Whats the strongest bulkhead joint

[leegrace]

Hi,

Just wondering what the strongest way to bond a plywood bulkhead onto a GRP hull is?

Use fillets, L brackets bonded to hull and bolted through bulkhead, etc?

Thanks

Lee

[BillyDoc]

Hi Lee,

I should leave this to the experts, but I suspect you are asking the wrong question. If you make your bulkhead/hull joint stronger than anything else in your structure, you are going to shift stresses elsewhere and probably cause a stress concentration fracture nearby. Perhaps a better question would be: "How can I balance the strength of my bulkhead/hull joint with the strength of the bulkhead and the strength of the hull." Ideally, the whole structure will have essentially the same strength throughout its various parts. That way, weight and materials are minimized and overall strength is maximized.

Bill

[lewisboats]

I would say filleted (Epoxy), then 3 layers of cloth, each wider than the last, on each mating surface (both sides, top and bottom) of the bulkhead.

Steve

[jegsmith]

The best way to join a bulkhead to a grp hull is by using high density foam blocks between the bulkhead and the hull to spread the load of the bulkhead around the area it is being bonded to the hull. Fiberglass tabbing must be applied over this assembly. There needs to be a lot of contact for the fiberglass tabbing and dont forget to wet out the plywood before tabbing it on because the plywood tends to absorb whatever glue used and cause a dry and weak joint.

[leegrace]

Thanks for your replies. Its not for a real life situation but for a university project so it is a case of making it as strong as possible but also get the balance with weight as the assessment marks will be awarded for the load taken before failure divided by the overall weight of the test panel.

http://boatdesign.net/forums/showthr...3830#post73830

Thanks for all you input. Keep it coming!!!

[Darren]

Hi
We use 1152 PA (Filleting Paste) with a 50mm rad & then bond the bulkheads to the hull/deck using chop strand/biaxial/chop strand
We use this method on boats up to 30 mts

[LP]

+/-45 deg. bi-axe will give greater strength across the joint since all strands will be crossing the joint whereas, 0/90 will have half of the strands running parallel to the joint with no contribution to the strenght of the joint. The chopped strand mat should not be needed if working with epoxy.

[PAR]

Isn't the object of the lesson problem, to insure you understand the concepts and can work toward the solutions with the necessary engineering?

[glassman]

it seems the kids today dont want to get dirty , Par ,I like the way you think

[BOATMIK]

The strongest joint is the one that you have added the most materials to and that affects the largest amount of material in the panels being joined.

The limitation comes with expense, weight, complication.

MIK :-)

[Robjl]

What thickness hull and bulkhead are we dealing with?
And how will it be supported for testing?
Need this to advise on layup/connection.
Cheers
Rob