http://www.spinnaker.com/~waynec/sailing/
nice write up on a restoration of the above pictured albacore…
claudio, I looked at the thread you linked, and you showed 3 layer of glass. 162, 110 and 40 gm/m2
I converted that to 5, 4 and 1.5 oz/yd2 does that sound about right… I looked at Defender
http://www.defender.com/category.jsp?path=-1|10918|16458&id=311437&start=11&results=8&sort=products
and I figure I’ll get a yard of 6, 4, and 2
Marc,
I do not think you will need the 6oz FG. My yellow boat is a very light layup using one layer of 1.7oz and one layer of 3.7 FG. It is a bit soft, but very light. A better choice is two layers of 3.7 or 4.0 oz FG - that will add about 25g to the hull while making it much more resistant to any distortion. The 6oz glass shows up in 1M boats and larger.
too late, ordered the 6,4,and 1 2 yards of each… enough top make a few hulls…maybe I’ll lay up 4 and 1 and the use the 6 after it cures for build up along the keel and for servo supports…
Hi Guys,
Haven’t had time to check in for a while.
I use another method to arrive at a foam hull shape for a plug. First, I use urethane foam which is harder and sands more easily that styrofoam, although the dust gets everywhere and is unpleasant (not that styrofoam dust is too pleasant either). Urethane foam doesn’t tear out and the sanded foam doesn’t roll about under the sandpaper.
I start with four blocks a bit longer than the hull that I want to make. (I always make my plugs at least an inch longer that the finished hull will be. The reason is that if the plug were the exact length the tendency is to roll over the very end of the plug when sanding. By extending the plug any distortion in fairness at the “stern” of the plug will not be part of the finished hull.)
Onward. Two adjacent faces of each long block are scored with a pencil at the station locations square to the common edge. These same edges are then given a light coat of black primer (Urethane foam can be painted). When the blocks are glued together the painted faces form a cross running along the length of the boat that is a permanent reference to the centerline and the waterline. The pencil scoring will show up as dots that indicate the section locations.
Before the four blocks are glued together they need to be pre-shaped to rough outlines. Two of the blocks have one side cut to the waterline plan shape, the other two have one side cut to the deck plan shape. It is a good idea to cut out half templates of these shapes to trace from so that the outline cuts you make are as symmetrical as possible. The plan templates should have the section lines drawn on both faces. The two blocks that are designated as below the waterline should be placed with one painted face down on your table and the vertical painted faces of each block facing each other. Orient the template so that the section lines on the blocks align with those on the template. Trace the around the template on one of the blocks using the vertical painted edge as the centerline, then flip the template over, orient it, and trace the outline onto the other block. The vertical painted faces will form the centerline of the plug and the faces that face down will become the waterline. Repeat for the deck plan outline.
I cut the blocks about 1/16th outside of the template line. I use a borrowed bandsaw but I’ve also used a hacksaw with the blade set on an angle to the handle. The most important consideration though is to keep the blocks organized and to make sure that the waterline blocks and deck blocks are mirror images of each other and to keep them straight before you cut anything.
The rocker and sheerline are a bit more involved. Simply put, the offcut from cutting the foam to the template plan shape is pinned (I use cut down bamboo skewers) back onto the block forming a cradle that will hold the block steady. In the under-the-waterline blocks this facilitates transferring the rocker profile onto the block as outlined for the waterline and deck plan shapes above. Again, be very careful setting up for a cut, it is very easy to reverse a block and cut the profile backwards.
To assemble the four blocks together I use contact cement (again only useful on Urethane) held back an 1/4 inch or more from the edges of the faces to be joined. I glue the two waterline blocks together on a flat surface, waterline face down and centerline vertical painted faces together. The same for the deck blocks. Then the the deck assembly and the under-the-waterline assembly get contact cemented together so the centerlines of each assembly line up. Thus, a rough version of the hull plug with a permanent centerline and waterline that can’t be sanded away. The section locations are indicated by dotes that are formed by the pencil scoring and they too can’t be sanded off.
To start the fairing process a set of section templates is needed. The actual section shapes are voids in rectangular templates. They should have the centerline and waterline marked on them, and should terminate at the deckline. As the fairing job gets closer to final shape these section templates will fit over the plug just fore or aft of their correct position. This will provide info as to high and low spots and how much more material needs to be removed for them to come into alignment with the section location dots. Combined with a long batten to indicate longitudinal smoothness between section locations and it doesn’t take long to fair a true, symmetrical hull plug.
One other thought. I usually sink a piece of 3/8 or 1/2 inch ply into the deck assembly along the centerline. I try for at least 6 inches above the deckline. Once the blocks are assembled this plywood “tab” allows me to clamp the raw plug into a vise to hold it steady for fairing.
I have built plugs this way for some twenty years. It is the fastest, and most accurate method I’ve used. When I first thought of it I kicked myself for not having come up with it from the start of my boatbuilding efforts. In the old days I always lost track of the centerline and waterline when I was fairing a plug and had to try to find the locations by the faint impressions that showed up here or there. Yes, Urethane foam is more expensive than home center styrofoam but it works so much better, takes spray paint, and can be assembled with contact cement. Plus, there is no other material like templates of cardboard or tin or thin ply to create ridges in the plug introduced here, just foam.
Niel -
two kinds of foam -------
- EXTRUDED - which is pink,gray, blue and used for house insulation below grade
- EXPANDED - usually white and looks like little beads of foam. TERRIBLE stuff to work with.
I recommend the extruded - since it sand great, it doesn’t give off toxic fumes in you hot-wire cut, and it is not as dense as the urethane - but much more dense than the expanded stuff - think white styrofoam coolers or bait buckets. Some have used the wite stuff - and while lighter in weight, MUCH harder to get a nice finish.
Just my personal preference.
I am using the extruded BLue, free from work. all I can take…my shop looks like smurfs crapped everywhere.
I need to start hooking the vaccum up the saw and belt sanders when I use them…
went sailing tonight, so I’ll do the layup of the albacore tomorrow…
thanks for the ideas neil. before I assembled the station blocks using hot glue, I cut the waterline, and center lines with the bandsaw. about 1/2"deep. so no issues with finding center when the sharpie wears off…