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Old 21-05-2008, 12:11   #1
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Need advice - wood rot on my main mast

My main mast is constructed of sitka spruce, I have found an area aprox. 10" long, and maybe 3/4" wide of dry rot, it is right on the corner of the rectangular shape of the mast maybe 3 feet up from the base. The circum of the mast at that spot is aprox. 27". Obviously I am concerned because it is on the mast, any suggestion on how I would do the repair. Should I dig it all out and fill with some sort of epoxy, or maybe replace with a pc of sitka and epoxy over that? Is this going to compromise the strength of the mast? It is just below a winch on the mast and looks as though water has been getting in where the winch is attached to the mast. I have looked over the rest of the mast verycarefully, everywhere else is solid, no softness.Thanks in advance for any advice.
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Old 21-05-2008, 13:27   #2
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Mike,

You can scarf in a new peice of sitka spruce and if done properly is as good as the day the mast was built. The key is to cut a long low angle cut so the scarf surface area for bonding is as large as possible. Epoxy works very well as your bonding agent. Do not just fill the area with epoxy, you will have no real strength.
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Old 21-05-2008, 19:00   #3
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mast repair

We did that to a mast in the Marshall Islands. Once you shape the areas for the scarf joint, you want to use CPES (Clear Penetrating Epoxy System) to saturate the surfaces. It goes in like water, really penetrates and strengthens the wood. It will kill any of the rot critters you may have missed and prevent any from trying to grow there again. Give a day to set up, and then you put your scarf joint together with a structual epoxy. CPES is manufactured by Smith & Co, and their products are carried by a number of stores. There is a mail-order one in Seattle called "Rot Doctor" that has a good website and lots of good literature. I've been using CPES since the '70s, and it really works well. I use on the boat, the house, its my favorite chemical for getting rid of rot, permanently. By the way, I'm a reliability engineer.
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Old 21-05-2008, 20:48   #4
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A 2nd vote for CPES although System 3 also has a similar rot treatment. Do your treatment and let it dry for a few days. Also treat the piece of wood you intend to use in the scarf joint. Then use an epoxy adhesive meant for wood to glue up the joint. Probably better to stay with one brand - like T88 if you used System 3 or Smith and Co's Wood Glue if you used CPES. If, like me, you can't make the scarf joint angles mate perfectly, put a dab of putty made from sawdust and the epoxy glue at any gaps. The putty is much stronger than a blob of glue across a gap.

Carl
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Old 21-05-2008, 23:10   #5
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A good structural scarf joint would be around an 8 to 1 ratio. My only question is in precoating the area to be glued. This is usually done on porous wood to prevent resin from leaching out of your adhesive mixture. There are powder additives that can be added to thicken the mixture, improve it's properties and also make it an effective gap filler for a less than perfect scarf joint. You do not want your initial sealing mixture to cure before gluing in the scarf otherwise you will get a poor bond. If you remove all the rot you could just use straight epoxy for this sealing coat. Mix in a little wood flour to your glue mixture to match if your mast is varnished. Don't clamp it to tight. You don't want to squeeze all the epoxy out.
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Old 22-05-2008, 00:16   #6
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I agree with all above but particularly wet on wet epoxy. Start early in the day with your pre made scarf ready. Saturate with many coats of your penetrating anti rot mix. (some brands specify up to 10 coats) You just keep slapping it on as it soaks it up. Lastly with a joint filler additive to normal epoxy, clamp up your scarf.
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Old 22-05-2008, 03:01   #7
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The gluing principal is to provide as much glue as the joint will absorb, in order to prevent glue-starved joints.

Coat the two pieces (mast & repair insert) with straight epoxy and let set for only 5 or 10 minutes.
Then recheck, and apply more epoxy until dry spots no longer appear (may take several pre-wetting coats)

Before the epoxy sets up, apply another coat of epoxy mixed with filler to a syrupy consistency. Apply the mix to both mating surfaces and allow it to set for 10 to 15 minutes.

Mate the insert into the mast. Now apply the clamps and pressure. When using c-clamps, use small blocks of wood to help spread out the pressure of the clamps, and use at least two clamps, one on either side of the "center nail".
Do not apply too much clamping pressure; as you do'nt want to force all the epoxy out of the joint.

Allow repair to fully cure (5 to 7 days?), prior to drilling (for hardware) or loading .
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Old 22-05-2008, 04:12   #8
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Thanks a million, I think I have a plan...
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Old 22-05-2008, 05:04   #9
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good one Mike.....and I recon it will work , let us know how it goes....

cheers

ps that is the best thing about this site.....
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Old 22-05-2008, 06:39   #10
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Timely advice for me also as I am starting work on my original (25 yr old masts) wooden masts (Both 15m long)

I have a little bit of rot near the base and will fix as advised.

The question for me is that there is also a SPLIT at the base about 8 inches long on the Aft. And another one at the lower spreader about 9” on the Fwd

My plan is to strip the complete masts down to bare wood, inspect and scarf in repairs as explained above then treat whole Masts with CPES.

My question:

Should I also be wrapping those splits with multi-directional fibreglass cloth to give those areas strength?

After the paint is removed…..If I find a number of small cracks everywhere should I consider wrapping the whole masts in fibreglass?

Thanks for any advice
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Old 22-05-2008, 11:49   #11
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Pelagic, because you have a hollow laminated mast, I would suggest scarfing in a section to the damaged piece. Do not wrap it with fibergalss. This is a guaranty of future problems. Looking at your photos, I would hand plane, and chisel the effected areas, then scarf in a section. I also feel 12:1 is a far better scarf ratio. I have heard different ideas, and do not totally disagree with 8:1, but for my own boat, I have always used at least 12:1.
When you re-drill you holes for wiring etc., make sure you put penetrating epoxy in those holes as well. Fortunately cracks with the grain are not a big deal, but since you have the spar unstepped, you may as well take care of it. In fact, if it were not for the damage, and what appears to be rot, around the holes, I would just recomend epoxy and clamps on the split.
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Old 22-05-2008, 11:59   #12
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Lots of good advice here. Thanks to knowledeable forum members. I went through this procedure and we rebuilt a friends mast in the mid 80s using the same methods described except his mast was coming apart at the seams. It was a great fix using epoxy and lasted many years.
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Old 22-05-2008, 12:04   #13
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Quote:
Originally Posted by Island Mike View Post
It is just below a winch on the mast and looks as though water has been getting in where the winch is attached to the mast.
Your diagnosis of the winch being the source of the problem may be right on the money.
If you haven't already... also might consider removing the winch and reinstalling after over-drilling the mounting holes and filling them with extended epoxy - consider the aluminum powder filler if you're going to thread the bolts into the epoxy.
Refer to the Gougeon site for details.

Pelagic: those cracks/splits will contain contaminants and possible rot spores. My theory for repairs like these is to take out more wood than you think is necessary and add back trustworthy timber. For the crack you picture I would definitely take a skillsaw to it add back a nice fat replacement section. IMNSHO just squeezing glue into the crack and clamping ' might be sufficient - but I'd worry on it.
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Old 22-05-2008, 12:35   #14
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tom, I should clarify, had I felt repairing the crack with epoxy and clamps was the correct method, I agree, it should be cut to clean wood, and possibly a filler piece inserted. Even if contaminates are not present, the epoxy will Bond far better to a fresh cut.
I would also add, maybe stating the obvious, that if you scarf a piece in, make sure you are using the same species, and a piece that is clear, and straight grained. Also, make a scarf jig. This is no hard to do, and will provide a much better scarfe.
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Old 22-05-2008, 13:05   #15
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Thanks for all the knowledgeable advice as this is very new to me.

About finding the same species of wood… I think that will be the challenge here in the Philippines.

Nobody is quite sure what the masts are actually made from and I have no idea how to go about determining that.

1 Any ideas or suggestions on how to determine the species or “family” of wood?
2 How much latitude do I have on just finding a similar weight and grain to use?
3 What are the dangers in getting this wrong?
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