Strip Planking Hull Thickness
 

Hello all,

Can anyone assist me with the calculation for strip planking hull
thickness...? We are embarking on a build of a 40ft ketch.

I know there is Dave Gerr's formulae for determining this but have not
got his book (not available in SA). I intend exoxy glass in/out.

Also, what influence will a different wood species make on the thickness
required? ie: mahogany vss cedar vss ... vss ...

Thanks for the info - cheers,
Max

Strip Planking Hull Thickness
 

Goo'day, Max

On Thu, 26 Oct 2006 08:23:22 +0200, Max Hazelhurst
wrote:

Hello all,

Can anyone assist me with the calculation for strip planking hull
thickness...?

Very briefly, the result of the calculation is whatever the designer
specifies.

No designer? You're the designer? Oh dear..... Might I suggest you
start your career with a slightly less ambitious project? About 30'
less....

Regards,

Bruce Nichol
ALBURY NSW Australia

Strip Planking Hull Thickness
 

Max Hazelhurst wrote:

Can anyone assist me with the calculation for strip planking hull
thickness...? We are embarking on a build of a 40ft ketch.

Sounds like a large project to begin with.

I know there is Dave Gerr's formulae for determining this but have not
got his book (not available in SA). I intend exoxy glass in/out.

Well, do get that book. It is available from on-line dealers that ship
around the world. Gerr does give neat and simple formulas, but there too
many factors to cover in a newsgroup post. Get that book! I think
Herreshoff also published his scantling rules, but watch out, those were
lighter, and assumed more qualified woodworking. Chapelle might have
published scantling rules too, I don't remember. Larsson's and
Eliasson's "Principles of Yacht Design" is a good modenr work that will
tell you a lot.

I know getting these books takes time and trouble. Reading and understanding
even more so. I bet that time more than pays itself when you finally start
building. And if you get your boat to sail, you sleep much better if you
*know* that the construction is solid enough for your waters.

If you are asking that kind of questions, I recommend a year of reading, and
then a year or three of designing, before you start to chop wood... When
you get to the concrete questions, ask again. I'm sure this group can help
with many details.

Good luck with the project!

- Heikki
(already at the design stage, for a 24' schooner)

Strip Planking Hull Thickness
 

Hi all,

cool - thanks for the heads-up thusfar. I'll organize the book via the
UK and take it from there.

I have spec's to work against for the plans that I am working off -
being the inquisitive sort, I want to understand the dynamics behind
this and also investigate some alternative species that I may have
access to here in S.Africa.

I'll post my findings here for reference and comment.

Thanks,
M

Strip Planking Hull Thickness
 

It depends on the type of wood and the layup schedule of the glass. It
really needs to be vary carefully analyzed and balanced.

On my 45' hull the designer called for 1.125" thick by 1.75" wide white
cedar with 4 layers of unidirectional diagonally laid below the waterline
and 2 layers above with 2 layers on the inside plus some Kevlar in the
forward slamming areas.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"Max Hazelhurst" wrote in message
...
Hello all,

Can anyone assist me with the calculation for strip planking hull
thickness...? We are embarking on a build of a 40ft ketch.

I know there is Dave Gerr's formulae for determining this but have not got
his book (not available in SA). I intend exoxy glass in/out.

Also, what influence will a different wood species make on the thickness
required? ie: mahogany vss cedar vss ... vss ...

Thanks for the info - cheers,
Max

Strip Planking Hull Thickness
 

Hi Glenn,

Thanks - I've looked quite a bit at your site in the past so, appreciate
the work that I'm throwing myself into...

Thanks for the info - I'll get the specifications hopefully quite soon
from the designers and post for comment and possible concerns.

Thanks
Max

Strip Planking Hull Thickness
 

Max,

I am also building a 40ft. ketch. It's not intended to be 'light'
displacement, and has a D/L ration of 230. It is intended to be
structurally perhaps a bit lighter than the traditional construction
plans I started with. For strip-plank with no ribs, except at
bulkheads, Bill Garden advised 1 3/8" strips. For the same with no
ribs (except bulkheads) and sheathed in and out with 30 oz. glass, Tom
MacNaughton advised 1 inch. I suggest you get "Sheathed Strip
Construction Scantlings Rule" from MacNaughton Associates, Inc.,
Eastport Boat Yard and Supply, Box 190, Eastport, Maine 04631, USA. I
hope that address is still good. I bought the rule about 10 yrs. ago.
At that time his phone was 207-853-6049. He has a rule that easily
sets up in a spreadsheet and is based on displacement. It's designed
to build boats at least as strong as per Nevin's rule, and often
lighter.

Remember that with strip planking you need something to add cross-grain
strength. That can either be ribs or sheathing. I compromised. My
hull has several bulkheads, each with a rib. It has one rib between
each pair of bulkheads so it's not fully ribbed. It has MacNaughton's
30 oz. exterior sheathing but only 10 oz. interior, figuring I'd get
the extra strength from the ribs I have, and allows me to finish the
interior bright. I planked with 1 7/16" square strips. My planking
thickness, after fairing, is probably 1 3/8" max, less in some areas
depending on how much fairing was needed.

Max Hazelhurst wrote:
Hello all,

Can anyone assist me with the calculation for strip planking hull
thickness...? We are embarking on a build of a 40ft ketch.
Max

Strip Planking Hull Thickness
 

Hi there,

Awesome - that's really helpful - I found Tom's website and have emailed
him about the scantlings rule book. Do you have any photo's of your
build - especially the ribs/bulkhead/inner hull areas? You can email me
off-list: maxh ..@.. zelhurst...com

Thanks,
Max
Max,

I am also building a 40ft. ketch. It's not intended to be 'light'
displacement, and has a D/L ration of 230. It is intended to be
structurally perhaps a bit lighter than the traditional construction
plans I started with. For strip-plank with no ribs, except at
bulkheads, Bill Garden advised 1 3/8" strips. For the same with no
ribs (except bulkheads) and sheathed in and out with 30 oz. glass, Tom
MacNaughton advised 1 inch. I suggest you get "Sheathed Strip
Construction Scantlings Rule" from MacNaughton Associates, Inc.,
Eastport Boat Yard and Supply, Box 190, Eastport, Maine 04631, USA. I
hope that address is still good. I bought the rule about 10 yrs. ago.
At that time his phone was 207-853-6049. He has a rule that easily
sets up in a spreadsheet and is based on displacement. It's designed
to build boats at least as strong as per Nevin's rule, and often
lighter.

Remember that with strip planking you need something to add cross-grain
strength. That can either be ribs or sheathing. I compromised. My
hull has several bulkheads, each with a rib. It has one rib between
each pair of bulkheads so it's not fully ribbed. It has MacNaughton's
30 oz. exterior sheathing but only 10 oz. interior, figuring I'd get
the extra strength from the ribs I have, and allows me to finish the
interior bright. I planked with 1 7/16" square strips. My planking
thickness, after fairing, is probably 1 3/8" max, less in some areas
depending on how much fairing was needed.

Max Hazelhurst wrote:
Hello all,

Can anyone assist me with the calculation for strip planking hull
thickness...? We are embarking on a build of a 40ft ketch.
Max

Strip Planking Hull Thickness
 

On Thu, 26 Oct 2006 08:23:22 +0200, Max Hazelhurst
wrote:

Also, what influence will a different wood species make on the thickness
required? ie: mahogany vss cedar vss ... vss ...

Mahogany would not be my first choice since it is much less rot
resistant than cedar as I understand it.

Strip Planking Hull Thickness
 

Mahogany is also a lot heavier than cedar and not as tolerant to bending.
Strip composite uses the strips as a core and its strength depends on the
core maintaining its shear strength. Cedar can absorb more deflection from
pounding.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"Wayne.B" wrote in message
...
On Thu, 26 Oct 2006 08:23:22 +0200, Max Hazelhurst
wrote:

Also, what influence will a different wood species make on the thickness
required? ie: mahogany vss cedar vss ... vss ...

Mahogany would not be my first choice since it is much less rot
resistant than cedar as I understand it.