Stitch N Glue Foam Core Composite Hybrid, Plausible?

Derick Kelsall developed this method long ago to a far greater degree than you have even imagined. He called it KSS. One major note -cutting after laminating entire sheets is super wasteful. Quality core is expensive but the utilization rate can be very high if you laminate AFTER cutting. Take a look at KSS -he bends and tortures far more than you are proposing.

http://www.kelsall.com/UniqueKSS/WhatIsKSS.pdf

It looks like Richard Woods has experience/opinion on it. It looks like he uses it like you propose. He is always helpful and often lurking these threads.

http://www.sailingcatamarans.com/index.php/faqs/18-building-questions/93-what-is-kss

 

The above statements are not entirely true.

If you cut the foam before laminating - as i started doing in the beginning of my build - most of the foam offcuts end up bizzare shapes and most of the small peices ends up in the bin also. Sure you can re cut them and glue them together and make other peices - but the same holds true with peices that are already laminated - you can glass them together and use them. Alot of the pre laminated off cuts, end up being used in various places such as shelves, stiffening ribs, steps, gussets, etc etc Its far more efficient to be able to pick up and offcut and use it straight away rather than have to glass over a peice of foam before using it...

Its also far more difficult to infuse bizzare shaped peices, there is much more potential to stuff up the infusion and have dry spots etc - you really have to very carefully plan such infusions are typically use more consumables - some of the kelsall full boat length infusions typically take 3 or 4 days to setup, whereas i could infuse a similar sized rectangular panel in less than 4 hours setup time... So, I found it far more reliable and much quicker to setup and then infuse regular shaped, large rectangular panels and then did not have to setup more infusions for small peices needed later - i simply used the offcuts.

One of the previous posts states 6oz cloth on 5/8 core bends like 1/4 in ply... think about that for a minute... theres no place for "cloth" in structural scantlings - so this information doesnt mean much. Structural scantlings are typically 100% stitched, non-woven fiber reinforcements when used as efficient sandwich core laminates.

If something is more than twice as thick and is the same stiffness, it clearly has a much lower modulus. This is why its important to understand the fiber types and their orientation if your looking to bend fiberglass laminated panels. Most of the panels i built - were stiffer than equal thickness plywood.

 

One other thing that should be mentioned in this discussion is that CNC routers aren't terribly hard to build. In the overall cost of a large cat for example, an 8x40 foot CNC table shouldn't be a huge part of the cost. I suspect one could be built with sufficient accuracy for this type of use for under $10,000 USD. And of course you could use it for many projects.

 

i think the entire CNC routing fees for a 40ft sailing catamaran - using pre laminated panels from someone like ATL composites etc ran about $3500.

my CNC routing costs to do the MDF frames for the hull shoes and all the transverse bulkheads from PVC foam - about 25 foam sheets from memory - cost me $1100.
Its chump change in comparison to the total build cost...