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PostPosted: Fri Jul 17, 2020 7:17 pm 
Site Rank - Deck Hand

Joined: Mon Jun 22, 2020 7:51 am
Posts: 21
Location: Madison, WI
I saw an "old" (2015) forum post by "Russ" about how to build a DIY alternative to the Hobie Baby Bob he called the "Tightwad Bob". It looked like a good, inexpensive idea, though his linked pictures had disappeared over the years (just like they will here since this board doesn't appear to allow picture uploads). I couldn't quite understand his build instructions, so I bought a couple 7X15 Lobster Buoys and came up with my own plan to build the "new" Lobster Bob. As with Russ, I mostly used stuff that was sitting around my basement...

First...collected the parts...the 7X15 buoy, a 1" diameter aluminum tube, some chunks of aluminum plate from an old snow rake (cut 3" wide), a 1/4" aluminum round rod cut into a couple pieces and to be threaded at the ends, four 1/4" nylon nuts and 5/8" OD washers (drilled to 1/4"ID) and a 5/16 stainless bolt with nyloc nut and a couple zinc plated washers.

A few simple tools...a 6" saber saw blade to cut deep slots in the buoy, a fine cut blade to cut aluminum plate, tube and rod, a 1/4" X 12" bit to drill through the buoy and all the stuff inside, a 1/4" thread die for the aluminum rod, and a nice, long-blade carpet knife to start cutting slots in the buoy. I also used a 5/16" drill at some point...

I cut a 9" piece of the 1" tube and slid it into the buoy center hole...a pretty nice, tight fit...about 2" from this end.

Cutting deep slots was a hassle...starting with the carpet knife, then using the saber saw to get close to 6" deep. By the center hole (at ~3.5"), the slots should be ~1" apart. I started them at ~3/4" apart to match the width at the top of my single sheave mast. It turns out going with straight slots starting at 1" apart would have worked better since the width of the head at the mount hole is actually closer to 1".

With my newly purchased 12" bit, I drilled 2 holes through one side of the buoy, then through the installed close plate (not shown in this picture), the tube (can't see it, but it's there), the far plate (also not shown), and out the other end of the buoy. You need to be careful everything stays aligned after this step. I also decided to countersink the holes so the nuts end up inside the buoy.

And here's what it looks like assembled. Things can't really move since the structure of the tube, rods and plates makes for a rigid structure supported inside the buoy. I think this is pretty strong and unlikely to loosen up easily. Note that all the internal parts are aluminum on aluminum or nylon or foam. No real chance for corrosion except on the stainless bolt that holds everything to the mast...more on that coming up...

Looking through the tube, you can see the rods that provide the rigidity and resistance to internal rotation.

And I decided to fill the countersink holes with some Gorilla foaming glue to lock in the nylon nuts and allow the outer surface to be smoothed. Very aerodynamic (I guess)...

Here it is mounted on my single-sheave mast. The single-bolt mounting ended up pretty tight and not really subject to rotation. For the Comptip mast, or to emulate the 4 hole mounting of the Baby Bob, different holes would be needed and maybe some threading of holes in the head. I used zinc-plate washers under the stainless bolt with Noalox between washer and aluminum plat. Possibility for corrosion here, but hopefully it can be controlled or be subject to easy parts replacement over the years.

Up there at the top...

The Lobster Bob weighs about 2.1lb compared to the Baby Bob at 2.65lb. The Lobster Bob is a little weak at ~18lb for displacement compared to 32lb for the Baby Bob. But at ~$150 for the Baby and maybe ~$25 for the Lobster, the DIY approach may have some appeal. Of course, some assembly required. And, for me, lots of fiddling time. So maybe the Baby Bob would have been a reasonable option after all...


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