Replies

1. 
   BobSmalser | Jul 01, 2005 04:37am | #1

   Why not log on to woodenboat-ubb.com and ask the folks who do it every day?

   3/4" is one heck of a coaming....you sure it wuz originally this thick?

   Unless we're talking a 60-foot schooner, you can probably use half-inch and spring them into bedding compound (Dolphinite or polysulfide dyed to match the teak)...leave the clamps on for a couple days and the coamings will take a set with no undue pressure on the screws.

   But 2" over 8' ain't much of a bend....but if it's 2" from center it's a 4-inch bend, eh?

   If the teak is especially stiff, wrap the center in rags and keep boiling water on it for a while....then clamp it in as described above dry....let is set...then bedding compound and screws later.

   You can also use a poly bedding compound like 3M 5200 or the cheaper non-marine equivalents like Vulkem Poly Sealant that'll be adhesive...but it'll be hard to remove for future repairs.

   
   

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   Edited 6/30/2005 9:49 pm ET by Bob Smalser

2. 
   jazzdogg | Jul 01, 2005 04:39am | #2

   Bruce,

   In addition to kerfing, common bending methods include (1) steaming the wood for about an hour per inch of thickness, bending the steamed lumber over a form, and clamping it in place until it takes a set and (2) resawing the stock into several thin strips than can be glued together face-to-face and likewise clamped to a bending form until the glue has cured. Some species are said to bend quite readily after they've been soaked in ammonia - though this isn't a technique I've tried.

   Some species bed readily, while others will resist your efforts vigorously. I've never tried to bend teak, so I cannot say whether common bending methods will work with 3/4" teak.

   Good luck,

    

   -Jazzdogg-

   "The trouble with the world is that the stupid are cocksure and the intelligent are full of doubt." Bertrand Russell

3. 
   hammer1 | Jul 01, 2005 07:59am | #3

   Teak is a tough species all around. Famous for dulling blades and not holding glue. Steaming wide boards usually results in cupped lumber. The oils in teak resist glue adhesion so freshly milled surfaces and an acetone wash are typical precautions. Resawing a wide, dressed board for laminating will be challenging. Often, the best lumber for bending is riven and green, not sawn and kiln dried.

   There is some misinformation about ammonia and bending. The experiments were conducted in a university. The ammonia used is anhydrous ammonia, a dangerous gas, not household ammonia. The lumber and gas are under pressure in an autoclave. This isn't a do it yourself project. Soaking lumber in household ammonia could make you very sick and probably ruin your lumber, too.

   I'd agree with consulting some boat building forums. They deal with your situation regularly. This company has interested me but I haven't found anyone that has much information on the products and availability, at least in the US. The web site is for the manufacturer of the equipment.
   http://www.compwood.dk/

   Beat it to fit / Paint it to match

4. 
   WillGeorge | Jul 02, 2005 12:15am | #4

   This may be way off in left field BUT.. I built a boat long ago from plans.. 22 foot cabin (inboard) from plans.. I forget what wood but had to bend some pretty thick wood in a few places... NO STEAM...

   SO.. I had a block and tackle... Made a form... wrap wood in brown paper and rags..... Alot of Clamps and some scraps of wood for protectors from the clamp faces...

   WET it with water..  Pull tight as I could with block and tackle... Tighten clamps...

   Every day I re-did.. Wet.. Tighten up what I could... Took ALONG time but worked!

    

5. 
   KeithNewton | Jul 02, 2005 07:53pm | #5

   Bruce, Seems like I have already given advice to this without being sure it was a coaming, but I think you are making it harder than it really is. I have two teak boards out in the shop that are 8' long. I just took the bathroom scales out and pushed the middle down on top of it with the ends on 2" block. The 5" wide one took 80# and the 6" took 60#. That is not a lot for screws to hold. If you planed it down to 5/8" you may cut that number in half.

   If we use the higher number of the two, your 10" board may need 160# of pressure to get it sprung into place. While this may seem like a lot, I'm not sure that you need to steam or laminate it.

   Why don't you try this first. Find a thicker / stiffer board, something like a 2 X 12, and clamp the ends down with a 6" block under the middle for a day or two. This may give it a little short term memory that will make it easier to spring while you get the screws in. You can also use a little dollop of 3M 5200 behind it when you install, but I would not do a solid bond for this. You would never be able to get it off if it ever needs to be replaced again.

1. 
   BruceEbling | Jul 03, 2005 05:54am | #6

   Thanks Keith and all that send in suggestions. I think Keith is pretty close to the solution. I will try to spring the board for a couple of weeks before I install. Then I will check into through bolting rather than just screws into the fiberglass. Also after carefully looking at the original board that I took off, it has a plug on the bottom edge of the board just inside of the "notch" that is cut in each end. I drilled out the plug and there appears to be nothing inside. Could this be some type of measure to prevent the board from splittting when bent? Again I am pretty new to this stuff and I really appreciate you "pros" giving me the benefit of your wisdom
   Bruce Ebling

1. 
   KeithNewton | Jul 03, 2005 06:58am | #7

   Something else may have been mounted there in the past, and the plug is just filling the hole to prevent a leak. Just a guess.Yes, if you can get to the back side to put nuts and fender- washers behind the glass would be better.