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Which Tool for Relieving Bulkhead ?
Imagine a freshly cut-out plywood bulhead lying horizontaly on a table
before you. The bulkhead will be attached to, or installed into the fiberglass hull using 'bonding angles' i.e., several layers of 'glass / epoxy that will lap onto both the bulkhead and hull. I'd like to relieve, or remove, about 1/8" of the plywood (face) material all along the edge of the bulkhead (where it will bond to the hull) for (say) 3" from the edge on both sides of the bulkhead. In this way, the 'glass angles will lie flush with the bulhead surface. How do I do this? That is, wat tool(s) would be used for removing the plywood, leaving a clean cut of consistent depth? Appreciate any tips. Mike Worrall Los Angeles |
Which Tool for Relieving Bulkhead ?
mike worrall wrote:
How do I do this? That is, wat tool(s) would be used for removing the plywood, leaving a clean cut of consistent depth? A router. Rick |
Which Tool for Relieving Bulkhead ?
Rick wrote: mike worrall wrote: How do I do this? That is, wat tool(s) would be used for removing the plywood, leaving a clean cut of consistent depth? A router. A belt sander A power plane A block plane if you are a real masochist. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Which Tool for Relieving Bulkhead ?
Two possibilities:
Start with a router. Cut a 1/8" rabbet of arbitrary(~1/4") width around the panel. Grind the rest of the taper with a belt sander, a hand planer or a 7" grinder. The rabbet will show you the depth. THis will be an ugly process. Glenn's (justly famous) router scarphing tool might be a good start at a tool for this. It's limited to 2-1/2" max., so a little touch-up with a block plane or one of the above tools will be needed. Rick wrote: mike worrall wrote: How do I do this? That is, wat tool(s) would be used for removing the plywood, leaving a clean cut of consistent depth? A router. Rick |
Which Tool for Relieving Bulkhead ?
Or if your really brave, you could do this with a large course disk sander..
Takes some skill to control the big disk sanders. The builders of my hull, Blue Water Boats did a nice neat job of it and I believe it was done with a very large belt sanding machine. The chamfered the 1" bulkheads back about a foot all around and that is how far their hull/bulkhead attachment was carried on my 38 ft hull.. -- My opinion and experience. FWIW Steve s/v Good Intentions |
Which Tool for Relieving Bulkhead ?
I know nothing about router blades. Ignoring the possibility of a router
blade, you can get a consitent depth of recess by first scoring the area to be recessed with a saw set to the depth of recess you want. Perhaps run a hand held circular saw along a line parallel to the edge of the bulkhead and then run a few cuts between this first cut and th edge. If the depth to be removed is only 1/8" there will be no problem following a curved line with a hand held circular saw set at that depth. Then take a power sander and sand down until the saw cuts just disappear. If working with plywood its pretty easy just to sand off the face ply. Its obvious when you start sanding into the second ply. If the face ply is the depth you want to remove, you're laughing my son. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-freenet email must have "notspam" in subject or it's returned |
Which Tool for Relieving Bulkhead ?
William R. Watt ) writes:
... If the depth to be removed is only 1/8" there will be no problem following a curved line with a hand held circular saw set at that depth. I should have recommended using a rip fence on the hand held circular saw. Mine cost about $10 Canadian and has been very handy. I still mark the line to be cut so I can see if I'm cutting correctly, but the rip fence helps a lot to steady the hand. You can set it first to 3" and go around the edge, then set it to 2" and go around again, then to 1" and score the surface again. The three cuts should be enough of a guide to get a consistent recess with the sander. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-freenet email must have "notspam" in subject or it's returned |
Which Tool for Relieving Bulkhead ?
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Which Tool for Relieving Bulkhead ?
mike worrall wrote:
: Imagine a freshly cut-out plywood bulhead lying horizontaly on a table : before you. The bulkhead will be attached to, or installed into the : fiberglass hull using 'bonding angles' i.e., several layers of 'glass : / epoxy that will lap onto both the bulkhead and hull. I'd like to : relieve, or remove, about 1/8" of the plywood (face) material all : along the edge of the bulkhead (where it will bond to the hull) for : (say) 3" from the edge on both sides of the bulkhead. In this way, : the 'glass angles will lie flush with the bulhead surface. : How do I do this? That is, wat tool(s) would be used for removing the : plywood, leaving a clean cut of consistent depth? : Appreciate any tips. : Mike Worrall : Los Angeles How about a router table with the fence drawn back so that a straight router bit protrudes 1/8" of an inch out from the fence, and, of course, more than 3/4" high? Perhaps, instead of the fence you might use 2 vertical dowels for the curve to run against. I don't use plywood in my boat building but it's just a wild thought. haven't tried anything like that. --- Gregg Replicas of 15th-19th century nautical navigational instruments: http://home.comcast.net/~saville/backstaffhome.html Restoration of my 82 year old Herreshoff S-Boat sailboat: http://home.comcast.net/~saville/SBOATrestore.htm Steambending FAQ with photos: http://home.comcast.net/~saville/Steambend.htm "Improvise, adapt, overcome." Smithsonian Center for Astrophysics Phone: (617) 496-1558 |
Which Tool for Relieving Bulkhead ?
I would taper the relief rather than have the relief end in an abrupt
cut edge 3 inches in from the end. Is the bulkhead going to be painted? If it is then is won't really matter if there is some variation in the inboard edges of the fillet. I hate routers. noisey, dusty, too fast, and hard to control unless you set up a jig. I'd draw a line three inches back from the edge and hand grind a taper with a disk grinder( also noisey and dusty but easier to control by hand) being careful not to take off any wood beyond the line. Use the glue line in the plywood to judge eveness of depth. You could also bevel the edge off with a power plane or even a hand jack plane if you are good at sharpening one.(sharpening the blade is the secret) If you have a lot to do the hand plane would be tedious. All this assumes that you are bonding the entire perimeter of the bulkhead to the hull rather than just short little tab angles. I've seen it both ways and I can't really tell from what you wrote. If using multiple short tabs, I'd use a really sharp slick (a wide flat chisel with a long handle) to bevel slots that the tabs would be built in. By the time you figure out how to build a jig for the router, hand grinding it with a disk sander would have it done. The inboard edge of the glass "fillet" can be faired with micro baloons and epoxy but if you use strips of glass cut from a sheet of fabric on the diagonal, you will not have to deal with the hard edge of glass tape. Cutting on the diagonal keeps the fabric from fraying and orients the fiber correctly for this aplication. Actually, you can fillet the bulkhead to the hull without cutting a recess at all. The glass is not all that thick that it can't be faired to the flat of the plywood so that it can't be seen if painted. Either way will require some fairing and sanding to achieve a smooth joint. SteveJ mike worrall wrote: Imagine a freshly cut-out plywood bulhead lying horizontaly on a table before you. The bulkhead will be attached to, or installed into the fiberglass hull using 'bonding angles' i.e., several layers of 'glass / epoxy that will lap onto both the bulkhead and hull. I'd like to relieve, or remove, about 1/8" of the plywood (face) material all along the edge of the bulkhead (where it will bond to the hull) for (say) 3" from the edge on both sides of the bulkhead. In this way, the 'glass angles will lie flush with the bulhead surface. How do I do this? That is, wat tool(s) would be used for removing the plywood, leaving a clean cut of consistent depth? Appreciate any tips. Mike Worrall Los Angeles |
Which Tool for Relieving Bulkhead ?
Some very good methods have been sugested which made some good reading.
However, assuming you are using 3/4" ply, these 1/8" reliefs will remove about 1/3rd of the thickness and could(will) creat a stress point where the 1/2" thich relieved section butts to the full 3/4" section of the bulkhead. If this is a sizeable boat, and the bulkheads are tied into members that will introduce sort of a parrellogram like stress ( cabin floors, decks, ect) the working of the stress aforementioned stress point could , over time, delaminate the plys? Anyway, it's just a thought to consider. It would look slick but possibly at a cost. I doubt the such a delamination would have seroius structural consequences, but it might not be pretty. Delamination or not, certainly it would create a good flex point to crack your faired out smooth bulkheads to have cosmetic cracks. ( sorry spellchecker isn't working, got to fix that!) -- Ron White Boat building web address is www.concentric.net/~knotreel |
Which Tool for Relieving Bulkhead ?
The relief near the edge of the bulkhead should taper to zero, as should the
tabbing. Ron White wrote: Some very good methods have been sugested which made some good reading. However, assuming you are using 3/4" ply, these 1/8" reliefs will remove about 1/3rd of the thickness and could(will) creat a stress point where the 1/2" thich relieved section butts to the full 3/4" section of the bulkhead. If this is a sizeable boat, and the bulkheads are tied into members that will introduce sort of a parrellogram like stress ( cabin floors, decks, ect) the working of the stress aforementioned stress point could , over time, delaminate the plys? Anyway, it's just a thought to consider. It would look slick but possibly at a cost. I doubt the such a delamination would have seroius structural consequences, but it might not be pretty. Delamination or not, certainly it would create a good flex point to crack your faired out smooth bulkheads to have cosmetic cracks. ( sorry spellchecker isn't working, got to fix that!) -- Ron White Boat building web address is www.concentric.net/~knotreel |
Which Tool for Relieving Bulkhead ?
Gregg Germain wrote in message
I don't use plywood in my boat building but it's just a wild thought. haven't tried anything like that. Showoff! ;) |
Which Tool for Relieving Bulkhead ?
mike worrall writes:
Imagine a freshly cut-out plywood bulhead lying horizontaly on a table before you. The bulkhead will be attached to, or installed into the fiberglass hull using 'bonding angles' i.e., several layers of 'glass / epoxy that will lap onto both the bulkhead and hull. I'd like to relieve, or remove, about 1/8" of the plywood (face) material all along the edge of the bulkhead (where it will bond to the hull) for (say) 3" from the edge on both sides of the bulkhead. In this way, the 'glass angles will lie flush with the bulhead surface. How do I do this? That is, wat tool(s) would be used for removing the plywood, leaving a clean cut of consistent depth? Lots of ways to do it buy why bother? You are going to be using glass and fairing compound to bond the bulkheads to the hull anyway. The proper size beer bottle to form the fillet is probably of more concern.G BTW, even my smallest bulkhead had to be assembled inside the hull. These bulkheads were constructed using two (2) pieces of 1/2", 4 ply, CDX, temporally screwed together on the layout table to form a blank, some of which were 12 ft x 16 ft, using 4x8 sheets, then laid out using a tick stick and trimmed to size. Finished bulkhead is now disassembled, carried up into the boat, piece by piece, and reassembled using low cost steel deck screws and wood glue. The assembled bulkhead is now located in the hull with blocks that have been temporally attached to the hull with deck screws and tabbed to the hull with scrap glass pieces. (One layer of 24 oz double bias). When cured, the blocks are removed and the rest of the bulkhead is now glassed to the hull. When cured, fairing compound is used to fill all voids between hull and bulkhead and a layer of glass is laid over the compound to form a fillet using said beer bottle on the other side of the bulkhead. When cured, sand down plywood and the glass fillet edges, seal with 2 coats of epoxy, sanding between coats, then laminate two (2) layers of 24 oz double bias glass on each side of the bulkhead. After that, it's time for high build primer followed by LPU. It's working for me. HTH -- Lew S/A: Challenge, The Bullet Proof Boat, (Under Construction in the Southland) Visit: http://home.earthlink.net/~lewhodgett for Pictures |
Which Tool for Relieving Bulkhead ?
Backyard Renegade wrote:
: Gregg Germain wrote in message : : I don't use plywood in my boat building but it's just a wild : thought. haven't tried anything like that. : Showoff! ;) Well I just wanted to be honest that I was making a suggestion that I never tried. ;^) --- Gregg "Improvise, adapt, overcome." Smithsonian Center for Astrophysics Phone: (617) 496-1558 |
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