DS II Compression Post Area Cracked

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DS II Compression Post Area Cracked

Postby crocboy » Mon Aug 26, 2019 1:49 pm

I have a 1982 DS II and noticed a fiberglass crack in the cuddy right in front of the mast step. I took a picture from the cockpit access hole and found that the two screws holding the mast step (circled red in the picture) are not even directly over the compression post. I've heard this is a common issue on the DS II, where the compression post is not directly lined up with the mast step. How can I fix the fiberglass crack, and do I need to move the compression post as well?
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crocboy
 
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Re: DS II Compression Post Area Cracked

Postby GreenLake » Mon Aug 26, 2019 6:22 pm

A crack like this could be due to mast step issues (likely) but also due to something too heavy placed on the cuddy floor (like e.g. a battery).

I would raise the mast, tension the rig and observe how much the crack widens. If there's substantial movement, you may not be able to repair without moving the support underneath.

In any case, any form of mere "cosmetic" repair risks failing. Your best bet would be to add a bit of strength, by building up a bit of a "plate" that overlaps the crack, but also extends underneath the mast step. To be clear, I'm talking about something that sits on top of the cuddy floor - yes, that makes the repair visible, but I fail to see any benefit that would make up for the complication of working this from underneath.

To avoid hard edges, you'll need to make a "pyramid" of layers, with each lower one wider than the one above by about 1". Top layer could be just the size of the mast step.

You can do the layup on a plastic sheet on your bench and then cover it with another sheet, so you can move it, and place in the cuddy in one piece. You can even let it cure a bit first (to the green stage, which is slightly tacky) and then use neat epoxy to glue it in place (works best if the two sides of the crack are level if unloaded).

Working this way is way more comfortable and probably results in a neater laminate. About 3-5 layers of cloth should do. If you want to use mat for some of the layers, it would have to be epoxy compatible (not all mats are).
~ green ~ lake ~ ~
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Re: DS II Compression Post Area Cracked

Postby crocboy » Mon Aug 26, 2019 8:41 pm

GreenLake,

What about a square piece of aluminum (about 12") that sits on the cuddy floor directly under the mast step?

Or possibly cutting an access panel in the cuddy floor and putting some kind of reinforcement post (4" PVC) directly under the mast step?

Also, why are they not aligned in the first place?
crocboy
 
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Re: DS II Compression Post Area Cracked

Postby GreenLake » Tue Aug 27, 2019 1:52 am

The problem that I see is that you appear to have diagnosed the cause for this without sufficient data (or you didn't share that data in enough detail). The floor can crack for two reasons. One is that the mast rests on it and is not sufficiently well supported (in a way that the mast step can move so far down that the floor would have to bear loads it's not designed for. The other is that some other load (battery?) was sitting before the mast and the floor was not strong enough to support that (and couldn't give, because the support for the mast forces that spot up. (The third option would be that there's something about the way the boat moves in waves that would make the floor move, but it can't because of the mast step support - I'm excluding this scenario).

That's why I suggest that you rig you boat and see whether tensioning the mast causes the crack to open (before deciding on the best action).

The pictures aren't 100% conclusive. There appears to be a square plate below the floor and the screws seem to go into it, that should normally be enough and not a cause for worry. Since you seem to have an inspection port from which you can take pictures, I would also try to see whether the short mast support moves in any way when you add load (does it bend / lean?). If there's anything going on with the support yielding, then you most likely need to fix that.

If you decide that it's enough to add a "fronting" plate (i.e. a plate above the floor and glued to it), then it doesn't matter much whether you use aluminum or laminate something. Except that with laminate it's easier to do it in stair steps so you don't create a hard spot along which the floor would then have a tendency to crack again.

Are you by any chance unfamiliar working with fiberglass and epoxy? If so, it's not really that hard and even if you use aluminum, you'd need to glue that plate to the floor - it's not enough to just have it sit there; epoxy is the best glue for that. (We'll be able to talk you through that, if that's the problem).
~ green ~ lake ~ ~
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Re: DS II Compression Post Area Cracked

Postby crocboy » Wed Aug 28, 2019 8:20 pm

GreenLake,

After rigging it, it is definitely because of the mast. The crack is right between the top of the mast step and the area where the actual compression post is - because the mast step is directly over the compression post, there is a small area (1") where it is not supported. With the mast fully rigged, the crack widens and I'm not sure I'd want to take it out anymore. I'm debating whether to fix it above the cuddy floor with a large plate, or below by adding a second support post.

Still wondering why the original designers didn't line them up perfectly so it's supported. Do you know why that might be?
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Re: DS II Compression Post Area Cracked

Postby GreenLake » Wed Aug 28, 2019 10:44 pm

If mast and post are misaligned then I would do both.

A plate alone just spreads the unsupported load over a wider area of the cuddy floor; the plate would still be pressed down by the mast. Half the load would go on the post but the "free" end of the plate would have to be supported by by the floor (and it would carry a good part of the mast load, perhaps not actually 50%, depending on the length of the lever, if you get what I mean - if the offset is merely partial, e.g. some part of the mast sits over the support, a plate alone may be sufficient in distributing the residual).

You seem to have an inspection port that lets you view the mast support. If there's any way you can add something (or if you can cut a hole right where the crack is now to put something directly under the mast step. Perhaps a tube, or epoxy sealed bit of hardwood. Then you can cover the hole or crack with a plate glued to the floor, so it can help not only with spreading the load from the mast step but also help the floor stay up when you put gear on it.

The "why" of this particular defect isn't going to help you getting this fixed. Were all the workers stoned during those years? Or is it merely difficult to place a support "blind" between hull and cuddy floor and have it end up where the mast needs to be? I bet they thought their method worked, but they were lacking a suitable means of double checking (or thought the floor would be strong enough to equalize - well clearly, these floors have managed this task for many years before failing, so perhaps they were simply not counting on their boats to live as long?).

Whatever the reason, I think you know what it takes to fix this.
~ green ~ lake ~ ~
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