Keel stud backing pads?

[Clyde_Wanderer]

I have removed all the keel stud nuts and washers on the inside of the hull.
Under the washers were a hard wood backing about 50x80mm and aprox 15mm thick, the studs, nuts, and washers are steel. What I was wanting to know is can I replace the hard wood backers with, say, galvenized steel 12mm thick? As I feel that over time the hard wood backers will compress and yeild to the compression of the stud nuts, allowing the effect of the tightness of the nuts to deminish, whereas steel plates shouldent yeald.
Would like to hear the forum's opinion on this.
Thanks.

 

[Krusty]

In the Hummingbird 30 you have a yacht from a reputable designer: I think you should be wary about changing anything without a very good understanding of why it is the way it is!
Glassfibre hulls are laminated inside a mould to achieve a fair and smooth outer skin; the inside surface can never be as smooth, and often has small but significant high-spots. The hardwood spacer-pads you have found are almost certainly there to absorb those high-spots and spread the compression load from the keel-nut washers over a wider area.
If you dispense with the hardwood and use steel, the compression loads will be concentrated on the high-spots, possibly crushing the glassfibre laminate under them and allowing any bilge-water to penetrate the laminate; that could spell BIG TROUBLE!
Yachts designed and built by experienced professionals are the way they are for good reasons, and the DIY amateur always take a risk, sometimes a big one, by making his own ''improvements''.
I can speak from experience: some of my improvements have been very successful. Some had to be returned to the original and the lessons taken to heart; and I have seen quite a number of good boats degraded by enthusiastic but ill-informed owners.
Full marks for asking on the forum before going ahead!

 

[bedouin]

Firstly I wouldn't even consider galvanised. I don't really see any problem with wood - once it is compressed I don't see that it should compress any more.

Have you noticed any problems with the present set up - if not why change it? Wood is a common component of boats and I can't think of any situations where what you describe causes problems

 

[Clyde_Wanderer]

Thanks, Piota and bedouin.
The reason I was thinking of changing from wood to steel is, 1 the wood was well saturated and softish when I removed them, they also had an impression of the washers on them, which would indicate that the nuts would not have been as tight as they were when last tightened down, if ever since she was built, (as the two next to the mast compression post were glassed over)
Secondly the keel moved slightly when she was been hoisted onto the cradle, and lastly, the nuts were not excessively tight when I removed them, there was the crack as they yeilded but I put this down to them been well stuck to their threads and not overtightness.
Thanks again, Eamonn.

 

[oldsaltoz]

G'day Eamonn,

I just got back from Cairns and saw your posting.

FWIW builders use less and less timber in glass boats and more and more foam, timber was used because it was very cheap and available.

Foam is now used for the same reason, (Cheaper than timber)

Having seen the pictures of your keel mounting I would consider the following.

Adding new timber may cause problems later if it's not treated to make it as waterproof as possible, bearing in mind this is in a wet area.

Adding Galvanised steel may also cause problems later should it start rusting at any stage, it only needs one pin hole in the coating.

The area covered by the existing timber blocks is so small it would make little or no difference if they are eliminated by laminating or by simply filling with resin and Micro-Fibres.

If you do fill them you should look at larger washers (Even better plates) and bed them down on wet micro-fibres and fully tighten 2 days or more after curing has completed.

Andavagoodweekend......

 

[Krusty]

[ QUOTE ]
Secondly the keel moved slightly when she was been hoisted onto the cradle, ...[ QUOTE ]

I am wondering if you had a survey before you bought the boat?
If the keel has moved there will very likely have been sea-water ingress to the keel studs, and corrosion. You may have a serious problem to deal with, and you should think about taking advice from a yacht surveyor now.
He may well ask for some of the studs to be withdrawn, possibly all of them. If there is significant corrosion, new studs will be needed of course, but the hull-to-keel joint will also have to be re-sealed.
At best, that might be by injection..... at worst, the hull and keel will have to be separated, the joint area thoroughly cleaned out and re-made with correct 2-part mastic (immersion-proof).
For a boat that size, you are looking at a professional boat-yard job.

That is not what you wanted to read. Sorry!.

 

[pete]

On my Hunter Horizon 27 twin keel The keel bolts/studs come through quite large galvanized square plates whick look like they are bedded on mastic (possibly Sikaflex).
It has been like that since Hunter built the boat in 1989 with no leaks or other problems.

 

[steve6367]

I changed mine last summer and put new wood back - encapsulated the whole lot in epoxy first to stop it going soft. I think with steel you have have trouble spreading the load completly evenly unless you can get the inside of the hull completly flat.

The small amount of give in wood may also help with shock loading should you give the keel a knock. With the tightness you can always check that every few years.