[Public-list] Hull/deck fixing

[Roger L. Kingsland]

Peter,

Don't tell the traditionalists, but I don't plan to have a toe rail or taft
rail aft of the primary winch.  The advantage of countersinking the hull to
deck fasteners is the finish surface doesn't require a "cap."  Plus, no
leaks (hope springs eternal)!

I would think the bolt heads you inquired about would be thicker than the
deck flange that overlaps the flange at the top of the hull.  I countersunk
3/16" stainless rivets at 4'' OC which were easy to cover with epoxy.  The
rivets are almost as strong as the 3/16" SS bolts they replace and, since
the spacing is closer, the net strength is greater (I used about 200).  The
nice thing about the rivets is the heads are so thin you don't have to drill
deep countersink holes.  Plus, it is a "blind fastener" so one person can do
it from the deck.

I used a router to control the depth and location of the holes and had a
1/2" high steel rod (equal to the diameter of countersink
the hole) machined with a hole equal to the rivet diameter in the center.
That way I could center the rivet holes in the countersink (or countersunk?)
holes.

Send me your email (mine is rkingsland101 at ksba.com) and I will send some
photographs. I special ordered the rivets and think I have enough left over
to do a second boat.  If you would like to use them; I will give you a good
deal.  If you do this, make sure to buy or rent a heavy duty (preferably
hydraulic) rivet machine.  I killed three hand powered machines doing my job
and my hand was sore and bruised for a week.

Relative to other responses on this thread, I agree with C.B. Currier as to
the limited structural function of the rivets.  Aluminum rivets,
particularly the tiny ones used #148, have little strength and don't hold up
to salt water.  It appears they were used primarily to hold the joint in
place while the resin dried.  In addition to this chemical connection, it
appears the primary mechanical fastener is the 3/16" bolts that also hold
the toe rail.  Because these are shear connections (rather than friction
connections) they don't add much strength beyond the immediate area around
the hole through the deck.  I partially agree with C. B. regarding the loss
of friction area by countersinking rivets but feel (without any facts to
back me up) if the countersinks holes are shallow are filled with epoxy, the
reduction will be minimal.  If the holes are under the toe rail, mike
Lehman's technique of using 5200 to fill in the countersink holes seems
logical (and now I have to worry about cracking of the epoxy filler I
used ).  However, because rivets make a friction connection and screws a
shear connection, I would prefer rivets.

That's my 50 cents.

Roger Kingsland


----- Original Message ----- 
From: "Peter Amos" <p.a.amos at tesco.net>
To: <public-list at alberg30.org>
Sent: Monday, August 30, 2004 10:20 AM
Subject: [Public-list] Hull/deck fixing


> Is it safe to use countersink bolts to replace the pop rivets in the
hull/deck joint?I am wondering if countersinking the bolt holes will weaken
the fibreglass of the deck flange too much.
> Peter Amos
> TaitTait #478
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> Public-list at alberg30.org
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