Malcolm3
Well-Known Member
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Bowman 48 keel problem
- Thread starter Malcolm3
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oldsaltoz
Well-Known Member
Looking at the location of the limber holes I suspect the timber has suffered form moisture entry. But it couls also be that the timber used had a high oil content and the timber fibreglass has de laminated from the timber, not an uncommon failure.
Builders avoid the use of timber these days and use foam as a shape former only and apply a lot more glass, this results on more strength and reliability with less height, however it ia also more expensive.
You could drill some 6 mm holes and check the condition of the timber by checking the material that is driven out for moisture and condition, also take note of the pressure on the drill and any variation in speed of depth that might indicate softer areas.
If no problems, fill the holes with thickened epoxy resin.
You should be able to remove them one at a time and replace them with smaller fillers and more glass, eliminating any replete or this problem.
If you decide to replace them, use short sections of tube like conduit to form your limber holes and reduce the chanses of moisture contamination in the future.
I hope this helps.
Let us know what your findings are.
Avagoodweekend......
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Builders avoid the use of timber these days and use foam as a shape former only and apply a lot more glass, this results on more strength and reliability with less height, however it ia also more expensive.
You could drill some 6 mm holes and check the condition of the timber by checking the material that is driven out for moisture and condition, also take note of the pressure on the drill and any variation in speed of depth that might indicate softer areas.
If no problems, fill the holes with thickened epoxy resin.
You should be able to remove them one at a time and replace them with smaller fillers and more glass, eliminating any replete or this problem.
If you decide to replace them, use short sections of tube like conduit to form your limber holes and reduce the chanses of moisture contamination in the future.
I hope this helps.
Let us know what your findings are.
Avagoodweekend......
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sailorman
Well-Known Member
It looks like the "Matrix" strengthening the hull where the keel is attached has become un-bonded from the hull.
you need to get a surveyor urgently & get haul-out
sailorman
Well-Known Member
the hull above the keel will almost certainly be 100% GRP.
was the cracking more apparent when she was hanging in the slings prior to standing her on the keel & with no support by the water.
ie all the keel weight pulling / hanging against the matrix
Tranona
Well-Known Member
What does your surveyor say?
Seems that the floors are failing by the grp bond with the hull failing. The wood inside may be rotten from water ingress but you wont know until you grind off the glass.
If you can feel movement then the hull is flexing and the floors are there to stop the flexing so they need to be rebuilt. Only a qualified person on the spot can determine how much needs to be done and I guess oldsaltz suggestion of removing the wooden floors completely and replacing with foam cored ones with proper limber holes is a good long term solution, but I guess it depends very much on the depth of your pockets and how permanent you want the solution to be.
Seems that the floors are failing by the grp bond with the hull failing. The wood inside may be rotten from water ingress but you wont know until you grind off the glass.
If you can feel movement then the hull is flexing and the floors are there to stop the flexing so they need to be rebuilt. Only a qualified person on the spot can determine how much needs to be done and I guess oldsaltz suggestion of removing the wooden floors completely and replacing with foam cored ones with proper limber holes is a good long term solution, but I guess it depends very much on the depth of your pockets and how permanent you want the solution to be.
robp
Well-Known Member
If you haven't done already - would it be an idea to contact Rustler Bowman? Even with all the changes, the drawings will be there and considerable knowledge of your boat I would imagine. http://www.bowmanyachts.com/
sailorman
Well-Known Member
any re-glassing need to be done with epoxy as polyester resin doesnt stick well to old post cured GRP
sailorman
Well-Known Member
sailorman
Well-Known Member
Tranona
Well-Known Member
As you say, keel problems are not unknown, nor are failures of bonds of strengthening ribs such as the floors in your boat. Chuck Paine will have done his sums when he specified the layups, but there is no guarantee that either they were followed or that the quality of the original moulding was of the standard you would expect. It is only after time that you discover that many of the well established methods of the past have problems.
Only today I was discussing with the owner the rudder of a very well respected ocean going yacht of similar pedigree to yours. He had built a new rudder himself after the original failed. His description of how the original was built made my hair stand on end. Mild steel tangs on stainless stock was the least of the problem - mild steel bolts with nuts on set in resin to hold the two halves together before the foam was injected. Unsurprisingly after a few years rust spots appeared and the two halves split!
BTW agree it is unlikely to be grounding unless the boat was dropped onto its keel. Normally damage on grounding is hitting rock with the forward part of the keel. Damage is usually cracks at the front where the keel is in tension and a depression at the rear from compression. The fact that all the floors have damage suggest they were either not adequately bonded or are of inadequate scantlings to take the loads.
Only today I was discussing with the owner the rudder of a very well respected ocean going yacht of similar pedigree to yours. He had built a new rudder himself after the original failed. His description of how the original was built made my hair stand on end. Mild steel tangs on stainless stock was the least of the problem - mild steel bolts with nuts on set in resin to hold the two halves together before the foam was injected. Unsurprisingly after a few years rust spots appeared and the two halves split!
BTW agree it is unlikely to be grounding unless the boat was dropped onto its keel. Normally damage on grounding is hitting rock with the forward part of the keel. Damage is usually cracks at the front where the keel is in tension and a depression at the rear from compression. The fact that all the floors have damage suggest they were either not adequately bonded or are of inadequate scantlings to take the loads.
Tranona
Well-Known Member
Think you are taking the sensible approach. You can only deal with what you have. My only reservation might be if you beef up the floors you might create stress points, but running the additional laminations over the hull should avoid that.
Hope it all goes well.
Hope it all goes well.
oldsaltoz
Well-Known Member
If you have simply re glassed the area between the timbers and the hull without checking the internal condition of the timber you have possibly wasted a lot of time and money.
Drilling a few holes to check as posted above will be simple and tiake little time or effort.
The fact that the cracks open and close depending on the weight of the keel is a very good indication that the beams are not doing their job.
You must establish the reason for this, adding a bit more glass is not the answer, if the timbers are rotting they will continue to rot making things worse.
You must find and fix the cause of the problem before going back or it might be your last voyage. It's your decision, I know I would not be happy till had found and fixed the fault.
Good luck.
Clyde_Wanderer
Well-Known Member
I had this problem on my Hummingbird when I bought her and on the advice of a Surveyor and great advice from Oldsaltoz sorted the problem by cutting out the saloon sole, completly removing the old rotton cross floors, cleaning the whole area of hull down to bare grp, adding several layers of 600grm biaxial cloth with epoxy, making new 35mm thick cross floors and completly encasing them in with the same cloth, woven roven and epoxy.
A long drawn out, dirty backing job, but one that was very successful and worth it.
Apic of some of the new floors in place, the green is dye from a marker pen used to mark the cloth for cutting.
The mast compression post was also removed and as OZ says the drain tubes in each cross floor was epoxied in to prevent water soaking into the ply.
This repair left the hull very rigid and strong.
Incidently you are not likely to find any cracks on the hull itself as it will flex a lot before cracking until the point of sudden failure.
I increased the bilge stub thickness by aprox 15mm feathering out towards the sides of the hull.
C_W
A long drawn out, dirty backing job, but one that was very successful and worth it.
Apic of some of the new floors in place, the green is dye from a marker pen used to mark the cloth for cutting.
The mast compression post was also removed and as OZ says the drain tubes in each cross floor was epoxied in to prevent water soaking into the ply.
This repair left the hull very rigid and strong.
Incidently you are not likely to find any cracks on the hull itself as it will flex a lot before cracking until the point of sudden failure.
I increased the bilge stub thickness by aprox 15mm feathering out towards the sides of the hull.
C_W
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stav
Well-Known Member
That looks a really good sound job Clyde Wanderer. I bet that puts a lot of keel reinforcement jobs to shame! I hope Malcom3 ponders this and the fact that you have done this on a 30 footer with a 3 ton keel? No idea what the keel weighs on a bowman 48!
Sandyman
Well-Known Member
Malc3 I think your taking a bit of a risk there, especially if your next cruise is 3.5k miles.
Seems to me that your repairs, all be it with good intention, are a short term repair job. A cover up rather than pay out the expense of a proper repair ?
I dont see how you could have confidence and sleep in peace a thousand miles from land in the knowledge your keel could fail.
One thought occurred to me............have you considered having it x-rayed.......might be expensive but could be worth it. I know its possible as my boats previous owner has it done having made alterations to the keel.
Might not be possible where you are but just a thought.
Good luck.
Seems to me that your repairs, all be it with good intention, are a short term repair job. A cover up rather than pay out the expense of a proper repair ?
I dont see how you could have confidence and sleep in peace a thousand miles from land in the knowledge your keel could fail.
One thought occurred to me............have you considered having it x-rayed.......might be expensive but could be worth it. I know its possible as my boats previous owner has it done having made alterations to the keel.
Might not be possible where you are but just a thought.
Good luck.
Malcolm3
Well-Known Member
Thanks for replys . Have drilled one hole and it seemed OK will do a couple more but wood appears sound. Applied 3 x FIB-948 24oz fiberglass woven roving with West system epoxy in centre line overlapping 6” outward and over to each application end and throughout bilges and around studs. Also additional strengthening of 3x overlapping
3/4oz e-glass biaxial with west system epoxy to corners, facings, and longitudinal cross beam to hull bond. Certainly the floors are closer on Clyde Wanderer and as you say this keel is heavier. Have attatched photos of what is being done currently. Clyde wanderer when you say you increased the bilge stub was that done on the inside or outside?
3/4oz e-glass biaxial with west system epoxy to corners, facings, and longitudinal cross beam to hull bond. Certainly the floors are closer on Clyde Wanderer and as you say this keel is heavier. Have attatched photos of what is being done currently. Clyde wanderer when you say you increased the bilge stub was that done on the inside or outside?
30boat
N/A
Actually the keel weighs 3600lbs.
30boat
N/A
It seems to me that there are not enough floors.I would have fitted extra floors between the keelbolts .On my Fulmar I fitted an extra floor between the ones already there.The lay up on keel stubs is usually quite substantial and they are inherently stiff because of their shape but making them stronger is always a good thing.
Clyde_Wanderer
Well-Known Member
The bilge stub ( area of hull where top of keel mates to) was glassed on inside, no glassing was done on outside of hull.
How thick are the cross floors in these pics?
C_W
