen something like these before--very useful.

:)

[hallaquila]

Jay,
For sitka spruce, you may have what I need in your backyard. There is an exotic wood dealer in Annapolis. I bought a 6'-8' section for a minor repair a couple years back. Expensive then, I recall. I'm sure it's a lot cheaper in your neck of the woods. Have a dealer in mind?
Tom

[Jay Greer]

Rather than paying freight across the country, look for a wood supplier that deals with custom aircraft builders in your neck of the woods. Otherwise, Eden Saw Lumber here in Port Townsend can supply your needs for spar grade sitka spruce.
Jay

[Raka025]

Replacing the upper section of "Bright Star's" main mast was the choice that I made last year. I started at an existing scarf and carefuly removed wood down to the glue line on all four sides. I constructed a box butt block to allow for clamping down on the scarfs. The block was tapered on its inside to allow the mast to flex at that point. It was a tedious job, the worst part being cleaning up the old scarfs. The job required the use of my full arsenal of rabbet planes
plus a set of new planes that are called "Bunny Planes".
http://www.hartvilletool.com/product/11571
The most important part of the job was constructing a proper spar bench in order to glue up the scarf and new section. Taking the time to construct a proper bench is well worth the effort. If I can be of any assistance do not hesitate to ask.
Jay

http://im1.shutterfly.com/media/47b8d835b3127ccec409239bfedd00000020O00QYsmrNy5bsQ e3nwg/cC/f%3D0/ps%3D50/r%3D0/rx%3D550/ry%3D400/

Nice place to work Jay - a bit jealous in Arkansas.