To flange or not to flange

Fair Progress - not

Fair Freedom has been the subject of previous blog postings here and work continues on her.

We hi-jacked Clive Richardson's thread about his new cruiser on the Norfolk Broads Forum a week or so back and talked about some aspects of bonding the hull to the superstructure and the different techniques. As part of this discussion, it transpired that people were interested in the kind of work we're doing on Fair Freedom and wanted details and pictures.

Well, you asked for it!

We've done a huge amount to this boat already but feel that we've barely scratched the surfrace. The boat's booked for Easter (eeek!).

The main issues with Fair Freedom are:

• Poorly repaired damage
• Damage to bonding between the hull and superstructure
• Dry Rot
• Wet Rot
• Leaky windows

In early 2009, we stripped the rear two cabins to starboard and replaced floor bearers and floors; built a new washbasin cabinet, repositioned the clorifier and aft toilet tank and remodelled the aft cabin from a double to a twin/double conversion. This year, the work is far more extensive.
As part of the work, the entire deck-level rubbing strake has been removed. This is the old-style strake which is a heavy plastic electrical conduit that fits (very awkwardly) over a flange. In removing this from the boat, we found large areas that had already been attended to in the past. Some of the work had probably been done by Richardsons as Clive told us that one of the things that they do with these Bounty's is to cut off the flange (it's part of the original GRP moulding) and replace it with an alimunium one. There are plenty of sections on the boat like this and it certainly seems to be a good idea; the flange itself seems to be a really vulnerable part of the moulding. Some effort was made previously to strengthen this as the flange itself is packed full of some kind of epoxy filler, much of which has broken away.

Ali profite bolted to the stern - the rubbing strake "slides" over this

Here you can see the original flange to the right along with the filling (broken up) and the damaged section to the center of the image. To the left, the flange has been cut off and replaced by the ali profile.

The overall problem with this kind of joint between the top and bottom mouldings is that the external elements are prone to damage. As the top and bottom flanges take knocks, the GRP weakens, the joint flexes and moisture creeps in. That's not to say that this is the only bonding between the two halves; it's not. There's also a GRP mat bonding inside the mouldings.

The problem is that as the joint flexes and lets moisture in, the gel coat also cracks and allows that moisture to seep into the GRP layup. One of the interesting things about GRP is that it is not waterproof - only the gel coat is. So, as the gel cracks, water gets in and over time starts to separate the GRP matting. Only in extreme cases is this really a problem; when laying up the original mouldings, the GRP tends to be layered whilst the previous one is still tacky. This "wet edge" technique gives a better bond between the layers which would find it very had to separate. However, when you're bonding the two halves, all the GRP will have set hard and so the new bond you make won't be quite as strong - this is unavoidable.

Now, add to this the perpetual ingress of water into this joint and the occasional flexing from some fool ramming the quay heading. The net result is lasting damage that will simply get worse even if it never took a knock again. Welcome to our world.

Ricko's idea of taking the GRP flanges off is sound and it's one that we'll probably follow all around the boat. It does mean grinding it all off, rebonding everything inside and then completely filling all external cavities with GRP strand, sanding down and re-gelling the whole bond.
What we plan to do after this is (if funds allow) totally discard the old rubbing strake and replace it with new rubber D section all the way around. I say "if funds allow"; this stuff is expensive at around £13 per metre - we need about 40 metres.

It's now a toss-up between refitting what we have and making a better job of it or doing the job properly. Handling the existing rubbing strake material is a real nightmare - it's very difficult to work with, is a plyable as a brick and damn heavy to boot. Will we spend almost as much time and effort in refitting the old stuff as we would in doing the job properly? We think it's a close-run thing. My preferance would be to renew all round but the additional cost will impact on other planned works.

We'll let you know what we decide. Meanwhile, here's a selection of images of the work.

Piles of GRP simply ripped out of the hull

Let there be light - but not here! The raised areas are the new bonding that have been laminated in to join the hull and superstructure.

There's two initial layers of mat, followed by a line of foam stripping which we hope will provide some shock proofing and additional strength. Over this, there's another four layers of mat. 

Yup, it could be snow, but it's dust. 

Another view of the new bonding

A typical crack

An old repair to the port-side aft cleat  mounting. Moisture had seeped in between the original lamination and the repair and the bond had broken, resulting in a big crack. Now, it all needs to be ripped out, ground back to solid material and rebuilt - much of it needs doing inside for strength.

Holes abound - often from the smallest of cracks. This one no longer exists

An example of an old repair. This gaping crack is in the underside of the front starboard deck just in front of the front window.
It was originally bridged by a plate of plywood and was simply bolted through from the deck and glassed over, you can see the bolts where we're ground them off. This will be relaminated shortly on the inside using the same foam technique as on the bonding. Once this is all cured, we'll expose the crack from the top, clean it all up, fill it, glass it and re-gel it. Sadly, there are plenty more of these kinds of repairs.