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Mast Crack Repair?

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JimV
Deckhand

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USA
20 Posts

Initially Posted - 12/21/2015 : 13:46:29

I'm new to the association here, I just bought a 1980 Catalina 25 short rig this fall. While trying to replace my old cast aluminum spreader brackets with SS ones the other day, I discovered that the lower bolt seized to the compression tube inside the mast. I didn't know that's what had happened until I tried to move the bolt out with a hammer and obviously too much force. You can see the end result in the pictures, does anyone have advice on the best way to repair this short of replacing the whole mast extrusion?

Thanks a ton!

Jim
Eugene, OR
"Caerulea" - 1980 C25 SR/SK #1720

DavidCrosby
Navigator

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USA
242 Posts

Response Posted - 12/21/2015 : 14:23:42

I would suggest having someone weld the crack closed. I had a vertical crack in a mast (not a Catalina) and had it welded with no ill effects.

I would say that is the nice thing about a trailerable boat. Towed the boat and mast to the welder and within a matter of minutes the problem was solved.

David Crosby "Small World"
'02 C250 WK #614

Peregrine
Admiral

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830 Posts

Response Posted - 12/21/2015 : 20:08:13

I agree the mast can be welded, well... it's not welding with aluminum, never the less it can be "welded".
When you go to put the spreader socket and shroud cleats back on ask what bolt or rivet can be safely used. I don't want to advise on this.
My guess is the bolt was steel and expanded with corrosion splitting the mast. Steel and aluminum really don't like each other.

John Gisondi
Peregrine #4762

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islander
Master Marine Consultant

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Response Posted - 12/22/2015 : 08:16:54

Yep, I think welding is your only choice if you don't want to replace the mast. Welding aluminum is difficult for many welders so find one that has lots of experience with aluminum.

Scott-"IMPULSE"87'C25/SR/WK/Din.#5688
Sailing out of Glen Cove,L.I Sound

JimV
Deckhand

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Response Posted - 12/22/2015 : 09:04:19

Thanks everyone for the advice.

I found a local shop that welds on masts for the local boat yard and they said they could weld it, so I'm going to go that route.

I got a quote of just over $1500 delivered from CD for a new extrusion only, no holes for hardware or slug slot, etc. So I'm hoping that the weld does the trick!

The bolt was SS and the compression tube was aluminium. I got the SS spreader bracket kit from CD and they included a tube of Marelube which is supposed to prevent the corrosion that occurs between SS and aluminium.

Jim
Eugene, OR
"Caerulea" - 1980 C25 SR/SK #1720

Edited by - JimV on 12/22/2015 09:05:02

oldengineer1949
1st Mate

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USA
75 Posts

Response Posted - 12/23/2015 : 08:53:39

Oh by the way, welcome aboard Jim!

Al and Bernadette, "Pualani Nui", '82 C25 SR/SK, homeport MCB Quantico

bigelowp
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Response Posted - 12/23/2015 : 12:10:53

Yes, the mast can be welded and as others have commented find a welder who welds aluminum on a regular basis as it required special skill and knowledge. One other option is check to see if anyone is parting out their boat that may have a mast OR check with local boat yards, who often have masts thy would love to get rid of -- and they will be much less than @$1,500.00

Peter Bigelow
PO - C-25 TR/FK #2092 Limerick
Rowayton, Ct
Port Captain: Rowayton/Norwalk/Darien CT

DavidBuoy
Admiral

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707 Posts

Response Posted - 12/24/2015 : 05:38:15

I've seen plenty of used C25 masts on the market. I don't think I would feel good knowing that repair is up there but that's me. I wonder if a sleeve would work?

Captain Rob & Admiral Alyson
"David Buoy"-1985 C25 SK/SR #5053

islander
Master Marine Consultant

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4038 Posts

Response Posted - 12/24/2015 : 09:48:35

quote:
I've seen plenty of used C25 masts on the market.

So have I at various times but finding one that is very close to where you live is the problem. Shipping a mast is very expensive. If you do find one within your area at the time you need it, Well that's unlikely and if you did just how do you strap a mast to the roof of your car. Not happening so a trailer/truck rental would be needed. The costs add up. If it helps here is a hit in Conn.http://newhaven.craigslist.org/bpo/5360647712.html

Scott-"IMPULSE"87'C25/SR/WK/Din.#5688
Sailing out of Glen Cove,L.I Sound

Edited by - islander on 12/24/2015 10:10:56

JimV
Deckhand

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Response Posted - 12/24/2015 : 17:24:25

I'm on the west coast (Oregon) and a lot of the used masts that I can find seem to be on the East Coast. That combined with budget constraints has me considering having the crack welded but I'v been looking at this vertical crack in my mast and wondering what part of the mast caries the most stress.

If you were to take a cross section of the mast where is the strength of the mast, I would think that it would be the front and back where the mast curves and makes the corners. It seems like the middle of the side of the mast would take the least amount of force.

Does anyone out there have a source showing data where the stress load is carried on a mast? It would also be interesting to know why different masts have different shapes and how that effects performance and strength.

Thanks for all the input, hope everyone is having a great Christmas Eve!

Jim
Eugene, OR
"Caerulea" - 1980 C25 SR/SK #1720

Steve Milby
Past Commodore

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5932 Posts

Response Posted - 12/24/2015 : 18:03:10

The load on a mast is straight down to the deck, assuming it's tuned correctly. A mast that is in-column (straight), with the rig tuned so that there is little or no significant movement to it, has very little chance of breaking. If you look at the system of stays, you can see that it's objective is to prevent the mast from bending out-of-column, either fore-and-aft, or laterally. If the upper or lower stays are too loose and allow the mast to bend out of column, it can break. I know of one instance in which a C25 mast snapped because the rig was way too tight. Some masts, primarily fractional rigs, can be bent, but the rig on a C25 should not be.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

islander
Master Marine Consultant

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4038 Posts

Response Posted - 12/25/2015 : 07:17:44

I agree with Steve. The mast itself doesn't take on the load when sailing. All of the stays do that. Most of the load on a mast is straight down and that is caused by the tension of the stays. I doubt that the weld will affect the strength of the mast. A proper weld is stronger than the surrounding material. An improper weld isn't. As suggested above, Find a good welder with experience in welding aluminum.

Scott-"IMPULSE"87'C25/SR/WK/Din.#5688
Sailing out of Glen Cove,L.I Sound

Edited by - islander on 12/25/2015 07:23:57

Peregrine
Admiral

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Response Posted - 12/25/2015 : 12:51:59

"The load on a mast is straight down to the deck, assuming it's tuned correctly."

Please understand, that statement can only be true on a calm day with the sails down.

With both the main and jib up and under sail the mast has tensions coming from different directions as each shroud and the fore and aft stays are under different loads.
For instance on a starboard tack the port shrouds are under load the starboard shrouds are slack. If there is too much sag in the fore stay and you compensate with an adjustable back stay then the forward, port lower shroud has more tension than all rest.
Think about what the mast goes through when you come off a wave hard sailing close to the wind.
So...
IMO a mast with significant flaw i.e. a split, could fail.

http://www.sponbergyachtdesign.com/articlesengineering.htm

Having said that I think a proper weld and preventing the hardware from corroding is a fine way to go.

John Gisondi
Peregrine #4762

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Edited by - Peregrine on 12/25/2015 12:56:38

Steve Milby
Past Commodore

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Response Posted - 12/25/2015 : 14:45:32

quote:
Originally posted by Peregrine

[font=Comic Sans MS][size=2][navy]"The load on a mast is straight down to the deck, assuming it's tuned correctly."

Please understand, that statement can only be true on a calm day with the sails down. With both the main and jib up and under sail the mast has tensions coming from different directions as each shroud and the fore and aft stays are under different loads.

Regardless of whether the sails are up or down, think about the function of the stays. The forestay, backstay and upper shrouds hold the top of the mast in a fixed position fore and aft, and laterally. The four lower stays hold the mid-section of the mast in a fixed position fore and aft, and laterally, so that the mid-section of the mast can't bend out of alignment with the top of the mast. There is, of course, a small amount of stretch in the various stays, but it is so slight as to be insignificant to the overall strength of the rig, especially when the rig is correctly tuned. Regardless of how the individual stays are loaded, the loads on the mast are still being transmitted straight down, in column, to the deck, because all the various stays are holding the mast in column.

In the Sponberg link that you provided, the author says, "We can check our calculations by adding together all the tensions in the shrouds on one side of the boat and comparing the result to the compression in the mast. They should be equal and opposite...." When the tensions provided by the stays are equal and opposite, to the compression in the mast, the mast will stay in column.

Other sailboats don't have two forward lowers and 2 aft lowers, like the C25, and what you are saying is true of other types of rigs, but not of the C25.

quote:
For instance on a starboard tack the port shrouds are under load the starboard shrouds are slack.

You have that backwards. On a starboard tack, the starboard shrouds are under load and the port shrouds are slack.

quote:
If there is too much sag in the fore stay and you compensate with an adjustable back stay then the forward, port lower shroud has more tension than all rest.

A backstay adjuster on a boat with a masthead rig, like the C25, enables you to tilt the whole rig forward when you're sailing downwind, because a certain amount of forestay sag powers up the jib, and when you ease the tension on the backstay adjuster, you create sag in the forestay. When the rig is tuned properly, tensioning the backstay pulls the top of the mast aft very slightly, and allows the midsection of the mast to bend forward very slightly (but not enough to significantly affect the strength of the mast). The slight forward bend in the midsection of the mast pulls the fabric in the middle of the mainsail forward, and depowers the mainsail, which helps to reduce the angle of heel when sailing closehauled. Tilting the mast does in fact change the tensions on the various stays, and it bends the mast ever so slightly, but the stays still hold the mast essentially in column, and they should be adjusted so that it can't be bent so far out of column as to materially affect it's strength.

quote:
Think about what the mast goes through when you come off a wave hard sailing close to the wind.
So...
IMO a mast with significant flaw i.e. a split, could fail.

http://www.sponbergyachtdesign.com/articlesengineering.htm

My main concerns with the repair of this mast are (1) that the cross-sectional shape of the mast be restored. If the mast has it's oval shape down to a certain point, and then at that point it has a bulge or a crease, that will be a weak spot. (2) that the weld is strong enough so that it won't crack again under load. I've never seen a mast crack like that, and you have to wonder if it cracked in the first place because of some flaw in it's original manufacture that might re-appear somewhere else, if you fix it.

Even with those reservations, I think I would discuss those concerns with the welder, and then have it repaired, and then sail it overpowered and rail down, close to your marina, in 15 kt winds, to test it.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

Edited by - Steve Milby on 12/25/2015 15:40:39

Peregrine
Admiral

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830 Posts

Response Posted - 12/25/2015 : 15:20:59

"Other sailboats don't have two forward lowers and 2 aft lowers, like the C25, and what you are saying is true of other types of rigs, but not of the C25".

Really?

The tensions can only equal when not sailing and there is no wind.
Yes I managed to get starboard port reversed but the principal is the same on either tack.

The statement;

"The load on a mast is straight down to the deck, assuming it's tuned correctly."

Is inaccurate.

John Gisondi
Peregrine #4762

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Steve Milby
Past Commodore

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Response Posted - 12/25/2015 : 15:53:31

quote:
Originally posted by Peregrine

"Other sailboats don't have two forward lowers and 2 aft lowers, like the C25, and what you are saying is true of other types of rigs, but not of the C25".

Really?

The tensions can only equal when not sailing and there is no wind.
Yes I managed to get starboard port reversed but the principal is the same on either tack.

The statement;

"The load on a mast is straight down to the deck, assuming it's tuned correctly."

Is inaccurate.

Look at the article that you posted. The author says, "We can check our calculations by adding together all the tensions in the shrouds on one side of the boat and comparing the result to the compression in the mast. They should be equal and opposite...." The author goes on to say that, " The load from the main is spread uniformly along the full height of the mast, and the load from the jib acts on the mast where the head stay is attached . (i.e. the top of the mast)" Since the mast tip is restrained by the shroud from falling off to leeward, then the load caused by the jib is transmitted straight down the mast, to the deck. The same is true of the load caused by the mainsail. Both loads are directed down the mast in the form of mast compression. A mast that remains in column can withstand tremendous forces. If it's allowed to get too far out of column, it will snap.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

Edited by - Steve Milby on 12/25/2015 15:57:17

Peregrine
Admiral

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Response Posted - 12/25/2015 : 16:50:26

For mathematical calculations that is correct but it assumes dead flat water and perfectly constant wind speed.
In the real world masts bend with each wave and each puff.

The following explains it pretty well.

"Because rig tension causes the mast to become unstable or �bendy,� the right amount of pre-bend is critical. A good way to understand this is to use the following thought experiment. You are hiking along a beautiful mountain trail, and you come across a stream that you want to cross without walking through it. You find a wooden board long enough to cross the stream and support it on the banks on either side of the stream.

As you walk on the board above the stream, it bounces up and down. Now, envision hanging a heavy weight from the midpoint of the board. Naturally, the board is going to bend downward. The heavier the weight, the more it will bend. Now, when you walk across the board, the board is much more stable, and there is less bouncing. The reason for this is that by hanging a weight on the board, you are �preloading� the board. Because the board is preloaded, the oscillating, vertical load caused by your walking across the board has less impact on the board. The heavier the weight that you hang from the board, or the greater the preload, the more this is true.

Without applying pre-bend to a mast under load, it will behave much like the board placed across the stream. As a boat moves through the water, it is periodically slowed by waves. Each time the boat is slowed, the force of the sail pushing forward on the mast increases, causing the mast to bend. When the boat picks up speed, the force of the sail against the mast is reduced, and the mast straightens up. As the boat moves through the ocean, the mast is constantly in motion, either bending when the boat pushes into a wave or straightening as the boat accelerates back to full speed."

Enough for now the second round of deserts just came out.

John Gisondi
Peregrine #4762

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Edited by - Peregrine on 12/25/2015 16:56:25

Steve Milby
Past Commodore

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Response Posted - 12/25/2015 : 17:43:00

With regard to mast prebend, I don't think we're really saying anything very different. As I said earlier, an adjustable backstay that is tensioned for sailing closehauled in a breeze will normally have a slight bend in the mast, but the C25 mast is not what is generally considered a "bendy" mast, and the amount of bend is not great, perhaps 4-5 inches. When the backstay adjuster is eased, the amount of bend in the mast decreases, and that's what causes an increase in forestay sag. If you don't have a backstay adjuster, then you have to tune the rig so that it will sail closehauled well, but, you won't be able to power up the rig by inducing headstay sag when you head downwind.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

Edited by - Steve Milby on 12/25/2015 17:44:32

Peregrine
Admiral

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Response Posted - 12/26/2015 : 17:58:51

I know we got a little far into the weeds with load directions etc, when Jim just wants his mast fixed.
My point about forces on the mast being other than just straight down is when you inspect your mast...

You do inspect your mast right?

...consider that there will be considerable lateral forces on the mast.
Inspect all hardware that is attached and any and all penetrations of the mast for corrosion, cracks or just discoloring.

John Gisondi
Peregrine #4762

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britinusa
Web Editor

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Response Posted - 12/30/2015 : 12:57:45

I didn't see any mention of the stress in mast compression when the halyards are loaded.
If the mast was held up with loose shrouds & stays, ie. low compression due to loading, but the main halyard was loaded, that's a good bit of compression (so much so that many of the modern racing rigs use a device that allows them to slacken the haylard slightly once the sail is raised to position)

ie. The main halyard compresses the mast along it's length.

Also, I'm not certain that adding a weight to bridge, preloading it, is the reason for stability, it's the reduction in change of weight. ie. Hang a Ton off the middle of a bridge (capable of carrying it) and then walking a 100lb person over the bridge will be a much smaller change in loading than the same bridge without the preloaded weight.

But then I tie my boat close enough to the dock that I don't need a bridge!

Paul

Joint Decision. (Sold)
PO C250WB 2005 Sail # 841.

Moved up to C34 Eximius

Updated August 2015

JimV
Deckhand

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USA
20 Posts

Response Posted - 12/30/2015 : 19:14:12

Well, I went with the weld job. Came out good and I'm pretty sure it will hold. Thanks for all the advice!

Have a great New Year

Jim
Eugene, OR
"Caerulea" - 1980 C25 SR/SK #1720

Edited by - JimV on 12/30/2015 19:15:03

britinusa
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Response Posted - 12/31/2015 : 04:36:25

Great pic of the action!

How soon before you get her out on the water?

Paul

Joint Decision. (Sold)
PO C250WB 2005 Sail # 841.

Moved up to C34 Eximius

Updated August 2015

JimV
Deckhand

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20 Posts

Response Posted - 12/31/2015 : 09:16:29

She won't get her bottom wet until April when our little pond has enough water in it to sail. Plus, I'm in the middle of a long list of projects that I need/want to do that won't be done until sometime in March.

Jim
Eugene, OR
"Caerulea" - 1980 C25 SR/SK #1720

Steve Milby
Past Commodore

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5932 Posts

Response Posted - 12/31/2015 : 09:35:24

That looks like a good repair. Were they able to dress the repair in some way to restore it's appearance? When the mast on my C22 was repaired, they refinished it with something that made the repair virtually invisible. I'd be interested in knowing what they used on yours.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

bigelowp
Master Marine Consultant

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1813 Posts

Response Posted - 01/03/2016 : 11:06:19

The repair appears -- and I am sure is -- of high quality. That said, keep an eagle eye on the mast area repair going forward to be on the safe side, especially if the mast stays up all year.

Peter Bigelow
PO - C-25 TR/FK #2092 Limerick
Rowayton, Ct
Port Captain: Rowayton/Norwalk/Darien CT

JimV
Deckhand

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Response Posted - 01/03/2016 : 15:47:16

The welder said he welded on quite a few masts with similar damage. He didn't really even give it much thought just went to fixing it and twenty minutes and forty bucks later it looked great.

I'm in the process of stripping off the old white paint and will be repainting it white again. It should make the repair work nearly undetectable.

I'll be taking the mast down at least once a year and at that time I'll clean the welded area and should be able to detect any stress cracks in the paint around the welded area.

Jim
Eugene, OR
"Caerulea" - 1980 C25 SR/SK #1720

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