Boatbuilding Blog

March 28, 2013

Adding a Dolphin-Whacker

Filed under: Hardware — tomlarkin @ 1:11 pm

As part of getting ready for my Alaska trip I added a heavy bronze flat bar to the stem and first couple of feet of the bow. This is so I can run into logs or debris or even rocks without harming the boat. I bought a chunk of aluminum bronze from Online Metals, 1 1/2 “ x 5/8” x 8 feet long.

(Anyone know what this type of thing is actually called?)

I cut off an 18 inch chunk to practice with. Using the Hossfeld with a 6 foot cheater bar I succeeded in bending the part this much before giving up. It was just too hard. I had to bolt the table down to the floor and run stringers to the wall-mounted work bench because I was dragging the 400 pound steel welding table all over the shop.
Sample Piece

Another view. At this point I mounted a small Mat-Gas torch, pointing at the bend,  and tried again when the bend got hot. The bar just broke at the heated spot. Then I got out the real piece and asked Barry to come over and help. With me leaning on the bender and Barry pulling on the stock, we got it to bend to the correct angle to run under the bow. I had made a plywood template of the bow earlier, and we used that to get the correct angle.
WP_20130216_005

Then I drilled and countersunk mounting holes, sanded off the machining marks, and rounded the top end freehand with a grinder.The lowest mounting hole is about 8 inches above waterline to avoid holes underwater.
WP_20130216_006

I mounted the thing while the boat was out of the water for a tune-up and bottom paint. The mounting holes were injected with neat epoxy to seal them. The little piece of tape is to keep it from running out. I did this a few times until the epoxy stopped being absorbed. I masked the whole area because Sikaflex wants to get everywhere!
Injecting Epoxy

The unit was bedded in black Sikaflex. I used 8 screws,  #14 x 3 1/2” bronze.
WP_20130218_004

Here she is going back in. The bronze should tarnish dark like the rest soon enough. See how the bronze wraps under the bow a couple of feet.
WP_20130219_004

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2 Comments »

  1. That machine you are using there is a manual tubing bender.It is set up to bend square or rectangular tubing.Harbor Freight sells them along with a lot of other tool retailers.

    Comment by ben2go — March 29, 2013 @ 12:08 am

    • Hi Ben. Yes, kind of. I made this one, copying the model #2 bender we had in the shop where I worked at the time. With a long enough lever arm, you can put really huge forces on the work. I just ran out of space in my garage and couldn’t make the arm any longer.

      Comment by tomlarkin — March 29, 2013 @ 12:56 pm


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