Boatbuilding Blog

April 25, 2011

Polishing the Dinghy

Filed under: Dinghy — tomlarkin @ 11:49 am

My dinghy was pretty inexpensive, but it was really rough. Thick glass seams on the chines and big blobs of resin were all over the outside. The bright wood finish also clashed with my color scheme. So I spent the past couple of weekends making it (somewhat) beautiful. First I ground down the worst of the high points and then re-sealed the surface with epoxy. Then I troweled on lots of fairing filler, sanded it off, and did it again. One more epoxy seal, then a couple coats of primer, then three coats of the same two-part polyurethane paint I used on the Coot. I added some rub strips on the bottom to protect my new paint and some ‘Gunnel-Guard’ padding all around the gunwales so the dinghy won’t ding up the hull. I hauled it down to the boat today. I think it looks really nice, and they look like they belong together now.

Lots and lots of filler!
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Primer:
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Installing the rub strips. The skeg has a stainless steel strip because it gets a lot of wear:
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This shows the gunnel-guard installed:
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At home on the stern:
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I wrote this entry on the iPad using the WordPress app, so the formatting is a little weird. Not as difficult to do as I expected, though.

March 28, 2011

Making the Dinghy Hinge

Filed under: Dinghy — tomlarkin @ 9:40 am

Years ago when I was working as a welder I made some Hossfeld steel bender knockoffs to sell for extra cash. I saved one and got to use it to bend the pivot bar that attaches to the dinghy.  I picked up some 1/2 inch stainless rod at Metal Shorts, put a roll of stainless wire in the MIG welder, and hooked up the Helium/Argon/CO2 gas mix. The bases are backing plates for Ronstan blocks. Using the mockup as a model, bending and welding only took a couple of hours.  You can see the piece on the boat in the top picture of the previous entry.

The Hossfeld knock-off mounted to my steel fabrication table:
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Clamped and ready to weld:
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Fitting it to the dinghy:
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February 10, 2011

Dinghy Tryout

Filed under: Dinghy — tomlarkin @ 9:31 am

Sunny and pleasant today so I took a vacation day to play with the dinghy. Everything worked surprisingly well! It was a bit heavy to start lifting, but not bad. I think I’ll need the block & tackle if I use a bigger, heavier boat. I stowed and launched it 5 times over a couple of hours. The dinghy is small, but rowed pretty well. I pulled it up in a 5 know breeze, with no problem. I think the pilothouse acts as a wind break while at anchor. I can cross under it pretty easily, even without blocking the bow up.

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I went for a nice row while anchored at Saint Edward Park.2011-02-09_14-47-19_207

February 9, 2011

Dinghy Mount Mockup

Filed under: Dinghy — tomlarkin @ 2:46 pm

I bought plans for a 9 1/2 foot Nutshell Pram to use as a dinghy. I wrote about how I wanted to load it onto the boat a few weeks ago. Then I saw an 8 foot Bolger Nymph pram on sale on Craigslist for a reasonable price. I went to the Second Wave used marine store in Fremont to look at it, and bought it almost on impulse. I picked up some used Weaver Davits at the same time, and the shop owner threw them in for free.  The dinghy is pretty small, maybe too small to safely hold the two of us. We’ll see. In the mean time, I can use it to see if the plan will work. I still want to make the Nutshell if I think I can get it onto the Coot.

Original idea:

I mocked up the curved stern of the Coot from scrap plywood and screwed the davits to it, then welded up a hanging bar from some old rebar in the garage. I can lift the dinghy as per the plan, but it’s really heavy. Harder than I had hoped. I may need to set up the 3:1 lifting tackle I’d  considered earlier. I’ll also try moving the painter attachment point to the bottom inside of the front transom to improve the lifting angle.

Dinghy in floating position. The mocked-up stern of the Coot is to the left, at the stern of the dinghy:
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Lift the back of the dinghy by the hanging bar and latch into the Weaver clips:
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Detail:
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Standing on the stern (in this case the steel workbench), pull the bow line to lift the dinghy up, and flip it onto the stern of the boat. This is about as high as I could go in the shop before hitting the lights.  I’ll move the whole thing to the boat one of these days to try it out live:
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Detail:
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If nothing else, I now have a nice little boat I can throw in the back of the truck for day trips.

January 3, 2011

Dinghy Idea

Filed under: Dinghy — tomlarkin @ 4:54 am

I’ve got a little 8 foot inflatable dinghy that fits in the forepeak. Anyone who’s ever used an inflatable knows the downsides of them – slow to inflate and deflate, and slow to row anywhere. Really awkward to manhandle, especially on a small mothership.  Here’s a way to carry a better better dinghy on the Coot.

This idea is to hook the stern of the dinghy to the transom of the Coot, and lift and flip the dingy upside-down onto the stern of the Coot.

The drawings show a 9-foot hard dinghy -  a Sherpa or Nutshell Pram for instance. There’s enough space for a 10 foot boat, but weight and leverage might become more of an issue while lifting.  The dinghy shouldn’t interfere with the usability much. Under way, the main outdoor space on the Coot is in front of the pilothouse. This area has a great view, and is away from the smoke and noise of the motor. To get to the lazarettes or the motor without removing the dinghy, you could lift the stem 2 or 3 feet and prop it up with a stick.  It makes a nice place to get out of the rain when working on the motor.  The dinghy shouldn’t obstruct the view out the stern too much.

At anchor, the aft space becomes usable just by flipping the dinghy off the back and leaving it attached.  You could even motor a ways in that configuration if you wanted.  In the stored position, the stem piece could drop into a socket with either a lockable pin through the stem or a padlock hasp attachment. Locking the stem down would make the boat absolutely fixed as well as difficult to steal. 

Dinghy Storage

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Ideal Dinghy

  • Rigid instead of inflatable
  • Long enough to row well and carry a decent load.
  • Move well under oars
  • Optionally able to use sails

Ideal Dinghy Storage

  • Easy to launch and retrieve
  • Low windage and low center of gravity
  • Won’t block the view or mobility around the boat
  • Minimal hardware left on the boat when the dinghy is removed
  • Stored upside-down so it won’t collect water and leaves, and will stay dry

Launching and Retrieving

Launching is really fast:

  • Unlock the stem piece
  • Grab the bow line
  • Lift the boat from the stem until it’s standing vertically on it’s transom
  • Either drop the boat or lower it to the water with the bow line.
  • Cleat the bow line
  • Unlatch the spring latches and lift the dinghy up off the hanging loops and drop it in the water.

Retrieving is just like launching, except you need to bring the stern of the dinghy around to the Coot transom. This might be difficult if it’s windy or rough. Stand on the stern platform to get the needed leverage to start lifting the boat, then walk it forward to set the stem down on the cabin top.

Mounting Hardware

It looks like Weaver Industries has the attachment hardware already made that would work for this application.

These are the parts that mounts to the Coot transom. They’re pretty unobtrusive.

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These parts mount to a riser on the transom of the dinghy. They would need to be modified to allow for swiveling 180+degrees instead of just 90 degrees.

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Mounting detail.

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Right-Side Up Version

You really need to lift it up a lot to get started, and then you need rollers and chocks to store it. It adds a lot more windage and will collect crud.

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Lifting With Block & Tackle

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