Re: Options for ply thickness for similar sharpie construction on simila [3 Attachments]

I heard the question to be "Why the variation in scantlings for a bunch of basically similar boats?"

Maybe Susan will choose offer something more definitive. My guess is that it has some to do with what the original commissioner said regarding the use of the particular design. Some were definitely for smaller lakes, protected waters, and others for coastal ocean cruising. Some would be trailered regularly, others pulled occasionally and cradled in a marina. Some were PCB's 'stock' plan from his own initiative, others per customer requirements.

Lastly, I think it is likely there are decades between the earliest and latest of the designs named. So PCB's decisions evolved, or at least changed, during that time.

oooooh MY! there's a phrase in the wonderfully-written reply below, that should become a classic on this website, oft-repeated (as it applies to a LOT of discussions):

"...It was not the dead pigs fault.."

timeless!

brilliant, Chief!

Wayne Gilham

From:bolger@yahoogroups.com [mailto:bolger@yahoogroups.com]On Behalf OfChief Redelk
Sent:Monday, December 23, 2013 8:44 PM
To:bolger@yahoogroups.com
Subject:Re: [bolger] Options for ply thickness for similar sharpie construction on simila

Agreed Bill.. My canoe fits that bill as well.

My point is that building light is most important in boats NOT on a
trailer.. That would be car top boats. Yes they would need to be
light..

My future boats will all be trailered since I am getting older and not
able to handle a 70 lb boat like I once could.

Therefore my future boats can be made out of 3/8 plywood and due to my
building skills will not a lot heavier than 1/4 ext plywood.

I know because we have a small scow made out of 3/8 plywood and one
made out of Luan. The thicker plywood was gifted to us so we used it
and was shocked how light the boat came out.

The boat is not all that heavy because the plywood did not require as
much bracing as the thin Luan boats and my skills as a builder..

The point is.. If the boat will be on a trailer it can be made a
little bit stronger and heavier.

Also a sailboat has a middle of the road weight range. It can be made
to light for some conditions.

It can be made to heavy for some conditions... My heavy PDR has enough
weight to carry it through a "Come about" while my light Baby Goose
has to be spun on the lee board by my weight being moved forward.

Weight is like ladies. While they can be a bit over weight they can be
a bit under weight..

My point being. I like good 3/8 plywood for boats on trailers. IF
someone goops a LOT of epoxy and glass on it the thing becomes a
"Tank".. If it's made light it can be excellent.

Boat building is like cooking. I know someone who messed up a good
ham..It was not the dead pigs fault..

I do agree that light boats ares great if you need to carry the boat
or self launch without a trailer.

For doing that I know of a man who uses 1/16th door skins and foam..
Great boats uses epoxy for his builds. It's not as cheap to build as
what I do but great boat.

Skin on frame is another good way to build light. But floating in
gators, snags, roots under water junk, I want 3/8 plywood..

Building boats is like choosing a woman.. We all think OURS is the
best. Smile, good day..Chief..

On 12/23/13, Bill Howard <billh39@...> wrote:
> The key is weight vs. strength.
>
> My 14 foot June Bug would be impossible to car-top with 3/8 inch ply.
>
> It would also be foolhardy to take her into any kind of chop.
>
> Here she is returning from a jaunt in the Chesapeake. Wind about 5 knots.
>
> Bill Howard,
> Nellysford
>
>
>
> On Dec 23, 2013, at 5:40 PM, Chief Redelk <chiefredelk@...> wrote:
>
>> I made that discovery on small boats too..
>>
>> I am of the opinion that 3/8 plywood is MUCH stiffer than 1/4,
>> stronger and not a lot heavier..
>>
>> I find a full 3/8 plywood deck well supported works well..When I
>> design a deck that will be walked on I think of picture frames or 4
>> sides boxes 12 inches wide by 12 inches long by 3 inches deep..Bracing
>> like that well supported then covered with 3/8 ply is very strong..I
>> think that a brace every 12 inches is my standard.. Ribs once were set
>> that close but on some boats I open them up to 16 inches.. However,
>> Stitch and glue boats don't fit that rule..
>>
>> My next boat will have a 3/8 plywood bottom, 3/8 decks and maybe 3/8
>> all over.. BUT since it's gonna be a 12 feet long scow maybe I will
>> make the sides out of 1/4 ext ply...BUT the fact is I am not sure the
>> weight difference is worth all the trouble of using two thicknesses of
>> plywood..
>>
>> In my mind there are TWO boat options when it comes to materials.. ONE
>> for boats on trailers and the other ONE for boats designed to be
>> LIGHT.. Since I trailer all my boats, just a tad Heavier is not a
>> problem..
>>
>> I am not talking excessively Heavy boats or over built boats.. just
>> boats using 3/8 versus 1/4 plywood..1 inch by 1 inch bracing is good
>> IF it's not hanging in the air..Well braced boats need to be
>> overweight.. Good day, Chief..
>>
>> On 12/23/13, MylesJ. Swift <mswift@...> wrote:
>> > I ended up doubling the ¼ inch bottom and main deck on my Micro. With
>> > four
>> > 200pounds plus guys dancing on the deck it flexed too much for my
>> > comfort.
>> >
>> >
>> >
>> > MylesJ
>> >
>> >
>>
>>
>
>

If you assume that ¼” and 3/8’” plywood have equal densities, 3/8” weighs 50% more than ¼”. If you assume a straight substitution of 3/8” for ¼” (with no change in framing), then a hull made if 3/8” will weigh 50% more than an identical hull made of ¼”.

There are a variety of ways to address boat weight, strength, and stiffness. Decks which are not intended to support people (such as those on kayaks) can be very thin (and some of these are made of fabric). However, very thin bottoms don’t work very well due to flexibility and lack of durability. The trick is to use thicker stuff where you need it and thinner stuff elsewhere.

Another approach is to support relatively thin skins with closely spaced framing. Some examples, such as skin on frame boats are obvious. Others, such as the stringers on cold molded boats, the laps on lapstrake boats, or even the fillets on stitch and glue boats are somewhat less obvious. Another possibility is to box in the space between longitudinal thwarts and the bottom of the boat, creating box girders for torsional stiffness and for adding a longitudinal frame on the bottom.

Finally, it is possible to add strength and stiffness to a hull by adding a layer of fiberglass on the outside of the boat. Many strip build boats add a layer of fiberglass on the inside and outside of the boat creating a wood cored fiberglass boat. This can create a very light, strong, and stiff boat.

All boats are compromises and one of the areas of compromise is scantlings. Many stitch and glue boats were designed on the premise that they would be built out of readily available, construction grade material and ¼” works pretty well for most small boats. But without constraints dictated by the need to market boat plans, it is likely that many small boats would have heavier bottoms and thinner sides.

JohnT

From:bolger@yahoogroups.com [mailto: bolger@yahoogroups.com ]On Behalf OfChief Redelk
Sent:Monday, December 23, 2013 5:40 PM
To:bolger@yahoogroups.com
Subject:Re: [bolger] Re: Options for ply thickness for similar sharpie construction on simila

I made that discovery on small boats too..

I am of the opinion that 3/8 plywood is MUCH stiffer than 1/4,
stronger and not a lot heavier..

I find a full 3/8 plywood deck well supported works well..When I
design a deck that will be walked on I think of picture frames or 4
sides boxes 12 inches wide by 12 inches long by 3 inches deep..Bracing
like that well supported then covered with 3/8 ply is very strong..I
think that a brace every 12 inches is my standard.. Ribs once were set
that close but on some boats I open them up to 16 inches.. However,
Stitch and glue boats don't fit that rule..

My next boat will have a 3/8 plywood bottom, 3/8 decks and maybe 3/8
all over.. BUT since it's gonna be a 12 feet long scow maybe I will
make the sides out of 1/4 ext ply...BUT the fact is I am not sure the
weight difference is worth all the trouble of using two thicknesses of
plywood..

In my mind there are TWO boat options when it comes to materials.. ONE
for boats on trailers and the other ONE for boats designed to be
LIGHT.. Since I trailer all my boats, just a tad Heavier is not a
problem..

I am not talking excessively Heavy boats or over built boats.. just
boats using 3/8 versus 1/4 plywood..1 inch by 1 inch bracing is good
IF it's not hanging in the air..Well braced boats need to be
overweight.. Good day, Chief..

On 12/23/13, MylesJ. Swift <mswift@...> wrote:
> I ended up doubling the ¼ inch bottom and main deck on my Micro. With four
> 200pounds plus guys dancing on the deck it flexed too much for my comfort.
>
>
>
> MylesJ
>
>

Agreed Bill.. My canoe fits that bill as well.

My point is that building light is most important in boats NOT on a
trailer.. That would be car top boats. Yes they would need to be
light..

My future boats will all be trailered since I am getting older and not
able to handle a 70 lb boat like I once could.

Therefore my future boats can be made out of 3/8 plywood and due to my
building skills will not a lot heavier than 1/4 ext plywood.

I know because we have a small scow made out of 3/8 plywood and one
made out of Luan. The thicker plywood was gifted to us so we used it
and was shocked how light the boat came out.

The boat is not all that heavy because the plywood did not require as
much bracing as the thin Luan boats and my skills as a builder..

The point is.. If the boat will be on a trailer it can be made a
little bit stronger and heavier.

Also a sailboat has a middle of the road weight range. It can be made
to light for some conditions.

It can be made to heavy for some conditions... My heavy PDR has enough
weight to carry it through a "Come about" while my light Baby Goose
has to be spun on the lee board by my weight being moved forward.

Weight is like ladies. While they can be a bit over weight they can be
a bit under weight..

My point being. I like good 3/8 plywood for boats on trailers. IF
someone goops a LOT of epoxy and glass on it the thing becomes a
"Tank".. If it's made light it can be excellent.

Boat building is like cooking. I know someone who messed up a good
ham.. It was not the dead pigs fault..

I do agree that light boats ares great if you need to carry the boat
or self launch without a trailer.

For doing that I know of a man who uses 1/16th door skins and foam..
Great boats uses epoxy for his builds. It's not as cheap to build as
what I do but great boat.

Skin on frame is another good way to build light. But floating in
gators, snags, roots under water junk, I want 3/8 plywood..

Building boats is like choosing a woman.. We all think OURS is the
best. Smile, good day..Chief..

On 12/23/13, Bill Howard <billh39@...> wrote:
> The key is weight vs. strength.
>
> My 14 foot June Bug would be impossible to car-top with 3/8 inch ply.
>
> It would also be foolhardy to take her into any kind of chop.
>
> Here she is returning from a jaunt in the Chesapeake. Wind about 5 knots.
>
> Bill Howard,
> Nellysford
>
>
>
> On Dec 23, 2013, at 5:40 PM, Chief Redelk <chiefredelk@...> wrote:
>
>> I made that discovery on small boats too..
>>
>> I am of the opinion that 3/8 plywood is MUCH stiffer than 1/4,
>> stronger and not a lot heavier..
>>
>> I find a full 3/8 plywood deck well supported works well..When I
>> design a deck that will be walked on I think of picture frames or 4
>> sides boxes 12 inches wide by 12 inches long by 3 inches deep..Bracing
>> like that well supported then covered with 3/8 ply is very strong..I
>> think that a brace every 12 inches is my standard.. Ribs once were set
>> that close but on some boats I open them up to 16 inches.. However,
>> Stitch and glue boats don't fit that rule..
>>
>> My next boat will have a 3/8 plywood bottom, 3/8 decks and maybe 3/8
>> all over.. BUT since it's gonna be a 12 feet long scow maybe I will
>> make the sides out of 1/4 ext ply...BUT the fact is I am not sure the
>> weight difference is worth all the trouble of using two thicknesses of
>> plywood..
>>
>> In my mind there are TWO boat options when it comes to materials.. ONE
>> for boats on trailers and the other ONE for boats designed to be
>> LIGHT.. Since I trailer all my boats, just a tad Heavier is not a
>> problem..
>>
>> I am not talking excessively Heavy boats or over built boats.. just
>> boats using 3/8 versus 1/4 plywood..1 inch by 1 inch bracing is good
>> IF it's not hanging in the air..Well braced boats need to be
>> overweight.. Good day, Chief..
>>
>> On 12/23/13, MylesJ. Swift <mswift@...> wrote:
>> > I ended up doubling the ¼ inch bottom and main deck on my Micro. With
>> > four
>> > 200pounds plus guys dancing on the deck it flexed too much for my
>> > comfort.
>> >
>> >
>> >
>> > MylesJ
>> >
>> >
>>
>>
>
>

The key is weight vs. strength.

My 14 foot June Bug would be impossible to car-top with 3/8 inch ply.

It would also be foolhardy to take her into any kind of chop.

Here she is returning from a jaunt in the Chesapeake. Wind about 5 knots.

Bill Howard,

Nellysford

On 12/23/13, MylesJ. Swift <mswift@...> wrote:
> I ended up doubling the ¼ inch bottom and main deck on my Micro. With four
> 200pounds plus guys dancing on the deck it flexed too much for my comfort.
>
>
>
> MylesJ
>
>

Ghosh they are heavy people. I wouldn't have them on my boat! 800 lbs plus you? Where was the waterline?

I ended up doubling the ¼ inch bottom and main deck on my Micro. With four 200pounds plus guys dancing on the deck it flexed too much for my comfort.

MylesJ