Is 1/4 inch (6 mm) plywood, glassed over, adequate for a non
load-bearing, hard canopy for my little cruiser? The canopy will be
about 9ft long by 6ft wide, and slightly curved for water run-off and
aesthetics. How many layers of fibreglass cloth would be needed?

I intend to force the plywood into shape and allow the epoxy and
fibreglass to keep its shape when dry.

I'm trying to avoid rafters as they eat into the avilable height.

teddyareno wrote:
Is 1/4 inch (6 mm) plywood, glassed over, adequate for a non
load-bearing, hard canopy for my little cruiser? The canopy will be
about 9ft long by 6ft wide, and slightly curved for water run-off and
aesthetics. How many layers of fibreglass cloth would be needed?

I intend to force the plywood into shape and allow the epoxy and
fibreglass to keep its shape when dry.

I'm trying to avoid rafters as they eat into the avilable height.

No probably not Teddy @ 9'X6', unless you put some curved shaped
framing under it. If you don't the flexing will just break the bond
between the glass & ply.

The cheapest lightest will be some framing & the glassed over ply.

You might consider coating the ply with release agent (PVA) then you
can build a good thickness of glass, peal the ply away & not have the
ply at all???

2 X 1 1/2 oz chopped strand mat should be plenty to add some strength &
when flow or gel coated it should be water proof.




K

Been busy today so I'll keep the Krause lie of the day short.

This lying simpleton, after it became clear he was losing a thread
where he was displaying his usual lack of patriotism much less gratitude
for the brave men & women out there risking their everything, to keep
the likes of him safe, he just reverts to type.

But seriously can you imagine this uneducated union thug now claims
he is reviewing universities!!! & wait for it he poo poos the
engineering course!!! this from a lying uneducated union thug who
couldn't use a toaster without a union authorised electrician in attendance.

I've included just one of the followup responses but it was such a
bald faced lie it even embarrassed the rejoinders:-)


I have visited West Point, the Naval Academy, the Air Force Academy and
the sub training facility at Groton. Some years ago, I actually did look
over descriptions of some of the course material at Annapolis and the
c.v.'s of some of the faculty. I'm sure the engineering course material
is fairly rigorous, though it is more "trade-oriented" and did not look
up to MIT or CalTech standards. I mean, if your goal is to be an
aeronautical engineer, you're going to get better training at MIT or
CalTech or at any of a large number of other engineering schools. I
thought the faculty academic credentials no better than what is found at
a typical smaller four year public university. The military academies
turn out military officers with an education, not highly educated
military officers. But that is their purpose, eh?



--


Holy molly, grandma, put on your high boots.


Harry Krause, admitted graduate in the humanities with a degree in
English
is hereby qualified to critique the engineering curriculum of not
only West
Point, but also that of the Naval Academy and the Air Force Academy and
compare it to that of MIT and CalTech.


The above paragraph is a classic.


You missed your calling Harry.

On 2 Feb 2005 23:34:21 -0800, (teddyareno)
wrote:
Is 1/4 inch (6 mm) plywood, glassed over, adequate for a non
load-bearing, hard canopy for my little cruiser? The canopy will be
about 9ft long by 6ft wide, and slightly curved for water run-off and
aesthetics. How many layers of fibreglass cloth would be needed?

I intend to force the plywood into shape and allow the epoxy and
fibreglass to keep its shape when dry.

I'm trying to avoid rafters as they eat into the avilable height.
=================================================

I would suggest reposting your question on group 'rec.boats.building'.

There are a number of people on that group who fabricate fiberglass
parts of various sorts. I agree with K that you are not going to get
the kind of panel stiffness you want with 1/4 inch ply unless you
glass it very heavily, but there are other alternatives such as 3/4
inch foam that might work out with the proper fiberglass layup on each
side. I disagree with K regarding the use of Chopped Strand Mat as a
reinforcing material. CSM is very weak for its weight and is mostly
useful for adding non-structural thickness to a layup. Woven glass
cloth or unidirectional has much better stiffness and structural
qualities.

Wayne.B wrote:

On 2 Feb 2005 23:34:21 -0800, (teddyareno)
wrote:

Is 1/4 inch (6 mm) plywood, glassed over, adequate for a non
load-bearing, hard canopy for my little cruiser? The canopy will be
about 9ft long by 6ft wide, and slightly curved for water run-off and
aesthetics. How many layers of fibreglass cloth would be needed?

I intend to force the plywood into shape and allow the epoxy and
fibreglass to keep its shape when dry.

I'm trying to avoid rafters as they eat into the avilable height.

=================================================

I would suggest reposting your question on group 'rec.boats.building'.

There are a number of people on that group who fabricate fiberglass
parts of various sorts. I agree with K that you are not going to get
the kind of panel stiffness you want with 1/4 inch ply unless you
glass it very heavily, but there are other alternatives such as 3/4
inch foam that might work out with the proper fiberglass layup on each
side. I disagree with K regarding the use of Chopped Strand Mat as a
reinforcing material. CSM is very weak for its weight and is mostly
useful for adding non-structural thickness to a layup. Woven glass
cloth or unidirectional has much better stiffness and structural
qualities.

Well my hull is basically 1/4" ply and is PLENTY stiff. Mind you, the
maximum unsupported area is about 1/4 of yours with a lot of curvature
molded in by Fairey marine when they hot pressed the veneers my hull is
made of. If you epoxy glass a couple of lairs of cloth on each side of
a pre curved ply core of sufficient thickness WITH PLENTY OF
CURVATURE it should be stiff enough to stand on with a 6 foot span. You
*DONT* want to lock in the strain by glassing ply that wont hold its
shape without the glass.
Check out http://www.marineply.com/stagflex.htm
You need a really good bond though, and I wouldn't try it unless I had
the equipment to vacuum bag the laminate.
--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
[at]=@, [dash]=- & [dot]=. *Warning* HTML & 32K emails -- NUL:
'Stingo' Albacore #1554 - 15' Early 60's, Uffa Fox designed,
All varnished hot moulded wooden racing dinghy.

Thanks to K and Wayne.B for helpful advice

Wayne.B wrote in message . ..
On 2 Feb 2005 23:34:21 -0800, (teddyareno)
wrote:
Is 1/4 inch (6 mm) plywood, glassed over, adequate for a non
load-bearing, hard canopy for my little cruiser? The canopy will be
about 9ft long by 6ft wide, and slightly curved for water run-off and
aesthetics. How many layers of fibreglass cloth would be needed?

I intend to force the plywood into shape and allow the epoxy and
fibreglass to keep its shape when dry.

I'm trying to avoid rafters as they eat into the avilable height.
=================================================

I would suggest reposting your question on group 'rec.boats.building'.

There are a number of people on that group who fabricate fiberglass
parts of various sorts. I agree with K that you are not going to get
the kind of panel stiffness you want with 1/4 inch ply unless you
glass it very heavily, but there are other alternatives such as 3/4
inch foam that might work out with the proper fiberglass layup on each
side. I disagree with K regarding the use of Chopped Strand Mat as a
reinforcing material. CSM is very weak for its weight and is mostly
useful for adding non-structural thickness to a layup. Woven glass
cloth or unidirectional has much better stiffness and structural
qualities.

On 2 Feb 2005 23:34:21 -0800, (teddyareno)
wrote:

Is 1/4 inch (6 mm) plywood, glassed over, adequate for a non
load-bearing, hard canopy for my little cruiser? The canopy will be
about 9ft long by 6ft wide, and slightly curved for water run-off and
aesthetics. How many layers of fibreglass cloth would be needed?

It should be fine. I did consulting work for UL in the late sixties
while married to my third wife, who was the CEO for Anderson lumber
international at the time.

Harry Krause wrote in message . ..
On 2 Feb 2005 23:34:21 -0800, (teddyareno)
wrote:

Is 1/4 inch (6 mm) plywood, glassed over, adequate for a non
load-bearing, hard canopy for my little cruiser? The canopy will be
about 9ft long by 6ft wide, and slightly curved for water run-off and
aesthetics. How many layers of fibreglass cloth would be needed?

It should be fine. I did consulting work for UL in the late sixties
while married to my third wife, who was the CEO for Anderson lumber
international at the time.

Thanks again everyone. Harry, I hope you stuck it out with your third
wife --- a wife and lumber yard all in one package. Heaven.