Monday, October 27, 2008

CNC Routers, Vacuum Bag Test and a Surf Canoe

This past week was a hodgepodge of work. The F22 building process is somewhat on hold because I'm waiting for materials to be shipped from the mainland. Hawai'i is a wonderful place unless you need to find unusual materials. Biaxial fibergass is one of these. I'm currently waiting for a large shipment of fiberglass, fillers, vacuum bagging material and laminating tools from Fiberglass Supply in Washington state. It will probably be another two weeks before it arrives. Bummer.

Until then, I have been keeping busy with several mini-projects. The first one is a test of pulling a vacuum bag on the foam surface. When I was laying the foam strips down for the core of this boat, I extended the strips proud of the keel join line and further forward and aft of the ama's overall lines. On these extensions, I covered the foam with a putty mixture of epoxy, microspheres and colloidal silica. To test the vacuum that could be achieved, I re-used a piece of bagging material from another project, recycled breather material and a single vacuum port.

The picture below illustrates this better than I can in words, but the net effect is that I was able to obtain a vacuum pressure of 12 in Hg (roughly 6psi). This is not ideal (I'd prefer around 15-20 in Hg), but it will do. I think the leaks are due to the fact that 1) air is being drawn from the deck flange, especially at the bow and 2) I am reusing bagging material with holes that have been patched with masking tape (the blue tape). I'm hoping that the actual bag will be a bit better.


























Also, the Marine Education Training Center now has a CNC router, which takes CAD drawings and converts them into computer code (G-code) to cut out patterns. We have a three-axis router and I hope to use it to cut out bulkheads, form frames, the deck and foils (daggerboard + rudder). It is so cool to watch the router process, so I have attached a video below. The sharp pitched squeaking noise is from the spindle RPM being too low. We increased the RPMs from 12,000 to 18,000 during the cut to eliminate them.





Finally, I spent a large part of the week filling and fairing a 4-man outrigger surf canoe, which I built from April to August and now just needs to be painted. I built this boat because it has a similar construction to the F22, foam core and knitted double bias (+-45/45) fiberglass with epoxy resin. It is reinforced with carbon fiber stringers for the hull and around the waes in case the canoe will be sailed (to anchor traveler, etc).


5 comments:

Tor Rabe said...

I think also 3) It is not possible to get a tight seal between foam and tape, you have to either lay down a strip of putty or a strip of peel ply as an attachment point for the vacuum tape.

I also think the deck flange area will cause you trouble. I ended up hand laminating the reinforcement layer, then using that as a mould for the vacuum lamination.

I wish you luck with your project!

Mike Paulding said...

Tor,

You and I are on the same wavelength for this task. I ended up coming to the conclusion that I needed a layer of the deck flange as a surface for the sealant tape and also hand laminated the reinforcement layer.

I mixed a slurry putty of epoxy and microspheres to form the bagging surface on top of the keel foam, which was 1-2" proud of the keel batten. I was able to attain a pressure of 22 in Hg using this approach.

Perhaps I should read the blog comments before I "reinvent the wheel".

Thanks for your insightful feedback.

Aloha,
Mike

VW-Whispher said...

Hi Mike,
I am looking for a CNC Foam Cuter in the Honolulu area. Can you point me in the right direction.

Thanks
Sam
soajay at hot m a i l .c O m

Frank Hylewicz Fräsmaschinen said...

Hi Mike,

what type of router motor do you use for that, how many watt etc ?

Frank

Frank Hylewicz Fräsmaschinen said...

Hi Mike,

what type of router motor do you use for that, how many watt etc ?

Frank