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Old 05-05-2009, 14:06   #1
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cranse iron removal

I have some rot in the bowsprit of our Tashiba 36. The bowsprit forward of the the cranse iron is composed of approx 5-6 layers of laminated wood. Each layer is about a quarter inch or so wide. The second layer from the port side is rotten back to and under the cranse iron.

I planned on removing the rotten wood and epoxying in a filler piece.

I removed the forestay, bobstay, whiskerstays, and four small screws that hold the cranse iron in position. However, when I tapped and later hammered (using a wood block to protect the cranse iron finish) on the cranse iron, it did not budge.

Anyone have any experience in removal to share?

Anyone have problems with my plan of repair versus constructing a totally new bowsprit?
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Old 05-05-2009, 14:28   #2
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I would strongly suggest if your going to do the work to just build a new sprit. It's not that hard of a job and it IS a major part of your rig. Should your repair fail your mast could come down.

I went through the same decision making process a couple of years ago and after some gentle coaxing by a boat builder friend I built a new sprit. I have no fear that my repair might not survive a storm or contribute to the mast coming down. It survived IKE so it WAS a good choice...........m
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Old 05-05-2009, 18:05   #3
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'Sounds Fishy to Me!

I'm not a wooden boat builder by trade but I did stay at a Holiday Inn Express last night!

That said, I am assuming you mean the fitting at the end of the bow sprit and not the gammon iron--being the fitting that wraps the sprit at the prow. The traditional way to install/remove a cranse (or "cranze" for some in the UK) iron is by heating it, in some cases (if it is in fact Iron or Bronze) nearly red hot, at which point it will expand enough that you can remove it. Doing that while it's on the sprit can be something of a problem but if you wrap the timber with glass fibre insulation and then a number of layers of aluminum foil, you should be able to train the flame from a tourch on the metal and get it pretty hot without damaging the timber. The wood is, itself, a good insulator so other than a little discoloration under the band, it shouldn't be much of a problem. Once it is hot however, you'll need to be ready to move quickly with tongs and a mallet to knock it loose.

If the foregoing is too "scary", you can also cut through one side of the band with a drummel cut-off wheel, expand it a little to get in off the sprit, and then take it to a machine shop and have them do a full penetration weld to rejoin the edges. You'll still have to do the heating trick to re-install it, but that's not so difficult.

The repair of the Sprit is pretty straight forward. Dispite popular misconception, a bow-sprit is a compression member, and is rarely subjected to much bending. Accordingly, you can grind out the damaged area and make a "fish" of teak or oak to fill the resulting hole. Thoroughly "glue" that in place with epoxy and, if you have any doubt about the snugness of its fit, add a couple of 1/4" lag screws driven through pre-drilled pilot holes and then cut off flush with the surface as drift pins. Sand the whole business smooth and finish with epoxy. Then re-heat your cranse iron, slip it in place, and wrap it with a rag soaked in cold water to shrink it in place and you're good to go. In future, be sure your varnish-work is maintained on the Sprit, particularly in the vicinity of the edges of the cranse iron.

FWIW...

s/v HyLyte
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Old 05-05-2009, 19:05   #4
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The repair should work fine as long as you remove all rot. Use a router to remove that plus a little more and prepare the oak batten for a good (not loose) fit. Plain mixed epoxy: pre-wet both parts, wait 10 minutes and next wet it out again and assemble.

cheers,
Nick.
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Old 05-05-2009, 20:59   #5
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The cranse iron in question is stainless steel. I am concerned that heating it would result is an unsightly discoloration. Is that an issue?

How much heat would be needed, would a MAP gas torch supply enough heat?
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Old 05-05-2009, 21:46   #6
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Like Hylyte wrote, cut it so you won't burn the wood and bring it to a machine shop to fix it. For putting it back on later, it will discolor but that can be fixed with acid and polishing; ask the machine shop for instructions and a little of that acid they use for that (they use it for the weld beads). I don't know how important that tight fit is... you could have it enlarged a bit??

For heat, fire up the charcoal bbq and put it in there just like you see in the movies ;-)

cheers,
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Old 06-05-2009, 06:09   #7
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Sparty--

If the cranse "iron" is actually polished stainless, then the odds are it was just pressure fit in place with a mallet and all the may be holding it is expansion in the timber due to moisture penetration throught the damaged area and perhaps some surface adhesion from varnish having migrated between the "iron" and sprit due to capillary action. If so, you should be able to heat it up enough with nothing more than a heat gun set on low/medium. To protect the wood, use some woven fiber-glass cloth wrapped around the sprit with a layer or two of aluminium foil held in place with a few wraps of monel seizing (mousing) wire. It won't get hot enough to discolor the stainless but the fitting will expand and the heat will soften any varnish adheasion, and you'll be good to go.

Frankly, given where the piece is located, a little discoloration isn't likely to be noticeable but if you're concerned about it, some jewlers rouge on a drummel polishing wheel does wonders for stainless.

FWIW...

s/v HyLyte
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Old 06-05-2009, 06:48   #8
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Here is a discussion about your issue:

Removing the cranse iron [Archive] - The WoodenBoat Forum
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