Thursday, November 12, 2020

Flat Pack Composite Kits

Flat pack plywood small boat kits; all pieces CNC cut and shipped to you in a nice long box (or two) have been around since the mid 1990's. The local firm, Chesapeake Light Craft is a world leader in this type of kit, offering a wide array of plywood small boats in kit form; built stitch and glue with epoxy fillets. Back in 2014, Aussie Mark Hughes took the flat pack kit concept one step further and developed a composite carbon/foam flat pack kit for super-techy ultra-lightweight construction. In the photos below the flat pack kit makes a Bunyip scow Moth. Todd Oldfield, posted on Facebook on his build, which I have lifted and re-posted here.

The jig is CNC cut from MDF and is an intricate web of slotted panels designed to hold the frames.

Frames, topsides, and chine panels are cut from prefabricated vacuum-bagged carbon skinned foam. The Perverted Moth blog has the layup schedule for the Bunyip panels.

Jig assembled.

CNC cut frames in place on jig.

Topside and chine panels taped in place.

Fitting the bottom foam panel. The bottom foam panel is not glassed on the outside.This may be because the entire outside of the hull is covered in a wet/layup carbon layer to stick everything together.

Carbon ready to wet out.

Outside of the hull complete on jig.

Hull off jig. I would think there would need to be more gluing area along the gunwhales and maybe along the frames

Fitting the foam deck and foredeck. Note the cuts to help the foam bend around the curves for the nose block. A heat gun is also helpful for this.

Below: the first 2014 carbon/foam Bunyip M-scow with cut-out frames and mast support box. From Longy Oi:
"There are different versions, designs. both composite inspired by the ply Bunyip design. First build was the Mark Hughes M-Scow designed composite flat pack was built as Brian Sherrings 'Carbonara'. Possibly the strongest yet light scow built. Todd's build is to another (?bunyip) digitised design. I don't know the point of having the two designs, but, yes, some differences, there was some Wet lay-up on the latter build, maybe not on the MScow?"

It may be that a scow with it's shallow curves is more suited to this style of flat pack kit-building. Composite panels, being stiffer than plywood panels cannot be expected to twist up as plywood panels can. (Reference Todd Oldfield's comments below.) I could see someone also trying this method on the simple, Benoit Duflos Classic Moth Moth-Pop design.

Todd Oldfield answers some questions about his build:
"in answer to your question I didn't put carbon on both sides of the deck and hull under vac bagging as if i did that I would not have been able to get the desired shape in the panel if i did it on both sides. I went back after the panel was glued done and put a layer of carbon over that panel and relevant join on the chines. All the chines are covered ibn carbon both sides to. It was a good fun build that was quicker to do than expected and wasn't as hard as expected either by using a male jig to form the boat on."

1 comment:

Michael Storer said...

This is great!

I have been watching the build on the Scow Moth Facebook group.

There is always something new to pick up when Moths are built. They have always been among the most innovative, if not the most innovative small boat structures