Is bulkhead tabbing now redundant?

The tabulation in the link is basically unreadable RX... its too small and pixelated...

As we have new design approach, i think its easy to solve the tension/compression problem in the frame/hull interface, If the foam cored frame is decored around the edges and unidirectional reinforcement added where the foam was. Both faces of the frame still have +-45 stitched biax. This reinforcement doesnt have to happen afterwards either, its very simple to make the frame with this reinforcement inside it, when the panel is infused, everything in 1 shot.

Then provided the adhesive is more flexible than the UD fibres, the UD fibres will absorb the tensile/compressive stresses along the interface between hull/frame.

So now we are looking at an I-beam, bonded to a hull plate...

 

Found this;

The issue of secondary bonding between polyester and epoxy substrates has been an area of concern for some time. Comparative in-house tests have abounded, but without quantative results they can only demonstrate modes of failure and give a 'feel' for the force required at break. ISO 527 was modified to accommodate a tensile double lap joint. Four types of specimen were tested to show that polyester tabbing has the same strength when bonding polyester or epoxy substrates.



* Interlaminar failure occurred with the CSM layer of tabbing laminates
** One specimen showed adhesive failure between the tabbing and substrate.

A - Polyester peel plied substrate, polyester tabbing
B - Polyester sanded substrate (80 grit), polyester tabbing
C - Epoxy peel plied substrate, polyester tabbing
D - Epoxy sanded substrate (80 grit), polyester tabbing




So it seems that in house testing determined that the maximum permissible shear for a polyester tabbing is around 6Mpa with interlaminar shear failure mode, mostly through the csm bonding layer... pretty poor...

The same company that did this testing, also tested the epoxy adhesive i referred to earlier, they tested the toughened epoxy adhesive to an E-glass substrate prepared by peel ply removal and it was found to be 16Mpa, which is almost 3 times greater. Would this imply the bonding area could almost be cut by 300% (omit the tabbing) whilst maintaining same strength?

 

Protruded I-beam Stringers, Bonded in

Another I-beam theme...
http://www.boatdesign.net/forums/bo...erstructure-topsides-47349-11.html#post640845

 

That seems to be the approach that Buizen Yachts has used that I referenced earlier, the cabinetry simply "floats' on a bead of sika or similar withing the structure, of coarse it must add something to structure also but I believe that skin/floors/main bulkheads /CPknees etc were competent alone to cope.
I got an NA to design/ simplify the structure of my cat to include tank tops, bunk bases & a longti L/J shaped "bench top" as the topside stringering, this bench is in "solid" glass(with gelcoat) & has been approved for single sided(underneath) tabbing for neatness. Any further cabinetry back screws or bonds to the back of the L.
Jeff.

 

Great, and your boat is polyester built... You main top sides stiffener is approved by NA to be tabbed only on 1 side, using polyester tabbing... We are getting closer to the truth, of what is possible...

 

However a sandwich panel in the same location would have required tabbing both sides, that's why it's in solid with uni in the "downstand" of the L bench top & not having to grind the gelcoat off for the upper side is a bonus in finish.
Jeff.

 

What the chart also tells us also(that we already know) is that peelplyed polyester surfaces need to be abraded to get a good bond.
Jeff.

 

Oh my giddy aunte !!! where do you get this information from ?? mad magazine ??

tabbing one side !!
have you Learned nothing at all?
what happens to a stiffener that tabbed one side when it goes under load ?? want to take a guess ??.
usually the tabbing will allow it to simply fall over , lay flat and becomes completely useless !! so why even have it in the first place ??
and if its true that a NA APPROVED SUCH A THING THEN HE TO IS A FRUIT CAKE !!

 

& ranting WHEN NOT UNDERSTANDING THE APPLICATION( sorry, not shouting....... my dog wants her dinner & pawed the caps lock!) is a bit cake like also, of course being a bench it's actually tabbed on not one but three sides................. but just on the bottom*
Think about it, plenty of spots in boats get tabbed one side only, tunnos you must of worked on some real jellyfish boats to be so concerned.
All the best in your endeavours from Jeff.

 

Tunnels, you really act the goose sometimes... it was clear to me, without jeffs clarification in his second post, that the L stiffener would have had to have significant flange on it, for bonding to the hull... all done in solid glass, and the flange ends up tabbed inside his cupboards/bench so its not really visible, unless you open a cupboard door crouch down on your knees, and look up inside to the b ack of the cupboard... In other words, his solution to ugly tabbing that laters needs to be faired out, was solved like this - the same reason im looking at different options.

BTW - my 1mm laminates are 1200gsm Dbias +-45deg ... but wait thats impossible i can already hear you say...

 

Just had pizza, once finished the dog......... Roxy the foxy... knows & insists it's time for her to eat, of course in a pizza you can have cheese on top, on the bottom or both & some parma ham too!
Jeff.

 

i dont want to be a part of any of this !!

YOU think you have all the answers when and just about every thing you post about is absolutely taboo !! and nearly all of what is getting written about has a very very short life expectancy . just one freak wave and you are history like as in swimming with a broken boat and bits floating . you think its funny almost when in reality its not . boats we built sailed the tasman sea between AUSTRALIA and NEWZEALAND and we prided our selves of never ever having had a boat that had one single misshape ever of one small problem of any sort . we made boats to last and live to finish races and never loose a member of the crew . I know for fact that some of the things you will try and even with all the calculations exceeded will fail if and whe you boat is pushed beyond acceptable levels because of here say silly illogical methods and way you want to construct your boat and you have I notice been treating just about every one that has been involved with all kinds of boats as though we are idiot's and you are the lord and master and we know nothing at all !! one day your high perch is going to snap and you are going to realise oops maybe you should have listen a little more intently .
I don't want to read any more of this thread . I really don't

 

Tunnels, I looked for a comma in there but couldn't find one !

 

But what about all the miles we sailed in our little wooden boat built from match sticks? do you think we never saw a storm or a bit of rough weather in 10 years of sailing? How on earth did we survive? We must have swam to shore, braved the sharks and rebuilt our boat a dozen times according to you?

 

Tunnels,

Your a little inconsistant............. in this post you claim to glue down a deck as follows.... tunnels tunnels is offline
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by the look of the date on the post i would say hes well past that and could be sailing by now . Here in new zealnd there is a flexable type of epoxy that is just what the doctor orded for that type of work . its an epoxy ,semi flexable, sticks like nothing i have ever used before , has a long working time is easy to use and easy to clean up, we did all the 8 deck and transom joins on the match raceing boats i made in South Korea .There was no fastenings at all through the decks they were just glued and not even glassed on the inside !! The outside we had a 5mm groove between the deck and the hull as the squash out area and just coved it and took off the surplus and that was it !!Fantastic stuff
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HPR25 ,comes in 2 colors ,white or black , its 2 to 1 mix is easy to use , its made by Adhesive technologies ltd here in Auckland nz . Its is west system resin based so has a good reputation . The 36 ft match racing yachts we were making had the decks and the internal floor grid over the keel stub socket ,that included the mast step was also stuck down with HPR25 . The boat in a fully finished condition was lifted from its cradle into the water each day on one single pin that went through the FIBREGLASS floor grid and had a STAINLESS STEEL yoke attached to the lifting strap from the crane .

............ & yet if Groper is investigating blobbing a bit of furniture in with a similar compound........... you have been blobbing critical hull to deck joints.....
Just an observation, I'm sure with the correct application & joint design both can be successful.
Regards from Jeff.