[Public-List] Rudder Repairs (yes, another thread, possibly another ruder variation)

[Rachel]

Andy,

I just got my e-mail for the first time in a few days.  I see it's 
probably past the time you will have done the repair, but I'll reply 
anyway.  I know that sometimes in a situation like this, the thread 
will die, and then some other person will be left thinking (maybe 
later). "Oh geez, why didn't they continue it!"

>  As you mentioned, the groove is cut down the rudder to permit 
> fastening of the nuts that hold the blade to the shaft.? Our thought 
> last night, was that in order to rectify the compromising of the 
> rudder's integrity that the groove would cause, they fastened the 
> brass/bronze straps across the gap to serve the purpose of a glass 
> skin.?

That sounds about like what I'm thinking.  It's like they were working 
with new materials but thiking in terms of the old ways (which many 
folks did at the semi-dawn of production fiberglass boatbuilding).  
They were also trying to meet a very competitive price point, which 
generally means that trying new-fangled ways takes a bit longer to 
start (due to money issues).
>
> I think I figured out the other half while thinking about it this 
> morning.? While they filled the top part of the groove, where the 
> rudder is narrow, with fairing compound, they filled the lower part, 
> where it's wide and subject to more stress, with the strip of 
> Mahogany.? The Mahogany is there to take up the compression loading 
> while the strapping takes up the tension loading.? Had they known more 
> about fiberglass, they probably would have filled the void with foam, 
> feathered back the sides, and glassed over the groove, obviating the 
> need for the straps and the mahogany . . . . but they didn't.

I don't know if they were being all that scientific, but they might 
have been.  I have a feeling the mahogany might have been there simply 
to fill a gap, but there might be something to what you're saying too.
>
> Based on this, I'm reluctant to remove the mahogany and fill it with 
> something that I have no way of guaranteeing will be devoid of gaps 
> below the surface and which may (likely) will not have the same sort 
> of compression resistance as the mahogany.? The wood in our rudder is 
> rock solid, I could barely dent it with a chisel last night.?

Mine is extremely solid, and basically dry.  Nonetheless, there's no 
way I'm going to put it back.  That's because the only problem with my 
rudder was a small crack at the bottom of the strip that was caused by 
some small amount of moisture/movement of the wood.  That's pretty 
unavoidable I think.  Why not just fill with a strip of the pre-made 
fiberglass board?  That's rock solid and stable.  That's what I'm going 
to do.  I'll fill any slight gaps (the piece is pretty darned tight 
fitting though) with epoxy thickened with silica, which is also very 
compression resistant.
>
> This comes full circle to the questions of what to use to fair the 
> various spots.? There are three distinct fairing jobs to do, the 
> principal one is over the mahogany strip.? Anything too stiff is going 
> to crack, anything too spongy is probably going to let in water.? The 
> second one is over the straps, this is fairly straightforward, 
> thickened epoxy should do the trick.? The last one is around the 
> shaft.? Another lister sent me photos of his rudder (which is the same 
> as these two), the shaft is exposed with no fairing, part of me says 
> just get all the old fairing out and let them paint it, part of me 
> says fillet the sides of the shaft with thickened epoxy, if it falls 
> off it falls off, no big deal.

Why not wrap in glass?  I'm going to do that after I put in the 
strip/thickened epoxy/fair.  Just a thin layer will keep the cracking 
at bay, whereas just plain filler will nearly always re-crack (IMHO).
>
> So, back to the hard one, what would you cover the mahogany with?? It 
> is just a fraction below the surface of the surrounding skin, not 
> enough of a void to readily fill with anything other than a thick 
> coating of paint.? I could paint it with epoxy, fair over the painted 
> epoxy with thickened epoxy and sand it, although I think we all know 
> that will eventually crack off.? I could re-fair it with Bondo, which 
> will grip the wood, take the paint, but let water in to the mahogany, 
> and that's pretty much where I am in my decision making process at the 
> moment.?

I'm almost positive Bondo over the wood strip will crack and bring you 
back to square one, fairy quickly.  Not that I always have to change 
original methods - and I love and believe in wood - but just not in 
this particular situation.  If the whole rudder was wood that would be 
different - like with like.
>
> Any other thoughts on what would make a good elastic waterproof 
> filler?? Is mahogany sufficiently rot resistant that fairing it 
> without worrying about water intrusion is sufficient?? Per Rachel, I 
> believe there's gelcoat behind the wood, so the worst case would be to 
> replace the wood when and if it eventually rots.

The mahogany is fairly rot resistant, but it will expand and contract 
at a much different rate than the fiberglass.  As you say, it's not a 
crisis if it does, but you then either have cracks or have to redo the 
job.
>
> Rachel, please don't stop posting, being able to work through these 
> sorts of problems with a lot of contrasting viewpoints and experiences 
> makes it possible to own these boats without spending a fortune (this 
> 'repair' was going to cost a fortune for the yard to do).

Thanks :)

I'll be curious to read on and see what you did!

Rachel


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