Filling Hollow keel on FS25

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johnjfrake

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I am in the process of fitting an inboard engine to my Folksong 25 and while perusing the space it will be located I realised that the empty keel may be a source of problems in that rear of keel is deep, long, empty and would be a pig to get at when the engine is in place. It occurs to me that filling the bottom 15-18" of the keel with foam and putting a few layers of glass over the top to seal it in might be a sensible idea. It would, slightly strengthen the keel, reduce the opportunities for flooding should I accidentally come across something sharp with the stern of the boat and prevent a possible/probable smelly damp accumulation where it is most difficult to get at. I seem to recall from somewhere that some Invicta (not a dissimilar design of boat) owner have done the same thing. Does anyone out there have any experiences of this practise or any thoughts on the pros and cons please?
 
Many of the polyurethane foams available to us absorb water over time. Single pack aerosols and two-pack mixes are said to be closed cell but most are only partly so. I built quite a lot of kayaks some years ago, filling bows and sterns with two-pack foam. Two years later we had to dig it all out.

If you follow this route ensure that your grp layer above is totally waterproof, likewise the keel itself to prevent moisture access from outside. The long-term consequence of soggy foam down there is very likely to be osmosis.
 
Thanks for the information. It leads to another question namely is there an alternative to foam? Something light as I don't want to alter the ballast ratio or move the centre of gravity aft.
 
johnjfrake said:
Thanks for the information. It leads to another question namely is there an alternative to foam? Something light as I don't want to alter the ballast ratio or move the centre of gravity aft.
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Air?


As vyv says, filling it with foam will cause you no end of grief in later years.

Better to leave it empty, if you did have a leak, or were holed, you'd have a load of wet foam to remove before you got to the problem..
 
I understand where you are coming from but then if i got holed with the engine in place plugging a hole at the bottom of the keel would be impossible. Something to make provision for however unlikley it is to happen whether foam filed or not!
 
Would it be possible to pack/fill the space with loose polystyrene beads, as per used in dog beds etc:? Then a layer of sealed waterproof fibreglass to seal it. That way if you ever needed access you could suck the beads out with a vacuum cleaner..
 
I would first make sure the keel was very dry and would then give the internal area a light sanding, wipe with Acetone before and after sanding then apply at least 3 or 4 coats of epoxy resin.

Then get an off cut of closed cell foam and shape it to fit at the required level making sure it has a fall to one end to collect any fludids. I would then glue another bit of foam to the underside and cut a hole in the top sheet to form a well for a bilge pump and glass the area with a thicker base, and glass the bottom of the sheet/s with an epoxy resin and clot (Not CSM).

Then mix some Micro fibres and epoxy resin and butter the edges all round and position the sheet with a fall to the well, than using more micro fibres create a coving around the outer edge with a bit of dowel or small fish paste jar.

Then apply about 750 grams of cloth and epoxy resin. This will provide enough strength to allow you stand on the new base.

Good luck and fair winds. :)
 
Just a thought.

Might be worth checking if you have a rudder fitting down there.

I have a similar set up to you with a keel attached rudder.

4' 6" below the waterline, I have a hexagonal nut on the interior side of the hull which attaches to an exterior spigot to attach the rudder foot. You could only get the rudder by removing this.

You might need to take the rudder off one day.

Regards
 
I think it would be best left open so that air can circulate around the inside of the hull moulding. You might arrange a bilge pump suction so that you can empty any bilge water easily. You could then throw a bucket of hot soapy water down there every now and then. As it happens I did fill the keel cavity in my Folkdancer - I used cement. I also put some extra ballast pigs down there. It stiffened her up quite nicely but I was young and didn't know very much then! I expect I got away with it because the Folkdancer has a little counter stern which gives some more buoyancy aft. I remember being pooped in her, though!

Neil
 
Once again thanks for the inputs. My rudder bolts are at the bottom of the keel but both nut and bolt are external. I am going to mull this over for a day or two before deciding what to do. I have located a company that offers epoxy foams with a claim to excellent water resistance, (http://www.mcmc-uk.com/products-epoxy-foams.html ). It may be that 3-4 coats of 2 pack epoxy on the inside of the hull followed by the epoxy foam then 3-4 layers of glass shaped with a well for any fluids to collect in is the answer. Will call the company to find out about techniques and costs.
 
Would you consider filling the space with shaped blocks of 'closed cell' foam , which are themselves wrapped in impermeable plastic sheeting? This assembly would not entrap water and should be easy to remove when so wanted. A simple removable floor would hold it all in place.
 
Yes the suggestion of moulded foam blocks coated in impermeable plastic sheets is a possibility but how to cover the top to prevent dirty water, oil etc getting between the sheets and the keel sides. As I said in my last post "needs a bit of thought". The inputs are invaluable though.
 
johnjfrake said:
t how to cover the top to prevent dirty water, oil etc getting between the sheets and the keel sides. As I said in my last post "needs a bit of thought". The inputs are invaluable though.
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I have a similar task and, like the OP, am mulling over the options. It seems I'd want to be able to remove the shaped blocks easily and periodically. A fitted 'sub-floor' on top of the wrapped blocks, sealed around with silicone sealant or some remaindered Sikaflex to prevent percolation of oily water down below, might solve that issue - until HMRC wanted a peek! :eek:
 
I used closed cell foam that comes as a 2 part mix from www.bluegee.co.uk for a similar job. Fill the cavity roughly then cut a ply panel, bond that to the hull. Drill a couple of holes, one to pour and one to vent - you should by then be able to judge the final amount. When it is cured, trim off any overflow and cover the ply with glass cloth and epoxy to a smooth finish.
 
I am mulling it over in my mind. The bottom of my boat's keel is pretty thick, I believe it would have to be a pretty sharp chain to penetrate the underside of the keel and the boat would have to hit it hard. I will bear in mind what you say. part of the reason for filling the keel would be to reduce the potential flow of water in through a hole in that area. I am not suggesting it would give complete immunity from damage and sinking simply slow the process down if I were holed in a very difficult to get at part of the boat.
 
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