[Public-List] Cutlass Bearing Flange Alberg 30

Roger L. Kingsland r.kingsland at ksba.com
Thu Jul 22 09:52:40 PDT 2010 

Albergers,

I am trying to wrap my head around the idea of tapping fiberglass thru which
machine screw (or bolt threads) go.  I assume the "grip" on the screw
exerted by the FG threads would be less than the nut, say, for yucks, half
as much.  So first one must torque the screw head, say to 50 lbs, into the
threaded FG then put the washers and nut on the end and torque the head
and/or nut to 100 lbs.  I suppose it would be possible to 1st torque the nut
to 50 lbs then tighten the head to 100 lbs.  This way, at least in theory,
the FG threads would be snug w/ the nut and the nut threads would take the
additional load that the FG couldn't.  If the head were restrained while the
nut was tightened (more likely w/ a slot or Phillips head) then even a few
turns of the nut would likely strip the FG threads.  

If the justification for tapping the FG is added strength, I would argue
that fasteners alone must be more than strong enough to handle the load,
making the FG threads unnecessary.  Plus another critical component of the
connection is properly distributing the load via a washer and/or backer
plate.  The tapped FG won't help in this regard.

I suppose better waterproofing could be a justification but this would only
occur if the weaker FG threads are not damaged during the installation.
Plus I would not like to rely on simply a tight fit between screw and FG
that might degrade if rigging forces cause them to loosen.  I would be more
comfortable with some kind of "squishy" stuff between the two materials w/
enough room to flex just a little; what about a slight bevel at the top of
the fiberglass hole with an appropriately sized "O" ring around the bolt
shaft that could seat inside the bevel when squished down by a washer or the
base of a piece of hardware?  This might work for highly loaded hardware,
like cleats, that should bedded in epoxy to prevent any movement.  I found
some adhesive, double faced, squishy tape that I put under hatch hinges and
stanchion bases in the hope that, when I tighten the fasteners, the material
will expand and seal around the fastener shafts (keeping my fingers
crossed).  

Food for thought for those like me who agonize over this kind of stuff.  Any
opinions?

Roger 148#         



-----Original Message-----
From: public-list-bounces at lists.alberg30.org
[mailto:public-list-bounces at lists.alberg30.org] On Behalf Of Gordon Laco
Sent: Thursday, July 22, 2010 10:18 AM
To: Alberg 30 Public List -- open to all
Subject: Re: [Public-List] Cutlass Bearing Flange Alberg 30
Importance: High

Good points John - you are correct about SS underwater... Bronze can be iffy
too if the alloy is not correct.

When my cutlass bearing came off I found that one of the bolts had corroded
to the consistency of a biscuit.  It was just crumbly powder under a head
that look fine.  I was able to get the stump out by clipping vice grips on
it and gently turning it out.


Gord #426 Surprise


On 22/07/10 9:52 AM, "John Birch" <Sunstone at cogeco.ca> wrote:

> Hi Peter,
> 
> They are lag bolts, tapped into the glass. There are no inserts.
> 
> Periodically, all bronze bolts underwater should be removed and 
> inspected - perhaps once a decade or so. You should never use SS Bolts 
> (deprived of oxygen, they become active and move the wrong way on the
periodic table.
> 
> Buying silicon or manganese bronze marine bolts is hard to do, go to a 
> reputable supplier - in the Toronto area go to Pacific Fasteners on 
> Chauncey Drive off Islington to make sure you are getting the right 
> bronze or monell fastners.
> 
> There are some instances where drilling and tapping machine screws 
> into fiberglass is helpful to ensure a stronger attachment. One 
> example I've done is the traveler track, another are the winches, all 
> followed with as wide a washer or plate as can be fitted below and 
> then lock washers, thread Locktight and then a nut. It makes for a 
> particularly strong attachment that means the whole glassed area would 
> have to break off - and I cant imagine the load necessary to cause such a
failure.
> 
> The cutlass bearing attachment is threaded on to the bronze shaft 
> tube, which is bedded throughout its internal length in the hull with 
> Dolfinite from the factory, or some other adhesive caulk if 
> retrofitted, then the bearing housing turned onto the threads on the 
> tube and then the housing is bolted into place. I suspect the cutlass 
> housing would do just fine without the bolts, but why test the theory. 
> Ensure the lag bolts are going into solid glass and not into resin 
> starved glass and insert them with lots of caulking on the threads.
> 
> Water migration into the glass will over time degrade the glass. If 
> your holes are degraded, suggest adding a fresh low viscosity epoxy 
> resin to re-wet the glass fibers after ensuring is all dried out.
> 
> Those lag bolts were cut with a tap to create the threads into the glass.
> You cant just drill a hole and use self tapping lag bolts or you'll 
> crack the glass. The holes have to be threaded with a tap set first.
> 
> Caulking is critical to prevent water seepage into the holes, which 
> will eventually break down the resin/glass bond in the area if allowed 
> to seep in.
> 
> Hope this is a help
> 
> Best
> 
> John
> 
> ----- Original Message -----
> From: "Jeffrey" <fongemie at gmail.com>
> To: "Alberg 30 Public List -- open to all" 
> <public-list at lists.alberg30.org>
> Sent: Thursday, July 22, 2010 8:53 AM
> Subject: Re: [Public-List] Cutlass Bearing Flange Alberg 30
> 
> 
>> They screw into the fiberglass. Not sure if there are any inserts or 
>> nuts imbedded in the fiberglass or not. I couldn't tell for sure when 
>> I had mine off this spring. it looked to be just fiberglass.
>> 
>> -jeff
>> 
>> Jeff Fongemie
>> #116 Seagrass
>> 
>> http://picasaweb.google.com/fongemie
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> On Thu, Jul 22, 2010 at 8:30 AM, Peter Milley <milleype at kingston.net>
>> wrote:
>>> 
>>> 
>>> Do the two bolts behind the propeller on the Al 30, holding the 
>>> cutlass bearing flange to the hull just screw into the fiberglass or 
>>> are there nuts behind them on the inside of the hull?
>>> 
>>> Peter Milley
>>> 
>>> _______________________________________________
>>> These businesses support your Association:
>>> http://www.alberg30.org/store/A30supporters.html
>>> Please support them.
>>> _______________________________________________
>>> Public-List mailing list
>>> Public-List at lists.alberg30.org
>>> http://lists.alberg30.org/listinfo.cgi/public-list-alberg30.org
>>> 
>> 
>> 
>> 
>> --
>> Jeffrey Fongemie
>> _______________________________________________
>> These businesses support your Association:
>> http://www.alberg30.org/store/A30supporters.html
>> Please support them.
>> _______________________________________________
>> Public-List mailing list
>> Public-List at lists.alberg30.org
>> http://lists.alberg30.org/listinfo.cgi/public-list-alberg30.org
>> 
> 
> 
> _______________________________________________
> These businesses support your Association:
> http://www.alberg30.org/store/A30supporters.html
> Please support them.
> _______________________________________________
> Public-List mailing list
> Public-List at lists.alberg30.org
> http://lists.alberg30.org/listinfo.cgi/public-list-alberg30.org


_______________________________________________
These businesses support your Association:
http://www.alberg30.org/store/A30supporters.html
Please support them.
_______________________________________________
Public-List mailing list
Public-List at lists.alberg30.org
http://lists.alberg30.org/listinfo.cgi/public-list-alberg30.org



 1279817560.0

More information about the Public-List mailing list