## Re: Illinois Isometrics

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• I think it may be in cartoons, the files section, LARGE Bolger boats but I m not sure and I find the Yahoo system lack of searchability frustrating. I ve got
Message 1 of 24 , May 8, 2009
I think it may be in cartoons, the files section, LARGE Bolger boats but I'm not sure and I find the Yahoo system lack of searchability frustrating.

I've got it on my computer if it is needed again.

Don

--- In bolger@yahoogroups.com, Harry James <welshman@...> wrote:
>
> Where in the files is the MAIB article on the Illinois, I put it there
> and can't find it.
>
> HJ
• I checked the buckling of a steel - core - steel sandwich due to temperature differences on the two surfaces. Assuming: - max. temperature difference of 30 K,
Message 2 of 24 , May 9, 2009
I checked the buckling of a steel - core - steel sandwich due to temperature differences on the two surfaces.

Assuming:
- max. temperature difference of 30 K,
e.g. when the sun shines onto a side.
Means: the panel would buckle outward.
- only one axis; the panel is 1 m wide

Result:
The outside skin would get about 0.36 mm longer for those 30 K.

Case 1: The edges of the outside skin are fixed at 1 m distance,
e.g. by a strong frame.
Result: The outside skin tries to create an arc of about 11.6 mm height (!!).
That is quite much. The core will surely not allow that. Means: if the inside skin stays flat (e.g. due to fixation to frames), most likely the core would fail by getting torn apart.

Case 2: The edges of the outside skin are not fixed, but the skin is allowed to expand and the inside skin is allowed to bend a bit.
The core is 2.5 cm thick (one inch).
Result a): If the core is very stiff against sheer forces (i.e. the outer side of the core doesn't allow this 0.36 mm expansion over 1 m width with a fixed inside length), then the result is an arc of the whole sandwich with only about 1.8 mm height. If the core thickness is doubled, the height of the arc gets half.
Result b): If the core is flexible enough to get streched on one surface similar to steel, while the other surface stays at constant length (easier with thicker core), then the panel would stay flat.

Conclusions ("Lessons Learnt"):
If my math is correct ... and my English understandable ;)

1) It is ok to fix the edges of the inner (cool side) skin of the panel to a frame that doesn't expand.
2) The edges of the outer (heatable) skin should be mounted only in such a way that small expansions (say 0.4 mm per m for both sides combined) are permissible, e.g. by using no bolts, screws, epoxy, but only silicone glue.
3) This in turn means that only the inside skin of the panel can bear compression or pulling forces.
4) Thicker core creates less problems, both in Case 2a) and 2b).
5) If possible avoid large temperature differences, e.g. by a thin layer of wood at the "sunny side".

But I am still unsure about the dimensions, e.g. what steel thickness would be needed on the outside of the sandwich to withstand common puncture situations, i.e. forces/pressures....

Cheers,
Stefan

--- In bolger@yahoogroups.com, I wrote:
> Regarding temperature:

> If there is a temperature difference between inside and outside,
> i.e. the inside and outside skins would expand at a different rate,
> the panel would bend as a consequence.
> In an low-angle circle segment (i.e. a flat arc), even low changes
> in length result in significant changes in radius.
> (to illustrate this: put a sheet of paper on the table
> and move the edges just a mm together and see how much
> the middle buckles upwards).
>
> I'll check how much that would be with temperatures
> that we encounter here.
>
> Cheers,
> Stefan
• ... This likely one of, but not all of, the reasons for wire mesh in a ferro cement boat. If there is an expansion difference the mesh can absorb it likely.
Message 3 of 24 , May 9, 2009
Stefan Probst wrote:
>
>
> I checked the buckling of a steel - core - steel sandwich due to
> temperature differences on the two surfaces.
>
> Assuming:
> - max. temperature difference of 30 K,
> e.g. when the sun shines onto a side.
> Means: the panel would buckle outward.
> - only one axis; the panel is 1 m wide
>
> Result:
> The outside skin would get about 0.36 mm longer for those 30 K.
>
> Case 1: The edges of the outside skin are fixed at 1 m distance,
> e.g. by a strong frame.
> Result: The outside skin tries to create an arc of about 11.6 mm
> height (!!).
> That is quite much. The core will surely not allow that. Means: if the
> inside skin stays flat (e.g. due to fixation to frames), most likely
> the core would fail by getting torn apart.
>
> Case 2: The edges of the outside skin are not fixed, but the skin is
> allowed to expand and the inside skin is allowed to bend a bit.
> The core is 2.5 cm thick (one inch).
> Result a): If the core is very stiff against sheer forces (i.e. the
> outer side of the core doesn't allow this 0.36 mm expansion over 1 m
> width with a fixed inside length), then the result is an arc of the
> whole sandwich with only about 1.8 mm height. If the core thickness is
> doubled, the height of the arc gets half.
> Result b): If the core is flexible enough to get streched on one
> surface similar to steel, while the other surface stays at constant
> length (easier with thicker core), then the panel would stay flat.
>
> Conclusions ("Lessons Learnt"):
> If my math is correct ... and my English understandable ;)
>
> 1) It is ok to fix the edges of the inner (cool side) skin of the
> panel to a frame that doesn't expand.
> 2) The edges of the outer (heatable) skin should be mounted only in
> such a way that small expansions (say 0.4 mm per m for both sides
> combined) are permissible, e.g. by using no bolts, screws, epoxy, but
> only silicone glue.
> 3) This in turn means that only the inside skin of the panel can bear
> compression or pulling forces.
> 4) Thicker core creates less problems, both in Case 2a) and 2b).
> 5) If possible avoid large temperature differences, e.g. by a thin
> layer of wood at the "sunny side".
>
> So far about construction details.
>
> But I am still unsure about the dimensions, e.g. what steel thickness
> would be needed on the outside of the sandwich to withstand common
> puncture situations, i.e. forces/pressures....
>
>
> Cheers,
> Stefan
>
> --- In bolger@yahoogroups.com <mailto:bolger%40yahoogroups.com>, I wrote:
> > Regarding temperature:
>
> > If there is a temperature difference between inside and outside,
> > i.e. the inside and outside skins would expand at a different rate,
> > the panel would bend as a consequence.
> > In an low-angle circle segment (i.e. a flat arc), even low changes
> > in length result in significant changes in radius.
> > (to illustrate this: put a sheet of paper on the table
> > and move the edges just a mm together and see how much
> > the middle buckles upwards).
> >
> > I'll check how much that would be with temperatures
> > that we encounter here.
> >
> > Cheers,
> > Stefan
>
>
This likely one of, but not all of, the reasons for wire mesh in a ferro
cement boat. If there is an expansion difference the mesh can absorb
it likely. I heard someone say a ferro cement boat is a steel boat
coated in cement.
Doug
• I am looking for my next boat(s) to build. I would like a super sexy looking sail boat, you know, jaw dropping lines, timeless style, classic, lots of
Message 4 of 24 , May 13, 2009
I am looking for my next boat(s) to build. I would like a super sexy looking sail boat, you know, jaw dropping lines, timeless style, classic, lots of brightwork.

I also have a 40 hp short shaft motor I want to build a long and lean hull for. Fishing only, built around a toilet for my lady. I have some ideas of my own and want to fold up some 9mm for the power project.

Any ideas for the sail version that won't take years? I build fast but loose interest faster. Ohh, it must deal with the ocean.

Thanks

Bruce in NJ

[Non-text portions of this message have been removed]
• Hi Bruce, ... You might look in the cartoon or study plan groups files sections for ideas. Search Yahoo groups for bolger and you should find these groups.
Message 5 of 24 , May 14, 2009
Hi Bruce,

> I am looking for my next boat(s) to build. I would like a super sexy looking sail boat, you know, jaw dropping lines, timeless style, classic, lots of brightwork.
>
> I also have a 40 hp short shaft motor I want to build a long and lean hull for. Fishing only, built around a toilet for my lady. I have some ideas of my own and want to fold up some 9mm for the power project.
>
> Any ideas for the sail version that won't take years? I build fast but loose interest faster. Ohh, it must deal with the ocean.

You might look in the cartoon or study plan groups' files sections for ideas. Search Yahoo groups for "bolger" and you should find these groups.

For the sailboat, take a look at Summer Ease (also incorrectly called Summer Breeze in some places). Bolger told me none had been built, and I have been sorely tempted to build this one.

For the powerboat, look at the Fisherman's Launch in Bolger's book Boats With An Open Mind. It could be built in lapstrake plywood. You could also rig a toilet on Slicer (in the same book), but I'm not sure if it's considered an ocean-going dayboat or not.

Jon Kolb
• Thanks, will have a look. I want to get started on this, I m a fast builder, but it takes me forever to pick something. I see sailboats I love, like the one in
Message 6 of 24 , May 14, 2009
Thanks, will have a look. I want to get started on this, I'm a fast builder, but it takes me forever to pick something. I see sailboats I love, like the one in the planters peanut commercial. Not really a backyard project though. The slicer with a head was actually considered last year. I wrote to Mr B and bought plans for shivaree instead. Too complicated for my skill level at that time. I want strip plank or cold molded for that hull.
Thanks,
Bruce in NJ

----- Original Message -----

To: bolger@yahoogroups.com

Sent: Thu, 14 May 2009 13:42:48 +0000 (UTC)

Subject: [bolger] Re: Illinois Isometrics

Hi Bruce,

> I am looking for my next boat(s) to build. I would like a super sexy looking sail boat, you know, jaw dropping lines, timeless style, classic, lots of brightwork.

>

> I also have a 40 hp short shaft motor I want to build a long and lean hull for. Fishing only, built around a toilet for my lady. I have some ideas of my own and want to fold up some 9mm for the power project.

>

> Any ideas for the sail version that won't take years? I build fast but loose interest faster. Ohh, it must deal with the ocean.

You might look in the cartoon or study plan groups' files sections for ideas. Search Yahoo groups for "bolger" and you should find these groups.

For the sailboat, take a look at Summer Ease (also incorrectly called Summer Breeze in some places). Bolger told me none had been built, and I have been sorely tempted to build this one.

For the powerboat, look at the Fisherman's Launch in Bolger's book Boats With An Open Mind. It could be built in lapstrake plywood. You could also rig a toilet on Slicer (in the same book), but I'm not sure if it's considered an ocean-going dayboat or not.

Jon Kolb

[Non-text portions of this message have been removed]
• ... If you feel up for strip planking or cold molding, you should find the lap straked Shivaree even easier. I forget if you want a trailer sailer, but if not,
Message 7 of 24 , May 14, 2009
On Thu, May 14, 2009 at 9:24 AM, <echo172@...> wrote:
>
>
> Thanks, will have a look. I want to get started on this, I'm a fast builder,
> but it takes me forever to pick something. I see sailboats I love, like the
> one in the planters peanut commercial. Not really a backyard project though.
> The slicer with a head was actually considered last year. I wrote to Mr B
> and bought plans for shivaree instead. Too complicated for my skill level at
> that time. I want strip plank or cold molded for that hull.
> Thanks,
> Bruce in NJ

If you feel up for strip planking or cold molding, you should find the
lap straked Shivaree even easier.

I forget if you want a trailer sailer, but if not, a 'quick build'
Bolger sailboat that fits your which list could be the Burgundy.

http://www.flickr.com/search/?s=int&ss=2&w=all&q=bolgerboats+burgundy&m=tags
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