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Old 11-11-2011, 09:10   #1
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Major Mast Step Repair - Please Advise

The main reason my new boat was so cheap it that it had a rather dire case of mast compression. It appears to be a common problem on these and the owners club details repair procedure.......


This picture is not quite exact, the mast is offset from the centre line by about and inch or so to the right....


I've cut the mast step out from above......




(The guy in the owners club carried out the repair from underneath but I reckon it's easier to make the outside good, rather than try and make the gelcoat headlining look original again)

I've rigged up a jack inside the boat to get the headlining to the correct height. From there I intend to do pretty much the same as the first picture - stainless bracket, new wooden pad etc. I'm then going to glass the mast step back in place.......

Any comments? Ideas? Things to watch out for??

I've been a mechanical engineer for the past 10 years so making sure the mast is sound is simple enough...... but my sailboat knowledge is sadly very lacking so any information would be massively appreciated!
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Old 11-11-2011, 09:17   #2
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Re: Major Mast Step Repair - Advice Please

What is the root cause of the compression? You're adding a pad under the mast step and that is fine and good but it concerns me that you're having to jack up the cabin top from inside. Is the compression post crushed? What is under the post?

I guess my question is, how is this a permanent fix?
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Old 11-11-2011, 09:31   #3
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Re: Major Mast Step Repair - Advice Please

Not sure of the root cause, what I do know is;

The mast tabernacle is not original
The tabernacle bolts are letting water in
There is already a plywood mast pad as standard - it is not in the best of shapes and needs replacing
There is no post inside, the bulkhead (or dividing wall between head and passageway) is solid timber about an inch and a half thick.

Not sure if the mast has been seriously over tightened at some point, I suspect old repair work was not done properly, it looks like someone has put expanding foam under the mast step? I thought there would be balsa or similar between the grp deck and the gelcoat headlining - there isn't.

It is going to be a permanent repair - hopefully stronger than original!
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Old 11-11-2011, 09:40   #4
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Re: Major Mast Step Repair - Advice Please

Sorry, when I was saying post I was meaning the bulkhead on which the mast step puts its weight. Can you check this 1 and 1/2" thick piece of timber where it joins the bottom of the hull? See if it is crushing down or if it what it is resting on has been crushed down.

Essentially what I am saying is that you need to check the entire string of supports on which the mast weight will fall from top to bottom.
The mast sits on the tabernacle
which sits on the step
which sits on the pad
which sits on the bulkhead
which sits on...???

Also make sure you use marine grade plywood for the pad and give it a good coat of epoxy just to be sure before reinstalling it. If the old bolts were leaking and letting water in I'd also suggest rethinking them. Were they counter sunk? What were they sealed with?
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Old 11-11-2011, 09:48   #5
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Re: Major Mast Step Repair - Advice Please

The sketch shows a "hardwood mast plate" Is this meant to act as a compression post?
If so...where does the other end (bottom) rest?
Is the edge of the plywood seen in your picture a bulk head?
Did the "plywood pad" bear directly on it?
When you jacked up the ceiling where was the movement visible i.e. between the ceiling and the bulkhead?
Can we see a picture from inside?
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Old 11-11-2011, 09:51   #6
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Re: Major Mast Step Repair - Advice Please

Edit....I guess Target9000 has already asked the relevant questions....sorry for the repeat....
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Old 11-11-2011, 09:51   #7
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Re: Major Mast Step Repair - Advice Please

I will check the bulkhead when I'm next at the boat although the compression was only present to the right of the bulkhead - possibly as a result of the bulkhead not being directly under the mast. As I say, it's a known fault with this model....

Assuming the bulkhead is sound....... is plywood better than hardwood? I was going to try and find something quite hardcore....

Not sure about the bolts, they heads were in the underside of the existing plywood - essentially making them studs..... I was thinking about doing similar only making sure that checking, resealing becomes part of routing maintenance?

Should there be a degree of flex at the point where a mast meets to boat? ie, could I bolt straight through to the stainless support plate or would that make the whole assembly too rigid?

And thank you Target, I'm sure some of this is coming under the heading of silly questions and your answers and patience are much appreciated!
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Old 11-11-2011, 09:54   #8
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Re: Major Mast Step Repair - Advice Please

If the arch supporting the cabin roof is in good shape it seems that it would be a simple matter of replacing the padding under the tabernacle. My boat is of a similar design and is beginning to show similar symptoms. Repairing or replacing the arch may be a bit more involved if it is glassed into the under side of the coach roof. Proper tunenig of the rig is important and should be checked from time to time. Over tensioning the rig can cause the hull on some boats to "banana".
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Old 11-11-2011, 09:56   #9
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Re: Major Mast Step Repair - Advice Please

Quote:
Originally Posted by James S View Post
Can we see a picture from inside?
On it

Yeah, I managed to get at least half an inch on the jack.... didn't go any further cos I was only really offering the jack in to check it worked.....

My plan is to set the headlining level (to where it originally was) and work up from there......
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Old 11-11-2011, 09:58   #10
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Re: Major Mast Step Repair - Advice Please

My only comment is I would use a aluminum bracket instead of stainless, cheaper lighter easier to work with. I think I would also us aluminum plate instead of plywood support pad.
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Old 11-11-2011, 09:59   #11
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Re: Major Mast Step Repair - Advice Please



Jack assy.....



Headlining - the small hole visible is one I drilled to mark the centre point of the mast.

Sorry about the poor quality pics, it was getting quite dark....
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Old 11-11-2011, 09:59   #12
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Re: Major Mast Step Repair - Advice Please

To echo what Target9000 says I'd also spend time determining all of the factors that have contributed to this problem. I've seen this repair implemented on a larger boat and the repair involved a lot more than returning the deck thickness/strength in the mast base area to what it was supposed to be. The compression post and it's base were also completely replaced/rebuilt and the hull was reinforced in ways that helped stabilize the chainplates and bilge to deck positions. If you didn't have oil canning, cracks/delamination or other signs of structural weakness in related structural areas then you probably don't need to go this far but it's at least worth a look so that you can have confidence in your repair long-term.

Jonathan

p.s. I posted this before seeing all of the responses,, I'll leave the post but it looks like you are already on the right track in figuring out the related structural systems, etc.
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Old 11-11-2011, 10:02   #13
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Re: Major Mast Step Repair - Advice Please

Some hard woods would be better than ply and some not as good. Just make sure whatever you use is well sealed, rot resistant, and has high radial compression resistance. If the boat was built with ply I would assume ply could probably go back in, assuming everything else is alright.

Good idea on checking in on those bolts to make sure they don't leak. Also add it to the ships maintenance log and highlight it. If you ever sell it you'll want the new owner to know its important.

Finally, there will be some flex at the mast-boat meeting point, but you don't really want that. The more rigid it is here the better. I'm assuming that the "SS support plate" that you're talking about is the new bracket in the photo above? If that is true you should be able to through bolt it but will you have room or will the bolts protrude up into the area where the mast step is? I doubt you'll have room for truly thrubolting and it wouldn't matter much anyway. By the looks of the photo, those brackets are simply to hold the bulkhead in its proper place, not to take any load themselves. I'd not worry about thrubolting.
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Old 11-11-2011, 10:02   #14
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Re: Major Mast Step Repair - Advice Please

Quote:
Originally Posted by S/V_Surya View Post
My only comment is I would use a aluminum bracket instead of stainless, cheaper lighter easier to work with. I think I would also us aluminum plate instead of plywood support pad.
Interesting...... it was suggested that I use nylon instead of wood but I was a little concerned that it would be too hard. You think not?

Ally would be easier but stainless looks prettier and metalwork is my strong point! (oooh, if only I could weld glass fibre up )
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Old 11-11-2011, 10:04   #15
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Re: Major Mast Step Repair - Advice Please

What about placing a truss underneath the mast that would attach to the bulkhead on each side. This would serve to transfer the mast load from the deck to the bulkheads. I have seen this done on smaller deck stepped boats where the mast support had failed after ten years or so.
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