Ok how screwed am I?

[Terra Nova]

This repair can be done in the water. But there will be lay day charges for the mast while it is out, besides the charges for unstepping and restepping it.

From here it looks like the tabbing has also separated from the bulkhead.

[ZULU40]

Hard to see that if the step is corroded to bits, the mast is not affected too. It might not look too bad until you get it out, but I think then you are going to find that the last 2 or 3 inches are shot. But all is not lost

Just cut off the affected part of the mast, I marked mine out using an old chart wrapped around the mast, in that way the mast is cut square. I used a cutting wheel on a disk grinder, and sliced off the corroded aluminium, I recall it being the last 68mm.

Now you have to make or have made a new step the best you can do is use stainless steel about the same thickness as the step you are replacing. It needs to have a plug on the bottom that makes up that 68mm lost, and around that plug it needs the guides to support the mast and control its position.

The step is used to control the incline of the mast where, you dont want it pointing forward, usually theres some instruction or advice from the builders/designers. So it will need slots in it, allowing it to move for and aft a bit.

You best think about replacing the fasteners too, again I went with stainless, but mine could go through the hull and into the lead of the keel below it. I upped the diameter and length as that seemed prudent.

The images are of the original step in and out of the boat, and the new one before bolted in.

[El Pinguino]

Originally Posted by er9

yeah as far as i can tell my bulkheads are also not tabbed to the floor only the hull sides above the floor level.

wow! 10cm is a LOT of movement.

better photos will come in the morning. its 3am and cant sleep or take pics...too dark.

OOOOOOPS....typo alert ....1 cm!

[Terra Nova]

Originally Posted by ZULU40

...Just cut off the affected part of the mast...

Not so fast!

By cutting off the base of the mast, and then raising the actual mast step, you create a "hinge" point. If a sufficient amount of mast is removed the new, taller, mast step wants to topple over from side pressure. So there is a limit to this "just cut it off."

At some point sleeving the base of the mast is preferred.

[ZULU40]

Originally Posted by Terra Nova

Not so fast!

By cutting off the base of the mast, and then raising the actual mast step, you create a "hinge" point. If a sufficient amount of mast is removed the new, taller, mast step wants to topple over from side pressure. So there is a limit to this "just cut it off."

At some point sleeving the base of the mast is preferred.

Im not proposing cutting off 2ft of mast, its just a few inches, and you can see by my examples the step has a nice base to it, and sides for the mast to sit in. The sides are important though because a mast can jump around a bit at sea.

[Terra Nova]

Originally Posted by ZULU40

...sides for the mast to sit in...

...trap water at the base of the mast. The mast step should fit inside the mast, with a drain hole in the mast at the top of the step.

[ZULU40]

Originally Posted by Terra Nova

...trap water at the base of the mast. The mast step should fit inside the mast, with a drain hole in the mast at the top of the step.

Its the same thing
even in your example condensate can collect inside the mast, and guess where it goes

Notice the sides of the step are open

Actually the problem with all these designs in the first place was that even small amounts of bilge water would get between the galvanically dissimilar metals and cause corrosion

At least it wont have that problem anymore.

[Terra Nova]

Originally Posted by ZULU40

Its the same thing
even in your example condensate can collect inside the mast, and guess where it goes...

...through the drain hole I mentioned.

[Suijin]

Originally Posted by ZULU40

Now you have to make or have made a new step the best you can do is use stainless steel about the same thickness as the step you are replacing. It needs to have a plug on the bottom that makes up that 68mm lost, and around that plug it needs the guides to support the mast and control its position.

Stainless may not be the best option, given that the mast is aluminum. In the bilge environment it's just asking for dissimilar metal corrosion even if you slather the mating surfaces with Tef-gel. When he gets the base out he needs to evaluate what's bolted to what and how to design a replacement that will do as little as possible to promote corrosion.

I don't think he's going to be wanting to move the foot of the mast base forward or back. The Mariner is not exactly a racing boat. He just needs to take careful measurements before starting to dig the old base out. One of the most important, other than it's lateral position, is the angle of the base flange around the sleeve that slides into the mast. It should be level with the mast base, as much as possible, to support it around it's circumference.

[ZULU40]

Originally Posted by Suijin

I don't think he's going to be wanting to move the foot of the mast base forward or back. The Mariner is not exactly a racing boat. He just needs to take careful measurements before starting to dig the old base out. One of the most important, other than it's lateral position, is the angle of the base flange around the sleeve that slides into the mast. It should be level with the mast base, as much as possible, to support it around it's circumference.

your comments about galvanic corrosion are worthy, but we still felt the durability of SS provided best practise, ymmv

As to dimensioning. I did all that too, but the original step and fasteners were so far gone it guaranteed the step, hence the mast, was out of position by about an inch and a half too far aft. The sailmaker acting as rigger set all this right when the rig was erected, we moved the step forward, and ensured backstay and forward stay had the right tension. We examined the step and mast and found them mating exactly.

The surveyor did notice there was a spirit level on the boat when I viewed her before purchase, and knowing the step was bad, we suspected thats what the owner was chasing and that this was an ongoing problem which could only be fixed by pulling down the rig.

But that had its bright sides too as the whole thing could be properly inspected, and we did find issues that required attention, small though they were.

[BlueSlue]

Originally Posted by er9

los angeles.

much thanks. yeah im out of my league with this one. i definately need help assessing this properly.

James (Jim) Wallace is a marine surveyor based in Long Beach. He is well respected in our area and did the survey for my boat. I'll pm you his contact info.

[JPA Cate]

@er9,

Kjell Christiansen in San Diego has been recommended, as a good surveyor and all 'round good guy, here on CF. Reportedly highly competent. I don't know if he's a rigger, as well.

Thinking about this some more, with the bulkhead having popped its tabbing, something structural is clearly going on, and it may be that the poster who suggested making sure the sub flooring is still adequate may be right that that is where to begin. On our old boat, to fix our structural problem, Jim glassed in two stringers, and one sub-floor.

Ann

[er9]

Originally Posted by Suijin

Stainless may not be the best option, given that the mast is aluminum. In the bilge environment it's just asking for dissimilar metal corrosion even if you slather the mating surfaces with Tef-gel. When he gets the base out he needs to evaluate what's bolted to what and how to design a replacement that will do as little as possible to promote corrosion.

I don't think he's going to be wanting to move the foot of the mast base forward or back. The Mariner is not exactly a racing boat. He just needs to take careful measurements before starting to dig the old base out. One of the most important, other than it's lateral position, is the angle of the base flange around the sleeve that slides into the mast. It should be level with the mast base, as much as possible, to support it around it's circumference.

if the mast has to be trimmed then i'm assuming the cut base needs to be as close to a perfect/flat 90 degree angle to the mast itself? then if the step is machined well it should fit nice and flat.

measuring and trying to re-construct this base as it was is going to be a beast. not very many reference points left to get accurate measurements from. i do have half a dozen bolt holes i need to hit. how far off can a mast be from side to side / front to back and still be good to go? when all is said and done...if my new step is 3/16" off from left to right and a 1/4" front to back from its original position am i going to be ok?

i'm pretty sure i can easily meet those tolerances or better. i am a fabricator for a living but have no idea how precise this has to be.

[er9]

Originally Posted by BlueSlue

James (Jim) Wallace is a marine surveyor based in Long Beach. He is well respected in our area and did the survey for my boat. I'll pm you his contact info.

thanks got your PM

[er9]

Originally Posted by JPA Cate

@er9,

Kjell Christiansen in San Diego has been recommended, as a good surveyor and all 'round good guy, here on CF. Reportedly highly competent. I don't know if he's a rigger, as well.

Thinking about this some more, with the bulkhead having popped its tabbing, something structural is clearly going on, and it may be that the poster who suggested making sure the sub flooring is still adequate may be right that that is where to begin. On our old boat, to fix our structural problem, Jim glassed in two stringers, and one sub-floor.

Ann

Kells did my original survey, that was in san diego...i dont think i can afford to have him drive up to the marina and back. thats way out of the budget. nice guy though...

i dont think the bulkead actually popped its tabbing though, thats the confusing part. something is obviously moving but the tabbing all looks intact.

to add to the confusion maybe...under the area of the bulkhead are four massive stringers running beam to beam and two running bow to stern.
iv'e examined them the best i could and there is no signs of trauma or stress cracking that i can tell from whats visible.

some parts of this problem are very confusing.

by sub flooring do you mean a layer of wood under the teak and holly planking? if so i have none. the teak and holly floor consists of 1"thick planking just resting on top of whatever stringers and support is available.