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Old 05-09-2012, 06:44   #16
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Re: Hull Sagging on the Stands? Pics Enclosed

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Originally Posted by CarlF View Post
How deep are those cracks? This could be just cosmetic crazing in the gel coat or paint on the inside of the bilge. Fiberglass isn't white. Try chipping some off and see if you can see any cracks in the glass underneath.
I am not really sure what you mean in this post by the term "Sagging hull", thought I was getting ready to read about a terribly saturated, cored hull.

I thinks Carl has given you some of the best advice here so far. You don't want to create a situation where there isn't one. The bilge area you show in your picture is subject to constant and considerable cyclic loads and stress cracking in an area where a horizontal meets a vertical plane like your bilge stringers is a classic area to seek potentially cosmetic stress cracking. That being said as Mr. Carl has indicated you want to know definitively if you have a structural or a cosmetic problem here. The idea is to see if you can slide a thin tool between the hull and the bottom edge of the stringers, (Someone mentioned a feeler gauge). As was said before you want to know if the laminate is coming apart or the gelcoat is just showing some stress cracks, (Very common). Another option would be to take a sander or grinder and remove a small area of the surface gel around your worst area and inspect the substrate. If you do determine that the stringers have in fact seperated from the hull, and if the problem areas are accessible it really isn't that big of a deal to re-tab them back to the hull. If it was my boat I would also increase the schedule of the fiberglass and area of the tabbing as the original work may have been to light for the loads encountered.

Good luck with your project.
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Old 05-09-2012, 07:10   #17
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Re: Hull Sagging on the Stands? Pics Enclosed

You are looking at the boat in the position where the weight of the keel is supported by the frame, (it is sitting on it) and the weight of the fiberglass is self supported pressing on the keel (wide load from the fiberglass being supported in mid-air tapering to a narrow line (the keel). If the cracks are structural this will tend to open them.

In the water the reverse is true. The bouyency of the fiberglass shape pulls the boat up and the wieght of the keel hangs from that. This will tend to close the cracks.

The mast pushes down on the keel and the spreaders pull down on the mast and up on the fiberglass. In the area of the mast this is similar to in water loading. Conceptually you could test the cracks by changing the spreader tension. Tighter tension would close the cracks, looser would open.

Consider trying to insert a feeler gage, or piece of paper into the cracks, run a loop of rope between your spreaders, insert a piece of wood through the loop and twist to tighten, like a tournequet. (not too much, use your good judgement to keep it within sailing loads).

If the feelers or paper are tighter you have a flexing crack. Release tension before you try to retrive the paper, you don't want to leave stuff behind.
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Old 05-09-2012, 07:41   #18
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Re: Hull Sagging on the Stands? Pics Enclosed

The "support members", "crossbeams" "support ribs", athwartship stringers" "bilge stringers" that everyone are referring to are actually called the floors.
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Old 05-09-2012, 07:48   #19
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Re: Hull Sagging on the Stands? Pics Enclosed

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Originally Posted by GordMay View Post
The full weight of the boat should sit on the keel (even a fin), with the jack stands merely providing balance.
That's what I've always been told....
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Old 05-09-2012, 10:37   #20
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Re: Hull Sagging on the Stands? Pics Enclosed

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Originally Posted by Efraim View Post
The "support members", "crossbeams" "support ribs", athwartship stringers" "bilge stringers" that everyone are referring to are actually called the floors.

His problem is with the Floor Timbers.
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Old 05-09-2012, 12:24   #21
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Re: Hull Sagging on the Stands? Pics Enclosed

Efraim,
Thank you for writing what I was going to write.
The floor timbers under the glass tabbing could just be shrinking a bit since being dried out. Hard to say unless you had before haulout and after haulout shots. My advice is the check to make certain the timbers are not broken or rotted, seal up the tabbing and cut back and glass in the smiley at the forward top edge of the keel and pop the boat back in the water.
kind regards,
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Old 05-09-2012, 12:32   #22
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Re: Hull Sagging on the Stands? Pics Enclosed

How much material did you remove from the hull? I have seen severe problems result from doing this without careful planning. usually in our yard if we are going to do more than a double peel we do the whole job in sections, so the whole boat is not weakened all at once, to prevent stand print through and resulting warping of the hull shape. We start at bow and stern and work towards the middle, repositioning jack stands as we go. I saw a Beneteau done by another outfit end up with really severe hull warping from doing this all at once instead of in sections.
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Old 05-09-2012, 13:15   #23
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Re: Hull Sagging on the Stands? Pics Enclosed

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How much material did you remove from the hull? I have seen severe problems result from doing this without careful planning. usually in our yard if we are going to do more than a double peel we do the whole job in sections, so the whole boat is not weakened all at once, to prevent stand print through and resulting warping of the hull shape. We start at bow and stern and work towards the middle, repositioning jack stands as we go. I saw a Beneteau done by another outfit end up with really severe hull warping from doing this all at once instead of in sections.
+1 Thats what I was getting at.
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Old 05-09-2012, 13:54   #24
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Re: Hull Sagging on the Stands? Pics Enclosed

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There are loads of ribs built into the hull, it does seem very solidly constucted. Boat is 37' and weighs around 16,000lbs.

I was thinking about putting the mast back up (one I've checked the base of the compression post) and tightening up the new rig... the armchair thinking here being that it might help to reduce the sag?

Cheers, James
James the good news is that it's a Moody so substantially built, that's why they don't make them anymore, they can't afford to make boats like this now.

Like you we have a couple of minor cracks around the front of one of the keels (twin keels). I suspect they were caused at some point during its life by being lifted out and touched down a little hard rather than hitting something. I cleaned out the crack and painted over it with several coats of Primocon. The cracks haven't re-appeared (now five years ago) even though I check at each lift.

You have removed the mast, I would also remove the chain, empty the fuel and water tanks, remove the batteries to look after them ashore, so to reduce the overall weight. With the internal cracks I would use a sharp chisel to chip away the flow coat to see what is going on, an angle grinder will destroy the evidence you need to see but I suspect they are just cracks in the flow coat and don't go down into the GRP. If so clean up the cracks and replace the gelcoat.

Whilst your at this stage, clean up the mild steel keel bolts and nuts and paint throughout the bilge to make cleaning in the future easier.

Are you members of the MOA? there is a forum is under the "info exchange" icon.

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Old 05-09-2012, 18:34   #25
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Re: Hull Sagging on the Stands? Pics Enclosed

Thanks again for your replies.

I will have a chip away and have a look at these cracks...

To think about it a bit more... I do think it has sagged a bit... Where I removed the cupboards to re-bed the chainplates there is now a bigger gap to the "roof" then there was before...

I have since emptied out the water tanks. Diesel tank is right over the keel, so am leaving that for the time being...

I ground the hull back pretty far... through the gel coat... then through a substantial layer of CSM... it's now down to the roving over most of the below the waterline area (save for a strip either side of the keel that extends out to the bow & stern)... In hindsight it's probably a good thing that I didn't remove the mat in this area!

I guess I'd like to ask what the next best idea would be... Would getting some jacks in strategic places help to reverse this sag (it's about a 1cm drop if I measure at the stairs and the tops of the cupboards).?

Or should I monitor and check that it isn't worsening?

Will re-glassing with the hull in this postion lead to further trouble when the process ultimately reverses once she's back in the water?

Shame that the outer layer of hull was built largely with a chopper gun and then poorly consolidated! Then again, I wouldn't own it otherwise... as it'd have sold for a lot more money than I can scrounge together at one shot!
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Old 05-09-2012, 18:45   #26
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Re: Hull Sagging on the Stands? Pics Enclosed

as i said before,and minarete said,just lift it and prop it normally with the hull supported,remove the props individualy as you re glass in sections.
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Old 05-09-2012, 20:07   #27
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Re: Hull Sagging on the Stands? Pics Enclosed

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as i said before,and minarete said,just lift it and prop it normally with the hull supported,remove the props individualy as you re glass in sections.

+1. Adjust jack stands until gaps and cracks that are new have closed up and you feel the boat is postioned with the hull as fair as possible, with an even load on as many jack stands as possible while still leaving some large areas for glassing. Then glass large sections, wait for a cure, move and readjust jack stands, and glass the previous jackstand spots. Should work out fine if you are careful.
The cracks in the floor timber tabbing look like classic keel impact damage, and the "smile" at the front of the keel/hull joint would tend to corroborate that.
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Old 05-09-2012, 21:56   #28
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Re: Hull Sagging on the Stands? Pics Enclosed

When you zoom in on the photos, you'll see that there is a crack in the floor timber on each side of the compression post that connects to and is continuous with the cracks in the glass.

The angle of the crack would to me anyway be indicative of the floor member failing from compression. Well that's what it looks like to me anyway.
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Old 05-09-2012, 21:56   #29
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Re: Hull Sagging on the Stands? Pics Enclosed

I was thinking about the cracks in the floor timber last night, if the hull was sagging the cracks would start on top of the timbers and go down. Your cracks are from the bottom going up. Just something to think about.

Something else to think about is supporting the hull, I like to minic the pressures when the boat in the water. You have weaked the hull for repairs which means more support is required.
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Old 06-09-2012, 09:22   #30
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Re: Hull Sagging on the Stands? Pics Enclosed

All great replies...

Many many thanks..

From what I've read, these boats originally had a softwood beam glassed in and then fibreglassed over... the compression post then sits atop... The issue being that the softwood can rot... and thus cause the roof to compress... I think you all may be right in judging the cracks as a side issue... more related to the soft support beams than my hacking away at the hull...

I'll have a chat with the yard and see what they think... will send them the link to this thread.

Much obliged!

James
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