Moving keel

[Clyde_Wanderer]

Does anyone remember a few wks ago, I posted a question about my keel been loose?
Well I have had a surveyer have a look at it, and inside the boat, he reckons its the hull either side of the keel that is flexing, and not a loose keel.
But I am not sure, as I wonder how he can make this diagnoses with her sitting on her cradle and the keel resting on the cradle centre spine, ie, without been able to meve the keel.
He advices cutting out the interior floor moulding which has small cross floors, ( or bulkheads running transversley underneath ) each about 13-14" longx7-8"high and which also supports the inner floor, these bulkheads are laminated onto the top surface of the hull and keel seat, and are shaped like a pair of Y fronts, "for want of a better description".
Two of these BHs have small areas of delamination, which were noticed in a survey done 3 yrs ago, but described as imaterial by the then surveyer.
The point I am making is that there is no other clues as to a weakness in this area of the hull, which leads me to think that I am been incorrectly adviced.
I would have thought that if there was recent flexing of hull that the lamination between bulkheads and hull layup would show signs of sliding or movement.
I have been adviced to relaminate hull across keel area and up a couple of feet either side on hull, which i reckon I will have to remove keel to do this work, as the studs would get in the way of this laminating, Which in doing that would still cover the surveyer if it did turn out to be a loose keel anyway.
Can anyone advice what I should do, or describe the process I should follow, to carry out the relamination work successfully?

 

[Talbot]

my first thought would be to get a second opinion.

 

[oldsaltoz]

G'day Eamonn,

A picture of the delaminated keel box would be a big help here, any delamination of a structural beam has to be taken seriously.

Can you lift the hull so the keel can move? You could then check for any movement in the delaminated area, keeping in mind that the keel would be moving more under it's own weight than you can apply by hand.

As for removing the keel and glassing from underneath, you might be better off doing this from inside, at least you will not be working overhead.

More information and perhaps some pictures will improve the quality of the answers you get.

Avagoodweekend......

 

[Clyde_Wanderer]

Thanks for replies.
Old soltoz. No pics, but the delamination as I said above was noticed in a survey 3 years ago and described as imaterial by the surveyer.
We are talking about a very thin layer of glass seperating from a transverse peice of 0.5" ply. which doesent in the least bit look as if it could ever have been of the slightest structural use, except to support inner sole.
If is the case that there is any weakness here, then it has been a design weakness, as basically nothing has altered that I can see, and I have spent 2 yrs relaminating the hull and interior of a 15ft sailing/wkender boat before, learning a lot from this restoration.
My feeling though is, Now that the probability exists of there been a weakness in this area of the hull I will just have to bite the dust and sort it.
My biggest concern is getting the hull to a high standard of cleanliness in preperation for relaminating onto it, just to confirm,I would not have even considered the outside of hull, all strengthening laminate and new bulkheads will be done inside.
With the last boat I used a very sharp 1.5"wide wood chisle to remone a very thin layer of the old laminate so as to be able to relaminate onto clean substrate.
I intend to start the strenghtening by removing sections of inner sole, old bulkheads above keel bed, removing keel, cleaning as above, then building up to as much as 1" of new laminate above keel bed area, ( which is already aprox 3-4" solid laminate ) and spreading out towards each side of hull for about 2ft reducing thickness as I move out, all this will be done fore to aft the length of the keel and maybe longer.
But I must be careful not to build up laminate too thick as I move out or there is a risk of moving any stress towards the outer part of the hull rather than having a built in obsorbing affect in the hull layup.
BTW the actual bilge in my boat is really only the length of the keel at its deepest part and the deepest part is only about 10" for a ft long at the rear end of bilge where the last keel stud is, the rest of bilge is only about 7-8" deep.
If you want I can email you some pics and a sketch or two if you want to give me your email.
I still havent grasped sending pics to this site.
Cheers, Eamonn.

 

[William_H]

Hello Clyde. it seems to me you will benefit by more strenthening of the web structure and hull over the keel. If only for your own peace of mind.

I would go to a lot of trouble to avoid removing the keel. Assuming the f/g structure of the hul under (above) the keel is not spongy (so can take the pressure of tightening keel bolts and supporting the pressure of the keel mating face) then if the keel can be bolted down to more structural f/g on the inside your problem should be solved.

You mention a problem of keel studs. If these can be removed then fit a wooden dowel in place and lay the new f/g around the dowels. The dowels can be pulled out or drilled out when the glass is hard. Lots of wax on the dowel may help avoid resin sticking.
Glassing around the studs means teasing a gap in the weave of the cloth and pushing the stud through so strands of cloth go arounnd the stud. Much stronger than cutting a hole.
If you can't remove the studs then wrap cling film around the stud. This will stop the resin sticking to the stud should you need to remove the keel later. The nuts could be tightened down onto the soft resin glass if you need to get the laminate thinner to allow for short studs. This pressure will actually make the laminate a little stronger where it is compressed as only resin is squeezed out. (hopefully)

When designing the additional web structure remember the keel, when sailing has a sideways stress which ultimately is transmitted to the mast via the chain plates and the keel compression post so a band of strength to the chainplates is good. However when on a cradle or taking ground the keel will have to support the weight of the hull engine etc. Your idea of diminishing thickness out to the hull sounds right.

You may benefit by fitting more webs across under the floor. You seem a little doubtful about the existing webs. I reckon any f/g on wood needs a fair thickness of glass and resin so that the f/g has the strength and the wood is only a mold to attach f/g too. ie thick enough to be effective even if the wood rots away.

You may benefit by using carbon fibre rather than glass and if you want the laminate as thin as possible use some pressure to squeeze the resin out of the laminate as it cures. You need an absorbant layer which can be peeled off after hardening to take away excess resin. The experts use a vaccuum bag for pressure to get the strongest lightest laminate. Don't forget lots of heat for hardening.
These are just a few comments to help your thinking.
good luck olewill

 

[oldsaltoz]

CLYDE_WANDERER
You need to reset your profile to accept PM (personal mail) so that I can send an e-mail address.

Avagoodweekend......

 

[Swagman]

Sympathis as it sounds like you've a rotten job ahead just preparing the floor - the job of strengthening it will seem easy after.
If you've never cleaned back old glass before then be prepared to get very dirty and covered in grp dust. It's exactly the kind of job you'd be better off paying someone else to do!

Good luck

JOHN

 

[simonfraser]

if the hull is flexing, how much flexing is allowed ?
i'd def get a second opinion before starting such a horrible job
you want to keep the boat ?

 

[kandoma]

the surveyer may be right: boats do not get stiffer over time, on the contrary.
You may just see the normal effects of a boat getting tired.

Laminating or relaminating on top of a multiyear hardened poyester is questinable. The bond between the old layer and the new layer may be weak. This is a well documented "feature" of polyester. Professional advice and experience is needed in such a case. The new and the old layer may be subjected to strong sheer forces.

Peter

 

[Blueboatman]

I have -kind of- done this job. I bought an inexpensive US boat that had in the past grounded and pounded a bit,and whilst afterwards used a lot,it really required much stiffening such as you are contemplating.
IMO it would be as well to just use fibreglass resin and not epoxies because you are going to use a lot of it and the cost difference will therefore be huge..
You will need to brace the hull securely and level and ideally I would let the keel 'hang',supported between angle iron bracing so that it cannot move and compromise the stability of the shored up boat,but in hanging you are ensuring that the hull is not compressed and distorted upward.
The real trick is how you get the inner liner out to expose the hull area requiring additional laminating.. I used a dremel and vacuum cleaner and cut away along the vertical faces just below the bunk tops,having removed the wooden cushion retaining slats.In this way I knew that once completed,the repairs would be relatively inconspicuous.Still had to slice visibly across the cabin sole but this was later painted with nonskid paint so looked ok.
I drilled a bung hole in the hull bottom so that after each laminating job the hull could be sanded and rinsed out with fresh water.
I used 75mm diameter foam kiddy flotation tubes(like plumbers pipe insulation) sliced in two and layed athwartships at 200 mm intervals from aft of the keel stub to forward of the main bulkhead and relaminated using csm/woven rovings alternating.The hull was increased in thickness locally by 15mm tapering out to nothing 750mm out from the centreline.
I did as William H has suggested and worked the first layers of glass over and around the keel bolts.
Laminating in 2 stages,after the first lot had had a week to cure I chocked the keel and slackened the keel bolts and then laminated the second lot so that the nuts would when replaced actually sit on new material-there was enough thread to accommodate the thicker laminate.
I relaminated the main bulkhead generously so that the keel,mast and chainplate loads would be securely tied together.
I would say that it is a job that can be done(obviously)if you have the time and patience and reasonable aptitude.
You dont say what kind of boat or how tall long and wide is the keel ,nor whether there is a wooden cabin sole.
I too havent got to posting pics on this forum but if you pm me and need em I can scan a coupleand email to you,for what its worth.
Oh and if you are doing the job in the uk you will need good background heat in the hull(electric oil filled radiator is good) to ensure a consistent condensation free hull and controlled curing times..
One other thing;Are you absolutely sure that there is not an encapsulated wood or ply stiffening piece in the laminate between the hull and the keel,or indeed any delamination locally(tap with a screwdriver handle)

 

[Clyde_Wanderer]

Hi all.
Thanks for some very good thoughtfull advice.
Firstly to reiterate on some of the points.
I am almost 100% sure there is no other material in the keel bed except grp, but when taped with a screwdriver blade etc it does have a very solid metal sound, surley there wouldent be a steel structure laminated into the hull lay up?
As regards keel bolts/nuts, some of the studs arent long enough to take an inch or so more laminate, so as mentioned will have to try to remove maybe all the centre ones leaving just front and back to hold keel in place, then remove them once centre section has been glassed and studs refitted?
I will also have to remove timber mast support which sits againat under side of coach roof and down onto the keel bed, then it will need to be shortened to allow it to fit in on completion of job.
I have put my email on my profile so anyone can email me, and if you email me oldsoltaz I will send you some pics, and take some more tomorrow.
Eamonn.