Re: [bolger] Re: plywood scarfing using a small electric grinder
> hallow out the face the one or two layers and fill that with epoxyAlso sometimes called the 'Payson Butt' joint.
> and glass.
Bolger specifies this type of butt joint on Topaz, for joining four 8
foot sheets into one long 32 foot panel. It works great, and has the
advantage of not wasting panel length. Scarfed, four sheets of
plywood would measure up only 30+ feet long.
In short, using a grinder, you dish out wood, and replace with epoxy
and a thick glassing. I used triple layer, totally about 26 oz. (each
side). Two layers of 10 oz biaxial tape in the dished recess, plus the
full surface covering with 6 oz cloth. Easy, strong, and perfectly
smooth and seamless.
(A trick I used, was to nail the plywood butt ends to a sawhorse,
using silicon bronze copper nails, with each panel end butt together
resting on the same sawhorse. Then I dished and glassed/epoxy right
through the nail heads. After cure, flipped it over, kicked off the
sawhorse, and grind off the nails. This held the panel ends tighter,
and flusher, better than trying to figure out how to clamp such
awkward large panels.)
I recall enough about 'extreme fiber bending stress' from structural
engineering class at the University to be assured that this 'Payson
Butt' joint is as strong or stronger than a scarf.
Grinder, belt sander or electric hand plane will all do it. Stagger
the sheets by the distance you want to scarf them with a piece of scrap
beneath. Your can also buy a scarfer attachment from West Marine for a
7 1/4" circular saw. I have used both methods and prefer the plane for
thicker plywood, scarfer for thinner stock
Paul H.
--- Inbolger@yahoogroups.com, "Robert Paquette" <robertpaquette@...>
wrote:
the sheets by the distance you want to scarf them with a piece of scrap
beneath. Your can also buy a scarfer attachment from West Marine for a
7 1/4" circular saw. I have used both methods and prefer the plane for
thicker plywood, scarfer for thinner stock
Paul H.
--- Inbolger@yahoogroups.com, "Robert Paquette" <robertpaquette@...>
wrote:
>
> Hi,
> Someone a while back had mentioned that it was a simple procedure to
> scarf two sheets of plywood using an electric hand-held grinder. I've
> searched the archives but I was unable to find the posting. Does
> anyone know of such a procedure?
> Robert
>
I know a couple of people that use the epoxy and
buttstraps on the back side and then hallow out the
face the one or two layers and fill that with epoxy
and glass.
I saw a couple of their boats and they looked fair at
the joints.
Krissie
The fish are biting.
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buttstraps on the back side and then hallow out the
face the one or two layers and fill that with epoxy
and glass.
I saw a couple of their boats and they looked fair at
the joints.
Krissie
> What you may be thinking of is Dynamite Payson's____________________________________________________________________________________
> 'Fiberglass
> Butt-Joint'. It really isn't a scarf, or
> 'traditional' butt joint,
> either. The usual 'Butt Joint' is basically
> 'sistering' two planks, or
> sheets of plywood, together. Slather the ends with
> glue/epoxy and a
> couple inches of the 'face', put on a piece of ply
> {about 6-8in wide}
> over the joint and nail/screw it down. The 'first
> variation' was to
> substitute a layer of fiberglass for the piece of
> ply, and do it on both
> sides. The 'second variation' - HERE the
> 'grinder/drill disk' comes in -
> was to glue the ends together and let dry/cure. Then
> 'sand out' a
> shallow curve{about the thickness of 1-2 layers of
> veneer}, centered on
> the joint. Then the area was filled with layers of
> epoxy saturated
> fiberglass - narrow on the bottom, and wider as
> filled - the last
> 'overlapping' onto the face of the ply. Again, this
> was done to BOTH
> sides.
>
> A true 'scarf joint' will reduce the overall
> additive length of the ply
> sheets {or planks}that are being used. How much -
> depends on the 'slope
> ratio' of the scarf. If you have just two '4x8'
> sheets, and your budget
> doesn't allow for more, and you *must' have a 16ft
> piece -the
> 'Fiberglass Butt' is your option. The caveat is . .
> . there is the 98
> percent probability that the joint will 'flag'
> through the finish . . .
> especially a gloss one.
>
> Regards & Good Luck,
> Ron Magen
> Backyard Boatshop
>
> > 6. plywood scarfing using a small electric grinder
> > Posted by: "Robert Paquette"
>robertpaquette@...
> paquetterobert
> > Date: Sun Apr 8, 2007 7:43 am ((PDT))
> >
> > Hi,
> > Someone a while back had mentioned that it was a
> simple procedure to
> > scarf two sheets of plywood using an electric
> hand-held grinder. I've
> > searched the archives but I was unable to find the
> posting. Does
> > anyone know of such a procedure?
> > Robert
>
>
The fish are biting.
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Robert . . .
DON'T do it . . . Not with one of those 4-1/2in, or 'Drill Mounted Disk'
grinder/sander.
With a 'disk' you will have the problem of 'scalloping' the scarfed
surface. It *can* be done, but it takes a lot of time and a LOT of care.
If you want to do the *entire job* by sanding . . . use a belt sander. I
have a Royobi that is similar to a Bosh - rather long & 'flat'. Very
well 'balanced' for this type of operation. Simply mark & 'stair-step'
the panels, then GENTLY apply the sander till you get an 'even slope'.
Get a 'Klingspore' catalog and look for 'PLANER' belts. Use 60 grit -
the 'texture' holds the epoxy.
What you may be thinking of is Dynamite Payson's 'Fiberglass
Butt-Joint'. It really isn't a scarf, or 'traditional' butt joint,
either. The usual 'Butt Joint' is basically 'sistering' two planks, or
sheets of plywood, together. Slather the ends with glue/epoxy and a
couple inches of the 'face', put on a piece of ply {about 6-8in wide}
over the joint and nail/screw it down. The 'first variation' was to
substitute a layer of fiberglass for the piece of ply, and do it on both
sides. The 'second variation' - HERE the 'grinder/drill disk' comes in -
was to glue the ends together and let dry/cure. Then 'sand out' a
shallow curve{about the thickness of 1-2 layers of veneer}, centered on
the joint. Then the area was filled with layers of epoxy saturated
fiberglass - narrow on the bottom, and wider as filled - the last
'overlapping' onto the face of the ply. Again, this was done to BOTH
sides.
A true 'scarf joint' will reduce the overall additive length of the ply
sheets {or planks}that are being used. How much - depends on the 'slope
ratio' of the scarf. If you have just two '4x8' sheets, and your budget
doesn't allow for more, and you *must' have a 16ft piece -the
'Fiberglass Butt' is your option. The caveat is . . . there is the 98
percent probability that the joint will 'flag' through the finish . . .
especially a gloss one.
Regards & Good Luck,
Ron Magen
Backyard Boatshop
DON'T do it . . . Not with one of those 4-1/2in, or 'Drill Mounted Disk'
grinder/sander.
With a 'disk' you will have the problem of 'scalloping' the scarfed
surface. It *can* be done, but it takes a lot of time and a LOT of care.
If you want to do the *entire job* by sanding . . . use a belt sander. I
have a Royobi that is similar to a Bosh - rather long & 'flat'. Very
well 'balanced' for this type of operation. Simply mark & 'stair-step'
the panels, then GENTLY apply the sander till you get an 'even slope'.
Get a 'Klingspore' catalog and look for 'PLANER' belts. Use 60 grit -
the 'texture' holds the epoxy.
What you may be thinking of is Dynamite Payson's 'Fiberglass
Butt-Joint'. It really isn't a scarf, or 'traditional' butt joint,
either. The usual 'Butt Joint' is basically 'sistering' two planks, or
sheets of plywood, together. Slather the ends with glue/epoxy and a
couple inches of the 'face', put on a piece of ply {about 6-8in wide}
over the joint and nail/screw it down. The 'first variation' was to
substitute a layer of fiberglass for the piece of ply, and do it on both
sides. The 'second variation' - HERE the 'grinder/drill disk' comes in -
was to glue the ends together and let dry/cure. Then 'sand out' a
shallow curve{about the thickness of 1-2 layers of veneer}, centered on
the joint. Then the area was filled with layers of epoxy saturated
fiberglass - narrow on the bottom, and wider as filled - the last
'overlapping' onto the face of the ply. Again, this was done to BOTH
sides.
A true 'scarf joint' will reduce the overall additive length of the ply
sheets {or planks}that are being used. How much - depends on the 'slope
ratio' of the scarf. If you have just two '4x8' sheets, and your budget
doesn't allow for more, and you *must' have a 16ft piece -the
'Fiberglass Butt' is your option. The caveat is . . . there is the 98
percent probability that the joint will 'flag' through the finish . . .
especially a gloss one.
Regards & Good Luck,
Ron Magen
Backyard Boatshop
> 6. plywood scarfing using a small electric grinderpaquetterobert
> Posted by: "Robert Paquette"robertpaquette@...
> Date: Sun Apr 8, 2007 7:43 am ((PDT))
>
> Hi,
> Someone a while back had mentioned that it was a simple procedure to
> scarf two sheets of plywood using an electric hand-held grinder. I've
> searched the archives but I was unable to find the posting. Does
> anyone know of such a procedure?
> Robert
Hi,
Someone a while back had mentioned that it was a simple procedure to
scarf two sheets of plywood using an electric hand-held grinder. I've
searched the archives but I was unable to find the posting. Does
anyone know of such a procedure?
Robert
Someone a while back had mentioned that it was a simple procedure to
scarf two sheets of plywood using an electric hand-held grinder. I've
searched the archives but I was unable to find the posting. Does
anyone know of such a procedure?
Robert