connect two torsion boxes

[fallguy1000]

I am trying to come up with a fancy, simple way to connect two torsion boxes.

As you know the Skoota 32dm is good size.

The cockpit panels are removable.

They are two 4'x8' panels and connected on the 8' seam to make a single 8'x8' cockpit.

I want to use torsion boxes to make them nice and stiff and provide conduit for the hydraulics and electrics.

I have some rough ideas about how to connect them, but not sure for sure.

[fallguy1000]

Here is an idea in crude mock up. Not a fan..both sides would need the cut and covers.

Another idea is bolt them up and build a removable panel over the seam.

[Evan_Gatehouse]

Here is the picture of the underside of my Woods bridgedeck catamaran cabin sole and cockpit. Glass and corecell sole so stiffer than plywood.



The stiffeners are single skin glass with 3 layers carbon unidirectional on the lowest surface of the top hat shaped stiffeners. The sides are 2 or 3 layers of 400 gm biaxial and they also encapsulate the carbon.

I made a very simple mold from some melamine coated MDF. Ripped the angles on a table saw, glued and screwed it together. Inside corners filled with bondo. Then mylar packing tape over the exposed MDF and bog. Waxed the melamine surfaces.

In cross section it looks like this: _/--\_ (except the -- should be on the top of the / \ not the middle. Curse you ASCI art!)

This is called a top hat stiffener in composite construction. It is more typically done with foam sides and top but because I was going to take wave impacts I didn't want to worry about delamination and the single skin was strong enough.

Glued in place with thickened epoxy

This is what they looked like before cabin sole and cockpit sole were joined together (they were too big to install in one piece). Notice how thin the laminate is.

[Evan_Gatehouse]

Just realized I might have mis-interpreted what you have said. Is the sole two layers, with a 3" gap between them?

[fallguy1000]

That is a possibility Evan and then we could just laminate aluminum angle into the middle join, but if the laminate ever failed the angle would fall into the sea. I suppose I could just put a tape over the bottom of the angle and then the thing would never fail. The downside is I have to crawl underneath to line everything up.

I would need to make sure those channels can serve as service conduits for hydraulic steering and all the electronics from the engine to the helm. The helm station also sits above the cockpit panels and remember all are demountable.

Thanks for posting.

How thick was the corecell and do you recall the laminating schedule?

I only have 12mm corecell and have a lot of extra, so was hoping to avoid buying 3/4" core.

Then, to add a little more humor and fun to it, I had considered putting faux teak walkways from the boarding doors to the cabin entry for some aesthetics. Those are all built at 1/4" thick, so not to add misery to the trouble, but just the whole hope informed.

[fallguy1000]

Just realized I might have mis-interpreted what you have said. Is the sole two layers, with a 3" gap between them?

I had considered a torsion box design that is 3" thick with a 2" piece of core vertical in between. The torsion box would make it really easy to run service lines through it. There WILL be hydraulic steering and all the electrical lines in the gap or conduit if I use the method you show.

[fallguy1000]

Keep in mind, there is a join in the middle of two sections and mine are all removeable. That is the part I want to do well.

What are the dimensions of the top hats? They look like 3" wide by 4" sides? I would be able to probably run the hydraulics through one and the electrical through another.

I would have to finish the inside of them to make sure they didn't catch my electric and hydraulic lines on glass shards, but that is easy enough.

[Evan_Gatehouse]

The laminate was 2 layers of 666 gm triaxial each side of 3/4" corecell 80 kg density. It was a custom weave with most of the laminate running across the width of the roll (300 gm). The other two layers at +/- 45 were 180 gm each. This was for maximum stiffness across a panel width. The stringers were not that big. About 2-1/2" wide x 3" deep

[fallguy1000]

Thanks Evan

I had considered something similar. I will still need to make a connection if I run corecell and tophats. But it can be AL angle.

The other issue is I have to order 3/4 core, and probably inch core because I want flexiteek inlays....

Maybe I can laminate the inch core from my 12mm stuff...

[Evan_Gatehouse]

Yes, you can easily glue two layers of foam together. Some builders use a layer of glass between for "added toughness" but I think that is stupid. It's at the neutral axis and doesn't do anything.