[MaxResolution]

I found them last year via a woodworker's link, and thought 'dumb site.' Note their flat panels say laminating with formica, aluminum, corian- 'to be advised.'

Very well, back to hulls. You guys have numerous issues at play. Acoustics and insulation still top my list, whatever the substrate. Epoxys and vinylized polymers are clearly advantageous, and quite case specific. Will we ever get around to bouyancy? Overall scale, and thickness?, or am I just delusional to preclude that laminates (over, say 8m) are not seaworthy in the least?

[Eric Sponberg]

Tri-star makes some valid points, but he seems to present it in a way that suggests engineers "forget" about the shear loads within cores. This is not the case. We engineers deal with both the face stresses and the core shear stresses all the time when engineering cored laminates. Core shear is not to be ignored, and in fact the ideal sandwich laminate will fail in the core and in the skins at the same time. In reality, one or the other (core or skins) will fail first, and the key is to achieve as much factor of safety in the design that is reasonable and consistent with weight, cost, and ease of lay-up.

Regarding MaxResolution's remark about steel hulls for this hypothetical sailboat (20-25 meters), certainly that can be done. All it takes is to engineer the boat to the material at hand--it's done every day. I am consulting right now on the rig for steel schooner of just that length, and boat designs can be found around the world from a number of notable designers.

Regards,

Eric

[tri - star]

To RNB:
This reply will be shorter - I promise.
( My daughters tell me, I some times pontificate a little long.....)

Yes, I agree with you - epoxy has merit. Being more resistant
to water than many materials.
People will say - but it costs twice as much.
Perhaps.........because it's TWICE as good ?

Here is a hull layup of a vessel designed AND built by us,
that has stood the test of time.
- X.layers of high grade F. Glass. ( On the water side.)
- One layer of Western Red Cedar.
- One layer of Fir.
- (2) X. layers of F. Glass. (On the inside.)
All held together with aircraft grade epoxy.

Note: In this layup; the core is - difinatively - HIGH density !

Note: It's common practice for boatyards to put more glass on
the outer, waterside of the core, than on the inside. Mostly for
cosmetic reasons.
However, our layup is ONLY concerned about structural integrity.
With ours - there is more glass on the INSIDE.
Because: Very high load impacts on the water side will more than
likely, cause failure to start on the INSIDE......
- As the rock just impacted, is creating a COMPRESSION loading
on the outside of the hull.
- And a TENSION load internaly.
- So often: failure starts INSIDE the vessel.
- As glass and carbon fiber are there to take tension loads:
It seems logical, to me - to beef up the area that most
needs to resist tension - with more tension resisting materials,
Than to do so, on the outside of the hull.

Cheers !

[tri - star]

To RNB

This reply will be shorter still........... I promise !
You indicated, RNB that you would like conclusive
scientific evidence re: cored hulls. Don't we all !

Some well engineered and well crafted vessels with
sandwich construction HAVE made many ocean
crossings. No debate about it.

You have had the benifit of disussing the pros and
cons, with various experts and manufacturer's
representatives. All of us - including myself - might
have vested interest in these concerns. Now, I'd
suggest, you conclud your research with a simple, low
cost procedure.

Go down to some boat yards. Close to quiting time.
Walk past the front office. Avoid anyone wearing a tie!
Talk to the guy with the grungyest overalls.
Take HIM for a beer.........
Ask HIM, what boats he dreads showing up again in the
yard for repairs.

To be clear. We HAVE produced cored boats - and will
do so in the future. Also, our vessels seldom show up for
repairs. Even the ones built 25 plus years ago.
So, presumeably, we know what we are about.

Regards.

[RNB]

Thank you one and all for your input and contributions on this subject. My concluding thoughts at this stage is to go for an advanced composite hull, that is, probably a carbon, kevlar, e-glass, Corecell, Epoxy sandwich with a sacrificial bow (yes I do believe epoxy is twice as good even if it is more expensive; though you are better to have a white rather dark blue hull given its thermal properties). I would also ideally like to go prepreg rather than resin infusion (finer unidirectional fibres rather than larger open woven fibres necessary for resin infusion). And finally but most importantly I will find a boat yard who has developed substantial experience in these building methods and really knows what they are doing. Again thanks to all. Regards. RNB.

[Codger]

I have an interest in cored laminates that is also non-marine in nature.
The bonding process is so critical and seems fraught with process failures.
Below is a photo of a helicopter blade delaminating. I only bring this to the discussion since if the aviation side still has issues getting it right with all the regs and process audits, how solid do you all feel about those processes in the marine manufacturing sector?

http://www.bluetonguehelicopters.com...une/cairns.jpg

[AMG]

In hull cores you don´t use honeycomb normally so I think they can not separate like that. Inside however there is an increasing use of glue instead of fibreglass to assemble the boat, which we don´t know how long it will last.

But on the other hand, most passenger planes are not using rivets but are also glued together these days...

[MaxResolution]

Darn those illegal laborers, I thought I told them to use more, not less glue!

Fact is, you can't get kids away from the video games long enough to teach them a real work ethic these days. I was sure I had a good, strong handle on this silly home theater niche, until I went through 11 shoddy 'trainees' in a row. Now I see why they charge $125.hr for computer repair. It's to cover their other 40hr work weeks that went unbilled!

[SandEngXp]

Originally Posted by MaxResolution

I found them last year via a woodworker's link, and thought 'dumb site.' Note their flat panels say laminating with formica, aluminum, corian- 'to be advised.'

Very well, back to hulls. You guys have numerous issues at play. Acoustics and insulation still top my list, whatever the substrate. Epoxys and vinylized polymers are clearly advantageous, and quite case specific. Will we ever get around to bouyancy? Overall scale, and thickness?, or am I just delusional to preclude that laminates (over, say 8m) are not seaworthy in the least?

I love the sarcasm... ...some PVC foams also carry USCG approval as bouyancy foam as they easily pass the requirements...

[SandEngXp]

Originally Posted by Codger

I have an interest in cored laminates that is also non-marine in nature.
The bonding process is so critical and seems fraught with process failures.
Below is a photo of a helicopter blade delaminating. I only bring this to the discussion since if the aviation side still has issues getting it right with all the regs and process audits, how solid do you all feel about those processes in the marine manufacturing sector?

http://www.bluetonguehelicopters.com...une/cairns.jpg

From The picture it looks like poor surface prep on the aluminum in the overlap. This is why PAA processing was developed. This area is prone to peel loading and bondline corrosion due to its location on the leading edge pressure side. If it were poor resin flow it would not have bonded to the aluminum honeycomb.