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Monday, August 30, 2010
Anyway, speaking of inspiring talks... we chatted with Dave King about his Pacific Cup winning Westsail 32 "Saraband". He said the boat has gained nearly a knot by doing some simple underbody fairing mods to improve laminar flow and reduce drag. As he described it, it sounded quite easy to do, as the mods are not structural. Just simple glass over foam against the existing hull. While not exactly the same thing, this got me thinking about the gap between the skeg and rudder on our W42.
Since we installed the rudder, there is about a 2 inch gap between the skeg and leading edge of the rudder. Enough of a gap that I think would increase drag. If you look at most sailboats in the yard, with skeg hung rudders, the trailing edge of the skeg is often closely molded to receive the rudder. This improves flow and reduces drag. I had been wondering how to fill this gap, or if I should even bother. But one thing Dave kept saying about his mod was "Hey, the boat is already out of the water, and it is an easy project." So, that pushed me over to try something.
After a couple hours on the 3D software, and CNC machine, I had cut a couple shims machined from Coosa fitted and ready to be glued/glassed. I am not sure this will yield a knot gain in speed, but you never know lol.
Modeling the shape of the shim.
Test cut using cheap insulation foam.
Final piece cut from Coosa
Final fit of the shim
Thursday, August 26, 2010
One thing this machine has changed is how I look at construction problems. Which should not be surprising I guess. The more tools you learn to use and add to your toolkit, the more difference is made in approach to design and construction (you craftsmen out there are probably saying "duh!").
One thing the machine has helped with is "time management" of the project. When you are holding down a day job, you need to make the most of your time in the morning, evening and weekends. And, manage all that with the rest of life's responsibilities. The machine allows my typical work week to go something like...
- Stare at the CAD program over a cup of coffee in the morning, have things drawn/designed by Tuesday
- Process the cutting files by Wednesday
- Machine cut the parts cut by Friday
- Have everything ready to build/assemble/install on the boat by the weekend.
And finally, there one thing I find amusing about all this. I have yet to use this machine for one of my primary reasons for building it in the first place: fiberglass mold making. Why? I have been too busy discovering other applications!
Tuesday, August 24, 2010
Without such a hatch, should you ever need to quickly get into the engine room from the cockpit, you would need to scramble down the companionway, go through the galley, through the tunnel, into the aft head, to the door to the engine room. With this addition, you can open the hatch and drop right in. If you fit that is. I better not gain any more weight or else this may be useless.
I got the idea from Dave on the Westsail 42, Elysium, but took a slight different approach to his otherwise perfect installation.
The flange that supports the hatch and provides the pathways for the water drainage was built from Coosa (instead of molded from fiberglass, as was Dave's method). The CNC machine was used heavily to provide the template for the cutout and for cutting the pieces of the flange. Edges were rounded over on the "manual" router table, and the whole thing assembled in place and glued in with thickened epoxy and thru-bolts.
Final sanding, trimming and paint, as well as choice of latch mechanism, will be done when the deck is refinished (not this year).
For completeness, here is the slide show...
- maximum 4 feet by 4 feet cutting area (larger can be cut with a bit of cutting file trickery)
- high speed lead screws give linear motion up to 300 inches per minute
- hardened steel bearings ride on rails of steel angle stock
- spindle is a Porter Cable 7518 3.25 hp variable speed router
- stepper motors that drive the lead screws are of the high torque variety
- Gecko G540 motor controller running at 48VDC.
- a Dell Inspiron laptop (inherited) drives the table using Mach3 software
- the table has mechanical (rail clamp system from Rockler) as well as vacuum hold down (made from PVC pipe, ultra light mdf and a shop vac)
- a special dust shoe (made by the machine itself), clamped to the router, around the cutting bit connected to a 4 inch dust collection hose sucks up the chips and dust during cutting (note, the dust collection system was already in place for a couple years)
- The router and vacuum table are switched by software.
Since the machine has been up and running, it has played some role in pretty much every boat construction project since. Whether it is cutting parts, templates jigs, etc. Some samples are
- Shop cabinets. All pieces, shelf holes, hinge holes, doors were cut with the machine. This was the first project where I got to know the ins and outs. The cabinets did not come out perfect, but I learned a lot about calibrating the machine and using different style bits.
- Dive tank and propane tank locker. The upper and lower pieces of the tank assemblies, cut from Coosa board, where cut using the machine. This made the building of the assemblies quite easy.
- Templates and jigs. The machine was used to cut plywood jigs to help spot and cut the openings in the deck of the boat for the dive tanks, propane tanks and cockpit coaming compartments.
- Anchor bow roller assemblies were mocked up with pieces cut from plywood. All cut from the original CAD designs of course.
- Deck hardware backing plates, cut from 1/4" aluminum plate. This machine can cut it, albeit VERY SLOWLY.
- General cutting operations. Like when you need to cut that odd size hole where you have no appropriate hole saw
Next, Secret Weapon Revealed Part III: Reality and Building the Boat
Saturday, August 21, 2010
This video shows some of the basic operations such as drilling holes, cutting pockets and dados and the final cutout. Straight and curved edges.
There are more videos on my YouTube channel http://www.youtube.com/user/westsail42
Tuesday, August 17, 2010
I built this last fall using unistrut, MDF, UHMW plastic, steel and aluminum extrusions, and a number other parts all easily sourced from your local Home Depot/Lowes and the Internet.
A few years ago, within the first year we acquired the Westsail as a bare hull, the admiral and I attended the IBEX marine builders trade show in Miami. There were numerous companies showing off their production quality CNC cutting machines. I was drooling. My wife kept hitting me in the arm and saying "we don't need one of those!!" With average prices starting around $45,000 she was right. Nevermind that we would not have the floorspace for one of these things. But still, I was drooling. Over time, I kept looking at these machines. I came across a "hobby grade" machine, www.shopbot.com, but the prices were around $20,000. Still too rich for my blood.
Cunning and Deception
Then sometime last year, whilst browsing www.cnczone.com, I learned of a DIY CNC table design called "Joe's 4x4 Hybrid CNC". The plans could be purchased for $100, and, the more critical custom parts could be purchased for $400. With that you got access to the Joe's CNC forum were other machine builders describe their tips, tricks and modifications. The trick here was how to sell this to the wife (here comes the cunning and deception bit). I started with purchasing the plans to research what the machine could actually do and how it could be applied to the known remaining boat construction projects, with which I would occasionally mention "You know, a CNC machine would really help with 'xxx
As I was quietly accumulating the necessary hardware to at least start the base table, one week while my wife was out of town, I started assembling the base table out of unistrut. Of course I got an earful when she came back when, despite my assurances that I was trying to control costs as best as I could, she pretty much resigned herself and said "well, you are going to do what you want anyway". I felt really guilty, but I knew this machine, when complete, would be really handy for stuff. I just could not prove it.
So, for about two months I acquired parts,selling eBay stuff and paying cash all long the way (as best as I could), and spent every other weekend assembling, squaring, aligning, gluing, sanding and painting (with some unplanned dis-assembling and re-assembling), all under the suspicious eye of my wife. Just before Christmas 2009, I had a machine ready to be fired up. Total cost: about $3000.
I connected up the electronics, fired up the software and did some initial calibrations. Movement! Shortly thereafter I had the machine doing some test cuts on cheap plywood. Soon, I had the machine cutting the final parts, that would ultimately be used the machine. After witnessing this, my wife later came up to me and said something like "Wow, thats pretty cool, can it cut a 'XYZ' part for one of MY projects??" I took that as evidence as she was finally sold on the idea.
Yes, we are still married.
Next in Part II: Tour of the machine.
Tuesday, August 03, 2010
C4 standing for "Cockpit Coaming Crap Compartments"
Whilst sailing in our little 28 footer the cockpit often accumulates various items such as winch handles, handheld GPS, handheld vhf, sunscreen, autopilot remote control, sailing gloves, and numerous half consumed bottles of water (the crap). The small boat has cutouts in both sides of the cockpit coaming (which is basically the "backrest" of where you sit) handy for storing these items. Close enough to throw stuff into and retrieve from without taking your hands off of the helm. The original Westsail 42 did not have any handy storage for this stuff in the cockpit area. So we added some. Two holes cut into the port side coaming and walled in from the underside. We elected not to do the starboard as it is above the "tunnel" to the aft cabin and may look odd from the inside. Besides the one port side compartment should be big enough.
Walled in with coosa board, glass and epoxy with the inside corners filleted with thickened epoxy, it passes the leak test (I tossed a gallon of water in there with no leaks into the engine room). The compartment is positioned to allow for winches (including electric winches), mounted on "top" of the coaming, fore and aft. The forward wall has a hole where a ventilator fan will be mounted to help keep the engine room cool.
Still To Do
- strategically spot a drain hole or two (to the outside of the hull) to keep the compartment dry
- sand and paint the inside. White? grey? something in between?
- fabricate and fit removable "doors" to the compartment. Perhaps locking. I need to see what sorta hinge hardware is available