Aries wind vane 'fix'

[maxiSwede]

Got a 'minor' problem that needs attention before next departure. And I know you are quite some smart 'fixers' here so let's have a brainstorming. ;D

Problem identification:

Older vane, works great. The attachment to the stern of Röde Orm is two (over)sized aluminum alloy tubes (on the vane gear) fitting into two other, slightly larger tubes on the stern. The attachment is secured by two 8 mm SS bolts on each side through both tubes.(Sb and Bb) Over the years I guess those bolts have slowly worked on  the holes to become bigger or even oval in shape. I want to stop this movement before it wears the tubes out completely.

The alternatives I have come up with this far:

1)
drill the holes a bit bigger in diameter and go for larger bolts - temporary fix, and what do I do next time around??  ???

2)
drill the holes bigger and have a machine shop make 'innerlining' (don't know the correct term in English for this) in aluminum that fits the bolts nicely.  Seems great in theory, but still makes corrosion between SS and alu a something to fear.  :P

3)
Use some thin nylon stuff as a ' lining' between the alu tubes and the bolts. That wouldn't cost a fortune, and I could easily cut them out myself whenever I would need them in the future... ::)


....so, what do all of you think.... I am pretty sure there is a fourth and a fifth alternative too, and just maybe the sixth one would be the best. 8)

cheers, Magnus

[CharlieJ]

I THINK for the"inner lining" you speak of you are referring to what I would call a "compression tube"

I commonly use these when through bolting things such as spreaders to masts or bails on booms.

You obtain a stainless tube just large enough for the bolt, then drill the main tubing ( both pieces) to fit the OD of the stainless compression tube.. Cut the compression tube EXACTLY the length as the outside diameter of the largest tube.

Put the two main tubes together, slide the compression tube through the hole in both, put a large washer on the bolt, slide the bolt through the  compression tube, add another washer, then the nut.

Now you can tighten the nut on the bolt very tightly, as all of the loading will be on the compression tube. The sheer loads are transferred to the OD of the compression tube, which is in affect, a much larger bolt then. 

Done correctly, there should never again be any movement there.

[maxiSwede]

Thanks, Charlie. Your suggestion makes sense. Just out of curiosity, why make the compression tubes (thanks for the correct word, too ;D) in stainless instead of aluminum?.

My guess is that the reason would be sheer strength....

and the potential issue of corrosion on the alu due to contact with stainless steel could be addressed by painting the inside of the holes in the aluminum tubes, or by lubricating them.

Yes, seems like the way to go. Thanks again. :)

[Fortis]

I would go with the tube (not actually a compression tube, actually called a sleeve int his application), but I would go with one of the high tech plastics like vesconite.

It totally gets rid of corrossion between ss and aluminium, it prevents the holes int he base plates ever wearing as you just doa  five year check on the vosconite and replace as needed. DO NOT got with nylon for the lseeve or bushing as nylon absorbs a surprising amount of water and swells (is nto dimensionaly stable) this stresses bolts that are torqued too tight to it. Vescontie and similar are 99.999% dimensionally stable and specifically designed as anti-wear surfaces.
Just machine up ten or twenty at a time and then don't lose the baggy with the spares!

My personal aproach to making sleeves like this is to also machine up some washers of vesconite. That creates a mushroom type cap for the bolts to press down on and again, goes even further to prevent corrossion.

Alex.

[CharlieJ]

yes, because of the corrosion issue- Where you plan to use it is going to be wet often with salt water, so similar metals would seem to be suggested. I would be very reluctant to use aluminum.

Alex, I've never heard the term "Vesconite" tell me more about it. Is there another common name, perhaps a different one here?

[maxiSwede]

Thanks Alex.

May I wish you a quick recovery!  It seems dangerous to have kids, haha.

Anyhow, what you say makes sense. I had no idea of nylon absorbing water...

Like Charlie, I have never heard of 'vesconite' either. That is a trade name I guess, wonder what the chemists calls it, and where to get it.  ???

[AdriftAtSea]

Vesconite is one of the high-density, low friction polymers developed to make parts for the marine industry.  Delrin and torlon are quite similar IIRC.  Any of the three would work in this situation.

[CharlieJ]

Thanks- I'm familiar with both Delrin and Torlon.

[maxiSwede]

So am I. Thanx again

[maxiSwede]

So, just a bit over a year later, this little project is successfully dealt with. the main reason it took me so long - well despite the fact I am a lazy son of a :::. - is that I had a h--l of a time trying to find the suitable material.

Thanks again everybody who took time to give me very useful advice!

[AdriftAtSea]

Thanks for the update..