I'm currently working on a Phil Bolger designed plywood sailing pirogue (the
CSD one). Even though the original design calls for a lee-board, I can't
leave well enough alone and am planning on an off-centre centre-board.

My question is about protecting the hull bottom at the centre board slot.
On previous boats (with a dagger-board), I just added some fibreglass tape
around and overlapping the slot, but I was wondering for this one if perhaps
some sort of shoe would be appropriate, and if so what (inexpensive and easy
to find) materials might be suitable. I'm intending on using this boat in
locations where I will have to paddle up a rocky river to a sailable lake.

Thanks

--
Andrew Butchart

http://www.floatingbear.ca

I put a plywood "shoe" over the slot on the bottom of the Dogskiff after
the screws pulled through the thin face ply on the lauan underlayment.
There's a photo and writeup on my website (see below) under "Boats",
"Dogskiff", "Sailing Rig".

"Andrew Butchart" ) writes:
I'm currently working on a Phil Bolger designed plywood sailing pirogue (the
CSD one). Even though the original design calls for a lee-board, I can't
leave well enough alone and am planning on an off-centre centre-board.

My question is about protecting the hull bottom at the centre board slot.
On previous boats (with a dagger-board), I just added some fibreglass tape
around and overlapping the slot, but I was wondering for this one if perhaps
some sort of shoe would be appropriate, and if so what (inexpensive and easy
to find) materials might be suitable. I'm intending on using this boat in
locations where I will have to paddle up a rocky river to a sailable lake.

Thanks

--
Andrew Butchart

http://www.floatingbear.ca




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Depends on how rocky the river is, how much weight you can tolerate, and your
definition of inexpensive.
If you plan to bump rocks a lot, the drift boat solution of cladding the bottom
with a tough plastic such as HDPE or UHMW might be warranted. Not light and not
real cheap.
Next less extreme would be glass in epoxy. A little graphite in the epoxy will
reduce friction on rocks and toughen the epoxy a bit.

Have you asked the designer? He's just full of clever ideas.


Andrew Butchart wrote:

I'm currently working on a Phil Bolger designed plywood sailing pirogue (the
CSD one). Even though the original design calls for a lee-board, I can't
leave well enough alone and am planning on an off-centre centre-board.

My question is about protecting the hull bottom at the centre board slot.
On previous boats (with a dagger-board), I just added some fibreglass tape
around and overlapping the slot, but I was wondering for this one if perhaps
some sort of shoe would be appropriate, and if so what (inexpensive and easy
to find) materials might be suitable. I'm intending on using this boat in
locations where I will have to paddle up a rocky river to a sailable lake.

Thanks

--
Andrew Butchart

http://www.floatingbear.ca

Jim Conlin wrote:
Depends on how rocky the river is, how much weight you can tolerate, and your
definition of inexpensive.
If you plan to bump rocks a lot, the drift boat solution of cladding the bottom
with a tough plastic such as HDPE or UHMW might be warranted. Not light and not
real cheap.
Next less extreme would be glass in epoxy. A little graphite in the epoxy will
reduce friction on rocks and toughen the epoxy a bit.

I've used a graphite/epoxy coating on a centerboard, it's a tough &
slick finish. Hard to beat IMHO. It ain't cheap though, and it takes
more than "a little."

Fresh Breezes- Doug King

"Andrew Butchart" wrote in message .. .
I'm currently working on a Phil Bolger designed plywood sailing pirogue (the
CSD one). Even though the original design calls for a lee-board, I can't
leave well enough alone and am planning on an off-centre centre-board.

My question is about protecting the hull bottom at the centre board slot.
On previous boats (with a dagger-board), I just added some fibreglass tape
around and overlapping the slot, but I was wondering for this one if perhaps
some sort of shoe would be appropriate, and if so what (inexpensive and easy
to find) materials might be suitable. I'm intending on using this boat in
locations where I will have to paddle up a rocky river to a sailable lake.

Thanks

Well, both would not hurt. It is just as easy to run a 1x1 around the
case, inside the hull, and a strip of glass on the outside of the
hull, to protect the edges of the joint. Light, strong, watertight.
Scotty

Proper reinforcement of the centerboard trunk on the INSIDE would be
critical since you don't want the trunk to flex at all and there will be
quite a bit of pressure on the trunk when the board is down. I havn't
seen this design but I think fastening the top of the trunk to a thwart
or seat might be a good way to firm it up.
You might want to radius the edges of the plywood where the board enters
the slot to avoid chipping this edge. I'd coat with glass and tape.
Be sure to make the slot quite a bit wider than you think it needs to be
since the board will swell and you might jam stones up there and a
bigger space seems to keep things open easier. The pivot on the board
should be loose too. I've used an oversised hole with an oversized
nylon bushing that rode on a stub of galvanized pipe threaded on both
ends as the pivot before and it worked well. For a larger boat I'd use
a steel or phosphor bronze pin.

Andrew Butchart wrote:
I'm currently working on a Phil Bolger designed plywood sailing pirogue (the
CSD one). Even though the original design calls for a lee-board, I can't
leave well enough alone and am planning on an off-centre centre-board.

My question is about protecting the hull bottom at the centre board slot.
On previous boats (with a dagger-board), I just added some fibreglass tape
around and overlapping the slot, but I was wondering for this one if perhaps
some sort of shoe would be appropriate, and if so what (inexpensive and easy
to find) materials might be suitable. I'm intending on using this boat in
locations where I will have to paddle up a rocky river to a sailable lake.

Thanks

"steveJ" wrote in message
...
Proper reinforcement of the centerboard trunk on the INSIDE would be
critical since you don't want the trunk to flex at all and there will be
quite a bit of pressure on the trunk when the board is down. I havn't
seen this design but I think fastening the top of the trunk to a thwart
or seat might be a good way to firm it up.
You might want to radius the edges of the plywood where the board enters
the slot to avoid chipping this edge. I'd coat with glass and tape.
Be sure to make the slot quite a bit wider than you think it needs to be
since the board will swell and you might jam stones up there and a
bigger space seems to keep things open easier. The pivot on the board
should be loose too. I've used an oversised hole with an oversized
nylon bushing that rode on a stub of galvanized pipe threaded on both
ends as the pivot before and it worked well. For a larger boat I'd use
a steel or phosphor bronze pin.



Steve:

Thanks - an excellent suggestion on re-inforcing the trunk on the inside,
I'll also take your advice with putting a radius on the slot - now that I
got a router for Christmas :-) The top of the trunk will be covered by the
deck except for a small portion where the top of the board will pivot up.
I'll probably use a 3/8" bolt for a pivot which should be lots since this
boat is only 14' long.

--
Andrew Butchart

http://www.floatingbear.ca

Andrew Butchart wrote:
"steveJ" wrote in message
...

Proper reinforcement of the centerboard trunk on the INSIDE would be
critical since you don't want the trunk to flex at all and there will be
quite a bit of pressure on the trunk when the board is down. I havn't
seen this design but I think fastening the top of the trunk to a thwart
or seat might be a good way to firm it up.
You might want to radius the edges of the plywood where the board enters
the slot to avoid chipping this edge. I'd coat with glass and tape.
Be sure to make the slot quite a bit wider than you think it needs to be
since the board will swell and you might jam stones up there and a
bigger space seems to keep things open easier. The pivot on the board
should be loose too. I've used an oversised hole with an oversized
nylon bushing that rode on a stub of galvanized pipe threaded on both
ends as the pivot before and it worked well. For a larger boat I'd use
a steel or phosphor bronze pin.




Steve:

Thanks - an excellent suggestion on re-inforcing the trunk on the inside,
I'll also take your advice with putting a radius on the slot - now that I
got a router for Christmas :-) The top of the trunk will be covered by the
deck except for a small portion where the top of the board will pivot up.
I'll probably use a 3/8" bolt for a pivot which should be lots since this
boat is only 14' long.

For a pivoting board (ie. proper centreboard, not a daggerboard) most
sailing dinghy designs have a slot gasket. This consists of two strips
either side of the slot that cover it when the board is up and prevent
too much water slopping up the case when the board is partially or fully
down. In a chop, an ungasketed case can deliver water fast enough to
require continuous bailing.

The strips tend to be either fabric backed or reinforced rubber (thin
convayer belting? - rather obsolete) sailcloth (bit old fashioned but
reliable) or a Mylar laninate tape (the latest thing?). The rubber and
the Mylar you apply by fastening both sides the whole length of the slot
then slitting down the middle to give two equal flaps, the Sailcloth
strips are applied a little differently.

Take two strips of Dacron (polyester) sailcloth at least 1' longer than
your slot and 1" wider. Fold over to half their width, run a couple of
lines of stitching full length to hold them there and iron the crease
in. Punch one end of each and fit a cheap eyelet.
.. . . . .
Now I need to describe the rubbing strips used to protect the keel and
the edges of the slot that the gasket fastens under.
The rubbing strips are metal, of a rather flat D section (half round at
a pinch but usually thinner) typically 1/2" x 1/4" for a boat of the
size we have but can be as thin as 1/8". The metal is ideally bronze,
but brass or aluminium is fine for fresh water use and occasional salt
water use. If all you can get is flat strip, just round the corners on
one side with a file then finish with a sander, or even use as is.
It is bent to fit the keel and the edges of the centreboard case BEFORE
it is drilled and countersunk for the fixing screws every 2 - 3". The
screws should be the same metal apart from aluminium for which use 316
stainless. It should be well bedded on a non hardening mastic, and
will take most of the abrasion if you touch bottom and much of the worry
out of beaching your boat.
.. . . . .
Back to the slot gasket. Fasten the ends without the eyelet under the
metal strips either side of the slot a couple of inches infront of the
slot, overlapping the strips by about 1/4" down the folded edge. (the
metal strips should have already been fitted once so all the screw holes
are ready and correctly lined up.) Start with one screw each, angle the
cloth strips slightly so the overlap is NIL at the back of the slot,
put in the next screw each side, tighten and then use two lines to the
rudder pintle on the transom (or other convenient fitting) through the
eyelets to tension the strips. They will buckle slightly to form a
slight 'hump' at the front of the case. This provides enough slack to
ease round the front of the board when fully down. Fasten all the
screws in the metal strips working back from the bow maintaining an
overlap between 1/8 and 1/4" (hint, rule a line on the bottom gasket
strip FIRST). Finish by cutting the cloth strips short on the diagonal
JUST before the back of the slot leaving a small V for any water forced
into the case around the board to drain back out. Trim off any gross
excess down the outside edges of the keelband strips with a razor blade
or very sharp knife.

Protect the front and back ends of the slot either with metal plates
(same metal as keelband strips PLEASE) or 2 - 3" offcuts of keelband
parallel to and centered between the strips either side of the slot.
Chandlers here have special triangular plates available to transition
from 1 centreline keel band to the two strips either side of the slot,
but they arent strictly necercery and wouldnt fit an offset case.

The end result should be good for 5 - 10 years dependant on usage. The
metal strips are usually good for 20 - 40 years.

DONT skimp on the bedding compound or leave any screw heads proud. Any
screw heads that protrude slightly at the edge should be filed flush.
'dope' each screw hole with your favorite mix or just bedding compound.
Its important to avoid water penetrating the wood.

P.S. Let some spare keelband into the tip of your centerboard and about
6" up the leading edge and you wont cry the first time you touch bottom
with it. (Or wait and fix the damage by letting in a strip like I did
:-( ) Dress it to profile with a file after fastening it. Also worth
doing to the rudder if you have a pivot up rudder blade. If not, you
must *NEVER* let the rudder touch anyway so dont bother with metaling
the tip.
--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk [at]=@, [dash]=- &
[dot]=.
*Warning* SPAM TRAP set in header, Use email address in sig. if you must.
'Stingo' Albacore #1554 - 15' Uffa Fox designed, All varnished hot
moulded wooden racing dinghy circa. 1961

"Ian Malcolm" wrote in message
...
For a pivoting board (ie. proper centreboard, not a daggerboard) most
sailing dinghy designs have a slot gasket. This consists of two strips
either side of the slot that cover it when the board is up and prevent
too much water slopping up the case when the board is partially or fully
down. In a chop, an ungasketed case can deliver water fast enough to
require continuous bailing.
snip



More excellent advice - thanks.

--
Andrew Butchart

http://www.floatingbear.ca