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-   -   rubber washer for keel bolts (http://www.sailnet.com/forums/general-discussion-sailing-related/12503-rubber-washer-keel-bolts.html)

alan.b 02-20-2006 03:05 AM

rubber washer for keel bolts
 
I am a student in the UK and I have to complete assignment for my course work which I have to ask for expert advise, I would be greatful for any help.
The question is which rubber for washers you would use to to fix in keel bolts and why?
Many thanks for any advise

Jeff_H 02-20-2006 07:19 AM

I don't think that I would use a rubber washer under a keel bolt. Keel bolts need to be torqued tp a very high tension. They need to maintain this tension through a pretty wide range of loadings with negligible elongation. That would discourage the use of a compressible washer. If a comperssible washer had to be used, I would think that urethane washer would be the best material for that purpose. Urethane can be specified in a range of stiffness, and I would guess that the least compressive urethane might work. Urethane can be ordered in a formulation that is stable with prolonged exposure to water. With some Urethanes are some issues when exposed to petrochemicals for prolonged periods as might accidently happen in a bilge.

Jeff

Silmaril 02-20-2006 08:02 AM

A thought...
 
I agree with Jeff 100% for using washers inside the hull, under the nuts for the keel bolts.

In a completely "Outside the box" thought, you COULD use rubber washers, if the intent was to make the holes water tight in this fashion, although I can find no practical reason anyone would.

If this is truly for course work, and for theoretical use only:

One could use rubber washers, of a stable rtv silicone type, if the keel had shallow machined cavities for the washers around the keel bolts, where the cavity was designed so that the washer formed a slight compression seal around the bolt and the hull as the keel bolts were tightened from above. The cavity SHOULD NOT be machined into the hull, as this would weaken the hull under the nuts for the keel bolts. This whole process would be too labor intensive in practicality, but as an answer to a classroom question, that is how I would do it.

paulk 02-20-2006 08:43 PM

Rubblebars
 
When we raced as youngsters, we often thought it great fun to sail by other boats and advise them (with great concern) that their rubbblebars were loose. Leaving it to our competitor to determine exactly what a rubblebar was, and how to tighten it. Suggesting the use of rubber washers for keelbolts would seem to fall under the same situation: a total fallacy. Rubber is called for when compressible or elastic qualities are needed because things are moving. A keel, by definition, is something you do NOT want to move - the rest of the boat is built upon it! If it is moving, it is going to leak - this is the problem the Volvo RTW boats are having right now; their keels are moving and water is getting in. Perhaps a rubber GASKET, which would compress and keep water out, would be indicated in a hull/keel joint, but this is not the question you posed. Individual washers on a standard keel would not perform the same way and would probably serve to create leaks because of the differences in the tightened spaces and how they would allow the keel to work, because of their compressibility. I would suggest going back to your professor and asking for clarification of this issue. Sounds like he's sending you to look for the head keelson spanner- a standard joke for the newest crew on a submarine.

d kleitz 02-21-2006 10:47 AM

keel bolts iin usa have stainles steel lock washers
they are torqued to large ft lbs, this crush rubber
del kleitz catalina 27


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