- 01/05/2022 at 11:50 #25270Fairey MaryParticipant
A question to the wise men…
Yesterday I took the chain-plates and bow roller off Mary and in general she is in good condition. I believe the bolts were galvanised probably hardware shop issue and sparing on zinc. I see a bit of the price tag is on one.
However, they were quite difficult to remove and not all they used to be. This is fine they will be replaced. My question relates to the bit I won’t replace, and how to make bolts removal easier in future? The ethos of the question is iron rots wood zinc doesn’t. Is that correct?
The two lower holes vertically aligned are through bolts, The two rusty bolts above. The two upper holes were fixing screws which are unlikely to have had much of a structural impact. These looked like bronze screws (bonus question) which I believe is very bad on a galvanised fitting. Hence it ate all of the wood in contact with the screws and the screws had bonded to the metalwork. There was no chance of just pulling the screws out. These need replacing with galvanised or stainless screws, correct?
So to make this easier in future I wish to drill out and dowel the upper holes. But the lower holes I believe the best solution is to line the holes with resin, basically fill them and drill them out again? There is only one chain plate bolt hole that looks like it could do with some wood letting back in. But this may not be necessary.
Generally when refitting the galvanised bolts, here and on the chain-plates I think I need some form of goop. This is used to fill the air void and avoid decay? Most bolt holes are not too bad and a suitable ‘goop’ would do the job. I am thinking of a heavy grease, one that won’t get absorbed totally into the wood. I don’t think the answer is mastic or sikoflex. I don’t like pulling bolts out that have been glued in with mastic.
It is my preference to seal the wood, paint it, before bolting the fittings on. Maybe paint the fittings separately. Should I use a tar-paper or similar between the fitting and the hull?
Also where to buy replacement bolts with a reasonable amount of zinc on them? Or should I get a job-lot hot dipped? Including re-galvanising the fittings.
- 07/05/2022 at 20:05 #25273Fairey MaryParticipant
I have just read Jonathan’s post on Bluster and see the preference for A2/A4 Stainless. I am tempted, but believe there is a different hardness/frailty. I don’t expect these bolts to suffer fatigue and the idea of shiney bolts with neoprene locking nuts sounds, well ‘shiney’.
My taste to replace with good galvanised bolts is more sticking to what it was/is. After all the fittings are still galvanised.
- 07/05/2022 at 20:05 #25290Nick PhillipsParticipant
The wise men are apparently all on tour. But they left me keeping the teapot charged, so whilst they are away the mouse is going to play….
Sounds like good progress is being made on Mary/
Lots of questions in your post (hope the WM don’t come back before I get to the end).
Not sure if you have seen it but excellent advice on Davey’s website here. And they may be a good source of your fastenings.
Some opinions, rather than facts, follow.
Iron rots wood, zinc does not: not strictly true, but the bolt takes up more space as it rusts which can lead to wood damage which promotes more rust which damages more wood which …… The zinc prevents the rust which protects the wood. Stainless bolts are an option but need care to prevent the wood around them getting wet – with no no access to the air they can rust as fast as mild steel (A4 / 316 grade is better than A2 in wet areas.
These need replacing with galvanised or stainless screws, correct? Yes, I would go stainless, well bedded.
But the lower holes I believe the best solution is to line the holes with resin, basically fill them and drill them out again? If the holes are damaged to the point of allowing the new bolts to move around then filling and re-drilling is an option. Not just resin, but resin plus thickener (colloidal silica, micro-balloons, sawdust ….)
You could also increase bolt diameter and drill to that if you are having the fittings re-galvanised when you drill a larger hole.
Goop. This is used to fill the air void and avoid decay? And prevent leaks! The bolt should be a tight sliding fit in the hole. I would bed the fitting and bolts in a good quality butyl rubber bedding sealant. These remain flexible forever. They are available in builders merchants quite cheaply but it is worth paying a bit more for quality stuff like this one. They are messy but clean up easily with white spirit at any time after fitting. Butyl rubber does not prevent the removal of fittings although some force is required. Certainly do use an adhesive sealant like any of the Sikaflexes or CT1 and definitely not anything with silicon. I would not be happy that any grease would provide a lasting seal.
Maybe paint the fittings separately. If you can re-galvanising is far and away the best option for fittings. It is charged by the kg and will have a minimum weight of 50kg or 100kg – way more than you need. But find a fabricator who often sends stuff for galvanising (e.g. trailer manufacturer?) and they might include your pieces. Simple painting of the fittings will not give the protection of galvanising, even with the so-called ‘cold galvanising’ paints. You could possibly get them blasted and epoxy-sprayed / powder coated by a paint shop?
Should I use a tar-paper or similar between the fitting and the hull? Not necessary if using the butyl rubber sealant.
Off to sweep the floor
- 17/05/2022 at 20:52 #25313Mike DixonParticipant
I bow to the expert’s opinions and suggestions.
Whilst aware that ‘sealed in’ S/S fittings rust alarmingly quickly given the wrong conditions, I have used S/S extensivley on all three Atalanta family boats. T4 is no longer with us, but not because of S/S failures; A31/4 seems to be fine and A1 likewise. Maybe I’ve just been lucky, but for me, using S/S is well worth the marginal risk.
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