Bulkhead Tabbing at Chines

[weldandglass]

I'm building an 18ft cored skiff in a mold. I've tapered my 1/2" divinycell core so that the laminate transitions to solid laminate at the chines, as shown below. I'm about to start tabbing in bulkheads and have thought about several different ways to deal with the residual space between the bulkhead and the core, shown in the sketch below.

I was planning on ripping divinycell fillets on the table saw and tabbing over them along the hull planels but this will create a larger void at the chine. If I use a full size bulkhead that lays flush against the hull panel and build an epoxy fillet I can use small divinycell strips to fill in the void and tab over them. Or I could just not tab at the chine and leave the space open.

I was wondering what other builders were doing. Any input would be appreciated.

 

[Mr Efficiency]

Bulkheads in a small skiff ? where ?

 

[Mr Efficiency]

I'd say if you trowel in a generous fillet of lightweight filler ( Q-cell should do it) to fill your space, and spanning across from where your inside skins taper from the full sandwich thickness, you won't need much in the way of bulkheads cluttering things, you'd just need to glass across the filler on to the inner skins.

 

[Ad Hoc]

In your image above, you need to extend the "solid laminate" some distance past the joint so it is ovetr the core, at least 100mm.
Then you should have an angle (triangular shape) foam section to take away the hard spot that sits on top of the solid laminate that must also be on the inboard side. Then laminate as the exterior, some 100mm past this triangular foam section joint.

 

[TANSL]

A bulkhead should be seated on a transverse frame, an omega profile, to better distribute the loads that the bulkhead transmits to the shell. This way, in addition, the problem that you raise would be solved.

 

[gonzo]

The bulkhead is the frame.

 

[Mr Efficiency]

Whack a nice fillet into the corner, as I mentioned above, and the need for bulkheads and frames is vastly reduced, if not eliminated in a small, lightweight boat

 

[jorgepease]

That is the way I did mine, pic above, but I only infused one side at a time on a jig. In a mold you would probably have to pack that void with glass. I have no bulkheads on my 22' skiff just big fillets and it's entirely flat decked with a low sheer so not a great example.

 

[TANSL]

A bulkhead is not a transverse frame. That is a very common mistake but, however common it may be, it is still a mistake. The way of working of each of these two elements is totally different. The method of calculating a bulkhead has nothing to do with that of a frame, the loads applied on each one of these elements are totally different. A very different thing is that a bulkhead can be used as a transverse resistant element, of course you can.
Back to the OP's question, as always happens in a structure, there may be several solutions, as long as they are applied correctly. The solution that I propose, in my opinion, is the most correct but perhaps, given the special circumstances of this boat (which I do not know), can not be applied.

 

[weldandglass]

Thank you for the replies everyone.

The attached graphic shows the best approach, I think.

Ad Hoc:
Yes, I've added additional laminate plies at the solid glass area and extended those significantly over the tapered core.

Thanks.

 

[TANSL]

It should be noted that this solution serves to reinforce the entire length chine but that does not, in my opinion, serve the case of the bulkhead proposed in your post # 1.

 

[weldandglass]

TANSL,
Right, but the bulkhead could still be added and tabbed to the inboard side of the laminate/triangular foam fillet. It would therefore serve two purposes, reinforcing the chine and removing the residual space at the chine for easier bulkhead tabbing.

 

[TANSL]

Reinforcing chine is a different problem. If that was not necessary (there are other means of reinforcing it) or the bulkhead was not watertight, that hole or gap could be left, without having to close it.
(I have added a sheet of Lloyds SSC Rules, July 2016 to my previous post)

 

[weldandglass]

TANSL,
Roger that. I appreciate the input.

 

[fallguy]

Newb question....

What is the purpose of using solid laminate at the chines?

Is it just a requirement of 'special service craft'? Or is it that much stronger? Or is it just to comply with Lloyd's standards?

It is with good reason I ask as I am building a catamaran with about 9 hard chines, but the specs are different and I am running laminated corecell right to the chines and taping them all.

Thanks.