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Mast Shrinkage?

Macgyro

Amazingly Still Afloat
Blogs Author
So, It's been getting colder and darker sooner here on the Chesapeake Bay, but we were able to get out for a couple of hours Wednesday afternoon. I noticed that my all of my standing rigging (forestay, backstay, and all 4 side stays) were looser than usual. The turnbuckles were all still pinned properly and didn't look like they expanded. I'm sure that a little mast shrinkage is normal when it's cold outside, right?

I do have a deck stepped mast on a 1970 E-32, and I'm looking for anyone willing to tell me that the compression post is not rotting at the bottom (where it seems to be continuously moist) or that the support below the compression post in the seemingly inaccessible below-the-single-piece-fiberglass-floor pan has not somehow rotted or compressed.

I seem to remember a post about adding a support, but couldn't find it. I was really hoping there'd be some magic viking cure, but it looks like I may be jacking and bracing this winter.

Has anyone fixed this? and How can I check the mystery support under the floor pan without cutting through the floor pan?

Thanks again for your hard won expertise!
-Dean
 

ChrisS

Member III
I did this job on my 32-2

I can show you the finished product pics if you like, but this was the process:

-De-tensioned the rig.
- Put a 4/4 post on top of a strip of plywood cut to fit the cabin sole. On top of the post I placed a bottle jack, and then wedged another piece of plywood above that under the cabin top.
- Jacked up the cabin top, keeping the load on the post.
- Cut a hole in the pan support just aft of where the mahogany compression post goes through the cabin sole. On my boat, it mated with a cross-shaped piece of iron that was degrading.
- Chipped out the iron with a dremel and a small sawzall. This was the hardest part. I also accessed it via the forward end of the salon bench.
- Jacked up the post a bit more.
- Glassed in a big chink of G-10, and shimmed it with pieces of 1/8" G-10. I jacked up the cabin top a time bit more to get the last shim in.
- After the epoxy cured, I let the jack go, and then tensioned the rig.

This was about four years ago, and there has been no more movement. While the job took the better part of a couple of days, it didn't cost much: about $150 of G-10 from McMasters, plus some epoxy and fiberglass.

Not rocket science!
 

Cory B

Sustaining Member
DImpled Mast Step?

It very well could be the compression post related.

But first, I would check the "step" that the mast rest's on on the deck. Is it dimpled? On our old E-32, water got in there and rotted some of the core.
 

Scott B.

Member
Dean,

I'm willing to tell you that your compression post might not be rotting at the bottom. I regularly sail year round on Puget Sound in the Pacific Northwest, and I've notice the same phenomenon of looser than normal shrouds and stays on my boat when the temperature is very cold. I don't know why this is, but I do know that my compression post and the compression post support block under the floor pan are absolutely solid, because the post is completely inspectable from within the cabin and I replaced the support block myself (which had been completely rotten before). By the way,when I say looser than normal, I mean slightly but noticeably looser when feeling the tension by hand, but not loose enough to cause any concern about going out sailing in cold weather.

The reason I think it may not necessarily be rot is because you specifically mentioned that you (only?) noticed it in cold weather. When the support block under my cabin sole was rotten, I had strange things going on in all temperatures, and the strange things got worse with increasing wind speed, not with temperature. And by strange things, I mean rigging going variably way out of tune, head door popping open and slamming around and then not being able to get it latched closed again, floor sagging a little under the compression post, and other weird things indicating something was definitely not right. And sure enough, below the cabin sole, under the compression post, there was a semi-rotten block sitting on a soggy mess that appeared to be a pile of liquefied plywood shims.

Since I've made the repairs, I've assumed the looser rigging in cold weather was just due to different temperature contraction levels among the various materials of the boat and rigging. But I may be wrong, so it could still be a rot issue, but I would think you'd notice that problem no matter what the temperature. I'm very curious to find out what it ends up being, since I've noticed the same thing on my boat. Good luck solving this mystery. I hope it's nothing major, but if you do end up with a large project on your hands there's a lot of good info on this site and a lot of Ericson owners out there willing to provide excellent advice and experience on how to do it yourself.

Scott
 

Jenkins

Member II
Mast shrinkage due to temperature change.

All materials change length when their temperature changes. For a long thin thing like a mast this is characterized by the coefficient of linear expansion, which is the ratio of the change in length per degree, divided by the total length.

So, change in length = coefficient of expansion X length x temperature change

Aluminum has a coefficient of linear expansion of about 22x10^-6 m/(m-K)

For a 50 ft mast (about 15 m), with a temperature change of 10 K (which is corresponds to going from about 70 F to 50 F, the change in length of the mast would be

Delta Length = 22x10^-6 [m/(m-K)]x 15 [m] x 10 [K] = 0.0033 m = 3.3 mm

We also need to recall that the wire rigging will also change length as the temperature changes. Steel has a smaller coefficient of expansion than aluminum and the exact value depends upon the particular type of steel. To get an upper bound, we will use a number from the low end of the range for steel - 10 m/(m-K). To get the change in length for the rigging (assuming it is the same length as the mast)

Delta length = 10x10^-6 [m/(m-K)]x 15 [m] x 10 [K] = 0.0015 m = 1.5 mm

So, the net change is the mast has shrunk by 1.8 mm more than the rigging.

You also might wish to take into account that the length of the rigging is different than the mast with the material in between largely being fiberglass with a coefficient of expansion of 36 m/(m-K)

However, this correction will be smaller because the difference in length of the rigging and the mast is much less than the overall lengths of the mast/rigging.

Looking at turnbuckles, it appears that a typical thread per inch count is about 20 threads per inch which is about 0.8 threads per mm, so that works out to a little over 2 turns on the turnbuckle to take up the 1.8 mm slack.

Since this is all linear, doubling the temperature change - going from 70 to freezing (20 C to 0 C or if you prefer 293 K to 273 K) would double all these numbers.

Also keep in mind, I used a very low range number for the expansion of steel - a mid-range number would lead to reducing the effect by about half.

Hope that helps you think about the cause of your problem.

Best,

Peter
 

alcodiesel

Bill McLean
Peter, I was thinking the same thing- aluminum expands and contracts more than SS. I don't know, is it the way Atomic 4 aficionados think?
 

Macgyro

Amazingly Still Afloat
Blogs Author
Wow! What a range of possibilities!

You guys are awesome!

Before we went out, I tightened the backstay 4-5 turns the wrong way (loosened) and then about 8 turns the right way. That was enough to "properly" tension the backstay using my highly accurate push it back and forth and see how far it moves technique. I left the side stays? and baby stays as they were, and didn't notice any significant deviations from my non-scientific sailing experience. They tightened up under load pretty well with the downwind side loose.

I really like Peter's scientific explanation, which I have no clue what it means, but looks impressive under a microscope. I hope it means I may not need to repeat Chris S's repair.

Next courses of action:
I will check the step to see if Cory B's idea holds water...

Then I will look to see if I can glimpse under the compression post through the forward end of the salon bench to see if the iron post support is indeed degrading.
Possibly cut a hole in the pan the size and shape of one of those circular deck access plates to inspect further, and hopefully not have to dig it out like Chris'.
If it is that, Thank you Chris, having a plan and a cost estimate will be extremely helpful if I need to do that repair.

And Thanks Loren for the links I was missing. Those were indeed the ones I saw before, and may use them.

Thanks Again!
-Dean
Will definitely post photos and corrective actions! Or, just tighten up the turnbuckles for cold weather sailing! Keep your fingers crossed!
 

ChrisS

Member III
Inspect from deck to bilge

If you read old threads and look in the 32-2 manual, you will see that the offset compression post can cause deck to collapse a bit, which then invites water intrusion and rot in the net step core. Another possibility is the degradation of the joint where the compression post meets the iron in the bilge. Either will cause movement.

Starting from the deck:

- Take a straight edge and place it on the raised pad where the mast meets the deck. Is it level, or concave? If the latter, water may be pooling and intruding into the deck core.
- Is there a crack in the headliner to the right of the compression post?

Either of the above indicates movement or flexing in the deck.

-In the cabin sole, do you see cracking where the post goes into the bilge? This may mean the post is moving on the bilge end. My boat also had small chunks of rusty iron that indicated that the iron step was failing.

My boat had no symptoms of saggy rigging, but much of what I just described.

If you plan on keeping the boat for any length of time, figure out where you can strenghten these areas. Or, just go sailing, but you may find that the worsening problems could thwart using the boat at an inconvenient moment in time.
 

Macgyro

Amazingly Still Afloat
Blogs Author
Thanks for the Mast Step by Step instructions

That looks like a good set of steps to inspect the area. Your description makes me think an old problem may have migrated to the mast step. There is a solar vent on a wooden block about 2-3' aft of the mast that was leaking into the core of the deck. I re-sealed it, but didn't do anything with the wet core except leaving it open (on the interior side) to the base of the vent, hoping the vent would dry it out. It didn't dry out, and it may have spread under the mast step. Another part of this will most likely be removing the block and vent, re-coring the wet deck, and fiber-glassing over the old hole. Possibly later, installing a real hatch instead of a solar vent that dies after a few months.

Will post photos once I get to the boat and get to inspect it keel to mast.

Thanks!
-Dean
 

Macgyro

Amazingly Still Afloat
Blogs Author
Photos

Went out sailing today. No real change, but I got to look at the mast step and compression post. I have a small crack in the headliner, but I think it's been there a while. I sanded the top of the door down a little about two years ago because it was sticking, and it hasn't started sticking again. Here are some photos. I took one from inside the built in seat and it looked like a composite block is under the floor, same for the one from the bilge. The plywood bulkhead right next to the compression post is completely rotted and I re-tabbed most of it except for the part right up against the compression post. Here are the photos:

IMG_0323.jpg Compression post (sideways) Rotted plywood is visible next to post.
IMG_0327.jpg Under the compression post (sideways. The lighter colored stuff is down) The Dark Grey is vertical and looks like it's in good shape.

IMG_0319.jpgMast Step with leaking wood block aft. (Heeled way over)
IMG_0324.jpg Bottom of compression post with bilge hatch open (sideways) The forward wall of this area is composite.

May see what happens if I jack up the cross member here under the mast. If it opens up a space, I'll know that I need to rebuild something.
 

Macgyro

Amazingly Still Afloat
Blogs Author
*UPDATE* The simplest possible answer is usually the correct one.....

*UPDATE*
I decided to tighten the turnbuckles on the stays to the proper tension regardless of whether the mast support was rotting or not, and have a frame of reference to see if it was getting worse or was stable. The cotter pins holding the ends of the cables to the chain plates were all in good condition (will still replace them this spring) but the pins preventing the turnbuckles from rotating were all bent inside the turnbuckles, allowing them to rotate and loosen the stays. Duh. Should have checked those first, but the plastic covers allowed the 'out of sight, out of mind' mentality to take over. I think I'm still going to fiberglass over the leaking deck vent under the boom and possibly dry out the core just aft of the mast to prevent future problems, but I think the KISS principle will apply for the mysterious shrinking mast.

Thanks for your help!
-Dean
IMG_0419.jpgIMG_0421.jpg
 
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bgary

Advanced Beginner
Blogs Author
The cotter pins holding the ends of the cables to the chain plates were all in good condition (will still replace them this spring) but the pins preventing the turnbuckles from rotating were all bent inside the turnbuckles, allowing them to rotate and loosen the stays.

I've actually seen that a lot over the years (cotters that bend and allow the turnbuckle to turn)

I use big split-rings on mine, positioned so that the ring goes through the hole *and* around the body of the turnbuckle. I like this approach because there's no way the turnbuckle can loosen, I can remove and replace the ring without tools, and there are no sharp ends to snag things.

I know there are those that consider using rings like this to be a violation of the laws of seamanship, or something, but... it works for me.

(I also use rings to secure the shackle pins on my anchor rode, instead of siezing wire. I know, blasphemy... right?)

turnbuckle_keeper1.jpg
 

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
I've never understood the use of cotter pins in turnbuckles. They have to be pretty large if there to stop rotation.

Tradition, I guess. And tradition to tape them over, which leaves peeling tape after a few months.
 
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