Moody 376 Compression post issues

[Keith Miller]

I’m in the process of buying a 376 and the survey has picked up an issue with the compression post

 

[John Wood]

Hi Keith, This is a well known 376 problem, the mast compression support was cast iron and it rusts. The solution is , rig down, remove joinery and replace the mast support, the bulkhead bonding needs to be checked as well. Hope this helps, not a DIY project I’m afraid, Regards, John

 

[Keith Miller]

That’s very helpful John thanks very much for the information

 

[John Wood]

Hi Keith , Had another thought, you need to check there is no flexion/distortion of the deck as well… Regards , John

 

[Keith Miller]

Great
I’ve had a survey and the deck was okay.
Thanks a lot for your info John much appreciated

 

[Peter Wright]

Hi,

I don't think Moody ever used cast iron for a compression post, they used a mild steel tube with mild steeel plates welded on for the top and bottom ends. It also rusts. Greater problems with the mast support system arise from the timber blocks , one on which the compression post is mounted and the other in the deck between the top of the compression post and the mast step. In both cases, water can get into them and start rot with the consequence that the timber can no ;longer bear the load and gets squashed thinner. In the case of the block in the deck. the issue often arises because the holes bored through it to pass cables below deck are not adequately sealed.

Peter.

 

[Pavel Hort]

Hi,

I'm very new to Moody 376 (new owner) and one of the first issues I have spotted is the completely rotten Compression post plate .
As I see it and correct me if I'm wrong:
1. Mast has to go down
2. A whole new compression post to be installed - fiberglassed back into the hull
3. make sense to install a new standing rigging ( 15+years) when mast is down in marina

All job to be performed by professionals, I wonder what kind of price tag I would be looking at £ to brace myself?
Anything could be done DIY to prepare it for marina and eventually save some costs?
And its only when everything else is good.

Pav.

 

[Peter Wright]

Hi Pavel,

Welcome to the MOA, and sorry to hear of your problem.

Your description of the remedial work sounds not too far out, if you establish that it's really necessary but just occupies a volume 8 to 10 times te volume of the steel it comes from so, despite your photos, you may not need to replace the compression post. I would be inclined to chip and wire brush the rust off the foot of the impression post to see how much steel remains. If there is sufficient, the remedy might be as simple as cleaning up and recoating with something like Hammerite.

Whether or not you replace the compression post, it's worth checking that the floor on which it stands and the mast plinth in the deck , which stands on the top of the post are both in satisfactory condition to support the mast compression loads. If the floor needs some remedial work, that will probably require the compression post taking out anyway.

If you are not comfortable making judgements about the amount of steel remaining or the condition ofvthe floor / mast plinth, I would get advice from a surveyor or a shipwright you can trust.

If your standing rigging is 15+ years old, it's due for replacement regardless of the compression post issues, so it sounds like your mast will be coming down anyway. While it's down, it is certainly worth a full overhaul of the main and genoa furlers and a thorough check of all other features of the rig (spreaders, mast head and foot sheaves, genoa halyard defector) and all the mast electrics. I know ti's is more potential expense, but it gets the most out of the cost of taking the mast down.

The other job you should do while the mast is down is to lift the little sealing plates around the chain plates, rake out the sealant resealwith a modern sealant and rebed the plates. The original sealant used for these tends to dry out and crack allowing water to soak into the marine ply bulkheads to which the chainplates are bolted. In extremis, this leads to rotting of the marine ply, so allowing the bolts to tear through the ply and the chainplate to come through the deck dumping the whole rig over the side. Keeping these sealing plates watertight is the key to preventing this. As a separate job, you should arrange access behind the beautiful cabinets in the saloon to check whether previous leaks have degraded the part bulkheads. You can read of Mike Hallgarth's dismasting here:

https://www.moodyowners.info/threads/dismasted-chainplate-to-hull-connection-failure.26812/#post-178919

And the repair here:

https://www.moodyowners.info/threads/post-dismasting-refit.28147/

The post replacement job can be done without taking the mast down by using a couple of Acrow props, one each side of the post, but it seems to me you will be taking your mast down anyway. Personally, I would replace the compression post with a new one in type 316 stainless steel once it has been removed, regardless of how much steel has been lost

You have already saved a few labour hours in getting access to the foot of the post and could really save more by taking down head lining to give access to the top. A key hassle is removing the table from the post which can put hours on the job, it's not clear what whether you have done that yet.

Lastly you are clear that you own Moody 376 yet in your name window it says you have a Moody 38 (2000s) this based on data you provided when signing up for membership. These are two completely different designs. You can update your membership details here:

Update Membership Details | Moody Owners Association

www.moodyowners.org

The update will not happen immediately on clicking submit as it requires some input from our membership registrar, but it usually gets done within a few days.

Any further Qs just ask away.

Peter

 

[Pavel Hort]

Great and very helpful feedback Peter, thank you !

Details updated, so hopefully the right Moody will be selected this time!

First thing I will remove the fiberglass on top + around and rust to see what remained from the post plate, but I'm afraid not much left as I was able to slide out very big chunks of rust (not visible from my pics).
But at this point when I just found out today that both side stays are 25years old and front/back stays are even more than 25years: The mast will go down and will be inspected + re-new all the bits you have described + re-wired. New standing rigging seems to be must TO DO!

The compression post will be changed I guess the similar way as it is described in the article ‘The Mast Post’ by Mark Prior. Completely new or partially. I was told by boatyard to use galvanised mild steel for compression post due to its characteristics and not SS. = Still time to research. I will strip down the whole area including the saloon table (any tips or links to be found on MOA for the table removal?

As you named "The other job you should do.." is actually my nightmare after reading the chain plate threads and the dis-masting article last weekend. This is definitely on the list TO DO next ! I went through all the articles and Im not sure at the moment if I should remove the whole cabinets ( did not find any MOA article yet) or just cut out the inspection hatches. The hatches will be there either way as the varnished cabinets are not my priority. I don't exactly know the location of the chain plates on my 376 and their side of attachment so I guess to remove the cabinets would be more sensible solution and then make hatches on the correct places.

So far I have just exposed the babystay chainplate, but based on what I was able to see it is just something rusty behind fiberglass for me. Any thoughts?

Pav

 

[Pavel Hort]

After removing all the rust flakes with hammer this is what has remained. About 3mm thick plate still attached to the post. It started to bend a bit as it is only 3mm thick now (i believe it was at least 5mm+ as new. What do you recon, still sailable far from the coast?

 

[Peter Catterall]

Thanks for the techy stuff on compression posts! we are considering buying a Moody 333 mk 3 so checking compression posts will be on my list!
Pretty scary when you look at the pics!

 

[Pavel Hort]

Just got the price quote from the local marina to fix the compression post. Stay kalm and sit: £2600 Not including the mast removal, its another £1800 . You better check it before buying.

 

[Peter Wright]

Hi Pavel,
If it takes 1 man a week to do the job at £60 an hour that will be £2400 - doesn't leave much for materials! At today's cost of employing people the man won't be earning much either. £1800 to drop the stick seems a bit much. Do your prices include VAT or not, but it's not cheap to keep a fully inspected and certified crane waiting for such jobs.

Peter.

 

[Pavel Hort]

I will fix the compression post myself and let you know how many hrs it took me = never done such a job before! It will be interesting to see - there is a great article by Mark Prior who did the same job also on Moody 376. I have managed to drop the price down for the mast removal/re-installation to £1400 as I will remove the boom, sails and electric myself. All the price quotes are including VAT

Pav.

 

[Pavel Hort]

I have cleaned out the compression post base plate area to see if cleaning and anti-rust would work for a while. Postpone the job for year/two. But it looks like the weld completly disappeared and the middle part under the post is bended downwards. I have measured about 1cm gap. Any thoughts?

 

[Peter Fleming]

Hi Pavel - I don't know about the 376 specifically, but I do know some Moodys were fitted with compression posts which were encased in a shiny metal sleeve to make it look pretty and yours looks like it might be that type. In such cases the sleeve is not structural and just hides the internal steel post onto which the base and top plates are welded. If yours is like that, then the sleeve itself is not welded in place so what you see as a "disappeared" weld is actually just the gap at the bottom of the sleeve, now visible because all the rust is cleaned away. I believe the sleeve is slightly shorter than the post and there will be a gap at the top so that the sleeve can slide upwards to reveal the weld at the bottom of the post.

That might help you see the condition of the post structure a bit better, but if you have a 1cm drop in the centre, it sounds as if the internal timber of the supporting floor is giving way. I think you already cut some of the encapsulating GRP away - was there any evidence of rot or movement or previous repairs? With that amount of drop I would expect it to be visible. If the timber floor is solid, then my only other thought is that the pressure created by the formation of the rust under the plate has forced up the ends as the coach bolts themselves will have also rusted and deteriorated, whereas the centre under the post had no give. I don't know if that's likely... I'm not a structural engineer! Perhaps one of our more engineering-minded members will comment.

Good luck!

Peter

 

[Peter Wright]

Hi Pavel,

The curve in the foot of your compression post may well have been caused by the welding heat when it was made, in which case it would always have been there, but there is no way to be sure of this. Judging from your photos (not the most certain approach) it seems to me that the post will last a few more years but, if it concerns you, it will be a constant concern every time you sail the boat, in which case replacement now, rather than in a few years' time may be your best option.

Just to be sure you understand that the shiny chrome plated part is not the compression post - that is simply a decorative thin walled tube covering the post itself which is a smaller diameter thick walled tube inside the decorative one. The decorative tube was never welded to the top or bottom of the post.

Peter.

I see Peter F. got there first with my last point!. P.

 

[Pavel Hort]

Hi Peter&Peter

now it makes more sense to me as the edge of the chrom tube was so smooth and sharp. Thanks a lot for this clarification and for your opinion regarding the urge of fixing this. Im playing with idea to survive next year in Med without major investments. Which starts with the Mast removal, fixing the compression post and new standing rigging (25years ). I would check the chainplates and its attachment + order a rigger to survey the whole rig. If one part fail, then it just make sense to do it all in one go when the mast is down.

Pav

 

[Peter Wright]

Hi Pavel,

If you do nothing else this year, at least rebed the sealing plates around the chainplates to ensure they are watertight. If this was done every 5 - 10 years, the marine ply knees to which the chainplates are bolted would not go rotten and rigs would not be lost on these designs.

I am surprised that your insurer is not insisting on new standing rigging if it's 25 years old. If the rigger doing the survey knows the age, he may well recommend new standing rigging just on the grounds of age.

If the mast comes down for standing rigging, you would be wise to attend to the compression post at the same time, rather than paying to take the mast down again next year as well.

Peter.

 

[Pavel Hort]

Hi Peter,

100% i need to rebed all sealing plates. Port side is leaking every rain directly into the bilge along the plywood bulkheads. I can only hope its not leaking 20years and the plywood is still in decent shape. I managed to reach bottom part of the bulkhead via seacock access opening in cabinet. This part of the bulkhead is already not covered with GRP and sounded solid. But upper part where the chainplates are attached???..still waiting to be revealed.
Insurer had thrir own rigger who looked at it 5years ago i think and she was happy to extend the insurance with them for another year even though the boat changed owner.

Pavel

 

[Pavel Hort]

Christmas is over, time to start to work on Moody). Just removed the compression post (which was quite an easy job) and it was just about the right time! Bottom plate coroded into 0-2mm thickness only and bended. Even top plate was corroded at one corner as some idiot drilled a hole throught the plate to run a cable.
Bottom looks decent, the grp is not flat creating cradle shape between the two bolts with about 5mm vertical gap. Poked into the screw holes and the ply looked solid jn the holes so i do expect its OK.
Im planning to lay over few layers of grp to flaten the bottom out before putting back the post. The post will get a new 10mm thick bottom plate and a new paint under the ss sleeve. The old grp recess i will cut away and will not glass over the bottom plate as the original design. I did not find any reason for it, hope im right.
Any comments/suggestiins?