Is bulkhead tabbing now redundant?

Guess work !! No!! they just keep doing what they been doing for the last how ever long and live In hope !
YOU CAN SWIM CANT YOU ??
SO WHAT ARE YOU WORRIED ABOUT

 

too true Tunnels
I sleep on deck in my pfd

 

Is your P F D like wearing PJ'S ??

 

almost but I am always wary of being rescued in a pfd naked - lol

When I worked offshore as in 80m steel 'to class' myself and others had our immersion suits rolled out on the floor when we slept as we knew how poorly they are built/designed and I dont mean the welds, its the tin foil construction.
Lots of bending and cracking even on new boats

 

Never trust a sailor specially on a dark night !!

 

Wear a condom and a PFD to lessen the embarrasment.

 

you would need to ensure they rescued a woman as well......
and if your wife was at home....

I think its decided..sleep in immersion suit

 

Groper,

Attached an alternate method of joining cored laminate under LR rule. Note that the rule cites the required panel flexibility and includes the formula. DNV has a much simpler approach with only one side tapered. You have to rebate the core though to avoid fairing on the outside, otherwise, there will be numerous knuckles sticking out.

This is consistent with the rule on adhesives, that the best joint is a double overlap tapered joints.

Another approach, not exactly with the rules is joining the core at 1/4 span where the shear is far from vertical. Vertical shear is greatest at midspan and at the base of the laminate. The only relevant rule I can find is that LR allows limber holes to be cut at 1/4 span of a stiffener.

Suggest to make test on the panel and see where it breaks.

I will attach my comments later on the layout you posted. I was hoping for a midship section. I have to draw one for you.

 

do there rules change when the core material is different?
or the bulkhead is different?

 

Do you mean the panel core or the bulkhead core? When the two are different?

 

well all combinations, as you might have a ply bulkhead on balsa or foam core and either bulkhead on a foam or balsa core

 

It would be best then to refer you to LR rules. "Design Details" shows all possible combinations.

 

Sorry RX, didnt realize you wanted a cross section, here is one, typical of modern cruising multihull design in Australia today;

I can make many test panels as i have HEAPS of sandwich panel offcuts lying around. I will make them up next time i am doing some laminating. What kind of testing is most relevant to test the type of load in real boat? If you can describe the test, i will do my best to replicate it with some form of measurable pressure or force etc...

 

As I have noted repeatedly, all you do is apply a known load and measure the response of the layup, to establish the E and poisson's ratio in all 3 axis. In a nutshell that's it. Since all you are after is what IS the material properties you are using? Until you can define what this is, via coupon testing, the response is an unknown.

 

The problem adhoc, is that like many engineers, you can have extreme difficultly explaining yourself to a non-engineer like me. I have met some engineers, that can put into words something that i can understand immediately.

I am looking for particulars, like coupon size - does it matter? Can i make a smaller peice or do i have to make a full size panel, equivalent to the largest unsupported panel in the real boat? Does the test panel need to have stiffeners in both directions - such as a panel with horizontal AND vertical stiffeners - will this change the response? Or can i just use a panel with 1 stringer on the back of it?

Any other particulars relevant to ensure accurate results?

The devil is in the details, and ive never done it before, so i would appreciate a bit more detail...

As far as the E goes, there are published figures for infused glass laminates in epoxy - same as what im using. Sure the numbers will vary from peice to peice and process to process, but there is already accepted baseline numbers for various laminates based on their matix type, fiber type, and Fiber volume fractions. I have already measured the Vf in my laminates - so i should already have a pretty good idea of the E in the facing skins laminates - enough to make a good estimate. A while back, I made a 6m length, 230mm depth triangular beam (main bridgedeck floor stiffener) and applied known load, the deflection was almost spot on compared with predicted from beam theory equations and published material properties. Agreement was very good.

I thought we needed to test the response of the adhesive joint? Is it different to laminate properties? Is the E of the adhesive relevant? - I am a builder, not an engineer, i hope you can explain it in a context i can understand...