Stitch N Glue Foam Core Composite Hybrid, Plausible?

You're not understanding what's being posted.

It doesn't matter what size sheets of foam are available to you, you can make any size laminated panel you want. You don't have to scarf joint the foam together before infusing, just butt joint with glue. One or both sides are then infused, then you cnc cut the parts needed from that large laminated panel.

It is not practical to cnc the foam to shape and then infuse, as excess resin and glass will get all over the precision cnc edge and render all that costly precision null and void. You might as well save the money and use a steak knife to cut the foam.

 

Isn't the practice of joining foam sheets to use sinusoidal join lines so the panel bends more evenly ? Butt jointing could cause a kink in a curved panel, even after laminating both sides.

 

I doubt that such a kink would normally occur. Doesn't happen with plywood and well executed glass/butt joints so would be less likely in foam.

 

Not a problem...

 

He wants to CNC rout the panels after infusing tho sam - unless you have one of those multi million dollar HUGE CNC beds, your generally limited to small panel sizes which can fit on a standard size CNC router bed...

If it were me - i would get the foam sheets CNC marked - then put them together and infuse massive rectangular panels with all the marks visible through the infused glass. You then have the panels, bulkheads and cutouts marked and fully nested and all you have to do is cut them out using circular saws and jigsaws - pretty quick and easy job if all the patterns are already there for ya... I would also incorporate as many rebated edges as possible for any areas you know have to be taped or glassed over during the same process so you dont have to fair out the raised edges etc

 

Not stitch and glue, but damn close to it. This may interest you. Its in french but the pics tell the story:

http://seasailsurf.com/seasailsurf/actu/4701-l-exocet-40-d-elie-canivenc-prend?lang=fr

 

Great Link, Thanks!

The design of that boat with it's hard chines would work well for my concept, just maybe not in that size. They are still using a male mold frame, something I was hoping to avoid. I'm thinking of something in the 25 ft range, the structural bulkheads acting as the sreaders for the hull form. Some bracing would be required, but not as extensive as the mold used on the featured hull in the link.

 

OK, I see this now...

 

It's not that simple unless you don't mind fairing as well. The planks "pull" a little on each bulkhead if you do that and will need fairing afterwards. By using the battens on the mold you can take out this problem. Once the planks are glassed to each other, the Chines will be fair lines and hold their shape due to the inherent stiffness of the chine edge.

 

Try this one... it was the first boat built like this. If you want more information, google "araldite mini transat". its a 6.5m ocean going yacht, built in much the same way. How many bulkheads are you going to use? might be possible to use a few bulkheads, and a few temporary formers which are later removed.

https://vimeo.com/21878671

 

Okay, lets try this again. You assemble a bottom pan like in the video above and erect some bulkheads. Then you go assemble four stitch-n-glue leaves. They are port and starboard pairs of forward topside to 1/2 the fordeck, and aft topsides to 1/2 the aft or side deck. These four pieces can be individually fitted to the molds and removed again. They can be fully outfitted with furnature, electrical, water, and the finish applied inside and out. Pieces are small enough and light enough to be carried around. If there are two main bulkheads about 18" apart where the fore and aft pieces join, then they can be butt-blocked; and all the electrical and plumbing controls can be fitted between the two bulkheads, so you just connect a few wires and hoses. A king plank joins the centerline. The cockpit is a separate structure. I designed one like this that had, as a final step, strip planking a small radius chine. All the wiring and hoses ran along this chine, so I would be able to get at everything until the very end.

This is what I had in mind at the time -
http://www.boatdesign.net/forums/boat-design/full-length-keel-27476-2.html#post275930

 

That video was incredible, thank you!

 

Very cool... advancing the concepts of production efficiency as well as design. Thats what I'm after!

 

The Scarab trimarans are designed to be built as foam stitch and glue. I'm almost done with one. Pretty easy. I built mine in PP honeycomb though.

FWIW - if you're in the USA - Plascore the PP honeycomb supplier I worked with can infuse sheets as large as 7x50 feet IIRC, and they can CNC cut to your drawings and deliver all the pre-cut panels ready to stitch. Might make for a quick economical build. If I were doing it again this is what I'd do.

 

5/8" 4-5 lb PVC foam core with 6 oz cloth on either side will bend very close to quality 1/4" plywood. You later add the rest of the lamination once you have the shape.

You can then keep the same mold spacing as you would if you were building with a stiffer core to begin with.

We tested this at my former business.