How much faith in Loctite?

cjepearson

cjepearson

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I have to fit a new locking nut to my prop shaft to secure my new, expensive feathering prop. The snag is that the boss of the new prop overlaps the hole for the split pin, so I may have to use Loctite to hold the nut on. Is this a jolly good idea? Would it be man enough for the job? I could get an engineering workshop to "castle" the nut, but it would means drilling a new hole in the shaft (having removed the rudder to remove the shaft) Ditto for fitting a grub screw. Loctite would be a whole lot easier.
 
Do you have room for a washer? If so, fit a tab washer, with one tab into the keyway groove, and the other tab over one flat of the nut. That is the way my prop nut is kept on.

You can make a tab washer yourself from a 2 mm piece of brass sheet - as I had to do. The i.d. the shaft size, and the o.d. the prop nut (flat) size.
 
Loctite threadlock is pretty good stuff, but you can't beat a foolproof mechanical method where secure attachment is concerned. Drilling a hole through your shaft, and through the nut if necessary, is a job many competent engineering companies could do for you in situ. If that fails there are companies who specialise in this type of work. I would try the yard where the boat is ashore as a first option and take it further if they cannot do it.
 
Loctite 243 is the one for underwater securing of threads and has been used for my folding prop and for holding anode nuts and bolts.

But as the other posts have suggested a mechanical solution is always the best
 
'Loctite' isn't particularly meaningful -- there are many grades for different applications, all described on their website. Used correctly it's good stuff, but I'd hesitate to depend on it alone in such a critical application. Would it be possible to drill and tap one of the flats of the nut to take a grubscrew? Or alternatively drill the nut to take lock wire to a tab washer or to the prop itself?
 
this is one of those posts where we all look into our navels and see how much fluff is in there for christ sakes!!
loctite, enormous company, enormous R&D, know their stuff, used by manufacturers all over the world to lock products in place. only caveat you have to use the product designed for the job, ok the thumblethumbs dont understand it so they recommend their bit of navel fluff, but if you are worried about it get an electric drill and drill a bloody hole through the nut and split pin it (10 minutes) or do what one of the other posters has suggested and make a lock tab. if you dont understand or cant do either, pay some one to do it for you, easy peasy. if it is of any consequence by the way i have had more than my fair share of heaving on a cheater bay on a socket trying to break a loctited threaded component loose!! think brake calipers on most new cars, bolt holding them on only thing between you and no brakes is some blue thread locking compound!!
 
I use the tab washer method which works well. Any company which deals with shafts and props will sell you one. Do not be tempted to try and drill through the nut and shaft yourself unless you have some experience. It is remarkably difficult to do it accurately and you could well break the drill, to boot.
 
Just a thought. How much of the threaded end of the shaft projects beyond the nut, with the new prop in place? I ask because the strength of a screw threaded connection depends upon some of the "bolt" projecting beyond the nut in order to return part of the tightening stresses to the core of the bolt. Some authorities claim that to achieve full strength in a threaded connection a length of bolt equal to half its core diameter should project beyond the outer face of the nut. If this is the case, then there should be room to drill a new hole for a split pin.
 
The new nut only leaves about 5mm of shaft protruding, and the nut is recessed into the boss of the prop so there is very little room to play with. There is no way I will try to drill through the nut and shaft in situ(I know my limitations all too well) Sounds like a professional job to me.
 
If the prop is a good tight fit on the taper, with a tightly fitted key allowing no rotation relative to the shaft I would go with Loctite, but be careful to get advice as to the correct grade. At some stage you will probably need to get it off, and the hard setting varieties will need a lot of heat to soften them for removal, which may be a No-No if the prop cannot take the application of a big blowlamp to the nut. I cannot advise on grade to use because Loctite have changed a lot of their numbers since I was familiar with them.
 
Loctite has as a component Cyanocrilate (Super Glue) .... this breaks down in water.

Honest opinion ? - Get it sorted properly - Loctite is not the answer.
 
[ QUOTE ]
Cyanocrilate

[/ QUOTE ] Cyanoacrylate..............but you knew I'd correct it!

Got to agree though the Loctite website does not seem to list any grade suitable for underwater use.

Philip Stevens idea of a locking tab washer is a good one so is a Nyloc or other self locking nut.
 
Just a thought...

Some grades of stainless suffer from crevice corrosion under water. This is, apparently, because they need oxygen to maintain their oxide layer which prevents them from corroding. Surely Loctite (or any similar compound) will prevent oxygen from reaching the metal surface? If that happens, should we even be Loctiting stainless fasteners above the waterline?
 
If the water is excluded then there should be no problem. Its important to make sure water cannot penetrate under deck fittings and get at the threads of fastenings.

Inverted U bolts commonly used for shroud anchorages are seriously at risk. We were lucky not to lose the mast a few years back when one failed due to crevice corrosion where it passed through the deck. A second failed as I tried to undo the nuts! Two others which had been removed and rebedded some years earlier were in perfect condition.
 
As the discussion has moved to thread lock properties...

From our experience of fitting sterng gear compnents, we advise the use of Araldite precision or 2011 resin. This is a low temperature slow setting epoxy, it is also resistant to water and protects the threads from crevice corrosion by keeping the water out.

To dismantle any components bedded with this epoxy, the parts can be heated and the epoxy softens, we use this to hold in bearings and threaded components, that other wise lossen from vibration.
 
[ QUOTE ]
[ QUOTE ]
Cyanocrilate

[/ QUOTE ] Cyanoacrylate..............but you knew I'd correct it!

Got to agree though the Loctite website does not seem to list any grade suitable for underwater use.

Philip Stevens idea of a locking tab washer is a good one so is a Nyloc or other self locking nut.

[/ QUOTE ]

Ta ... my speeling after a few Vodkas goes to rat-s****


I'm always wary of any liquid answer to something that should be mechanical ... when it is to submerged and is an important item.
 
A parallel but relevant experience: my Volvo 120 S leg has, like all S legs, a prop of course held in place by a cone that screws onto the shaft. What holds it all together? A long thin SS hx bolt threading thought the cone and into the shaft. What holds it in place? Loctite. Every year since the boat was launched - never a problem the whole season long, despite all the theoreticals such as continuous vibration and loading changes etc.

I am not minded to start extra drdilling for the theoretical advantage of yet another mechnical advantage.

PWG
 
A parallel but relevant experience:

My Volvo 120 S leg has, like all S legs, a prop of course held in place by a cone that screws onto the shaft. What holds it all together? A long thin SS hex bolt threading though the cone and into the shaft. What holds it in place? Loctite. Just like all the Volvo 120 shafts.

Every year since the boat was launched - never a problem the whole season long, despite all the theoreticals such as continuous vibration and loading changes etc.

I am not minded to start extra shaft drilling for the theoretical advantage of yet another mechnical advantage.

PWG
 
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