Moving the bulkhead in a plastic boat

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Moving the bulkhead in a plastic boat

Post by jka2706 »

There have been various posts about moving the bulkheads in glass boats. Has anyone tried it in a plastic boat?

The boat currently has pedal footrests that aren't comfortable, but could be used to anchor a chunk of closed cell foam. Would it work to seal this around the edge (silicon sealant maybe)?

There's then about a foot of space, which would be accessible from the front hatch (and would make the space much bigger) if I knocked the current bulkhead out.

Will this work? Has anyone tried it?



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Re: Moving the bulkhead in a plastic boat

Post by nicholas »

I would not use silicon I would use one of the Sika products or an equivalent,

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Re: Moving the bulkhead in a plastic boat

Post by Mikebelluk »

Shouldn't be a problem, just make sure you make an accurate template to work from with an extra 3/4" all round as it will squash in a bit and you will have to sand a slight angle on it to allow for the taper of the boat. You will probably need 3" closed cell foam and I would Sikaflex it in too.

use masking tape to get a clean edge or it'll go all over the place!

Personally I would remove the footrests, it will make it a lot easier to get the foam in.
(Have a good look at an Easky, they have foam bulkheads I think to see how it's done)

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Re: Moving the bulkhead in a plastic boat

Post by flat earth sails »

Another way to taper the foam is to router a groove of about 4mm all the way around about 60mm in from the edge. The manyfacturers youse a poly urethane sealent, your normas sica will still have problems stiking.

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Re: Moving the bulkhead in a plastic boat

Post by ron-t »

My experience of foam bulkheads in plastic boats is that they are a disaster- you may get it to seal for a while, but after weeks or months they start to leak.

Don`t underestimate the safety issue of having bulkheads that leak. Even small leaks will allow water into the end compartments at a surprisingly high rate, if you come out of your boat and take a swim - rescues become much harder, and the boat may become highly unstable and unpaddlable. And yes, I have proved this the hard way. Fortunately I was only a few metres from some rocks.

Now you are suggesting using a foam bulkhead as your footrest - even bigger disaster !

With every paddle stroke you are stressing the seal between the foam and the hull, and in a very short time, the foam will move, and the seal is broken.

I see two possible better plans, depending on what kind of bulkhead the boat has at present.

1) If the existing bulkhead is foam, you can`t afford to stress it in any way. Get two bits of 6mm or 8mm marine grade plywood, cut them into sort of square / discs roughly 100mm x 100mm - whatever shape fits - and bolt them onto the existing pedals, which I agree are very uncomfortable because they are far too small. I have done this in the past, and it works fine. Use 5mm or 6mm A4 stainless steel screws, available from any yachting type shop.

2) If the boat has welded plastic bulkheads, then they are probably strong enough to use as the backing for a footrest. Remove the pedals, and get enough high density foam to make a fat solid block all the way from your feet to the existing bulkhead. There is a safety advantage in this, as it means that if you take a swim, there is less water inside your cockpit, so makes rescues easier.

Both of these methods will not impact at all on the second hand value of your boat as you can just put it back to how it was, whereas if you change the existing bulkhead, you will certainly reduce its second hand value and make it more difficult to sell.

If there is any doubt about the strength of the existing bulkhead, don`t stress it, use method 1) or something similar.

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Re: Moving the bulkhead in a plastic boat

Post by TechnoEngineer »

What ron said.... ... G_0407.JPG

Note there is an airbag behind the footrest.
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Re: Moving the bulkhead in a plastic boat

Post by Chris Bolton »

I would go with Ron's idea for the footrest, and Mike's advice if you still want to move the bulkhead. Unbolt the footrest rails to give you access to push the foam in and seal it (Sikaflex 291) and so that you can sort out the fixings for the footplate, then refit them.

If the existing foam is really well sealed, and you are in any doubt about whether you can do a good job on the replacement, maybe consider Ron's caution, but it's quite possible that a new bulkhead with good Sikaflex will be at least as good as the original if not better.

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Re: Moving the bulkhead in a plastic boat

Post by MikeB »

Or mount a plate to the existing rail mounts - as per this idea for putting a footpump into a plastic boat - ... fpump.html

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Re: Moving the bulkhead in a plastic boat

Post by blurpup »

Another option is to mount a plate directly onto the existing pedals. To do this you have two options:

a) Make the plate relatively small (approx 10 cm high is plenty) and do not bolt in place. This is to reduce the risk if you go past the footrest you can just pull it off with your foot.

b) Make a larger plate that does not have enough space to allow you foot to slide past it.

In both cases - start with a cardboard template (just push down the boat to get rough shape then refine from there). Cut channels to match the rail channels for your existing pedals. For a loose fit, put karrimat on the ends to create a snug friction fit, for a full plate bolt through the existing pedals.

I make my plates from styrofoam sheet cut and shaped to size and then wrapped in Kevlar Carbon and Carbon using epoxy. This creates a relatively lightweight and durable plate. You can also use balsa as the sandwich, but you need to make sure you seal it well to prevent the structure from weakening.

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Re: Moving the bulkhead in a plastic boat

Post by Nick P »

I successfully moved a bulkhead in my old sealion a few years ago. The bulkheads were dense foam and I wanted to move the forward bulkhead back to use as footrest while also reducing cockpit volume and increasing bow compartment capacity. Since I was moving the forward bulkhead aft, its size needed to be increased. I therefore made a new foam bulkhead to fit. Importantly, I fitted a layer of 9mm karrimat around the outer face of the new 75mm thick bulkhead to act as a gasket. The new bulkhead was fitted and rammed into final position using lump hammer and a length of 4x2, thus compressing the karrimat. Fairly brutal, low tech solution, but the bulkhead was water tight and remained so when I sold it 3 years later. Requires accurate scribing to make the new bulkhead, and also a high quality closed cell foam karrimat (cheap camping mats compress to easily).


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Re: Moving the bulkhead in a plastic boat

Post by Nick P »

Link to my earlier post (with photos) ... =4&t=77944


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