Backyard Renegade wrote:
: Gregg Germain wrote in message
:
: I don't use plywood in my boat building but it's just a wild
: thought. haven't tried anything like that.

: Showoff!

Well I just wanted to be honest that I was making a suggestion that I
never tried. ;^)



--- Gregg
"Improvise, adapt, overcome."

Smithsonian Center for Astrophysics
Phone: (617) 496-1558

I would taper the relief rather than have the relief end in an abrupt
cut edge 3 inches in from the end.
Is the bulkhead going to be painted? If it is then is won't really
matter if there is some variation in the inboard edges of the fillet.
I hate routers. noisey, dusty, too fast, and hard to control unless you
set up a jig.
I'd draw a line three inches back from the edge and hand grind a taper
with a disk grinder( also noisey and dusty but easier to control by
hand) being careful not to take off any wood beyond the
line. Use the glue line in the plywood to judge eveness of depth.
You could also bevel the edge off with a power plane or even a hand jack
plane if you are good at sharpening one.(sharpening the blade is the
secret) If you have a lot to do the hand plane would be tedious.
All this assumes that you are bonding the entire perimeter of the
bulkhead to the hull rather than just short little tab angles. I've seen
it both ways and I can't really tell from what you wrote. If using
multiple short tabs, I'd use a really sharp slick (a wide flat chisel
with a long handle) to bevel slots that the tabs would be built in.

By the time you figure out how to build a jig for the router, hand
grinding it with a disk sander would have it done.
The inboard edge of the glass "fillet" can be faired with micro baloons
and epoxy but if you use strips of glass cut from a sheet of fabric on
the diagonal, you will not have to deal with the hard edge of glass
tape. Cutting on the diagonal keeps the fabric from fraying and orients
the fiber correctly for this aplication.
Actually, you can fillet the bulkhead to the hull without cutting a
recess at all. The glass is not all that thick that it can't be faired
to the flat of the plywood so that it can't be seen if painted. Either
way will require some fairing and sanding to achieve a smooth joint.
SteveJ

mike worrall wrote:
Imagine a freshly cut-out plywood bulhead lying horizontaly on a table
before you. The bulkhead will be attached to, or installed into the
fiberglass hull using 'bonding angles' i.e., several layers of 'glass
/ epoxy that will lap onto both the bulkhead and hull. I'd like to
relieve, or remove, about 1/8" of the plywood (face) material all
along the edge of the bulkhead (where it will bond to the hull) for
(say) 3" from the edge on both sides of the bulkhead. In this way,
the 'glass angles will lie flush with the bulhead surface.

How do I do this? That is, wat tool(s) would be used for removing the
plywood, leaving a clean cut of consistent depth?

Appreciate any tips.

Mike Worrall
Los Angeles

Table saw, or circular hand saw with fence. Set for 1/8" depth,
3" rip, and glide the saw free hand side to side. You may want to
set the fence on the wrong side. Then, finish with a wide flat
face chisel. Work up to a scored boundary segmented with a box
cutter, or leave it tapered.

Why bother? Raw fiberglass is so enabling. You can see a
suggestion of woodgrain through it, and integrity inspections are
*so* easy and hull liner materials like shag carpet are *so*
concealing, as is hull paint.

Terry K

mike worrall wrote:

Imagine a freshly cut-out plywood bulhead lying horizontaly on a table
before you. The bulkhead will be attached to, or installed into the
fiberglass hull using 'bonding angles' i.e., several layers of 'glass
/ epoxy that will lap onto both the bulkhead and hull. I'd like to
relieve, or remove, about 1/8" of the plywood (face) material all
along the edge of the bulkhead (where it will bond to the hull) for
(say) 3" from the edge on both sides of the bulkhead. In this way,
the 'glass angles will lie flush with the bulhead surface.

How do I do this? That is, wat tool(s) would be used for removing the
plywood, leaving a clean cut of consistent depth?

Appreciate any tips.

Mike Worrall
Los Angeles

--
Terry K - My email address is MY PROPERTY, and is protected by
copyright legislation. Permission to reproduce it is
specifically denied for mass mailing and unrequested
solicitations. Spamspoof salad by spamchock TM - SofDevCo ®

mike worrall writes:

Imagine a freshly cut-out plywood bulhead lying horizontaly on a table
before you. The bulkhead will be attached to, or installed into the
fiberglass hull using 'bonding angles' i.e., several layers of 'glass
/ epoxy that will lap onto both the bulkhead and hull. I'd like to
relieve, or remove, about 1/8" of the plywood (face) material all
along the edge of the bulkhead (where it will bond to the hull) for
(say) 3" from the edge on both sides of the bulkhead. In this way,
the 'glass angles will lie flush with the bulhead surface.

How do I do this? That is, wat tool(s) would be used for removing the
plywood, leaving a clean cut of consistent depth?

Lots of ways to do it buy why bother?

You are going to be using glass and fairing compound to bond the bulkheads
to the hull anyway.

The proper size beer bottle to form the fillet is probably of more
concern.G

BTW, even my smallest bulkhead had to be assembled inside the hull.

These bulkheads were constructed using two (2) pieces of 1/2", 4 ply, CDX,
temporally screwed together on the layout table to form a blank, some of
which were 12 ft x 16 ft, using 4x8 sheets, then laid out using a tick stick
and trimmed to size.

Finished bulkhead is now disassembled, carried up into the boat, piece by
piece, and reassembled using low cost steel deck screws and wood glue.

The assembled bulkhead is now located in the hull with blocks that have been
temporally attached to the hull with deck screws and tabbed to the hull with
scrap glass pieces. (One layer of 24 oz double bias).

When cured, the blocks are removed and the rest of the bulkhead is now
glassed to the hull.

When cured, fairing compound is used to fill all voids between hull and
bulkhead and a layer of glass is laid over the compound to form a fillet
using said beer bottle on the other side of the bulkhead.

When cured, sand down plywood and the glass fillet edges, seal with 2 coats
of epoxy, sanding between coats, then laminate two (2) layers of 24 oz
double bias glass on each side of the bulkhead.

After that, it's time for high build primer followed by LPU.

It's working for me.

HTH


--
Lew

S/A: Challenge, The Bullet Proof Boat, (Under Construction in the Southland)
Visit: http://home.earthlink.net/~lewhodgett for Pictures

Some very good methods have been sugested which made some good reading.
However, assuming you are using 3/4" ply, these 1/8" reliefs will remove
about 1/3rd of the thickness and could(will) creat a stress point where the
1/2" thich relieved section butts to the full 3/4" section of the bulkhead.
If this is a sizeable boat, and the bulkheads are tied into members that
will introduce sort of a parrellogram like stress ( cabin floors, decks,
ect) the working of the stress aforementioned stress point could , over
time, delaminate the plys? Anyway, it's just a thought to consider. It would
look slick but possibly at a cost. I doubt the such a delamination would
have seroius structural consequences, but it might not be pretty.
Delamination or not, certainly it would create a good flex point to crack
your faired out smooth bulkheads to have cosmetic cracks. ( sorry
spellchecker isn't working, got to fix that!)

--
Ron White
Boat building web address is
www.concentric.net/~knotreel

The relief near the edge of the bulkhead should taper to zero, as should the
tabbing.

Ron White wrote:

Some very good methods have been sugested which made some good reading.
However, assuming you are using 3/4" ply, these 1/8" reliefs will remove
about 1/3rd of the thickness and could(will) creat a stress point where the
1/2" thich relieved section butts to the full 3/4" section of the bulkhead.
If this is a sizeable boat, and the bulkheads are tied into members that
will introduce sort of a parrellogram like stress ( cabin floors, decks,
ect) the working of the stress aforementioned stress point could , over
time, delaminate the plys? Anyway, it's just a thought to consider. It would
look slick but possibly at a cost. I doubt the such a delamination would
have seroius structural consequences, but it might not be pretty.
Delamination or not, certainly it would create a good flex point to crack
your faired out smooth bulkheads to have cosmetic cracks. ( sorry
spellchecker isn't working, got to fix that!)

--
Ron White
Boat building web address is
www.concentric.net/~knotreel